最新刊期
卷 29 ， 期 3 ， 2008
- 摘要：Patterned ZnO film seed layer was fabricated on the Si substrates by optical photolithography and pulsed laser deposition. The patterned and vertically aligned ZnO nanowires units with a minimum diameter of 30 μm were synthesized via vapor phase transport or hydrothermal growth method. X-ray diffraction analysis shows the nanowires are single crystal with c-axis [001] preferred orientation. The patterns of ZnO nanowires arrays are clear and the boarder is well ordered from the scanning electron microscopy (SEM) images. The photoluminescence (PL) spectra at room temperature of ZnO nanowires exhibit the strong emission at the wavelength 380 nm, the emissions in visible region were restrained, which indicates the good crystallity of ZnO nanowires with few defects. Through field electron emission test, a turn-on field and a threshold field of 2.3 and 4.2 V·μm-1 were achieved, which indicate that the patterned vertically aligned ZnO nanowires posses good field emission property.关键词：aligned ZnO nanowires;photoluminescence;field electron emission111|67|5更新时间：2020-08-12
- 摘要：A polymer light-emitting electrochemical cell(LEC)offers an alternative approach to achieving electroluminescence (EL) from conjugated polymers. Different from a polymer light-emitting diode(PLED),the emitting layer of LEC contains ionic conductor such as poly(ethylene oxide) (PEO) mixed with lithium salt. In these solid-state LECs, the conjugated polymers are p-doped on the anode side and n-doped on the cathode side and a light-emitting p-n junction is formed between the p-doped and n-doped regions. The LEC was shown to operate in both forward and reverse bias, effectively independent of the electrode workfunction. Compared with PLED, LEC has the advantages of low turn on voltage and high quantum efficiency of its electroluminescence. The luminescence of LEC based on emitting material poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene](MEH-PPV) doped with red dye 4-dicyanomethylene-2-(tert-buty1)-6-methyl-4H-pyran(DCJTB) has been researched. The EL peak wavelength of LEC devices depends on the luminescent materials of LEC. Usually OLEDs changed emission wavelength by doped organic dye into host materials, but this method in LEC was not reported. Doping organic dye into the luminescent materials of LEC may change the emission wavelength of device and fabricate LECs with various emission wavelengths, even the white emitting LECs.Red dye DCJTB was doped into MEH-PPV then a LEC device with a sandwich structure of ITO/MEH-PPV+PEO+LiCF3SO3+DCJTB/Al is fabricated. EL peak wavelength of the LEC devices ranges from 570 nm to 650 nm continuously, depending on the doping concentration of DCJTB. In the photoluminescence(PL) spectra excited with the excitation wavelength of MEH-PPV, it is observed that the emission from MEH-PPV decrease and DCJTB increase with the rise of the doped DCJTB mass concentration. This indicates that energy transfer occur from MEH-PPV to DCJTB. The redshift of DCJTB’s emission caused by increasing its concentration is another factor for the phenomena.关键词：polymer light emitting electrochemical cell;MEH-PPV;red dye DCJTB;doping;energy transfer103|418|1更新时间：2020-08-12
- 摘要：We compared the characteristics of OLEDs with different ITO anode resistances for the device structures: ITO/TPD/Alq3/LiF/Al to investigate the effects of ITO anode resistance on OLEDs performance. The devices with lager ITO anode resistances exhibit lower current density and luminance at certain driving voltage, which may mainly be due to the presence of series resistance of the ITO anodes leading to a reduced effective driving voltage for charge injection.We found that the efficiencies of the devices are independent on ITO anode resistances.关键词：OELDs;ITO;resistance115|99|3更新时间：2020-08-12
- 摘要：We fabricated the CuPc and C60 heterojunction organic photovoltaic devices by vacuum deposition and investigated the effects of CuPc deposition rate on photovoltaic device performance. We found that the photovoltaic devices with high CuPc deposition rate exhibited larger short circuit current and higher power conversion efficiencies. X-ray diffraction and atomic force microscopy studies show that the CuPc thin films with high deposition rates are smooth and amorphous, which may correlated with improvements of the charge transport and exciton diffusion for obtaining higher performance of organic photovoltaic devices.关键词：organic photovoltaic devices;thin films;deposition rate103|72|0更新时间：2020-08-12
- 摘要：With a wide bandgap of 3.370 eV and a large exciton binding energy of 60 meV at room temperature, ZnO has attracted considerable attention as a promising material for optoelectronic devices, especially in short-wavelength light emitting diodes (LEDs) and laser diodes. However, the lack of high-quality p-type ZnO has hampered the development of ZnO homostructural LEDs. The reported p-type ZnO films always have very low Hall mobility at room temperature (1~10 cm2·V-1·s-1). For improving the quality of p-type ZnO, it is very important to understand the hole scattering mechanisms in these films.In this paper, nitrogen-doped p-type ZnO films were grown on sapphire substrate by plasma-assisted molecular beam epitaxy, using radical NO as oxygen source and nitrogen dopant. The electrical properties of p-type ZnO films were investigated by temperature-dependent Hall-effect (T-Hall) measurements. The activation energy of N acceptor was deduced to be 75 meV by fitting the T-Hall data. The hole scattering mechanisms were studied both experimentally and theoretically. The experimental Hall mobility was found to be considerably lower than the calculated mobility including ionized impurity scattering, acoustic-mode deformation potential scattering, piezoelectric potential scattering, and polar optical phonon scattering. However, taking the effect of inhomogeneity on the mobility into account, the calculated mobility was in excellent agreement with the experimental data. This indicates that besides ionized impurity and acoustic deformation potential scattering at low temperatures and the polar optical phonon scattering at high temperatures, the effects of the inhomogeneous microstructure in p-type ZnO films play a more important role in determining the hole mobility.关键词：ZnO;p-type doping;scattering mechanisms;P-MBE100|95|0更新时间：2020-08-12
- 摘要：As a versatile wide band gap semiconductor material, ZnO has a variety of applications including gas sensors, piezoelectric devices, field effect transistors, solar cells, and so on. Particularly, the application of ZnO in blue and ultraviolet light emitting diodes (LED) and laser diodes(LD) have attracted much attention in the past ten years, because it has the wide-bandgap of 3.37 eV at room temperature (RT) and the large exciton binding energy of 60 meV. Many growth techniques for single-crystalline ZnO films have been used, such as molecular beam epitaxy (MBE), metal-organic chemical vapour deposition(MOCVD), RF magnetron sputtering, and pulsed laser deposition (PLD). Among these techniques, MOCVD has many advantages for the semiconductors production and has been used to manufacture many semiconductor devices. MOCVD growth of ZnO requires appropriate zinc and oxygen precursor. For the group Ⅱ element, the mostly used zinc precursor is a metal-organic compounds like diethyl (DEZn) and dimethyl (DMZn). For the group Ⅵ precursor, a large number of oxygen-containing compounds was widely used: gases like O2, CO2,NO,N2O;water and several types of organic compounds like alcohols, aldehydes, ketons. During the growth of ZnO, kinds of carrier gas were used to introduce zinc and oxygen precursor into growth chamber. Because of the huge volume of the carrier gas and the likely reaction with zinc precursor or oxygen precursor, it has the obvious influence on the quality of ZnO. In this experiment, argon(Ar), nitrogen (N2)and hydrogen (H2) were used to compare their effect on the growth of ZnO;DMZn were used as the zinc precursor and N2O as oxygen precursor.ZnO films were grown on quartz substrate by LP-MOCVD. Crystalline quality, and Optical properties were studied with photoluminescence, X-ray diffraction (XRD) using Cu Kα (λ=0.154056 nm), Raman spectra. The growth rate of ZnO was measured with the step profiler. Compared to Ar, the optical properties were improved by using H2 as the carrier gas of N2O. The quantity of unintended doped carbon was decreased. Ionization strengthened the ultraviolet emission and weakened the visible emission of ZnO films. According to the measure of XRD, the ZnO films had (0002) preferred orientation.关键词：ZnO;metal-organic chemical vapor deposition;ionization;carrier gas87|51|0更新时间：2020-08-12
- 摘要：The influence of hydrogenation on the luminescence characteristics of ZnO was investigated by low temperature photoluminescence (PL). Hydrogen was incorporated into the ZnO crystals from a remote dc plasma. It is found that hydrogen incorporation influences on the relative luminescence intensities of bound exci-tons, in particular the intensity of I4 (3.363 eV) is enhanced and a emission peaked at 3.366 eV appears. Hydrogenated ZnO samples show a different temperature dependence of PL spectra compared with virgin ZnO samples.关键词：ZnO;hydrogenation;anneal;PL spectrum98|90|0更新时间：2020-08-12
- 摘要：ZnO films have been prepared by radio frequency magnetron sputtering on sapphire substrates. The effect of the annealing temperature on the structure and optical properties of the ZnO films are studied using XRD, SEM and photoluminescence. The results indicate that the ZnO thin films have hexagonal wurtzite single phase structure and a preferred orientation with the c axis perpendicular to the substrates. With increasing annealing temperature the intensities of the XRD (002) diffraction peaks increases, the grain size and intensity of the UV photoluminescence peaks increase while the FWHM of (002) peaks decreases, which demonstrates that the high quality of the ZnO films deposited by RF magnetron sputtering can be obtained by properly controlling annealing temperature.关键词：ZnO films;RF magnetron sputtering;annealing116|85|2更新时间：2020-08-12
- 摘要：Recently, there has been an increasing interest in ZnO due to its electrical, optical and piezoele-ctric properties making suitable for many applications such as light emitting diodes, photodetectors, surface acoustic waves device and so on. SAW filters with working frequency higher than 1 GHz will be widely applied in the intending wireless communication, whereas higher resonant frequencies (superior to 2.5 GHz) tend to push the limits of conventional photolithography. ZnO/diamond structure as SAW substrates offers an attractive means for relaxation of the lithographic criteria since ZnO has excellent piezoelectricity while diamond has the highest elastic and stiff coefficient and highest sound velocity. The use of ZnO based on diamond as SAW substrates offers an attractive means for relaxation of the lithographic criteria since diamond has the highest stiff coefficient and sound velocity. SAW devices have been reported based on ZnO/diamond/Si layered structures with a diamond layer of 10~100 μm deposited by chemical vapor deposition (CVD) technique. However the silicon substrate restricts the heat dissipation performance of the diamond films. In regard of actual applications, a ZnO/diamond layered structure without a silicon substrate can make full use of the outstanding thermal, elastic, and sound velocity characteristics of diamond while avoiding restriction of heat dispassion due to additional silicon substrates. High quality ZnO films are currently the foundation of device preparation and the variation of deposition technological parameters is an important factor to obtain ZnO films with high quality.In this paper, ZnO thin films have been prepared on the smooth nucleation surfaces of freestanding CVD thick diamond films by reactive radio-frequency magnetron sputtering. With the variation of O2/Ar, the growth and optical properties of the ZnO films are characterized experimentally by X-ray diffraction, room temperature photoluminescence spectra, and electron probe microanalysis and Hall measurements. The results indicate that the ZnO film deposited with a O2/Ar ratio of 1 is of c-preferred orientation and high resistivity and has the best optical property.关键词：SAW filter;diamond;ZnO film;sputtering115|101|0更新时间：2020-08-12
- 摘要：Recently, ZnO has attracted great interest for its wide band-gap (3.37 eV) and relatively large exciton binding energy (60 meV) at room temperature (RT). It has been regarded as one of the most promising candidates for the next generation of ultraviolet (UV) light emitting diodes (LEDs) and lasing devices (LDs) operating at high temperatures and in harsh environments. For the application of ZnO based optoelectronic devices, it is necessary to fabricate both n-type and p-type ZnO films. It is easy to obtain n-type ZnO because it is intrinsic electron-conduction. However, realization of stable and reproducible p-type ZnO has long been the bottle-neck of ZnO-based optoelectronic devices. So far, a variety of dopants, mainly the group-V elements such as N, P, As, and Sb, and group-I elements such as Li, Na, and K,has been used to produce p-type ZnO. Though great progress has been made in fabricating p-type ZnO and even fabricating ZnO based p-n junction light emitting devices, this challenge still represents a major problem since the light-emitting efficiency was generally very limited due to the low concentration and mobility of holes in the p-type layer. Group IA element may be useful only for producing semi-insulating ZnO instead of p-type material, because their small ionic radii make them very easy to form the interstitial site as donor impurities rather than substitute on Zn site as acceptor impurities. Group ⅴ elements were also faced with considerable difficulties for p-type ZnO doping because of problems such as its self-compensating effect, deep acceptor level, and low solubility of the acceptor dopants. In addition, the choice of dopant and growth technique remains controversial and the reliability of p-type ZnO is still under debate. Lately, argentum (Ag), as group IB elements, was proposed to be a good acceptor candidate for producing p-type ZnO under oxygen-rich growth conditions based on first-principles calculations. Furthermore, p-type ZnO thin film has been achieved experimentally by Ag doping using pulsed laser deposition (PLD) technology at quite a narrow temperature range of 200~250℃. In this paper, Ag doped ZnO films (ZnO:Ag) were deposited on quartz glass substrates by ultrasonic spray pyrolysis (USP) technology. Zn(CH3COO)2 and Ag(NO3)3 aqueous solution were used as the sources of Zn and Ag, respectively. The effect of Ag doping on structural, electrical and optical properties of ZnO films were studied using X-ray diffraction (XRD), scanning electron microscope(SEM), Hall effect measurements, photoluminescence spectra, and transmittance spectra measurements. All the measurements were performed at room temperature. The surface of the ZnO:Ag film exhibits a smooth surface and very dense structure, no visible pores and defects over the film were observed. It is found that electrical and optical properties of the obtained ZnO:Ag thin films change dramatically due to Ag doping. The Ag doped p-type ZnO films with hole carrier concentration of 2.01×1017cm-3 and Hall mobility of 0.24 cm2·V-1·s-1 at room temperature have been successfully obtained at 550℃ reaction temperature.关键词：ZnO:Ag films;ultrasonic spray pyrolysis;p-type doping;Hall effect122|89|6更新时间：2020-08-12
- 摘要：ZnO was deposited on glass under NH3 gas ambience using electronic beam evaporation. AFM measurements indicate that the roughness of N-doped ZnO is a little bit higher than undoped ZnO, and it increases as the pressure of NH3 rises. However, the ZnO surface remains smooth. XRD measurement shows that the (0002) diffraction peaks remain constant for the different N-doped samples. The width of diffraction peak of N doped ZnO is 0.427°, which is a slightly broader than 0.261°of undoped ZnO. The resistivity of N-doped ZnO increases 4 to 7 times in magnitudes, which indicates the realization of reducing electronic concentration in ZnO films.关键词：N-doped ZnO thin film;AFM;XRD;PL spectra;resistivity121|170|1更新时间：2020-08-12
- 摘要：Because of the high basicity of mineralizer solution used for growing ZnO crystal, a closed precious inner metal container is essential for preventing the incorporation of impurities from the inner surface of the autoclave and for the growth of high-quality ZnO single crystal. Many researchers used platinum inner contai-ner but Pt is quite costly. In this paper, we report our growth of single ZnO crystals by the hydrothermal method using a gold inner container and the characterization of the grown crystals.ZnO crystals have been grown by the hydrothermal method using a mixed solution of KOH,LiOH and H2O2 as the mineralizer. The growing rates for +c(0001) and -c(0001) direction are 0.17 and 0.09 mm/day, respectively. The impurity concentration was determined by inductively coupled plasma mass spectroscopy (ICP-MS). The crystal-linity of the grown ZnO crystal was characterized by X-ray rocking curve measurement using a Philips X’pert MRD. The absorptivity was tested by a Jasco V-570 UV/Vis/NIR spectrophotometer, and the photoluminescence(PL) exited by a He-Cd laser (λ=325nm) was measured at room temperature.The results show that the incorporation of K was under detective limit;Li originated from LiOH was observed in both +c and -c regions. In addition, Au that may be corroded by H2O2 and Si came from the nutrients were also observed by ICP-MS. Other impurity concentrations (such as Al, Fe, Cu, and Pb) of the -c region were much higher than those of the +c region, and the crystal color changes from light green for +c sector to dark brown for -c sector. The full-width at half-maximum (FWHM) of double axis X-ray rocking curve for the polished Zn face cut from +c sector is 45 arcsec. For the +c sector, the resistivity at room temperature is 80Ω·cm, the carrier concentration is about 104cm-3, and the mobility is about 100 cm2/V·s.The photoluminescence (PL) spectrum has only a strong UV emission at 376 nm (3.3 eV)from the band edge and the absorption spectrum of +c part of the crystals is very flat between 400 and 1600 nm at room temperature.106|128|3更新时间：2020-08-12
- 摘要：ZnO sub-micrometer rod arrays have been prepared on bent surface of Zn microspheres by thermal evaporating the mixture of ZnS and Zn powder to metal Zn slice. In a typical preparation process, 0.01 mol ZnS and 0.01 mol Zn powder were mixed in an aluminum boat and positioned at the center of a horizontal quarts tube furnace. A slice of metal Zn substrate in a small quartz boat was located in downstream region of the tube. The whole system was sealed and pumped to a pressure of 100 Pa. High-purity Ar was aerated into the tube at a flow rate of 100 standard cubic centimeters per minute. The pressure in the tube was kept at 0.04 MPa. The furnace temperature was heated up to 900℃ at a 20℃/min rate. The system was kept at 900℃ for 2h. After the furnace was cooled to room temperature naturally, white wool-like matter was found to deposit on the Zn substrate. Finally, the product was collected for further characterizations by field-emission scanning electron microscope (FE-SEM, Hitachi S-4800) and LEO 1550 SEM attached with an Oxford Inca Drycool EDS detector. The results show ZnO sub-micrometer rod arrays can self-organized grow on surfaces of formed Zn microspheres. These ZnO rods with hexagonal cross-section have an average diameter of 500 nm and length of 1 μm. Top of the ZnO rod is very flat. Energy dispersive X-ray spectrum of the ZnO rod array demonstrates that only Zn and O elements exist with a ratio of about 1:1. No S element has been found. ZnO crystal exhibits hexagonal wurtzite structure, which belongs to the space group C4V6. According to selection rule of phonon mode, Raman active modes for the wurtzite ZnO are: 1A1+2B2+1E1+2E2. A1 and E1 modes are polar and can split into the transverse optical (TO) and longitudinal optical (LO) phonon modes. E2 mode is non-polar optical phonon mode, which is composed of two modes with low and high frequency. The vibration peaks at 331, 381, 430 and 580 cm-1 can be clearly observed in Raman spectrum of the ZnO sub-micrometer rod array. The peaks at 381 and 580 cm-1 correspond to polar transverse A1 and longitudinal E1 optical phonon modes, respectively. The strong peak at 430 cm-1 can be assigned to the nonpolar optical phonon (E2) modes of the ZnO rod at high frequency, which is associated with oxygen deficiency. The peak at 331 cm-1 is attributed to the 2E2 mode. Photoluminescence spectra of the ZnO rod arrays show two peaks at the wavelength of 387 nm and 509 nm, respectively. The stronger peak at 387 nm with the full width at half maximum (FWHM) of 16 nm can be attributed to near band-edge emission. Another weaker peak at 509 nm probably is due to defect state luminescence. The sub-micrometer ZnO rod arrays have a potential application in ultraviolet laser devices.98|83|1更新时间：2020-08-12
- 摘要：Co-doped ZnO films were fabricated using a pulsed laser deposition method on c-sapphire substrates. The structural and magnetic properties of the Co-doped ZnO films have been studied in this paper. The XRD characterization results show that they are wurtzite structures with the c-axes of the films aligning with those of the substrates. However the films do not grow along with the same orientation on the whole area of the specimens based on the HRTEM results. It is hard to conclude that the films were formed to be single crystals. The results reveal the occupation of Co ions at Zn sites in the host lattice. The studies of the electronic structures of the thin films show that the addition of Co ions into the Zn sites in the host ZnO affects the electronic band structure of the material. Magnetic hysteresis loops (M-H) were observed at room temperature, suggesting that the magnetism could be realized by Co-doping into ZnO. However, the improvement is limited. The work is following our previous reports on ZnO based diluted magnetic semiconductors, in which Co-doped ZnO thin films were synthesized using a dual-beam pulsed laser deposition method, suggesting their intrinsic mechanisms involved are probably similar.关键词：Co-doped ZnO;diluted magnetic semiconductors;pulsed laser deposition;magnetic properties117|276|1更新时间：2020-08-12
- 摘要：Diluted magnetic semiconductors (DMS), in which some atoms of host semiconductors are ran-domly substituted by magnetic atoms, are regarded as key materials for spintronics because they have charge and spin degrees of freedom in a single substance. ZnO is a potential candidate for applications of spintronics devices since its possibility for room temperature ferromagnetism and its intrinsic excellent electrical properties. ZnO is also suitable for fabricating carrier controllable ferromagnetism because carrier-controlling techniques for ZnO have been well established. And among the methods used for deposition of thin films, PLD is effective and has the advantage that the ratios of the elemental components of the bulk and film are almost the same, even for chemically complex systems. In this paper, Zn0.95Co0.05O thin films were prepared by pulse laser deposition(PLD) on silicon(100) and quartz substrates. By optimizing the growth conditions, the Co-doped ZnO thin films obtained at temperature of 700℃ and oxygen pressure of 0.02 Pa showed magnetism even at room temperature. The X-ray diffraction patterns suggested that the obtained films showed c axis orientation preference, and Co related phases such as CO2O3 didn’t appear, simply indicating that Co ions had been successfully doped into ZnO crystal lattices. SEM images showed that the films have dense surfaces with small roughness. The obtained sample was measured to have a hole concentration of ~1018cm-3, a mobility of 18.7 cm2·V-1·s-1, and a resistivity of about 0.04 Ω·cm, maintaining semiconductivity.And the magnetization of the Co-doped ZnO film can be measured at 12 K, even at room temperature.关键词：ZnO;magnetism;Co doped;PLD109|98|5更新时间：2020-08-12
- 摘要：p-type ZnO thin films have been realized via co-doping of In and N by using dc reactive magnetron sputtering method. X-ray diffraction (XRD) measurement showed that all films possessed a good crystallinity with c-axis preferential orientation. The lowest reliable room-temperature resistivity was found to be 35.6 Ω·cm with carrier concentration of 1.57×1018cm-3 and Hall mobility of 0.111 cm2·V-1·s-1. X-ray photo-electron spectroscopy confirms that In had been incorporated into the ZnO films effectively and the presence of In enhanced the incorporation of N. The transmittance spectrum revealed that the transmittance of all films was about 90% in the visible region.关键词：p-type conduction;In-N co-doped;dc reactive magnetron sputtering;ZnO film126|88|1更新时间：2020-08-12
- 摘要：We present a method that ZnO films have been deposited by radio-frequency (RF) reactive sputtering on Si substrates. Then the films were annealed in air, N2 or O2 for 1 hour respectively, and the optic and electricity characteristics of them were studied using ellipsometry and DLTS. The result shows that the refractive index of ZnO films is decreased with the descent of oxygen. And it is invariable with annealing temperature under O2.We explained and gave the mechanism about the invariance of refractive index . There has a deep level center related with Zni defect measured by DLTS. The deep levels of E1 was eliminated when annealed under O2.When annealing under N2, the existence of Zni restrained VO that favor decreasing the refractive index of ZnO films. Under certain annealing temperature and atmosphere the optic and electric characteristics of ZnO film can be improved obviously.关键词：ZnO thin film;annealing;deep level;photoelectricity characteristic95|103|0更新时间：2020-08-12
- 摘要：By alloying MgO with ZnO, ZnMgO exhibits a wider bandgap than pure ZnO and has a similar lattice constant to that of ZnO. Therefore ZnMgO can be used as a potential barrier to enhance the quantum efficiency for ZnO/ZnMgO heterostructures, such as quantum wells, superlattices, laser diodes and so on. However, one major challenge is to achieve high quality and stable p-type ZnMgO. Recently, p-type ZnMgO have been investigated by doping with P, Sb, Li, and codoping of Al and N by pulse laser deposition, rf magnetron sputtering, ultrasonic spray pyrolysis or dc magnetron sputtering.In this letter, p-type ZnMgO thin films were realized by Ga-N codoping method via dc reactive magnetron sputtering. ZnMgO thin films were deposited on glass, n-Si wafer, wet oxidated n-Si substrate (SiO2/n-Si) and quartz respectively. N2O was used as the source of N and O. Hall-effect measurements reveal that the optimal reliable p-type conduction is achieved on the wet oxidated n-Si substrate with a hole concentration of 2.28×1017cm-3, and a resistivity of 27.7 Ω·cm. XPS results suggest the presence of Ga-N bonds and thus validate the codoping method. According to the XRD patterns, p-type ZnMgO thin films exhibit good crystallinity with (002) orientation. The full width at half maximum (FWHM) of (002) diffraction peak are 0.61°, 0.392° to 0.314°,respectively, for the films deposited on glass, n-Si wafer, wet oxidated n-Si substrates. It is reasonable to consider that the crystallinity is improved evidently when the films deposited on SiO2/n-Si substrate. The FE-SEM image of the film deposited on SiO2/n-Si substrate is obviously different from that on the other substrates.关键词：ZnMgO thin films;Ga-N codoping;magnetron sputtering;substrate98|93|0更新时间：2020-08-12
- 摘要：Zinc oxide (ZnO) is a strong candidate for replacing GaN semiconductors that are of great technological importance for the fabrication of optoelectronic devices, because of its unique electrical and optical properties, namely, its large bandgap of 3.37 eV, low power threshold for optical pumping at room temperature, and highly efficient UV emission resulting from a large exciton binding energy of 60 meV at room tempe-rature, and an easy wet etching process. For the realization of high performance ZnO-based optoelectronic devices, the achievement of high quality ohmic contacts is essential. So far, the metal schemes for ohmic contact to n-type zno mainly focus on Al base and Ti base, such as,Al, Al/Pt, Ti/Au, Ti/Al/Pt/Au, and nonalloyed In. Pt-Ga via rapid annealing process, low specific contact resistance scope from 10-410-8Ω·cm2 was obtained. For p-type ZnO, due to its difficulty in doping, contact to p-type ZnO has not been extensive studied.There’s only a few report on Ni/Au,Au,Au/Ni/Au and Ni/ITO contact to Sb doped,P doped and ZnMgO p-type ZnO. Replacing O site by N is considered as a effective route to realize p-type ZnO. In this paper, we studied rapid annealing effect on the electric character of the N-doped ZnO film and effect on Ni/Au contacts to the N-doped ZnO film.A conversion from rectifying to ohmic behavior is observed for Ni/Au contacts to N-doped ZnO film. The as-deposited Ni/Au contacts to the as grown ZnO film shows nonlinear rectifying behavior, linear ohmic behavior appeared after rapid annealing at temperature up to 350℃. A minimum specific contact resistance of 8×10-4Ω·cm2 was obtained after annealing at 650℃. Higher annealing temperatures degrade the ohmic contact behavior. Hall measurement suggests that the conductive type changed from p-type to n-type via rapid annealing process, which corresponds partly to the changed contact behavior. Analyses of the elements depth profile by Auger electron spectroscopy and glancing angle X-ray diffraction identified the reaction product in the interface of the metal and ZnO. Results suggest the addition of surface state and interface state can lower the barrier height and increase the tunnel path, which also contribute much to the improvement of Ni/Au ohmic contacts to N-doped ZnO.关键词：N-doped ZnO;Ni/Au;rapid thermal annealing;ohmic contact110|92|0更新时间：2020-08-12
- 摘要：Effects of Al doping on the morphology and structure of Al-doped ZnO(AZO) were discussed. Analysis of AZO was carried out by scanning electron microscopy, photoluminescence and double-crystal X-ray diffraction. The diffraction peak position of the (002) plane was shifted to a lower angle with increasing Al concentration. It was found that the UV emission peak of near band edge emission in PL has a blue-shift to a region of higher photon energy with increasing Al concentration. The AZO epilayer was used as surface texturing, uniform current spreading, high transparent and thick window layer for achieving a highly efficient LED. AZO was deposited on the GaN-based LEDs as the transparent conducting layer. Light transmission above ~85% in the wavelength ranging from 400 to 700 nm, and AZO resistivity and roughness of ~7.3×10-3 Ω·cm and ~28 nm were obtained, respectively. The OM image shows that the LED with an AZO layer can reach a uniform current spreading at a relatively low current intensity (~0.02 mA).关键词：Al-doping ZnO;texturing surface;current spreading layer;window layer123|145|0更新时间：2020-08-12
- 摘要：We developed a simple and easy method to prepare nanometer-sized ZnO spheres via solvothermal route at low temperature and concentration without template. The morphology of the as-prepared ZnO spheres recorded by FESEM revealed that these spheres were uniform in size. From the higher resolution FESEM images we could clearly observe that the ZnO nanospheres were actually composed of many even smaller ZnO nanospheres. We conducted the experiments at different reaction time and temperature, systematically investigated the effects of these reaction conditions on the structural and optical characteristics of these ZnO nanospheres. The formation mechanism of such ZnO nanospheres was also discussed.关键词：ZnO;nanosphere;solvothermal;optical property;structural property108|118|4更新时间：2020-08-12
- 摘要：In recent years, semiconductor nanostructures have attracted much attention due to their potential application in a wide range of advanced devices. ZnO nanostructure has become a promising candidate for applications in functional oxide-based, blue-ultraviolet light emitting, field-effect transistor and transparent conductivity, because of its large direct wide band gap of 3.37 eV and large exciton binding energy of 60 meV. Furthermore, ZnO nanostructure can be used for electromechanical coupled sensor, transducers and biomedical applications. Many researchers reported the synthesis of ZnO nanostructures by a vapor-liquid-solid (VLS) mechanism. This approach is the most widely used technique for synthesizing aligned ZnO nanostructures, in which the assistance of metal catalysts, such as Au, Co, Cu etc. are frequently chosen. Because these catalysts commonly are also unfavorable impurities in the product, so it is necessary to exploit some catalyst-free growth techniques of ZnO nanostructures. Most of the related works were focused on the silicon and sapphire substrates using VLS technique, however there was no report of catalyst-free fabricating ZnO nanostructure on InP using pulsed laser deposition (PLD) technique. In this paper, we employed InP wafers as the substrates, a undoped thin ZnO film with thickness of 20~30 nm was predeposited on InP substrate surface by PLD as the buffer layer. The predeposited ZnO film assembled uniform ZnO islands on the InP substrate surface. ZnO nanoneedle-type nanostructure were successfully synthesized on indium phosphide (InP) (100) substrates. It illuminates that the using of catalyst is not absolutely necessary in the growth of ZnO nanostructures. The morphologic, crystal structural and optical pro-perties were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectrum analytic approaches, respectively. SEM pattern showed that the ZnO nanoneedle was obtained in high yield and high-quality and had a preferential growth orientation that was perpendicular to the substrate surface and are well separated from each other. From the XRD scan results, a strong diffraction peak was observed at 34.5°, attributing to the ZnO (002) plane, indicating that the growth direction is well-oriented along c-axis and has highly crystalline quality. A typical PL spectrum, measured at room temperature, showed a strong free-excition emission at 379 nm with a full width at half maximum (FWHM) value of 13.5 nm, and a weak deep level (DL) emission at 484 nm, the intensity ratio of free-excition emission relative to DL emission was 11:1, indicating that the ZnO nanoneedles produced in this experiment are of high optical quality. The simple and efficient method to fabricate ZnO nanoneedle has the following advantages: low cost, potential for wafer-scale production, and guaranteeing high-purity of ZnO. Therefore, this method may benefit in the applications for nano-devices.关键词：ZnO nanoneedle;pulsed laser deposition;photoluminescence;X-ray diffraction105|91|1更新时间：2020-08-12
- 摘要：Rare earth doped semiconductor nanomaterials have attracted wide interest in recent years. Rare earth ions can improve the electrical and luminescent properties of the matri-materials. For rare earth doped materials, many references reported Er doped systems, but La and Ce doped materials was rarely reported, especially for nanomaterials. This kind study will help to develop new luminescent materials. In this paper, rare earth ions La and Ce doped ZnO nanocrystals were prepared by co-precipitation method. XRD results show that the diffraction peaks of the semiconductor nanocrystals widened and the intensity decreased with the increase of rare earth concentrations in the ZnO nanocrystals which means that the size of the ZnO nanocrystals decreased. The results show the doping of rare earth ions can hold back the growth of ZnO nanocrystals. The La and Ce doped samples have the same results. Strong and narrow blue photoluminescence at 443 nm was observed in 1% Ce doped ZnO nanocrystals excited at 380 nm. It was ascribed to oxide vacancy defect caused by CeO2 new phase. This blue luminescence is important to the preparation of short wave apparatus. The photoluminescence of La ions doped ZnO nanocrystals was a wide peak from 418 nm to 610 nm.关键词：coprecipitation method;ZnO nanocrystsl;rare earth doping;photoluminescence115|111|6更新时间：2020-08-12
- 摘要：By using low-pressure metal-organic chemical vapor phase deposition(LP-MOCVD) technology, ZnO nanorods were grown with ZnO particles as catalyst on Si(111) substrate’s surface. X-ray diffraction (XRD),Raman spectroscopy, scanning electron microscopy(SEM), photoluminescence(PL) were used to characterize the crystalline quality, crystal structure,surface properties and optical properties of the ZnO nanorod samples. The results show that ZnO nanorods have a preferential c-axis orientation. Oxygen partial pressure was found to have important influence on the growth of ZnO nanorods. When oxygen partial pressure is low, the growth of ZnO is based on VLS growth mechanism;when oxygen partial pressure is high, the growth of ZnO is based on VS growth mechanism;ZnO growth can be optimized by changing the flow rate of N2O.Currently the use of MOCVD and ZnO catalyst for the growth of nano-ZnO arrays are less reported. The paper has enriched ZnO nanomaterials synthesizing methods, and the growth control mechanism was discussed.关键词：ZnO nanorods;VLS/VS mechanism;LP-MOCVD109|106|1更新时间：2020-08-12
- 摘要：Sn-doped ZnO nanocrystals were synthesized by the hydrothermal method using ZnCl2 and NaOH as raw materials at 200℃ for 5 h. The dopant source of tin was SnCl4·4H2O and the atomic percentage of dopant in the solution were n(Sn):n(Zn) = 1% and 2% respectively. The phase composition, morphology, size as well as optical properties of the samples have been characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-Visible absorption and photoluminescence (PL) spectra. The effects of the Sn doping concentration and the pH value of the precursor solution on the surface morphology and optical properties of the samples have also been studied. The experimental results indicate that the obtained Sn-doped ZnO nanocrystals are of hexagonal wurtzite structure. The average grain size of the samples increases and the surface morphology goes from short rod-like to single cone-like and double cone-like with the increase of Sn concentration. In addition, the surface morphology of the samples can also be affected by the basicity of the precursor solution. Since it changes from long rod-like (for pH 7.0) to short rod-like (for pH 12.0). There was a UV absorption peak from the UV-visible absorption spectra which have a red-shift with the increase of Sn concentration. Three photoluminescence bands, including a strong purple emission at 433 nm, a left-shoulder near UV band emission around 401 nm as well as a weak blue emission at 466 nm were observed at room temperature. The intensities of the emission peaks increased with the increase of Sn concentration. Compared with that of undoped ZnO nanocrystal, only the intensities of emission peaks are changed, but the peak positions are almost not changed in the Sn doping concentration rang of our experiments.关键词：ZnO nanocrystal;hydrothermal synthesis;Sn-doping;optical properties111|71|1更新时间：2020-08-12
- 摘要：ZnO is wide bandgap semiconductor. Its nanoparticles with uniform size distribution have caused much attention because the nanoparticles are bases of other nanostructures. In this work, ZnO nanoparticles were grown from newly produced zinc ketoacidoximate (C8H16N2O8Zn) precursor and from the precursor in NaCl and in mixture of NaCl and Li2CO3 at different temperatures of 300~700℃ in muffle stove. The nano-particles were characterized by X-ray diffraction (XRD), scan electron microscope (SEM), absorption and photoluminescence spectroscopy. The growth mechanism and effects of NaCl plus Li2CO3 and the growth temperatures on nanostructure morphology and size distribution were discussed. The ZnO nanoparticles were formed at 320℃ from pure zinc ketoacidoximate precursor or from the precursor in NaCl and in the mixture of NaCl and Li2CO3. All the nanoparticles were spherical. The average diameters were 6, 6.5, 7.0 nm correspondingly. Size distribution of ZnO nanoparticles grown from the pure precursor is wider while nanoparticles grown in NaCl and in mixture of NaCl and Li2CO3 are almost uniform. When the growth temperature was decreased to 300℃, ZnO could not formed. When the growth temperature was increased to 450℃, the nanoparticles grew larger and the morphology was still spherical. With a further increase of the growth temperature, nanorods with larger diameter formed due to the melting of haloid and agglomerate of Zn precursors. The size and size distribution of the nanoparticles mainly depended on the growth temperatures. Absorption peaks of the nanoparticles grown at 320℃ was near 3.35 eV and the absorption peaks of nanoparticles synthesized in NaCl and in mixture of NaCl and Li2CO3 red-shifted due to quantum size effects. The nanoparticles grown at 320℃ had strong UV luminescence at room temperature. Gaussian fitting indicated that the luminance of nanoparticles are consistent of luminescence of transition from oxygen vacancies and Zn interstitials to the valance band, luminescence of shallow impurities recombination and luminescence of band-edge recombination.关键词：ZnO nanoparticles;size distribution;growth temperature;optical properties.133|96|1更新时间：2020-08-12
- 摘要：Much effort has been devoted to the development of cold cathodes in field emission flat panel display and vacuum microelectronic devices. Electron field emission from various nanostructure materials has drawn significant attention of the industrial and scientific communities over world wide. One of the cold cathodes is zinc oxide (ZnO). ZnO-based nanostructure materials have attracted great interest recently due to their potential applications such as ultraviolet nanowire nanolasers, gas sensors, solar cells and field emission (FE) devices. Zinc oxide is a Ⅱ-Ⅳ compound semiconductor with a direct wide bandgap (3.37 eV) and large exciton binding energy (60 meV). Several methods have been reported for the synthesis of one-dimensional (1D) ZnO nanostructures such as nanowires, nanorods, and nanobelts. Comparing to carbon-based materials, the ZnO nanostructure has a unique advantage. Using carbon-based materials, we have to encounter a strict requirement on vacuum. If not, it will be oxidized with the growth of vacuum and temperature. ZnO nanostructure would last longer under the same vacuum for carbon-based FE device. The tetrapod-like zinc oxide synthesized by Vapor-Solid method was applied to the field emission display as the cold cathode material. Our ZnO nanostructures were prepared by oxidizing Zn vapor in a horizontal tube furnace. The source material was Zn (99.9%) powder, which was loaded in a horizontal quartz tube placed in the constant temperature zone of the tube furnace. Ar at a flow rate of 300 sccm was used first to purge the reactor for 30 min. Then the furnace was heated to 850℃ at a heating rate of 25℃/min and kept at 850℃ for 30 min at a flow rate of 70 sccm Ar and 40 sccm O2. Finally, after cooling down the furnace naturally to room temperature under the protection of an Ar flow, the fluffy, white ZnO was collected from the quartz tube. We introduced SEM and XRD to show the morphology and structure of the tetrapod-like zinc oxide.The field emission characteristics are evaluated by the simplified Fowler-Nordheim (FN) equation J=A(β2V2/Φd2)exp(-BΦ3/2d/βV), where J is the current density, A and B are constants with values of A=1.56×10-10A·V-2·eV,B=6.8×103 V·eV-3/2·μm-1, respectively, β is a field enhancement factor which quantifies the field enhancement due to microstructure roughness, Φ is the work function of ZnO (5.3 eV), d is a distance between the anode and cathode and V is the applied voltage. The characteristic of the diode structure was researched and the anode display image was presented. The turn-on field was 3.6 V·μm-1 and the threshold field was 6.6 V/μm with the current density of 0.2 mA·cm-2. From the stable field emission and uniform display image, we can conclude that the tetrapod-like zinc oxide is an excellent cold cathode material for field emission and has a potential application in the vacuum nano-electronics.关键词：tetrapod-like zinc oxide;field emission;nano-material;flat panel display96|89|2更新时间：2020-08-12
- 摘要：In the early 1980’s, Tokuda studied the mean number of phonons for both the optical and the piezoelectric polarons within the scheme of variational approach based on the unitary transformation and the method of the Lagrange multiplier.Many investigators studied the properties of the mean number of phonons of polarons by using many methods. The properties of the mean number of phonons of the polaron in polar crystal, quantum well, quantum wire and symmetric quantum dot have been studied using the linear combination operator method by one of the present authors and co-worker. Recently, the mean number of phonon of the polaron in an asymmetric quantum dot has been calculated using linear combination operator method by the present author. However, using linear combination operator method, the properties of the mean number of phonons for the bound polaron in an asymmetric quantum dot has not been investigated so far. The purpose of this present paper is to explore the effect of the transverse and the longitudinal effective confinement length of quantum dot, the Coulomb bound potential and the electron-phonon coupling strength on the properties of strong-coupling bound polaron in an asymmetric quantum dot. We obtain the expressions for the vibration frequency and the mean number of phonons of the strong-coupling bound polaron in an asymmetric quantum dot as a function of the transverse and the longitudinal effective confinement length of quantum dot, the Coulomb bound potential and the electron-phonon coupling strength by using linear combination operator and the unitary transformation methods. Numerical calculations are performed and the results show that the vibration frequency and the mean number of phonons of the strong-coupling bound polaron in an asymmetries quantum dot will strongly increase with decreasing the transverse and longitudinal effective confinement length of quantum dot, and will increase with increasing the coulomb bound potential and the electron-phonon coupling strength.关键词：asymmetric quantum dot;bound polaron;mean number of phonon;linear combination operator108|62|1更新时间：2020-08-12
- 摘要：The nano-zinc oxides (ZnO) synthesized by thermal evaporation of zinc powder with silver powder at different temperature and zinc powder only were compared. Scanning electron microscopy (SEM) was applied to study the morphologies and X-ray diffraction (XRD) was exerted to characterize the crystal structure. The field emission cathode was fabricated with a simple screen printing method. We packed the cathode panel and the anode panel printed with phosphor power as a field emission display with diode structure for the contrastive field emission experiment. The results show that the higher synthesizing temperature of the sample, the better field emission;the sample synthesized by the evaporation source including zinc powder and silver powder shows better field emission than that for the single source only including zinc powder. It’s shown from the experimental results that nano-ZnO semiconductor material is a good candidate for a field emission cathode and has potential application in vacuum electronics.关键词：zinc oxide;field emission;flat display;nanomaterial107|92|0更新时间：2020-08-12
- 摘要：The electron energy distribution of n-type silicon tips (EED/n-Si) is simulated as a function of gate bias and compared with experimental results. The simulation is based on the theory of electron energy distribution of metals (EED/M) taking account of the penetration of electric field into semiconductor. The calculated results showed the electron energy of EED/n-Si will shift to low energy with penetration of electric field, higher the gate bias or the electric field on surface and more shift of the electron energy of (EED/n-Si) to low energy. The shift could be over 1.5 eV according to gate bias. The penetration of electric field into the n-Si is predominant in the shift of electron energy of EED/n-Si.关键词：field emission;electron energy distribution;silion tip;penetration of electric field101|66|0更新时间：2020-08-12
- 摘要：Vacuum micro-electronics devices based on field emission cathode have become the focus of people around the world because it has lots of advantages such as high-speed electron transmission, low power consumption, high current density, operating without heating and so on. Field emission array (FEA) is the most important part of the vacuum micro-electronics device. In order to improve the performance of the FEA devices, many new structures have been designed and the fabrication of FEA has been optimized constantly. Filmed-array is a novel approach that includes not only the advantages of the array but also the characters of the film materials. It is considered to be an effective method to improve the performance of the devices. Filmed-array is fabricated by coating additional thin films on the tip of prepared spindt arrays. If the film material chosen has low work function, high conductance and reliability, good emission can be gained. The choosing principle of the film materials includes work function, conductance, density and reliability. Being a good thermal emission material, lanthanum hexaboride(LaB6) has excellent characteristics and is propitious to the film. The fabrication of LaB6-coated silicon spindt field emission arrays is reported in this paper, in which standard semiconductor techniques including oxidation, photolithogragh, dry etching, oxidation sharpening on the n-type silicon were used. In our fabricated silicon spindt arrays, the height is about 1μm. Interval between each silicon spindt is 6 μm, and cutting-edge radius of curvature is about 50 nm, tip-angle is about 56 degrees, the density of arrays is about 106/cm2. Then, the LaB6 film is deposited on the silicon spindt by electron beam evaporation to reduce the work function and enhance the capability of resisting ion bombardment. Film thickness is about 50 nm, the radius of curvature is about 111 nm.The X-ray Diffraction (XRD) analysis results indicates LaB6 with well crystallization was gained by electron beam evaporation, In interplanar 〈100〉, films make preferred growth. I-V characteristics and stability of field emission of silicon array and LaB6 filmed-arrays have been studied. The results show that silicon array coated by LaB6 film has good and stable emission characteristics. The total field emission current from the LaB6 filmed-arrays reached to 125 μA, which is 125 times than pure silicon spindt arrays. The results indicated LaB6 filmed-arrays is the kind of ideal field emission arrays.关键词：lanthanum hexaboride;silicon spindt arrays;electron beam evaporation;field emission;filmed arrays105|69|0更新时间：2020-08-12
- 摘要：High aspect ratio, small diameter, inertness, and high heat conductivity make CNTs promising field emitters. With the advancement in the fabrication technology, the emission current density of field emission arrays is increasing steadily. At high current density, the measured F-N plots often show deviations from linearity. Apart from the intrinsic effects of the material of the field emission cathode, another reason explaining this phenomenon could be the effect of space charge. Moreover, the performance of CNT-emitters has been improved greatly recently: this means that the macroscopic current density can reach several amperes per square centimeter and the corresponding microscopic current density at the tip of CNTs is so high that space charge affects the field emission of CNT-emitters noticeably. This leads to a lower current density from the CNT-arrays as compared to the situation where space charge effects do not play a role. In this paper, we try to simulate the influence of the space charge effect in carbon nanotube field emitter.A fabrication of carbon nanotube bundle field emission arrays (FEAs) grown by microwave plasma chemical vapor deposition MWPCVD was reported in this paper. This prepared FEAs present good field emission performance. To simulate the field emission characteristics of these FEAs, a model was built based on the microstructure of our carbon nanotube bundle field emission arrays firstly. Then the influence of the space charge effect on the character of carbon nanotube field emitter was simulated using the Electron Beam Simulation (EBS) software, including the distribution of electric field on the surface of emitter, emission current density, I-V behavior and the expending angle of emitting electron beam.The simulation results show that the I-V characteristics of CNT emitters act in well accord with F-N equation when the current density at the tip of CNTs is low. However, when the current density at the tip of CNTs is more than 106A/cm2, the effective electric field intensity on carbon nanotube tip is impacted evidently by the space charges, which influence the characteristic of carbon nanotube field emission evidently. By comparing the electric field intensity of tip in free space with the field of tip in space that is influenced by space charges, we can find that the tip field, with the continuous increase of applied voltage, is linear with the applied voltage in free space. However, they are nonlinear in space influenced by space charges. When space charges appear, the field of tip is lower than that in free space. The reduction of tip field will lead to the reduction of emission current density on the tip. As a result the current density of carbon nanotube is limited by the space charges. Through the simulation, we also find that the space charge can lead the expending angle of emitting electron beam to be larger.关键词：space charge effect;carbon nanotubes;field emission;microwave plasma CVD104|189|3更新时间：2020-08-12
- 摘要：The preparation and characteristics of silicon nanoarrays is now an attractive areas of research. At present,most research focused on the optical and electrical properties and applications,and less field emission characteristics,as a mature technology of silicon planar support, silicon field emission cathode materials are easily compatible with the microelectronic integrated circuits, and so they have a broad application prospects.We present the fabrication of large-scale two dimensional periodic silicon nanoarrays using nanosphere lithography,and the field emission characteristics have been studied. The fabrication process includes following steps: first the crystalline silicon substrate was coated with a monolayer of self polystyrene (PS) spheres of 220 nm in diameter, then the sample was etched by reactive ion etching to produce silicon nanoarrays. AFM images of the nanoarrays show that the tips stand 60～70 nm high and the area density can achieve 6×109/cm2. All field emission measurements were performed at a vacuum of 1.0×10-4 Pa or better. Expected to improve the field emission characteristics, about 60 nm thickness of a amorphous carbon film was deposited on top of the silicon nanoarrays by plasma-enhanced chemical vapour deposition. Field emission results show that compared to silicon nanoarrays, silicon nanoarrays coated with a thin a-C film effectively lower the threshold fields, approximately 8.1 V/μm, while field enhancement factor increased. When the electric field intensity reached 20 V/μm, the current density can reach about 1.4 mA/cm2. The improvement of field emission originates from the anisotropic structure of the films,when conductive sp2 clusters embedded in an insulating sp3 matrix,the electric field has been enhanced.关键词：silicon nanoarrays;field emission;amorphous carbon113|64|0更新时间：2020-08-12
- 摘要：Recently, phosphorescent materials like iridium(III) complexes have been attracted a lot of interest for their potential application on fabricating organic light emitting diodes (OLEDs) and their high phosphorescence quantum efficiency which is due to mixing the singlet and the triplet excited states via spin-orbit coupling and enhancing the triplet-state subsequently. In our work, a series of new iridium complexes were synthesized based on the ligands of benzotriazole derivatives. Complexes Ir(TBT),Ir(EBT), Ir(CBT) were characterized by 1H NMR and ESI. In addition, steady photoluminescence studies reveal that Ir(TBT),Ir(CBT) and Ir(EBT) exhibit orange-red, orange and yellow fluorescent emissions in solid state at room temperature, respectively. According to the study, it is found that the emission maximum of these complexes can be tuned by modified ligands. Theoretical studies of electronic structures were carried out using density functional theory at the B3LYP/6-31G* level in order to gain a good understanding of the luminescent behaviors of these materials. The quantum chemistry calculation results are accordant with the experiment study. In addition, the thermal stability was also investigated by DSC and Tg is located about 133℃, which shows the material Ir(TBT) meets the thermal request for OLEDs materials. Based on the study, it shows that these complexes could be designed as OLEDs materials.Our work proves that the iridium complexes based on benzotriazole derivatives can be perfect candidates for fabricating OLEDs.107|99|0更新时间：2020-08-12
- 摘要：In polyphosphoric acid (PPA) solution, a novel acidic potassium permanganate-galangin chemiluminescence system was studied. By means of chemiluminescence spectra, UV-Vis absorption spectra, fluorescence spectra and micro-potentiometric titration method, it was discovered that some experimental evidences for confirming the emission species of the system. The results indicated that the CL intensity of system reached maximum when the molar ratio of potassium permanganate to galangin was 6:5 and the CL intensity of system was proportional to galangin concentration within certain concentration extent when existing excessive oxidant. In addition, the fact that there exists mirror symmetry between electronic absorption spectra of permanganate ion and chemiluminescence spectra of the redox system showed that main luminophor of the chemiluminescence system certainly came from the reductive products of permanganate ion. The chemiluminescence kinetic results also indicated that along with the chemiluminescence reaction, the emission species was hardly the single species but could be converted into other species by the some dismutation process. On the grounds of experimental results, a possible reaction mechanism was also proposed, and it was confirmed likewise that the main emission species of the chemiluminescence redox system was more probably contributed of the excited Mn(Ⅱ) and Mn(Ⅲ) species produced by the redox system. Furthermore, the production of excited Mn(Ⅱ) by the active radical which came from galangin’s oxidative production was the main approaches for chemiluminescence reaction. The CL intensity of excited Mn(Ⅱ) had to be of linear relationship to galangin concentration,thus can be applied to quantitative analysis;but the production of excited Mn(Ⅲ) by the dismutation process would disturb the chemiluminescence behavior between the CL signal response and galangin concentration and not to be beneficial to chemiluminescence analysis.关键词：chemiluminescence;galangin;potassium permanganate134|127|2更新时间：2020-08-12
- 摘要：The influence of ZnO nanoparticles on chlorophyll a (Chl-a) was studied by observing their absorption, fluorescence, and Fourier transform infrared spectra (FTIR). Chl-a molecules were absorbed onto the surface of the colloidal nanoparticles due to the electrostatic interactions between Chl-a molecules and particle surfaces which led to a redshift of the absorption peaks of Chl-a upon addition of ZnO nanoparticles to Chl-a benzene solution. The redshift of the fluorescence spectra and the quenching of the fluorescence emission of Chl-a suggested a charge-transfer between Chl-a and ZnO nanoparticles. The difference between the first exci-ted state of Chl-a and the bottom of the conduction band of ZnO may provide the necessary driving force for such a charge-transfer process. An isoemissive point was observed at 654 nm in the fluorescence spectra when excited by 355 nm. No isoemissive point was found when excited by 433 nm, because ZnO nanoparticles have no absorption at this wavelength. Based on the Stern-Volmer relation I0/I=1+K[Q], the quenching mechanism was attributed to static quenching. Besides, changes of Zn-O bond vibration peak in FTIR were also observed after the Chl-a molecules were absorbed onto ZnO nanoparticles. The above studies illustrated a strong interaction between Chl-a and ZnO nanoparticles, and indicated that ZnO nanoparticles may exert negative impact on the photosynthesis process, where Chl-a plays an important role.关键词：Chl-a;ZnO nanoparticle;fluorescence quenching;isoemissive point124|103|2更新时间：2020-08-12
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