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.