One-dimensional nanoscale semiconductor structures

such as nanowires

nanobelts

and nanorods

have attracted considerable attention due to their interesting fundamental properties and potential applications in nano-scale opto-electronic devices.ZnS

an important semiconductor compound

has wide bandgap energy of 3.7 eV at 300 K.It has been used as a host crystal material in photoluminescence(PL)

electroluminescence

mechanoluminescence

acousticluminescence

and thermoluminescence.ZnS also has wide applications in the fields of displays

sensors

lasers

and photocatalysis.The ZnSin nanoscale has been reported to have some characteristics different from the bulk crystal

which may extend its application range.Recently

various ZnS nanostructures had been synthesized

including

nanowires

nanosheets

nanobelts

nanorods

nanoribbons

and nanotubes etc.As a rule

ZnS nanostructures were grown using thermal evaporation method with Au catalyst following vapor-liquid-solid(VLS) growth mechanism usually.In VLS growth process

catalysts play an essential role by forming liquid alloy droplet to provide nucleation sites for nanostructure growth.However

even low impurity concentration will affect the physical properties of semiconductors and the unintentionally doped impurities are detrimental for the device fabrication.Acatalyst-free method to grow vertical aligned ZnSnanorods array was reported.The ZnSnanorods were grown on

c

-plane Al

2

O

3

substrate by plasma-assisted metalorganic chemical vapor deposition(p-MOCVD) without employing of any metal catalyst.The images of field-emission scanning electron microscope(SEM) and transmission electron microscope(TEM) show that the obtained ZnSnanorods have uniform diameter of 60 nm with the length about 400 nm.Selected-area electron diffraction(SAED) pattern and X-ray diffraction(XRD) pattern measurements indicate that the ZnS nanorod is single crystals with hexagonal structure.In photoluminescence(PL) spectrum of the nanorods

a strong near band-edge emission located at 335.92 nm was observed under the excitation of 325 nm

indicating that the nanorods are of high optical quality.