Investigation On The Synthesis, Optical And Field Emission Properties Of Semiconductor ZnO

ZnO is an important wide band semiconductor. In this paper, ZnO micro/nanostructures with various morphologies have been synthesized by different methods, including thermal evaporation and hydrothermal. The photoluminescence and field emission properties of ZnO products are investigated. This thesis contains the following works and innovations:1. The ZnO nano structures with different aspects such as nanorod and nanoprick have been synthesized using thermal evaporation vapor phase transport by changing reaction time, temperature, airflow and pressure. The growth mechanisms have been analyzed, and the field emission properties have also been researched. The electron field emission properties show that the ZnO nanostructures which have sharp tips have better emission characteristic.2. A new aqueous chemical growth method for generation of ZnO nanorod chains, transformed from ZnO micro dumbbell, has been developed. The novel structure and morphology of the as-synthesized ZnO micro dumbbell and ZnO nanorod chains are characterized using X-ray diffraction and scanning electron microscopies. Field-emission characterization shows that the nanorod chains have better field emission properties with the lowest turn-on field (defined as the field required to detect a current density of 1μA/cm²) of～2.7 V/μm, and the lowest threshold field (defined as the field where the current density reaches 1 mA/ cm²) of～4.8 V/um. The field enhancement factor (3 was estimated to be about 2194 for ZnO nanorod chains. The findings imply that ZnO nanorod chains may be suitable for cold-cathode electron source applications.3. Novel porous ZnO nanobelts were successfully synthesized by heating layered basic zinc acetate (LBZA) nanobelts in the air. The precursor of LBZA nanobelts consisted of a lamellar structure with two interlayer distances of 1.325 and 0.99nm. Using the IR spectrums of the LBZA nanobelts, thermal decomposition behavior of LBZA nanobelts have been investigated. PL show that a strong UV emission centered at～380 nm coming from ZnO heated at 700℃has the highest I_UV:I_VS ratio (I_UV:I_VS～28). Defect-related visible emission is nearly no detected. The narrow (15 nm) full width at half maximum PL peak is the indication of the uniformity of the ZnO nanobelts. The good performance for photoluminescence emission makes the porous ZnO nanobelts promising candidates for photonic and electronic device applications.