| AVS 57th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Tuesday Sessions |
| Session NS-TuP |
| Session: | Nanometer-Scale Science and Technology Poster Session |
| Presenter: | T. Hirate, Kanagawa University, Japan |
| Authors: | T. Hirate, Kanagawa University, Japan T. Kanesiro, Kanagawa University, Japan T. Satoh, Kanagawa University, Japan |
| Correspondent: | Click to Email |
ZnO is a promising material for ultraviolet (UV) and white light-emitting diode (LED) applications, because of its large exciton binding energy of 60 meV relative to the thermal energy of 25 meV, as well as its large band gap of 3.37 eV at room temperature. In the past several years, the fabrications and characterization of one-dimensional ZnO nanostructures have been extensively investigated for their applications, such as LEDs, gas sensors, field emission devices, nanolasers and photovoltaics. We have studied on application of vertically aligned ZnO nanorods grown by CVD to field emission devices. In this paper we report on surface-sulfurization of Al-doped ZnO nanorods and the effects on the field emission characteristics.
Al-doped ZnO nanorods are grown by low-pressure thermal CVD cooperated with 10Hz Nd-YAG pulsed laser ablation of Al2O3 target, which is developed by us. Precursors for CVD are Zn vapor and O2. Substrates are n+Si(111) wafers. ZnO nanorods are grown in two stages. In first stage of growth no laser ablation is used to grow aligned ZnO nanorods and in second growth stage laser ablation is used to grow Al-doped ZnO layer on ZnO nanorods grown in 1st stage. Concentration of Al in ZnO nanorods is controlled by laser power. Finally surface-sulfurization is performed in H2S atmosphere. It is revealed that the conditions of sulfurization have very complex effects on field emission characteristics. An example of the conditions are 39.6 Pa of H2S partial pressure, 550 C and 5 min. Field emission characteristics are measured in vacuum of 10-4 Pa using 12.7mm diameter metal ball as anode electrode with separation of 160 micron meter.
When laser power is high (2.0W), the low initial electric field of 4 V/micron meter for emission is obtained. In this case, however, ZnO nanorods with sharp tips are grown due to high laser power, thus the reason of improvement of field emission characteristics is not clear at present. We are studying on this point. We estimate that the surface-sulfurization of ZnO nanorods are effective to improve the field emission characteristics because the electronic affinity of ZnS is lower than ZnO.