From the viewpoint of applications, a high-temperature process might damage or deteriorate optoelectronic devices. A low-temperature VS process would be more suitable for the integration of 1D ZnO-based devices. Besides, the important characteristic of the field emission of ZnO NWs is rarely investigated, which could be a candidate for field electron emitters due to their high aspect ratios, negative electron affinity, and mechanical and chemical stability. In this paper, we report a simple synthesis of ZnO NWs on a
silicon substrate using the VS process at a relatively low growth temperature (550°C). Methods ZnO NWs were synthesized in a horizontal tube furnace system equipped with a 90-cm-long quartz tube, three-zone heating system, gas inlet, and pump out. A 1 × 1 cm-sized, n-type Si(100) has been used as the deposited substrate. Before being loaded, the silicon substrate was etched LY3009104 using hydrofluoric
acid and cleaned ultrasonically with ethanol and deionized water. After finishing substrate pretreatment, the silicon substrates were selleck compound coated with 8-nm-thick Au films as buffer layer by a DC sputter. An alumina boat loaded with zinc powder (100 mesh, 99.99%) was placed at the center of the quartz tube, and the silicon substrates were placed a few centimeters downstream from the source. After loading, the quartz tube was heated up to 550°C under a constant high-purity Ar gas (150 sccm, 99.99%). The temperature was held at the peak temperature for 60, 90, 120 min, respectively. After evaporation, the system was SCH727965 concentration naturally cooled down to room temperature under flowing argon gas. The structure of as-grown samples was analyzed by X-ray diffraction (XRD; D5005, Siemens AG, Munich, Germany) using CuKα1 radiation. The morphology and microstructure were investigated by scanning electron microscopy (SEM; S-4300, Hitachi, Tokyo, Japan). Photoluminescence (PL) measurement was performed at room temperature
Sitaxentan using λ = 325 nm of excitation of a He-Cd laser source (IK3401R-F, Kimmon Koha Co., Ltd., Tokyo, Japan). Field emission was measured at room temperature in a vacuum ambient of 3.5 × 105 Torr. The distance between the anode and the tip of the ZnO NWs was 18 μm, and the emission current was monitored with a Keithley 237 electrometer (Cleveland, OH, USA) and recorded at 1.0-s intervals by applying a sweep step of 10 V. Results and discussion XRD was used to acquire the crystallographic property of the ZnO NWs. Shown in Figure 1 are the XRD patterns of NWs grown at 550°C for 60, 90, and 120 min, respectively. Obviously, only the diffraction peak of ZnO(002) appears in the XRD profiles without the existence of secondary phases and clusters. This indicates that the ZnO NWs are preferentially oriented in the c-axis direction. While increasing the growth duration from 60 to 120 min, the intensity of ZnO(002) diffraction plane increased as well.