Aligned growth of ZnO nanowires on diamond by nanoparticle-assisted pulsed laser depositionWednesday (24.06.2020) 11:56 - 11:59 Room 1
ZnO nanocrystals have been paid much attention owing to their unique optical and electrical properties, and ZnO nanocrystal-based optoelectronic devices have been reported. We have developed a catalyst-free growth method for aligned ZnO nanocrystals, named nanoparticle-assisted pulsed laser deposition (NAPLD) , and demonstrated Fabry–Pérot lasing from a single nanowire and high-sensitivity photosensor. However, the application of ZnO to homojunction diodes has been limited due to the difficulties of high quality p-type ZnO fabrication. As an alternative approach to utilize ZnO for optoelectronic applications, a ZnO/p-type material heterojunction structure has been suggested, and we have demonstrated ZnO nanowire/p-GaN film ultraviolet (UV) LED. Recently, diamond is attracting attention in combination with ZnO for photodetectors operated in the UV region because of its 5.47 eV band gap, highest thermal conductivity, high radiation resistance and good temperature stability. In this study, we synthesized ZnO nanowires on a diamond single crystal substrate by NAPLD, and investigated the structural and optical characteristics of the ZnO nanowires.
In the experiment, a sintered source target of ZnO was used. A diamond single crystal (100) substrate was put on a SiC heater in a vacuum chamber and the ZnO target was ablated with the third harmonics of a Q-switched Nd:YAG laser at 355 nm. Then, ZnO nanowires were grown on the diamond at background argon gas of 27 kPa and a laser fluence of 1 J/cm2 with a substrate temperature of 750 ºC for 20 minutes. Figure 1 shows the scanning electron microscope (SEM) images of the ZnO nanowires. The diameter of the aligned nanowires was about 100 nm. And they have wurtzite crystalline structure from X-ray diffraction measurement. A photoluminescence measurement under He-Cd laser (325 nm) excitation showed an UV emission centered at around 379 nm, which is the contribution of the near band edge emission of the wide band-gap ZnO, and weak broad visible emission attributed to the deep-level defects inside ZnO lattices. The results indicate a low concentration of deep-level defects inside ZnO lattices. Now, we are investigating dependence of orientation of the diamond substrate on the growth of the ZnO nanowires.
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