Synthesis of ZnO Nanowires by Pulsed Laser Deposition in Furnace
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Synthesis of ZnO Nanowires by Pulsed Laser Deposition in Furnace Kyung Ah Jeon1, Hyo Jeong Son1, Jong Hoon Kim1, K. H. Yoo2, Sang Yeol Lee1 1
Department of Electrical and Electronic Engineering, Yonsei University,
134 Shinchondong, Seodaemunku, Seoul, 120-749, Korea 2
Department of Physics, Yonsei University, 134 Shinchondong, Seodaemunku, Seoul, 120-749, Korea ABSTRACT ZnO nanowires (NWs) were fabricated on Au coated sapphire (0001) substrates by using a pulsed laser deposition (PLD) system in vacuum furnace with a Q-switched Nd:YAG laser. ZnO NWs have various size and shape with a substrate position inside a furnace, and their morphologic construction is reproducible. Scanning electron microscopy (SEM) images indicate that the diameters of ZnO NWs ranged from 100 to 150 nm and the average length was greater than 3 µm. Room-temperature photoluminescence spectra of the NWs show the near band-edge emissions and the deep-level green light emissions. The formation mechanism of the NWs is discussed. INTRODUCTON One dimensional nanoscale structures have attracted a great deal of attention in recent years because of their great potential for novel physical studies as well as applications in constructing nanoscale electronic and optoelectronic devices. Several different methods have been used for producing NWs such as laser ablation [1], chemical vapor deposition [2,3] thermal evaporation [4,5] Controlled growth of the NWs in their morphology, orientation, for example, is the key to success both for characterization of physical properties and promising application of ZnO nanowires in nanoscale optoelectronic devices; however, it is extremely difficult to realize. In most of previous reports for growth of NWs by using PLD, deposition times are over 60 min. The target which is induced by laser beam during the deposition forms many cone-like structures on the surface. This cone-like structures change plume direction and distribution of the particle size, which cause the decrease of deposition rate [6] and aggravation of film quality [7]. Here we report the use of the vapor-phase transport process to grow ZnO nanowires via the vapor liquid solid (VLS) mechanism [8]. The Zn vapor is generated using laser ablation of rotating ZnO target to avoid the formation of cone-like structures. Photoluminescence (PL) characterization of the nanowires shows that these nanowires exhibit strong UV emission and size-dependent green
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light emission.
EXPERIMENTAL ZnO NWs were synthesized on Au coated Al2O3 (0001) substrates by using pulsed laser ablation in alumina tube placed inside a furnace. Target was put on the rotational holder inside the center region of the tube and the substrates were placed upstream from center of the tube as shown in Fig. 1. The sample A and B were located at 5 cm and 1 cm from target, respectively. After the evacuation of vacuum chamber to the pressure of 1ⅹ10-3 torr, argon gas was injected into the chamber under a flow rate of 50 sccm by a mass flow controller and maintained at a c
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