Growth and Optical Properties of GaP, GaP@GaN and GaN@GaP Core-shell Nanowires
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Growth and Optical Properties of GaP, GaP@GaN and GaN@GaP Core-shell Nanowires Hung-Min Lin,1 Jian Yang,1 Yong-Lin Chen,2 Yau-Chung Liu,1 Kai-Min Yin,3 Ji-Jung Kai,3 FuRong Chen,3 Li-Chyong Chen,2 Yang-Fang Chen2 and Chia-Chun Chen1,4,* 1 Department of Chemistry, National Taiwan Normal University. 2 Institute of Condensed Matter, National Taiwan University. 3 Department of Engineering and System Science, National Tsinghua University 4 Institute of Atomic and Molecular Sciences, Academia Sinica. * To whom the correspondence should be addressed. E-mail: [email protected] ABSTRACT High-quality GaP, GaP@GaN and GaN@GaP nanowires were grown by a convenient vapor deposition technique. The wire-like and two-layers structures of GaP@GaN and GaN@GaP core-shell nanowires were clearly resolved using X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM) and their growth directions were identified. Photoluminescence intensity of GaP@GaN nanowires increased as temperature increased. The result was interpreted by the piezoelectric effect induced from lattice mismatch between two semiconductor layers. An unexpected peak at 386 cm-1 was found in the Raman spectra of GaN@GaP and assigned to a surface phonon mode due to the interface. Detailed synthetic conditions and possible growth mechanisms of those nanowires were proposed. INTRODUCTION One-dimensional nanocrystals have been the focus of scientific researches, because they have extensive potentials in fundamental properties as well as in practical applications. III-V group compounds as a kind of important semiconductor can be applied in many fields.[1,2] Individual semiconducting nanowires have already been demonstrated to work as field-effect transistors (FETs), photodetectors and bio/chemical sensors.[3-5] More sophisticated light-emitting diodes (LEDs) and complementary diode logic devices also have been fulfilled by using n-type or ptype semicondutor nanowires. These practical applications great stimulate the develop on the synthetic technique of III-V group compounds.[6-9] For examples, GaN and GaP nanowires were synthesized by laser ablation on targets, which were composed of elements desired in nanowires and catalysts.[6] Recently, GaP nanowires have been achieved by the thermal deposition of Ga(PtBu2) in the presence of surfactants or the sublimation of the ball-milled powders at 1100 °C.[7] A convenient thermal CVD route to high-quality GaN nanowires has been reported.[8] Semiconductor heterostructures are one of several fundamental and important concepts in modern device physics due to great contributions to fundamental researches and practical optoelectronic devices.[10] Currently, the structures have been found in many devices on the base of their unique optical, electronic and structural characteristics coming from the interfaces between two semiconductors. A large number of studies on the heterostructures of a multilayer thin film, a typical 2-dimensional (2-D) nanostructure, have been reported.[11] The studies on heterostr
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