Materials Science and Engineering B72 (2000) 117 – 120 Synthesis and photoluminescence properties of semiconductor nanowires Z.G. Bai a , D.P. Yu a, *, J.J. Wang a , Y.H. Zou a , W. Qian a , J.S. Fu a , S.Q. Feng a , J. Xu b , L.P. You b a Department of Physics, National Key Laboratory of Mesoscopic Physics, Peking Uniersity, Beijing 100871, PR China b Electron Microscopy Laboratory, Peking Uniersity, Beijing 100871, PR China Abstract GaSe and Si nanowires (SiNWs) were synthesized by physical evaporation. The photoluminescence (PL) properties of the Si nanowires were investigated in correlation with the diameter of the crystalline core. Intensive light emission was observed peaking at dark red, green and blue regions for the as grown and partially oxidized SiNW samples. The red PL emission is ascribed to the quantum confinement effect of the crystalline core of the SiNWs, while the green and blue ones are attributed to the radiative recombination of the defect centers in the amorphous silicon oxide layer surrounding the SiNWs. © 2000 Published by Elsevier Science S.A. All rights reserved. Keywords: Nanowires; Photoluminescense; Crystalline core www.elsevier.com/locate/mseb 1. Introduction Semiconductor nanomaterials have attracted much research interest. For example, porous silicon and sili- con nanocrystallites have been extensively studied as promising candidates for light emitting materials [1,2]. Due to their peculiar structure characteristics and the size effect, both show visible PL, which is very interest- ing both for the understanding of some fundamental physical problems, such as quantum confinement effect, and for potential opto-electronic technological applica- tions. So far, porous silicon and silicon nanocrystallites were found to have efficient PL covering almost the whole range from infrared to ultraviolet region. There are mainly two popular models explaining the physical origin of the observed PL, which emphasize either the quantum confinement or the surface states. One impor- tant reason why there are still some debates on this issue is that porous silicon has a large heterogeneity and a complex morphology, which may cause some difficulty and uncertainty in the explanation of the origin of the visible PL. Recently, real free-standing SiNWs have been synthesized by Yu et al. [3,4] and Morales et al. [5]. The most striking characteristics of the SiNWs are the high purity and the uniform diame- ter distribution, which make it possible to give some conclusive experimental results on the size dependence of the PL properties of the SiNWs, thus reveal the physical origin of different visible PL. In this article we will report on the synthesis of SiNWs and GaSe nanowires and the PL properties of the SiNWs. 2. Synthesis of SiNW and GaSe nanowires The synthesis of the GaSe nanowires and SiNWs was conducted by physical vaporization of mixed target materials. The details of the synthesis of the SiNWs was reported elsewhere [3,4]. The GaSe nanowires were prepared by the following procedure: Se powder was placed separately with a mixture of Ga and Ga 2 O 3 powder (mol ratio 4:1), which was heated to a tempera- ture of about 1000°C in a reduced atmosphere. The product was collected on a Si wafer. A Hitachi H9000 NAR high-resolution electron microscope (HREM) with a point-to-point resolution of 0.18 nm (accelerat- ing voltage at 300 kV) was used to characterize the products. * Corresponding author. Fax: +86-10-6275-1615. E-mail address: yudp@pku.edu.cn (D.P. Yu) 0921-5107/00/$ - see front matter © 2000 Published by Elsevier Science S.A. All rights reserved. PII:S0921-5107(99)00501-2