Solid State Communications 150 (2010) 1923–1927 Contents lists available at ScienceDirect Solid State Communications journal homepage: www.elsevier.com/locate/ssc Self-catalytic growth of horizontal and straight Si nanowires on Si substrates using a sputter deposition technique Soumen Dhara a , P.K. Giri a,b,∗ a Department of Physics, Indian Institute of Technology, Guwahati, Guwahati-781039, India b Centre for Nanotechnology, Indian Institute of Technology, Guwahati, Guwahati-781039, India article info Article history: Received 3 April 2010 Received in revised form 9 June 2010 Accepted 17 July 2010 by D.J. Lockwood Available online 23 July 2010 Keywords: A. Si nanowires B. Catalyst free growth C. Raman E. Sputtering abstract We report on the growth of horizontal and straight Si nanowires (NWs) on Si substrate using sputter deposition of the Si layer followed by thermal annealing at 1000 °C and above. The growth of horizontal NWs was achieved without the use of any metal catalyst. Uniform cylindrical shaped Si NWs with a diameter in the range of 50–60 nm and a length of up to 8 μm were synthesized. The as-synthesized Si NWs have a Si core covered with a thin amorphous native oxide layer, as revealed by high resolution transmission electron microscopy. The aspect ratio of these Si NWs is in the range of 100–160. Micro- Raman studies on the NWs reveal a tensile strain on the Si NW core due to presence of a thin oxide layer. From the Raman shift, we calculate a strain of 1.0% for the catalyst free Si NW. FTIR analysis indicates the presence of interstitial oxygen atoms in the Si NWs, as expected from oxidation of Si NWs. For comparison, metal catalyst (Au) assisted Si NWs have also been grown on Si(100) substrate by a similar process. These NWs have a similar diameter and a marginally higher aspect ratio. A model for the growth mechanism of horizontal NWs is presented. This represents one of the first examples of direct horizontal growth of straight Si NWs on commonly used Si substrates suitable for nanoelectronic device fabrication. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction From the last decade, the growth of Si nanowires (NWs) has received much research attention due to its huge application prospects in nanowire based microelectronics and photovoltaics. Metal catalyzed vapor liquid solid (VLS) grown Si NWs have thus far been successfully grown and used for a wide range of functional nanodevices, such as field effect transistors, photodetectors, solar cells, biological–chemical sensors [1–4]. However, the problem of metal contamination on NWs may affect the performance and longevity of these nanodevices [5]. Further, metal induced deep level defects are efficient recombination and generation centres that have detrimental effects on the performance of most of the electronic and optoelectronic devices [6]. Very few groups have reported the catalyst free growth of Si NWs using different sophisticated techniques. Recently, Kim et al. have reported the catalyst free growth of Si NWs in a low pressure chemical vapor deposition system using silane gas [7]. Oxide assisted growth by the physical vapor deposition method can also form a catalyst free crystalline Si NWs with amorphous oxide shell [8,9]. However, in ∗ Corresponding author at: Centre for Nanotechnology, Indian Institute of Technology, Guwahati, Guwahati-781039, India. Fax: +91 361 2582749. E-mail address: giri@iitg.ernet.in (P.K. Giri). this process a high temperature is required, which is above 1200 °C. Further, the Si NWs grown in these processes are not straight and aligned. Therefore it is very difficult to incorporate these NWs in different Si nanowire based devices. Usually (111) oriented Si wafer is used for the growth of Si NWs, due to lowest surface energy along this plane. A few groups have reported catalyst assisted growth of Si NWs on Si(100) substrate. However there are no reports on the growth of Si NWs on Si(100) surface using sputtering techniques. To the best of our knowledge, previously there were only two reports on the use of magnetron sputtering for Si NWs growth on two different substrates [10,11]. The structure of these Si NWs was found to be bundled and fullerene/non-cylindrical shaped. Further, these non cylindrical shaped NWs were grown at a high substrate temperature (600–850 °C) and using an Au catalyst. Thus, catalyst free growth of Si NWs remains an important challenge for the materials community. The majority of the studies have reported catalyst mediated growth of vertical Si NWs on Si substrates. There are no systematic studies on the growth of horizontal Si NWs that are appropriate for the fabrication of nanoelectronic devices. In this article, we report a growth of horizontal and straight Si NWs on silicon substrates using a sputter deposition technique fol- lowed by thermal annealing. Si NWs are grown on Si(100) sub- strate by a self catalytic growth method, without the use of any metal catalyst. The structure, morphology and composition of the Si NWs were studied using X-ray diffraction, Raman scattering, 0038-1098/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2010.07.031