Structural and optical properties of H 2 diluted c-Si/a-SiO x core-shell silicon nanowire Bhabani Sankar Swain • Bibhu Prasad Swain • Khalid Mahmood • Seung-Min Yang • Nong-Moon Hwang Received: 12 May 2014 / Accepted: 6 August 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract We observed photoluminescence quenching in crystalline (c) Si/amorphous (a) SiO x core-shell sili- con nanowires (Si-NWs). We observed that the photo- luminescence (PL) intensity strongly depends on the stoichiometry of outer a-SiO x matrix, which was char- acterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The PL showed a broad-range emission from 1.6 to 2.4 eV with the peak centered at 2.27 eV, which quenched as the oxygen content decreased from 60.5 to 54.6 at.%. Both trans- verse optic and longitudinal optic signatures of Si–O–Si were shifted to lower wavenumbers, which indicate the modification of chemical networks in core-shell Si-NWs. The minority carrier life time (s) increased from 3.4 to 7.5 ls as the diameter of core Si increased from 22 to 78 nm, indicating the decrease of trap densities and alternation trap states. The reason for PL quenching is mostly attributed to the structural and stoichiometry changes in outer a-SiO x of c-Si/a-SiO x -NW. 1 Introduction One-dimensional (1D) c-Si/a-SiO x core-shell silicon nanowire (Si-NW) has been considered as the next gener- ation material, which can compete with the planar tech- nology, due to its possible applications in devices such as solar cell [1], light-emitting diode [2], anode materials for Li ion battery [3], bio/chemical sensor [4], etc. So far, single crystalline Si-NWs have not been considered in photonic devices due to their indirect band gap. However, silicon nanocrystals embedded in a SiO 2 matrix show excellent optical properties by emitting visible emission [5]. The emission strongly depends upon the interface, surface and structural properties of core Si and outer a-SiO x . The photoluminescence (PL) quenching of Si nanocrystals and porous Si have potential applications in various gas sensors [6–8]. The PL quenching is mainly attributed to chemical derivatization of surface in the nanostructure material as the surface-to-volume ratio is an important factor to regulate the electronic states of Si-NWs [9]. The PL quenching in Si nanoparticles observed in phospholipid vesicle bilayers was previously studied [10]. The PL quenching was also observed in porous silicon deposited by various metal adsorbates solution and evap- oration method [11]. However, the PL quenching in core- shell Si-NWs has not been reported. In this article, PL quenching by structural changes in c-Si/a-SiO x -NWs is investigated. The structural and the stoichiometry of outer a-SiO x were characterized by Fou- rier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). We correlate both data with minority carrier lifetime (s) measured by microwave photo-conductance decay (l-PCD) measurement. We observed that the PL quenching is strongly tuned by the oxidation state of Si in a-SiO x . B. S. Swain (&)  S.-M. Yang  N.-M. Hwang Department of Materials Science and Engineering, Seoul National University, Seoul, Republic of Korea e-mail: bsswain@snu.ac.kr; bsswain@kookmin.ac.kr B. S. Swain School of Advanced Materials Engineering, Kookmin University, Seoul, Korea B. P. Swain Centre for Materials Science and Nanotechnology, Sikkim Manipal Institute of Technology, Majitar, Rangpo, Sikkim, India K. Mahmood School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea 123 Appl. Phys. A DOI 10.1007/s00339-014-8675-x