Solid State Communications 149 (2009) 352–356 Contents lists available at ScienceDirect Solid State Communications journal homepage: www.elsevier.com/locate/ssc Blue–violet photoluminescence from colloidal suspension of nanocrystalline silicon in silicon oxide matrix Mallar Ray a,∗ , Kakali Jana a , N.R. Bandyopadhyay a , S.M. Hossain b,1 , Daniel Navarro-Urrios b , P.P. Chattyopadhyay c , Martin A. Green d a School of Materials Science and Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711103, West Bengal, India b Dipartimento di Fisica, Università di Trento, Via Sommarive 14, 38100 Povo, Italy c Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711103, West Bengal, India d ARC Photovoltaics Centre of Excellence, University of New South Wales, Sydney 2052, Australia article info Article history: Received 1 August 2008 Received in revised form 2 December 2008 Accepted 11 December 2008 by D.D. Sarma Available online 24 December 2008 PACS: 78.55.-m 81.20.Ev 78.55.Ap 61.46.Hk Keywords: A. Silicon nanocrystal B. Mechanical milling C. Blue–violet photoluminescence abstract We report room temperature visible photoluminescence (PL), detectable by the unaided eye, from colloidal suspension of silicon nanocrystals (nc-Si) prepared by mechanical milling followed by chemical oxidation. The PL bands for samples prepared from Si wafer and Si powder peak at 3.11 and 2.93 eV respectively, under UV excitation, and exhibit a very fast (∼ns) PL decay. Invasive oxidation during chemical treatment reduces the size of the nc-Si domains distributed within the amorphous SiO 2 matrix. It is proposed that defects at the interface between nc-Si and amorphous SiO 2 act as the potential emission centers. The origin of blue–violet PL is discussed in relation to the oxide related surface states, non- stoichiometric suboxides, surface species and other defect related states. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction Since Canham’s [1] report on room temperature light emission from porous Si, there has been great interest surrounding the topic aimed at understanding the origin of PL and possible application in light emitting devices. Efficient room-temperature PL has been obtained from nc-Si embedded in SiO 2 matrix, having adequate structural stability for reliable fabrication of solid light emitters [2]. A wide range of PL emission bands ranging from UV to NIR have been reported for such systems prepared by different techniques, like crystallization of amorphous SiO 2 , Si + implantation in SiO 2 , Si rich SiO 2 grown by chemical vapor deposition or by sputtering, etc. It has been demonstrated that stable luminescence of nc-Si in Si oxide films peaks in the NIR region even when the size of nc- Si is ∼2 nm [3], implying difficulties in obtaining efficient visible luminescence, especially in the blue–green range [4]. ∗ Corresponding author. Tel.: +91 33 26688140; fax: +91 33 26682916. E-mail address: mray@matsc.becs.ac.in (M. Ray). 1 Permanent address: Department of Physics, Bengal Engineering and Science University, Shibpur, Howrah 711103, India. Earlier studies have examined the microstructural features induced in elemental Si by high energy ball milling [5–7]. Milling of elemental Si in Spex-8000 shaker mill in sealed argon atmosphere resulted into two phase amorphous and nc-Si [6]. Shen et al. [7] have shown room temperature PL emission with peak positions ranging from 890 to 900 nm from nc-Si in Si-oxide matrix prepared by high energy ball milling. In this communication, we report intense violet–blue emission from colloidal suspensions of nc-Si in Si-oxide matrix prepared by chemically induced oxidation of mechanically milled Si. To the best of our knowledge there has been no previous report on blue PL from nc-Si prepared by ball milling. The novel and inexpensive synthesis route of nc-Si in oxide matrix, exhibiting blue–violet PL, opens up a huge scope for potential applications. 2. Experimental details Si powder from two different sources were used as starting materials — (i) commercial Si powder, with average particle size 20 μm, purchased from Alfa Aesar with nominal purity of 99.9% (sample: S1) and (ii) Si powder prepared from 2–5  cm resistivity, 0038-1098/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2008.12.023