Raman spectroscopy of nanostructured silicon fabricated by metal-assisted chemical etching Dr. PhD Igor Iatsunskyi* , 1, 2 , Prof. Stefan Jurga 1 , Prof. Valentyn Smyntyna 2 , Mykolai Pavlenko 2 , Valeriy Myndrul 2 , Anastasia Zaleska 2 1 Nanobiomedical Center, Adam Mickiewicz University in Poznan ul. Umultowska 85, PL 61614 Poznań, Poland 2 Department of Experimental Physics, Odessa I.I. Mechnikov National University, Str. Pastera 42, 65023, Odessa, Ukraine, yatsunskiy@gmail.com ABSTRACT In this work, we present a detailed experimental Raman investigation of nanostructured silicon films prepared by metal- assisted chemical etching with different nanocrystal sizes and structures. Interpretation of observed one and two-phonon Raman peaks are presented. First-order Raman peak has a small redshift and broadening. This phenomenon is analyzed in the framework of the phonon confinement model. Second-order Raman peaks were found to be shifted and broadened in comparison to those in the bulk silicon. The peak shift and broadening of two-phonon Raman scattering relates to phonon confinement and disorder. A broad Raman peak between 900-1100 cm -1 corresponds to superposition of three transverse optical phonons ~2TO (X), 2TO (W) and 2TO (L). Influence of excitation wavelength on intensity redistribution of two-phonon Raman scattering components (2TO) is demonstrated and preliminary theoretical explanation of this observation is presented. Keywords: nanosilicon, metal-assisted chemical etching, Raman spectroscopy 1. INTRODUCTION In recent years, silicon nanostructures have been extensively studied both theoretically and experimentally to realize their possible applications. For instance, silicon nanowires (Si NWs) exhibit novel chemical and physical properties due to their dimensions at the nano-scale, and offer great potential in the fields of electronics, photonics, chemical sensors and biological systems [1-3]. Nanostructured silicon is presently of widespread interest because Si is an extremely promising material not only for electronics but optoelectronics and solar cells [4-6]. Raman scattering has become a standard tool to study the silicon and nanostructured silicon for many years [7-10]. Raman-scattering studies of nanomaterials give us information about energy dispersion, structure, bonding and disorder. The analysis of nanostructures is mainly based on the phonon confinement model in which the finite crystallite size is taken into account by weighting the phonon-scattering efficiency. Confinement effects in nanostructures lead to modifications of the electronic, optical and vibrational properties. Unfortunately, if a first-order Raman spectrum of nanocrystalline silicon has been studied extensively, the second-order Raman scattering is investigated marginally [11, 12]. In the second-order Raman scattering process, two phonons of equal and opposite momentum participate and produce either line or broad continuous spectrum. Zone edge phonons, which appear only in higher-order Raman scattering, correspond to large wave vectors and are sensitive to short-range disorder. The nature of a material, such as crystalline or amorphous, can therefore be ascertained by analyzing the higher-order phonons as well. Study of second- order Raman scattering, in addition to first-order spectra, provides important information on the vibrational modes, energy structure, and morphology of nanostructured materials. Besides, second-order Raman scattering exhibits a higher sensitivity to nanoparticles size than first-order scattering [11]. *yatsunskiy@gmail.com; phone +380 673660744 Optical Micro- and Nanometrology V, edited by Christophe Gorecki, Anand Krishna Asundi, Wolfgang Osten, Proc. of SPIE Vol. 9132, 913217 · © 2014 SPIE CCC code: 0277-786X/14/$18 · doi: 10.1117/12.2051489 Proc. of SPIE Vol. 9132 913217-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 05/14/2014 Terms of Use: http://spiedl.org/terms