Physica E 36 (2007) 65–72 Role of surface texturization on the gas-sensing properties of nanostructured porous silicon films Shailesh N. Sharma a,Ã , G. Bhagavannarayana b , Umesh Kumar, R. Debnath c , S. Chandra Mohan d a Electronic Materials Division, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110 012, India b Materials Characterization Division, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110 012, India c Central Glass & Ceramic Research Institute, Raja S.C. Mullick Road, Kolkata 700 032, India d Department of Applied Chemistry, Delhi College of Engineering, New Delhi 110042, India Received 7 June 2006; accepted 26 July 2006 Available online 13 October 2006 Abstract In this work, by means of high-resolution X-ray diffraction, excitation l-dependent photoluminescence (PL) and Fourier transform infrared studies, it has been demonstrated that hydrogen-passivated porous silicon (PS) films with high PL and stability can be obtained on p-type Si(1 0 0) substrate by simple texturization process rather than by resorting to any anodic, chemical or thermal oxidation of PS [T. Karacali, B. Cakmak, H. Efeoglu, Opt. Express 11 (2003) 1237]. PS formed on textured substrates is superior to PS formed on polished silicon substrates at the same current density and time of anodization. The application of PS films formed on textured substrate as a gas sensor has been demonstrated and it shows higher sensitivity values upon exposure to ethanol as compared with polished PS specimens of similar porosity. The improved properties are attributed to the formation of highly porous vertical layers separating macroscopic domains of nanoporous silicon. r 2006 Elsevier B.V. All rights reserved. PACS: 07.07.Df; 61.10.Nz; 68.43.h; 68.47.b; 78.55.Mb Keywords: Porous silicon; Textured substrate; Polished substrate; High resolution X-ray diffraction; Photoluminescence; Gas-sensing properties 1. Introduction In recent years, porous silicon (PS) has been proposed as a new material for solid-state gas sensors because of its huge surface-to-volume ratio, its high chemical reactivity at room temperature and its potential compatibility with silicon integration technologies [1–3]. The sensitivity of PS to different vapours depends on porosity, pore structure and size distribution of pores [2]. Again, these are controlled by formation current density, electrolyte con- centration, anodization time, doping level of the substrate, etc. [2,3]. Thus different vapours having widely different molecular weight and dimension can be sensed selectively by tailoring the morphology and corresponding adsorbing properties of PS-sensing layer [2]. The gas-modified variables are conductance/current or capacitance in elec- trical sensors and photoluminescence (PL) in optical ones [4]. However, the use of gas-sensing electrical methods in practical devices is limited by the high resistivity of the as- made PS layer. Therefore, it is imperative to form highly stable, stress/strain-free PS layers for its possible applica- tion as gas sensors. Recent advancement in miniaturization especially in silicon micro technology has encouraged researchers to develop miniaturized gas sensors which offers general advantages with respect to batch fabrication and reduction of cost [5]. The requirements for good gas sensors for practical applications are: (i) good sensitivity over a wide range of temperature, (ii) short response time, (iii) good reproducibility and (iv) low cost [5]. Though PS has potential in developing CMOS-compatible gas sensors, it ARTICLE IN PRESS www.elsevier.com/locate/physe 1386-9477/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.physe.2006.07.024 Ã Corresponding author. Fax: +91 11 25726938. E-mail address: shailesh@mail.nplindia.ernet.in (S.N. Sharma).