ISSN: 2277-9655 [Alwan* et al., 6(1): January, 2017] Impact Factor: 4.116 IC™ Value: 3.00 CODEN: IJESS7 http: // www.ijesrt.com © International Journal of Engineering Sciences & Research Technology [204] IJESRT INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY EFFECTS OF THE POROUS SILICON MORPHOLOGY ON THE GAS SENSOR PERFORMANCE Dr. Alwan M. Alwan*, Ruaa A Abbas * School of Applied sciences, University of Technology/Baghdad Ministry of Science and technology / Baghdad DOI: 10.5281/zenodo.245646 ABSTRACT In this work,porous silicon (PSi) based gas sensor of structure (AL/nPSi/n-Si/AL) at different morphologies was prepared on the n-type silicon substrate using IR illuminated source of wavelength (810nm). The morphological and gas sensing properties of the sample were studied, under various etching time (5-20min). The current density –voltage characteristic at temperaturefrom 25 to 150 °C of the sensor,which was sensitivity analysis based on the silicon nano size, porosity, layer thickness, and effective dielectric constant of the PSi layer.The SEM image of the PSi layer showed the formation single layer structure pore –like the cylindrical and rectangular pore shape. The porous layer after etching time (5-10min) and double of mud _like for 20min produced different dimensions with randomly distributed as an upper layer and pore _like structure as a lower layer. The current density–voltage analysis confirms that higher temperatures with the presence of CO2 gas lead to sharply increase the sensitivity with the current and voltage. Overall, the improvement that appeared on the double porous layer sensitivity due to the higher value of the surface area. KEYWORDS: poroussilicon,surfacemorphology, gas sensor,carbon dioxide. INTRODUCTION Porous silicon (PSi) is considered as a very efficient material in the chemical sensor due to its unique properties which dependent on the large surface area [1]. That change in morphology of porous silicon can be obtained by the variety of etching condition through several parameters such as current density, etching time, HF acid concentration and illumination conditions. [2]. photo electrochemical etching of silicon by using HF acid is a well- known technique for porous silicon fabrication. The electrochemical and photochemical etching method is a combination of the material interaction with the HF acid through light and current density. It has been used laser light illuminating on the silicon electrode during the anodization process and was effect its greatly in modifying of the macro-porous properties [3]. That control of the high surface area within a small volume of the pore sizes given an increase in sensor characteristics.The ability to modulate dielectric constant as a function filling moleculesmakes of the Psi a suitable dielectric material for the gas detection process [4]. All these features are lead to consider the Psi as one of the most valuable materials in the field of gas sensor technology. The Psi sensor is simple and cheap method as compared to other gas detectors that are super-sensitive could be based on Psi elements resistive [5]. The morphology and a reduced particle size play a significant role in the gaseous sensor applications, due to the increase of the specific surface area.On the other hand, Psi sensitivity is dependent also on the chemical adsorption and the physical adsorption of the gasses [6. 7]. The detection of carbon dioxide currently used in critical fields such as indoor air quality monitoring [8, 9]. The sensing devices Most of the currently available carbon dioxide are based on optical principles but they are usually bulky and expensive. In this research has been a study of several development groups in the alternative sensor for CO2 monitoring which is cheap and efficient. The semiconductor materials are always a competitive low-cost choice in many areas [10]. In this research was the study focus on the porous silicon morphology on the CO2 gas detection process. The electrical behavior in the sensing properties of (AL/nPSi/n-Si/AL) has been investigated at different temperature with the morphologies of the Psi layer.