Ammonia sensing by silicon nanowires (SINWs) obtained through metal assisted electrochemical etching

Abstract

Present work reports fabrication of silicon nanowires (SINWs) through metal-assisted electrochemical etching. The process of etching is carried out with the help of dc current supplied through Agilent 6634B dc power supply on silver electroplated silicon(Si) wafer. The method provides ordered SINWs with larger surface area. Morphology, as seen from FESEM shows vertically aligned bunched SINWs of average length of 23µm with porous structure of finely distributed pores over the surface. Electrochemically etched SINWs shows high sensitivity to gas/vapors due to its highly porous nature, by capturing the gas molecules through voids present on the surface. In the present work different vapors viz. acetone, chloroform and ammonia are tested. Among these SINWs are seen to be fairly selective to ammonia. Ammonia sensing measurements are done for gas concentrations from 10 to 100 ppm. Sensitivity of the sensor increases with increasing concentrations. Electrical conductivity of SINWs is reduced in presence of ammonia. The experimental results highlight fair response and recovery times with good correlation coefficient to ensure prospect of developing SINWs based gas sensor for possible utilization in the medical and environmental fields, for example.