The gas-sensing characteristics of individual ZnO nanowires having single-crystalline and multiple grain boundaries, fabricated using bottom-up and top-down approaches, respectively, were studied. The sensor response of individual ZnO nanowires with multiple grain boundaries was enhanced some three times as compared to that of single-crystalline ZnO nanowires; due to well-known grain-boundary modulations. However, the response and recovery times of the individual ZnO nanowires with multiple grain boundaries were much slower than those of the single-crystalline ZnO nanowire, indicating the presence of oxygen diffusion resistance to grain boundaries due to the relatively fast surface kinetic reaction. Simplified kinetic diffusion modelling and experimental results could quantify the significant diffusion resistance of gas molecules into the grain boundaries of the individual ZnO nanowires.

The Effect of Grain Boundaries Inside the Individual ZnO Nanowires in Gas Sensing. H.W.Ra, R.Khan, J.T.Kim, B.R.Kang, Y.H.Im: Nanotechnology, 2010, 21[8], 085502