Electrodeposition of high aspect ratio indium antimonide nanowires on porous anodic alumina (PAA) membranes.

摘要

In the recent past, there has been an increasing interest in nanostructured III-V semiconductor materials due to their potential applications including nanowire transistors, molecular electronics and thermoelectric devices. In particular, Indium Antimonide (InSb) has generated a lot of interest due to its direct band gap (0.18 eV), very high electron mobility, and ballistic lengths of up to 700 nm at 300K. Compared to the regular methods of fabricating InSb nanowires, such as vapor-liquid-solid (VLS) and physical vapor deposition (PVD), the process of electrodeposition on porous anodic alumina (PAA) templates has the ability to synthesize higher aspect ratio nanowires that is not possible using PVD (due to pore closure effect). Moreover, using the VLS method may cause the incorporation of the catalyst into the nanowires, which may be difficult to remove. This is most likely the first time the electrodeposition of InSb nanowires with an average diameter range of 15-20 nm has ever been demonstrated and reported. In this work, high aspect ratio InSb nanowires have been successfully electrodeposited into a PAA template. The template was fabricated by two-step anodization of an aluminum layer, that had been deposited on a silicon wafer with a thin layer of titanium (adhesion promoter), sandwiched between the two. The template exhibited average pore diameters in the range of 15 - 20 nm. The insulating oxide barrier layer at the pore bottom is usually removed by a plasma etching process before the electrodeposition step. However, for this study a relatively new technique of applying a reverse bias anodization, was optimized and used to break through the oxide barrier layer. The InSb nanowires were then synthesized in the PAA templates using the electrodeposition process. Finally, the physical and material properties of the nanowires were characterized using Field Emission Scanning Electron Microscopy and Raman Spectroscopy.