Synthesis and characterization of silicon nanorod arrays for solar cell applications

Silicon nanorods have been grown by chemical vapor deposition of silane, using both gold and indium as catalysts for the vapor liquid solid (VLS) process. Conditions for optimal rod morphology for each catalyst were identified by varying silane partial pressure and temperature in the range P = 0.05-1 Torr and T = 300-600 C, respectively. In most cases, catalyst particles were formed by partial de-wetting of evaporated films of the catalytic material to form droplets with diameters of tens to hundreds of nanometers. Also, periodic arrays of catalyst particles with controlled size and spacing were achieved both by the use of porous alumina membranes and also by electron-beam lithography. Using these techniques, silicon nanorods were grown with diameters of 100 nm to microns and lengths of microns to tens of microns. Four-point and gate-bias-dependent resistance measurements were made on single wires, and these indicate that rods we have grown with gold catalysts and phosphine doping have metal-like conductivity.