EBL Patterned ITO Contacts for Single Nanowire Devices

Sammanfattning: Nanowires have attracted interest as fundamental building blocks for electronic and optoelectronic devices as well as for fundamental research. Photonic studies of single nanowire devices typically involve patterning of metal electrodes for electronic access, yet plasmonic ef- fects between the metal contacts and the light source may perturb experimental measurements. An alternative to conventional metallic contact materials is transparent conductive oxides (TCOs), such as in- dium tin oxide (ITO). ITO is a well-studied TCO often used as trans- parent top contact for optoelectronic devices, including nanowire array devices. Contacting single nanowires requires high-resolution pattern- ing of the ITO electrodes, which has never been reported using EBL. Here, we demonstrate a simple method for patterning sub 100nm wide ITO lines with EBL and lift-off. We contacted single InAs nanowires and demonstrated ohmic ITO contacts and measured for the rst time a specic contact resistivity of (3.94+-2.79)X10^(-5)Ohm-cm^2, which to the best of our knowledge is the lowest specic contact resistivity between ITO and any semiconductor. Although ITO properties were improved by annealing, the ITO contact resistance increased which was hypoth- esized to be caused by oxygen diusing from ITO to the InAs during the heat treatment. The contact resistivity of 3.5nm/5.5nm/100nm Ni/Au/ITO contacts to InAs nanowires was generally higher than that of pure ITO contacts at 10^(-4)Ohm-cm^2. Annealing indicated that con- tact resistivity of these contacts could be improved, but no denitive conclusion could be drawn from the statistical analysis.