Electrical contact fabrication on vertically aligned Zn O nanowires investigated by current sensing AFM

We present a simple method for generating vertically aligned (VA) ZnO nanowire (NW) arrays with tailored electrical top contacts, suitable for photodetector and photovoltaic applications. ZnO NWs were synthesized on Si substrate in house using a hydro-thermal method, producing dense and highly organized vertical ZnO NW (50-100nm) arrays. The vertical geometry of the NW arrays facilitated further processing of the NW structures and streamlined in situ characterization of individual NWs as well as entire NW ensembles. The top contact metallization involved depositing a thin film of low work function metals such as aluminum (5nm) followed by a thin film of gold (15nm) onto NW arrays, partially embedded in an insulating silsesquioxane-based material (SOG-400F). The I-V characteristics of individual ZnO NWs were measured using current sensing atomic force microscopy (CS-AFM). Compared with arrays of as-grown ZnO NWs, the metalized top contacts of NWs resulted in improved I-V characteristics with good Ohmic behavior at the metal-semiconductor contact (MSC).