Microscale Contacts for Nanowire Characterization Using Microscope Projection Photolithography

Microscope projection photolithography (MPP) offers a versatile method of prototyping microscale devices. The benefits of MPP include the ability to create features at a variety of dimensions, the ability to work outside of a cleanroom, and the ability to use robotic microscope stage controls to adjust the positions of features easily and accurately. This makes MPP a precise, yet flexible technique ideal for manufacturing contact pads that can be used to investigate the properties of individual nanowires. An enormous breadth of research has been dedicated to the synthesis and characterization of nanowires. The properties of individual nanowires can, however, vary greatly between syntheses or within a batch. Characterization of individual nanowires remains an important step in the scale-up of these materials. Their characterization does, however, often require complex and highly sensitive self-assembly techniques to arrangenanowires on substrates with proper placement of electrical contacts. Some work has been done on techniques for the selective characterization of individual nanowires, but those methods rely on using focused electron beam writing techniques to connect nanowires to pre-existing electrical contacts. The study of nanowires would benefit from a rapid, flexible approach to fabricating contacts for individual nanowires. This study demonstrates a system for fabricating electrical contacts with minimum feature sizes of ~0.9 µm on individual nanowires (e.g., diameters from <75 to >125 nm) that are positioned randomly on a small substrate (e.g., <1 cm^2). Designs for double and quadruple contact pads are shown to enable the effective measurement of the electrical properties of individual nanowires. The techniques provided herein can provide a rapid, simple, and customizable method of studying individual nanowires.