Detection of Thin Films on Solid Surfaces Using a Contact Angle Goniometer

by Keith Foreman
Physics / Chemistry
Faculty advisor: Dr. Shawn Stone

A developing area of great interest to surface scientists is the adsorption of thin films on solid surfaces.  There is a wide variety of applications of such devices, such as corrosion prevention, passivation of microelectronic surfaces, and chemical/biochemical sensors.  Therefore, verifying the presence of such a thin film on a solid surface is critical.  Several techniques, such as Atomic Force Microscopy (AFM) and Surface Vibrational Sum-Frequency Generation (SVSFG) can provide evidence of the presence of a thin film on solid surfaces.  However, the instruments required for such techniques are quite expensive and the data collection process can be arduous.

This project presents the successful construction and implementation of a relatively simple and cost effective device, a contact angle goniometer.  A goniometer is used to acquire the angle of contact of water droplets (.2 μL) on a solid surface, from which the presence of thin films can be inferred.  Specifically, our data suggests the presence of a monolayer on gallium arsenide, an important semiconductor that has higher electron mobility than silicon.