River is also a member of the University Honors College. His thesis title is "Thermal conductivity measurements via the 3-omega method", which includes his research in CSMC on the thermal conductivity of AlPO (aluminum oxide phosphate) films, on which he collaborated with Cathy Page's group. He also received an Undergraduate Research, Innovation, Scholarship and Creativity (URISC) Award. The URISC program is intended to enable OSU undergraduate students to develop a scholarly relationship with faculty early in their academic careers.
River built an apparatus that measures how effectively films conduct heat away from a heating element evaporated on the film surface. Heat conduction is frequency dependent, so he used a lockin amplifier to isolate the heater voltage third harmonic which contains the relevant information. A thin film on a substrate increases the thermal resistance of the stack by ΔR. At low frequency, ΔR is independent of frequency and inversely proportional to the thermal conductivity of the film. Imperfect contact at the heater/film and film/substrate interfaces produces a similar effect, so he measured a series of films of different thickness to isolate the film contribution. AlPO's thermal conductivity is smaller than that of most silica glasses, making it a very good thermal insulator. AlPO is transparent to visible light, but the AlPO films on silicon on the right are colored because thin-film interference causes the films to selectively reflect particular colors that correspond to their thickness.