Ujjwal Das, an associate scientist at the University of Delaware's Institute of Energy Conversion, examines a silicon wafer after a thin layer of sulfur - less than 5 nanometers thick - was deposited on the surface. In the background, doctoral students Robert Theisen and Isaac Lam watch a silicon wafer emerge from the atmospheric pressure vapor treatment reactor, where it was treated with hydrogen sulfide and hydrogen selenide gases. The reactor was developed at IEC.