Edwards Thermal Evaporator

edwardsThe Edwards Thermal Evaporator is used for thin film deposition. In our lab, the evaporator is primarily used to coat Si surfaces with nano meter scale layers of Cr (as an adhesion layer), Au and Ti. The sample and a crucible containing the desired metal coating  are placed under vacuum in a main chamber. A large current is passed through the crucible, causing the metal to evaporate. As the metal cools, evaporated material is deposited on the surface. The thickness of the material is monitored via a Quartz Crystal Microbalance (QCM) also located inside the main chamber.  As material accumulates on the quartz crystal, the natural resonant frequency of the quartz changes.  Monitoring the frequency allows for determining the rate of thin film deposition.