The research of relationships between residual stress and columnar angles in oblique deposition of magnesium fluoride thin films

Abstract

MgF 2 films are obliquely deposited on glass substrates using a resistive heating Mo boat at both substrate temperatures of room temperature and 220 °C. These films have obviously columnar microstructures from SEM pictures without respect to substrate temperatures. The columnar angles of the MgF 2 films increase with the deposition angles. However, the columnar angle of MgF 2 film, deposited at a substrate temperature of room temperature, is not equal to that at 220 °C when the MgF 2 films are prepared at the same deposition angle. Also, the trend of stress behavior of the MgF 2 films, deposited at a substrate temperature of room temperature, is different from that at 220 °C due to the generation of thermal stress. The behaviors associated with stress in the MgF 2 films are measured using a phase-shifting Twyman-Green interferometer with the application of a phase reduction algorithm. Anisotropic stress does not develop in the MgF2 films with tilted columns and the residual stress depends on the deposition and columnar angles in columnar microstructures of the MgF 2 films.