Temperature-dependent optical and mechanical properties of obliquely deposited MgF2 thin films

The temperature-dependent optical and mechanical properties of magnesium fluoride (MgF2) thin films with small columnar angles have been presented. Electron-beam evaporation method was used to prepare MgF2 thin films with two different columnar angles of 6° and 24°. MgF2 thin films were deposited on B270 glass substrates and silicon wafers, respectively. The temperature-dependent optical and mechanical behaviour of MgF2 thin films with different columnar angles were obtained by elevated temperature in the range 30-110°C. The wavelength shift with temperature was measured by a spectrophotometer for evaluating the stability of obliquely deposited MgF2 films. The microstructure and surface roughness of the MgF2 thin films have been measured by scanning electron microscope (SEM) and atomic force microscopy (AFM). Characteristics for the temperature-dependent optical properties and biaxial residual stresses of MgF2 thin films deposited at two different oblique angles have been measured and compared. The residual stress of MgF2 thin films deposited on the B270 substrates has been plotted against the measurement temperature, both of the samples showed a linear dependence