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

Abstract

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.