Structural and Optical Properties of HfO2 Films on Sapphire Annealed in O2 Ambient

The structural properties of HfO 2 films could be improved by thermal treatment owing to their crystallization.We deposited HfO 2 films on sapphire by radio frequency (RF) magnetron sputtering, whose base vacuum pressure was lower than 4.5 × 10 -6 Pa, RF power was 100 W, working temperature was 200°C, working pressure was 3 mTorr, and the density of the active gas (Argon) was 20 sccm.After depositing the HfO 2 films, the samples were thermally treated by rapid thermal annealing (RTA) in O 2 ambient at different temperatures.Subsequently, the measured physical properties (structural, morphological, and optical) indicated that the crystallite size, refractive index at a wavelength of 632 nm, and packing density increased with rising temperatures.In particular, an HfO 2 film thermally treated at 800°C in O 2 ambient had the highest refractive index of 2.0237 and packing density of 0.9638.The relation between optical and structural properties was also analyzed.