  In the present work, HfO2 thin film (100nm) has been deposited by sputtering
technique and annealed at various temperatures ranging from 400 to 1000\degree
(in step of 200 \degree) in O2 ambient for 10 min. The samples have been
characterized using XRD, FTIR, EDAX, AFM and Laser Ellipsometer. The impact of
annealing temperatures in O2 ambient on structural properties such as
crystallite size, phase, orientation, stress have been studied using XRD. The
Hf-O phonon peaks in the infrared absorption spectrum are detected at 512, 412
cm^-1 . The stretching vibration modes at 720 cm^-1 and 748 cm^-1 correspond to
HfO2. AFM data show mean grain size in the range of 38 nm to 67 nm. The film
reveals variation in structural properties, which appears to be responsible for
variation in oxygen percentage, refractive index (1.96 to 2.01) at 632 nm
wavelength and roughness (6.13nm to 16.40nm). Annealing temperature as well as
ambient condition has significant effects on stress, crystal size and thus the
arrangement of atoms. For good quality film, annealing temperature larger than
600 \degree is desired.
