Effect of gamma irradiation and heat treatment on the optical properties of SbNbO₄ ferroelectric thin films

Abstract

SbNbO₄ ferroelectric thin films were formed by using d.c. magnetron sputtering. The orthorhombic SbNbO₄ ferroelectric phase was formed at about 600°C under relatively low pressure of about 1.2mTorr. The optical reflection (R) and transmission (T) spectra in the wavelength range 190—800 nm of the films deposited on sapphire substrates were measured and hence the absorption coefficient (α) was estimated. The allowed indirect transitions were found to be responsible for interband transitions of SbNbO₄ films. The absorption coefficient α was calculated as a function of γ-dose and as a function of heat treatment at 500°C and 700°C. The values of optical energy gap E_g and optical moment E_p for the electronic interband transition of irradiated and annealed SbNbO₄ films were deduced. A number of bands show a continuous shift in position and an increase in intensity with increasing γ-dose and annealing temperature.

Key Words:

• Ferroelectrics
• SbNbO₄ films
• Optical properties
• γ-irradiation

PACS:

• 78.66
• 71.80