Substrate Temperature Influenced Physical and Electrochromic Properties of MoO3 Thin Films

Abstract

Molybdenum oxide (MoO3) films were deposited on glass and silicon substrates by sputtering of molybdenum target at different substrate temperatures in the range 473-573 K at a constant oxygen partial pressure of 4x10-4 mbar employing RF magnetron sputtering technique. The effect of substrate temperature on structural, morphological, electrical and optical properties of the MoO3 films was systematically studied. X-ray diffraction studies revealed that the films formed at 303 K were amorphous in nature, while those deposited at substrate temperature 473 K were orthorhombic MoO3 with crystallite size of 27 nm and the crystallinity increased with increase of substrate temperature. The scanning electron micrographs of the films deposited at 303 K were of fine grain structure in amorphous back ground and the films formed at 523 K contained the grains with shape of platelets piled one over the other with size of about 1 μm. Fourier transform infrared transmittance spectra exhibited the characteristic vibration modes of MoO3. The electrical resistivity of the films decreased with increase of substrate temperature due to partial filling of oxygen ion vacancies. The optical band gap and refractive index of the films increased with the increase of substrate temperature. The MoO3 films formed at substrate temperature of 523 K exhibits high optical modulation of 22% and coloration efficiency of 30 cm2/C.