Preparation and optical, nanomechanical, negative thermal expansion properties of Sc2W3O12 thin film grown by pulsed laser deposition

Abstract

Negative thermal expansion Sc2W3O12 thin films have been grown on silicon and quartz substrates by pulsed laser deposition (PLD). The effects of oxygen pressure, substrate temperature and annealing temperature on the morphologies and phase composition of the Sc2W3O12 thin films were systematically investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The negative thermal expansion, optical and nanomechanical properties of the Sc2W3O12 thin films were characterized by high temperature X-ray diffraction, spectrophotometry and nanoindentation. The results indicate as-deposited Sc2W3O12 thin films to be amorphous. Orthorhombic Sc2W3O12 thin films were observed to form by heating at 1000°C for 7min in air. The Sc2W3O12 thin film deposited at 500°C under an oxygen pressure of 20Pa has the lowest root mean square (RMS) roughness value. Meanwhile it also shows the optimum optical performance with an average transmission of over 85%. The Young's modulus (E) of the Sc2W3O12 thin film is 153.40GPa and the hardness (H) is 8.62GPa. The orthorhombic Sc2W3O12 thin film exhibits an anisotropic negative thermal expansion with an average linear thermal expansion coefficient was calculated to be −3.0×10−6K−1 in the temperature range from 25°C to 600°C.