Preparation and optical study of Au nanograins in amorphous La-oxide medium

Gold-incorporated lanthanum oxide films have been prepared by the vacuum evaporation method on glass and silicon substrates. Samples were investigated by X-ray fluorescence, X-ray diffraction, UV–vis–NIR absorption spectroscopy, and DC-electrical measurements. Sample with molar incorporation level of about 4% consists of Au-nanograins (4.5 nm) embedded in amorphous La-oxide and exhibits insulating properties. Sample with molar incorporation level of 7% consists of Au-nanograins (15 nm) embedded in amorphous La-oxide and exhibits conducting behaviour, which refers to an insulator–metal (I–M) transform. The I–M transform was explained due to the band overlapping effect.