Photoluminescence of langasite thin films prepared from sol–gel process

La3Ga5SiO14 (LGS, langasite) thin films of stoichiometric composition on SiO2/Si(1 1 1) substrates were obtained by a sol–gel spin-coating method. The as-spin coated films were amorphous when they were heated at the temperature lower than 1100 °C. (1 1 0) preferred orientation of the films were obtained by annealing the films at temperature higher than 1200 °C. A blue photoluminescence (PL) emission peak around 429 nm was observed under an excitation wavelength of 381 nm and was suggested to originate from the Ga3+ ions at the octahedral sites. A correlation between the ionic structure and the photoluminescence behavior are discussed based on the X-ray photoelectron spectroscopy (XPS) examination of the binding energies of Ga3+2p and O2−1s.