La3Ga5SiO14 (LGS, langasite) thin films of stoichiometric composition on SiO2/Si(111) 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 degrees C. (110) preferred orientation of the films were obtained by annealing the films at temperature higher than 1200 degrees 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 Ga(3+)2p and O(2-)1s. (c) 2007 Elsevier B.V. All rights reserved.