Ultraviolet-reduced reduction and crystallization of indium oxide films

Structural changes stimulated by ultraviolet (UV) irradiations of sol-gel-d erived indium oxide thin films were investigated. Illumination of incoheren t UV photons (4.9 eV) from a low-pressure mercury lamp resulted in formatio n of crystalline indium metal. Irradiation of coherent UV beams from an ArF excimer laser (6.4 eV) and from the fourth harmonics of a Nd:YAG laser (4. 7 eV) was found to be effective in the crystallization of indium oxide, acc ompanied by a decrease in the sheet resistance. The lowest resistance witho ut a reduction of transmission in the visible region was achieved with a 6. 4 eV laser beam at a fluence over 10-20 mJ cm(-2) shot(-1). The results of x-ray photoelectron spectroscopy revealed that charge transfer from O2- to In3+ was induced by the incoherent and the coherent UV photons. The partial reduction with the incoherent illumination and the crystallization with th e laser irradiation are tentatively assumed to be due to electronic excitat ions in the amorphous network. (C) 1999 American Institute of Physics. [S00 21-8979(99)05401-8].