Pulsed laser deposition of TiO_2: diagnostic of the plume and characterization of nanostructured deposits

摘要

Promising applications of TiO_2 nanostructures include the development of optical devices, sensors, pho-tocatalysts and self-cleaning coatings. In view of their importance, research on the synthesis of nanosized TiO_2 is a particularly active field. In this work we report on the investigation of the effect of laser irradiation wavelength (Q-switched Nd:YAG laser at 532, 355 and 266 nm), the temperature of the substrate and the atmosphere of deposition (vacuum, Ar and O_2) that are suitable for obtaining nanostructured deposits from TiO_2 sintered targets. The ablation plume emission is characterized with spectral and temporal resolution by optical emission spectroscopy (OES), while the surface morphology and chemical states of the material deposited on a Si (100) substrate are examined by environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) and by X-ray pho-toelectron spectroscopy (XPS), respectively. Deposits with nanostructured morphology with grain size down to 40 nm and keeping the stoichiometry of the targets were obtained at high temperature, while the highest concentration of particu-lates was observed at the longest laser wavelength of 532 nm on a substrate heated up to 650℃. In situ characterization of the ablation plume, carried out by OES, indicated the presence of emissions assigned to Ti Ⅰ, Ti Ⅱ and O Ⅰ.