COLORATION EFFECT OF PULSED LASER ON WO3

When laser pulses irradiate the surface of the sample WO3, an interesting coloration effect is obtained. Only by one pulse of XeCl laser irradiation (wavelength: 308 nm, pulse duration: 36 ns, output power: 100 mJ/pulse), a significant color change appears. X-ray photoelectron spectroscopy (XPS) shows that a partial reduction process of WO3 occurs and conduction band electrons appears. X-ray diffraction pattern indicates that the lattice parameters of the colored samples are increased. A molten layer can be seen in scanning electron microscopy (SEM) image. It may be concluded that the coloration effect of pulsed laser undergoes a process different from that of electro- or photo- chromism, and may be attributed to thermochromism and substoichiometric WO3 is formed. The coloration process is characterized by its high speed and stability.