Angle-resolved analysis of desorbed species in pulsed laser ablation on cadmium tungstate single crystal surfaces with different orientations studied by time-of-flight mass spectrometry

Angular distributions of species desorbed by pulsed laser ablation were studied on three single crystal CdWO4 surfaces with different orientations. Sharp angular distribution of desorbed species to surface normal was analyzed with nth order of cosθ dependency. The difference of n values of desorbed ionic O2+ species on the three different surfaces was explained by a secondary thermal effect. However, the characteristic sharp angular distribution was interpreted to be clued by an initial photochemical process. The n values of desorbed O+, Cd+, W+ and WO2+ were simultaneously compared on the surfaces. The lighter-mass species showed sharper angular distributions than the heavier-mass species. The result was explained by a collision between them. Pseudo Mach numbers of ablated species were studied as a function of desorbing angle θ to evaluate both the flow velocity factor and the collision factor.