Results are reported on the study of phase transformations in diamonds induced by nano- and picosecond pulses of KrF excimer laser (λ=248 nm) and second harmonic of a YAP:Nd laser (λ=539 nm). Main attention in the research was paid to i) laser-induced graphitization of high-quality CVD diamond plates and ii) laser-induced structure transitions in ion-implanted diamond single crystals. For CVD diamond, the thickness of the laser-graphitized surface layers was measured and the accumulation period for graphitization to occur was found to be longer for lower laser fluences. In the experiments with ion-implanted diamonds, multipulse laser irradiation at fluences lower than the graphitization thresholds resulted in progressive annealing, i.e., in an increase of the optical transmission and surface contraction. Under certain low-intensity irradiation conditions, it was also found that, competing with the annealing process, laser etching of the ion-implanted diamond occurred at extremely low rates of 10-4-10-3 nm/pulse. A correlation between the defect concentration distribution and graphitization thresholds in partially annealed ion-implanted diamonds is discussed.
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