CC BY
12LM-PS-9
Role of adsorbed water in fs laser nanoablation of diamond
V. Gololobov1, V. Kononenko1, V. Konov1
1Prokhorov General Physics Institute of the Russian Academy of Sciences, Natural Scienses Center, Moscow, Russian Federation
Earlier (see, e.g. [1, 2]) we have shown that laser nanoablation of diamond requires oxygen-containing gas environment (atmospheric or rare air).
For better understanding of chemical processes that govern laser nanoablation, in the present work we measured nanoablation rates at different air pressures in the range from 1 atm down to 10-7 torr. Polished monocrystalline CVD diamond samples were irradiated by multiple 100 fs pulses (repetition frequency 1 kHz) with wavelength X = 400 nm and fluence 3 J/cm2. It was found that quite unexpectedly the ablation rate dependence on air pressure is non-monotonions (Fig.1).
Almost equal values of rates in air and at pressure 10-7 torr as well as 20-fold increase near 10-5 torr are explained by competition of the two phenomena. The first is reaction of weakly bonded surface carbon atoms with oxygen which rate grows linearly with oxygen pressure and results in diamond etching. The second is adsorbed water layer formation in air that prevents penetration of oxygen molecules to the sample surface. The thickness and homogeneity of such layers drops with air pressure decrease and at lower pressures their shielding influence on surface oxidation becomes less pronounced.
1CT7 10"5 10"3 10"1 101 103 pressure, [torr]
Fig. 1. Diamond surface nanoablation rate versus atmospheric pressure.
References
[1] Kononenko, V. V., Gololobov, V. M., Komlenok, M. S., Konov, V. I., "Nonlinear photooxidation of
diamond surface exposed to femtosecond laser pulses." Laser Physics Letters 2015, 12(9): 5. [2.] Kononenko, V. V., Vlasov, I. I., Gololobov, V. M., Kononenko, T. V., Semenov, T. A., Khomich, A. A., Shershulin, V. A., Krivobok, V. S., Konov, V. I., "Nitrogen-vacancy defects in diamond produced by femtosecond laser nanoablation technique." Applied Physics Letters 2017, 111(8): 4.
