Sergei I. Dolgaev

Fast etching of sapphire by a visible range quasi-cw laser radiation

Abstract Experimental results are presented on laser-assisted etching of sapphire by a copper vapour laser radiation (wavelength 510 nm, pulse duration 10 ns, repetition rate 8 kHz, energy density ∼ 10 J/cm2). The etching is carried out under the laser irradiation through the sapphire substrate of the interface sapphire/absorbing liquid. The self-modulation of the groove depth is observed in a certain range of scanning velocities of laser beam. A qualitative model of the etching process is proposed where the maximal etching depth per pulse is limited by the thermal diffusion length of sapphire during the laser pulse. The corresponding etching rate of 0.3 μm/pulse (∼ 2 mm/s) is observed experimentally. The etched areas of sapphire show the ability to reduce Cu from the electroless plating solution. Area-selective Cu metallization of the etched grooves, via- and blind holes is reported with adherence up to 18 N/mm2.

Deposition of nanostructured Cr2O3 on amorphous substrates under laser irradiation of the solid-liquid interface

Abstract The deposition of epitaxial films of Cr 2 O 3 , Fe 2 O 3 , and MnO 2 under laser irradiation of the interface sapphire-absorbing liquid has been reported recently. In similar experimental conditions, laser irradiation of the amorphous solid–liquid interface results in deposition of a polycrystalline film. In the present paper, the deposition of Cr 2 O 3 on a glass substrate induced by radiation of a Cu vapor laser is studied. Irradiation of the interface glass–aqueous solution of CrO 3 at fluence of 2–5 J/cm 2 at λ =510.6 nm results in the deposition of Cr 2 O 3 which consists of oriented nanoclusters with size of 8–20 nm. The subsequent chemical etching of the glass results in a free-standing film of Cr 2 O 3 with lateral dimensions of several mm 2 and 30–50 μm thick. The mathematical model of the deposition process is considered based on the semi-analytical solution of the non-stationary heat diffusion equation for a gaussian profile of laser beam. It is shown that during a ns laser pulse the maximum of the temperature shifts from the interface towards the absorbing liquid. The results of calculations are qualitatively consistent with experimental data on the dependence of the thickness of Cr 2 O 3 deposit on the heat diffusion coefficient of a solid substrate.