Advanced Materials

Control over the Crystalline State of Sapphire



Amorphous regions in sapphire with sub-micrometer 3D resolution have been produced at the focus of a single femtosecond laser pulse. Crystalline- to-amorphous and amorphous-to-polycrystalline transitions (crystalline and amorphous regions are marked C and A in the HRTEM image) are induced by single- and multi-pulse irradiation, respectively. The wet-etching selectivity for the amorphous phase is significantly greater than that for the crystalline phase in aqueous HF.

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