We demonstrate a simple way to fabricate amorphous micro-rings in crystalline silicon using
direct laser writing. This method is based on the fact that the phase of a thin surface layer
can be changed into the amorphous phase by irradiation with a few ultrashort laser pulses
(800 nm wavelength and 100 fs duration). Surface-depressed amorphous rings with a
central crystalline disk can be fabricated without the need for beam shaping, featuring
attractive optical, topographical, and electrical properties. The underlying formation …