10-nm silicon nanostructures for phase-change UV-readable optical data storage

Achieving state-of-the-art optical data storage requires raising device capacity well above commercial standards. This requires media structured at a much smaller scale and enabling readout at a shorter wavelength. Current CDs, DVDs and Blu-rays are read with visible light, and are based on metallic reflection gratings and phase-change recording layers structured at the few-hundred-nm scale. Herein, we introduce 10-nm structured silicon as a promising UV-readable data storage platform. Recording on it harnesses the amorphous-to-crystalline phase-change of silicon, the two phases presenting well-constrasted UV optical properties. Furthermore, the phase-change contrast is strongly enhanced in the Vacuum UV thanks to the distinct interband plasmon resonances of the amorphous and crystalline nanostructures, which have an epsilon-near-zero and surface plasmonic character, respectively. Silicon nanogratings with a 10 nm width and a 20 nm period resonate near the wavelength of 120 nm, at which phase-change induces a 600% maximum optical transmittance contrast. This paves the way toward UV-readable data storage platforms with a 10 to 100 times increased data density, which could be implemented by harnessing the well-established silicon nanotechnology.