Nanometer-sized phase-change recording using a scanning near-field optical microscope with a laser diode

We present for the first time a nanometer-sized phase-change recording using a scanning near-field optical microscope (PC-SNOM recording). The recording experiments were performed with a SNOM using a 785-nm-wavelength semiconductor laser diode, shear force detection for gap control and reflected light detection for observing the domains (reading). The recording media of ZnS . SiO2(20 nm)/GeSbTe(30 nm)/ZnS . SiO2(150 nm)/polycarbonate substrate were used. The writings were done at laser powers of 8.4-7.3 mW in the probe for pulse widths of 5 or 0.5 ms. As a result, we obtained a minimum recorded domain size of 60 nm in diameter. This size shows a potential to achieve an ultrahigh density PC-SNOM recording with about 170 Gb/in(2). A possibility of achieving high speed readout for the future data storage is also discussed.