Phase change recording using a scanning near-field optical microscope

Abstract

The formation and observation, with reflected light, of 60-nm-diam phase-changed domains in a thin GeSbTe film using a scanning near-field optical microscope with a 785 nm wavelength laser diode is demonstrated. The dependence of the domain size on incident laser power was obtained, and the size changed from 150 to 60 nm in diameter with incident power of 8.4–7.3 mW in the probe. At the threshold power of 7.3 mW, the film temperature rose to around 180 °C to partially phase change the local area of the film from amorphous to crystalline. A detected reflectivity increase due to phase change in the formed domain was 8%–2%. The observing (reading) was performed with an incident laser power of 0.2 mW, which corresponds to 10−2–10−3 times less than in a magneto-optical recording. The incident laser power shows that the phase change reading using the reflection scanning near-field optical microscope has the potential to read the recorded bit at a speed over 10 MHz.

Nanosilicon dot arrays with a bit pitch and a track pitch of 25nm formed by electron-beam drawing and reactive ion etching for 1Tbit∕in.2 storage

“…This result promises to open the way toward 1 Tbit/ in. 2 Available magnetic recording density is rising at a rate of 60% per year. High-end magnetic storage media with a recording density of over 100 Gbit/ in.…”

“…These recording media were, however, very far from the areal density of 1 Tbit/ in. 2 , because the pitches were too large. In this letter, we describe the ultrahigh-packed nanofabrication of a 1 Tbit/ in.…”

“…High-end magnetic storage media with a recording density of over 100 Gbit/ in. 2 have already been commercialized. In optical recording, the Blu-ray disk and the high-definition digital versatile disk ͑DVD͒ with a capacity of 25 Gbytes have also been developed.…”

“…However, there are many technical issues to be solved for recording densities as high as 1 Tbit/ in. 2 . A breakthrough is required for future recording systems.…”

“…2 , we carried out ͑1͒ a very fine EB exposure with a fine probe and a high probe current; we also prepared ͑2͒ a thin resist layer to prevent the spread of incident electron scattering; finally, we designed ͑3͒ a highly packed pattern with a hexagonal or centered rectangular lattice structure such as cross stitch to prevent proximity effects. Item ͑2͒ refers to a thin resist layer which requires an increased acceleration voltage for precise EB drawing.…”