Phase-Change Kinetics of Bi–Fe–(N) Layer for High-Speed Write-Once Optical Recording

Abstract

In this work, we present the phase-change kinetics of Bi–Fe–(N) layers for write-once optical recording. In situ reflectivity measurement indicated that the phase-change temperature (Tx) of the Bi–Fe–(N) layers is strongly related to the heating rate. The Tx's were about 170 °C at low heating rates and approached the melting point of the Bi phase (i.e., 271.4 °C) at high rate of heating provided by laser heating. For a 100-nm-thick Bi–Fe–(N) layer, Kissinger's analysis showed that the activation energy of phase transition (Ea) = 1.24 eV, while the analysis of isothermal phase transition in terms of the Johnson–Mehl–Avrami (JMA) theory showed that the average Avrami exponent (m) = 2.2 and the appropriate activation energy (ΔH) = 5.15 eV. With the aid of X-ray diffraction (XRD) analysis, a two-dimensional phase transition behavior in the Bi–Fe–(N) layers initiated by the melting of the Bi-rich phase was confirmed. For optical disk samples with optimized disk structure and write strategy, the signal properties far exceeding the write-once disk test specifications were achieved. Satisfactory signal properties indicated that the Bi–Fe–(N) system is a promising alternative for high-speed write-once recording in the Blu-ray era.