Modeling of laser pulsed heating and quenching in optical data storage media

Abstract

In order for rewritable optical data storage to compete with other storage technologies, it is crucial to increase the data transfer rate and storage capacity. Near-field recording should enable considerable progress in these areas, however, currently available near-field light sources are limited by their low output powers. This puts severe constraints on the thermal properties of the phase change media. This article addresses how rewritable optical data storage media can meet data transfer rate and storage capacity requirements. In particular, the required laser power for writing and erasing submicron ''bits'' is calculated. It is shown using modeling how the power and the write and erase times depend on the structure and thermal properties of the media, as well as on the crystallization kinetics of the recording layer. Guidelines for media optimization and areas that presently pose the most serious limitations are presented.

A slope-theory approach to electrical probe recording on phase-change media

“…Simplified analytical models and more detailed numerical simulations of laser heating in phase-change optical storage disks have indicated that the temperature rise in the phase-change layer involves transient and steady-state stages with a nonconstant heating rate. 27,28 However, at small times after applying the heating source and near the transition or crystallization temperature where interest is focused here, the temperature evolution is almost linear with a constant heating rate 27 and can thus be described by ͑18͒ in this region. Moreover, using this linear approximation allows comparison with ramped electrical conductivity versus temperature measurements that are typically used to study and characterize phase-change recording media.…”

Preparation and characterization of laser-irradiation induced amorphous for Ge2Sb2Te5 phase-change materials

“…Therefore, the laser beam mainly heats the layer of GST films with 20 nm thickness. According to the heat capacities and thermal conductivities of GST (c = 1.3 J cm 3 K 1 , and K = 0.2 W m 1 K 1 ), carbon (c = 1.86 J cm 3 K 1 and K = 3.5 W m 1 K 1 ), and aluminum (c = 2.45 J cm 3 K 1 and K = 237.0 W m 1 K 1 ) [6,20,21], the Al films with 40 nm thickness could increase the heat capacity by four times and the thermal conductivity by sixtyfive times. …”

“…In the rewritable commercial Blu-ray discs fabricated with Ge 2 Sb 2 Te 5 (GST) materials, the writing/erasing process occurs with reversible phase changes between the meta-stable crystalline phase [4] and the laser-irradiation induced amorphous (L-a) phase driven by laser pulses of different power and duration time [6]. But the basic scientific questions, such as the local atomic structure of L-a phase and the mechanism of phase-change, have not been finally resolved and have given rise to much controversy [7][8][9][10][11].…”

“…Due to the difficulty of preparing sufficient amount of L-a samples for X-ray diffraction (XRD) and neutron diffraction (ND) experiments, most investigations on local structure were performed by ab initio molecular dynamics calculation [8][9][10][11]. At the meantime, the most investigated L-a GST phases [1, 6,[12][13][14][15][16][17] were in fact prepared on hard substrates and unsuitable for collecting diffraction data. On the other hand, the local structure of L-a GST phase is probably different from the as-prepared amorphous GST phase (S-a) deposited by magnetron sputtering methods [18,19].…”

Explanation of programming distributions in phase-change memory arrays based on crystallization time statistics

“…The critical set current I Ã SET decreases for increasing t SET . In fact, to provide the same crystalline fraction with a longer set pulse, a lower temperature will be required [12,13], corresponding to a lower current inducing Joule heating in the amorphous region of the cell. Fig.…”