ZnS-SiO2 Films Research Articles

Calculations of Absorbed Dose in Heavy-Ion Irradiated Phase-Change Memory Cells

Heavy ion irradiation on phase change memory cell was conducted using Monte Carlo simulations. Absorbed dose in the whole memory cell, as well as in its active layer was assessed. Phase change memory cell was modeled as a sandwiched structure of two TiW electrodes and ZnS-SiO2films as insulators surrounding the active region. The most commonly used phase change material, Ge2Sb2Te5, was used as active layer of the cell. Ionization effects of heavy ion irradiation were investigated for various thicknesses of phase change layer and different ion energies.

Simulation-based calculations of the proton dose in phase change memory cells

Monte Carlo simulations of proton irradiation on phase change memory cells were conducted and the proton dose, in both the whole memory cell and in its active layer, calculated. The memory cell was modeled by a multi-layer stack consisting of two TiW electrodes and ZnS-SiO2 films as insulators surrounding the active region. Materials considered for the active region were Ge2Sb2Te5, AgSbSe2, and Si2Sb2Te5. The effects of exposing phase change memory cells to proton beams were investigated for various thicknesses of phase change materials and different proton energies. Radiation-induced changes in the investigated memory cells are presented, including the accumulation of atomic displacements and the thermal heating of the active region. Possible effects of these changes on cell operation are discussed.

Crystallization Mechanisms of Phase Change (GeSbSn)100−xCox Optical Recording Films

In this study, the (GeSbSn)(100-x0Co(x) films (x = 0-13.3) were deposited on natural oxidized silicon wafer and glass substrate by dc magnetron co-sputtering of GeSbSn and Co targets. The ZnS-SiO2 films were used as protective layers. The thicknesses of the (GeSbSn)(100-x)Co(x) films and protective layer were 100 nm and 30 nm, respectively. We investigated the effects of Co addition on the thermal property, crystallization kinetics, and crystallization mechanism of the GeSbSn recording film. The crystallization temperatures of (GeSbSn)(100-x)Co(x) films were decreased with Co content. It was found that the activation energy of the (GeSbSn)(100-x)Co(x) films will decrease from 1.53 eV to 0.55 eV as Co content increased from 0 at.% to 13.3 at.%.

Characteristics of In-Ge-Sb-Sn-Te Thin Film Used for Phase Change Optical Recording Media

The In10GexSb52-xSn23Te15 films (x = 2, 5, and 9) were deposited on nature oxidized silicon wafer and glass substrate by dc magnetron sputtering. The ZnS-SiO2 films were used as protective layers. The thickness of the In10GexSb52-xSn23Te15 film is 20 nm. We have studied the crystallization kinetics, structural and optical properties of the In10GexSb52-xSn23Te15 (x = 2, 5, and 9) recording films. It is found that the crystallization temperature of the film is increased with increasing Ge content. The optical contrasts of In10GexSb52-xSn23Te15 films with x = 2~9 are all higher than 30 % at a wavelength of 405 nm, showing that the films are suitable for blue laser optical recording media application.

Crystallization Mechanism of Si/Cu<sub>100-x</sub>Zr<sub>x</sub> Bilayer Film for Write-Once Blue Laser Optical Recording Media

Si/Cu100xZrx (x= 0~38.1) bilayer recording thin films were deposited on nature oxidized silicon wafer, and glass substrate by magnetron sputtering. The ZnS-SiO2 films were used as protective layers. We have studied the thermal property, optical property, and crystallization mechanism of the Si/Cu100-xZrx bilayer thin films. The optical contrasts of the Si/Cu100-xZrx (x= 0~38.1) bilayer films under 405 nm wavelength are all larger than 15%, and it reaches a high value of 40%, as x= 38.1. This indicates that the Si/Cu100-xZrx (x= 0~38.1) bilayer films are suitable for blue laser optical recording.

Microstructure and Crystallization Mechanism of (GeSbSn)<sub>100-x</sub>Fe<sub>x</sub> Phase Change Optical Recording Films

The (GeSbSn)100-xFex films (x = 0 ~ 12.9) were deposited on nature oxidized silicon wafer, and glass substrate by dc magnetron sputtering. The ZnS-SiO2 films were used as protective layers. The thickness of the (GeSbSn)100-xFex film is 100 nm. We have studied the effects of Fe addition on the crystallization kinetics, and microstructures of the GeSbSn recording film. The crystallization temperatures of (GeSbSn)100-xFex films with x = 0, 7.1, 9.1, and 12.9 were found to be 225 °C, 198 °C, 167 °C, and 165 °C, respectively. The crystallization activation energies of (GeSbSn)100-xFex films with x = 0, 7.1, 9.1, and 12.9 are about 1.74 eV, 1.15 eV, 0.81 eV, and 0.52 eV, respectively.

GeCu/Si Bilayer Thin Film for Write-Once Blue Laser Optical Recording Media

GeCu(6 nm)/Si(6 nm) bilayer recording thin film was deposited on nature oxidized silicon wafer and polycarbonate substrate by magnetron sputtering. The ZnS-SiO2 films were used as protective layers. We have studied the thermal property, crystallization mechanism, and recording characteristics of the GeCu/Si bilayer thin film. Thermal analysis shows that the GeCu/Si bilayer film has two reflectivity changes with the temperature ranges, 120 °C ~ 165 °C and 310 °C ~ 340 °C. The results of dynamic tests show that the optimum jitter values at recording speeds of 1X and 4X are 5.8% and 5.9%, respectively. The modulations at 1X and 4X recording speeds are all larger than 0.4.

Effect of Dielectric Material Films on Crystallization Characteristics of Ge2Sb2Te5 Phase-Change Memory Film

Reduction of the film thickness of phase-change film and the adoption of GeN- or ZrO2-based dielectric films are both effective in achieving good thermal stability in phase-change optical disks. It was experimentally confirmed that, at a heating rate of 10 °C/min, the crystallization temperature Tx of the Ge2Sb2Te5 amorphous film when sandwiched by ZnS–SiO2 films markedly increases from 162 to 197 °C, while the thickness of the Ge2Sb2Te5 film decreases from 10 to 3 nm. Tx also slightly increases when ZnS–SiO2 films are substituted for GeN-based films (from 162 to 165 °C) and ZrO2-based films (from 162 to 167 °C). At the same time, the activation energy of crystallization is 2.4 eV for both GeN- and ZrO2-based films, and is higher than 2.2 eV for ZnS–SiO2 films.

Real-Time Growth Control of Ge–Sb–Te Multilayer Film as Optical Recording Media by In Situ Ellipsometry

Using an in situ ellipsometer, we monitored the thin film growth curve of optical recording media in real time. Utilizing the complex refractive indices of Ge2Sb2Te5 and ZnS–SiO2 obtained from the analysis of spectroscopic ellipsometry data, we calculated the growth curves of ellipsometric constants vs thickness. By comparing the calculated growth curve of ellipsometric constants with the measured one, and by analyzing the effect of the density variation of the Ge2Sb2Te5 recording layer on ellipsometric constants, we precisely monitored the growth rate of Ge2Sb2Te5 and ZnS–SiO2 films, respectively, and eventually controlled the whole growth process of a multilayer sample made of Ge2Sb2Te5 and ZnS–SiO2 films. The accurate thickness control using in situ ellipsometry was verified through the analysis of the deposited multilayer sample using an ex situ spectroscopic ellipsometer.

Super Resolution Read Only Memory Disc Using Super-Resolution Near-Field Structure Technology

Super resolution near-field structure (super-RENS) technology is one of the promising technologies for a sub-terabyte optical storage of around 200 GB capacity. We confirmed the possibility of super-RENS read only memory (ROM) media with multilayer structure using the combination of the PtOx, AgInSbTe, ZnS-SiO2 films. The carrier to noise ratio (CNR) and readout cyclability was measured for the super-RENS ROM disc in both the red laser and the blue laser systems.