Photo-oxidation and the Absence of Photodarkening in Ge2Sb2Te5 Phase Change Material

2006 ◽  
Vol 918 ◽  
Author(s):  
Bong-Sub Lee ◽  
Ying Xiao ◽  
Stephen G. Bishop ◽  
John R. Abelson ◽  
Simone Raoux ◽  
...  
Keyword(s):  
Phase Change ◽  
Secondary Ion Mass Spectrometry ◽  
Free Carrier ◽  
Carrier Generation ◽  
Photo Oxidation ◽  
Optical Irradiation ◽  
The Mean ◽  
Change Material ◽  
Secondary Ion ◽  
Change Memory

AbstractGe2Sb2Te5 is under intense investigation for phase-change memory devices, including rewriteable DVDs where optical illumination is used to switch between the glassy and crystalline states. We investigate the influence of optical irradiation on amorphous phase. Many chalcogenides display photo-oxidation, photodarkening or photo-bleaching, but little has been reported on the Ge-Sb-Te system. Using spectroscopic ellipsometry (SE) and secondary ion mass spectrometry, we determine that the samples have a strong tendency to photo-oxidize; if this is not accounted for, then the analysis of SE data appears to show photodarkening. Other authors recently reported photodarkening in nonstoichiometric GexSb20-xTe80 [Pamukchieva et al., Proc. SPIE 5581, 608 (2004); Pamukchieva et al., J. Optoelectron. Adv. Mater 7, 1277 (2005)], but our analysis suggests that the changes were also the result of photo-oxidation. The oxide has lower value of (n, k) than Ge2Sb2Te5, and can be etched by hydrofluoric acid or water. The photo-oxidation is presumably the result of free carrier generation in the Ge2Sb2Te5. Our observation of negligible photodarkening is consistent with previous works that found less photodarkening in tellurides compared with selenides or sulfides, and that an increase in the mean coordination number, here by Ge addition, further reduces the photodarkening effect.

Si2Sb2Te6Phase Change Material for Low-Power Phase Change Memory Application

2009 ◽  
Vol 2 (9) ◽  
pp. 091401 ◽  
Author(s):  
Xilin Zhou ◽  
Liangcai Wu ◽  
Zhitang Song ◽  
Feng Rao ◽  
Bo Liu ◽  
...  
Keyword(s):  
Low Power ◽  
Phase Change ◽  
Phase Change Memory ◽  
Change Material ◽  
Change Memory

Effect of Aerogel Incorporation in PCM-Containing Thermal Liner of Firefighting Garment

2018 ◽  
Vol 36 (3) ◽  
pp. 151-164 ◽  
Author(s):  
Abu Shaid ◽  
Lijing Wang ◽  
Stanley M. Fergusson ◽  
Rajiv Padhye
Keyword(s):  
Thermal Properties ◽  
Thermal Resistance ◽  
Heat Resistance ◽  
Phase Change ◽  
Phase Change Material ◽  
Protective Clothing ◽  
Ignition Time ◽  
Current Case ◽  
The Mean ◽  
Change Material

Phase change material (PCM) in firefighting garment enhances protection and comfort. Wearing a protective clothing containing PCM, while fighting the fire, is a direct risk to the wearer as most PCMs used are flammable. This article reports a solution by using aerogel. Thermal liner fabric was treated with PCM and/or aerogel and then their thermal properties were analyzed. It has been found that the mean ignition time of PCM-containing thermal liner is around 3.3 s in current case while this value significantly increased to 5.5 s when the combination of aerogel and PCM was used. Moreover, the weight of the liner fabric with aerogel decreased in comparison to PCM-containing liner. Aerogel also slowed down the spreading of flame in PCM-containing fabric. Aerogel–coated liner showed superior heat resistance and the combination of aerogel with PCM increased the thermal resistance of PCM-containing liner.

Transient Performance of a Finned PCM Heat Sink

2005 ◽  
Author(s):  
V. Shatikian ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Phase Change ◽  
Melting Temperature ◽  
Phase Change Material ◽  
Heat Sink ◽  
Geometrical Parameters ◽  
Transient Performance ◽  
The Mean ◽  
Liquid States ◽  
Fin Thickness ◽  
Change Material

The present study explores numerically the transient performance of a heat sink based on a phase change material (PCM), during the process of melting. Heat is transferred to the sink through its horizontal base, to which vertical fins made of aluminum are attached. The phase change material is stored between the fins. Its properties, including the melting temperature, latent and sensible specific heat, thermal conductivity and density in solid and liquid states, are based on a commercially available paraffin wax. A parametric investigation is performed for melting in a relatively small system, 10mm high, where the fin thickness is 1.2mm, and the distance between the fins varies from 2mm to 8mm. The temperature of the base varies from 12°C to 24°C above the mean melting temperature of the PCM. Transient numerical simulations are performed, yielding temperature evolution in the fins and the PCM. The computational results show how the transient phase-change process, expressed in terms of the volume melt fraction of the PCM, depends on the thermal and geometrical parameters of the system, which relate to the temperature difference between the base and the mean melting temperature, and to the thickness of the PCM layer.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

Secondary ion mass spectrometry study of photorefractive-damage-resistant locally Er/Mg-doped near-stoichiometric Ti:Mg:Er:LiNbO3 strip waveguides

2010 ◽  
Vol 25 (9) ◽  
pp. 1822-1832 ◽  
Author(s):  
De-Long Zhang ◽  
Ping-Rang Hua ◽  
Li Qi ◽  
Bei Chen ◽  
Edwin Yue-Bun Pun
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Gaussian Function ◽  
Waveguide Layer ◽  
Lateral Direction ◽  
Er Doping ◽  
Depth Direction ◽  
Ion Mass Spectrometry ◽  
The Mean ◽  
Secondary Ion

Secondary-ion mass spectrometry (SIMS) was used to study the profile characteristics and diffusion properties of Mg, Ti, and Er ions in photorefractive-damage-resistant locally Er/Mg-diffused near-stoichiometric (NS) Ti:Mg:Er:LiNbO3 strip waveguides fabricated on two Z-cut initially congruent, undoped LiNbO3 substrates in sequence by local Er doping at 1100 °C or 1130 °C in air, Mg/Ti pre-diffusion at 1100 °C in wet O2, and post Li-rich vapor transport equilibration (VTE) treatment at 1100 °C. For comparison, a SIMS study was also carried out on the waveguides fabricated without the post-VTE treatment. In order to compensate for the refractive index decrease arising from both the Mg doping and the post-VTE treatment, and hence to get a positive net index increment profile in the Ti-diffused layer, a thicker Ti-film of around 170 nm was coated. Nevertheless, SIMS results show that the Ti diffusion reservoir, as well as the Er and Mg reservoirs, was exhausted. From the SIMS profiles, characteristic diffusion parameters such as the 1/e diffusion width (for Ti only) and depth, diffusivity, and surface concentration of the Mg, Ti, and Er ions are obtained. It is interesting that the Mg distribution in the NS waveguide layer is desirably homogeneous with a concentration [(1.7–2.0) ± 0.3 mol%] higher than the optical damage concentration threshold. The Ti profile follows a sum of two error functions along the lateral direction of NS waveguides with a diffusion width of (12–13) ± 0.5 μm, and a Gaussian function in the depth direction with a 1/e depth of (5.1–6.0) ± 0.2 μm. The Er profile follows also a Gaussian function with a 1/e depth of (3.7–4.4) ± 0.3 μm. In the NS waveguide layer, the mean diffusivity is (7.1 ± 2.2) to (8.3 ± 2.8) μm2/h for Mg, (3.5 ± 0.3) to (4.5 ± 0.4) μm2/h in the lateral direction and (0.54 ± 0.04) to (1.13 ± 0.08) μm2/h in the depth direction for Ti, and (4.1 ± 0.4) to (5.5 ± 0.5) × 10−2 μm2/h for Er. The effects of Li outward diffusion in the initial Er doping procedure, and the Mg codiffusion and post-VTE treatment on the mean Mg, Ti, and Er diffusivities are discussed in comparison with the previously reported results on single Mg, Ti, or Er diffusion and Mg/Ti codiffusion in a pure or homogeneously MgO-doped congruent LiNbO3 crystal. Finally, the keys to the success of the fabrication procedure adopted are discussed.

Evidence for Exchange Between Free and Deep Hydrogen (Deuterium) During Diffusion

1995 ◽  
Vol 377 ◽  
Author(s):  
Howard M. Branz ◽  
Sally Asher ◽  
Yueqin Xu ◽  
Mathieu Kemp
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Emission Rate ◽  
Exchange Process ◽  
Interior Layer ◽  
Exchange Processes ◽  
Hydrogen Deuterium ◽  
The Mean ◽  
Hydrogenated Amorphous ◽  
Secondary Ion ◽  
Tracer Experiments

ABSTRACTWe do not observe any immobile deuterium in secondary ion mass spectrometry D profiles taken after long anneals of hydrogenated amorphous silicon sandwich structures with a thin deuterated interior layer. This suggests that a single deep H level (∼1.4 eV deep) controls H diffusion. On its face, our result contradicts nuclear magnetic resonance and H effusion measurements that show about 30% of H in a-Si:H is “isolated” and deeply bound (∼ 2.1 eV deep). We reconcile our experimental results with the existence of isolated deep H by assuming there is a low-barrier (<< 1.4 eV) exchange process between free H and deep D. In tracer experiments, exchange has the effect of increasing the apparent emission rate of the deep D to nearly that of the shallowest trapped H. We solve for the D profiles and confirm that a deep-trapped D component is consistent with our D tracer profiles if and only if exchange processes are important. We also find that the mean distance D travels before retrapping (100–200Å) is determined by an exchange process of free D with trapped H.

Polyamorphism in K2Sb8Se13 for multi-level phase-change memory

2020 ◽  
Vol 8 (19) ◽  
pp. 6364-6369 ◽  
Author(s):  
Meng Xu ◽  
Chong Qiao ◽  
Kan-Hao Xue ◽  
Hao Tong ◽  
Xiaomin Cheng ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Data Storage ◽  
Phase Change Memory ◽  
State Data ◽  
Amorphous Phases ◽  
Multi Level ◽  
Change Material ◽  
Change Memory

A novel phase-change material K2Sb8Se13 with two amorphous phases was thoroughly investigated for multi-state data storage.

Nitrogen-doped Sb-rich Si–Sb–Te phase-change material for high-performance phase-change memory

2013 ◽  
Vol 61 (19) ◽  
pp. 7324-7333 ◽  
Author(s):  
Xilin Zhou ◽  
Liangcai Wu ◽  
Zhitang Song ◽  
Yan Cheng ◽  
Feng Rao ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
High Performance ◽  
Phase Change Memory ◽  
Nitrogen Doped ◽  
Change Material ◽  
Change Memory

Interface Characterization of Metals and Metal-nitrides to Phase Change Materials

2011 ◽  
Vol 1337 ◽  
Author(s):  
Deepu Roy ◽  
Dirk J. Gravesteijn ◽  
Rob A. M. Wolters
Keyword(s):  
Contact Resistance ◽  
Phase Change ◽  
Phase Change Materials ◽  
Electrode Materials ◽  
Interfacial Contact ◽  
Interfacial Contact Resistance ◽  
Change Material ◽  
Change Memory ◽  
Selection Of

ABSTRACTWe have investigated the interfacial contact properties of the CMOS compatible electrode materials W, TiW, Ta, TaN and TiN to doped-Sb2Te phase change material (PCM). This interface is characterized both in the amorphous and in the crystalline state of the doped-Sb2Te. The electrical nature of the interface is characterized by contact resistance measurements and is expressed in terms of specific interfacial contact resistance (ρC). These measurements are performed on four-terminal Kelvin Resistor test structures. Knowledge of the ρC is useful for selection of the electrode in the integration and optimization of the phase change memory cells.

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