Stress Buildup Upon Crystallization of GeTe Thin Films: Curvature Measurements and Modelling

Phase change materials are attractive materials for non-volatile memories because of their ability to switch reversibly between an amorphous and a crystal phase. The volume change upon crystallization induces mechanical stress that needs to be understood and controlled. In this work, we monitor stress evolution during crystallization in thin GeTe films capped with SiOx, using optical curvature measurements. A 150 MPa tensile stress buildup is measured when the 100 nm thick film crystallizes. Stress evolution is a result of viscosity increase with time and a tentative model is proposed that renders qualitatively the observed features.

Download Full-text

Multilayer SnSb4–SbSe Thin Films for Phase Change Materials Possessing Ultrafast Phase Change Speed and Enhanced Stability

ACS Applied Materials & Interfaces ◽

10.1021/acsami.7b06533 ◽

2017 ◽

Vol 9 (32) ◽

pp. 27004-27013 ◽

Cited By ~ 10

Author(s):

Ruirui Liu ◽

Xiao Zhou ◽

Jiwei Zhai ◽

Jun Song ◽

Pengzhi Wu ◽

...

Keyword(s):

Thin Films ◽

Phase Change ◽

Phase Change Materials ◽

Enhanced Stability

Download Full-text

Laser Synthesis of Sn-Ge-Sb-Te Phase Change Materials

MRS Proceedings ◽

10.1557/proc-0918-h08-03 ◽

2006 ◽

Vol 918 ◽

Author(s):

Wendong Song ◽

L.P. Shi ◽

X.S. Miao ◽

T.C. Chong

Keyword(s):

Thin Films ◽

Phase Change ◽

Crystallization Temperature ◽

Photoelectron Spectroscopy ◽

Phase Change Materials ◽

Frequency Factor ◽

Ramp Rate ◽

Laser Synthesis ◽

Si Substrates ◽

Change Temperature

AbstractSn-doped Ge-Sb-Te films on Si substrates were prepared by laser synthesis at the different growth temperatures. The compositions of Sn-doped Ge-Sb-Te films were analysized by X-ray photoelectron spectroscopy. The crystal structures of Sn-doped Ge-Sb-Te thin films with a Sn content of less than 30 at% are close to Ge2Sb2Te5. The crystallization behaviors of Sn-doped Ge-Sb-Te films were analyzed by self-developed phase change temperature tester. The crystallization temperatures of Sn4.3Ge32.9Sb28.1Te34.6, Sn9.8Ge20.3Sb28.4Te41.5 and Sn18.8Ge19.5Sb25.3Te36.4 are 141.5, 137.3 and 135.0 °C at a ramp rate of 20 °C/min, respectively. Doping Sn into Ge-Sb-Te will result in a decrease of crystallization temperature. It was also found that crystallization temperature increases with an increase of ramp rate for a phase change material. The activity energy Ea and frequency factor ¦Ô for Sn9.8Ge20.3Sb28.4Te41.5 thin films are 2.42 eV and 1.7 × 1026 Hz, respectively. The crystallization speed of Sn-doped Ge-Sb-Te is estimated to be faster than Ge2Sb2Te5.

Download Full-text

Melting of Phase Change Materials With Volume Change in Metal Foams

Journal of Heat Transfer ◽

10.1115/1.4000747 ◽

2010 ◽

Vol 132 (6) ◽

Cited By ~ 28

Author(s):

Zhen Yang ◽

Suresh V. Garimella

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Phase Change ◽

Volume Change ◽

Phase Change Materials ◽

Metal Foam ◽

Melting Process ◽

Metal Foams ◽

Volume Shrinkage ◽

Two Temperature

Melting of phase change materials (PCMs) embedded in metal foams is investigated. The two-temperature model developed accounts for volume change in the PCM upon melting. Volume-averaged mass and momentum equations are solved, with the Brinkman–Forchheimer extension to Darcy’s law employed to model the porous-medium resistance. Local thermal equilibrium does not hold due to the large difference in thermal diffusivity between the metal foam and the PCM. Therefore, a two-temperature approach is adopted, with the heat transfer between the metal foam and the PCM being coupled by means of an interstitial Nusselt number. The enthalpy method is applied to account for phase change. The governing equations are solved using a finite-volume approach. Effects of volume shrinkage/expansion are considered for different interstitial heat transfer rates between the foam and PCM. The detailed behavior of the melting region as a function of buoyancy-driven convection and interstitial Nusselt number is analyzed. For strong interstitial heat transfer, the melting region is significantly reduced in extent and the melting process is greatly enhanced as is heat transfer from the wall; the converse applies for weak interstitial heat transfer. The melting process at a low interstitial Nusselt number is significantly influenced by melt convection, while the behavior is dominated by conduction at high interstitial Nusselt numbers. Volume shrinkage/expansion due to phase change induces an added flow, which affects the PCM melting rate.

Download Full-text

Interdiffusion and Stress Evolution During Solid-State Amorphization in Ni-Hf Thin-Film Diffusion Couples

MRS Proceedings ◽

10.1557/proc-400-143 ◽

1995 ◽

Vol 400 ◽

Cited By ~ 1

Author(s):

M. Atzmon ◽

W. S. L. Boyer

Keyword(s):

Solid State ◽

Tensile Stress ◽

Diffusion Couple ◽

Rutherford Backscattering Spectrometry ◽

Amorphous Layer ◽

Stress Evolution ◽

Curvature Measurements ◽

Thin Film Diffusion ◽

Stress Variations ◽

State Amorphization

AbstractUsing a combination of x-ray diffraction and curvature measurements, the stress evolution during solid-state amorphization in a Ni-Hf diffusion couple has been monitored. In contrast to the Co-Hf system, no dissolution of Ni in Hf is observed. During interdiffusion, the growing amorphous layer develops a large tensile stress, which subsequently relaxes by creep. Irradiation of the diffusion couple leads to an increase in tensile stress, and a further increase following a subsequent anneal. Composition measurements by Rutherford backscattering spectrometry indicate absence of an effect of the stress variations on the effective interdiffusion coefficient.

Download Full-text

Structural change with the resistance drift phenomenon in amorphous GeTe phase change materials’ thin films

Journal of Physics D Applied Physics ◽

10.1088/0022-3727/49/3/035305 ◽

2015 ◽

Vol 49 (3) ◽

pp. 035305 ◽

Cited By ~ 15

Author(s):

Pierre Noé ◽

Chiara Sabbione ◽

Niccolo Castellani ◽

Guillaume Veux ◽

Gabriele Navarro ◽

...

Keyword(s):

Thin Films ◽

Structural Change ◽

Phase Change ◽

Phase Change Materials

Download Full-text

Enhanced temperature stability and exceptionally high electrical contrast of selenium substituted Ge2Sb2Te5 phase change materials

RSC Advances ◽

10.1039/c7ra01140g ◽

2017 ◽

Vol 7 (28) ◽

pp. 17164-17172 ◽

Cited By ~ 13

Author(s):

Christine Koch ◽

Anna-Lena Hansen ◽

Torben Dankwort ◽

Gerrit Schienke ◽

Melf Paulsen ◽

...

Keyword(s):

Thin Films ◽

Phase Change ◽

Phase Change Materials ◽

Temperature Stability ◽

Crystalline Phases ◽

Compound Ii

Compared to the pure telluride Ge2Sb2Te5, Ge2Sb2Te4Se (I) and Ge2Sb2Te2Se3 (II) thin films reveal an exceptionally large electrical contrast (increased by factor 100 for compound II) between the amorphous and crystalline phases.

Download Full-text

Thickness-dependent Crystallization Behavior of Phase Change Materials

MRS Proceedings ◽

10.1557/proc-1072-g05-02 ◽

2008 ◽

Vol 1072 ◽

Cited By ~ 4

Author(s):

Simone Raoux ◽

Jean L. Jordan-Sweet ◽

Andrew J. Kellock

Keyword(s):

Thin Films ◽

Film Thickness ◽

Phase Change ◽

Crystallization Behavior ◽

Phase Change Materials ◽

Random Access ◽

X Ray Diffraction ◽

Time Resolved ◽

Future Technology ◽

Technology Nodes

ABSTRACTWe have investigated the crystallization behavior of phase change materials as a function of their thickness. Thin films of variable thickness between 1 and 50nm of the phase change materials Ge2Sb2Te5 (GST), N-doped GST (N-GST), Ge15Sb85 (GeSb), Sb2Te, and Ag and In doped Sb2Te (AIST) were deposited by magnetron sputtering, and capped in situ by a 10nm thick Al2O3 film to prevent oxidation. The crystallization behavior of the films was studied using time-resolved X-ray diffraction. For each material we observed a constant crystallization temperature Tx that was comparable to bulk values for films thicker than 10 nm, and an increased Tx when the film thickness was reduced below 10 nm. The thinnest films that showed XRD peaks were 2 nm for GST and N-GST, 1.5 nm for Sb2Te and AgIn-Sb2Te, and 1.3 nm for GeSb. The observed increase in the phase transition temperature with reduced film thickness and the fact that very thin films still show clear phase change properties are indications that Phase Change Random Access Memory technology can be scaled down to several future technology nodes.

Download Full-text

Evaluation of volume change in phase change materials during their phase transition

Journal of Energy Storage ◽

10.1016/j.est.2020.101206 ◽

2020 ◽

Vol 28 ◽

pp. 101206 ◽

Cited By ~ 6

Author(s):

Luisa F. Cabeza ◽

Gabriel Zsembinszki ◽

Marc Martín

Keyword(s):

Phase Transition ◽

Phase Change ◽

Volume Change ◽

Phase Change Materials

Download Full-text

Crystallization process and thermal stability of Ge1Cu2Te3 amorphous thin films for use as phase change materials

Acta Materialia ◽

10.1016/j.actamat.2011.10.048 ◽

2012 ◽

Vol 60 (3) ◽

pp. 872-880 ◽

Cited By ~ 52

Author(s):

Y. Sutou ◽

T. Kamada ◽

M. Sumiya ◽

Y. Saito ◽

J. Koike

Keyword(s):

Thin Films ◽

Thermal Stability ◽

Phase Change ◽

Phase Change Materials ◽

Crystallization Process ◽

Amorphous Thin Films ◽

Thermal Stability Of

Download Full-text

Thermal oxidation mechanism and stress evolution in Ta thin films

Journal of Materials Research ◽

10.1557/jmr.2010.0157 ◽

2010 ◽

Vol 25 (6) ◽

pp. 1080-1086 ◽

Cited By ~ 9

Author(s):

Yusung Jin ◽

Jae Yong Song ◽

Soo-Hwan Jeong ◽

Jeong Won Kim ◽

Tae Geol Lee ◽

...

Keyword(s):

Thin Films ◽

Compressive Stress ◽

Oxidation Mechanism ◽

Ex Situ ◽

Heating Process ◽

Fast Diffusion ◽

Stress Evolution ◽

Compressive Stresses ◽

Layered Formation ◽

Curvature Measurements

Oxidation-induced stress evolutions in Ta thin films were investigated using ex situ microstructure analyses and in situ wafer curvature measurements. It was revealed that Ta thin films are oxidized to a crystalline TaO2 layer, which is subsequently oxidized to an amorphous tantalum pentoxide (a-Ta2O5) layer. Initial layered oxidation from Ta to TaO2 phases abruptly induces high compressive stress up to about 3.5 GPa with fast diffusion of oxygen through the Ta layer. Subsequently, it is followed by stress relaxation with the oxidation time, which is related to the slow oxidation from TaO2 to Ta2O5 phases. The initial compressive stress originates from the molar volume expansion during the layered formation of TaO2 from the Ta layer, while the relaxation of the compressive stresses is ascribed to the amorphous character of the a-Ta2O5 layer. According to Kissinger's analysis of the stress evolution during an isochronic heating process, the oxygen diffusion process through the a-Ta2O5 layer is the rate-controlling stage in the layered oxidation process of forming a a-Ta2O5/TaO2/Ta multilayer and has an activation energy of about 190.8 kJ/mol.

Download Full-text