From octahedral structure motif to sub-nanosecond phase transitions in phase change materials for data storage

As the most promising materials for phase-change data storage, the pseudobinary mGeTe•nSb2Te3 (GST) chalcogenides have been widely investigated. Nevertheless, an in-depth understanding of the thermal-transport property of GST is still lacking, which is important to achieve overall good performance of the memory devices. Herein, by using first-principles calculations and Boltzmann transport theory, we have systematically studied the lattice thermal conductivity along the out of plane direction of both stable hexagonal and meta-stable rock-salt-like phases of GST, and good agreement with available experiments has been observed. It is revealed that with the increase of the n/m ratio, the lattice thermal conductivity of hexagonal GST increases due to the large contribution from the weak Te-Te bonding, while an inverse trend is observed in meta-stable GST, which is due to the increased number of vacancies that results in the decrease of the lattice thermal conductivity. The size effect on thermal conductivity is also discussed. Our results provide useful information to manipulate the thermal property of GST phase-change materials.

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Structural Transitions in Ge2Sb2Te5 Phase Change Memory Thin Films Induced by Nanosecond UV Optical Pulses

Materials ◽

10.3390/ma13092082 ◽

2020 ◽

Vol 13 (9) ◽

pp. 2082

Author(s):

Mario Behrens ◽

Andriy Lotnyk ◽

Hagen Bryja ◽

Jürgen W. Gerlach ◽

Bernd Rauschenbach

Keyword(s):

Thin Films ◽

Phase Transitions ◽

Phase Change ◽

Data Storage ◽

Structural Changes ◽

Phase Change Memory ◽

Phase Changes ◽

Uv Laser ◽

Optical Pulses ◽

Change Memory

Ge-Sb-Te-based phase change memory alloys have recently attracted a lot of attention due to their promising applications in the fields of photonics, non-volatile data storage, and neuromorphic computing. Of particular interest is the understanding of the structural changes and underlying mechanisms induced by short optical pulses. This work reports on structural changes induced by single nanosecond UV laser pulses in amorphous and epitaxial Ge2Sb2Te5 (GST) thin films. The phase changes within the thin films are studied by a combined approach using X-ray diffraction and transmission electron microscopy. The results reveal different phase transitions such as crystalline-to-amorphous phase changes, interface assisted crystallization of the cubic GST phase and structural transformations within crystalline phases. In particular, it is found that crystalline interfaces serve as crystallization templates for epitaxial formation of metastable cubic GST phase upon phase transitions. By varying the laser fluence, GST thin films consisting of multiple phases and different amorphous to crystalline volume ratios can be achieved in this approach, offering a possibility of multilevel data storage and realization of memory devices with very low resistance drift. In addition, this work demonstrates amorphization and crystallization of GST thin films by using only one UV laser with one single pulse duration and one wavelength. Overall, the presented results offer new perspectives on switching pathways in Ge-Sb-Te-based materials and show the potential of epitaxial Ge-Sb-Te thin films for applications in advanced phase change memory concepts.

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Phase-Change Materials For Non-Volatile Data Storage

Nanostructured Materials for Advanced Technological Applications - NATO Science for Peace and Security Series B: Physics and Biophysics ◽

10.1007/978-1-4020-9916-8_47 ◽

2009 ◽

pp. 413-428

Author(s):

D. Lencer ◽

M. Wuttig

Keyword(s):

Phase Change ◽

Data Storage ◽

Phase Change Materials

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Understanding the Electro-thermal and Phase-transformation Processes in Phase-change Materials for Data Storage Applications

MRS Proceedings ◽

10.1557/proc-803-hh1.2 ◽

2003 ◽

Vol 803 ◽

Cited By ~ 4

Author(s):

C. D. Wright ◽

M. Armand ◽

M. M. Aziz ◽

S. Senkader ◽

W. Yu

Keyword(s):

Phase Change ◽

Data Storage ◽

Phase Change Materials ◽

Random Access ◽

Optical Data Storage ◽

Operating Conditions ◽

Optical Data ◽

Probe Type ◽

Practical Utilization ◽

Transformation Processes

ABSTRACTAttempts at the practical utilization of Sb-Te based alloys beyond optical data storage have been made recently by employing these materials in both scanning probe type memories, and in electrical memory devices - namely Phase-Change Random Access Memory (PC-RAM). We have developed models to simulate the electrical, thermal, and phase-change characteristics of this important class of material. In this paper we describe the physical basis of our models and present simulation results for different memory configurations and operating conditions.

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Nature of phase transitions in crystalline and amorphous GeTe-Sb2Te3 phase change materials

The Journal of Chemical Physics ◽

10.1063/1.3643327 ◽

2011 ◽

Vol 135 (12) ◽

pp. 124510 ◽

Cited By ~ 14

Author(s):

B. Kalkan ◽

S. Sen ◽

S. M. Clark

Keyword(s):

Phase Transitions ◽

Phase Change ◽

Phase Change Materials

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Phase-Change Media for High-Density Optical Recording

MRS Proceedings ◽

10.1557/proc-674-v1.2 ◽

2001 ◽

Vol 674 ◽

Cited By ~ 5

Author(s):

Herman Borg ◽

Martijn Lankhorst ◽

Erwin Meinders ◽

Wouter Leibbrandt

Keyword(s):

Phase Change ◽

Data Storage ◽

Laser Heating ◽

Phase Change Materials ◽

Optical Storage ◽

Sputter Deposition ◽

Optical Recording ◽

Thermal Design ◽

Recording Media ◽

Audio Video

ABSTRACTRewritable optical-storage systems are quickly gaining market share in audio, video and data- storage applications. The development of new rewritable optical-storage formats with higher capacity and data rate critically depends on innovations made to the recording media incorporating so-called phase-change materials. These materials allow reversible switching between a low and high reflective state induced by laser heating. In this paper, we highlight phase-change media aspects as optical and thermal design, sputter-deposition, materials optimization, and the development of new recording strategies. Focus is on the speed race in optical recording.

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