GST sputtering target
A Review of Germanium-Antimony-Telluride Phase-Change
In sputtering, a target with the correct GST composition is typically used as the material source.
Chalcogenide phase change materials based on germanium-antimony-tellurides (GST-PCMs) have shown outstanding properties in non-volatile memory (NVM) technologies due to their high write and read speeds, reversible phase transition, the high degree of scalability, low power consumption, good data retention, and multi-level storage capability.
However, GST-based PCMs have shown recent promise in other domains, such as in spatial light modulation, beam steering, and neuromorphic computing.
This paper reviews the progress in GST-based PCMs and methods for improving the performance within the context of new applications that have come to light in recent years.
Keywords: phase-change materials;
GST; non-volatile memory ;
electrical properties ;
optical properties ;
Over the past few decades, chalcogenide phase change materials have received increased attention for next-generation non-volatile memory [ 1, 2, 3 ] and high-density optical recording [ 4, 5, 6 ].
Typically, a chalcogenide material has two or more discrete states at which it exhibits distinguishable material properties.
The change in the state is driven by thermal excitation, usually via an electrical or optical pulse.
The significant difference between these states in electrical and optical properties upon the reversible switching allows storing the rewritable digital bit information.
The most ubiquitous phase change material, GeSbTe (germanium-antimony-tellurium or GST), is a ternary compound consisting of germanium, antimony, and tellurium that is capable of reversibly switching at high speeds between its amorphous and crystalline states in response to thermal excitation.
The crystallization temperature of the alloy is between 100∘
C and the melting point is about 600℃ (873 K).
Due to the non-volatility and high stability of both states, chalcogenide phase change materials have been used in rewritable optical recording media for years [ 7, 8, 9 ].
In the optical recording media application, a laser with controllable intensity and pulse duration is used to interact with the material, namely, heat a small volume to switch the material between crystalline and amorphous states.
The information is then stored in the reflectivity of the phase change material layer.
For electronic memories, even though Flash memory is the current leading technology for non-volatile memory devices, the next generation of memory requires even higher speeds for write and erase processes, while maintaining high endurance, good scalability, low cost, and high power efficiency.
With developments in lithography and discoveries in chalcogenide compounds, recently GST emerged as an important candidate for electronic nonvolatile memory devices [ 10, 11, 12, 13 ].
Within longer-term prospects, new proposals and early demonstrations have emerged for exploiting the optical properties of GST for dynamic light modulation applications.
By utilizing the difference in optical properties between different phases, researchers have developed GST-based reconfigurable light modulators [ 14 ], optical limiters [ 15 ], optical switches [ 16 ], and polarizing reflectors [ 17 ].
In this review paper, we start with a description of basic GeSbTe alloys and their phase switching properties, material properties including the electrical, structural, and optical ( Section 2 ).
Non-volatile phase change memory devices are reviewed in Section 3.1. Light modulators that utilize the contrast of the optical constants are discussed in Section 3.2.
Even though GST phase change material shows promising in both non-volatile memory and optical modulators, it is necessary to modify the electrical property for power efficiency, high-speed operation, and stability.
Therefore, in Section 4, doping mechanisms, and their effects on the material response are reviewed.
Finally, fabrication methods of GST and doped-GST are discussed in Section 5.
Crystallization Kinetics of GeSbTe Phase-Change
Although nanostructured phase-change materials (PCMs) are considered as the building blocks of next-generation phase-change memory and other emerging optoelectronic applications, the kinetics of the crystallization, the central property in switching, remains ambiguous in the high-temperature regime.
Therefore, we present here an innovative exploration of the crystallization kinetics of Ge2Sb2Te5 (GST) nanoparticles (NPs) exploiting differential scanning calorimetry with ultrafast heating up to 40 000 Ks–1.
Our results demonstrate that the non-Arrhenius thermal dependence of viscosity at high temperature becomes an Arrhenius-like behavior when the glass transition is approached, indicating a fragile-to-strong (FS) crossover in the as-deposited amorphous GST NPs.
The overall crystal growth rate of the GST NPS is unraveled as well.
This unique feature of the FS crossover is favorable for memory applications as it is correlated to improved data retention.
Furthermore, we show that methane incorporation during NP production enhances the stability of the amorphous NP phase (and thereby data retention), while a comparable maximum crystal growth rate is still observed.
These results offer deep insight into the crystallization kinetics of nanostructured GST, paving the way for designing nonvolatile memories with PCM dimensions smaller than 20 nm.
Ge2Sb2Te5 (GST), one of the prototypical phase-change materials (PCMs), enables rapid and reversible switching between its amorphous and crystalline phases, which is accompanied by large optical and electrical contrast.
This unique feature makes GST attractive for data-storage applications 1 − 3 and a strong contender for emerging applications, such as solid-state displays, 4 optical modulators, 5 neuromorphic computing, 6, 7 on-chip photonic circuitry, 8 and plasmonic-based circuits.
9 Crystallization lies at the heart of the switching in phase-change technology;
thus, a solid understanding of the crystallization kinetics entails a crucial aspect of designing phase-change memory.
Conventional measurements are only able to investigate crystallization kinetics within a relatively low-temperature range (near the glass transition temperature).
10 − 13 However, in actual applications, crystallization generally takes place at higher temperatures.
Despite its scientific and technologic relevance, the analysis of the crystallization kinetics at these high temperatures has remained for a long time highly challenging due to the ultrashort time and length scales (ns and nm) involved.
This situation persisted until very recently, where ultrafast differential scanning calorimetry (DSC) was utilized to explore the crystallization process of GST films with heating rates up to 40 000 Ks–1.
14 Using subsequent extensive modeling, growth rates ranging from the glass transition temperature to the melting temperature were derived for the film structures, showing a remarkable breakdown of Arrhenius behavior in the viscosity at heating rates beyond ∼500 Ks–1. Non-Arrhenius thermal dependence of the viscosity at high temperatures has lately been widely observed in both nucleation-dominated and growth-dominated PCMs.
For instance, for GST confined in memory cells it was demonstrated that non-Arrhenius thermal dependence of crystallization at high temperatures crosses over to a wide temperature range at lower temperatures where still Arrhenius behavior prevails.
15 − 17 In recent years, also for other PCMs, such as the films, 18 supercooled and melt-quenched AgInSbTe films, 19 − 21, and GeSb films, 22, 23 the crystallization kinetics have been determined based on nonconventional techniques with measurements spanning relatively wide temperature ranges.
All these works confirm the breakdown of Arrhenius dependence for amorphous PCMs at high temperatures.
However, a question that remains is whether this breakdown can be described on the basis of a model for viscosity with a single value for the fragility.
In parallel, down-scaling the GST into (sub lithographic) nanostructures generates tremendous advantages for PCM-based memory including ultrafast switching, low switching power, and ultrahigh density.
Therefore, many efforts have been devoted to entering this promising field.
24, 25 In this context, the fabrication of monodisperse GST nanoparticles (NPs) with good size and composition control has been a great challenge for a long time.
We achieved a breakthrough by exploiting a technique based on gas-phase condensation and magnetron sputtering, which is capable of meeting the requirements of GST N
Germanium Antimony Telluride Sputtering Targets Ge3Sb2Te6 are also available. Typical purity: 99.99% GeSbTe (germanium-antimony-tellurium or GST)
Germanium Antimony Telluride Sputtering Targets Ge2Sb2Te5 are available in various sizes from 2 inches to 4-inch diameter.
Germanium Antimony Telluride Sputtering Targets Ge3Sb2Te6 are also available.
Typical purity: 99.99%
GeSbTe (germanium-antimony-tellurium or GST) is a phase-change material from the group of chalcogenide glasses used in rewritable optical discs and phase-change memory applications.
Its recrystallization time is 20 nanoseconds, allowing bitrates of up to 35 Mbit/s to be written and direct overwrite capability up to 106 cycles.
It is suitable for land-groove recording formats.
It is often used in rewritable DVDs.
New phase-change memories are possible using n-doped GeSbTe semiconductor.
The melting point of the alloy is about 600°C (900 K) and the crystallization temperature is between 100 and 150°C.
Germanium Antimony Telluride Theoretical Properties
GST sputtering target
Germanium Antimony Telluride Sputtering Targets (Ge2Sb2Te5)
Telluride Sputtering Targets, we have rich experience to manufacture and sell high purity Ge2Sb2Te5 sputtering targets.
1 H 1 He 2
2 Li3 Be4 B5 C6 N 7 O 8 F 9 Ne 10
3 Na11 Mg12 Al13 Si14 P 15 S 16 Cl 17 Ar 18
4 K19 Ca20 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30 Ga31 Ge32 As 33 Se34 Br 35 Kr 36
5 Rb 37 Sr38 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48 In49 Sn50 Sb51 Te52 I 53 Xe 54
6 Cs 55 Ba56 La57 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80 Tl 81 Pb82 Bi83 Po 84 At 85 Rn 86
7 Fr 87 Ra 88 Ac 89 Rf 104 Db 105 Sg 106 Bh 107 Hs 108 Mt 109 Uun 110 Uuu 111 Uub 112 Uut 113 Uuq 114 Uup 115 Uuh 116 Uus 117 Uuo 118
8 Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 Eu 63 Gd 64 Tb 65 Dy 66 Ho 67 Er68 Tm69 Yb70 Lu71
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%, 99.999%. Shape---Discs: Dia(≤480mm),Thickness(≥0.5mm) Rectangle:
Germanium Antomony Telluride (Ge2Sb2Te5) Sputtering Target
Purity--- 99.99%, 99.999%
Application --- Semiconductors field, PCM material.
Germanium Antimony Telluride (Ge2Sb2Te5) Evaporation Material
Purity --- 99.99%，99.999%
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