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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Avoided ferromagnetic quantum critical point in pressurized La 5 Co 2 Ge 3

We present the pressure-temperature phase diagram La 5 Co 2 Ge 3 up to ~ 5 GPa, which was constructed from magnetization, resistivity, and specific heat measurements. At ambient pressure, La 5 Co 2 Ge 3 is an itinerant ferromagnet with a Curie temperature T C ~ 4 K. Upon increasing pressure up to ~ 1.7 GPa, T C is suppressed down to ~ 3 K. Upon further increasing pressure, our results suggest that La 5 Co 2 Ge 3 enters a different low-temperature ground state. The corresponding transition temperature T* has a nonmonotonic pressure dependence up to ~ 5 GPa. Our results demonstrate that the ferromagnetic quantum critical point in La 5 Co 2 Ge 3 is avoided by the appearance of a different, likely magnetically ordered, state that has an antiferromagnetic component.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Strong magnetoelastic coupling in Mn 3 X ( X = Ge , Sn)

Here we measure the full elastic tensors of Mn 3 Ge and Mn 3 Sn as a function of temperature through their respective antiferromagnetic phase transitions. Large discontinuities in the bulk moduli at the Néel transitions indicate strong magnetoelastic coupling in both compounds. Strikingly, the discontinuities are nearly a factor of 10 larger in Mn 3 Ge than in Mn 3 Sn. We use the magnitudes of the discontinuities to calculate the pressure derivatives of the Néel temperature, which are 39 K/GPa 14.3 K/GPa for Mn 3 Ge and Mn 3 Sn, respectively. We measured the in-plane shear modulus c 66 , which couples strongly to the magnetic order, in magnetic fields up to 18 T and found quantitatively similar behavior in both compounds. Recent measurements have demonstrated strong piezomagnetism in Mn 3 Sn : Our results suggest that Mn 3 Ge may be an even better candidate for this effect.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Field-Induced Magnetic States in the Metallic Rare-Earth Layered Triangular Antiferromagnet TbAuAl 4 Ge 2

Magnetic frustration in metallic rare- earth lanthanides (Ln) with 4f electrons is crucial for producing interesting magnetic phases with high magnetic anisotropy where intertwined charge and spin degrees of freedom lead to novel phenomena. Here we report on the magnetic, thermodynamic, and electrical transport properties of TbAuAl 4 Ge 2 . Tb ions form two-dimensional triangular lattice layers which stack along the crystalline c axis. The magnetic phase diagram reveals multiple nearly degenerate ordered states upon applying field along the magnetically easy ab-plane before saturation. The magnetoresistance in this configuration exhibits intricate field dependence that closely follows that of the magnetization while the specific heat reveals a region of highly enhanced entropy, suggesting the possibility of a nontrivial spin textured phase. For fields applied along the c axis (hard axis), we find linear magnetoresistance over a wide range of fields. Further, we compare the magnetic properties and magnetoresistance with an isostructural GdAuAl 4 Ge 2 single crystal. These results identify TbAuAl 4 Ge 2 as an environment for complex quantum spin states and pave the way for further investigations of the broader LnAuAl 4 Ge 2 family of materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Suppression of metal-to-insulator transition and stabilization of superconductivity by pressure in Re 3 Ge 7

The effect of pressure on the low-temperature states of the Re 3 ⁡Ge 7 is investigated by both electrical and Hall resistance and magnetization measurements. At ambient pressure, the temperature-dependent resistance of Re 3 ⁡Ge 7 behaves quasilinearly from room temperature down to 60 K, then undergoes a two-step metal-to-insulator transition (MIT) at temperatures T 1 =59.4K and T 2 =58.7K, which may be related to a structural phase transition or occurrence of charge-density wave ordering. Upon applying pressure, the two-step (T 1 ,T 2 ) MIT splits into three steps (T 1 ,T 2 . and T 3 ) above 1 GPa, and all traces of MITs are fully suppressed by ~8 GPa. Subsequently, the onset of bulk superconductivity (SC) occurs between 10.8 and 12.2 GPa and persists to our highest pressure of 26.8 GPa. At 12.2 GPa the superconducting transition temperature, T c , and upper critical field, H c ⁢2 reach the maximum of T c (onset) ~5.9 K and H c ⁢2 (1.8 K) ~14 kOe. Finally, our results not only present the observation of SC under high pressure in Re 3 ⁡Ge 7 but also delineate the interplay between SC and other competing electronic states by creating a T-p phase diagram for this potentially topologically nontrivial system Re 3 ⁡Ge 7 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Multiple magnetic interactions and large inverse magnetocaloric effect in TbSi and TbSi 0.6 Ge 0.4

We present a comprehensive investigation of the electronic structure, magnetization, specific heat, and crystallography of TbSi (FeB structure type) and TbSi 0.6 ⁢Ge 0.4 (CrB structure type) compounds. Both TbSi and TbSi 0.6 ⁢Ge 0.4 exhibit two antiferromagnetic (AFM) transitions at T N⁢1 ≈ 58 and 57 K, and T N⁢2 ≈ 36 and 44 K, respectively, along with an onset of weak metamagneticlike transition around 6 T between T N⁢1 and T N⁢2 . High-resolution specific heat (C P ) measurements show the second- and first-order nature of the magnetic transition at T N⁢1 and T N⁢2 , respectively, for both samples. However, in the case of TbSi, the low-temperature (LT) AFM to high-temperature (HT) AFM transition takes place via an additional AFM phase at the intermediate temperature (IT), where both LT to IT AFM and IT to HT AFM phase transitions exhibit a first-order nature. Both TbSi and TbSi 0.6 ⁢Ge 0.4 manifest significant magnetic entropy changes (Δ⁢S M ) of 9.6 and 11.6 J/kg-K, respectively, for Δ⁢μ 0 ⁢H=7 T, at T N⁢2 . The HT AFM phase of TbSi 0.6 ⁢Ge 0.4 is found to be more susceptible to the external magnetic field, causing a significant broadening in the peaks of Δ⁢S M curves at higher magnetic fields. Temperature- and field-dependent specific-heat data have been utilized to construct the complex HT phase diagram of these compounds. As a result, temperature-dependent x-ray diffraction measurements demonstrate substantial magnetostriction and anisotropic thermal expansion of the unit cell in both samples.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Search for double-β decay of 76 Ge to excited states of 76 Se with the Majorana Demonstrator

The M AJORANA DEMONSTRATOR is a neutrinoless double-β decay search consisting of a low-background modular array of high-purity germanium detectors, ~2/3 of which are enriched to 88% in 76 Ge. The experiment is also searching for double-beta decay of 76 Ge to excited states (e.s.) in 76 Se. 76 Ge can decay into three daughter states of 76 Se, with clear event signatures consisting of a ββ-decay followed by the prompt emission of one or two γ rays. This results with high probability in multi-detector coincidences. In this work, the granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 41.9 kg yr of isotopic exposure, the DEMONSTRATOR has set world leading limits for each e.s. decay of 76 Ge, with 90% CL lower half-life limits in the range of (0.75–4.0) × 10 24 yr. In particular, for the 2ν transition to the first 0 + e.s. of 76 Se, a lower half-life limit of 7.5 × 10 23 yr at 90% CL was achieved.

59 ≤ A ≤ 89↗
DOE OSTI2023

Triaxiality and the nature of low-energy excitations in Ge 76

The deformation properties of the low-lying states in 76 Ge have been investigated following a safe energy Coulomb excitation measurement with the GRETINA tracking array and CHICO2 heavy-ion counter at the ATLAS accelerator facility at Argonne National Laboratory. A comprehensive set of transition and static E2 matrix elements were extracted from the measured differential Coulomb cross-sections, and compared with results of configuration interaction shell-model calculations and computations carried out within the framework of the generalized triaxial rotor model. The remarkable agreement between the calculated and experimental data supports a near-maximum triaxial deformation for the ground state of 76 Ge. Additionally, the degree of softness of the asymmetry in 76 Ge and 76 Se was investigated using rotational invariants generated from configuration interaction shell-model wave functions computed with the jj44b and JUN45 effective interactions. The resulting invariants are shown to be consistent with a stiff triaxial deformation in 76 Ge and a predominantly soft triaxial potential for 76 Se, in agreement with the conclusions of recent works by this collaboration.

59 ≤ A ≤ 89↗
DOE OSTI2024

Half-life of Ge 71 and the gallium anomaly

Recent discussions about the origin of the so-called gallium anomaly have motivated a remeasurement of the half-life of 71 Ge. Here, we have conducted three separate measurements using dedicated planar Ge detectors—one with 55 Fe as a standard, one with 57 Co as a standard, and one standalone 71 Ge measurement. Our results yield a half-life of 11.468±0.008 days, which is consistent with, but significantly more precise than, the currently accepted value. With this experiment, the potential explanation of the gallium anomaly being due to an unexpectedly long 71 Ge half-life has been ruled out, leaving the anomaly's origin as an open question.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Absence of Low-Energy Shape Coexistence in 80 Ge: The Nonobservation of a Proposed Excited 0 2 + Level at 639 keV

The 80 Ge structure was investigated in a high-statistics β-decay experiment of 80 Ga using the GRIFFIN spectrometer at TRIUMF-ISAC through γ, β-e, e-γ and γ-γ spectroscopy. No evidence was found for the recently reported 0 2 + 639-keV level suggested as evidence for low-energy shape coexistence in 80Ge. Large-scale shell model calculations performed in 78,80,82 Ge place the 0 2 + level in 80 Ge at 2 MeV. The new experimental evidence combined with shell model predictions indicate that low-energy shape coexistence is not present in 80 Ge.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Performance of III–V Solar Cells Grown on Reformed Mesoporous Ge Templates

We demonstrate a solar cell on reformed porous Ge with an efficiency of 7.7%. We generate mesopores in (100) Ge by bipolar electrochemical etching and anneal them at high temperature. The pores coalesce deep in the structure rather than at the surface as desired, although resulting in coarse superficial morphology unsuitable for device growth. To combat this issue, we developed a surface treatment involving an HBr dip, annealing at 415 degrees C, and a postannealing ultrasonic De-ionized water dip to improve the surface structure, resulting in a smoother reformed surface on which we grow a GaInAs solar cell. The structure retains embedded pores after growth and the transitions between Ge and III-V layers are distinct. The solar cell fabricated using the improved coalescence has an efficiency of 4.5%. The efficiency improves to 7.7% by isolating the rest of the device from three limiting localized shunt areas. Protruding defects in the porous Ge and III-V layers still limit the performance, but this work establishes a step toward the technical viability of this exfoliation approach, showing decent efficiency if protruding defects can be removed or reduced.

14 SOLAR ENERGY↗
DOE OSTI2024

Magneto-transport study on Sn-rich Sn 1–x Ge x thin films enabled by CdTe buffer layer

α-Sn, generally known as gray tin, has attracted significant scientific interest due to its potential to host novel topological phases. Studying the transport properties of α-Sn thin films grown on the InSb substrate has been challenging, as the InSb substrate also significantly contributes to the transport properties. In this article, we report a novel approach to epitaxially grow α-Sn thin films on an InSb substrate with a resistive buffer layer of CdTe. Thin films of α–Sn 1–x Ge x (x = 0, 0.025) alloy of 15 nm thickness have been grown using molecular beam epitaxy. The high quality of the samples has been determined through high-resolution x-ray diffraction. The CdTe buffer layer has high resistance and acts as an insulating virtual substrate, which significantly suppresses contribution from InSb. Magnetotransport measurements show clear Shubnikov–de Hass oscillations in α–Sn 1–x Ge x (x = 0, 0.025) thin films. A change in oscillation frequency is observed upon alloying with Ge, implying a modification in the electronic structure and demonstrating the effectiveness of the CdTe buffer layer approach. Furthermore, this work provides a new approach that enables the electronic transport characterization of the α–Sn 1–x Ge x alloy system, which enables the study of the topological quantum states using electronic transport and their device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Role of Oxygen on Chemical Segregation in Uncapped Ge 2 Sb 2 Te 5 Thin Films on Silicon Nitride

Germanium antimony telluride has been the most used and studied phase-change material for electronic memory due to its suitable crystallization temperature, amorphous to crystalline resistance contrast, and stability of the amorphous phase. In this paper, the segregation of Ge in a Ge 2 Sb 2 Te 5 film of 30 nm thickness during heating inside the transmission electron microscope was observed and characterized. Furthermore, Ge 2 Sb 2 Te 5 film was deposited using sputtering on a Protochips Fusion holder and left uncapped in atmosphere for about four months. Oxygen incorporated within the film played a significant role in the chemical segregation observed which resulted in amorphous Ge-O island boundaries and Sb and Te rich crystalline domains. Such composition changes can occur when the phase-change material interfaces insulating oxide layers in an integrated device and can significantly impact its electrical and thermal properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Ge(WO3)6 by Materials Project

Ge(WO3)6 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are eight inequivalent W+5.33+ sites. In the first W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–28°. There is one shorter (1.94 Å) and five longer (1.95 Å) W–O bond length. In the second W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–45°. There are a spread of W–O bond distances ranging from 1.86–2.11 Å. In the third W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–46°. There are a spread of W–O bond distances ranging from 1.87–2.10 Å. In the fourth W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–28°. There are a spread of W–O bond distances ranging from 1.91–1.98 Å. In the fifth W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–46°. There are a spread of W–O bond distances ranging from 1.86–2.11 Å. In the sixth W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–28°. There are a spread of W–O bond distances ranging from 1.90–2.00 Å. In the seventh W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–28°. There is four shorter (1.94 Å) and two longer (1.95 Å) W–O bond length. In the eighth W+5.33+ site, W+5.33+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–45°. There are a spread of W–O bond distances ranging from 1.92–2.10 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded in an L-shaped geometry to two equivalent O2- atoms. Both Ge–O bond lengths are 1.89 Å. In the second Ge4+ site, Ge4+ is bonded in an L-shaped geometry to two equivalent O2- atoms. Both Ge–O bond lengths are 1.89 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.33+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.33+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.33+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two W+5.33+ and one Ge4+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent W+5.33+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent W+5.33+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent W+5.33+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent W+5.33+ atoms. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.33+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.33+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two W+5.33+ and one Ge4+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.33+ atoms. In the thirteenth O2- site, O2- is bonded in a linear geometry to two W+5.33+ atoms. In the fourteenth O2- site, O2- is bonded in a linear geometry to two W+5.33+ atoms. In the fifteenth O2- site, O2- is bonded in a linear geometry to two W+5.33+ atoms. In the sixteenth O2- site, O2- is bonded in a linear geometry to two W+5.33+ atoms. In the seventeenth O2- site, O2- is bonded in a linear geometry to two W+5.33+ atoms. In the eighteenth O2- site, O2- is bonded in a linear geometry to two W+5.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(SbTe2)2 by Materials Project

Ge(SbTe2)2 is Calaverite-derived structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three Ge(SbTe2)2 sheets oriented in the (0, 0, 1) direction. Ge4+ is bonded to six equivalent Te2- atoms to form GeTe6 octahedra that share corners with six equivalent TeSb3Te3 octahedra, edges with six equivalent GeTe6 octahedra, and edges with six equivalent TeSb3Te3 octahedra. The corner-sharing octahedral tilt angles are 7°. All Ge–Te bond lengths are 3.01 Å. Sb2+ is bonded in a distorted T-shaped geometry to three equivalent Te2- atoms. All Sb–Te bond lengths are 3.03 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Sb2+ and three equivalent Te2- atoms to form TeSb3Te3 octahedra that share corners with three equivalent GeTe6 octahedra, edges with three equivalent GeTe6 octahedra, and edges with six equivalent TeSb3Te3 octahedra. The corner-sharing octahedral tilt angles are 7°. All Te–Te bond lengths are 3.31 Å. In the second Te2- site, Te2- is bonded to three equivalent Ge4+ and three equivalent Te2- atoms to form a mixture of distorted corner and edge-sharing TeGe3Te3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(SbTe2)2 by Materials Project

Ge(SbTe2)2 is MAX Phase-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three Ge(SbTe2)2 sheets oriented in the (0, 0, 1) direction. Ge4+ is bonded to six Te2- atoms to form GeTe6 octahedra that share corners with three equivalent SbTe6 octahedra, edges with three equivalent SbTe6 octahedra, and edges with six equivalent GeTe6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are three shorter (2.85 Å) and three longer (3.27 Å) Ge–Te bond lengths. There are two inequivalent Sb2+ sites. In the first Sb2+ site, Sb2+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing SbTe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are three shorter (3.01 Å) and three longer (3.20 Å) Sb–Te bond lengths. In the second Sb2+ site, Sb2+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent GeTe6 octahedra, corners with three equivalent SbTe6 octahedra, edges with three equivalent GeTe6 octahedra, and edges with nine SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 1–6°. There are three shorter (3.03 Å) and three longer (3.17 Å) Sb–Te bond lengths. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Sb2+ atoms. In the second Te2- site, Te2- is bonded to six Sb2+ atoms to form TeSb6 octahedra that share corners with three equivalent TeGe3Sb3 octahedra and edges with nine TeSb6 octahedra. The corner-sharing octahedral tilt angles are 4°. In the third Te2- site, Te2- is bonded to three equivalent Ge4+ and three equivalent Sb2+ atoms to form a mixture of edge and corner-sharing TeGe3Sb3 octahedra. The corner-sharing octahedral tilt angles are 4°. In the fourth Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Ge4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(SbTe2)2 by Materials Project

Ge(SbTe2)2 is MAX Phase-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three Ge(SbTe2)2 sheets oriented in the (0, 0, 1) direction. Ge4+ is bonded to six Te2- atoms to form GeTe6 octahedra that share corners with three equivalent SbTe6 octahedra, edges with three equivalent SbTe6 octahedra, and edges with six equivalent GeTe6 octahedra. The corner-sharing octahedral tilt angles are 7°. There are three shorter (2.86 Å) and three longer (3.32 Å) Ge–Te bond lengths. There are two inequivalent Sb2+ sites. In the first Sb2+ site, Sb2+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing SbTe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are three shorter (3.02 Å) and three longer (3.21 Å) Sb–Te bond lengths. In the second Sb2+ site, Sb2+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent GeTe6 octahedra, corners with three equivalent SbTe6 octahedra, edges with three equivalent GeTe6 octahedra, and edges with nine SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 1–7°. There are three shorter (3.03 Å) and three longer (3.16 Å) Sb–Te bond lengths. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Ge4+ atoms. In the second Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Sb2+ atoms. In the third Te2- site, Te2- is bonded to six Sb2+ atoms to form TeSb6 octahedra that share corners with three equivalent TeGe3Sb3 octahedra and edges with nine TeSb6 octahedra. The corner-sharing octahedral tilt angles are 3°. In the fourth Te2- site, Te2- is bonded to three equivalent Ge4+ and three equivalent Sb2+ atoms to form a mixture of edge and corner-sharing TeGe3Sb3 octahedra. The corner-sharing octahedral tilt angles are 3°.

36 MATERIALS SCIENCE↗
DOE OSTI2023

High‐Throughput Study of Amorphous Stability and Optical Properties of Superlattice‐Like Ge–Sb–Te Thin Films

A high‐throughput ion beam sputtering system is used to synthesize compositional gradient superlattice‐like (SLL) thin film libraries of Ge–Sb–Te alloys over the entire phase diagram. Here, the optical properties and structural evolution of the Ge–Sb–Te combinatorial SLL thin film are investigated. A systematic screening over the annealing temperature, annealing time, and modulation period has elucidated the critical factors that affect the stability of the metastable phase and optical properties. It is found that amorphous stability and optical constant are highly dependent on the modulation period and chemical composition of the thin film. This data‐driven approach offers new perspectives for accelerating the development of new materials with excellent optical and amorphous stability and for exploring their mechanisms, by greatly expanding the dataset of Ge–Sb–Te alloys with SLL structures through high‐throughput experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Phase evolution and amorphous stability upon solid-state reaction in superlattice like Ge–Sb–Te combinatorial thin-film

In this paper, the superlattice-like (SLL) Ge–Sb–Te combinatorial thin films were prepared by using a high-throughput ion beam sputtering system. The phase evolution and amorphous stability of such films undergoing heat treatment as a function of the coating sequence and modulation period were systematically studied. The composition structure diagram was constructed via an automated process of data obtained by high-throughput synchrotron micro-X-ray diffraction and lab-based micro-X-ray fluorescence. Furthermore, the element distribution and microstructure in the depth direction of the SLL thin films were characterized with time-of-flight secondary ion mass spectrometry and transmission electron microscopy, respectively. These studies demonstrated that the coating sequence has a significant effect on the element distribution in the as-deposited SLL thin films and the structure of the final product upon solid-state reaction. Reducing the modulation period of the SLL thin film improves the stability of the amorphous Ge–Sb–Te phase. This work lays a solid foundation for the rational design of SLL Ge–Sb–Te thin films to improve their performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗