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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on ReSe2 by Materials Project

ReSe2 is Molybdenite-like structured and crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one ReSe2 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Re4+ sites. In the first Re4+ site, Re4+ is bonded to six Se2- atoms to form distorted edge-sharing ReSe6 octahedra. There are a spread of Re–Se bond distances ranging from 2.45–2.66 Å. In the second Re4+ site, Re4+ is bonded to six Se2- atoms to form distorted edge-sharing ReSe6 octahedra. There are a spread of Re–Se bond distances ranging from 2.49–2.62 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three Re4+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three Re4+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three Re4+ atoms. In the fourth Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to three Re4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2In(ReSe4)2 by Materials Project

TaSe2TaInSe2(ReSe2)2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of two ReSe2 sheets oriented in the (0, 0, 1) direction; one TaInSe2 sheet oriented in the (0, 0, 1) direction; and one TaSe2 sheet oriented in the (0, 0, 1) direction. In each ReSe2 sheet, Re3+ is bonded to six Se2- atoms to form distorted edge-sharing ReSe6 pentagonal pyramids. There are three shorter (2.53 Å) and three longer (2.54 Å) Re–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Re3+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Re3+ atoms. In the TaInSe2 sheet, Ta+4.50+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. There are three shorter (2.61 Å) and three longer (2.62 Å) Ta–Se bond lengths. In1+ is bonded in a 6-coordinate geometry to three equivalent Se2- atoms. All In–Se bond lengths are 3.16 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta+4.50+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to three equivalent Ta+4.50+ and three equivalent In1+ atoms. In the TaSe2 sheet, Ta+4.50+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta+4.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Machine-learning-assisted analysis of transition metal dichalcogenide thin-film growth

In situ reflective high-energy electron diffraction (RHEED) is widely used to monitor the surface crystalline state during thin-film growth by molecular beam epitaxy (MBE) and pulsed laser deposition. With the recent development of machine learning (ML), ML-assisted analysis of RHEED videos aids in interpreting the complete RHEED data of oxide thin films. The quantitative analysis of RHEED data allows us to characterize and categorize the growth modes step by step, and extract hidden knowledge of the epitaxial film growth process. In this study, we employed the ML-assisted RHEED analysis method to investigate the growth of 2D thin films of transition metal dichalcogenides (ReSe2) on graphene substrates by MBE. Principal component analysis (PCA) and K-means clustering were used to separate statistically important patterns and visualize the trend of pattern evolution without any notable loss of information. Using the modified PCA, we could monitor the diffraction intensity of solely the ReSe2 layers by filtering out the substrate contribution. These findings demonstrate that ML analysis can be successfully employed to examine and understand the film-growth dynamics of 2D materials. Further, the ML-based method can pave the way for the development of advanced real-time monitoring and autonomous material synthesis techniques.

36 MATERIALS SCIENCE↗
DOE OSTI2025

In Situ Atomic Tracking on the Interfacial Etching and Reconfiguration of Cu-ReSe 2 Contact during Thermal Annealing

The Schottky barrier height can be greatly affected by the metal diffusion, reaction, and covalent bonding formation at the contact. Exploring novel methods and revealing the fundamental mechanisms for contact engineering are of vital importance for microelectronic devices. Here, in this study, the annealing induced interfacial reactions at Cu-ReSe 2 contact are dynamically revealed from the atomic scale. Accompanied by the diffusion of Se to Cu, ReSe 2 is gradually decomposed to a thin Re interlayer through a “chain-by-chain” manner. Theoretical calculations show that the Cu atoms can facilitate the chemical bond breaking of ReSe 2 , significantly lowering the Se diffusion energy barrier toward Cu. The formed Re/ReSe 2 heterostructure presents a metal-like band structure, which underscores the critical role of Cu in altering the interfacial chemistry and promoting carrier transport across the interface. Our results can provide vital insights into the contact properties of ReSe 2 and provide a possible method for fabricating high-performance ReSe 2 -based devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗