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1. Toward understanding the phase-selective growth mechanism of films and geometrically-shaped flakes of 2D MoTe ₂

   https://doi.org/10.1039/d1ra07787b  

   Limbu, Tej B.; Adhikari, Bikram; Song, Seung Keun; Chitara, Basant; Tang, Yongan; Parsons, Gregory N.; Yan, Fei (November 2021, RSC Advances)

   Two-dimensional (2D) molybdenum ditelluride (MoTe 2 ) is an interesting material for fundamental study and applications, due to its ability to exist in different polymorphs of 2H, 1T, and 1T′, their phase change behavior, and unique electronic properties. Although much progress has been made in the growth of high-quality flakes and films of 2H and 1T′-MoTe 2 phases, phase-selective growth of all three phases remains a huge challenge, due to the lack of enough information on their growth mechanism. Herein, we present a novel approach to growing films and geometrical-shaped few-layer flakes of 2D 2H-, 1T-, and 1T′-MoTe 2 by atmospheric-pressure chemical vapor deposition (APCVD) and present a thorough understanding of the phase-selective growth mechanism by employing the concept of thermodynamics and chemical kinetics involved in the growth processes. Our approach involves optimization of growth parameters and understanding using thermodynamical software, HSC Chemistry. A lattice strain-mediated mechanism has been proposed to explain the phase selective growth of 2D MoTe 2 , and different chemical kinetics-guided strategies have been developed to grow MoTe 2 flakes and films. 

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2. Dynamic adhesion of 2D materials to mixed-phase BiFeO 3 structural phase transitions

   https://doi.org/10.1063/5.0096686  

   Watson, Carla; Peña, Tara; Abdin, Marah; Khan, Tasneem; Wu, Stephen M. (July 2022, Journal of Applied Physics)

   Two-dimensional materials, such as transition metal dichalcogenides, have generated much interest due to their strain-sensitive electronic, optical, magnetic, superconducting, or topological properties. Harnessing control over their strain state may enable new technologies that operate by controlling these materials’ properties in devices such as straintronic transistors. Piezoelectric oxides have been proposed as one method to control such strain states on the device scale. However, there are few studies of how conformal 2D materials remain on oxide materials with respect to dynamic applications of the strain. Non-conformality may lead to non-optimal strain transfer. In this work, we explore this aspect of oxide-2D adhesion in the nanoscale switching of the substrate structural phase in thin 1T′-MoTe 2 attached to a mixed-phase thin-film BiFeO 3 (BFO), a multiferroic oxide with an electric-field induced structural phase transition that can generate mechanical strains of up to 2%. We observe that flake thickness impacts the conformality of 1T′-MoTe 2 to structural changes in BFO, but below four layers, 1T′-MoTe 2 fully conforms to the nanoscale BFO structural changes. The conformality of few-layer 1T′-MoTe 2 suggests that BFO is an excellent candidate for deterministic, nanoscale strain control for 2D materials. 

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3. Single‐Step Synthesis of In‐plane 1T'‐2H Heterophase MoTe ₂ for Low‐Resistance Contacts

   https://doi.org/10.1002/adfm.202511589  

   Lin, Ye; Lee, Hanwool; Kang, Junzhe; Wang, Zhiyu; Haasch, Richard T; Chyczewski, Stasiu T; Liu, Zetai; Chuang, Huai‐Chung; Zheng, Jun‐Fei; Zhu, Wenjuan (January 2026, Advanced Functional Materials)

   Abstract MoTe₂possesses two polymorphs: semiconducting (2H) and semi‐metallic (1T') phases, separated by a small energy barrier. The 1T' phase of MoTe₂provides an excellent platform for forming low‐resistance contacts with the 2H phase, where the low density of states in the semimetal suppresses metal‐induced gap states (MIGS) and reduces Fermi‐level pinning. However, existing fabrication methods encounter significant challenges in location control, contact quality, and device scaling. In this work, a new method is developed to synthesize 1T'‐2H heterophase structures using chemical vapor deposition (CVD). By depositing pre‐patterned molybdenum, seamless in‐plane 1T'‐2H MoTe₂heterophase junctions are synthesized in a single‐step process, achieving precise control over the location of each phase and uniform MoTe₂coverage across centimeter‐scale surfaces. Field‐effect transistors incorporating 1T' MoTe₂contacts and 2H MoTe₂channels show p‐type dominant transfer characteristics and exceptionally low contact resistance. The unique attributes of these 1T' MoTe₂contacts, including pristine interfaces, reduced Schottky barrier heights, and seamless edge contacts, combined with the pronounced ambipolarity of the grown 2H MoTe₂, demonstrate the commercial viability of this process for 2D transistors, addressing the long‐standing challenge of contact resistance in 2D transistor technology. 

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4. In-plane anisotropic two-dimensional materials for twistronics

   https://doi.org/10.1088/1361-6528/ad2c53  

   Kim, Hangyel; Kim, Changheon; Jung, Yeonwoong; Kim, Namwon; Son, Jangyup; Lee, Gwan-Hyoung (April 2024, Nanotechnology)

   Abstract In-plane anisotropic two-dimensional (2D) materials exhibit in-plane orientation-dependent properties. The anisotropic unit cell causes these materials to show lower symmetry but more diverse physical properties than in-plane isotropic 2D materials. In addition, the artificial stacking of in-plane anisotropic 2D materials can generate new phenomena that cannot be achieved in in-plane isotropic 2D materials. In this perspective we provide an overview of representative in-plane anisotropic 2D materials and their properties, such as black phosphorus, group IV monochalcogenides, group VI transition metal dichalcogenides with 1T′ and T_dphases, and rhenium dichalcogenides. In addition, we discuss recent theoretical and experimental investigations of twistronics using in-plane anisotropic 2D materials. Both in-plane anisotropic 2D materials and their twistronics hold considerable potential for advancing the field of 2D materials, particularly in the context of orientation-dependent optoelectronic devices. 

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5. Spin-resolved topology and partial axion angles in three-dimensional insulators

   https://doi.org/10.1038/s41467-024-44762-w  

   Lin, Kuan-Sen; Palumbo, Giandomenico; Guo, Zhaopeng; Hwang, Yoonseok; Blackburn, Jeremy; Shoemaker, Daniel P.; Mahmood, Fahad; Wang, Zhijun; Fiete, Gregory A.; Wieder, Benjamin J.; et al (December 2024, Nature Communications)

   Abstract Symmetry-protected topological crystalline insulators (TCIs) have primarily been characterized by their gapless boundary states. However, in time-reversal- ($${{{{{{{\mathcal{T}}}}}}}}$$ $T$ -) invariant (helical) 3D TCIs—termed higher-order TCIs (HOTIs)—the boundary signatures can manifest as a sample-dependent network of 1D hinge states. We here introduce nested spin-resolved Wilson loops and layer constructions as tools to characterize the intrinsic bulk topological properties of spinful 3D insulators. We discover that helical HOTIs realize one of three spin-resolved phases with distinct responses that are quantitatively robust to large deformations of the bulk spin-orbital texture: 3D quantum spin Hall insulators (QSHIs), “spin-Weyl” semimetals, and$${{{{{{{\mathcal{T}}}}}}}}$$ $T$ -doubled axion insulator (T-DAXI) states with nontrivial partial axion angles indicative of a 3D spin-magnetoelectric bulk response and half-quantized 2D TI surface states originating from a partial parity anomaly. Using ab-initio calculations, we demonstrate thatβ-MoTe₂realizes a spin-Weyl state and thatα-BiBr hosts both 3D QSHI and T-DAXI regimes. 

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