Tunable optical and electronic properties of gallium telluride monolayer for photovoltaic absorbers and ultraviolet detectors

Broadband Photodetection of Centimeter-Scale T-Phase Gallium Telluride Grown by Molecular Beam Epitaxy

Two-dimensional (2D) semiconductors have recently attracted considerable attention due to their promising applications in future integrated electronic and optoelectronic devices. Large-scale synthesis of high-quality 2D semiconductors is an increasingly essential requirement for practical applications, such as sensing, imaging, and communications. In this work, homogeneous 2D GaTe films on a centimeter scale are epitaxially grown on fluorphlogopite mica substrates by molecular beam epitaxy (MBE). The epitaxial GaTe thin films showed an atomically 2D layered lattice structure with a T phase, which has not been discovered in the GaTe geometric isomer. Furthermore, semiconducting behavior and high mobility above room temperature were found in T-GaTe epitaxial films, which are essential for application in semiconducting devices. The T-GaTe-based photodetectors demonstrated respectable photodetection performance with a responsivity of 13 mA/W and a fast response speed. By introducing monolayer graphene as the substrate, we successfully realized high-quality GaTe/graphene heterostructures. The performance has been significantly improved, such as the responsivity was enhanced more than 20 times. These results highlight a feasible scheme for exploring the crystal phase of 2D GaTe and realizing the controlled growth of GaTe films on large substrates, which could promote the development of broadband, high-performance, and large-scale photodetection applications.

Record-High Work-Function p-Type CuBiP2 Se6 Atomic Layers for High-Photoresponse van der Waals Vertical Heterostructure Phototransistor

The notable lack of intrinsic p-type 2D layered semiconductors has hindered the engineering of 2D devices for complementary metal oxide semiconductors (CMOSs). Herein, a novel quaternary intrinsic p-type 2D semiconductor, CuBiP₂ Se₆ atomic layers, is introduced into the 2D family. The semiconductor displays a high work function of 5.26 eV, a moderate hole mobility of 1.72 cm² V^-1 s^-1 , and an ultrahigh on/off current exceeding 10⁶ at room temperature. To date, 5.26 eV is the highest work-function recorded in p-type 2D materials, indicating the ultrastable p-type behavior of CuBiP₂ Se₆ . Additionally, a multilayer graphene/CuBiP₂ Se₆ /multilayer graphene (MLG/CBPS/MLG)-based fully vertical van der Waals heterostructure phototransistor is designed and fabricated. This device exhibits outstanding optoelectronic performance with a responsivity (R) of 4.9 × 10⁴ A W^-1 , an external quantum efficiency (EQE) of 1.5 × 10⁷ %, a detectivity (D) of 1.14 × 10¹³ Jones, and a broad working wavelength (400-1100 nm), respectively. This is comparable to state-of-the-art 2D devices. Such excellent performance is attributed to the ultrashort transmit length and nondestructive/defect-free contacts. This leads to faster response speed and eliminates Fermi-level pinning effects. Moreover, ultrahigh responsivity and detectivity endow the device with applaudable imaging sensing capability. These results make CuBiP₂ Se₆ an ideal p-type candidate material for next-generation CMOSs logic devices.

Gallium-Telluride-Based Composite as Promising Lithium Storage Material

Various applications of gallium telluride have been investigated, such as in optoelectronic devices, radiation detectors, solar cells, and semiconductors, owing to its unique electronic, mechanical, and structural properties. Among the various forms of gallium telluride (e.g., GaTe, Ga₃Te₄, Ga₂Te₃, and Ga₂Te₅), we propose a gallium (III) telluride (Ga₂Te₃)-based composite (Ga₂Te₃-TiO₂-C) as a prospective anode for Li-ion batteries (LIBs). The lithiation/delithiation phase change mechanism of Ga₂Te₃ was examined. The existence of the TiO₂-C hybrid buffering matrix improved the electrical conductivity as well as mechanical integrity of the composite anode for LIBs. Furthermore, the impact of the C concentration on the performance of Ga₂Te₃-TiO₂-C was comprehensively studied through cyclic voltammetry, differential capacity analysis, and electrochemical impedance spectroscopy. The Ga₂Te₃-TiO₂-C electrode showed high rate capability (capacity retention of 96% at 10 A g^-1 relative to 0.1 A g^-1) as well as high reversible specific capacity (769 mAh g^-1 after 300 cycles at 100 mA g^-1). The capacity of Ga₂Te₃-TiO₂-C was enhanced by the synergistic interaction of TiO₂ and amorphous C. It thereby outperformed the majority of the most recent Ga-based LIB electrodes. Thus, Ga₂Te₃-TiO₂-C can be thought of as a prospective anode for LIBs in the future.

Exploration of exciton dynamics in GaTe nanoflakes via temperature- and power-dependent time-resolved photoluminescence spectra

GaTe nanoflakes have been receiving much research attention recently due to their applications in optoelectronic devices, such as anisotropic non-volatile memory, solar cells, and high-sensitivity photodetectors from the ultraviolet to the visible region. Further applications, however, have been impeded due to the limited understanding of their exciton dynamics. In this work we perform temperature- and power-dependent time-resolved photoluminescence (PL) spectra to comprehensively investigate the exciton dynamics of GaTe nanoflakes. Temperature-dependent PL measurements manifest that spectral profiles of GaTe nanoflakes change dramatically from cryogenic to room temperature, where the bound exciton and donor-to-acceptor pair transition normally disappear above 100 K, while the charged exciton survives to room temperature. The lifetimes of these excitons and their evolution vs temperature have been uncovered by time-resolved PL spectra. Further measurements reveal the entirely different power-dependent exciton behaviors of GaTe nanoflakes between room and cryogenic temperatures. The underlying mechanisms have been proposed to explore the sophisticated exciton dynamics within GaTe nanoflakes. Our results offer a more thorough understanding of the exciton dynamics of GaTe nanoflakes, enabling further progress in engineering GaTe-based applications, such as photodetectors, light-emitting diodes, and nanoelectronics.

Adsorption of SF6 Decomposed Products on ZnO-Modified C3N: A Theoretical Study

SF₆, as an outstanding insulation medium, is widely used in the high-voltage insulation devices, guaranteeing the safe operation of the power system. Nevertheless, the inevitable partial discharge in a long-running device causes the decomposition of SF₆ and deteriorates its insulation performance. In this work, DFT calculations were performed to study the adsorbing and sensing properties of ZnO-modified C₃N (ZnO-C₃N) nanosheet towards SF₆ decomposed products, in order to propose a novel nano-candidate for evaluating the operation status of SF₆ insulation devises. We first investigated the structure of ZnO-C₃N monolayer and then simulated its adsorption behaviour upon four typical SF₆ decomposed species, namely H₂S, SO₂, SOF₂, and SO₂F₂. It is found that the ZnO-C₃N monolayer can exhibit desirable reactivity and sensitivity on SO₂, SOF₂, and SO₂F₂, leading to the intense deformation of gas molecules and large adsorption energies. These consequences allow the potential application of gas adsorbent based on ZnO-C₃N monolayer for removing impurity gases from SF₆ insulation equipment. According to the analysis, it is supposed that ZnO-C₃N monolayer is qualified to be used in maintaining insulation strength and ensuring the safe operation of power system.