General low-temperature growth of two-dimensional nanosheets from layered and nonlayered materials.

Most of the current methods for the synthesis of two-dimensional materials (2DMs) require temperatures not compatible with traditional back-end-of-line (BEOL) processes in semiconductor industry (450 °C). Here, we report a general BiOCl-assisted chemical vapor deposition (CVD) approach for the low-temperature synthesis of 27 ultrathin 2DMs. In particular, by mixing BiOCl with selected metal powders to produce volatile intermediates, we show that ultrathin 2DMs can be produced at 280-500 °C, which are ~200-300 °C lower than the temperatures required for salt-assisted CVD processes.

Ultimate low leakage and EOT of high-dielectric using transferred metal electrode.

The increase of gate leakage current when the gate dielectric layer is thinned is a key issue for device scalability. For scaling down the integrated circuits, a thin gate dielectric layer with a low leakage current is essential. Currently, changing the dielectric layer material or enhancing the surface contact between the gate dielectric and the channel material is the most common way to reduce gate leakage current in devices.

Phase-Selective Synthesis of Ultrathin FeTe Nanoplates by Controllable Fe/Te Atom Ratio in the Growth Atmosphere.

Phase controllable synthesis of 2D materials is of significance for tuning related electrical, optical, and magnetic properties. Herein, the phase-controllable synthesis of tetragonal and hexagonal FeTe nanoplates has been realized by a rational control of the Fe/Te ratio in a chemical vapor deposition system. Using density functional theory calculations, it has been revealed that with the change of the Fe/Te ratio, the formation energy of active clusters changes, causing the phase-controllable synthesis of FeTe nanoplates.

Dual-Carbon Electrode-Based High-Energy-Density Potassium-Ion Hybrid Capacitor.

Potassium-ion hybrid capacitors (KIHCs) have attracted growing attention due to the natural abundance and low cost of potassium. However, KIHCs are still limited by sluggish redox reaction kinetics in electrodes during the accommodation of large-sized K. Herein, a starch-derived hierarchically porous nitrogen-doped carbon (SHPNC) anode and active carbon cathode were rationally designed for dual-carbon electrode-based KIHCs with high energy density.

Chemical vapor deposition and temperature-dependent Raman characterization of two-dimensional vanadium ditelluride.

Recently, ultrathin two-dimensional (2D) metallic vanadium dichalcogenides have attracted widespread attention because of the charge density wave (CDW) phase transition and possible ferromagnetism. Herein, we report the synthesis and temperature-dependent Raman characterization of the 2D vanadium ditelluride (VTe). The synthesis is done by atmospheric pressure chemical vapor deposition (APCVD) using vanadium chloride (VCl) precursor on fluorphlogopite mica, sapphire, and h-BN substrates.

Organic charge transfer complexes on graphene with ultrahigh near infrared photogain.

Photodetectors have widespread applications in fields including telecommunications, thermal imaging and bio-medical imaging. The photogating effect, arising from charge trapping at defects and/or interfaces, can have extremely high photoelectric gain which can be a benefit to high-sensitivity room temperature photodetection. Here, we introduce thin layered organic charge transfer complexes (CPXs) integrated on graphene transistors for the development of hybrid phototransistors with ultra-high photoresponsivity of ∼10 A W in the near infrared (NIR) region at room temperature.

Growth of two-dimensional materials on hexagonal boron nitride (h-BN).

With its atomically smooth surface yet no dangling bond, chemical inertness and high temperature sustainability, the insulating hexagonal boron nitride (h-BN) can be an ideal substrate for two-dimensional (2D) material growth and device measurement. In this review, research progress on the chemical growth of 2D materials on h-BN has been summarized, such as chemical vapor deposition and molecular beam epitaxy of graphene and various transition metal dichalcogenides. Further, stacking of the as-grown 2D materials relative to h-BN, thermal expansion matching between the deposited materials and h-BN, electrical property of 2D materials on h-BN have been discussed in detail.

Potential 2D Materials with Phase Transitions: Structure, Synthesis, and Device Applications.

Layered materials with phase transitions, such as charge density wave (CDW) and magnetic and dipole ordering, have potential to be exfoliated into monolayers and few-layers and then become a large and important subfamily of two-dimensional (2D) materials. Benefitting from enriched physical properties from the collective interactions, long-range ordering, and related phase transitions, as well as the atomic thickness yet having nondangling bonds on the surface, 2D phase-transition materials have vast potential for use in new-concept and functional devices. Here, potential 2D phase-transition materials with CDWs and magnetic and dipole ordering, including transition metal dichalcogenides, transition metal halides, metal thio/selenophosphates, chromium silicon/germanium tellurides, and more, are introduced.