Search

Modulating the electronic properties of VSi2N4 with high Curie temperature to realize an ideal half-metal is appealing towards spintronic applications. Here, by using first-principles calculations, we propose alloying the VSi2N4 monolayer via substitutive doping of transition metal atoms (Sc–Ni, Y–Mo) at the V site. We find that the transition metal atom (except the Ni atom) doped VSi2N4 systems have dynamical and thermal stability. The doping of transition metal atoms can modulate the electronic structure of VSi2N4. Especially, the doping of the Sc/Y atom transforms VSi2N4 into an ideal half-metal, while the doping of the Ti/Zr atom leads to a half-semiconductor. For the half-metallic Sc- and Y-doped VSi2N4 devices, the magnetoresistance ratios up to 1010% and 108% are achieved, respectively. When the magnetization direction is parallel, the spin filtering efficiency of both devices reaches up to 100% at a low bias voltage, independent of the bias direction. When the magnetization direction is antiparallel, both show a dual spin filtering effect. Our findings offer a theoretical reference for modulating the electronic properties of two-dimensional materials towards spintronic applications. [ABSTRACT FROM AUTHOR]

Field-effect-transistor (FET)-type gas sensors have attracted a surge of research interest due to their low power dissipation and exceptional sensitivity. However, theoretical explorations into their sensing capability and underlying mechanism remain scarce. Herein, taking the pure and defective WTe2 monolayers as the sensing platforms, we systematically investigate the sensing characteristics and working principles of FET-type gas sensors in response to various hazardous gases, including SO2, CO, NO, NH3, and NO2, using first-principles calculations and statistical thermodynamic modeling. Our findings reveal that the pure WTe2-based FET-type gas sensor, operating at zero gate voltage, shows remarkably high sensitivity and reusability for NO2 detection, achieving 96% sensitivity at a low concentration of 20 ppb. Our research demonstrates that the introduction of Te-vacancies serves as a highly efficient strategy for enhancing the sensitivity of the gas sensor towards all tested toxic gases, while ensuring its reusability. Applying a gate voltage to the pure WTe2-based FET-type gas sensor further improves its sensitivity to NO2, surpassing 90% within the whole bias range, and reaching 97% under the gate voltage of 3 V. This improvement is attributed to the upward shift of the conduction bands under a positive gate voltage with respect to the chemical potential of the source, which increases the electron barrier and decreases the conductance. Our research offers a promising approach for achieving ultra-sensitive and recyclable detection of toxic gases at ppb-level concentration. [ABSTRACT FROM AUTHOR]

We study the regulation of the electronic and spin transport properties of the WGe2N4 monolayer by adsorbing 4d transition metal atoms (Y–Cd) using density functional theory combined with non-equilibrium Green's function. It is found that the adsorption of transition metal atoms (except Pd, Ag and Cd atoms) can introduce a magnetic moment into the WGe2N4 monolayer. Among the transition metal atoms, the adsorption of Nb and Rh atoms transforms WGe2N4 from a semiconductor to a half-metal and a highly spin-polarized semiconductor, respectively. The half-metallic Nb-adsorbed WGe2N4 system is selected to investigate the spin transport properties, and a high magnetoresistance ratio of 107% is achieved. In both parallel and antiparallel magnetization configurations, the spin filtering efficiency reaches close to 100% in the whole bias range, and the antiparallel magnetization configuration exhibits a dual spin filtering effect with a rectification ratio of up to 104. Our study predicts that the adsorption of 4d transition metal heteroatoms is an effective method to regulate the electronic and magnetic properties of WGe2N4 towards high-performance spintronic devices. [ABSTRACT FROM AUTHOR]

Since the diode is one of the common electronic components in modern semiconductor electronics, realizing diodes with superior and controllable rectifying behaviors based on two-dimensional materials is important for next-generation electronics. Herein, gate-tunable in-plane (IP) and out-of-plane (OP) heterojunction diodes composed of the semiconductive WGe2N4 and metallic TaSi2N4 are reported based on first-principles calculations. The interfacial properties and rectifying characteristics of the IP and OP heterojunction diodes are systematically investigated. The results demonstrate that the Schottky barrier in the IP diode is much larger than that in the OP diode, resulting in a smaller current of the IP diode. The IP diode exhibits a much higher rectification ratio of 107 than the OP diode of 104 under the zero gate voltage. Noticeably, the rectifying behaviors of both diodes can be effectively modulated by the gate voltages. The positive gate voltages increase the current of IP and OP Schottky diodes and improve the rectification ratio to 109 and 105, respectively. Moreover, the negative gate voltage makes the rectifying direction of the OP Schottky diode reverse with a rectification ratio larger than 106. Our results provide a reference for designing superior two-dimensional diodes with controllable rectifying behaviors and pave the way for the design of logic devices in the future. [ABSTRACT FROM AUTHOR]

Searching for eligible two-dimensional (2D) semiconductors to fabricate high-performance (HP) short-channel field-effect transistors (FETs) at the nanoscale is essential toward the continuous miniaturization of devices. Herein, we predict the 2D Janus WSi2P2As2 semiconductor and propose it as a qualified channel material for sub-5 nm FETs by using first-principles calculations. The results demonstrate that the monolayer Janus WSi2P2As2 is a 2D semiconducting nanofilm with a band gap of 0.83 eV, a hole mobility of 490 cm2 V–1 s–1 in the armchair direction, and an out-of-plane polarization. Benefiting from these outstanding intrinsic characteristics, the performance of the 5 and 3 nm gate-length WSi2P2As2 FETs can fulfill the International Technology Roadmap for Semiconductors for HP standards after employing optimizing strategies, including underlap structure, dielectric project, and cold source. Our results promote the development of new 2D nanomaterials and device architectures for designing HP short-channel FETs. [ABSTRACT FROM AUTHOR]

Realizing Ohmic contact is essential but challenging in the development of high‐performance 2D‐material‐based electronics. Here, using first‐principles calculations, the interfacial properties between 2D metallic M3C2T2 (M = Ti, Zr, Hf; T = O, F, OH) and 2D semiconductors are comprehensively investigated, taking group ΙV monochalcogenides in blue‐phosphorene phase as example, and the performance of short‐channel field‐effect transistors (FETs) with M3C2(OH)2 electrode is studied. The band alignments and the interface dipole analysis demonstrate that the M3C2(OH)2 and Ti3C2O2 electrodes form van der Waals interaction with the group ΙV monochalcogenides, conductive to weakening the Fermi level pinning and forming desired Ohmic contacts. Moreover, owing to the large work function of the Ti3C2O2, it realizes p‐type Ohmic contacts with 2D semiconductors. In addition, due to the favorable Ohmic contacts, the on/off ratio of the 5 nm gate‐length Zr3C2(OH)2–GeTe FET is around 105. Moreover, for the 3 nm gate‐length Zr3C2(OH)2–SnTe FET after adopting optimizing strategies, the on/off ratio increases from 102 to 106, and the subthreshold slope decreases from 125 mV dec‐1 to 58 mV dec‐1 below the thermionic limit (60 mV dec‐1). The results provide a theoretical guidance for achieving the intrinsic n‐type and p‐type Ohmic contacts and high‐performance FETs in 2D nanoelectronics. [ABSTRACT FROM AUTHOR]