Gray Arsenic Research Articles

Evidence of Higher Order Phonon Anharmonicity in Gray Arsenic Crystal.

Phonons play a key role in the heat transport process of quantum materials. The understanding of thermal behaviors of phonons will be beneficial for designing modern electronic devices. In this study, we utilize specific heat, Raman spectroscopy, and first-principles calculations combined with the phonon Boltzmann transport equation to explore the thermal transport of gray arsenic. Our specific heat data indicate the presence of the phonon anharmonicity at high temperature. This is further supported by temperature-dependent Raman data showing evident phonon softening and line width broadening. More interestingly, from the analysis of temperature-dependent Raman modes, we found that the four-phonon scattering process is indispensable for interpreting the line width broadening at high temperatures. Moreover, we evaluate the importance of the four-phonon scattering process in the heat transport of gray arsenic using the moment tensor potential method. Our work sheds light on the importance of a higher order phonon scattering process in heat transport of the materials with moderate thermal conductivity.

Structural and electric transport properties of gray arsenic under high pressure

Structural and electric transport properties of gray arsenic under high pressure

Quasiparticle interference of the topological surface state on gray arsenic

Quasiparticle interference of the topological surface state on gray arsenic

Thermodynamic Origins of Structural Metastability in Two-Dimensional Black Arsenic.

Two-dimensional (2D) materials have aroused considerable research interest owing to their potential applications in nanoelectronics and optoelectronics. Thermodynamic stability of 2D structures inevitably affects the performance and power consumption of the fabricated nanodevices. Black arsenic (b-As), as a cousin of black phosphorus, has presented extremely high anisotropy in physical properties. However, systematic research on structural stability of b-As is still lacking. Herein, we demonstrated the detailed analysis on structural metastability of the natural b-As, and determined its existence conditions in terms of two essential thermodynamic variables, hydrostatic pressure and temperature. Our results confirmed that b-As can survive only below 0.7 GPa, and then irreversibly transforms to gray arsenic, consistent with our theoretical calculations. Furthermore, a thermal annealing strategy was developed to precisely control the thickness of the b-As flake, and it sublimates at 300 °C. These results could pave the way for 2D b-As in many promising applications.

Thermal Conductivity of Buckled and Puckered Arsenene: An Equilibrium Molecular Dynamics (EMD) Simulation

This study aims to calculate the thermal conductivity of buckled and puckered arsene using Molecular Dynamics simulation through Large-scale Atomic/Molecular Massively Parallel Simulation (LAMMPS). Arsenene is the monolayer of arsenic, that belongs to one of its allotropes, the gray metallic arsenic. The temperature varied from 100K, 300K, 500K, and 700K with a fixed dimension of 10nm x 50nm. Also, the length of the material varied from 10nm, 20nm, and 30nm. 40nm and 50nm at a fixed temperature of 300 K with constant width of 10nm. Results show that the main contributor to the increase of thermal conductivity is due to the phonon means free path. As the length increases, the thermal conductivity also increases because of its long mean free path. Moreover, the decreasing thermal conductivity as to the increase in temperature is due to phonon mean free path shrinking, resulting in a reduction in thermal conductivity. At room temperature, the thermal conductivity of buckled and puckered arsenene is found to be 1.8 W/mK and 1.3 W/mK, respectively. This study will provide fresh insight into the thermal properties of buckled and puckered arsenene, which will be useful for nanoelectronics applications.

From a nanoparticular solid-state material to molecular organo-f-element-polyarsenides.

A convenient pathway to new molecular organo-lanthanide-polyarsenides in general and to a f-element complex with the largest polyarsenide ligand in detail is reported. For this purpose, the activation of the solid state material As0nano (nanoscale gray arsenic) by the multi electron reducing agents [K(18-crown-6)][(Ln+II)2(μ-η6:η6-C6H6)] (Ln = La, Ce, Cp′′ = 1,3-bis(trimethylsilyl)cyclopentadienyl anion) and [K(18-crown-6)]2[(Ln+II)2(μ-η6:η6-C6H6)] (Ln = Ce, Nd) is shown. These non-classical divalent lanthanide compounds were used as three and four electron reducing agents where the product formation can be directed by variation of the applied reactant. The obtained Zintl anions As33−, As73−, and As144− were previously not accessible in molecular 4f-element chemistry. Additionally, the corresponding compounds with As144−-moieties represent the largest organo-lanthanide-polyarsenides known to date.

Deterministic Transfer of Large-Scale β-Phase Arsenic on Fiber End Cap for Near-Infrared Ultrafast Pulse Generation

Gray arsenic (β-phase) has aroused great attention in photonics and electronics applications, as a novel family member of two-dimensional (2D) elemental crystals of group-VA. Here, β-phase arsenic (β-As) bulk crystals were synthesized via the chemical vapor transport (CVT) method. Meanwhile, large-scale β-As nanoflake was transformed using the polydimethylsiloxane (PDMS)-assisted dry transfer method and was placed on the end cap of optical fiber with high coverage over the core area. Moreover, the β-As was used as a saturable absorber in ytterbium-doped fiber ring cavity resonance, and we demonstrated near-infrared ultrafast pulse fiber laser with the central wavelength, repetition rate, and signal-to-noise ratio (SNR) of 1,037.3 nm, 0.6 MHz, and 67.7 dB, respectively. This research demonstrates a 2D material small area deterministic transfer method and promotes the potential application of group-VA crystals in near-infrared ultrafast laser generation.

Growth of black arsenic phosphorus thin films and its application for field-effect transistors

Black arsenic phosphorus single crystals were grown using a short-way transport technique resulting in crystals up to 12 × 110 and ranging from 200 nm to 2 thick. The reaction conditions require tin, tin (IV) iodide, gray arsenic, and red phosphorus placed in an evacuated quartz ampule and ramped up to a maximum temperature of 630 °C. The crystal structure and elemental composition were characterized using Raman spectroscopy, x-ray diffraction, and x-ray photoelectron spectroscopy, cross-sectional transmission microscopy, and electron backscatter diffraction. The data provides valuable insight into the growth mechanism. A previously developed b-P thin film growth technique can be adapted to b-AsP film growth with slight modifications to the reaction duration and reactant mass ratios. Devices fabricated from exfoliated bulk-b-AsP grown in the same reaction condition as the thin film growth process are characterized, showing an on-off current ratio of 102, a threshold voltage of −60 V, and a peak field-effect hole mobility of 23 cm2 V−1 s−1 at V d = −0.9 V and V g = −60 V.

Bandgap opening in layered gray arsenic alloy

As an essential member of group-V layered materials, gray arsenic (g-As) has recently begun to draw researchers’ attention due to fantastic physical properties predicted by theoretical calculation. However, g-As presents semimetal behavior as the thickness exceeds bilayers, which hinders its further device applications, such as in logic electronics. Herein, we report the growth of high quality gray arsenic–phosphorus–tin (g-AsPSn) alloys via a simple one-step chemical vapor transport process. The as-grown g-AsPSn alloy remains the same layered rhombohedral structure as g-As, while the g-AsPSn alloy shows an opened bandgap compared with g-As. Infrared absorption and photoluminescence spectra reveal a narrow optical bandgap of 0.2 eV. A field effect transistor based on few-layer g-AsPSn alloy flakes shows a typical p-type semiconductor behavior and a relatively high mobility of ∼66 cm2 V−1 S−1 under ambient conditions. It can be envisioned that the synthesized two-dimensional layered narrow-gap g-AsPSn alloy presents considerable potential applications in electronics and infrared optoelectronics.

Signature of Dirac semimetal states in gray arsenic studied by de Haas–van Alphen and Shubnikov–de Haas quantum oscillations

We report systematically studies of de Haas--van Alphen (dHvA) and Shubnikov--de Haas (SdH) quantum oscillations under high magnetic fields on gray arsenic, which has been suggested to be a topological insulator by first-principles calculations and angle-resolved photoemission spectroscopy. We observed large unsaturated magnetoresistance and pronounced quantum oscillations in two methods. By analysis of these quantum oscillation spectra, we obtained two major frequency branches around 3.8--18 and 153--162 T, and the light effective quasiparticle mass and nontrivial Berry phase. These results suggest that bulk crystals of gray arsenic may belong to the category of topological Dirac semimetals rather than topological insulators.

Stability and Phase Transition of Metastable Black Arsenic under High Pressure.

Black arsenic (bAs) is a metastable phase of arsenic that has attracted increasing interest owing to its layered structure, tunable band gap, high carrier mobility, and large on/off ratio. Here, we systematically investigated the high-pressure behaviors of bAs up to ∼14 GPa. A phase transition from bAs to gray arsenic (gAs) occurred at critical pressure of 3.48 GPa, and the bAs and gAs coexisted between 3.48 and 5.37 GPa before bAs completely converted to gAs above 5.37 GPa. The structure was reversible for bAs after pressure was released from about 1-3 GPa, indicating the stability of bAs at pressures less than the critical pressure. At pressures above 5.37 GPa, bAs transformed to gAs and remained gAs after pressure was released. Molecular dynamics (MD) simulation was performed to explain the phase transition mechanism. This work provides insights into the phase stability and phase transition of metastable bAs under high pressure.

Coordination chemistry of 2D and layered gray arsenic: photochemical functionalization with chromium hexacarbonyl

The functionalization of layered materials is one of the current challenges in material science. Exfoliated rhombohedral (gray) arsenic represents a promising layered material for the fabrication of electronic devices and sensors; however, synthetic protocols for tuning its properties or protecting the surface by covalent functionalization are not known. In this communication, we present its covalent functionalization accompanied by the exfoliation of rhombohedral arsenic in the presence of ultraviolet light irradiation and chromium hexacarbonyl. During this modification, the arsenic atoms act as ligands to the chromium metal center. We believe that this study provides a promising approach for the modification of rhombohedral few-layer arsenene and enables its application in various fields, including electronic devices, sensors, and energy devices.

Structural and electronic properties of the V-V compounds isoelectronic to GaN and isostructural to gray arsenic

The III–V binary compound semiconductors such as GaN, GaP, InN and InP have extensive applications in various optoelectronic, microwave and power-electronic devices. Using first-principles calculation, we systematically studied the structural and electronic properties of the V-V binary compounds (BiN, BiP, SbN and SbP) that are isoelectronic to GaN, GaP, InN and InP if Bi and Sb are in the +3 valence state. Interestingly, we found that the ground-state structures of BiP, SbN and SbP have the R-3m symmetry and are isostructural to the layered structure of gray arsenic, whereas BiN prefers a different ground-state structure with the C2 symmetry. Electronic structure calculations showed that the bulk BiN is a narrow bandgap semiconductor for its bandgap is about 0.2 eV. In contrast, BiP, SbN and SbP are metallic. The layered ground-state structure of the V-V binary compounds motivates us to study the electronic properties of their few-layer structures. As the structure becomes monolayer, their bandgaps increase significantly and are all in the range from about 1 eV to 1.7 eV, which are comparative to the bandgap of the monolayer gray arsenic. The monolayer BiP, SbN and SbP have indirect bandgaps, and they show a semiconductor-metal transition as the number of layers increase. Interestingly, the monolayer BiP has the largest splitting (350 meV) of the CBM valley, and thus may have potential application in novel spintronics and valleytronics devices.

Bulk β-Te to few layered β-tellurenes: indirect to direct band-Gap transitions showing semiconducting property

Herein we report a prediction of a highly kinetic stable layered structure of tellurium (namely, bulk β-Te), which is similar to these layered bulk materials such as graphite, black phosphorus, and gray arsenic. Bulk β-Te turns out to be a semiconductor that has a band gap of 0.325 eV (HSE06: 0.605 eV), based on first-principles calculations. Moreover, the single-layer form of the bulk β-Te, called β-tellurene, is predicted to have a high stability. When the bulk β-Te is thinned to one atomic layer, an indirect semiconductor of band gap is changed to 1.265 eV (HSE06: 1.932 eV) with a very high kinetic stability. Interestingly, an increase of the number of the β-tellurene layers from one to three is accompanied by a shift from an indirect to direct band gap. Furthermore, the effective carrier masses, the optical properties and phonon modes of few-layer β-tellurenes are characterized. Few-layer β-tellurenes strongly absorb the ultraviolet and blue-violet visible lights. The dramatic changes in the electronic structure and excellent photo absorptivities are expected to pave the way for high speed ultrathin transistors, as well as optoelectronic devices working in the UV or blue-green visible regions.

First-principles prediction of stabilities and instabilities of compounds and alloys in the ternary B-As-P system

We examine the thermodynamic stability of compounds and alloys in the ternary B-As-P system theoretically using first-principles calculations. We demonstrate that the icosahedral ${\mathrm{B}}_{12}{\mathrm{As}}_{2}$ is the only stable compound in the binary B-As system, while the zinc-blende BAs is thermodynamically unstable with respect to ${\mathrm{B}}_{12}{\mathrm{As}}_{2}$ and the pure arsenic phase at 0 K, and increasingly so at higher temperature, suggesting that BAs may merely exist as a metastable phase. On the contrary, in the binary B-P system, both zinc-blende BP and icosahedral ${\mathrm{B}}_{12}{\mathrm{P}}_{2}$ are predicted to be stable. As for the binary As-P system, ${\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}$ disordered alloys are predicted at elevated temperature---for example, a disordered solid solution of up to $\ensuremath{\sim}75$ at.% As in black phosphorus as well as a small solubility of $\ensuremath{\sim}1$ at.% P in gray arsenic at $T=750$ K, together with the presence of miscibility gaps. The calculated large solubility of As in black phosphorus explains the experimental syntheses of black-phosphorus-type ${\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}$ alloys with tunable compositions, recently reported in the literature. We investigate the phase stabilities in the ternary B-As-P system and demonstrate a high tendency for a formation of alloys in the icosahedral ${\mathrm{B}}_{12}$(${\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}$)${}_{2}$ structure by intermixing of As and P atoms at the diatomic chain sites. The phase diagram displays noticeable mutual solubility of the icosahedral subpnictides in each other even at room temperature as well as a closure of a pseudobinary miscibility gap around 900 K. As for pseudobinary ${\mathrm{BAs}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}$ alloys, only a tiny amount of BAs is predicted to be able to dissolve in BP to form the ${\mathrm{BAs}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}$ disordered alloys at elevated temperature. For example, less than 5% of BAs can dissolve in BP at $T=1000$ K. The small solubility limit of BAs in BP is attributed to the thermodynamic instability of BAs with respect to ${\mathrm{B}}_{12}{\mathrm{As}}_{2}$ and As.

Magnetotransport properties in a compensated semimetal gray arsenic

We report the observation of an extremely large magnetoresistance (up to 15 000 000% at 1.8 K in a magnetic field of 9 T) in a simple chemical element, gray arsenic, in which the magnitude of the magnetoresistance increases as approximately the square of the magnetic field strength without any signs of saturation. The Hall-effect study confirms that gray arsenic is a nearly perfect ``compensated semimetal,'' with a small concentration of very mobile carriers, which lead to an extremely large magnetoresistance. The analysis of Shubnikov--de Haas oscillations reveals a nontrivial \ensuremath{\pi} Berry phase, a strong signature of Dirac fermions with three-dimensional dispersion. Furthermore, in the presence of parallel magnetic and electric fields, a weak antilocalization effect and a pronounced negative longitudinal magnetoresistance, which may be linked to novel topological states, are also observed. These findings which uncover the material's basis in gray arsenic not only open avenues in spintronics and magnetic sensor applications but also provide more platforms to study topological materials.

Prediction on the light-assisted exfoliation of multilayered arsenene by the photo-isomerization of azobenzene.

The exfoliation of gray arsenic into single- or few-layered arsenene is a challenge of utmost importance. We propose here that the conformational change in the photo-isomerization of azobenzene-based photochromes might be used to promote the exfoliation of multilayered arsenene. Our density functional theory calculations show that the trans-to-cis conformational change can lead to an increase of the adjacent interlayer distance of arsenene from 6.59 Å to 11.07 Å. Starting from the transition state, the azobenzene molecule can be isomerized into the more stable trans form based on further ab initio molecular dynamics simulations. Reactive molecular dynamics simulations also show that about a 5 Å interlayer distance change can be induced by the cis-to-trans photo-isomerization of an azobenzene-OC10H21 molecule. The computational results may inspire the experimental enthusiasm for light-driven synthesis of single or few-layered arsenene.

Optical Identification of Topological Defect Types in Monolayer Arsenene by First-Principles Calculation

Recent theoretical research has demonstrated that a new two-dimensional material, the monolayer of gray arsenic (arsenene), can respond to the blue and ultraviolet light leading to possible optoelectronic applications. However, some topological defects often affect various properties of arsenene. Here we theoretically investigate the arsenene with monovacancy (MV), divacancy (DV), and Stone–Wales (SW) defects. Three kinds of MVs are identified and the reconstructed structures of DV and SW defects are confirmed. The dynamical stability, rearrangement, and migration for these defects are investigated in detail. Optical spectral calculations indicate that the MVs enhance optical transitions in the forbidden bands of arsenene and two new characteristic peaks appear in the dielectric and absorption spectra. However, there is only one new peak in the spectrum induced by DV and SW defects. Calculations of band structures indicate that the MV induces two defect bands in the forbidden bands of pristine arsenene, w...

A first-principles study of transition metal doped arsenene

Arsenene is the monolayer gray arsenic which was proposed only recently. Herein, we study the magnetic properties and electronic structures of transition-metal-doped arsenene by using first-principles calculations. Three doping concentrations are considered in our investigation. The results show that not all 3d transition metal (TM) atoms can induce the magnetic state in arsenene. Moreover, the doping concentration hardly affects the magnetic moment except for Fe- and Ni-doped systems. We believe, in particular, that the magnetism is dominantly controlled by the doping TM atoms, and no significant contributions are induced, even by their nearest arsenic atoms. In addition, the multiplicate electronic structures of TM-doped arsenene, such as semiconductor, metal and half-metal, have also been revealed and discussed in this work, which may provide a new attention for the doped arsenene nanosheets.

Modulating the electronic properties of monolayer MoS2 through heterostructure with monolayer gray arsenic

Two-dimensional layered materials attract much attention due to their outstanding intrinsic properties and wide applications. In this work, the mechanical and electronic properties of monolayer MoS2 on monolayer gray arsenic (g-As) substrates are studied by first-principles calculations. Results indicate that both g-As and MoS2 undergo small corrugations when monolayer MoS2 is bonded to g-As. The lowest binding energies (~−0.05eV) and the electronic structures are almost independent of the atomic arrangement. But the indirect band gap of g-As/MoS2 heterostructure enlarges with increasing the interlayer distance. Moreover, the valence band maximum consists of π-like states rather than σ states upon the formation of g-As/MoS2 heterostructures. Interestingly, complete electron-hole separation is found in the g-As/MoS2 heterostructures, which can facilitate the application of MoS2 on photoelectric device. In addition, the work function of monolayer MoS2 shifts down upon the g-As/MoS2 heterostructures formation since a certain charge transfer is found between MoS2 and g-As even though the interlayer interaction is very weak. Our findings provide a detailed understanding of the nature physical properties of g-As/MoS2 heterostructures, and suggest a simple way to fabricate and improve the application of monolayer MoS2 in nanodevices.