An official website of the United States government
Abstract Theoretical and experimental investigations of various exfoliated samples taken from layered In4Se3crystals are performed. In spite of the ionic character of interlayer interactions in In4Se3and hence much higher calculated cleavage energies compared to graphite, it is possible to produce few‐nanometer‐thick flakes of In4Se3by mechanical exfoliation of its bulk crystals. The In4Se3flakes exfoliated on Si/SiO2have anisotropic electronic properties and exhibit field‐effect electron mobilities of about 50 cm2 V−1 s−1at room temperature, which are comparable with other popular transition metal chalcogenide (TMC) electronic materials, such as MoS2and TiS3. In4Se3devices exhibit a visible range photoresponse on a timescale of less than 30 ms. The photoresponse depends on the polarization of the excitation light consistent with symmetry‐dependent band structure calculations for the most expectedaccleavage plane. These results demonstrate that mechanical exfoliation of layered ionic In4Se3crystals is possible, while the fast anisotropic photoresponse makes In4Se3a competitive electronic material, in the TMC family, for emerging optoelectronic device applications.
more »
« less
This content will become publicly available on August 2, 2025
Bulk photovoltaic effect and high mobility in the polar 2D semiconductor SnP 2 Se 6
The growth of layered 2D compounds is a key ingredient in finding new phenomena in quantum materials, optoelectronics, and energy conversion. Here, we report SnP2Se6, a van der Waals chiral (R3 space group) semiconductor with an indirect bandgap of 1.36 to 1.41 electron volts. Exfoliated SnP2Se6flakes are integrated into high-performance field-effect transistors with electron mobilities >100 cm2/Vs and on/off ratios >106at room temperature. Upon excitation at a wavelength of 515.6 nanometer, SnP2Se6phototransistors show high gain (>4 × 104) at low intensity (≈10−6W/cm2) and fast photoresponse (< 5 microsecond) with concurrent gain of ≈52.9 at high intensity (≈56.6 mW/cm2) at a gate voltage of 60 V across 300-nm-thick SiO2dielectric layer. The combination of high carrier mobility and the non-centrosymmetric crystal structure results in a strong intrinsic bulk photovoltaic effect; under local excitation at normal incidence at 532 nm, short circuit currents exceed 8 mA/cm2at 20.6 W/cm2.
more »
« less
- Award ID(s):
- 1929356
- PAR ID:
- 10555105
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Science Advances
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 10
- Issue:
- 31
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We report the effect of extended duration electron beam exposure on the minority carrier transport properties of 10 MeV proton irradiated (fluence ∼1014cm−2) Si-dopedβ-Ga2O3Schottky rectifiers. The diffusion length (L) of minority carriers is found to decrease with temperature from 330 nm at 21 °C to 289 nm at 120 °C, with an activation energy of ∼26 meV. This energy corresponds to the presence of shallow Si trap-levels. Extended duration electron beam exposure enhancesLfrom 330 nm to 726 nm at room temperature. The rate of increase forLis lower with increased temperature, with an activation energy of 43 meV. Finally, a brief comparison of the effect of electron injection on proton irradiated, alpha-particle irradiated and a reference Si-dopedβ-Ga2O3Schottky rectifiers is presented.more » « less
-
Abstract 2D photonic crystal (PhC) lasing from an InP nanowire array still attached to the InP substrate is demonstrated for the first time. The undoped wurtzite InP nanowire array is grown by selective area epitaxy and coated with a 10 nm thick Al2O3film to suppress atmospheric oxidation and band‐bending effects. The PhC array displays optically pumped lasing at room temperature at a pulsed threshold fluence of 14 µJ cm−2. At liquid nitrogen temperature, the array shows lasing under continuous wave excitation at a threshold intensity of 500 W cm−2. The output power of the single mode laser line reaches values of 470 µW. Rate equation calculations indicate a quality factor ofQ ≈ 1000. Investigations near threshold reveal that lasing starts from isolated islands within the pumped region before coherently merging into a single homogeneous area with increasing excitation power. This field emits a lasing mode with an average off‐normal angle of ≈6°. Single mode lasing with the nanoarray still attached to the InP substrate opens new design opportunities for electrically pumped PhC laser light sources.more » « less
-
Abstract Source/Drain extension doping is crucial for minimizing the series resistance of the ungated channel and reducing the contact resistance of field‐effect transistors (FETs) in complementary metal–oxide–semiconductor (CMOS) technology. 2D semiconductors, such as MoS2and WSe2, are promising channel materials for beyond‐silicon CMOS. A key challenge is to achieve extension doping for 2D monolayer FETs without damaging the atomically thin material. This work demonstrates extension doping with low‐resistance contacts for monolayer WSe2p‐FETs. Self‐limiting oxidation transforms a bilayer WSe2into a hetero‐bilayer of a high‐work‐function WOxSeyon a monolayer WSe2. Then, damage‐free nanolithography defines an undoped nano‐channel, preserving the high on‐current of WOxSey‐doped FETs while significantly improving their on/off ratio. The insertion of an amorphous WOxSeyinterlayer under the contacts achieves record‐low contact resistances for monolayer WSe2over a hole density range of 1012to 1013cm−2(1.2 ± 0.3 kΩ µm at 1013cm−2). The WOxSey‐doped extension exhibits a sheet resistance as low as 10 ± 1 kΩ □−1. Monolayer WSe2p‐FETs with sub‐50 nm channel lengths reach a maximum drain current of 154 µA µm−1with an on/off ratio of 107–108. These results define strategies for nanometer‐scale selective‐area doping in 2D FETs and other 2D architectures.more » « less
-
Photoelectrochemical (PEC) hydrogen generation is a promising solar energy harvesting technique to address the concerns about the ongoing energy crisis. Antimony selenide (Sb2Se3) with van der Waals‐bonded quasi‐1D (Q1D) nanoribbons, for instance, (Sb4Se6)n, has attracted considerable interest as a light absorber with Earth‐abundant elements, suitable bandgap, and a desired sunlight absorption coefficient. By tuning its anisotropic growth behavior, it is possible to achieve Sb2Se3films with nanostructured morphologies that can improve the light absorption and photogenerated charge carrier separation, eventually boosting the PEC water‐splitting performance. Herein, high‐quality Sb2Se3films with nanorod (NR) array surface morphologies are synthesized by a low‐cost, high‐yield, and scalable close‐spaced sublimation technique. By sputtering a nonprecious and scalable crystalline molybdenum sulfide (MoS2) film as a cocatalyst and a protective layer on Sb2Se3NR arrays, the fabricated core–shell structured MoS2/Sb2Se3NR PEC devices can achieve a photocurrent density as high as −10 mA cm−2at 0 VRHEin a buffered near‐neutral solution (pH 6.5) under a standard simulated air mass 1.5 solar illumination. The scalable manufacturing of nanostructured MoS2/Sb2Se3NR array thin‐film photocathode electrodes for efficient PEC water splitting to generate solar fuel is demonstrated.more » « less
