Magnetic-Proximity-Induced Efficient Charge-to-Spin Conversion in Large-Area PtSe2/Ni80Fe20 Heterostructures

As a topological Dirac semimetal with controllable spin-orbit coupling and conductivity, PtSe2, a transition-metal dichalcogenide, is a promising material for several applications, from optoelectrics to sensors. However, its potential for spintronics applications has yet to be explored. In this work, we demonstrate that the PtSe2/Ni80Fe20 heterostructure can generate large damping-like current-induced spin-orbit torques (SOT), despite the absence of spin-splitting in bulk PtSe2. The efficiency of charge-to-spin conversion is found to be -0.1 ± 0.02 nm-1 in PtSe2/Ni80Fe20, which is 3 times that of the control sample, Ni80Fe20/Pt. Our band structure calculations show that the SOT due to PtSe2 arises from an unexpectedly large spin splitting in the interfacial region of PtSe2 introduced by the proximity magnetic field of the Ni80Fe20 layer. Our results open up the possibilities of using large-area PtSe2 for energy-efficient nanoscale devices by utilizing proximity-induced SOT.

Self-powered, low-noise and high-speed nanolayered MoSe2/p-GaN heterojunction photodetector from ultraviolet to near-infrared wavelengths

Integration of nanolayered metal chalcogenides with wide-bandgap semiconductors forming pn heterojunction leads to the way of high-performance photodetection. This work demonstrates the fabrication of a few nanometer thick Molybdenum diselenide (MoSe₂)/Mg-doped Gallium Nitride (p-GaN) heterostructure for light detection purposes. The device exhibits low noise broadband spectral response from ultraviolet to near-infrared range (300-950 nm). The band-alignment and the charge transfer at the MoSe₂/p-GaN interface promote self-powered photodetection with high photocurrent to dark current ratio of 2000 and 1000 at 365 nm and 640 nm, respectively. A high responsivity of 130 A W^-1, detectivity of 4.8 × 10¹⁰Jones, and low noise equivalent power of 18 fW/Hz^1/2at 365 nm is achieved at an applied bias of 1 V. Moreover, the transient measurements reveal a fast rise/fall time of 407/710μsec for the fabricated device. These outcomes exemplify the viability of MoSe₂/p-GaN heterostructure for high-speed and low-noise broadband photodetector applications.

Bilayer MoS2 on silicon for higher terahertz amplitude modulation

The terahertz (THz) amplitude modulation has been experimentally demonstrated by employing bilayer molybdenum disulfide (MoS2) on high-resistivity silicon (Si). The Raman spectroscopy and x-ray photoelectron spectra confirm the formation of bilayer MoS2 film. The THz transmission measurements are carried out using a continuous wave (CW) frequency-domain THz system. This reveals the higher modulation depth covering wide THz spectra of 0.1–1 THz at low optical pumping power. The modulation depth up to 72.3% at 0.1 THz and 62.8% at 0.9 THz under low power optical excitation is achieved. After annealing, the strong built-in electric field is induced at the MoS2–Si interface due to p-type doping in MoS2. This improves modulation depth to 86.4% and 79.7%, respectively. The finite-difference time-domain (FDTD) based numerical simulations match well with the experimental results. The higher modulation depth at low optical power, broadband response, low insertion losses, and simplicity in the design are the key attributes of this THz modulator.

Low-noise, high-detectivity, polarization-sensitive, room-temperature infrared photodetectors based on Ge quantum dot-decorated Si-on-insulator nanowire field-effect transistors

A CMOS-compatible infrared (IR; 1200-1700 nm) detector based on Ge quantum dots (QDs) decorated on a single Si-nanowire channel on a silicon-on-insulator (SOI) platform with a superior detectivity at room temperature is presented. The spectral response of a single nanowire device measured in a back-gated field-effect transistor geometry displays a very high value of peak detectivity ∼9.33 × 10¹¹Jones at ∼1500 nm with a relatively low dark current (∼20 pA), which is attributed to the fully depleted Si nanowire channel on SOI substrates. The noise power spectrum of the devices exhibits a1/fγ,with the exponent,γshowing two different values of 0.9 and 1.8 owing to mobility fluctuations and generation-recombination of carriers, respectively. Ge QD-decorated nanowire devices exhibit a novel polarization anisotropy with a remarkably high photoconductive gain of ∼10⁴. The superior performance of a Ge QDs/Si nanowire phototransistor in IR wavelengths is potentially attractive to integrate electro-optical devices into Si for on-chip optical communications.