Atomically thin van der Waals tunnel field-effect transistors and its potential for applications.

Power dissipation is a crucial problem as the packing density of transistors increases in modern integrated circuits. Tunnel field-effect transistors (TFETs), which have high energy filtering provided by band-to-band tunneling (BTBT), have been proposed as an alternative electronics architecture to decrease the energy loss in bias operation and to achieve steep switching at room temperature. Very recently, the BTBT behavior has been demonstrated in van der Waals heterostructures by using unintentionally doped semiconductors.

Reversible and Precisely Controllable p/n-Type Doping of MoTe Transistors through Electrothermal Doping.

Precisely controllable and reversible p/n-type electronic doping of molybdenum ditelluride (MoTe ) transistors is achieved by electrothermal doping (E-doping) processes. E-doping includes electrothermal annealing induced by an electric field in a vacuum chamber, which results in electron (n-type) doping and exposure to air, which induces hole (p-type) doping. The doping arises from the interaction between oxygen molecules or water vapor and defects of tellurium at the MoTe surface, and allows the accurate manipulation of p/n-type electrical doping of MoTe transistors.

Origin of Noise in Layered MoTe₂ Transistors and its Possible Use for Environmental Sensors.

Low-frequency current fluctuations are monitored and the mechanism of electric noise investigated in layered 2H-type α-molybdenum ditelluride transistors. The charge transport mechanism of electric noise in atomically thin transition-metal dichalcogenides is studied under different environments; the development of a new sensing functionality may be stimulated.

Effect of surface Si redistribution on the alignment of Ge dots grown on pit-patterned Si(001) substrates.

Thermally activated redistribution of Si surface atoms is found to be a crucial factor for the growth of aligned Ge dots on pit-patterned Si(001) substrates. A phenomenon of Si accumulation around the edge of pits significantly alters the substrate surface morphology. As the pit spacing is reduced to below 100 nm, a convex morphology developed between adjacent pits causes a chemical potential distribution that drives the Ge dots into the pits.

Low temperature and high magnetic field spectroscopic ellipsometry system.

We report on the design and implementation of a spectral ellipsometer at near-infrared wavelength (700-1000 nm) for samples placed in high magnetic fields (up to 14 T) at low temperatures (~4.2 K). The main optical components are integrated in a probe, which can be inserted into a conventional long-neck He dewar and has a very long free-space optical path (~1.

Thermally induced morphology evolution of pit-patterned Si substrate and its effect on nucleation properties of Ge dots.

We demonstrate the effect of the pre-growth heat treatment process on the nucleation properties of Ge dots grown on pit-patterned Si(001) substrates. The prefabricated 200 nm diameter pits inherently evolve into truncated inverted pyramids (TIPs) with (110) base edges and a 7°-9° sidewall slope during heat treatment; this morphology transformation is robust against variations in shape and orientation of the pit patterns. Uniform Ge dots with an areal density of 4 × 10(9) cm(-2) were obtained on the Si substrates having TIPs.

Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots.

In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states) on photoluminescence excitation (PLE) spectra of InAs quantum dots (QDs) was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T) were compared.