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As the semiconductor devices of integrated circuits approach the physical limitations of scaling, alternative transistor and memory designs are needed to achieve improvements in speed, density, and power consumption. We report on a transistor that uses an embedded tunneling field-effect transistor for charging and discharging the semi-floating gate. This transistor operates at low voltages (≤2.0 volts), with a large threshold voltage window of 3.1 volts, and can achieve ultra-high-speed writing operations (on time scales of ~1 nanosecond). A linear dependence of drain current on light intensity was observed when the transistor was exposed to light, so possible applications include image sensing with high density and performance.

The topological three-dimensional Dirac semimetal Cd3As2 has drawn great attention for the novel physics and promising applications in optoelectronic devices operating in the infrared and THz regimes. Among the extensive studies in the past

The exciton effect in two-dimensional (2D) transition metal dichalcogenides (TMDs) plays a dominating role in describing the optical and optoelectronic properties. However, the interplay between the excitons and free carriers has not yet been understood upon photoexcitation in 2D TMDs. Here, we first present a study of the dynamical interplay of excitons and unbound electron–hole pairs using time-resolved terahertz (THz) spectroscopy (TRTS) in a few-layer WS2 laminate. Our experimental results demonstrate that the Auger recombination is observed in the relaxation process of the mobile charge carriers rather than that of excitons upon photoexcitation. The transient complex THz photoconductivity spectroscopy of WS2 is well described by the Drude–Lorentz model of free carriers modulated by the exciton polarization field. Our results provide a comprehensive understanding of nonequilibrium carrier kinetics (both excitons and free carriers) in WS2 laminate, and should be applicable to other 2D systems.

Temperature-induced spin reorientation transition in NdFeO3 single crystal is studied by terahertz time-domain spectroscopy in the temperature range from 50 K to 290 K. Following the resonant excitation of quasi-antiferromagnetic (AF) mode, the nature of temperature dependence of emission from AF-mode is investigated systematically in the spin reorientation temperature interval. The emission frequency is observed at 0.485 THz for both Γ4 and Γ24 phases, and it shifts abruptly to 0.456 THz (around 110 K) corresponding to Γ2 phase. The evolution of vector G is obtained from the temperature-dependent polarization changes of the AF-mode excitation. Our results demonstrate that the polarized terahertz time-domain spectroscopy is a sensitive tool to explore the dynamical spin reorientation transition in RFeO3 crystals, and the terahertz magnetic pulse shows potential application for non-thermally manipulating ultrafast spin reorientation.

The atomically thin layered transition metal dichalcogenide (TMDCs) PtSe2 is a new emerging two-dimension (2D) material, which has a transition from indirect-gap semiconductor to semimetal with increasing thickness. Defects in 2D TMDCs are very ubiquitous and play a crucial role in understanding many electronics and optoelectronics in TMDCs. In this article, PtSe2 films with different thickness are obtained by selenizing the variously thick Pt films. Extrapolation of the onset absorption from the visible-infrared spectrum demonstrates that the selenization of 1 and 3 nm Pt films shows semiconductor-like character, while those of thick Pt films (with thickness of 10 and 15 nm) show metallic behavior. The transient absorption (TA) spectroscopy reveals that all films show immediately photobleaching signals after photoexcitation at 800 nm, and the subsequent relaxation process shows strongly thickness dependence. The thinnest film shows biexponential relaxation with typical time constants of 1.28 and 101.2 ps. In contrast, the photobleaching signals are developed into photoinduced absorption signals in thicker films, and the absorption magnitude increases with the thickness of the films. The optical pump and terahertz (THz) probe spectroscopy reveals that all samples show positive photoconductivity after photoexcitation of 800 nm, the subsequent recovery is completed within 2.0 ps, and the recovery time constant decreases with the increase of the films’ thickness. Our TA and THz spectroscopy results reveal that the defect states of the films play dominated role in the relaxation of photocarrier after photoexcitation, and edge-site states are inferred to make dominated contributions to the defect states in the selenization of platinum films.

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Ferroelectric vs. structural properties of large-distance sputtered epitaxial LSMO/PZT heterostructures AIP Advances 2, 032184 (2012) Magnetron-sputter deposition of high-indium-content n-AlInN thin film on p-Si(001) substrate for photovoltaic applications J. Appl. Phys. 112, 063114 (2012) Effect of MgO spacer and annealing on interface and magnetic properties of ion beam sputtered NiFe/Mg/MgO/CoFe layer structures J. Appl. Phys. 112, 063906 (2012) Reactive sputter deposition of pyrite structure transition metal disulfide thin films: Microstructure, transport, and magnetism J. Appl. Phys. 112, 054328 (2012) Strong free-carrier electro-optic response of sputtered ZnO films