There is an increasing interest in harvesting photoejected hot-electrons for sensitive photodetectors, which have highly tunable detection wavelengths controlled by structural engineering rather than the classic doped semiconductors. However, the widely employed metallic nanostructures that excite surface plasmons (SPs) to enhance the photoemission of hot-electrons are usually complex with a high fabrication challenge. Here, we present a purely planar hot-electron photodetector based on Tamm plasmons (TPs) by introducing a distributed Bragg reflector integrated with hot-electron collection layers in metal/semiconductor/metal configuration. Results show that the light incidence can be strongly confined in the localized region between the top metal and the adjacent dielectric layer due to the excitation of TP resonance so that more than 87% of the light incidence can be absorbed by the top metal layer. This enables a strong and unidirectional photocurrent and a photoresponsivity that can even be higher than that of the conventional nanostructured system. Moreover, the planar TP system shows a narrow-band resonance with high tunability, good resistance against the change of the incident angle, and the possibility for extended functionalities. The proposed TP-based planar configuration significantly simplifies the conventional SP-based systems and opens the pathway for high-performance, low-cost, hot-electron photodetection.

Tellurene and TMDs show desirable type II band alignment for constructing highly-efficient heterojunction solar cells with strong charge separation and enhanced sunlight absorption.

The present investigation examined whether an association exists between betel quid chewing and signs of periodontal disease and determined the prevalence of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis by polymerase chain reaction. The periodontal status of 34 betel quid chewers and 32 non‐betel quid chewers were compared. A significantly higher prevalence of bleeding on probing was found in betel quid chewers than non‐chewers among the subjects with higher plaque level, greater gingival inflammation, deeper probing depth or greater attachment loss. Also, the results suggested that betel quid chewers may harbor higher levels of infection with A. actinomycetemcomitans and P. gingivalis than non‐betel quid chewers. The association persists after adjusting for severity of the clinical parameters. In conclusion, betel quid chewing was associated with a higher prevalence of bleeding on probing where higher clinical levels of disease existed, and with a likelihood of subgingival infection with A. actinomycetemcomitans and P. gingivalis.

Spin field-effect transistors (SFETs) based on the Rashba effect could manipulate the spin of electrons electrically, while seeking desirable Rashba semiconductors with large Rashba constant and strong electric-field response, to preserve spin coherence remains a key challenge. Herein, we propose a series of 2D Rashba semiconductors with two-atom-thick buckled honeycomb structure (BHS) according to high-throughput first-principles density functional theory calculations. BHS semiconductors show large Rashba constants that are favorable to be integrated into nanodevices superior to conventional bulk materials, and they can be fabricated by mechanical exfoliation or chemical vapor deposition. In particular, 2D AlBi monolayer has the largest Rashba constant (2.77 eVÅ) of all 2D Rashba materials. Furthermore, 2D BiSb monolayer is a promising candidate for SFETs due to its large Rashba constant (1.94 eVÅ) and strong electric field response (0.92 eÅ2). Our designed 2D-BiSb-SFET shows shorter spin channel length (42 nm with strain) than conventional SFETs (2–5 μm).

Two-dimensional (2D) Janus transition-metal dichalcogenides (TMDs) (MXY, M ¼ Mo, W; X, Y ¼ S, Se, Te; X s Y) have desirable energy gaps and high stability in ambient conditions, similar to traditional 2D TMDs with potential applications in electronics. But different from traditional 2D TMDs, 2D Janus TMDs possess intrinsic Rashba spin splitting due to out-of-plane mirror symmetry breaking, with promising applications in spintronics. Here we demonstrate a new and effective way to manipulate the Rashba effect in 2D Janus TMDs, that is, charge doping, by using first-principles density functional theory (DFT) calculations.We find that electron doping can effectively strengthen the Rashba spin splitting at the valence band maximum (VBM) and conduction band minimum (CBM) in 2D Janus TMDs without constant energy consumption, superior to traditional techniques (electric fields and strain engineering), but hole doping would weaken the Rashba effect in 2D Janus TMDs. By combining the DFT calculations with the electric-triple-layer model, we also reveal the intrinsic mechanism of tuning the Rashba effect in 2D Janus TMDs by charge doping, and find that the charge transfer plays an important role in tuning the Rashba spin splitting in 2D polar semiconductors. In particular, the Rashba constants are linearly dependent on the charge transfer between X (or Y) and M atoms in 2D Janus TMDs. These results enrich the fundamental understanding of the Rashba effect in 2D semiconductors, which can be promising candidates for spin field-effect transistors (FETs) in experiments. Recently, a polar TMD monolayer, MoSSe, has been successfully synthesized in experiments, 17,18 and is a Janus TMD. 2D Janus TMD monolayers MXY (M ¼ Mo, W; X, Y ¼ S, Se, Te; X s Y) show desirable energy gaps (1.0-2.0 eV) 19,20 and high stability [17][18][19][20] in ambient conditions, similar to traditional 2D TMDs 21-23 with potential applications in electronics. In particular, the Janus TMD monolayers show intrinsic Rashba spin splitting due to the

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In this paper, we report the dielectric spectroscopy of hexagonal boron nitride (h-BN) ceramic which has been widely used due to a very low dielectric coefficient. In order to obtain the relaxation time distributions of h-BN, the Havriliak–Negami empirical equation is selected to analyse the measured dielectric data due to the Cole–Cole plots of h-BN samples. In the processes of solving the empirical equation, a nonlinear least-square technique is used and the boundary condition for unknown parameters in the equation is defined. The relaxation time and its distribution parameters are obtained by this method. The polarization mechanisms are also discussed based on the obtained relaxation time distributions. This research may be helpful for applications of h-BN ceramic.

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