Bi ${}_2$ Se ${}_3$ has extensive application as thermoelectric materials. Here, large-scale Bi ${}_2$ Se ${}_3$ single-crystal hexagonal nanoplates with size 7.50–10.0 $\mathsf{\mu }$ m were synthesized successfully by hydrothermal method. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to characterize the Bi ${}_2$ Se ${}_3$ nanoplates, which confirm the single-crystal quality and smooth surface morphology with large size. Micro-Raman spectra over a temperature range of 83–603 K were furthermore used to investigate the lattice dynamics of Bi ${}_2$ Se ${}_3$ nanoplates. Both 2A ${}_g^1$ and 1E ${}_g^2$ modes shift evidently with reduced temperature. The line shape demonstrates a significant broadening of full width at half maximum (FWHM) and red-shift of frequency with increased temperature. The temperature coefficient of A ${}_{1g}^1$ , E ${}_g^2$ , A ${}_{1g}^2$ modes were determined to be −1.258 × 10 ${}^{-2}$ cm ${}^{-1}$ /K, −1.385 × 10 ${}^{-2}$ cm ${}^{-1}$ /K, −2.363 × 10 ${}^{-2}$ cm ${}^{-1}$ /K, respectively. Such low temperature coefficient may favor the obtaining of a high figure of merit (ZT) and indicate that Bi ${}_2$ Se ${}_3$ nanoplates were used as excellent candidates of thermoelectric materials.

An optoelectronic diode based on a p–n junction is one of the most fundamental device building blocks with extensive applications. Compared with graphene, layered transition-metal dichalcogenides demonstrate promising applications in novel valley-electronics and opto-electronics. Here we reported the fabrication and optoelectronic properties of a single multilayer MoS₂ sheet. Our results indicate that the thin MoS₂ shows a linear transport property while thick MoS₂ shows diode characteristics with well-defined current rectification behavior. We assign that the rectification behavior is due to the formation of a p–n junction in the single multilayer MoS₂ piece. The intrinsic defects in MoS₂ can change the conduction polarity, such as: sulfur vacancies contribute to the n-type behavior while sulfur interstitials and molybdenum vacancies contribute to the p-type conduction. The variation of intrinsic defects and stoichiometry is obvious over the micrometer range in thick MoS₂. The fabricated MoS₂ transistors were assessed under bias and gate voltage modulation when exposed to red, green and UV light under vacuum. The multilayer MoS₂ shows dominant p-type behavior under dark conditions while its shows dominant n-type conduction under light illumination. In addition, this MoS₂ phototransistor shows an evident photovoltaic effect. The open-circuit voltage (V_oc) and short-circuit current (I_sc) are observed to be −0.48 V and 494 nA under red illumination. These results demonstrate the potential application of a single multilayer MoS₂ sheet in optoelectronics, such as light-emitting diodes (LEDs), field-effect photovoltaic cells and photodetectors.

In a two-terminal Au/hexagonal WO₃ nanowire/Au device, ions drifting or carriers self-trapping under external electrical field will modulate the Schottky barriers between the nanowire and electrodes, and then result in memristive effect. When there are water molecules adsorbed on the surface of WO₃ nanowire, hydrogen ions will generate near the positively-charged electrode and transport in the condensed water film, which will enhance the memristive performance characterized by analogic resistive switching remarkably. When the bias voltage is swept repeatedly under high relative humidity level, hydrogen ions will accumulate on the surface and then implant into the lattice of the WO₃ nanowire, which leads to a transition from semiconducting WO₃ nanowire to metallic H_xWO₃ nanowire. This insulator-metal transition can be realized more easily after enough electron-hole pairs being excited by laser illumination. The concentration of hydrogen ions in H_xWO₃ nanowire will decrease when the device is exposed to oxygen atmosphere or the bias voltage is swept in atmosphere with low relative humidity. By modulating the concentration of hydrogen ions, conductive hydrogen tungsten bronze filament might form or rupture near electrodes when the polarity of applied voltage changes, which will endow the device with memristive performance characterized by digital resistive switching.

Layered two-dimensional (2D) gallium monochalcogenide (GaX, X = S, Se, Te) semiconductor crystals hold great promise for potential electronics and photonics application. In this paper, we reported the optoelectronic properties of 2D bandgap engineered GaSe_0.5Te_0.5 nanoflakes. The GaSe_0.5Te_0.5 nanoflakes were synthesized by chemical vapor deposition (CVD) and characterized by XRD, SEM, TEM, XPS, Raman and PL spectra, which demonstrate the high crystal quality of as-prepared nanoflakes. The photodetector based on single GaSe_0.5Te_0.5 nanoflake shows fast response time, high reversibility and stability both in air and vacuum. The photo-responsivity is up to 22 A W⁻¹ under illumination of 532 nm light. More interesting, the GaSe_0.5Te_0.5 nanoflake photodetector demonstrate extended light response range, as compared with pure GaSe. The photo-responsivity is 13 A W⁻¹ for 650 nm red light. The present results suggest strongly that the bandgap engineered 2D GaSe_0.5Te_0.5 nanoflakes hold extensive applications in next-generation photodetection and photosensing nanodevices.

We demonstrate a scheme for realizing quantum-information storage (retrieval) into (from) a quantum memory using a hybrid quantum system, which consists of N nitrogen-vacancy (N-V) centers (as memory), N transmission line resonators (TLRs) (as data bus), and N current-biased Josephson-junction (CBJJ) superconducting phase qubits (as heads of read and write). By virtually exciting the vibrational modes of the TLRs, this can produce an effective coupling between the N-V centers and the CBJJs in the system. Because the operation time ($\sim${}10$-${}8 s) is much shorter than the decoherence time of the CBJJ ($\sim${}10$-${}5 s), the quantum information can be transferred between the N-V centers and the CBJJs easily. Owing to the strong-coupling condition [$\lambda${}/2$\pi${}$\gg${}($\gamma${}eg,$\Gamma${},$\gamma${}$\phi${})] and the long coherence time ($\sim${}10$-${}3 s) of the N-V centers, the quantum information can be stored in the memory steadily, and it can be retrieved with a high fidelity (>96%). This scheme provides a scalable way of exchanging quantum information between different quantum interfaces, and has the experimental feasibility with currently available experimental technology.