[en] Highlights: • To fabricate high quality ZnS films need to promote the ion-by-ion process and restrain cluster-by-cluster process. • The complexation ability of tri-sodium citrate is stronger than that of hydrazine hydrate. • The nucleation density of nuclei determine the performance of ZnS thin films. -- Abstract: Zinc sulfide (ZnS) thin films were deposited on glass substrates using the chemical bath deposition (CBD) technique. The effects of different complexing agents (tri-sodium citrate, hydrazine hydrate) and their concentrations on the structure, composition, morphology, optical properties and growth mechanism of ZnS thin films were investigated. The results indicated that the chemical-bath-deposited ZnS thin films exhibit poor crystallinity and a high Zn/S atomic ratio with an average transmittance of 75% in the range of visible light. The ZnS thin films prepared using hydrazine hydrate as the complexing agent present a more compact surface, a smaller average particle size, and a sharper absorption edge at 300–340 nm compared with those prepared using tri-sodium citrate. Based on our experimental observations and analysis, we conclude that the predominant growth mechanism of ZnS thin films is an ion-by-ion process. The nucleation density of Zn(OH)₂ nuclei on the substrate in the initial stage produces the different morphologies and properties of the ZnS thin films prepared using the two complexing agents

[en] A simple and reliable method to determine the junction temperature of GaN-based light-emitting diodes (LEDs) is presented in this paper. The variation of resistance of doped GaN with temperature is advantageously used to measure junction temperature. A simple calibration relating to temperature and resistance is measured and shows excellent agreement with the model analysis. The junction temperature of the pulsed-driving LEDs is measured by resistance meter and shows good agreement with that by the forward voltage method. Experimental results obtained by the described method are presented and discussed. The temperature-dependent resistance method has potential to be a very useful alternative for measurement of temperature in electronic and optoelectronic devices. (paper)

[en] Well-crystallized Cu₂ZnSnS₄ (CZTS) nanoparticles contain ultrasmall nanocrystals (~ 10 nm) have been grown directly on three-dimensional (3D) transparent porous reduced graphene oxide (rGO) thin films by a facile and scalable solution-based strategy. Few-layer rGO prepared by modified Hummers’ method was used to fabricate hierarchical ultraporous 3D rGO thin films (3DGTFs) with high transmittance (> 75% for 200-nm thick). Single-phase kesterite CZTS nanocrystalline particles were grown uniformly on the surface active sites within the 3D rGO network by hydrothermal method. The as-prepared CZTS/rGO composite thin films exhibited excellent electrocatalytic ability by taking advantages of the high conductivity and high surface area of 3DGTFs and the high catalytic activity of CZTS nanoparticles. As expected, the composite thin films demonstrate more than one order of magnitude lower in electrical resistivity and in charge transfer resistance than the individual CZTS thin films. The conversion efficiency of dye-sensitized solar cells using CZTS/rGO thin films as the counter electrode (CE) approached 6.12%, comparable to that using Pt CE (6.45%) and superior to those using individual CZTS CE (1.07%) and rGO CE (0.18%).

[en] Stannous sulfide (SnS) was grown on SiO₂/Si substrates via chemical vapor deposition technique and characterized using optical microscopy, scanning electronic microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, atomic force microscopy and photoluminescence (PL) spectrum, respectively. The results indicate that SnS with two distinct morphologies of “the ultra-thin SnS flakes and the micron-thick SnS crystals” can be grown on different zones of the SiO₂/Si substrate. The ultra-thin SnS flakes are single crystal with thickness of 139 nm and maximum lateral sizes of 371 μm. However, the micron-thick SnS crystals are 2.2 μm-thick and a lateral size of 15 μm with square shape. The difference in morphology between the ultra-thin SnS flakes and the micron-thick SnS crystals is mainly due to the difference in the initial nucleation way. Both the ultra-thin SnS flakes and the micron-thick SnS crystals are orthorhombic structure with high-purity. PL strong peak of the ultra-thin SnS flakes is at 950 nm, and it is at 945 nm for the micron-thick SnS crystals. Their optical band gap is approximately 1.31 eV.

[en] Vertically aligned CoS prismatic nanorods were synthesized on transparent conductive fluorine-doped tin oxide (FTO) substrates by a two-step method. First, vertically aligned Co₃O₄ prismatic nanorod arrays were prepared by a rapid microwave irradiation method. Second, Co₃O₄ were converted to CoS nanorods by solution-based ion exchange reaction (IER). The dye-sensitized solar cell (DSSC) using CoS prismatic nanorods arrays as the counter electrode (CE) achieves a power conversion efficiency of 6.06%, which is comparable with the cells based on Pt-CE (6.45%).

[en] ZnSe thin films are deposited onto glass substrates by the chemical bath deposition (CBD) method at different hydrazine hydrate concentrations and different zinc sulfate concentrations using the precursors of zinc sulfate, sodium selenosulphate, hydrazine hydrate, ammonia and de-ionized water. The morphology, structural and optical properties of ZnSe nanocrystalline thin films were investigated as a function of hydrazine hydrate concentration or zinc sulfate concentration using scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectrophotometer measurements. The results reveal that the ZnSe thin films are composed of a large number of uniform spherical particles. The crystal structure of ZnSe nanocrystalline thin films is the zinc-blende structure. Both the average diameter of the spherical particles and the grain size of the nanocrystals increase with an increase in hydrazine hydrate concentration and/or zinc sulfate concentration. The optical band gap of the ZnSe thin films decrease with an increase in hydrazine hydrate concentration and/or zinc sulfate concentration due to the quantum-size effects. The kinetics and reaction mechanism of the ZnSe nanocrystalline thin films during deposition are discussed.

[en] Memristors have received widespread attention as a new type of nonvolatile memory device, which are promising to mimic synapse dynamics efficiently. In this work, a memristor with the structure of PMMA/Ag/FAPbI${}_3$/FTO was fabricated and memristive behavior was investigated. With PMMA as the passivation layer in this structure, the performance as well as stability of the FAPbI${}_3$ memristor was significantly improved, as compared with non-passivated device. The results show that the device with passivation layer has better stability in the air (20 days) and excellent artificial synaptic functions, such as spike timing-dependent plasticity (STDP), long-term potentiation (LTP) and long-term depression (LTD). This work demonstrates the great potential of PMMA-passivated perovskite memristor in neuromorphic computing.

[en] Two-dimensional (2D) ReS₂ flakes are synthesized by the chemical vapor deposition under atmospheric pressure using Re–Te binary eutectic and sulfur as precursors. The morphologies, crystal structure, phonon vibration modes, chemical states and optical property of the 2D ReS₂ flakes are characterized using optical microscopy, scanning electron microscope, transmission electron microscopy, the Raman spectroscopy, X-ray photoelectron spectroscopy and transmittance spectra. The lateral size of 2D ReS₂ flakes can be tuned via changing the synthesis parameters. The monolayer 2D ReS₂ flakes is single crystal structure. Its maximum lateral size is 30 μm, and optical band gap is 1.42 eV. The absorption coefficient is as large as 10⁵ cm⁻¹, transmittance of 92–98% and refractive index of 1.5–1.3 in the wavelength range from 400 to 800 nm. The effect of synthesis parameters on the morphologies and growth mechanism of 2D ReS₂ flakes are investigated in detail. This is helpful for further application of ReS₂ in electronic and optoelectronic devices.

[en] In this paper, a hydrothermal strategy is developed to synthesize high-quality WSe₂ films on a quartz substrate. N, N-dimethylformamide (DMF) and deionized water are used as double solvent, and low-cost selenium powder and sodium tungstate dehydrate are used as the Se and W sources, respectively. Characterizations with X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy confirm the high quality of hexagonal WSe₂ films. Photodetectors, which are assembled based on such solution-processed WSe₂ films, exhibit a high photoresponsivity and a short response time. This study suggests that WSe₂ films are very promising for optoelectronic applications which require low cost, large area and process simplicity. (orig.)

[en] In the paper the ways to compute the response of transmission line (TL) illuminated by electromagnetic pulse (EMP) were introduced firstly, which include finite-difference time-domain (FDTD) and transmission line matrix (TLM); then the feasibility of electromagnetic topology (EMT) in ICs nuclear electromagnetic pulse (NEMP) effect simulation was discussed; in the end, combined with the methods computing the response of TL, a new method of simulate the transmission line in IC illuminated by NEMP was put forward. (authors)