[en] The reaction kinetic processes of species produced in a pulsed TEA CO₂ laser induced silane plasma were studied with the time-resolved OES. It is showed that the time position of main peaks for different fragments' characteristic lines are appreciably different. The reaction kinetic processes are discussed based on the results. By comparing the time evolution of the lines of the fragments and considering the other results of OES, the authors infer that the final reaction channel of the laser-induced silane plasma is a Si producing channel

[en] A self-consistent hybrid Monte Carlo fluid model is presented to describe the nitrogen dc glow discharge. The movement of fast electrons is simulated by the Monte Carlo method while the dynamics of slow electrons and ions is by fluid equations. The spatial features of the charged species and the corresponding electric field throughout the discharge have been calculated, which include the creation rates of ions and slow electrons, densities of the charged species, the electric field and the potential distribution. These closely related results can give a self-consistent explanation of the discharge characteristics throughout the space of nitrogen dc glow discharge. The calculated ion density is also compared with the corresponding experimental result

[en] Graphical abstract: In this paper, the temperature dependence of the LPE has been experimentally studied under illumination of different lasers ranging from visible to infrared for the μc-SiOx:H/a-Si:H/c-Si p-i-n structure. It was found that the position sensitivity increases nearly linearly with wavelength from 405 nm to 980 nm in the whole temperature range, and the saturated position sensitivity decreased quickly from 32.4 mV/mm to a very low value of 1.26 mV/mm and the nonlinearity improved from 7.01% to 3.54% with temperature decreasing from 296 K to 80 K for 532 nm laser illumination. By comparing the experiment results of μc-SiOx:H/a-Si:H/c-Si and ITO/c-Si, it is suggest that the position sensitivity was mainly determined by the temperature-dependent SB and the nonlinearity was directly related to the decreased resistivity of conductive layer. When an external bias voltage was applied, the LPE improved greatly and the position sensitivity of 361.35 mV/mm under illumination of 80 mW at 80 K is 286.7 times as large as that without biased voltage. More importantly, both the position sensitivity and the nonlinearity were independent of temperature again, which can be ascribed to the large constant transmission probability and diffusion length induced by the greatly increased SB. Our research provides an essential insight on the bias voltage-modulated LPE at different temperatures, and this temperature-independent greatly improved LPE is thought to be very useful for developing novel photoelectric devices. - Highlights: • The LPE is proportional to the laser wavelength in the whole temperature range. • The LPE decreases gradually with decreasing temperature from 296 K to 80 K. • Nonlinearity of the LPV curve improves a little with decreasing temperature. • The LPE improves dramatically and is independent of temperature with the aid of a bias voltage. - Abstract: The lateral photovoltaic effect (LPE) in μc-SiOx:H/a-Si:H/c-Si p-i-n structure is studied at different temperatures under illumination of different lasers ranging from visible to infrared. The LPE improves with increasing laser wavelength with the position sensitivity nearly linearly dependent on the wavelength in the whole temperature range. Though the position sensitivity decreased gradually with decreasing measurement temperature from 296 K to 80 K, the nonlinearity improved a little, which can be ascribed to the decreased resistivity of conductive layer. Considering that the LPE was mainly determined by the Schottky barrier (SB), an external bias voltage was added to enhance the built-in field, it was found that the LPE improved dramatically with position sensitivity linearly proportional to the laser power. More importantly, both the position sensitivity and the nonlinearity were independent of temperature again in the whole laser power range. Our research sheds new light on the bias voltage-modulated LPE at low temperatures.

[en] Na₃Bi(PO₄)₂:Eu³⁺/Tb³⁺/Dy³⁺/Sm³⁺ phosphors were synthesized via a high-temperature solid-state reaction method. The X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), diffuse reflection, photoluminescence (PL) and fluorescent decay curves were utilized to characterize the obtained phosphors. Under n-UV excitation, Na₃Bi(PO₄)₂:Eu³⁺/Tb³⁺/Dy³⁺/Sm³⁺ samples show the characteristic f-f emissions and present red, green, yellow and orange emission, respectively. When Tb³⁺, Dy³⁺ and Sm³⁺ were co-doped into the Na₃Bi(PO₄)₂:Eu³⁺ phosphors, tunable emission colors can be obtained and can be efficiently adjusted by varying the doping ions and the doping concentration. The energy transfer mechanisms were investigated in detail and demonstrated that there is an efficient energy transfer from Tb³⁺, Dy³⁺ and Sm³⁺ to Eu³⁺ via a dipole-dipole interaction mechanism. Additional, as the temperature increases from RT to 150 °C, the PL intensity of Tb³⁺-Eu³⁺, Dy³⁺-Eu³⁺ and Sm³⁺-Eu³⁺ co-doped phosphors decreased to 86%, 85% and 88%, respectively, which prove good thermal stability. All the CIE coordinates of as-prepared phosphors are displayed and show abundant colors, making these materials have potential applications for n-UV-excited white-LEDs.

[en] Highlights: •The evolution of PL from Si cluster to nanocrystal in SRO/SiO₂ multilayer films is studied. •The quantum confinement effect and interface related PL are discussed. •PL red shift with extending the detecting time is obtained. -- Abstract: The evolution of photoluminescence (PL) from Si cluster to nanocrystal in Si-rich oxide (SRO)/SiO₂ multilayer films is reported. Two PL bands can be obtained when the SRO layer thickness is no larger than 2 nm, and the high energy PL band (blue band) is related to the interband transition of Si cluster caused by quantum confinement effect (QCE), while the low energy band (red band) is related to the interface recombination. Both Si clusters and nanocrystals exist in the film when the SRO layer is increased to 3 nm, and the intense PL in the red band suggests that Si nanocrystals becomes the main light-emitting centers. The blue band disappears when the SRO layer is increased to 4 nm, and the PL mechanisms of the red band are QCE and interface defects in Si nanocrystals

[en] Hydrogenated amorphous silicon carbide (a-Si_1-xC_x : H) films with different carbon concentrations have been deposited using the helicon wave plasma-enhanced chemical vapour deposition technique under the condition of strong hydrogen dilution. The a-Si_1-xC_x:H films with carbon content x up to 0.64 have been deposited. Their structural and optical properties are investigated using Fourier transform infrared spectroscopy, Raman scattering, ultraviolet-visible transmittance spectroscopy and x-ray photoelectron spectroscopy. The deposition rate, optical band gap and B factor related to structural disorder are found to monotonically change in the investigated range with methane-silane gas flow ratios. It is found that the deposited films exist with the structure of Si-like clusters and Si-C networks when silicon content is high, while they consist mainly of C-like clusters and Si-C networks for carbon-rich samples. A large optical band gap is obtained in high carbon concentration samples, which is attributed to the high density characteristic of helicon wave plasmas and the strong hydrogen dilution condition

[en] The ions (N₂⁺, N⁺) and fast nitrogen molecular (N_2f) transport process in cathode sheath of nitrogen glow discharge plasma is studied by using Monte Carlo simulation. Spatial variation of energy distribution and angular distribution are simulated for ions (N₂⁺, N⁺) and fast molecules (N_2f) in cathode sheath, their variation behavior are investigated, and the results are compared with the results of experiment

[en] Optical emission spectroscopy (OES) is used to diagnose the active species emission in the helicon-wave-plasma-enhanced chemical vapor deposition of nanocrystalline silicon. The effects of the experimental parameters on OES intensity of SiH, H_β and H_α have been studied. Experiment results indicate that the magnetic field confinement makes the reactant molecules dissociate efficiently. Appropriate hydrogen dilution can increase the density of hydrogen active species, while higher dilution makes the concentration of silicon-contained active species decrease. The density of the active species increase monotonically with increasing input rf power, and a relatively higher concentration of hydrogen active species reaching the substrate surface can be achieved. Experiment results obtained are analyze based on the dispersive relation and the characteristic of the helicon wave plasma, which offer the basic data for the understanding of the process of nanocrystalline silicon deposition and adjusting its experimental parameters. (authors)

[en] The process of decay of photoelectrons in the conduction band of ZnS:Mn, Cu luminescent materials after excitation with a short-pulse laser has been investigated in this paper by means of measurements made using the microwave absorption dielectric spectrum detection technique. Exponential decay processes were observed for the electrons in the conduction band and the shallow-trapped electrons; the lifetimes of the electrons were found to be 1177 and 1703 ns, respectively. The processes of decay of the luminescence from ZnS:Mn, Cu were investigated and exponential decay processes were found for blue Cu⁺, green Cu⁺ and Mn²⁺ luminescent centres with lifetimes of the excited state of 139, 140 and 680 μs, respectively

[en] Using Monte Carlo simulation,the energy distribution of heavy particles bombarding negative wall under different discharges is studied. It is shown that various particle energy distributions in front of the cathode wall depend on the electric field and the collision frequency. The density of low-energy fast atoms (N_f) is nearly two magnitudes higher than that of high-energy particles (N⁺) in front of the cathode. Under the condition corresponding to the highest creation rate of active species (N⁺, N_f), suitable decrease in gas pressure, and increase in discharge voltage and gas temperature will be beneficial to the active particles reaching a cathode