Tin oxide (SnO2) is one of the most promising transparent conducting oxide materials, which is widely used in thin film gas sensors. We investigate the dependence of the deposition time on structural, morphological and hydrogen gas sensing properties of SnO2 thin films synthesized by dc magnetron sputtering. The deposited samples are characterized by XRD, SEM, AFM, surface area measurements and surface profiler. Also the H2 gas sensing properties of SnO2 deposited samples are performed against a wide range of operating temperature. The XRD analysis demonstrates that the degree of crystallinity of the deposited SnO2 films strongly depends on the deposition time. SEM and AFM analyses reveal that the size of nanoparticles or agglomerates, and both average and rms surface roughness is enhanced with the increasing deposition time. Also gas sensors based on these SnO2 nanolayers show an acceptable response to hydrogen at various operating temperatures.

No abstract

With the advent of ultrashort high intensity laser pulses, laser absorption during laser-plasma interactions has received significant attention during the past two decades since it is related to a variety of applications of high intensity lasers, including the hot electron production for fast ignition of fusion targets, bright X-ray and gamma-ray sources, ion acceleration, compact neutron sources, and generally the creation of high energy density matters. Although some absorption mechanisms appear for short laser pulses with nanosecond duration time, they usually appear for some nonlinear phenomena as electron ohmic heating and laser pulse ponderomotive force are not considered. In this paper, the absorption of the S-polarized laser pulse through an interaction with an underdense plasma in attendance of electron ohmic heating and ponderomotive nonlinearities is analyzed. It is shown that, due to the effect of the ponderomotive force in both isothermal and non-isothermal plasmas, the increasing laser radiation angle leads to the increasing electric field wavelength. Also, since the ponderomotive force modifies the electron density and temperature distribution, it is shown that the decreasing radiation angle leads to the steepening of the electron density profile and the narrowing of electron bunching. Furthermore, by increasing the radiation angle, the absorption coefficient is decreased strongly. It is found that due to the heat of the plasma at the expanse of the wave energy in the case of a non-thermal plasma, the absorption coefficient is increased intensively in comparison to a collisional plasma.

Using the tridimensional magnetic probe, the current sheath velocity at 0.25 Torr is studied in Sahand, a Filippov-type plasma focus facility. The current sheath velocity in argon-filled plasma focus with different percentages of helium impurity at different operating voltages was studied. The highest average current sheath velocity of 12.26 ± 1.51 cm μs −1 at the top of the anode in the axial phase was achieved at 17 kV. Minimum average current sheath velocity is 5.24 ± 1.18 cm μs −1 at 12 kV with 80% argon + 20% helium as a working gas. The full width at half-maximum of peaks of the magnetic probe was found to be inversely related to the current sheath velocity, i.e. smaller at higher voltages for different impurity and decreased with increasing of impurity.

Nonlinear self-modulation of dust–ion acoustic (DIA) waves is studied in an unmagnetized dusty plasma comprising warm adiabatic ions, arbitrarily charged dust particles, and hot nonextensive q-distributed electrons. By employing the multiple space and time scales perturbation, a nonlinear Schrödinger equation is derived for the evolution of the wave amplitude. The existence along with the stability of wave packets are discussed in the parameter space of two oppositely charged dust and ion temperature over different ranges of the nonextensive parameter q. The growth rate of the modulation instability is also given for different values of the q parameter. It is found that the critical wave number at which the instability sets in increases as the nonextensive parameter q increases. This leads to a wider range (in spatial extension) of the stable envelope solitons. It is also found that the effects of ion temperature and negative (positive) dust concentration significantly modify the criteria for the modulation instability of DIA waves. Our finding should elucidate the nonlinear electrostatic structures that propagate in astrophysical and cosmological plasma scenarios where nonextensive particles exist: such as instellar plasma, stellar polytropes, cosmic radiation, and systems with long-rang interaction.