S. Gurlui

Influence of oxidation conditions on the properties of indium oxide thin films

Abstract Indium oxide (In 2 O 3 ) thin films have been prepared by thermal evaporation of indium in vacuum on a glass substrate at room temperature, followed by thermal oxidation in air. It was experimentally established that the heating velocity during the oxidation process has a strong influence on the electrical and optical properties of films as prepared. The temperature was increased from room temperature to 450°C, with velocities ranging between 0.1°C/s and 0.5°C/s. In 2 O 3 thin films as obtained have been examined for optical transparency function on wavelength. The calculated values of optical band gap range between 2.99 and 3.31 eV. Electrical conductivity measurements have also been carried out on the above oxide thin films as a function of temperature. Both the electrical and optical studies showed that In 2 O 3 thin films with higher transparency and electrical conductivity are obtained at higher oxidation velocities. Also, the experimental results show linear dependences of transmission coefficient on the oxidation velocity.

Experimental and Theoretical Aspects of Aluminum Expanding Laser Plasma

The formation and dynamics of aluminum laser produced plasma are experimentally and theoretically investigated. The visible emitting regions of plasma form two structures of different expansion velocities. Such behavior is in agreement with the transient current recorded by a cylindrical Langmuir probe. Using the hydrodynamic model of scale relativity theory, the plasma dynamics at different time scales are numerically and analytically analyzed.

Some experimental and theoretical results on the anodic patterns in plasma discharge

The dynamics of an interface plasma-plasma self-structured as a double anodic layer using the fractal space-time theory is established. So, for the fractal dimension D=2, the Schrodinger “fluid” is obtained as an irrotational movement of a Navier-Stokes fluid with an imaginary viscosity coefficient. In the deterministic case, the anodic double layer is described by a set of diffusion-reaction equations, a situation in which the equal diffusion curves are of the Koch-type and the self-structuring is given by means of the coherence of the electron-ion pairs. In the nondeterministic case, the anodic double layer is described by a set of time-dependent Schrodinger-type equations and the self-structuring is given by means of the negative differential resistance and the pulsation-potential linear dependence. Through the spontaneous symmetry breaking the Langmuir’s relations, the distributions of the potential field and charge densities have been obtained. The model was verified by means of our experimental data...

Oscillatory Langmuir probe ion current in laser-produced plasma expansion

Using the Langmuir probe method to investigate the parameters of laser-produced plasma, our experimental results show an oscillatory structure of the recorded transient ion current. The periodic behavior is analyzed for various targets and probe positions and, after extracting the continuous part, it is found to be connected with the ion frequency and the electron-ion collision frequency. We conclude that theories to describe these oscillations may provide new diagnostic techniques of laser-produced plasma.

Ordered plasma structures in the interspace of two independently working discharges

The plasma formations that appear in the contact region between two negative glow discharges have been studied by means of electrical and spectral methods. The experimental and theoretical research of the plasma formations show that the double layer is the final stage of a more complex plasma structure which is formed first.

Basic processes in discharge plasma double layers

Experimental results regarding the study of plasma double layers (DLs) by electric and spectral methods in the case of a glow discharge obtained in a chamber of three-electrode geometry are presented. The experimental results prove that the appearance of DLs in active plasmas can be accompanied by quantum processes, such as excitation and ionization.

Optic and spectral characteristics of some aromatic copolyethers embedded in polymer matrices

Abstract Photochromic properties of copolyethers based on bisphenol-A 4, 4′-dihy-droxydiphenyl, 4, 4′-dihydroxy-azobenzene, and 3,3-bis(chloromethyl)oxetane (BCMO) both embedded in a polymer matrix (polyvinyl alcohol, PVA) and in the pure state, deposed on quartz disks, have been studied. The polarization spectra of the studied compounds have been obtained. From the analysis of the absorption spectra in polarized light, it has been established that the oscillator responsible for the appearance of the electronic absorption band executes vibrations with an average orientation along the stretching direction of the studied foils.

Characterization of Aluminum Laser Produced Plasma by Target Current Measurements

The transient target current is used to characterize the aluminum laser produced plasma for various fluences and target external polarizations. A double peak structure of the electronic part was experimentally observed, as consequence of the existence of non-Maxwellian electron distribution through the hot and cold electrons. Applying an external voltage on the target, the ionic part becomes oscillatory, with plasma ion frequency. Assuming that particle motions take place on continuous and non-differentiable curves, a fractal hydrodynamic model of plasma expansion is built. In such conjecture, the analytical solutions and numerical simulations allow a reasonable interpretation of our experimental results.

Laser Ablation Transient Plasma Structures Expansion in Vacuum

The dynamics of transient plasmas generated by high-fluence nanosecond laser ablation has been investigated by means of a fast intensified charge-coupled device imaging system. The recorded pictures reveal a specific splitting process of the plasma plume into fast and slow components.

Investigation of femtosecond laser-produced plasma from various metallic targets using the Langmuir probe characteristic

The Langmuir probe is used to characterize the plasma produced by fs-laser ablation from pure metallic targets. Time dependence of the probe current and the total collected charge is discussed in terms of a shifted Maxwell–Boltzmann distribution function, and from probe characteristics the plasma temperature and average charge state are calculated. Target materials of various physical properties (atomic mass, thermal constants) are used to find possible correlations with resulting plasma parameters. By positively biasing the probe, the collected charge –probe voltage characteristic is in general vertically shifted, and for low negative probe potentials an effect consisting in an abnormal decrease of the ion current is observed. Periodic falls of the total collected charge vs. probe voltage are experimentally recorded, the effect being more significant at high background pressure. They are tentatively attributed to secondary ionization.