Abstract: The physical background and present status of the application of metal-insulator-silicon structures with semiconductor nanocrystals embedded in the insulator layer for memory purposes is breafly summarized.
Abstract: The paper presents results of research of similar electrical, optical and structural properties of three types of MOS structures prepared on different Si-based semiconductors. Electrical interface properties are investigated by institutionally produced equipment with Charge Version of Deep Level Transient Spectroscopy and time domain C-V. X-ray diffraction at grazing incidence angles is applied to control their structural properties. Optical properties of selected structures are investigated by photoluminescence measurements at liquid helium temperature (approx. 6K in cryostat). Dominant interest is focused on analysis of both electrical properties of MOS porous silicon based structures prepared on p-type crystalline Si and photoluminescence signals of the structures observed around 1.1 eV, respectively.
Such parameters as Fermi level position, flat-band voltage, surface potential, position of deep level hole traps, and acceptor density are calculated for various conditions as defined by sample ambient, temperature, and light illumination. Following two main findings are analyzed: i) total suppression of large C-V hysteresis due to suitable illumination and ii) recovering of part of detected interface states in the dark.
Abstract: The perovskites RNiO3 (R rare earth ≠ La) are classified as a phase transition metal-insulator. The transition temperature is modulated by the size of the rare earth. The use of compound R1-xR'xNiO3 can vary transition temperature on a wide thermal range depending on the concentration of the two rare earths. The Sm1-xNdxNiO3 (x = 0.45) thin layers have been carried out on (100) silicon substrates by KrF laser ablation (λ = 248 nm, 25ns) at two different fluences 2 and 3 Jcm-2. The oxygen pressure and the target-substrate distance have been maintained at 0.2 mbar and 4 cm respectively. The deposition temperature has been set at 500 ° C. The obtained layers were characterized by X-ray diffraction, atomic force microscopy and Rutherford back scattering diagnostics. The resistivity Measurements were carried out by the conventional four-probe method. The XRD spectra revealed the presence of an ideal cubic perovskite phase. The RBS analysis showed that the deposited layers are rich in oxygen. A correlation between the morphology properties of the deposited layers and the plasma dynamics studied by fast imaging has been found.
Abstract: Thin films of CuIn1-xBxSe2 (CIBS) as absorption layer in single-junction solar cells can potentially grant a higher band gap in comparison with other studied chalcopyrite materials like CuIn1-xGaxSe2 (CIGS) and CuIn1-xAlxSe2 (CIAS). The higher band gap near optimum value ~ 1.4 eV can help to achieve higher efficiency (today 19.5% for CuIn0.74Ga0.26Se2). In this paper are described first results of experiments with effort to produce CIBS films by selenization of CuInB precursor alloy in Se vapors. Resulting material was analyzed by Raman spectroscopy, X-ray diffraction, and Auger electron spectroscopy. Measurements show that formation of CIBS layer is complicated by forming of pure CuInSe2 layer with unwanted Cu2-xSe phases and by accumulation boron near to the substrate.
Abstract: In this work, the combined diagnostic measurements of ablated material by scanning electron microscopy of the craters and ion time of flight analysis have been employed to study the interaction of third harmonic Nd-Yag laser with silicon and titanium target. Evidence for the transition from normal vaporization to phase explosion has been obtained, showing an abrupt increase in the mass ablation rate beyond a laser intensity threshold and round-shaped micrometer-sized cavities found on the irradiated areas. Ion time of flight analysis is used to estimate the surface temperature under near threshold ablation conditions.
Abstract: First principles calculations, by means of the full-potential linearized augmented plane wave method within the local density approximation, were carried out for the optical properties of the strained layer superlattices (GaAs)6/(GaP)m(001) (m=2, 4 and 6). The calculated imaginary part of the dielectric function agrees well with the available experimental data. The assignment of the structures and the peaks in the optical spectra and band structure transitions are investigated in detail. Our results indicate that the anisotropy in these materials is mostly due to the tensile strain in the GaP layers.
Abstract: Some investigations on physico-chemical properties of hydrogenated amorphous carbon (a-C:H) thin films deposited from C2H4 precursor have been carried out. The films were elaborated in a Microwave Multipolar Plasma reactor excited at Distributed Electron Cyclotron Resonance (MMP-DECR). The effects of the plasma power on the electrical and structural characteristics of the deposited films have been evaluated. It appeared that for low plasma power ( 400 W), the deposition rate and the hydrogen concentration increases, whereas the Csp2 concentration remains constant. Beyond 400 W, the deposition rate and the hydrogen concentration reach saturation levels and the Csp2 concentration decreases. In contrast, the film density decreased with the increase of the plasma power. Below 400 W, the dielectric constant decreased with the increase of the plasma power, however, beyond 400 W its value remained almost constant. The correlation between film characterization and properties shows that the permittivity is driven by the film density and the film structure.
Abstract: Reflectometry technique in Centre de Recherché Nucléaire de Draria (CRND) is operational since 2002. The instrument is used for investigation of monochromators and supermirrors. In this communication, several monochromators: 10 and 40 nickel-titanium bilayers deposited on a float-glass substrate with different period are analysed. The investigation of magnetic multilayers (25 silicon-iron bilayers monochromator) is also performed. From the results, Bragg peaks were identified indicating the periodicity of the multilayers.
Abstract: Thin SiOF films were elaborated in microwave excited DECR plasma reactor (Distributed Electron Cyclotron Resonance) from a mixture of hexamethyldisiloxane (HMDSO) and oxygen (O2) (in 1: 9 proportion) with the presence of various CF4 concentrations. The fluorine contents in the films composition were adjusted by the CF4 gas flow ratio (in the range of 10 - 70%). The refractive index and the deposition rate were estimated from ellipsometric data and the film chemical structure was studied by FTIR analysis technique. The deposition rate increases with increasing CF4 flow and then decreases after reaching a maximum value for 20% of CF4. The decrease in the deposition rate may be attributed to the etching effect by CF4 plasma during the deposition process. As the additive fluorine concentration increases, the intensity of Si–F peak stretching vibrations located at 930 cm-1 increases and the frequency of the Si–O stretching vibration mode centered at 1060 cm-1 shifts towards higher wavenumber.