Optical properties of Ar ions irradiated nanocrystalline ZrC and ZrN thin films

Thin nanocrystalline ZrC and ZrN films (<400 nm), grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique, were irradiated by 800 keV Ar ion irradiation with fluences from 1 × 10¹⁴ at/cm² up to 2 × 10¹⁵ at/cm². Optical reflectance data, acquired from as-deposited and irradiated films, in the range of 500 - 50000 cm^-1 (0.06 - 6 eV), was used to assess the effect of irradiation on the optical and electronic properties. Both in ZrC and ZrN films we observed that irradiation affects the optical properties of the films mostly at low frequencies, which is dominated by the free carriers response. In both materials, we found a significant reduction in the free carriers scattering rate, i.e. possible increase in mobility, at higher irradiation flux. This is consistent with our previous findings that irradiation affects the crystallite size and the micro-strain, but it does not induce major structural changes.

Band offsets in YSZ/InGaZnO4 heterostructure system

The energy discontinuity in the valence band (deltaE(v)) of Y2O3-stabilized ZrO2 (YSZ)/InGaZnO4 (IGZO) heterostructures was obtained from X-ray photoelectron spectroscopy (XPS) measurements. The YSZ exhibited a bandgap of 4.4 eV from absorption measurements. A value of deltaE(v) = 0.57 +/- 0.12 eV was obtained by using Ga 2P3/2, Zn 2p3/2 and In 3d5/2 energy levels as references. This implies a conduction band offset (deltaE(c)) of 0.63 eV in YSZ/InGaZnO4 heterostructures and a nested interface band alignment.

Growth of Cerium Oxide Buffer Layers and Superconducting thin films on Silicon

Films of CeO2 have been grown on Si and glass substrates using the laser ablation deposition technique. X-ray diffraction measurements for the films deposited on glass indicated that they are the same as films grown on Si covered with the native oxide. This evidence supports a picture in which chemical rather than crystal-lographic effects constrain the film growth. The crystal quality for films grown on Si was shown to improve with increasing film thickness away from the amorphous layer. Low cooling rates as well as reduced film thickness were effective in avoiding the formation of micro-cracks. The surface morphology was shown to be dependent on the laser wave-length as well as the oxygen partial pressure. Thin films of YBa2Cu3O7δ could easily be grown on CeO2/Si showing c-axis orientation, whereas the growth of BiSrCaCuO (2212) on CeO2/Si resulted in the two films mixing with each other.

Calcium phosphate thin film processing by pulsed laser deposition and in situ assisted ultraviolet pulsed laser deposition

Calcium orthophosphates (CaP) and hydroxyapatite (HA) were intensively studied in order to design and develop a new generation of bioactive and osteoconductive bone prostheses. The main drawback now in the CaP and HA thin films processing persists in their poor mechanical characteristics, namely hardness, tensile and cohesive strength, and adherence to the metallic substrate. We report here a critical comparison between the microstructure and mechanical properties of HA and CaP thin films grown by two methods. The films were grown by KrF* pulsed laser deposition (PLD) or KrF* pulsed laser deposition assisted by in situ ultraviolet radiation emitted by a low pressure Hg lamp (UV-assisted PLD). The PLD films were deposited at room temperature, in vacuum on Ti-5Al-2.5Fe alloy substrate previously coated with a TiN buffer layer. After deposition the films were annealed in ambient air at 500-600 degrees C. The UV-assisted PLD films were grown in (10(-2)-10(-1) Pa) oxygen directly on Ti-5Al-2.5Fe substrates heated at 500-600 degrees C. The films grown by classical PLD are crystalline and stoichiometric. The films grown by UV-assisted PLD were crystalline and exhibit the best mechanical characteristics with values of hardness and Young modulus of 6-7 and 150-170 GPa, respectively, which are unusually high for the calcium phosphate ceramics. To the difference of PLD films, in the case of UV-assisted PLD, the GIXRD spectra show the decomposition of HA in Ca(2)P(2)O(7), Ca(2)P(2)O(9) and CaO. The UV lamp radiation enhanced the gas reactivity and atoms mobility during processing, increasing the tensile strength of the film, while the HA structure was destroyed.

Electron-microscopic studies on the effect of calcium pantothenate upon rat liver and locally irradiated epidermis

Calcium pantothenate was administered to Wistar rats in a dose of 180 mg/day/rat for 42 days, in order to investigate its effect upon the ultrastructure of the epidermis locally irradiated with a dose of 600 rep and upon partly hepatectomized liver and locally irradiated epidermis, as compared to control. The resulting data have revealed that calcium pantothenate is metabolized without entailing ultrastructural changes. Both liver and epidermis appear to be protected by calcium pantothenate, which greatly diminishes or even cancels the display of irradiation-induced negative effects. The changes brought about by irradiation are throughly presented and the subcellular mechanisms providing the radioprotection of epidermis and liver are accurately defined.

Pulsed Laser Deposition of High Quality ZnO Thin Films

Thin films of ZnO have been grown on silicon and glass substrates by the pulsed laser deposition method. The effects of the oxygen partial pressure, substrate temperature and laser wavelength on the structural and optical properties of the films have been studied. The KrF excimer laser (at 248 nm) was found to produce better quality thin films than the frequency doubled Nd:YAG laser (532 nm). Layers produced at substrate temperatures as low as 300°C were c-axis oriented with a FWHM value for the 002 XRD reflection less than 0.2° and exhibited optical transmission higher than 80% in the visible region.