Structural and optical properties of TiO2 thin films grown by sol-gel dip coating process

The mono and bi-layer TiO₂ thin films have been prepared by sol-gel method on glass. X-Ray diffraction, Raman spectroscopy, atomic force microscopy, spectroscopic ellipsometry and m-lines spectroscopy techniques have been used to characterize the TiO₂ films. The mono-layer film is found to be amorphous, while the bi-layer film shows the presence of anatase phase. The bi-layer film exhibits more homogeneous surface with less roughness. The thickness effect on the refractive index, extinction ceofficient, packing density and optical band gap is analysed. The waveguiding measurements of the bi-layer film exhibit single-guided TE₀ and TM₀ polarized modes from which we can measure the refractive index and the film thickness.     

ZnTe precipitates formed in SiO2 by sequential implantation of Zn and Te ions

Ion implantation is a versatile tool for the formation of compound semiconductor nanocrystal precipitates in a host medium with the ultimate goal to form quantum dots for use in device technology. Low dose (1 × 10¹⁶ cm⁻²) implantations of tellurium and zinc ions have been performed in a 250 nm thick SiO₂ layer thermally grown on 1 1 1 silicon. Their respective energies (180 and 115 keV) have been chosen to produce 5–10 at.% profiles overlapping at a mean depth of about 100 nm. Subsequent thermal treatments at 700 and 800 °C lead to the formation of nanometric precipitates of the compound semiconductor ZnTe. Their size, crystalline structure and depth distribution have been studied as a function of annealing temperature using transmission electron microscopy (TEM) and Rutherford backscattering spectrometry. For the lowest temperature the TEM images shows a cloudy band of ZnTe, but for the highest temperature, the ZnTe nanocrystals are self organized into two layers parallel to the surface. Their mean diameter ranges between 4 and 30 nm, as a function of annealing temperature.     

Effect of Sb implantation on copper silicides formation and morphology after annealing of Cu/Si structures

In this work, the solid state reaction between a thin film of copper and silicon has been studied using Rutherford backscattering spectroscopy, X-ray diffraction, scanning electron microscopy and microprobe analysis. Cu films of 400 and 900 Å thicknesses are thermally evaporated on Si(1 1 1) substrates, part of them had previously been implanted with antimony ions of 5×10¹⁴ or 5×10¹⁵ at. cm⁻² doses. The samples are heat-treated in vacuum at temperatures in the range 200–700 °C for various times. The results show the growth and formation of Cu₃Si and Cu₄Si silicides under crystallites shape dispatched on the sample surface, independently of the implantation dose. On the other hand, it is established that the copper layer is less and less consumed as the antimony dose increases, resulting in the accumulation of Sb⁺ ions at silicide/Si interface and in the silicide layer close to surface. The exposure of samples to air at room temperature shows the stability of Cu₄Si phase whereas the Cu₃Si silicide disappears to the benefit of the silicon dioxide formation. The observed phenomena are discussed.     

Comparison of Thin Films of Titanium Dioxide Deposited by Sputtering and Sol–Gel Methods for Waveguiding Applications

Semiconductors - In this work, TiO2 thin films were deposited onto glass substrate by two different techniques: sol–gel dip-coating (SG) and reactive DC magnetron sputtering (Sput). The...     

Effect of substrate temperature on the structural and magnetic properties of Fe/Ag superlattices

In the present work, Fe/Ag superlattices were grown by molecular beam epitaxy (MBE) on MgO(001) single crystal substrates maintained at room temperature or at 423 K during the deposition. The structural properties were carried out using small and high angle X-ray diffraction techniques. The magnetic hysteresis loops with the magnetic field applied parallel or perpendicular to the plane of the films were measured by a superconducting quantum interference device (SQUID) magnetometer in the temperature range 5–300 K. A comparison of the obtained results showed that the heating of MgO substrates leads to a strong interdiffusion and causes a significant modification of structural and magnetic properties of Fe/Ag superlattices.     

Formation of Nanometric Yttrium Silicides Layers onto Si (111) Substrate by Ion Implantation

Silicon - Nanometric YSi2 − x yttrium silicides layers have been formed onto a Si(111) single-crystal substrate by implantation at room temperature (RT) of Y ions using an energy...     

Study on the solid state reaction between bilayered Pd/Au films and silicon substrates

Bilayers of pure palladium and gold films were evaporated alternatively on (1 0 0) and (1 1 1) monocrystalline silicon substrates. After annealing, in a vacuum furnace from 100 to 650 °C during 30 min, the growth sequence of the Pd₂Si and PdSi phases that evolved as the result of the diffusion reaction was examined by means of Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), whereas the surface morphology was investigated by scanning electron microscopy (SEM) technique. The effect of the intermediate gold layer is investigated in order to test its effectiveness as barrier for Cu and Si atoms interdiffusion and its influence on the morphology of the formed palladium silicides. The effect of substrate orientation on the palladium silicides growth and formation was also explored.     

Luminescence properties of ZnS:Mn nanocrystals embedded in SiO2 by ion implantation

Sequential multi-energy implantations of zinc and sulphur ions have been performed in a 250-nm thick SiO₂ layer thermally grown on 1 1 1 silicon. Energies and doses have been chosen to produce 10 at.% constant concentration profiles overlapping over about 100 nm. Manganese is subsequently introduced at various levels by the same way. Thermal treatments (from 700 to 1100 °C) lead to the formation of nanometric precipitates of the luminescent compound ZnS:Mn. A bimodal size distribution is observed, with a quasi-single layer of large particles (40 nm) in the end-of-range region and much smaller precipitates between this layer and the surface. The orange emission is maximal when the Mn concentration is close to 3%. Several hours at 900 °C is the best thermal budget for maximal luminescence intensity at room temperature. A shift of the excitation spectrum related to size variations, shows that the particles of smaller size are mainly responsible for the observed luminescence. In agreement with other authors, the luminescence lifetime is found in the ms range and increases with the nanocrystal diameter, tending to the lifetime of bulk ZnS. The luminescence of ZnS:Mn nanoparticles embedded in SiO₂ by ion implantation is also shown to be very stable during long UV light irradiation.     

Characterization of C12A7 thin films deposited by spray pyrolysis

In this work, conductive C12A7 thin films were deposited by spray pyrolysis method onto glass substrates. The films, structural, optical and electrical properties were investigated as a function of the spray number. X-rays diffraction showed that the deposited films were polycrystalline with a preferential orientation along the (310) planes. Raman spectroscopy confirmed the C12A7 phase and revealed the superoxide radical \( {\text{O}}_{2}^{ - } \) presence. The C12A7 films, optical transmission varied between 57 and 75 % as a function of the spray number. A constant band energy (4.14 eV), determined from UV–visible spectra, was attributed to the electrons transition from the valence band to the occupied cage level. According to the photoluminescence (PL) spectroscopy, two main emission peaks at 1.55 and 2.81 eV were respectively attributed to the formation of the “F⁺-like centers” and the electron transitions from the occupied cage level to the framework conduction band. Another emission peak at about 2.27 eV was attributed to the cages oxygen vacancies defects. The electrical resistivity variation between 10^?4 and 1.36 Ω cm was correlated to the in cages oxygen vacancies produced during films deposition.     

Spray Pyrolysis Synthesized and ZnO–NiO Nanostructured Thin Films Analysis with Their Nanocomposites for Waveguiding Applications

Semiconductors - In this work, we have prepared ZnO, NiO, and nanocomposites ZnO–NiO thin films elaborated by the chemical method of spray pyrolysis on glass substrates at a temperature of...