Investigation of the structural and electrical properties of air-annealed ruthenium thin films on 6H–SiC at different temperatures

Ruthenium (Ru) Schottky contacts and thin films on n-type 6H–SiC were fabricated and characterised by physical and electrical methods. The characterisation was done after annealing the samples in air at various temperatures. Rutherford backscattering spectroscopy (RBS) analysis of the thin films indicated the oxidation of Ru after annealing at a temperature of 400 °C, and interdiffusion of Ru and Si at the Ru–6H–SiC interface at 500 °C. XRD analysis of the thin films indicated the formation of RuO₂ and RuSi in Ru–6H–SiC after annealing at a temperature of 600 °C. The formation of the oxide was also corroborated by Raman spectroscopy. The ideality factor of the Schottky barrier diodes (SBD) was seen to generally decrease with annealing temperature. The series resistance increased astronomically after annealing at 700 °C, which was an indication that the SBD had broken down. The failure mechanism of the SBD is attributed to deep inter-diffusions of Ru and Si at the Ru–6H–SiC interface as evidenced by the RBS of the thin films.     

Influence of surface topography and annealing temperature on the surface and volume of dissipation electrical energy and Spitzer–Fan model in Al doped ZnO films

The aim of this work is to investigate the optical constants of aluminum doped zinc oxide films annealed at different temperatures. With increasing temperature, due to decreasing unfilled inter-granular volume per unit thickness, the optical transmittance spectra of films were increased. The films have a normal dispersion in the spectral range 400?<?λ?<?500 nm and the anomalous dispersion in IR range. The lattice dielectric constants ε_L, the free charge carriers concentration, the plasma frequency, Spitzer–Fan model and the waste of electrical energy as heat of films can be analyzed using the refractive index n and the extinction coefficient k spectra. With increasing annealing temperature, the lattice dielectric constants ε_L of films decrease however the free charge carriers concentration of films increase. The free carrier electric susceptibility of films annealed at 600 °C has maximum value. The energy loss by the free charge carriers when traversing the bulk and surface of films annealed at 600 °C has a minimum value in the near fundamental absorption edge and it with increasing energy increases.     

Effect of thermal annealing on disorder and optical properties of Cr/Si bilayer thin films

Chromium/silicon bilayers are deposited by sequential electron beam evaporation on quartz substrates. The bilayers consisting of Cr and Si layers of 50 and 400 nm thicknesses, respectively, are subjected to post-deposition annealing at temperatures from 200 to 700 °C. The thermal annealing results in the interdiffusion between Cr and Si, as evidenced by cross-section scanning electron micrographs and the line profiles obtained from energy-dispersive X-ray spectroscopy. It is inferred from the compositional line profiles that the films are a combination of silicon-rich oxide, chromium oxide and unreacted Cr up to 500 °C. Chromium disilicide forms at temperatures greater than 500 °C with decrease in chromium oxide content. The refractive index value and extinction coefficient values are 2.1 and 0.12 in the as-deposited case which increase to 3.5 and 0.24 at 400 °C. These values decrease to 2.1 and 0.12 at 500 °C. At the same temperatures, the band gap values are 2.21, 2.40 and 2.28, respectively. Thus, the refractive index, absorption coefficient and the optical band gap of the films peak at an annealing temperature of 400 °C and decrease thereafter. Significantly, this is accompanied by increase in Urbach energy which is an indication of increase in disorder in the system. There is decrease in Urbach energy as well as the optical constants at temperatures >400 °C.     

Ellipsometry,FTIR, Raman and X-Ray Spectroscopy Analysis of PECVD a-Si1-xCx:H Film

Hydrogenated amorphous silicon carbide (a-Si_1-xC_x:H) films were deposited by RF plasma enhanced chemical vapor deposition (PECVD) and subsequently annealed in N₂ atmosphere at different temperatures. Systematic investigations of the deposition temperature and annealing effect on the film's properties, including film thicknesses, optical bandgap, refractive indexes, absorption coefficient (α), chemical bond configurations, stoichiometry and crystalline structures, were performed using ellipsometry, FTIR absorbance spectroscopy, Raman spectroscopy, XPS, and XRD. All of the results indicate that the structural and optical properties of the a-Si_1-xC_x:H film can be effectively engineered by proper annealing conditions. Moreover, molecular vibrational level equation was introduced to explain the peak shift detected by FTIR and Raman spectroscopy.     

Annealing temperature dependent on structural,optical and electrical properties of indium oxide thin films deposited by electron beam evaporation method

In the present work the influence of annealing temperature on the structural and optical properties of the In₂O₃ films deposited by electron beam evaporation technique in the presence of oxygen was studied. The deposited films were annealed from 350 to 550 °C in air. The chemical compositions of In₂O₃ films were carried out by X-ray photoelectron spectroscopy (XPS). The film structure and surface morphologies were investigated as a function of annealing temperature by X-ray diffraction (XRD) and atomic force microscopy (AFM). The structural studies by XRD reveal that films exhibit preferential orientation along (2 2 2) plane. The refractive index (n), packing density and porosity (%) of films were arrived from transmittance spectral data obtained in the range 250–1000 nm by UV–vis-spectrometer. The optical band gap of In₂O₃ film was observed and found to be varying from 3.67 to 3.85 eV with the annealing temperature.     

Temperature-dependent luminescence dynamics for ZnO thin films

The paper presents the photoluminescence investigation of zinc oxide thin films. A high quality ZnO films fabricated by dip-coating (sol–gel) method were grown on quartz wafers. The films with different thickness (number of layers) were annealed at different temperatures after the preparation process. It was found that high quality, transparent ZnO thin films could be produced on quartz substrates at relatively low annealing temperature (450–550  $^{\circ }\mathrm{C}$ ). The dependence of the ZnO thin film quality was studied by X-ray diffraction and atomic force microscopy techniques. Optical properties were investigated by classic and time-resolved photoluminescence (TRPL) measurements. Photoluminescence spectra allowed us to estimate energy of the free excitons, bond excitons and their longitudinal optical (LO) phonon replicas as a function of the annealing temperature. An innovative TRPL technique let us precisely measure the decay time of the free- and bond excitons’ in the real time. TRPL measurements as a function of temperature reveal a biexponential decay behavior with typical free/bound exciton decay constants of 970/5310 ps for the as-grown sample and 1380/5980 ps after annealing process. Presented spectra confirm high structural and optical quality of investigated films. We proved that the thermal treatment improve both optical and structural quality and extend the photoluminescence’s lifetimes. The obtained experimental results are important for identification of exciton’s peaks and their LO phonon replicas for the investigated ZnO films.     

Effects of thermally induced anatase-to-rutile phase transition in MOCVD-grown TiO2 films on structural and optical properties

Titanium dioxide (TiO₂) films with a thickness of 550 nm were deposited on quartz glass at 300 °C by metalorganic chemical vapor deposition. The effects of post-annealing between 600 °C and 1000 °C were investigated on the structural and optical properties of the films. X-ray diffraction patterns revealed that the anatase phase of as-grown TiO₂ films began to be transformed into rutile at the annealing temperature of 900 °C. The TiO₂ films were entirely changed to the rutile phase at 1000 °C. From scanning electron spectroscopy and atomic force microscopy images, it was confirmed that the microstructure of as-deposited films changed from narrow columnar grains into wide columnar ones. The surface composition of the TiO₂ films, which was analyzed by X-ray photoelectron spectroscopy data, was nearly constant although the films were annealed at different temperatures. When the annealing temperature increased, the transmittance of the films decreased, whereas the refractive index and the extinction coefficient calculated by the envelope method increased at high temperature. The values of optical band gap decreased from 3.5 eV to 3.25 eV at 900 °C. This abrupt decrease was consistent with the anatase-to-rutile phase transition. Received: 4 October 2000 / Accepted: 4 December 2000 / Published online: 23 May 2001     

Influence of annealing temperature on optical properties of zinc oxide thin films analyzed by spectroscopic ellipsometry method

Zinc oxide (ZnO) thin films were sol–gel spin coated on glass substrates, annealed at various temperatures 300 °C, 400 °C and 500 °C and characterized by spectroscopic ellipsometry method. The optical properties of the films such as transmittance, refractive index, extinction coefficient, dielectric constant and optical band gap energy were determined from ellipsometric data recorded over the spectral range of 300–800 nm. The effect of annealing temperature in air on optical properties of the sol–gel derived ZnO thin films was studied. The transmission values of the annealed films were about 65% within the visible range. The optical band gap of the ZnO thin films were measured between 3.25 eV and 3.45 eV. Also the dispersion parameters such as single oscillator energy and dispersive energy were determined from the transmittance graph using the Wemple and DiDomenico model.     

Optical constants of vacuum annealed radio frequency (RF) magnetron sputtered zinc oxide thin films

Zinc oxide thin films were deposited by radio frequency magnetron sputtering. The films were annealed in vacuum at temperatures of 400, 600, and 800 °C. The influence of annealing on the structural, chemical, and optical properties of the films was investigated. From a structural point of view, the films were highly oriented, with columnar microstructure. Chemical analysis indicated that the films were sub-stoichiometric, and that the concentration of oxygen vacancies was enhanced upon annealing. The films were highly transparent in the visible and near-infrared spectral regions. Transparency was reduced as the annealing temperature was increased. The refractive index and extinction coefficient, in the transparent regions of the films, were derived from transmittance measurements. The refractive index manifested variation that was affected by crystallite size, roughness and defect concentration. The extinction coefficient of the as-deposited films and those annealed at 400 °C was negligible. However, the films annealed at 600 or 800 °C had much larger values of the extinction coefficient due to increased absorption or scattering. The absorption coefficient and optical band gap of the films were derived from spectrophotometric measurements. The absorption coefficient showed progressive increase with the annealing temperature. However, the band gap did not show significant variation.     

Effect of annealing on photo accelerated chemically deposited Indium sulfide thin films with various cationic precursors

The present work reports the deposition of Indium sulfide thin films by a recently established novel method called photo-assisted chemical deposition technique. It is a very low cost method for the deposition of thin films, and can be easily scaled up for industrial production. Indium sulfide thin films are deposited on glass substrates through various cationic precursors and the effect of annealing on structural, optical and morphological properties was investigated. Films have been characterized with respect to their structural, optical and morphological properties by means of X-ray diffraction, UV–VIS-NIR Spectrophotometer, SEM and AFM techniques. As-deposited films on glass substrates were amorphous and became crystalline after annealing. The grain size of all the annealed films are larger than the as-prepared films and attained a maximum value for the film prepared with sulfate precursor. The calculated strain was compressive in nature. Surface roughness was estimated from the AFM measurements and found to be decreased in annealed samples. The film deposited with chloride precursor showed a higher visible transmittance of around 80 % and became 90 % on annealing. The variation of packing density follows the variation of the refractive index. The optical band gap of the samples was estimated and found to be within the range of 2.45–2.71 eV, which is in quite agreement with the literature.     

Optical properties of PMN–PT thin films prepared using pulsed laser deposition

(1 ? x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ (PMN–PT) thin films have been deposited on quartz substrates using pulsed laser deposition (PLD). Crystalline microstructure of the deposited PMN–PT thin films has been investigated with X-ray diffraction (XRD). Optical transmission spectroscopy and Raman spectroscopy are used to characterize optical properties of the deposited PMN–PT thin films. The results show that the PMN–PT thin films of perovskite structure have been formed, and the crystalline and optical properties of the PMN–PT thin films can be improved as increasing the annealing temperature to 750 °C, but further increasing the annealing temperature to 950 °C may lead to a degradation of the crystallinity and the optical properties of the PMN–PT thin films. In addition, a weak second harmonic intensity (SHG) has been observed for the PMN–PT thin film formed at the optimum annealing temperature of 750 °C according to Maker fringe method. All these suggest that the annealing temperature has significant effect on the structural and optical properties of the PMN–PT thin films.     

A Spectroscopic Ellipsometry Study of TiO2 Thin Films Prepared by dc Reactive Magnetron Sputtering： Annealing Temperature Effect

TiO2 thin films are obtained by dc reactive magnetron sputtering. A target of titanium （99.995%） and a mixture of argon and oxygen gases are used to deposit TiO2 films on to silicon wafers （100）. The crystalline structure of deposited and annealed film are deduced by variable-angle spectroscopic ellipsometry （VASE） and supported by x-ray diffractometry. The optical properties of the films are examined by VASE. Measurements of ellipsometry are performed in the spectral range O. 72-3.55 e V at incident angle 75^o. Several SE models, categorized by physical and optical models, are proposed based on the ＇simpler better＇ rule and curve-fits, which are generated and compared to the experimental data using the regression analysis. It has been found that the triple-layer physical model together with the Cody-Lorentz dispersion model offer the most convincing result. The as-deposited films are found to be inhomogeneous and amorphous, whereas the annealed films present the phase transition to anatase and rutile structures. The refractive index of TiO2 thin films increases with annealing temperature. A more detailed analysis further reveals that thickness of the top sub-layer increases, whereas the region of the bottom amorphous sub-layer shrinks when the films are annealed at 300℃.     

Optoelectronics properties of TiO<Subscript>2</Subscript>:Cu thin films obtained by sol gel method

In this research, Cu-doped TiO₂ thin films have been successfully deposited onto a glass substrate by Sol–gel technique using dip coating method. The films were annealed at different annealing temperatures (400–500 °C) for 1 h. The structural, optical and electrical properties of the films were investigated and compared using X-ray Diffraction, UV–visible spectrophotometer and 4-point probe method. Optical analysis by mean transmittance T(λ) and absorption A(λ) measurements in the wavelength range between 300 to 800 nm allow us to determine the indirect band gap energy. DRX analysis of our thin films of TiO₂:Cu shows that the intensities of the line characteristic of anatase phase increasing in function of the temperature.     

Optimization of the optical and electrical properties of electron beam evaporated aluminum-doped zinc oxide films for opto-electronic applications

Aluminum-doped zinc oxide (AZO) thin films have been deposited by electron beam evaporation technique on glass substrates. The structural, electrical and optical properties of AZO films have been investigated as a function of annealing temperature. It was observed that the optical properties such as transmittance, reflectance, optical band gap and refractive index of AZO films were strongly affected by annealing temperature. The transmittance values of 84% in the visible region and 97% in the NIR region were obtained for AZO film annealed at 475 °C. The room temperature electrical resistivity of 4.6×10⁻³ Ω cm has been obtained at the same temperature of annealing. It was found that the calculated refractive index has been affected by the packing density of the thin films, whereas, the high annealing temperature gave rise to improve the homogeneity of the films. The single-oscillator model was used to analyze the optical parameters such as the oscillator and dispersion energies.     

Influence of thermal annealing on optical and structural properties change in Bi-doped Ge30Se70 thin films

The effect of annealing on the structural and optical properties of thermally evaporated Ge₃₀Se₇₀ and Ge₃₀Se₆₀Bi₁₀ thin films is reported in this paper. The prepared films were thermally annealed at 250°C to optimize the optical properties which can be used for the optical device fabrication. X-ray diffraction study revealed no structural transformation whereas the surface morphology changed as observed from scanning electron microscopy. The optical properties of the deposited and annealed films have been investigated by using a UV–VIS–NIR spectrophotometer in the wavelength range of 400–1100?nm. The optical band gap of the Ge₃₀Se₇₀ annealed film is found to be increased while the energy gap of the Bi-doped annealed Ge₃₀Se₆₀Bi₁₀ thin film decreased which is explained by the chemical disorderness, defect states and density of localized states in the mobility gap. The Tauc parameter and Urbach energy which measure the degree of disorder changed with the annealing process. The transmittivity increases and the absorption power decreases in the Ge₃₀Se₇₀ annealed film, whereas the reverse effect is noticed for the annealed Ge₃₀Se₆₀Bi₁₀ thin film. The irreversible nature of this change can be useful for optical recording purposes.     

Effect of annealing temperature on the characteristics of ZnO thin films

Effect of annealing temperature on characteristics of sol–gel driven ZnO thin film spin-coated on Si substrate was studied. The UV–visible transmittance of the sol decreased with the increase of the aging time and drastically reduced after 20 days aging time. Granular shape of ZnO crystallites was observed on the surface of the films annealed at 550, 650, and 750 °C, and the crystallite size increased with the increase of the annealing temperature. Consequently nodular shape of crystallites was formed upon increasing the annealing temperature to 850 °C and above. The current–voltage characteristics of the Schottky diodes fabricated with ZnO thin films with various annealing temperatures were measured and analyzed. It is found that, ZnO films showed the Schottky characteristics up to 750 °C annealing temperature. The Schottky diode characteristics were diminished upon increasing the annealing temperature above 850 °C. XPS analysis suggested that the absence of oxygen atoms in its oxidized state in stoichiometric surrounding, might be responsible for the diminished forward current of the Schottky diode when annealed above 850 °C.     

Effect of thermal annealing on the structure and microstructure of TiO2 thin films

Nanostructured TiO₂ thin films have been prepared through chemical route using sol-gel and spin coating techniques. The deposited films were annealed in the temperature range 400–1000°C for 1 h. The structure and microstructure of the annealed films were characterized by GAXRD, micro-Raman spectroscopy and AFM. The as-deposited TiO₂ thin films are found to be amorphous. Micro-Raman and GAXRD results confirm the presence of the anatase phase and absence of the rutile phase for films annealed up to 700°C. The diffraction pattern of the film annealed at 800 to 1000°C contains peaks of both anatase and rutile reflections. The intensity of all peaks in micro-Raman and GAXRD patterns increased and their width (FWHM) decreased with increasing annealing temperature, demonstrating the improvement in the crystallinity of the annealed films. Phase transformation at higher annealing temperature involves a competition among three events such as: grain growth of anatase phase, conversion of anatase to rutile and grain growth of rutile phase. AFM image of the asdeposited films and annealed films indicated exponential grain growth at higher temperature.      

The microstructure of SiO thin films: from nanoclusters to nanocrystals

The microstructure and electronic structure of silicon-rich oxide (SRO) films were investigated using transmission electron microscopy and electron energy loss spectroscopy as the main analytical techniques. The as-deposited SRO film was found to be a single phase SiO_1.0, as suggested by its electronic structure characteristics determined by the valence electron energy loss spectrum. This single phase undergoes a continuous but incomplete phase decomposition to Si and SiO₂ for films annealed between 300 and 1100°C. The resulting Si phase first appears as ～2?nm-diameter amorphous clusters which grow to larger sizes at higher annealing temperatures, but only crystallize at a critical temperature between 800 and 900°C. This cluster/matrix configuration of the SRO films is consistent with the appearance of the interface plasmon and its oscillator strength as a function of the nanoparticle size. Three separate stages were identified in the sequence of annealed films that were characterized by the presence of single-phase SiO, amorphous silicon nanoclusters, and silicon nanocrystals, respectively. The presence of amorphous silicon nanoclusters in the intermediate stage, the mean size of which can be controlled via annealing, may offer an alternative to silicon nanocrystal composites for optical applications.     

Solid State Reaction of Ruthenium with 6H-SiC Under Vacuum Annealing and the Impact on the Electrical Performance of its Schottky Contact for High Temperature Operating SiC-Based Diodes

Thin films and Schottky diodes dots of ruthenium (Ru) on bulk-grown n-type-6-hexagonal-silicon carbide (6H-SiC) were annealed isochronally in a vacuum furnace at temperatures ranging from 500–1,000 °C. Rutherford backscattering spectroscopy analysis of the thin films showed formation of ruthenium silicide (Ru₂Si₃) at 800 °C, while diffusion of Ru into 6H-SiC commenced at 800 °C. Raman analysis of the thin films annealed at 1,000 °C showed clear D and G carbon peaks which was evidence of formation of graphite. At this annealing temperature, the Schottky contact was observed to convert to an ohmic contact, as evidenced by the linearity of current–voltage characteristic, thereby, rendering the diode unusable. The transformation from Schottky contact to ohmic contact is attributed to graphite formation at the interface.     

Synthesis and characterization of light emitting Eu2O3 films on Si substrates

We have studied the optical and structural properties of Eu₂O₃ thin films grown by RF magnetron sputtering on Si substrates. The films have been annealed in O₂ ambient to improve their properties. The intensity of the photoluminescence (PL) signal detected at room temperature from the films depends on the temperature of the thermal process. The structural characterization of the films, performed by transmission electron microscopy, energy filtered transmission electron microscopy and x-ray diffraction, reveals that annealing processes performed at temperatures higher than 900 °C induce a mixing at the Eu₂O₃–Si interface, leading to the formation of a silicate-like layer, which is responsible for the observed decrease of the PL intensity.