Artorn Pokaipisit

NANOSTRUCTURE AND PROPERTIES OF INDIUM TIN OXIDE (ITO) FILMS PRODUCED BY ELECTRON BEAM EVAPORATION

Nanocrystal indium tin oxide (ITO) thin films were grown by electron beam evaporation (e-beam). The ITO films were fabricated at substrate temperatures ranging from 100 to 400°C in O2 partial pressure ranging from 0.10 to 100 mTorr. The surface morphology was monitored using atomic force microscopy (AFM). The charge in the surface morphology of ITO films was discussed in terms of grain size and crystallographic orientations. Grain size measurements of the solid dispersed and the AFM study for nanostructure showed that the oxides were in the nano range (20–30 nm). In general, the values of the optical bandgap for the films are consistently blue-shifted as compared with the crystal size. The average crystalline size determined from the shift of the optical gap were found to be in the range 20–30 nm, which is in excellent agreement with the data obtained from AFM. All ITO films average grain size was ~ 20 nm deposited by e-beam evaporation. The average optical transmittance was 90.50% in the visible range (400–700 nm) and the average bandgap was 3.98 eV. ESR spectrum of ITO film showed random oxygen vacancies which arise due to the changing crystal field effects.

Dynamic in situ spectroscopic ellipsometric study in inhomogeneous TiO2 thin-film growth

We investigate the film-growth process of the inhomogeneous sputtered TiO2 thin films by the in situ real-time spectroscopic ellipsometer. The growth process of the film is analyzed by both the uniform and the island film growth models. Based on the analyses from the Ψ-Δ trajectories, the initial thin-film growth corresponds to the island film growth model for a single-layer film. As the film grows, the microstructural phase changes cause the transition from the single-to the double-layer physical model, because of the development of the inhomogeneity in the TiO2 thin film. The dynamic fits with the double-layer physical model and the Cody–Lorentz optical model indicate three different stages of the film growth: the nucleation stage, the coalescence stage, and the continuous-layer stage. Although our presented model works well for most of the experimental data, the determination of the refractive index at the ultrathin thickness may be problematic.

Vacuum and Air Annealing Effects on Properties of Indium Tin Oxide Films Prepared by Ion-Assisted Electron Beam Evaporation

Indium tin oxide (ITO) films were deposited on glass substrates by ion-assisted electron beam evaporation, followed by annealing in vacuum and air at different temperatures from 200 to 350 °C with an interval of 50 °C for 1 h. The deposited films were analyzed by a four-point probe method, Hall effect measurement, an X-ray diffraction technique, spectrophotometry, and atomic force microscopy. Results show that the electrical resistivity of ITO films depends on annealing temperature. Its lowest value of 1.07 ×10-4 Ω cm is obtained at an annealing temperature of 350 °C in vacuum. The optical transmittance of ITO films with a thickness of 500 nm for annealing in air is higher than that in vacuum. The optical band gap and grain size increase with increasing annealing temperature.

Raman spectroscopy of DLC/a-Si bilayer film prepared by pulsed filtered cathodic arc

DLC/a-Si bilayer film was deposited on germanium substrate. The a-Si layer, a seed layer, was firstly deposited on the substrate using DC magnetron sputtering and DLC layer was then deposited on the a-Si layer using pulsed filtered cathodic arc method. The bilayer films were deposited with different DLC/a-Si thickness ratios, including 2/2, 2/6, 4/4, 6/2, and 9/6. The effect of DLC/a-Si thickness ratios on the sp3 content of DLC was analyzed by Raman spectroscopy. The results show that a-Si layer has no effect on the structure of DLC film. Furthermore, the upper shift in G wavenumber and the decrease in ID/IG inform that sp3 content of the film is directly proportional to DLC thickness. The plot modified from the three-stage model informed that the structural characteristics of DLC/a-Si bilayer films are located close to the tetrahedral amorphous carbon. This information may be important for analyzing and developing bilayer protective films for future hard disk drive.

Fabrication and characterization of hydrophilic TiO 2 thin films on unheated substrates prepared by pulsed DC reactive magnetron sputtering

TiO2 thin films were deposited on unheated silicon wafers (100) and glass slides by a pulsed DC reactive magnetron sputtering in an ultrahigh vacuum (UHV) system. The effects of both an operating pressure and deposition time on film structure, surface morphology, and optical property were studied. The film structure and microstructure were characterized by grazing-incidence X-ray diffraction (GIXRD) technique and transmission electron microscopy (TEM). The surface morphology was investigated by field emission scanning electron microscopy (FE-SEM). The optical property of the TiO2 thin films was determined by spectroscopic ellipsometry (SE). The water contact angle measurement was also used to determine hydrophilicity of the films after exposed to UV light. The results suggested that the TiO2 thin film at less than 40 nm was amorphous. As the thickness was increased, the mixture of anatase and rutile phases of TiO2 began to form. By reducing the operating pressure during the film deposition, the rutile phase component can also be enhanced. Both the increased film thickness and decrease operating pressure were the critical factors to improve the hydrophilicity of the TiO2 thin films.

Performance of Near-Infrared Reflective Tile Roofs

A green pigments based on a Cr2O3-Al2O3-V2O5-TiO2 composition have been synthesized and the ability of these pigments used with ceramic glazes to confer high solar reflectance has also been studied. Cr2O3 is the host component and the adding mixtures of Al2O3, V2O5 and TiO2 as the guest components. The composition denoted by T1 composes of Cr2O3, TiO2, Al2O3 and V2O5 are 80, 4, 14 and 2 wt%, respectively, gives near infrared solar reflectance of 82.8%. T1 green pigments were prepared for ceramic cool tile roofs (denoted by T1 cool roof). The comparison study on the effectiveness of T1 ceramic cool roofs and a commercial ceramic cool tile roofs (denoted by C cool roof) show that the T1 cool roof has given a better result by keeping the tested room about 4 °C cooler.

Effect of Bi2O3 Content on the Properties of Bi2O3-BaO-B2O3 Glass System

Glasses with composition xBi2O3:(60-x)BaO:40B2O3 with 10£x£50 (in mol%) have been prepared using the normal melt-quench technique. The optical absorption spectra of the glasses have been recorded in the wavelength range 400-700 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The values of optical band gap are decreased with the addition of Bi2O3. The density and molar volume studies indicated that Bi2O3 in these glasses is acting partly as network modifier and partly as network former.Values of the theoretical optical basicity are also reported and discuss in term of oxide ion polarizability.

POST-ANNEALING EFFECTS ON THE STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF ITO FILMS STUDIED BY SPECTROSCOPIC ELLIPSOMETRY

ITO thin films were coated on unheated glass and Si-wafer (100) substrates by ion-assisted evaporation. The effects of post annealing, in vacuum at 250°C and 350°C for 1 h, on the structural, optical and electrical properties were studied. The structure was characterized by X-ray diffraction (XRD). The surface morphology of the films was investigated by atomic force microscopy (AFM). The optical properties were evaluated by spectrophotometer and spectroscopic ellipsometry (SE). The resistivity was measured by the four-point probes method. It was found that the increase of post-annealing temperature would improve the film crystallinity and electrical properties. The preferred orientation of ITO thin film after annealing is (222). The resistivity of the as-deposited film is found to be 5.52 × 10-4 Ωcm and decreases to 2.11 × 10-4 Ωcm after annealing at 350°C. The AFM image reveals that the surface roughness decreases with increasing annealing temperature. The uniqueness test based on SE analysis data has be...

Comparison of Nanocrystalline TiO2 Films Prepared on Unheated Substrates Using Single- and Dual-Cathode DC Unbalanced Magnetron Sputtering Systems

Titanium dioxide (TiO2) films were deposited on unheated Si(100) wafers by single- and dual-cathode dc unbalanced magnetron sputtering. Each cathode was specially designed with a high magnetic field strength. The effect of the radial distance from the center of the coating cathode on the film structures was investigated. For the substrate placed at the center of the coating cathode, it was found that the TiO2 films deposited by dual-cathode sputtering exhibit rutile with higher crystallinity than films deposited by single-cathode sputtering. At various radial distance from the center to 6 cm to the left and light of the center, mixed phases of rutile and anatase were observed on TiO2 films deposited using both single- and dual-cathode sputtering systems. Furthermore, in the case of using dual-cathode, crystalline TiO2 films were obtained for a longer range to the left of the center than to the right owing to the higher magnetic field strength.

Compositional Changes of Enamel and Dentine after Er:YAG Laser Irradiation

The aim of the present study was to investigate the organic and inorganic compositions of enamel and dentine after Er:YAG laser irradiation using Fourier-transform Raman spectroscopy (FT-Raman). The enamel and dentine of extracted human teeth were irradiated by Er:YAG laser at an energy density of 29.7 J/cm2. The organic and inorganic components were evaluated from Raman spectra of untreated and laser-treated of extracted human teeth. The results showed that the Raman intensity ratio of the carbonate peak (1067 cm-1) to the phosphate peak (957 cm-1) and the organic peak (2940 cm-1) to the phosphate peak of enamel and dentine decreased after laser irradiation. Therefore, laser treatment can reduce the organic and inorganic components of human enamel and dentine.