Papers by Author: Surasing Chaiyakun

Abstract: Chromium aluminum nitride (CrAlN) has been extensively studied because of high hardness, high oxidation and corrosion resistance, and good wear resistance. However, utilizing substrate treatments such as heating and voltage biasing during film deposition usually leads to relatively high surface roughness that affects wear rates. It has been found that sputter deposition at low substrate temperatures can produce nano-grain coatings with enhanced structure and mechanical properties. For this reason, the CrAlN in this study was prepared by a reactive co-sputtering technique without the substrate treatments. Effects of Al content on structure and mechanical properties were investigated by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectrometry, atomic force microscopy, X-ray photoelectron spectroscopy, and nanoindentation. The results suggest that these CrAlN films formed as solid solutions by substitution of Al for Cr in the CrN crystalline structure. The deposition with increasing Al but fixed N leads to N deficiency, therefore at high Al content these films form under 1:1 stoichiometric nitride. This lowers film crystallinity and hence refined film morphology. Surface roughness and hardness of the films decreased from 5.737 to 1.135 nm and from 31.69 to 26.56 GPa, respectively. However, the solid solution strengthening arising from the further increase of the Al content causes these values to rebound to 2.466 nm and to 30.16 GPa.

Abstract: Very thin titanium chromium nitride (TiCrN) films with various Ti content were deposited by unbalanced magnetron co-sputtering of Ti and Cr metals. Deposition time was set to 15 min to achieve film thickness ranging from 142 to 190 nm. Silicon wafers and copper grids were used as substrates. The Ti current (I_Ti) was varied from 0.4 to 1.0 A to achieve the differnt Ti content whereas Cr current (I_Cr) was fixed to 0.6 A. Effects of the Ti content on structure and morphology of these TiCrN thin films were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). The XRD revealed that the films showed crystalline structure with fcc phase and were formed as Ti_xCr_1-xN solid solution with a crystallite size of about 13 nm. The TEM result confirmed that the films were polycrystalline. The AFM images of the films showed dome top characteristic with root-mean-square roughness slightly decreasing from 1.643 to 1.273 nm. FE-SEM cross-sectional images exhibited development of film morphology from columnar structure corresponding to zone 1 of Thornton’s structure zone model to fine structure gradually with the increase of the Ti content.

Abstract: Zirconium oxide (ZrO₂) thin films were deposited on Si-wafer and glass slide substrates by reactive DC unbalanced magnetron sputtering at different deposition times. A pure metallic zirconium target (99.97%) was sputtered in a gas mixture of argon and oxygen. The crystal structure was characterized by GI-XRD (grazing-incidence X-ray diffraction) whereas surface morphologies and films thickness were evaluated by AFM (atomic force microscopy). The transmittance spectrum was measured by spectrophotometer. The optical constants of the as-deposited films were calculated by Swanepoel method. It was found that the ZrO₂ films deposited on silicon substrates showed a highly monoclinic phase (-1 1 1). The as-deposited films showed high transmittance in visible range. The thickness and roughness varied from 155 nm to 502 nm and 3.1 nm to 3.6 nm, respectively, with increasing of deposition times. The optical constants namely refractive index (n) and extinction coefficient (k), at 550 nm, was about 1.9 - 2.1 and 0.0003 - 0.0009, respectively. In addition, the energy band gap (E_g) of the as-deposited film was approximately 4.17 eV.

Abstract: In this work, TiO₂ thin films were prepared by a sol-gel spin coating method on glass slide, stainless steel 304 and silicon wafer substrates. The thin films were annealed at different temperatures at ambient atmosphere. The effect of substrates and annealing temperatures on microstructure, surface morphology and hydrophilicity of the films were characterized by Raman spectroscopy, atomic force microscopy and water contact angle measurement, respectively. The Raman spectra indicated that the annealed TiO₂ thin films (at 550 °C) coated on stainless steel and silicon wafer exhibited anatase structure. The contact angle of all samples decreased with increasing the UV-irradiation time and annealing temperature.

Abstract: Deposition of aluminum and zinc targets was carried out by DC magnetron sputtering to produce aluminum doped zinc oxide (AZO) thin films. These films were deposited on quartz, glass and silicon substrates under 5.5x10^-3 mbar pressure. At a ratio of argon gas to oxygen gas (Ar:O₂) of 5:10 and a voltage at zinc target of260 V, AZO thin films were deposited at different currents at aluminum target such as 900, 1,000, 1,100 and 1,200 mA. Effect of current at aluminum target on the structural, optical and electrical properties of resulting films was studied. Structural characterization by X-ray diffraction (XRD) technique and Energy Dispersive X-Ray Spectroscopy (EDS) confirmed incorporation of aluminum in ZnO lattice. The thickness measurement by Scanning Electron Microscope (SEM) showed that the thickness of AZO thin films is in the range of 270–350 nm. An average transmittance of above 80% in the visible wavelength region was obtained for aluminum doped zinc oxide. The optical direct bandgap and the resistivity of AZO thin films were found in the range 3.3-3.5eV and 6.0x10^-1-9.0x10^-1 Ωcm; respectively.

Abstract: Titanium nitride (TiN) thin films were deposited on to unheated silicon (100) and stainless steel substrates by home-made direct current (DC) reactive magnetron sputtering method at a deposition of 60 min in an Ar-N₂ gas mixture. The effects of sputtering power on structure and microstructure of these films have been studied. The films were analyzed by X-ray diffraction (XRD), Atomic Force Microscope (AFM) and Field-Emission Scanning Electron Microscope (FE-SEM). The films colors were influenced by sputtering parameter which altered from green purple to light gold and dark gold, respectively. By XRD, the polycrystalline structure of the as-deposited films was face center cubic (fcc) of TiN structure with (111), (200), (220), and (311), planes. The increasing of sputtering power transformed film from amorphous phase to crystal phase with crystal size were enhanced from 21.9 nm to 39.8 nm. The AFM scans revealed that sputtering power significantly affected surface morphologies and thicknesses of the TiN films. With increase in sputtering power, the roughness and films thickness were increased from 0.5 nm to 25.1 nm and 331 nm to 1113 μm, respectively. The microstructure combined with cross-section analysis FE-SEM revealed that the grain refinement with columnar structure were obtained for the film deposited at sputtering power of 270 W.

Abstract: In the past decade, many transition metal nitride thin films, especially titanium nitride (TiN) and zirconium nitride (ZrN), have been widely used as hard coatings, decorative coatings, diffusion barriers in IC technology and heat mirrors, as a result of their attractive properties of high hardness, corrosion resistance, thermal stability and electrical resistivity [1-4]. However, the ZrN films have shown significant performance regarding to its higher hardness, better corrosion resistance, lower electrical resistivity and warmer golden colour compared to those of the TiN films. ZrN films have shown significant performance advantages over TiN films [5-.

Abstract: Aluminum nitride (AlN) thin films have been deposited on the glass slide and Si-wafer by reactive DC magnetron sputtering technique at different sputtering power. The as-deposited films have been characterized by grazing-incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM) and optical transmittance, respectively. The results show that the as-deposited films were transparent and have high transmittance in visible regions. The crystal structure from XRD results show that the as-deposited films are amorphous with low sputtering power and turn to crystal structure with high sputtering power, which showed orientation of AlN structure corresponding to the AlN(1 0 0), AlN(1 0 1) and AlN(1 1 0). The roughness values and the films thickness from AFM was varied from 0.4 nm to 3.9 nm and 199 nm to 905 nm, respectively. The optical constants namely the refractive index n and the extinction coefficient k, were determined from transmittance spectrum in the visible regions by using envelope method. For 500 nm, n and k, were in the range of 1.8 2.0 and 0.014 0.004 respectively.

Abstract: Titanium nitride (TiN) thin films of different crystal structure and morphologies were deposited by direct current (dc) reactive magnetron sputtering method under conditions of various deposition times (3090 min). The crystal structure, crystal size, thickness and surface morphology properties of the films were studied and the results were discussed with respect to deposition time. The films were deposited on Si (100) and stainless steel substrates with constant Ar to N₂ ratio of 15:2 sccm and sputtering power of 280 W. The crystal structure was characterized by X-ray diffraction. The Scherrers formula was used to calculated crystal size. The surface morphology and thickness were evaluated by Atomic Force Microscope (AFM). The golden coloured with uniformnity of TiN films were obtained at deposition time for 30 min. The as-deposited films color was varied with the deposition times from gold, brown and dark brown. The polycrystalline films showed reflections corresponding to the (111), (200), (220) and (311) orientations of the face center cubic TiN structure. The crystallinity of the films was increased with increased the deposition times. The AFM results indicate that the grain size of surface morphologies changed through the deposition times. With increase in deposition time, the roughness and films thickness were increased from 5.0 nm to 21.0 nm and 551.0 nm to 1.4 μm, respectively.

Abstract: The TiAlN thin films with different crystal structure, surface morphology, microstructure and chemical compositions were deposited on Si (100) plane by changing the N₂ flow rate from 2 to 10 sccm using co-targeted reactive magnetron sputtering technique in the same process. The effect of nitrogen flow rate on structure and properties of TiAlN thin films was investigated in the study. The films were characterized by X-ray Diffraction (XRD), Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) techniques, respectively. The results show that the crystal structure, surface morphologies microstructure and chemical compositions of the film are strongly depended on the N₂ flow rates. The (111) (200) and (220) planes of TiAlN thin films were found with different nitrogen flow rates, one is the preferred orientation of (111) plane that appeared for nitrogen flow rates of 2 sccm, the other one is the preferred orientation of (200) plane for the higher nitrogen flow rates of 4-10 sccm. The crystal size of the films was also determined by Scherrers equation, varied between 13.8 - 35.6 nm. The roughness of the as-deposited films was ranging from 1.8 to 4.3 nm. The chemical compositions of TiAlN were depended on N₂ flow rates. The microstructure and cross-sectional SEM analysis revealed that the nanograins were developed and thickness decreased from 381 nm to 131 nm. In addition, the columnar structures were observed for all films.