Papers by Keyword: Sputtering

Abstract: Rare-earth element of gadolinium (Gd) were successfully doped into zinc oxide (ZnO) using dual sputter source of DC and RF sputtering. The substrate rotation speed was controlled from 1 rpm to 9 rpm to investigate their effects on the properties of the films in order to achieve a great feature of thin film. XRD profiles confirmed the c-axis orientation with structure of ZnO hexagonal wurtzite. No peaks related to secondary phases were observed. The intensity of dominant peak showed increment upon improvement of substrate rotation speed. The incorporation of Gd into ZnO structure was further confirmed by composition element form EDX with average atomic percentage of 3 at. % for all the films. Surface topology from AFM images showed the grain size has increased with the higher speed of substrate rotation. Gd-doped ZnO thin films indicated good transparency with an average transmittance above 90 % regardless of substrate rotation speed. The bandgap has a slight decrease from 3.06 eV to 3.03 eV with an increment speed of rotational substrate. These findings further imply that the substrate rotation speed has a significant influence on the structural and optical properties of the sputtered thin films.

Abstract: Thin films of vanadium oxide were synthesized by DC magnetron sputtering on a glass slide. Process parameters including temperature, argon and oxygen ratio (Ar:O₂) and base pressure were investigated. It was found that the control of sputtering base pressure is very important in realizing the pure VO₂ (M) thin films. These thin films have grown at low base pressure of 5x10^-6 mbar. The results of the valence electron analysis show the outstanding phase of VO₂ and a small amount of V₂O₅ and V₂O₃ phases. The hysteresis loop of electrical resistance property of the VO₂ thin films illustrated the quality of film, which is related to metal-insulator transition phase (MIT) at the transition temperature (T_c) of approximately 63°C. The sample was tested for its electrical properties by a four-probe setup with a temperature controller during heating and cooling cycles.

Abstract: In this work, a low-cost method to produce ZnO nanostructured materials for the treatment of water polluted with model organic pollutants (e.g. dyes) is presented. Zinc and silver-coated Zn (Ag/Zn) films, fabricated via sputtering method were naturally oxidized via a simple, low-temperature, scalable thermal process. During oxidation, Ag/ZnO nanorods were grown on Zn foils after treating their surface with various agents (e.g. acids) and annealing in an oven at temperatures 385-400 °C. The ZnO and Ag/ZnO films on Zn were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy. The cationic dye Methylene Blue (MB) was selected as model pollutant dissolved in water, and a batch photo-reactor was fabricated and used to to study the adsorption capacity and photocatalytic performance of films. The transient varation of MB concentration in aqueous solutions was measured with UV-Vis spectroscopy. Ag/ZnO demonstrated a strong MB adsorbion capacity in dark conditions, and a satisfactory MB photocatalytic degradation under UV light irradiation.The optimized doping of Ag in Ag/ZnO film enhanced its photocatalytic activity, and seems well-promising for the potential scale-up of Ag/ZnO films, and use in large-scale systems for water purification under UV light irradiation.

Abstract: Carbon nanotubes (CNTs) are considered as the most promising materials to solve the electromagnetic interference (EMI) issue. Various forms of CNTs including CNTs/polymer composites, metal nanoparticles-decorated CNTs and freestanding CNT buckypapers (CNT BPs) have been proposed to enhance shielding effectiveness. In this study, the synergistic effect of nickel nanoparticles (NPs) and relatively short CNTs for the enhancement of microwave shielding properties was investigated. CNT BPs were prepared by vacuum filtration of well-dispersed multi-walled CNTs and subsequently nickel was decorated on the CNT BPs (Ni/CNT) by pulsed DC sputtering technique with different deposition times of 0, 5, 10 and 15 min (hereinafter referred to as CNi0, CNi05, CNi10 and CNi15, respectively). The diameter of Ni/CNT increased from 8.74±0.53 to 72.5±3.2 nm and the conductivity improved from 9.57±0.87 to 12.57±0.59 S/cm when the nickel deposition time was 15 min. Nickel NPs were the mixed phases of nickel and nickel oxide with a dominant nickel phase. The shielding effectiveness at the frequency of 9.5 GHz achieved to -34.1 dB for CNi15. The enhancement of shielding effectiveness of CNi15 is attributed to the synergistic effect of CNTs and nickel NPs on wave dissipation

Abstract: Transparent conductive films of indium oxide (In₂O₃) are deposited on a glass substrate by RF magnetron sputtering and their electrical properties are investigated in relation to their microstructure. Sputtering deposition was carried out with variations of normalized substrate temperature (T_s/T_m where T_m is the melting temperature) and argon partial pressure (P_Ar). At a very low substrate temperature (T_s/T_m < 0.1), the columnar grains with voided grain boundaries are observed in the In₂O₃ films, which are attributed to the low surface mobility and atomic shadowing effect. With an increase in the substrate temperature, tight grain boundaries are formed between the growing columnar grains. At high temperature (0.3 < T_s/T_m < 0.5), the grain surface is faceted, which is due to the high surface mobility of the sputtered atoms, and development of preferred orientation with grain growth is promoted. The growing morphology is also dependent on the argon partial pressure. At low P_Ar deposition, an inclined fibrous grain oriented to the target direction and a smooth surface structure is developed. As the P_Ar increases, a dome-shaped surface structure and columnar grains normal to the substrate are developed due to the scattering effect of the sputtered atoms. The growing morphology with substrate temperature and argon pressure coincides with the Thornton's Structure Zone Model (SZM). The lowest electrical resistivity (2.1×10^-2 Ωcm) is observed in the In₂O₃ films with tight grain boundaries and faceted grains, which corresponds to zone II region of the SZM.

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: We have observed surface plasmon resonances (SPR) in Au thin films between 18 nm to 27 nm thick deposited onto glass substrates. The observed resonance angles are between 15.5 to 18.75 degrees, which are lower than predicted theoretical values for thicker films. The shift of resonances with the change of refractive index of surrounding confirms its application for nanobio-sensing. A thorough topological surface analysis and transmitted spectra were performed. Au thin films were annealed in Argon and the analysis repeated and compared with those from pre-annealing. The annealing process will cause a sharper appearance of surface plasmon resonances which will make these thin film devices a more suitable candidate for nanobio-sensing applications.

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: In this work, the wear behaviour of thin aluminium films deposited on stainless-steel substrate through rf magnetron sputtering is studied. The coefficient of friction and material loss are characterised as functions of the substrate temperature (Ts) of the deposited aluminium thin films. It was observed that due to the evolving microstructural and roughness properties of the films with the substrate temperature, the material behaviour of the films under extremely high wear loads significantly depend on the substrate temperature. The most significant coefficient of friction was observed at 60oC and 80oC, and highest material loss was recorded at 100oC. The material loss and variation of coefficient of friction were related to the morphology (porosity and roughness) of the sputtered aluminium thin films.

Abstract: In this paper, we propose preparation of PEGylated AuNPs by direct sputtering of Au into pure PEG with subsequent addition of amine terminated PEG. Effect of post-deposition amine addition on properties, aging and thermal stability will be discussed. Transmission electron microscopy and dynamic light scattering measurements showed that we have prepared non-agglomerated spherical NPs with size ranging from 2.9 to 5.9 nm depending on parameters of the preparation. Aging and thermal stability results revealed significant changes in the spectra after addition of PEG–NH₂. Differences in the optical absorption spectra can be assigned to change of refractive index (concentration of amine groups on NPsʼ surface) on the metal core and solvent interface with time and temperature.