Bao-Shun Yau

Reactive magnetron sputtering of indium tin oxide films on acrylics – morphology and bonding state

Abstract Indium tin oxide (ITO) films were deposited on acrylics by low temperature reactive magnetron sputtering. The effects of oxygen flow and bias voltage on the microstructure, surface morphology and bonding state of films were evaluated. In this investigation, X-ray photoelectron spectroscopy, X-ray diffraction, Atomic force microscope were used. It was found that the grain size of ITO films increased and surface roughness decreased with the increase of oxygen flow rate. The XPS spectra of In 3d and Sn 3d indicated that the oxygen flow had little effect on the binding energy of ITO films. The relative strength of O 2− II increased, while that of O 2− I decreased with increasing oxygen flow rate. The grain size increased with the bias voltage. However, at a maximum voltage of −90 V fine grains were detected due to the formation of numerous nuclei resulting from bombardment of high energy particles. The bias voltage had little effect on the bonding state of In, Sn and O ions.

The electromagnetic shielding effectiveness of indium tin oxide films

Indium tin oxide (ITO) films were deposited on acrylics by low temperature reactive magnetron sputtering. The influence of film thickness on the shielding effectiveness of the films was investigated. The electric conductivity increased with ITO film thickness. This is probably due to the scattering of charge carriers by the external surfaces of thin films which is higher for films with smaller thickness. Results of magnetic moment versus magnetic field suggested that ITO film is basically a non-magnetic material. An increase in reflection loss with film thickness was observed, which was very similar to that observed for the electrical conductivity. The absorption loss was extremely small when compared with the reflection loss and therefore could be neglected when considering the total shielding effectiveness.

Effects of nitrogen flow on R.F. reactive magnetron sputtered silicon nitride films on high speed steel

Silicon nitride films were deposited on high speed steel by r.f. reactive magnetron sputtering. The effects of nitrogen flow rate on the deposition rate, chemical composition, microstructure and mechanical properties were evaluated. The deposition rate, nitrogen content, hardness and reduced elastic modulus decreased with increasing nitrogen flow rate. The decrease of coating hardness could decrease constraint stress, and hence decrease the shear stress at the interface, which resulted in higher critical load.

Reactive magnetron sputtering of indium tin oxide films on acrylics—Electrical resistivity and optical properties

The effects of processing parameters on the deposition rate lattice parameters, stoichiometric compositions, surface morphology, and bonding state of indium tin oxide (ITO) films on acrylics had been previously reported. This study was a continuation of the previous investigation and focused on the electrical resistivity and optical properties of ITO films.The electrical resistivity decreased and then increased with oxygen flow rate. This was due to the effects of oxygen vacancies and impurity scattering. The resistivity of ITO films decreased with the applied bias voltage and film thickness. The transmittance of visible light increased with the oxygen flow rate and decreased with film thickness. Films deposited at oxygen flow rates having low electrical resistivity also had higher infrared radiation (IR) reflectance.

Effects of substrate bias on nanocrystal-(Ti,Al)N x / amorphous-SiN y composite films

Nanocrystal-(Ti,Al)N x /amorphous-SiN y composite films were prepared in a codeposition process under different substrate bias voltages. The effects of substrate bias voltage on the deposition rate, composition, microstructure, and mechanical properties of nanocomposite films were investigated. Results indicated that the films with bias voltages caused resputtering due to the bombardment of high-energy ions on film surface. The resputtering effect had substantial influence on deposition rate, surface morphology, and composition of films. The films with (220) preferred orientation were also observed as the applied substrate bias voltages exceeded 50 V. As the substrate bias voltage increased, the nanocrystallite size increased, lattice strain raised, and the hardness decreased.

Field emission of micro aluminum cones coated by nano-tips of amorphous diamond

Abstract Nano-tips of amorphous diamond films were deposited on Al micro cones to form a metal/diamond interface structure. The amorphous diamond films were deposited by cathodic arc at a temperature less than 150 °C. The turn on applied field was 4.5 V/μm at 10 μA/cm2 for the Al/diamond structure. The turn on applied field is approximately 10 times lower than that for Al alone. The high emission current was obtained (50 mA/cm2) due to metal/diamond structure and the presence of defect band within band gap of amorphous diamond that allowed electrons to pass through with little hindrance. Moreover, the stability of electron emission was monitored at electrical field strength of 7 V/μm for 100 h. The fluctuations of long-term emission current were at ±4% during the entire duration of monitoring. The fluctuation may be due to the absorption and desorption of molecules by the dangling bonds of carbon atoms on surface of nano-tips of amorphous diamond in a vacuum chamber during electron emission. The high stability of electron emission form micro Al cones by nano-tips amorphous diamond coatings was observed.

Investigation of nanocrystal-(Ti,Al)N1−x/amorphous-SiNy composite films

Nanocrystal-(Ti,Al)N1−x/amorphous-SiNy composite films were prepared by the magnetron sputtering codeposition process. The effects of deposition parameters on the composition, microstructure, and mechanical properties of nanocomposite films were investigated. Results indicated that the composition of nanocomposite films could be controlled through the codeposition process. Nanocrystal (Ti,Al)N1−x embedded in amorphous SiNy matrix with (200) preferred orientation was observed. The content of amorphous SiNy has substantial influence on the nanocrystallite size, columnar structure, surface morphology, and hardness.

Effects of nitrogen flow rates on reactively sputtered nanocrystal-(Ti,Al) x N 1- x /amorphous-Si y N 1- y nanolaminate films

Nanocrystal-(Ti,Al) x N 1- x /amorphous-Si y N 1- y nanolaminate films were deposited periodically under different nitrogen flow rates. The composition, microstructure and mechanical properties of nanolaminate films were investigated by x-ray photoelectron spectroscope, x-ray diffractometer, scanning and transmission electron microscopy, atomic force microscope, and nanoindentation apparatus. Results indicated that the formation of the compound on the target surface was substantially influenced by the deposition rate, composition and crystallite size of the nanolaminate films. Nanolaminate structure with periodic compositional modulation and sharp interfaces were deposited at different nitrogen flow rate. Smaller nanocrystallite size, round-shaped grain features, smoother surface morphology, higher hardness, and reduced elastic modulus were obtained for nanolaminate films with increasing the nitrogen flow rate.