Advanced Materials Research Vols. 26-28

Abstract: Ta-Al-N thin films on Si wafer were prepared by RF reactive magnetron sputtering in a N2/Ar ambient. Then the stacked structures of Cu/Ta-Al-N/Si were prepared and annealed at temperatures varied from 400°C to 900°C for 5 minutes in a N2 ambient tube. Four-point probe (FPP) sheet resistance measurement, Atomic force microscope (AFM), Scanning electron microscope(SEM), Alpha-Step IQ Profilers and X-ray Diffraction(XRD) were used to investigate the composition, morphology and the diffusion barrier properties of the thin films. The results show that with the increasing of Al component, the surface of Ta-Al-N thin-films became finer, the sheet resistance became higher, and after annealing at 800°C/300S FA, Cu diffusion through Ta-Al-N barrier didn’t not occurred. Results show that Ta-Al-N thin-films could act as diffusion barrier for new generation integrated circuits due to its excellent high temperature properties.

Abstract: Orthorhombic Bi2S3 (bismuthinite) nanorods and nanowires were synthesized by the solventless thermolysis of bismuth alkylthiolate precursors. Reactions producing high aspect ratio nanowires were carried out in air at 225°C with the presence of a capping ligand species, octanoate. Nanorods with a lower aspect ratio were produced by the same approach with the addition of elemental sulfur at a lower temperature (~160°C). Current density –Voltage characterization of the devices under illumination with 500 W Xenon lamp showed the photovoltaic performance. Both the nanorods and the nanowires hybrid with the polymer show the improved photovoltaic performance than polymer only. As far as we know, we are the first to apply Bi2S3 nanorods and nanowires to solar cells with the structure of ITO/PEDOT:PSS/MDMO-PPV:Bi2S3/Al.

Abstract: The practical uses of soft magnetic composite(SMC) for an electrical motor is presented in this paper. SMC allows obtaining improved stator and core shapes as well as totally new design concepts such as claw pole motor. However, a major disadvantage of soft magnetic composites was their weak strength. In this study, spark plasma sintering (SPS) was utilized to improve the strength of SMC. Advantages of the SPS process over other conventional sintering process are the faster heating and cooling rates ensured and higher pressure applied during the sintering procedure. This allows obtaining high strength products in short periods of time to meet with industrial application without insulation destruction. This paper introduces the development of high strength soft magnetic composite motor core and examples of practical application for industries. The result showed that the SPS process increased the fracture strength, about 1.3 to 1.7 times, of SMC compare to the conventional compaction. Also we derive method to reduce the iron loss in the SPS sintering process using control forming temperature. As the forming temperature decreased from 500°C to 300°C, reduction of iron-loss was obtained from 192W/kg to 21W/kg by using SPS sintering process. Moreover, with increased the SPS sintering process pressure value from 250MPa to 800MPa which is the conventional compaction condition and decreased forming temperature to 200°C, iron-loss was measured. The results showed that iron-loss was obtained 11.42W/kg and it was similar value of conventional compaction results.

Abstract: Diamond coatings on pure titanium substrates are of interest for tribological and biomedical implants. However, due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density, it is hard to deposit adherent thin diamond layers on titanium. The aim of the present research was to successfully produce smooth and well adherent nanocrystalline diamond (NCD) film on a pure Ti substrate using the microwave plasma chemical vapor deposition (MWPCVD) method. The influence of Argon addition to CH4/H2 plasma on the crystallinity, morphology and growth of the diamond film deposited by MWPCVD was investigated using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Xray diffraction (XRD) and Raman spectroscopy.

Abstract: SiO2 coatings and double layer films of SiO2/Si3N4 have been designed and prepared on sapphire (α-Al2O3) by radio frequency magnetron reactive sputtering in order to improve the optical and mechanical properties of infrared windows of sapphire. The transmission of the coated and uncoated sapphire in the wavelength range from 2.5 to 6.7um was determined. Surface morphology and roughness of coated and uncoated sapphire have been measured using a talysurf. The flexure strength of coated and uncoated sapphire samples has been studied by 3-point bending tests at room temperature and high temperatures. The results show that the coatings can improve the surface morphology and reduce the surface roughness of sapphire substrate. What’s more, the designed single layer of SiO2 film and two-layer of SiO2/Si3N4 films can both increase the transmission of sapphire in mid-wave IR and strengthen sapphire at high temperatures. Coated sapphire transmits over 95% at wavelength from 3 to 5um for the two designs. Flexure tests reveal that SiO2 coatings and SiO2/Si3N4 films increase the strength of c-axis sapphire by a factor of about 1.5 and 1.4, respectively, at 800°C.

Abstract: Amorphous Si films are generally deposited on glass by physical or chemical vapor deposition. When annealed, they undergo crystallization through nucleation and grain growth. At low annealing temperatures, crystallization starts near the glass substrates for pure Si films and near metals for metal-induced crystallization. In this case, crystallites grow along the <111> directions of c-Si nearly parallel to the film plane, that is, the directed crystallization. The directed crystallization is likely to develop the <110> or <111> orientation, which means the <110> or <111> directions are along the film thickness direction. As the annealing temperature increases, equiaxed crystallization tends to increase, which in turn increases random orientation. When the annealing temperature is further increased, the <111> orientation may be obtained.

Abstract: This paper reports that Zn ion implantation to a dose of 1 × 1017 ions/cm2 was performed on highly c-axis-orientated ZnO thin films deposited on Si (100) substrates by the sol-gel technique. After ion implantation, the as-implanted ZnO films were annealed in argon ambient at different temperatures from 300−500 oC. The effects of ion implantation and post-implantation annealing on the structural and luminescent properties of the ZnO films were investigated by x-ray diffraction, photoluminescence (PL). Results show that the intensities of (002) peak and photoluminescence (PL) were evidently decreased by Zn ion implantation. The recovery of (002) peak and photoluminescence occurs at ~300oC.

Abstract: Carbon doped TiO2 and pure TiO2 thin films were prepared by atmospheric metal organic chemical vapor deposition (MOCVD) method. Both pure TiO2 and carbon doped TiO2 films are in anatase structure. X-ray photoelectron spectra (XPS) of the carbon doped TiO2 film indicate carbon atoms occupy oxygen sites and form Ti-C bonds in TiO2 lattice. In UV-VIS absorption spectra, it can be found that the carbon doped TiO2 film has a red-shifted absorption edge compared with the pure TiO2 film. In the photocatalytic decomposition experiment of Rh.B, carbon doped TiO2 exhibited remarkably visible light activity.

Abstract: This paper discusses the effect of plating condition on the mechanical properties and residual stress of electroplated Cu film. The inlaid copper structure was fabricated on silicon wafer where silicon oxide was thermally grown. Seed layer was deposited by sputtering method followed by copper electro-deposition. Copper was electrodeposited with IBM paddle type electroplating machine Residual stress, hardness, elastic modulus, and surface roughness of electroplated copper film were investigated at various organic additives in plating solution and current types with a nanoindenter and a surface profilometer. The dishing amounts in chemical mechanical polishing (CMP) was also investigated at various additives. The results show that, in the case of residual stress, the copper film deposited at higher additive or PC current result in lower residual stress. The additives do not significantly affect the mechanical properties of Cu deposit.