A novel route to organic-inorganic composites was described based on biomineralization of poly(ethylene glycol) (PEG)-based hydrogels. The 3-dimensional hydrogels were synthesized by radical crosslinking polymerization of poly(ethylene glycol fumarate) (PEGF) in the presence of ethylene glycol methacrylate phosphate (EGMP) as an apatite-nuclating monomer, acrylamide (AAm) as a composition-modulating comonomer, and potassium persulfate (PPS) as a radical initiator. We used the urea-mediated solution precipitation technique for biomineralization of hydrogels. The apatite grown on the surface and interior of the hydrogel was similar to biological apatites in the composition and crystalline structure. Powder x-ray diffraction (XRD) showed that the calcium phosphate crystalline platelets on hydrogels are preferentially aligned along the crystallographic c-axis direction. Inductively-coupled plasma mass spectroscopy (ICP-MS) analysis showed that the Ca/P molar ratio of apatites grown on the hydrogel template was found to be 1.60, which is identical to that of natural bones. In vitro cell experiments showed that the cell adhesion/proliferation on the mineralized hydrogel was more pronounced than on the pure polymer hydrogel.

The effects of anisotropic dielectric properties of ferroelectric Ba1-xSrxTiO3 (BST) films on the characteristics of phase shifter have been studied in microwave regions at room temperature. Ferroelectric BST films with (001) and (011) orientation were epitaxially grown on (001) and (011) MgO substrates, respectively, by pulsed laser deposition method. The structures of BST films were investigated using x-ray diffraction measurement. The microwave properties of orientation engineered BST films were investigated using coplanar waveguide transmission lines that were fabricated on BST films using a thick metal layer by photolithography and etching process. The measured differential phase shift and insertion loss (S21) for (011) BST films are larger than those for (001) BST films. Dielectric constants of the ferroelectric BST films are calculated from the measured S21 using a modified conformal-mapping model.

The ferroelectric (Ba0.6Sr0.4)TiO3 (BST) films were prepared on (001) MgO single crystals by pulsed laser deposition. Coplanar waveguide (CPW) type phase shifters controlled by external dc bias field were fabricated on BST films using a 2 μm thick metal layer to reduce metal loss. Microwave properties of the CPW phase shifter were measured using a HP 8510C vector network analyzer from 0.1 – 20 GHz. The fabricated CPW phase shifters (8 mm long) exhibited differential phase angle of 100 ° at 10 GHz with a dc bias field of less than 80 kV/cm between center and ground conductors. Furthermore, a stable differential phase angle (102 ± 3.5 o) was observed from another CPW while changing the power of incident microwave from -10 to +30 dBm. Gap size dependent dielectric constant of the BST film was observed and a simple correction method was suggested in the paper. These results demonstrate the possible application of ferroelectric tunable devices on a high power tunable wireless telecommunication.

Due to growth tensile stress, which evolves in diamond films during deposition, thick diamond films are easily cracked. In this study we successfully prevented growth cracks by introducing thermal compressive stress with step-down control of deposition temperatures during growth. Three deposition temperature drops of 10 °C each during deposition enabled us to successfully synthesize crack-free four-inch diamond wafers several hundred micrometers in thickness. This method is very simple and may be applicable to coating of films of various materials different from those of substrates.

The deposition area of diamond film is increased by applying a geometry of multiple cathodes and a single anode in direct current (dc) plasma assisted chemical vapor deposition (PACVD). Each cathode is made of Ta and connected independently to its own dc power supply. The operating pressure is 1.3 × 104 Pa (100 Torr), and methane-hydrogen mixed gas is used as reaction gas. The voltage and the current applied to each cathode are 650 V and 4 A, respectively. The transition from a diffuse glow to an arc is prevented by maintaining cathode temperatures above 2000 °C, which inhibits carbon deposition on the cathodes. Translucent diamond film of 3 in. diameter, thicker than 200 μm, is grown using seven cathodes with 3% CH4–H2 mixed gas for 110 h. The deposition area can be increased further by increasing the number of cathodes.

Elastic modulus and Poisson's ratio of diamond-like carbon (DLC) film was measured by a simple method using DLC bridges which are free from mechanical constraint of substrate. The DLC films were deposited on Si wafer by C6H6r.f. glow discharge at the deposition pressure 1.33 Pa. Because of the high residual compressive stress of the film, the bridge exhibited a sinusoidal displacement by removing the constraint of the substrate. By measuring the amplitude with known bridge length, we could determine the strain of the film required to adhere to the substrate. Combined with independent stress measurement by laser reflection method, this method allows calculation of the biaxial elastic modulus, E/(1–v), where E is the elastic modulus and v Poisson's ratio of the DLC film. By comparing the biaxial elastic modulus with plane-strain modulus, E/(1–v2), measured by nano-indentation, we could further determine the elastic modulus and Poisson's ratio, independently. The elastic modulus, E, increased from 87 to 133 GPa as the negative bias voltage increased from 400 to 550 V. Poisson's ratio was estimated to be about 0.20 in this bias voltage range. For the negative bias voltages less than 400 V, however, the present method resulted in negative Poisson's ratio which is physically impossible. The limitation of the present method was also discussed.

A simple method to measure the elastic modulus and Poisson's ratio of diamond-like carbon (DLC) films deposited on Si wafer was suggested. This method involved etching a side of Si substrate using the DLC film as an etching mask. The edge of DLC overhang free from constraint of Si substrate exhibited periodic sinusoidal shape. By measuring the amplitude and the wavelength of the sinusoidal edge, we can determine the strain of the film required to adhere to the substrate. Combined with independent stress measurement by laser reflection method, this method allows calculation of the biaxial elastic modulus, E/(1 − v), where E is the elastic modulus and v Poisson's ratio of the DLC films. By comparing the biaxial elastic modulus with plane-strain modulus, E/(1 −v2), measured by nano-indentation, we could further determine the elastic modulus and Poisson's ratio, independently. This method was employed to measure the mechanical properties of DLC films deposited by C6H6 r.f. glow discharge at the deposition pressure 1.33 Pa. The elastic modulus, E, increased from 94 to 128 GPa as the negative bias voltage increased from 400 to 550 V. Poisson's ratio was estimated to be about 0.22 in this bias voltage range. For the negative bias voltages less than 400 V, however, the present method resulted in negative Poisson's ratio. The limitation of the present method was discussed.

Tribochemical reactions between Si incorporated diamond-like carbon (Si–DLC) films and steel ball were investigated during initial stage of tribo-test. The films were deposited by r.f.–PACVD using mixtures of diluted silane (SiH4:H2=10:90) and benzene gases. Si concentration in the film was varied from 0 to 10 at.% by adjusting the diluted silane fraction in the reaction gases. A rotating type ball-on-disk wear rig was employed for the tribo-test in ambient atmosphere. When the Si concentration was less than 5 at.%, initial transient period of high friction coefficient was commonly observed. After the transient period, the friction coefficient becomes lower with increasing contact cycles. The initial transient period becomes shorter and the starting and maximum friction coefficients in transient period decreased with increasing Si concentration. Composition of the debris on the wear scar surface was analyzed by Auger spectroscopy at various stages in the initial transient period. We observed that when the friction coefficient increased in earlier stage of the transient period, iron and oxygen was observed in the debris. However, decrease in the friction coefficient in the later stage of the transient period was associated with the formation of silicon rich oxide debris. This result supports the friction mechanism of Si-DLC films that the formation of Si rich oxide debris results in low friction coefficient in ambient atmosphere.

Nitrogen incorporated diamond-like carbon (DLC) films were deposited by r.f. plasma assisted chemical vapor deposition (r.f.-PACVD) method. Mixtures of benzene and ammonia or nitrogen were used as the reaction gases for the deposition. Composition, atomic bond structure and mechanical properties of the film were investigated when the fraction of nitrogen source increases from 0 to 0.79. All films were deposited at fixed negative bias voltage of the cathode (-500 V) and the deposition pressure (10 mTorr). While ammonia addition reduces both residual stress and hardness of the film from 1.7 to 1 GPa and from 2750 to 1700 Kgf/mm2 respectively, the mechanical properties are not significantly varied by nitrogen addition. Deposition rate, composition and atomic bond structure are also dependent on the nitrogen source gases. Observed behavior of mechanical properties is discussed in terms of the content of inter-links of sp2 clusters. In addition to hydrogen, C≡N bonds in the film are also terminated sites of three dimensional atomic bond network. By considering the hydrogen concentration and the C≡N bonds, it can be shown that the mechanical properties of nitrogen incorporated DLC films are determined by the content of inter-links of sp2 clusters.

In order to characterize friction and wear behavior between cylindrical specimens and flexible counterface materials such as magnetic tape, a tribometer is suggested. The tribometer is used to investigate the behavior between video cassette recorder (VCR) head drums and VCR tapes. Friction coefficients of uncoated and diamond-like carbon (DLC) film coated head drums of Al alloy are compared before and after a wear test. Before the wear test, an uncoated head drum shows friction coefficients ranging from 0.22 to 0.3 as the applied tension increases from 200 to 600 gf at the sliding speed of 0.16 m/s. The friction coefficients of DLC coated head drum are 14 to 30 % lower than those of uncoated head drums. At the sliding speed of 4.9 m/s, the friction coefficients of both uncoated and DLC coated drums are reduced to less than 0.1. After the wear test, however, the friction coefficients of uncoated head drums increase to the range from 0.3 and 0.47 depending on the applied tensions. Furthermore, the friction coefficients are not reduced even at the high sliding speed of 4.9 m/s. DLC coated head drums, on the other hand, exhibit similar friction coefficients to those before the wear test. Degradation of frictional property in the uncoated head drum is discussed in terms of the surface damages mainly due to magnetic metal oxide particles transferred from VCR tapes. This result shows that the DLC coating of VCR head drum can improve the friction and wear properties. It is also observed that the DLC coating can reduce the damage of VCR tapes.

Residual compressive stress of diamond-like carbon (DLC) films was measured by beam deflection method. DLC films were deposited on thin Si wafers using r.f. plasma decomposition of methane and benzene. Negative bias voltage of the cathode was varied from -100 to -800 V and deposition pressure from 3 to 100 mTorr. When using benzene as precursor gas, the residual stress monotonically increases as increasing . (Here, Vb is the negative bias voltage of cathode and P the deposition pressure.) In case of using methane, however, the residual stress has a maximum value at between 70 and 100 V/mTorr1/2. Because of the difference in molecular size between benzene and methane, the mean free path of ions in benzene discharge is 5 times shorter than that in methane discharge. The contrasting behavior of residual stress is discussed in terms of the difference in ion energies at the specimen surface due to the difference in mean free path. On the other hand, total hydrogen concentration decreases as increasing in both cases. This result thus shows that the total hydrogen concentration cannot be a key to understand the behavior of residual stress.