Chemically vapor deposited diamond-tipped one-dimensional nanostructures and nanodiamond–silica–nanotube composites

Composite thin films of nanodiamond and silica nanotubes were synthesized by means of microwave plasma assisted chemical vapor deposition (MPCVD) on silica nanotube matrix that was seeded with nanodiamond particles. SEM, Raman spectroscopy, and EDX were used to analyze the composite. Wet chemical etching was applied to selectively remove exposed silica from the composites for further revealing the nanostructure of the composites. Nanodiamond grew around silica nanotubes and filled the space left between silica nanotubes to form a continuous film. When appropriately selected sizes of nanodiamond particles were used as diamond seeds, silica nanotubes capped with CVD-grown diamond crystals were also obtained. Potential applications and implication of composites of nanodiamond and 1-D nanostructures will be discussed.     

Ultrathin DLC and SiOx layer deposition on poly(ethylene terephthalate) and restriction of surface dynamics

The hydrophilicity of oxygen plasma‐reated polymer surfaces decays with storing time in air environments. Because they are dense, highly crosslinked, and chemically stable, diamond‐like carbon (DLC) films and silicon oxide films (SiO_x) were deposited on poly(ethylene terephthalate) by plasma‐enhanced chemical vapor deposition to restrict polymer surface dynamics. In this study, the effects of ultrathin films on surface dynamics of these polymers were investigated. The layers were deposited on substrates with thickness below 100 Å. The thickness of films was measured with a scanning analyzer ellipsometer, while ATR‐IR spectroscopy and Raman spectroscopy were performed to observe the chemical structure of the films. Films below 50 Å were also shown to be effective in stabilizing the plasma treated polymer surfaces. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1158–1164, 2000     

Effect of chelating agents on the preferred orientation of ZnO films by sol-gel process

The effect of chelating agents of ZnO precursor solutions on crystallization behavior was investigated. Two different additives, monoethanolamine (MEA) and diethanolamine (DEA), and crystalline Pt (111)/Si and amorphous SiN _x /Si substrates, were used for this study. ZnO film grown on SiN _x /Si from a DEA-chelated precursor solution shows a poorly oriented microstructure with weak crystallization peaks, while ZnO film grown on Pt(111)/Si shows a c-axis preferred orientation. In the case of ZnO films prepared with a MEA-chelated precursor solution, all films show a strong preferred orientation irrespective of substrate type. This result clearly demonstrates the role of the chelating agent on the crystallographic orientation and crystallization behavior of sol-gel processed ZnO films.     

High breakdown voltage Schottky rectifier fabricated on bulk n-GaN substrate

Vertical Schottky rectifiers have been fabricated on a free-standing n-GaN substrate. Circular Pt Schottky contacts with different diameters (50 μm, 150 μm and 300 μm) were prepared on the Ga-face and full backside ohmic contact was prepared on the N-face by using Ti/Al. The electron concentration of the substrate was as low as 7 × 10¹⁵ cm⁻³. Without epitaxial layer and edge termination scheme, the reverse breakdown voltages (V_B) as high as 630 V and 600 V were achieved for 50 μm and 150 μm diameter rectifiers, respectively. For larger diameter (300 μm) rectifiers, V_B dropped to 260 V. The forward turn-on voltage (V_F) for the 50 μm diameter rectifiers was 1.2 V at the current density of 100 A/cm², and the on-state resistance (R_on) was 2.2 mΩ cm², producing a figure-of-merit (V_B)²/R_on of 180 MW cm⁻². At 10 V bias, forward currents of 0.5 A and 0.8 A were obtained for 150 μm and 300 μm diameter rectifiers, respectively. The devices exhibited an ultrafast reverse recovery characteristics, with the reverse recovery time shorter than 20 ns.