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A plasma beam scanning treatment has been developed to modify the surface of the hydrogenated amorphous carbon (a-C:H) film on the indium tin oxide glass. The plasma beam scanning treatment makes the a-C:H film an excellent layer for liquid-crystal alignment. The qualities of a-C:H films were characterized by using atomic force microscope, micro-Raman spectroscopy, and field-emission scanning electron microscope. The ultrathin a-C:H films were deposited at 50% CH4/(H2+CH4) gas ratio, 100 W radio-frequency power, and a gas pressure of 10 mtorr for 15 min by capacitive-coupled plasma chemical-vapor deposition method. The twist nematic cells were filled with liquid crystal (ZLI-2293) on the a-C:H film treated with different nitrogen plasma beam scanning time. The grooving mechanism is considered not responsible for the liquid-crystal (LC) alignment. Raman spectra suggest that a bond-breaking process of aromatic rings occurs in the a-C:H film. The O1s, C1s, and N1s core-level spectra support that the nitrogen plasma beam scanning treatment induces a bond-breaking process of aromatic rings to create available carbon dangling bonds for the formation of C–O bonds. The newly formed C–O bonds are “directional,” which favor the LC alignment on the a-C:H film. [ABSTRACT FROM AUTHOR]

Amorphous-carbon (a-C) nanotips were directly grown on copper substrates by microwave plasma-enhanced chemical-vapor deposition. The length of a typical a-C nanotip is ∼250 nm and its tip diameter is ∼25 nm. The in-plane correlation length La, equivalent to the size of the sp[sup 2] clusters, is determined to be 1.2 nm through the intensity ratio of the D and G peaks in the Raman spectrum, which is about in the optimum range for field emission. A low turn-on field of 1.6 V/μm at 10 μA/cm2, a threshold field of 3.8 V/μm at 10 mA/cm2, and a high current density of 32.42 mA/cm2 at 4.0 V/μm are achieved. The field emission characteristics of a-C nanotips are close to those of carbon nanotubes, and much better than what has been reported for flat diamond-like carbon or a-C:H coated cathodes. The roles of the sp[sup 2] cluster size, electron confinement and conductivity in the field emission of a-C nanotips are discussed. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The surface of highly ordered pyrolytic graphite (HOPG) was modified by Ar plasma beam scanning at a controllable angle of incidence. The characteristics of plasma modified HOPG were investigated by atomic force microscope (AFM), micro-Raman, X-ray photoemission spectroscopy (XPS), and grazing incident angle of X-ray diffraction (GIAXRD). A smooth surface of HOPG can be obtained by adjusting the incident angles of Ar plasma beam scanning. The surfaces of HOPG become smoother with increasing angle of incidence after Ar plasma beam scanning. Raman spectra indicate that the plasma beam scanning breaks the hexagonal structures of sp2 C=C bonds near the surface of HOPG. The broken hexagonal network structures can form C–O bonds that increase the amount of oxygen on the surface of HOPG, supported by C1s and O1s XPS spectra. GIAXRD data support that the co-existence of both crystalline structures of 2H and 3R in HOPG. The carbon bond breaking in 2H and 3R is different and depends on the angle of incidence. Most broken carbon bonds form damaged aromatic rings near the surface of HOPG. [ABSTRACT FROM AUTHOR]