Liquid-crystal alignment on a-C:H films by nitrogen plasma beam scanning

Journal Article · Sat Oct 15 04:00:00 EDT 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2115093· OSTI ID:20719577

Wu, K Y; Chen, C -H; Yeh, C -M; Hwang, J; Liu, P -C; Lee, C -Y; Chen, C -W; Wei, H K; Kou, C S; Lee, C -D ^[1]

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1. Department of Materials Science and Engineering, National Tsing Hua University, Hsin-Chu City, Taiwan (China)

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% CH{sub 4}/(H{sub 2}+CH{sub 4}) 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 O{sub 1s}, C{sub 1s}, and N{sub 1s} 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.

• OSTI ID: 20719577
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 98; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMORPHOUS STATE
ATOMIC FORCE MICROSCOPY
CARBON
CHEMICAL VAPOR DEPOSITION
FIELD EMISSION
HYDROGEN
INDIUM COMPOUNDS
LAYERS
LIQUID CRYSTALS
METALLIC GLASSES
METHANE
NITROGEN
PLASMA
RADIOWAVE RADIATION
RAMAN SPECTRA
RAMAN SPECTROSCOPY
SCANNING ELECTRON MICROSCOPY
SURFACES
THIN FILMS
TIN OXIDES