THE FIELD-EMISSION CHARACTERISTICS OF A-C-H THIN-FILMS PREPARED BY HELICAL RESONATOR PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

The field emission characteristics of hydrogenated amorphous carbon (a -C:H) films prepared by helical resonator-plasma enhanced chemical vap or deposition (HR-PECVD) are examined. a-C:H films are deposited with CH4/H-2 and CH4/Ar gases under different substrate RF bias conditions. The properties of a-C:H films are investigated by Raman spectroscopy, Fourier transform IR (FT-IR), UV spectroscopy and elastic recoil dete ction (ERD). Field emission characteristics of a-C:H coated on Si whis kers which are grown by the vapor-liquid-solid (VLS) method are tested under ultrahigh vacuum. Highly efficient field emission characteristi cs are achieved in the specimen deposited at a substrate RF bias highe r rather than in the ground deposition condition regardless of the nat ure of the reactant gas. As the substrate RF bias is changed from grou nd to a higher RF substrate bias, the deposited a-C:H films have lower hydrogen contents and higher sp(2)-bonds. Therefore, the field emissi on characteristics of a-C:H thin films are affected by the hydrogen co ntents of the films rather than by the sp(3)/sp(2) ratio.