Grain-Size-Dependent Diamond-Nondiamond Composite Films: Characterization and Field-Emission Properties

Diamond Films with grain sizes in the range of 5-1000 rim and grain boundaries containing nondiamond carbon are deposited on a silicon substrate by varying the deposition parameters. The overall morphologies of the as-deposited diamond-nondiamond composite films are examined by scanning electron microscopy and atomic force microscopy, which show a decrease in the surface roughness with a decrease in the diamond grain size. Although the Raman spectra show predominately nondiamond carbon features in the diamond films with smaller grain sizes. glancing-angle X-ray diffraction spectra show the absence of graphitic carbon features and the presence of very small amorphous carbon diffraction features. The CH(4) percentage (%) in Ar and H(2) plasma during deposition plays a crucial role in the Formation OF diamond films with different grain sizes and nondiamond carbon contents, which, in turn, determines the field emission behavior of the corresponding diamond films. The smaller the grain size of the diamond, the lower is the turn-on held for electron emission. A lower turn-on field is obtained from the diamond films deposited with 2-5% CH(4) than from the films deposited with either, 1% or 7.5% CH(4) in the Ar medium, A current density greater than 1 mA/cm(2) (at 50 V/mu m) is obtained from diamond films deposited with a higher percentage of CH(4). A model is suggested For the field-emission mechanism from the diamond-nondiamond composite films with different diamond grain sizes and nondiamond contents.