Bombarding energy dependence of bonding structure in amorphous carbon interlayer and its effect on diamond nucleation

Abstract

The bombarding energy dependence of bonding structure in amorphous carbon interlayer and its effect on diamond nucleation density (Nd) were studied. Amorphous carbon (a-C) interlayer was deposited by magnetron sputtering. Interestingly, the intensity ratio (I-D/I-G) Of the D band (similar to 1400 cm(-1)) to the G band (1570 cm(-1)) in the Raman spectra and the optical band gap of the a-C film were found to be inversely proportional to the sputtering power, that is, to bombarding energy, When diamond was subsequently deposited at 800 degrees C by microwave plasma chemical vapor deposition (CVD), diamond could be grown only on the interlayers with higher I-D/I-G (greater than or equal to 2.20), and Nd was increased up to 2 x 10(6)/cm(2) with the increase of I-D/I-G ratio, that is, with the decrease of the bombarding energy. We experimentally confirmed that the amount of the sp(3) bonded carbon clusters within the interlayer was dependent on the bombarding energy of the particles, determining the diamond nucleation density. We suggest that the transformation of the amorphous carbon into graphitic carbon should be effectively prevented for the diamond nucleation on the a-C interlayer.