The Raman spectrum of amorphous diamond

We present the Raman spectrum of an amorphous, fully sp(3)-bonded carbon network. The reduced Raman spectrum agrees closely with the calculated density or states of diamond. The results have been obtained from nanoclusters produced deep inside a single crystal diamond irradiated with MeV He ions. The deep implantation creates amorphous sp(3) bonded C clusters along the ion tracks, within a largely intact diamond matrix. The matrix maintains the clusters under high pressure, preventing the relaxation to sp(3) bonded structures. Sharp peaks associated with defect structures unique to MeV ion implantation are observed at 1422, 1447, 1467, 1496, 1540, 1563, 1631, 1649, 1683 and 1726 cm(-1). We also observe a shoulder in the reduced Raman spectrum at ca 1120 cm(-1) which we tentatively attribute to surface phonon modes. The results provide the Raman signature that might be expected from tetrahedrally bonded amorphous carbon films with no graphite-like amorphous components. (C) 1998 Elsevier Science S.A.