ABSTRACT
The phonon DOS of polycrystalline diamond has recently been determined by Cappelletti et aL, ( 1 995 ) and is shown in Fig. 9 .2 , along with that calculated for the bond charge model. The experimental results yield relatively good agreement with the three major band positions and minima of the bond charge model. Neutron scattering resolution limits observation of details predicted for the higher optic band. The symmetry of diamond results in a single triply degenerate mode at q = 0 with Raman but no IR activity. These r25 optic modes yield a single sharp discrete line at 1 330 em-I . RS is a useful, commonly employed means for evaluating the growth of diamond phase thin films (cf. Fig. 1 0. 1 1 ) . The tensor character of the Raman process also provides a means of obtaining information about the orientational order of thin film deposits. In contrast to graphite (discussed in the next section) , first o rder RS from small nanocrystalline diamond particles with a diameter < 30 A do not appear to have been studied to date.
