STRUCTURAL CHARACTERIZATION AND TRANSPORT-PROPERTIES OF DIAMOND FILMSPREPARED BY DC PLASMA GLOW-DISCHARGE CVD

We present in this paper results of characterization of CVD diamond fi lms prepared with a de plasma glow discharge method at different metha ne concentrations and substrate temperatures. SEM analysis combined wi th x-ray diffraction measurements and micro-Raman spectroscopy have be en used to determine the morphology and texture of three diamond sampl es prepared at a constant methane to hydrogen ratio (3.8 vol%). The ch ange of the morphology with substrate temperature in the range 950-110 0 degrees C is consistent with reported measurements performed on diam onds prepared by microwave-enhanced CVD, This confirms the assumption that the structural properties of CVD diamond are tunable with the dep osition parameters and do not depend on the particular method of plasm a activation. Micro-Raman spectroscopy combined with I-V measurements depicts the transport process as conduction along grain boundaries due to low-resistivity graphite-like phases. The resistivity is found to increase with decreasing growth rate up to a value of 10(13) Ohm cm fo r a deposition rate of 10-20 mu m/h. Thus, the rate of growth is regar ded as a quality parameter, which takes into account the combined effe cts of methane concentration and substrate temperature at constant pow er density. The leakage currents for the sample with higher resistivit ies are still dominated by the contribution of the nondiamond carbon p hases at room temperature and by nitrogen impurities al higher tempera tures.