CORRELATION BETWEEN BREAKDOWN VOLTAGE AND STRUCTURAL-PROPERTIES OF POLYCRYSTALLINE AND HETEROEPITAXIAL CVD DIAMOND FILMS

The dielectric strength of both non-oriented polycrystalline (grain si ze less than 100 nm) and highly textured diamond films (grain size abo ut 2 mu) which have been epitaxially nucleated on silicon(100) has bee n investigated by the ramping method at room temperature. We show that annealing in air or etching in CrO3 + H2SO4, which drastically increa ses the resistivity of the samples in comparison with the as-grown sta te, has no significant effect on the breakdown voltage. Besides this, the dependence of the dielectric strength on the film thickness has be en studied. We observe a pronounced reduction of the dielectric streng th from 4 x 10(6) V cm-1 to about 1 x 10(6) V cm-1 for film thicknesse s ranging from 150 nm to 2 mum respectively.