Alternating-current and direct-current electrical transport properties of diamond diodes with diamond surfaces of the different morphology

Abstract

The alternating current (ac) conductance (f=200 Hz) was measured as a function of applied voltage at ambient temperature for two diodes with aluminium/diamond rectifying contacts on chemical vapour-deposited diamond films of 5 μm in thickness with different morphology, nucleation and growth surfaces. Comparison of direct current (dc) conductance curves (deduced from experimental current–voltage curves) with ac conductance curves for the diodes revealed different transport mechanisms for two interfaces. The current–voltage characteristic of gold/diamond/gold structures shows that the two interfaces have different resistance values. The results demonstrate that the nucleation surface has a greater surface density of states than the growth surface, and this contributes to electrical transport through the potential barrier. Cole–Cole curves show a discrepancy between the Debye semicircle and experimental results and illustrate the fundamental differences between the two diodes. These results provide additional proof that the principal source of dispersion admittance is the surface states. The current–voltage characteristic of diamond diodes with diamond films of 1 μm in thickness shows two distinct resistance states (high and low resistance). By applying an appropriate bias, resistance switching from one state to the other state can be achieved. The experimental results are discussed on the basis of filamentary conduction