The electrical conduction mechanism for the polycrystalline diamond membrane in the voltage range of ± 50 V

Polycrystalline diamond films were deposited on the silicon substrate using a methane/hydrogen gas mixture in a microwave plasma-assisted chemical vapor deposition system. The polycrystalline diamond membrane was obtained by etching the backside of the silicon wafer with KOH solution. The conduction mechanisms for the Al/diamond/Al sandwich structure of the polycrystalline diamond membrane were established in the voltage range of -300 to 300 V. The equivalent circuit for the polycrystalline diamond membrane was represented by a back-to-back Schottky diode for the bulk diamond crystallites, in parallel with the grain boundary impedance for the diamond grain boundaries. It was found that the field-activated transport mechanism, in which the grain boundary impedance can be represented by the modified Frenkel-Poole equation, was for the diamond grain boundaries. The electrical conduction properties of the bulk diamond crystallites was found to be expressed by the Schottky emission conduction mechanism with the generation current, which played an important role in the low voltage measurement region of ± 50 V.