Ohmic contact to nitrogen doped amorphous carbon films

Abstract

Nitrogen doped amorphous carbon (a-C:N) films are potentially useful electrode materials for electrochemical analysis which can be used in micro-fluid bio-detection chip. An ohmic contact between the carbon film and electrical circuitry is required so that voltage drops and currents at the interface between film and chemical solution can be reliably measured. The main objective of this study is to investigate several electrical contacts on the a-C:N films, to find a method to fabricate ohmic contact on a-C:N films. The a-C:N films were deposited with a filtered cathode vacuum arc (FCVA) operating in a nitrogen atmosphere, and a DC pulse bias of 0 to −3.0 kV was applied to the substrate. The sandwich structures of Ti/a-C:N/Ti and Al/a-C:N/Al were fabricated to study the contact between metal and a-C:N films by measuring their I– V characteristics. The highly conductive silicon (N type) with resistance of <0.006 Ω cm was used in sandwich structures of Si/a-C:N/Ti (and Al) to examine the electrical contact between the highly conductive silicon and a-C:N films. Ti/A-C:N/Ti and Al/a-C:N/Al show typical ohmic behavior and Schottky barrier behavior, respectively. The highly conductive silicon is therefore not an ideal substrate and an interlayer of Ti on the silicon wafer is suggested for electrochemical applications.