The Conduction Mechanisms in Undoped Polycrystalline Diamond Films

摘要

The undoped polycrystalline diamond films are deposited on p-type silicon substrates by a microwave plasma chemical vapor deposition (MPCVD) system. The deposition conditions are CH_4/H_2=0.5percent, pressure = 45 torr, power = 2.2 kW, and subtract temperature = 885 deg C. SEM was used to inspect the surface morphology, Raman Spectrosopy to determine the quality, and XPS to analyze the chemical composition. It is concluded that a cleaning procedure on diamond surfaces can eliminate the carbon phase but enhance the oxygenation on the films. The electrical characteristics were investigated by current-voltage-temperature measurements in a metal-insulator-semiconductor (MIS) structure with top metal contacts and back silicon substrates contacts. It can be found a transition electric field of 240 kV/cm, where Schottky emission (SE) mechanism is responsible for electric conductio below 240 kV/cm, and Poole-Frenkel transport (PF) mechanism dominates beyond 240 kV/cm. By the extrapolations, the Schottky barrier height of silver and diamond film is 2.4 eV, and the tarp depth is 4.75 eV in the diamond film.