Structural and electrical properties and current–voltage characteristics of nitrogen-doped diamond-like carbon films on Si substrates by plasma-enhanced chemical vapor deposition

Abstract

We have deposited nitrogen-doped diamond-like carbon (N-DLC) films by plasma-enhanced chemical vapor deposition using CH4, N2, and Ar, and investigated the effects of N doping on the structure and the electrical, mechanical, and optical properties of the N-DLC films. We fabricated undoped DLC/p-type Si and N-DLC/p-type Si heterojunctions and examined the current–voltage characteristics of the heterojunctions. When the N2 flow ratio was increased from 0 to 3.64%, the resistivity markedly decreased from the order of 105 Ω·cm to that of 10−2 Ω·cm and the internal stress also decreased. The resistivity gradually increased with increasing N2 flow ratio from 3.64 to 13.6%, and then it decreased at a N2 flow ratio of 13.6%. These behaviors can be explained in terms of the clustering of sp2 carbons and the formation of sp3C–N, sp2C=N, sp1C≡N, and C–Hn bonds. The rectification ratio of the heterojunction using the N-DLC film prepared at 3.64% was 35.8 at ±0.5 V.