Effect of carbon doping on microstructure, electronic and magnetic properties of Cr:AlN films

Carbon was doped into Cr:AlN films. Microstructure analysis demonstrated that the Cr atom kept at AlN lattice when carbon content was lower. The doped carbon atoms formed graphite phases and C-N clusters dispersing in the films, which influenced the electric and magnetic properties significantly. When the resistivity was around 10(5)-10(7) Omega cm under an alternating current (AC) frequency of 210 Hz, it increased with increasing carbon content, and when the resistivity was around 10(3) Omega cm under a higher AC frequency of 800 kHz, it decreased with increasing carbon content. The magnetisms for the carbon-doped samples are stronger than those of samples without carbon doping. The atomic magnetic moment (AMM) of the sample with a carbon content of 2.3 at.% was the highest (0.4 mu(B)/Cr). It was proposed that atomic migration of carbon might have occurred under high AC frequency. The formation of C-N compounds could consume part of the available nitrogen and then increased the density of N vacancy in the Cr:AlN lattice, which is favorable for coupling among bound magnetic polarons (BMP). (C) 2010 Elsevier B.V. All rights reserved.