Augmentation of thermoelectric power factor of p-type chromium nitride thin films for device applications

Abstract

The transformation of the n-type chromium nitride (CrN) thin films into p-type by intrinsic point defects using reactive radio frequency magnetron sputtering is explored in this report. The formation of the acceptor point defects with increasing nitrogen pressure transformed the n-type conductivity of CrN into p-type along with variation of preferred orientation from (111) to (200). To improve the mobility of holes and hence to decrease the resistivity, the CrN thin films with preferred orientation along (220) was fabricated by precisely tuning the sputtering parameters. The root cause behind the reduction in resistivity of CrN thin films with orientation of crystallites was explored by surface charge density mapping using conductive atomic force microscopy. The reduction in resistivity resulted in the enhancement of thermoelectric power factor and the p-type CrN thin film showed a power factor of 24.43 μW/m K2 with Seebeck coefficient of 301 μV/K and resistivity of 3.71 mΩ m at RT.