Effects of Zn and Zn-N doping on optical, electrical, and structural properties of p-type SnO2 films

Zn-doped SnO2 (ZTO) and Zn-N co-doped SnO2 (ZNTO) films were deposited via direct current sputtering. Herein, the Zn-substituted Sn (ZnSn) and N-substituted O (NO) contents were determined using EDX mapping and XPS analysis. The crystal qualities of the ZTO and ZNTO films were determined using X-ray diffraction, field emission scanning electron microscopy, and atomic force microscopy; the ZTO films exhibited a low crystal quality. On the other hand, the crystal quality of the ZNTO films improved significantly because of the contribution of NO in the SnO2 lattice. Additionally, the rutile (101) - cubic (200) reflection transition proved the presence of NO in the host lattice due to its increased compressibility. The transmittance of the ZNTO film was over 85% in response to the standard of a transparent conductive electrode. Excellent p-type properties were confirmed for the ZNTO film deposited from SnO2 target doping 8 wt% ZnO, with the lowest resistivity of 6.3 x 10-3 omega cm and the highest hole mobility of 7.66 cm2 V-1 s-1. The photocurrent characteristics of the ZNTO/n-Si junctions indicated that the films could be applied as p-type transparent conductive electrodes in transparent electronic or optoelectronic devices.