Microstructural Evolution in Mocvd-Derived Tantalum-Doped Tin Dioxide Thin Films and Subsequent Property Changes

Abstract

In this study, a series of Ta-doped SnO2 thin films was grown on glass and A12O3(0001) substrates utilizing the metal-organic chemical vapor deposition (MOCVD) technique. The main focus of this study was to understand the structure-property relationship in the Ta-Sn-O material system. Microstructure of the films was characterized through x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Electrical properties were studied using four-point probe resistivity and Hall measurement. Optical transparency was also measured in the visible spectrum. The major contribution of this study includes: (1) By introducing Ta during the growth of SnO2 thin films highly conductive and transparent films were prepared. The effectiveness of Ta as an n-type dopant in SnO2 was investigated by studying electrical properties of the thin films. (2) A unique variant structure of undoped and Ta-doped epitaxial SnO2 thin films grown on A12O3(0001) substrates was studied. Crystallographic models were proposed to explain the variant structure. The role of Ta on the variant structure and the subsequent electrical property were also investigated.