열 화학 기상법으로 증착된 SnO₂ 박막의 구조, 광학 및 전기적 특성

Abstract

Abnormal grain growth (AGG) occurs when SnO₂ thin films are deposited by conventional thermal CVD at 475 ℃, and high-resolution transmission electron microscopy shows some of the interfaces to be atomically faceted. However, when deposited at 525 ℃ normal grain growth (NGG) occurs with all the interfaces smoothly curved and atomically rough. This correlation between interface structure and grain growth behavior is consistent with that observed previously in bulk materials. For the application of SnO₂ thin films in sensors and transparent electrodes, the temperature of 525 ℃, which is just above the faceting transition temperature, was found to be optimum deposition temperature due to its small grain size and high surface to volume ratio. The photoluminescence properties of SnO₂ were investigated with different substrate temperatures. X-ray diffraction showed that the crystallinity of the grown thin films increased with increasing substrate temperatures. Two narrow peaks and two broad peaks were observed from the photoluminescence measurements at 6 K. The intensity and shape of the broad peaks changed with increasing substrate temperature. It is concluded that the origin of the broad peak at 2.4 eV was due to oxygen vacancies and that of peak at 3.1 eV was related to structural defects. Hall effect measurements showed that the carrier density was decreased as increasing deposition time from 10 to 30 min., but increased for the deposition of 60 min