| 학회 | 한국재료학회 |
| 학술대회 | 2018년 봄 (05/16 ~ 05/18, 삼척 쏠비치 호텔&리조트) |
| 권호 | 24권 1호 |
| 발표분야 | 5. 화학센서용 기능성 소재(Chemical sensors)-오거나이저: 장호원 교수(서울대) |
| 제목 | Gas sensing behaviors in metal-oxides-based nanoscale Schottky and hetero p-n junctions |
| 초록 | Metal oxides gas sensors have been intensively studied due to their advantages of low cost, and simple fabrication and operation. However, there are several issues to be solved such as high-temperature operation, and low gas selectivity. In this regard, metal oxides-based nanoscale heterojunctions have recently become attractive candidates as sensing layers, most of which are based on mixed composite or particle-decorated structures having randomly distributed heterojunctions. Although gas sensing performances were reported to be enhanced, there have been remaining challenges in understanding gas sensing behaviors at the hetero-interfaces with such not-well defined heterojunctions. In this presentation, gas sensing behaviors in the metal oxides-based nanoscale heterojunctions are studied, and the way to enhance gas sensing performances are introduced. The key idea is to fabricate and characterize the nanoscale Schottky diodes and hetero p-n junction diodes having well-defined and highly-exposed metal oxides-based hetero-interfaces. The device is designed to have top-and-bottom electrodes configuration and sensing layers between them, enabling effective current modulation through well-defined heterojunctions. Furthermore, hetero-interfaces are highly exposed in nanoscale to gas ambient which facilitates gas adsorption and desorption on metal oxides-based heterojunctions. First, a nanoscale Pt/n-TiO2 and p-NiO/TiAu Schottky diodes are fabricated and characterized to study gas sensing behaviors in the metal and metal oxides heterojunctions. It shows very promising low-temperature performance including a high H2 response and short response/recovery times. Such a high performance is attributed to a unique device architecture having highly exposed nanoscale Schottky contact to the ambient and the top-and-bottom electrodes configuration, which takes full advantages offered by the Schottky devices. Second, a nanoscale p-NiO/n-SnO2 diode is fabricated and characterized to study gas sensing behaviors in nanoscale hetero p-n junctions. Here, the heterojunctions are well-defined and gases can easily access to both metal oxides surfaces and hetero-interfaces. The p-NiO/n-SnO2 gas sensor shows a similar trend in current modulation under both reducing H2 and oxidizing NO2 gases, which is very unusual considering the changes of electrical properties occurring in the single p-NiO and the n-SnO2 gas sensors. Such unexpected sensing properties are explained by the predominant modulation in barrier height at the hetero-interfaces over the change in the carrier concentration of each oxide layer, which is confirmed by the Shockley diode equation as well as the simulation results obtained by TCAD software. |
| 저자 | 권현아, 김종규 |
| 소속 | 포항공과대 |
| 키워드 | Metal oxides; heterojunction; gas sensor |
