S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Material Science and Engineering (재료공학부) Theses (Master's Degree_재료공학부)
The fabrication and performance analysis of vanadium oxide thin films for microbolometer application
마이크로볼로미터 적용을 위한 바나듐 산화물 박막의 제작 및 성능 분석
- 공과대학 재료공학부
- Issue Date
- 서울대학교 대학원
- 학위논문 (석사)-- 서울대학교 대학원 : 공과대학 재료공학부, 2018. 8. 박찬.
- Research on infrared sensing technology that can detect objects at night can be applied to a variety of fields such as autonomous vehicles, medical devices. There are two kinds of infrared sensor, photon detector and a thermal detector. The photon sensing type detector has relatively high detection performance. However, it is expensive and has low mobility because it requires cryogenic cooling equipment that has a large volume. On the other hand, the thermal sensing type detector has relatively low performance, but it is cheaper and has high mobility than photon detection type device. There are many kinds of thermal sensing type detector, however, microbolometers with high detectivity are attracting attention, and many new materials are being studied to use for the thermal sensing layer of microbolometer. The most important part of the microbolometer is a thermal sensing layer that absorbs the heat and various materials have been studied as a candidate for thermal sensing material. In general, vanadium oxide and amorphous silicon (a-Si) are being researched as a thermal sensing material.
Vanadium oxide has many advantages over a-Si as a microbolometer material. Therefore, IR cameras using vanadium oxide thin film are being commercially used in many fields. However, although vanadium oxide has been extensively studied, still there are problems such as the stability or operating temperature range of the microbolometer device. Vanadium oxide has various polymorphic phases, which makes it difficult to fabricate the desired phase thin film with high reproducibility. Moreover, the operating temperature range of thin film containing monoclinic VO2 (VO2(M)) phase is limited due to the phase transition at 68 ℃.
In this study, we fabricated vanadium oxide thin film for microbolometer which is stable at a high operating temperature and shows high-performance. Thin films containing VO2(M) phase have limited operating temperature range due to the hysteretic behavior induced by the phase transition. Therefore, single phase VO2(B) thin film without VO2(M) was fabricated by sputtering. We have found that the perovskite buffer layer is effective for the production of single phase VO2(B) thin films and produced stable single phase VO2(B) thin films using various perovskite buffers. We also analyzed the electrical properties of VO2(B) thin films, verifying that buffered VO2(B) thin film has high TCR & low resistivity simultaneously. Moreover, depending on the type of the buffer layers, the phase of the vanadium oxide and the electrical properties of the thin film could be controlled.