■ 제 목: Unconventional epitaxy and van der Waals stack integration for fabricating multi-functional devices

■ 연 사:  홍영준 교수 (세종대학교 나노신소재공학과)                  

■  일 시:  2023년 4월 11(화) 오후 4시 

■  장 소:  응용공학동 1층 영상강의실 

■ Host :  배병수 교수 

Epitaxy provides a way to prepare single-crystalline overlayer devices on wafers made of different materials. This technique has played a crucial role in the commercialization of high-performance quantum-functional electronic and optoelectronic devices. With the growing demand for high-performance multi-functional devices on a single chip, the electronics industry has shifted towards high-density hetero-integration. This has led to the development of stamping-printing and transfer-assembly techniques. One approach for heterogeneous integration involves transfer-based assembly methods, which require the delamination of epi-layers prepared from different batches and procedures. However, two important technical issues arise in this process. First, conventional epitaxial growth methods result in epi-layer devices that are strongly bonded to the substrate, making them difficult to separate without the use of high-power laser irradiation or chemical etchants. It is well known that these separation methods leave damage to the substrate and epi-layers. The strict constraints of these methods limit the degree of freedom in using conventional wafers. Second, during the transfer and assembly process, different functional devices need to be diced into tiny chips and then transferred and assembled onto the desired substrate with highly accurate alignment precision. However, achieving vertical stack devices in high density is challenging due to transfer accuracy issues. In this colloquium, we discuss a novel epitaxy technique that does not require chemical bonds between the epi-layer and wafer, which can help resolve these issues. We also share the procedures for making high-density heterogeneous and flexible devices using this novel epitaxy approach, towards applications such as micro-displays and flexible optoelectronic devices.