报告题目：Epitaxial growth of heterostructuredIII-V semiconductor nanowires on graphene

报 告 人：Prof. Helge Weman（Norwegian University of Science and Technology, CrayoNanoAS, Norway）

报告时间：2017年04月19日（星期三） 上午10:00-11:00

报告地点：新校区物理与电子学院多功能报告厅（116室）

报告摘要：

Heterostructured III-V semiconductor nanowires have attracted considerable attention in recent years because of their potential in future nano-electronic and nano-photonic device applications. The III-V nanowire project at NTNU today involves the epitaxial growth (MBE), structural (HRTEM) and nano-optoelectrical characterization, as well as processing (NTNU NanoLab) with a special emphasis on nanowire solar cell devices. In this talk, I will give some highlights on what we have achieved since 2006 when the first GaAs nanowires were grown at NTNU.

I will then focus on our most recent work on epitaxial growth of GaAs nanowires on graphene [1-2]. We have recently developed a generic atomic model, which describes the epitaxial growth of semiconductor nanostructures on graphene that is applicable to all conventional semiconductor materials. The model was first verified by cross-sectional transmission electron microscopy studies of GaAs nanowires that grow epitaxially and dislocation-free on graphene. Recently we have also shown the vertical growth of dislocation-free GaN nanowires on graphene [3]. The epitaxial growth of semiconductor nanostructures on graphene is very appealing for device applications since graphene can function not only as a replacement of the semiconductor substrate but in addition as a transparent and flexible electrode for e.g. solar cells and LEDs.

For deep ultraviolet AlGaN based LEDs in huge need for various disinfection and sterilization purposes, the concept offers a real advantage over present thin film based technology. Such thin film UV LEDs are today very expensive and inefficient due to the lack of a good transparent electrode (ITO is absorbing in deep UV), the high dislocation density in the active thin film layers, low light extraction efficiency, and the use of very expensive semiconductor substrates (e.g. AlN). The spin-off company CrayoNano are now developing UV LEDs based on the growth of AlGaN nanostructures on graphene, which potentially can overcome these problems, as will be further discussed in my talk.

References

A.M. Munshi, D.L. Dheeraj, V.T. Fauske, D.C. Kim, A.T.J. van Helvoort, B.O. Fimland, and H. Weman, Nano Letters12, 4570 (2012).

2. A.M. Munshi and H. Weman, Phys. Status Solidi RRL7, 713 (2013). (Review)

3. M. Heilmann, A.M. Munshi, G. Sarau, M. Göbelt, C. Tessarek, V.T. Fauske, A.T.J. van Helvoort, J. Yang, M. Latzel, B. Hoffmann, G. Conibeer, H. Weman, and S. Christiansen,

Nano Letters16, 3524 (2016).

报告人简介：

(NTNU) in Trondheim, Norway. He received his PhD in semiconductor physics in 1988 from Linköping University, Sweden. During his career, he has held various positions at UCSB, NTT, EPFL and IBM Res. Lab Zurich. Since 2005 Weman is leading a research group at NTNU on III-V semiconductor nanowires grown on Si and graphene for use in optoelectronic applications. In June 2012 he founded CrayoNano AS who are now developing highly efficient deep UV LEDs using AlGaN nanostructures grown on graphene. He is the coordinator of the M-era.Net project “Semiconductor Nanowire/Graphene Hybrids for High-Efficiency LEDs” consisting of academic and industrial partners from Norway and South Korea. At CrayoNano he is also partner of the EUROSTAR project “CMOS Fab-compatible Graphene”. Germany. Since 2010 Dr. Weman is a member of the Norwegian Academy of Technical Sciences (NTVA).