| AVS 59th Annual International Symposium and Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS+NS-ThA |
| Session: | Surface Science of Nanostructures |
| Presenter: | A. Mikkelsen, Lund University, Sweden |
| Correspondent: | Click to Email |
Free-standing III-V nanowires have the potential to become central components in future electronics and photonics with applications in IT, life-science and energy[1]. The atomic scale structure and morphology of semiconductor nanowire surfaces are central in determining both growth and function of the wires. Surface diffusion and nucleation will directly influence the final appearance of the wires, and transport and optical properties of semiconductor nanowires is often governed by their surfaces.
We develop and use scanning probe and synchrotron based microscopy/spectroscopy to completely determine structure, chemistry and physical properties of III-V nanowire surfaces with extreme precision. We use our novel methods to directly image both interior and exterior surfaces of the nanowires down to the single atom level, revealing geometric structure as well as both electrical and mechanical properties[2-4]. With our rather diverse toolbox we can obtain a real understanding of the connections between nanowire structure, growth and function.
We present recent Scanning Tunneling Microscopy/spectroscopy (STM/S) results, on nanowires consisting of various III-V materials and of polytypic heterostructures with wurtzite (WZ) and zincblende (ZB) crystal segments - only possible in nanowires. We have obtained images of the atomic scale structure for all common WZ and ZB facets as well as information about the electronic structure using STS. We are now developing these methods to perform STM/S on individual nanowires under device operation. Further, we show that STM, can be used for direct top view imaging of the micrometer high free-standing nanowires. We then determine mechanical resonances up to hundreds of MHz with sub Ångström precision[4].
Finally, using synchrotron based Photo Emission / Low Energy Electron Microscopy/Spectroscopy (PEEM/LEEM/XPS) we have characterized III-V nanowire surface chemistry and electronic properties and investigated the influence of various ultra-thin dielectrics to reduce surface band-bending effects[5-8]. A complete picture of oxide thicknesses, effects on bandbending and information on axial and radial doping is obtained.
1. C.M. Lieber and Z.L. Wang, MRS Bull.32, 99 (2007), and other papers in this issue.
2. A. Mikkelsen et al, Nature Mater.3, 519 (2004) ; L. Ouattara et al, Nano Lett.7, 2859 (2007)
3. E. Hilner, et al, Nano Lett, 8, 3978 (2008)
4. A. Fian, et al, Nano Lett. 10, 3893 (2010)
5. R. Timm et al., Appl. Phys. Lett.99, 222907 (2011).
6. B. Mandl et al., Nano Lett. 10, 4443 (2012)
7. R. Timm el al., Microelectron. Eng. 88, 1091 (2011).
8. M. Hjort et al, Appl. Phys. Lett.99, 233113 (2011)