| AVS 59th Annual International Symposium and Exhibition | |
| Electron Transport at the Nanoscale Focus Topic | Thursday Sessions |
| Session ET+NS+EM-ThM |
| Session: | Electron Transport at the Nanoscale: Nanowires and Junctions |
| Presenter: | R. Timm, Lund University, Sweden |
| Authors: | R. Timm, Lund University, Sweden O. Persson, Lund University, Sweden M. Hjort, Lund University, Sweden M.T. Borgström, Lund University, Sweden L. Samuelson, Lund University, Sweden A. Mikkelsen, Lund University, Sweden |
| Correspondent: | Click to Email |
III-V semiconductor nanowires offer tremendous possibilities for device application in energy and information technology [1]. Due to their unique properties and extreme surface-to-volume ratio, it is both essential and challenging to investigate their atomic structure and to combine this information with electrical measurements on individual nanowires. Recently, we have managed to clean InAs nanowires from their native oxide and obtained first atomically resolved images of their side surfaces by using scanning tunneling microscopy (STM) [2]. Here, we present a systematic STM study covering various nanowire surface structures emerging from different III-V material systems and different crystal structures. By combining STM imaging with scanning tunneling spectroscopy (STS) measurements we simultaneously study the surface structure and local electronic properties across the interfaces of nanowire heterostructures like polytypic nanowires, p-n-junctions, and material heterostructures.
In order to go further in combining local structural and electronic characterization as well as transport measurements of nanowire devices, we have developed a new method to perform STM/S on individual nanowires in-situ under device operation: For this, specific heterostructure nanowires, distributed on a SiOx/Si substrate, are contacted with metal electrodes defined by electron beam lithography. Using a combined Atomic Force Microscopy (AFM) / STM setup, we can first locate an individual nanowire in AFM mode and then acquire STM images and STS spectra on the contacted nanowire. Thus, we obtain the LDOS spatially resolved along the nanowire, even while the nanowire is externally biased via the metal contacts, allowing simultaneous transport studies. We will show and discuss initial results for different heterostructure nanowire devices, demonstrating the large potential of this new method.
Finally, we can also use the STM to measure electron transport through individual upright standing nanowires still on their growth substrate: After imaging the nanowires from top by STM [3], a point contact between the STM tip and the Au particle on top of the nanowire can be established in ultrahigh vacuum, thereby overcoming the problems in contacting single nanowires known from conventional setups. A high accuracy and reproducibility of this method has been demonstrated for InP and InAs nanowires with different doping levels [4] as well as for Schottky barrier measurements on Au/GaAs nanowires.
[1] Y. Li et al., Mater. Today 9 (10), 18 (2006).
[2] E. Hilner et al., NanoLetters8, 3978 (2008).
[3] A. Fian et al., Nano Letters 10, 3893 (2010).
[4] R. Timm et al., submitted (2012).