|AVS 58th Annual International Symposium and Exhibition|
|Nanometer-scale Science and Technology Division||Tuesday Sessions|
|Session:||Nanowires and Nanoparticles II: Characterization and Synthesis|
|Presenter:||O. Persson, Lund University, Sweden|
|Authors:||O. Persson, Lund University, Sweden
D. Suyatin, Lund University, Sweden
J. Wallentin, Lund University, Sweden
L. Samuelson, Lund University, Sweden
A. Mikkelsen, Lund University, Sweden
R. Timm, Lund University, Sweden
|Correspondent:||Click to Email|
Semiconductor nanowires show great characteristics for implementations in a broad range of applications, e.g. optoelectronic devices . The increased possibilities of using different materials to realize tailored p-n-junctions or bandgaps and the inherent property of low density of defects make the nanowire the perfect candidate to realize new electronic devices.
Vast arrays of freestanding nanowires are used in many applications such as LEDs and solar cells. The electronic properties of such wires are essential to investigate for understanding and further developing the devices. The prevalent method used to make electronic measurements on nanowires is complex and challenging. It consists of several processing steps where the nanowire has to be deposited onto a substrate, localized, and then contacts need to be defined and deposited . The range of nanowire material systems and doping levels for which this method can provide good Ohmic contacts is strongly limited.
Here we show a novel technique for investigating the electronic properties of freestanding nanowires by utilizing a scanning tunneling microscope (STM). We can exactly obtain the position of individual freestanding nanowires by scanning them from the top . By contacting the Au-seed particle on the top of the nanowire with the STM tip in a controlled manner, a well-defined point contact is established. The sample substrate will act as a back contact establishing a well-defined system in an ultra-high vacuum.
We have previously performed a variety of successful STM measurements on III-V nanowires [3,4]. Here we show that I-V measurements on single as-grown wires can be done reproducibly and consistently. GaAs wires with a doping concentration of 1018 cm-3 and a diameter of 80 nm are analyzed with this method and they consistently show a resistivity of approx. 700 Ω. Measurements on InP and InAs wires confirm the reliability of this new technique by revealing nanowire conductivities which agree well to the corresponding doping level. We will also present first results on individual nanowire p-n-junctions and Schottky diodes.
The main advantages of our method are that we get a well-defined contact, the measurements are done on as-grown nanowires, and we have a good control of the wire surfaces due to UHV conditions. To determine the chemical surface composition of these wires, the I-V studies are complemented by high intensity X-ray photoemission spectroscopy at the MAX-II synchrotron in Lund.
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