Nano-Scale Devices Embedded in Self-Supporting Polymer Foils
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NANO-SCALE DEVICES EMBEDDED IN SELF-SUPPORTING POLYMER FOILS R. Könenkamp1, J. Chen2 , S. Klaumuenzer2, and R. Engelhardt2 1 Physics Department, Portland State University, Portland, OR. 97201, USA 2 Hahn-Meitner Institut Berlin, Glienicker Strasse 100, 14109 Berlin, Germany ABSTRACT Self-supporting polymer foils of several micrometer thickness have been structured using irradiation by fast heavy ions and subsequent etching. Very deep, well defined nanostructures can be prepared in this way. These can then be used as templates for semiconductor deposition and the fabrication of robust embedded electronic devices. Electron microscopy shows voidfilling poly-crystalline growth in the polymer films. Electrical experiments show low sensitivity when mechanical forces are exerted on the foil, suggesting that the embedded nanodevices can be used as reliable sensors in applications with considerable bending of the foils. Two different transistor arrangements will be discussed. INTRODUCTION Semiconductor structuring in the nano- and micrometer range is of interest for a number applications and is currently pursued in many fields, particularly in electronics, photonics, sensing and in photovoltaics. There is also a basic interest in studies of electronic properties in confined volumes. In this paper we report the fabrication of columnar semiconductor devices grown within nanometer sized pore regions of self-supporting polymer foils. Well-defined semiconductor columns with diameters as low as 30 nm and aspect ratios well in excess of 100 can be in the etched ion tracks of polyester foils. We have deposited a quaternary, transparent p-type semiconductor, CuSCN, in the vertical etch cylinders of polyethylen-terephthalat (PET) foils. While similar approaches have previously been employed for the growth of metals as well as semiconductors (1-3), there are very few reports on device fabrication employing this approach. Electrodeposition is used as the preferred semiconductor growth process. It can be carried out at comparably low temperatures and leaves the polyester foil chemically and structurally intact. Both, the fabrication of the templates and the growth of the semiconductor columns are compatible large area applications. EXPERIMENTAL Narrow channels of circular cross-section and diameters varying between 30 nm to 300 mm were prepared in thin ~10 µm thick PET foils using 400 MeV heavy ion irradiation from the Ion Synchrotron Lab Berlin at the Hahn-Meitner Institut Berlin. The passage of these highly energetic ions induces amorphization of the polymer structure in a narrow cylinder of a few Å diameter (4). After irradiation the polymer foil is exposed to an aqueous solution of 10%
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Figure 1a: Polymer foil with ~ 100 nm diameter etch cylinders prepared by ion track etching. Figure 1b: Freestanding nanowires grown in electrodeposition in after dissolving the foil.
NaOH in H20 at 80°C. This treatment induces fast etching of the amorphized ion track and isotropic slow etching of the intact polyester structu
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