Transport and optical properties of amorphous carbon and hydrogenated amorphous carbon films |
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Authors: | A. Tibrewala E. Peiner S. Biehl |
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Affiliation: | a Institute for Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig, Germany b Fraunhofer-Institute for Thin Film and Surface Engineering, Bienroder Weg 54 E, D-38108 Braunschweig, Germany |
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Abstract: | In this paper we report on the electrical and optical properties of amorphous carbon (a-C) and hydrogenated amorphous carbon (a-C:H) films. Resistivity of both types of films decreases with increase in temperature. At lower temperatures (60-250 K) the electron transport is due to variable range hopping for the a-C films. At higher temperatures (300-430 K) it is thermally activated for both types of films. Analysis of the heterojunction between diamond-like carbon (DLC) and bulk silicon (Si) leads to the conclusion that our a-C films are of n-type and our a-C:H films are of p-type. The optical measurements with DLC revealed a Tauc bandgap of 0.6 eV for the a-C films and 1-1.2 eV for the a-C:H films. An Urbach energy around 170 meV could be determined for the a-C:H films. Strain versus resistance plots were measured resulting in piezoresistive gauge factors around 50 for the a-C films and in between 100 and 1200 for the a-C:H films. |
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Keywords: | 72.20 73.40 42.25.B |
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