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Seebeck effect of as-grown and micro-structured metallic (Zn,Al)O

: Homm, G.; Teubert, J.; Henning, T.; Klar, P.J.; Szyszka, B.


Physica status solidi. C 7 (2010), Nr.6, S.1602-1604
ISSN: 1610-1634
ISSN: 1610-1642
ISSN: 1862-6351
International Conference on II-VI Compounds <14, 2009>
Fraunhofer IST ()

We studied the Seebeck coefficient S of sputtered Zn0.98Al 0.02O samples with free carrier concentrations varying from 10 18 to 1021 cm-3. The temperature dependence of the Seebeck coefficient at low carrier concentrations exhibits typical semiconductor behavior (S < 0 and pronounced phonon drag below 80K) whereas the metallic as-grown Zn0.98Al0.02O shows a sign reversal of the Seebeck coefficient with decreasing temperature which is related to the not square-root-like density of states of this degenerately doped metallic material. Furthermore, metallic specimens were microstructured by photolithography and wet-chemical etching with a pattern based on a square grid with a unit cell consisting of a centered square-hole. The Seebeck coefficient changed systematically with decreasing size of the unit cell. The change of S is caused by a shift of the Fermi energy due to the creation of additional surface traps at the sidewalls of the micro holes.