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

Abstract

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

Ineffectiveness of energy filtering at grain boundaries for thermoelectric materials

“…Such a filtering effect is reported for indium gallium arsenide superlattice films, 10 bulk PbTe with Pb nanoparticles, 11 nanocrystalline PbTe, 12-14 nanostructured SiGe, 15 and ZnO-based materials. [16][17][18] An additional advantage that often comes along with such an energy-filtering mechanism is an additional phonon scattering, 10,12,13,19 which reduces the phonon part of the thermal conductivity and therefore can also increase the figure of merit. One drawback of the filtering effect is always a reduction of the electric conductivity.…”

Phonons investigation of ZnO@ZnS core‐shell nanostructures with active layer

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Calculation of Thermoelectric Transport Properties in Heterostructures

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