Structure of Ge-based films exhibiting thermoelectric effect

This paper concerns the growth of Ge thin films doped with various dopants (B, Sb, Au) by magnetron sputtering in Ar plasma under constant or pulsed p owering. The aim of this work was to correlate the structural properties of Gc films with their capability to generate thermoelectric power. The films were prepared at varying sputtering deposition parameters (i.e. supplying power and substrate temperature). For the deposition at low temperatures (6 23 K) and with the addition of boron or antimony to target surface, the fil ms tend to grow in microcrystalline or amorphous structure. The amorphous a s-sputtered films convert into polycrystalline ones during thermal treatmen t in vacuum at the temperature above 723 K. However, when Ge and Au are co- sputtered, the polycrystalline films contaminating crystallites of both Ge and Au phases are formed regardless of the substrate temperature during dep osition (406-1040 K). For various films the efficiency of thermoelectric po wer in the range of 2.10(-10) to 6.10(-6) W.K-2 cm(-1) was obtained. The re sults presented here suggest that both the grain size of Ge phase and dopan t activation are dominant factors in determining the efficiency of thermoel ectric power. From our experiments, the proper deposition conditions or ann ealing for maximizing the efficiency value can be obtained. For Ge-Au and G o-Sb films these values were comparable to that of poly - Si.