1 research outputs found
Thermoelectric Power Factor Enhancement by Pulsed Plasma Engineering in Magnetron Sputtering Induced Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> Thin Films
Precise
control over microstructure and composition is desired prerequisite
for the performance enhancement of thermoelectric materials. In conventional
magnetron plasma sputtering synthesis, composition control is challenging
when the sputtering-target is composed by different elements. Here,
the potential of pulsed power utilization is demonstrated for compositional
control of Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> thin films via
pulse-reversal time and pulse-frequency engineering in pulsed DC-magnetron
sputtering process. When annealed at 400 °C for 1 h in vacuum
conditions, amorphous thin films (of 200 nm thickness, deposited on
glass substrate) crystallize in to face centered cubic phase with
average nanocrystallite size ∼10 nm. Power density enhancement
to 5.56 W/cm<sup>2</sup> at low pulse reversal time induces maximum
process throughput as 450 nm/min. Increase in either of pulse frequency
or pulse reversal time decreases the discharge voltage and plasma
density. As a consequence, kinetic energy of ions and ionization of
plasma species are sequentially controlled to improve the stoichiometry
of film and eventually; the electronic transport. The optimization
of pulse plasma engineering yields maximum thermoelectric power factor
value as 1.35 μW cm<sup>–1</sup> K<sup>–2</sup> with process throughput more than 300 nm/min. The obtained values
are promising for applications in the automobile and microelectronics
industry