Structural and thermoelectric transport properties of Sb2Te3 thin films grown by molecular beam epitaxy

We have studied the structural and transport properties of Sb2Te3 thin films prepared by molecular beam epitaxy as a function of the Te/Sb flux ratio during deposition. Both the crystallinity and the transport properties are found to be strongly affected by nonstoichiometry. The most stoichiometric sample (prepared with a Te/Sb ratio of 3.6) had a high degree of crystallinity, high thermopower, and high carrier mobility. However, Sb2Te3 films with excess Sb or Te had poorer crystallinity, reduced magnitude of the thermopower, and reduced mobility as a result of the formation of antisite defects. These antisite defects were able to be reduced by controlling the relative flow rate ratio of Te to Sb during growth.