MOCVD Growth of Thermoelectric BiSbTe3 Films on Surface-Treated Sapphire Substrates

Metal organic chemical vapor deposition(MOCVD) has been used to grow BiSbTe3 films on (0001) sapphire substrates. Prior to growth, some of the substrates were subjected to chemical treatment. The impact of this process on the surface morphology and on the crystalline quality of the resulting BiSbTe3 films is investigated. We demonstrated that the surface treatment of a sapphire substrates with a potassium-containing solution has a marked effect on the surface morphology of the resulting layers. In particular, BiSbTe3 layers grown on sapphire substrates treated with a potassium-containing solution exhibited a high nucleation density during the initial growth stage, leading to a smooth mirror-like morphology. In contrast, the growth of films oil sapphire substrates without treatment was found to result in randomsized island-like surface defects Untreated substrates led to multi-oriented films while films on treated substrates were close to epitaxially oriented. We believe that the formation of nanoscale defects on the substrate surface during chemical treatment may account for the observed improved surface morphology.