Structural and chemical stability of thin films of Pt-Ga intermetallic compounds of GaAs (001)

Nearly single-phase thin films of three different Pt-Ga intermetallic compounds have been grown on GaAs(001) by co-deposition of Pt and Ga. The resultant films have been annealed at various temperatures and then characterized using x-ray two-theta diffractometry (XRD), Auger electron spectroscopy (AES), and x-ray photoemission spectroscopy (XPS). The XRD results showed that PtGa₂ and PtGa thin films are chemically stable on GaAs under one atmosphere of N₂ up to 800 °C and 600 °C, respectively, but thin films of Pt₂Ga react with GaAs at temperatures as low as 200 °C to form phases with higher Ga concentration PtAs₂. The XRD patterns also revealed that the crystallite orientation and texture of the films were dependent on annealing temperature. Segregation of Ga to the surfaces of the films upon annealing was also observed by both AES and XPS. The results demonstrated that the as-deposited films of PtGa₂ and PtGa were kinetically stabilized with respect to possible chemical reactions with the GaAs substrates that evolve gaseous As species during open system annealing.