X-ray photoemission studies of praseodymiumthin films on SiO2/Si(100)

Abstract

Pr overlayers, with thicknesses of about 1.8 and 0.6 nm,were deposited on 1.2 nm SiO2/Si(100)at room temperature and x-ray photoelectron spectroscopy (XPS) was used toinvestigate the reactions at the Pr/SiO2/Si interfacesas a function of annealing temperature. The results show that the Pr overlayers reduce SiO2at room temperature, forming Pr2O3and a Pr silicate (Pr–O–Si).For the 1.8 nm Pr/SiO2/Si system, the 1.2nm SiO2layer is mostly reduced at room temperature and a Pr silicide was alsoobserved. The Pr–O–Si silicate increases in intensity while the Pr2O3intensity decreases with annealing temperature. Angle-dependent XPS,taken after annealing, indicates that the silicate is located at the topsurface. In the case of the 0.6 nm Pr/SiO2/Sisystem, the Pr overlayer is almost oxidized after annealing, and some SiO2remains even after annealing at 1090 K, which can serve asa low-defect-density buffer layer between the high-κ film (Pr2O3and Pr–O–Si) and the silicon.