Epitaxial integration of ferroelectric and conductive perovskites on silicon

BaTiO3 (BTO) and LaxSr1 - xTiO3 (x <= 0.15) perovskite heterostructures are deposited epitaxially on SrTiO3 (STO)-buffered Si(001) via atomic layer deposition (ALD) to explore the formation of a quantum metal layer between a ferroelectric film and silicon. X-ray diffraction and scanning transmission electron microscopy show the crystallinity of the heterostructure deposited by ALD. After postdeposition annealing of the La-doped STO film in ultrahigh vacuum at 600 degrees C for 5 min, x-ray photoelectron spectra show the lack of La-dopant activation when the film is deposited on 10 nm-thick BTO. The same postdeposition annealing condition activates the La-dopant when LaxSr1 - xTiO3 films are deposited on STO-buffered Si(001) surfaces consisting of 2.8 nm of STO(001) on Si(001). Annealing of LaxSr1 - xTiO3 films sandwiched between BTO and STO-buffered Si(001) layers in air at temperatures <= 350 degrees C preserves the La-dopant activation. Piezoresponse force microscopy demonstrates the ferroelectric behavior of BTO films grown on LaxSr1 - xTiO3 surfaces. Sheet resistance and capacitance-voltage measurements further demonstrate the conductivity of the LaxSr1 - xTiO3 films sandwiched between the BTO film and the Si(001) substrate.