Crystallization of bismuth titanate and bismuth silicate grown as thin films by atomic layer deposition

Bismuth silicate and bismuth titanate thin films were deposited by atomic layer deposition (ALD). A novel approach with pulsing of two Bi-precursors was studied to control the Si/Bi atomic ratio in bismuth silicate thin films. The crystallization of compounds formed in the Bi2O3–SiO2 and Bi2O3–TiO2 systems was investigated. Control of the stoichiometry of Bi–Si–O thin films was studied when deposited on Si(100) and crystallization was studied for films on sapphire and MgO-, ZrO2- and YSZ-buffered Si(100). The Bi–Ti–O thin films were deposited on Si(100) substrate. Both Bi–Si–O and Bi–Ti–O thin films were amorphous after deposition. Highly a-axis oriented Bi2SiO5 thin films were obtained when the Bi–Si–O thin films deposited on MgO-buffered Si(100) were annealed at 800°C in nitrogen. The full-width half-maximum values for 200 peak were also studied. An excess of bismuth was found to improve the crystallization of Bi–Ti–O thin films and the best crystallinity was observed with Ti/Bi atomic ratio of 0.28 for films annealed at nitrogen at 1000°C. Roughness of the thin films as well as the concentration depth distribution were also examined.