The growth kinetics of rf sputtered Ba2Si2TiO8 thin films

Abstract

Radio-frequency sputtered barium titanium silicate (BST), Ba2Si2TiO8, thin films were grown on crystalline Si(100) substrates at substrate temperatures ranging from 750 to 955 °C and were characterized using x-ray diffraction, optical microscopy, and scanning electron microscopy. The result of x-ray diffraction analysis indicates that the BST films deposited at an optimum substrate temperature of 845 °C were strongly c-axis oriented. The corresponding film growth rate in the direction normal to the film surface and lateral grain growth rate were 1.95 nm/min and 0.77 μm/min, respectively, at the initial stage of deposition. The former decreased with sputtering time and the latter increased with grain size. The fast lateral grain growth rate indicates a strong interaction between the overgrown BST film and the Si substrate. The increase in lateral grain growth rate suggests a surface diffusion controlled nucleation and growth mechanism in the initial stage of the deposition, and a coalescence mechanism dominating in the later stage. The activation energy for lateral grain growth was 359±30 kJ/mol for 0.01 μm size grains, and decreased to 148±20 kJ/mol for 1 μm size grains, which is in good agreement with the proposed growth model.