Influences of interfacial intrinsic low-dielectric layers on the dielectric properties of sputtered (Ba,Sr)TiO3 thin films

The influences of low-dielectric interfacial layers on the dielectric properties of Pt/(Ba,Sr)TiO3/Pt capacitors were investigated before and after postannealing. The interfacial layer is believed to be the intrinsic dead layer (low-dielectric layer) due to the termination of chemical bonds of the (Ba,Sr)TiO3 (BST) material at the interfaces. The dielectric constant of the capacitor decreases with decreasing BST film thickness owing to the low dielectric constant of the dead layer. The dead-layer capacitance varies with processes such as film deposition temperature, and postannealing. Higher deposition temperatures result in a larger dead-layer capacitance and a higher bulk dielectric constant. Although annealing under a N-2 atmosphere is less effective in reducing the dead-layer effect than under an O-2 atmosphere, it is more effective in increasing the bulk dielectric constant. Therefore, a N-2, rather than an O-2 atmosphere, results in a larger increase in the overall dielectric constant. (C) 2000 American Institute of Physics. [S0003-6951(00)00427-7].