Crystalline and electrical properties of pulsed laser deposited BST on platinized silicon substrates

In order to produce thin film capacitors with elevated capacitance and breakdown strength, pulsed laser deposition of the ferroelectric material Ba0.6Sr0.4TiO3 (BST) has been trade on (111)Pt/Ti/SiO2/Si substrates. The films are in situ crystallized at 700 degreesC, polycrystalline in nature, and exhibit a single perovskite phase. This paper reports on both the effect of the oxygen pressure during heating and deposition, and the influence of different modes of introduction during the deposition stage, on the crystalline and electrical properties of the BST films. Orientation of films depends on the deposition oxygen pressure. with a (111) preferential orientation obtained when depositing under vacuum. XRD characterization reveals that the out-of-plane parameter of BST films increases when depositions are made tinder lower oxygen pressure. This phenomenon is related to a higher concentration of vacancies and defects in the films grown under low-pressure environment. However, a local introduction of oxygen on the substrate improves the annihilation of these defects. The crystalline orientation of the films is also highly dependent on the residual oxygen pressure during heating. A high (111) preferentially oriented BST film is obtained when heating and depositing tinder 0.1 mbar oxygen pressure. The heating atmosphere is thought to influence the out-diffusion of titanium on the surface of the Pt layer, thus modifying the nucleation and growth of BST films. Aluminum electrodes have been deposited on top of the BST films by do sputtering to measure electrical capacitances. The calculated dielectric constant of in situ crystallized films deposited under 0.1 mbar oxygen pressure exceeds 500 at 100 kHz under zero do bias. This high dielectric constant value obtained without post-deposition treatment appears to be of great technological interest. (C) 2002 Elsevier Science Ltd. All rights reserved.