Authors: A. Schilling, MM. Saad, P. Baxter, TB. Adams, RM. Bowman, JM. Gregg, FD. Morisson and JF. Scott
Affilation: Queen's University, Belfast & Nanotec NI, United Kingdom
Pages: 317 - 320
Keywords: ferroelectric, barium titanate, dielectric constant
Measurements on free standing single crystal barium strontium titanate capacitors made using focused ion beam micromachining with thicknesses down to 75 nm, show a dielectric response typical of large single crystals, rather than conventional thin films. There is a notable absence of any broadening or temperature shift of the dielectric peak or loss tangent; peak dielectric constant of ~25, 000 are obtained and Curie-Weiss analysis demonstrates 1st order transformation behaviour (Figure 1). This is in major contrast to results on conventionally deposited thin film capacitor structures which show large dielectric peak broadening and temperature shifts, as well as apparent change in nature of the paraelectric-ferroelectric transition from 1st to 2nd order. The data are compatible with recent models models, which attribute dielectric peak broadening to gradient terms that will exist in any thin film capacitor heterostructure, either through defect profiles introduced during growth, or through subtle asymmetry between top and bottom electrodes. These results and implications for data used to derive likely performance parameters in future down-scaling of FRAM devices into the nanoscale will be discussed.