(001)-Oriented LaNiO 3 Bottom Electrodes and (001)-Textured Ferroelectric Thin Films on LaNiO 3
- PDF / 700,799 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 31 Downloads / 240 Views
Zhenshan Zhang, Jeong Hwan Park and Susan Trolier-McKinstry Materials Research Laboratoryand Departmentof MaterialsScience and Engineering, Pennsylvania State University, University Park, PA 16802
ABSTRACT In this work, highly (OO1)p•-oriented thin films of LaNiO 3 (LNO) were deposited by DC magnetron sputtering onto Si substrates (pc = pseudocubic indices). The target powder was prepared using a molten salt technique with Na 2CO 3 as a flux. The final target density was greater than 85% of theoretical density. The best results were obtained when sputtering was carried out at a power of 186 W and a working pressure of 45 mtorr with a gas composition of 50% 02 + 50% Ar. The thickness of the deposited films was proportional to the sputtering time, and the growth rate was 300A/hour. Highly (001)-oriented thin films of lead zirconate titanate Pb(Zro. 52Ti0.48)O 3 (PZT) and Pb[(Mg1/ 3Nb 2/3)0.7Ti0. 3]O 3 (PMN-PT) were fabricated by a sol-gel2 method on (001)-textured LNO metallic oxide electrodes. A remanent polarization of 12 ltC/cm and d 31 of -125 pC/N (assuming a Young's modulus of 35 GPa) were measured on the PMN-PT thin films with a thickness of 0.9 lgm. This piezoelectric coefficient considerably exceeds that available from PZT films, and depends critically on the film orientation. Changes in the hysteresis loop due to externally applied stress will also be described. INTRODUCTION Preparation of electrodes for ferroelectric thin films is important in the fabrication of ferroelectric memories, microsensors and microactuators. Generally, ferroelectric thin films are grown on Pt-coated silicon wafers with Pt top contact electrodes. But Pt or Pt-based metal films are not ideal electrodes for FE capacitors and are difficult to dry etch. The problems can include weak adhesion to silicon substrates, as well as unsatisfactory resistance to fatigue. LNO is a perovskite-structured Pauli paramagnet and is a metallic oxide down to 0.4 K [1]. The pseudocubic lattice parameter of LNO is 3.85 A. Since LNO is an intrinsic n-type metallic oxide, though one with a low electron density at the Fermi level [2], it can be used as an oxide electrode with low lattice mismatch to many perovskite ferroelectric materials. In addition, since LNO tends to adopt a (001) fiber texture on flat surfaces [3], it is possible to use the electrode to control the orientation of the ferroelectric films. Based on these advantages, much attention has been paid to LNO electrodes. Previous investigators have reported on the deposition of LNO by pulsed-laser deposition, rf sputtering, metal organic deposition (MOD), sol-gel deposition, and spray-ICP on a variety of substrate materials [4-6]. In this work, DC magnetron sputtering was used to prepare LNO thin films, and sol-gel techniques were used to coat ferroelectric thin films on the LNO bottom electrodes.
73 Mat. Res. Soc. Symp. Proc. Vol. 596 ©2000 Materials Research
Society
EXPERIMENTAL PROCEDURE LNO thin films were deposited on the (100) surface of silicon substrates using DC magnetron sputterin
Data Loading...
