Solution Chemistry, Substrate, and Processing Effects on Chemical Homogeneity in Lead Zirconate Titanate Thin Films

• Published in: Journal of the American Ceramic Society 2015-07, Vol.98 (7), p.2028-2038
• Main Authors: Ihlefeld, Jon F., Kotula, Paul G., Gauntt, Bryan D., Gough, Dara V., Brennecka, Geoff L., Lu, Ping, Spoerke, Erik D.
• Format: Article
• Language: English
• Subjects: Crystallization; Heating; Solution chemistry; Spectrum analysis; Temperature effects; Thin films; Titanium
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.13576

The effects of chemistry, substrate, and processing conditions on through‐thickness cation distributions are explored in solution‐derived morphotropic composition lead zirconate titanate (PZT) films. Films prepared from chelate‐based and conventional sol–gel chemistries were spin cast onto Pt/ZnO/SiO2/Si and Pt/Ti/SiO2/Si substrates and pyrolyzed at 300°C, 350°C, and 400°C prior to crystallization at 700°C either in a preheated furnace or via rapid thermal processing. For films crystallized within a conventional furnace on Pt/ZnO/SiO2/Si substrates no chemical gradients were observed. All films prepared on Pt/Ti/SiO2/Si substrates had increased titanium concentrations near the PZT/Pt interfaces, and the source is shown to be titanium diffusing from the substrate metallization stack. The effect of heating method and rate was explored in films prepared on Pt/ZnO/SiO2/Si substrates with 15°C, 50°C, and 100°C/s heating rates within a rapid thermal annealer. Only one solution chemistry‐heating rate combination resulted in the formation of a chemical gradient: a conventional sol–gel chemistry and a 50°C/s heating rate. Infrared spectroscopy of pyrolyzed gel films showed absorption spectra differences in the bonding structure between the two chemistries with the conventional sol–gel‐derived films exhibiting a signature more similar to that of a PbTiO3 gel, suggestive of a gel‐structure source of gradient formation during crystallization.