Chemical and microstructural characterization of rf-sputtered BaTiO3 nano-capacitors with Ni electrodes

• Published in: Applied surface science 2012-05, Vol.258 (15), p.5599-5604
• Main Authors: Reck, James N., Cortez, Rebecca, Xie, S., Zhang, Ming, O’Keefe, Matthew, Dogan, Fatih
• Format: Article
• Language: English
• Subjects: Capacitors; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Dielectric; Exact sciences and technology; Nano-technology; Physics; Sputtering
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.02.035

► Sputter deposited BaTiO3 nano-capacitors ∼100nm thick were characterized. ► AFM and SEM confirmed the films to be smooth and conformal with no macro-defects such as pores or cracks. ► TEM and XRD indicate the films were either amorphous or nanocrystalline. ► XPS showed the films had excess oxygen and Ba:Ti ratios ranging from 0.78 to 1.1. ► No correlation between the chemical/microstructural features and dielectric properties (permittivity up to ∼1000 and losses below 0.1). Chemical and microstructural evaluation techniques have been used to characterize sputter deposited 100–150nm thick BaTiO3 nano-capacitors with 30nm thick Ni electrodes fabricated on Si/SiO2 wafers. More than 99% of devices had resistance>20MΩ. Electrodes were found to have a roughness, Ra, of about 0.66±0.04nm, and the BaTiO3 had a Ra value of 1.3±0.12nm. Characterization of the BaTiO3 film chemistry with X-ray Photoelectron Spectroscopy (XPS) showed the films had excess oxygen and Ba:Ti ratios ranging from 0.78 to 1.1, depending on sputtering conditions. X-ray diffraction showed a broad peak between approximately 20° and 35° 2θ, indicating the films were either amorphous or contained grain sizes less than 5nm. Focused ion beam images confirmed the presence of smooth, conformal films, with no visible signs of macro-defects such as pin-holes, cracks, or pores. High resolution transmission electron microscopy (TEM) and electron diffraction patterns confirmed the presence of a nearly amorphous film with limited short range order. No correlation was found between the chemical and microstructural studies with the dielectric permittivity (280–1000), loss (0.02–0.09), and/or resistivity (8.7×1010–1.5×1012Ωcm) values.