Ferroelectric Sr-2(Nb, Ta)(2)O-7 thin films prepared by chemical solution deposition

Ferroelectric Sr-2(Nb,Ta)(2)O-7 (SNTO) thin films were prepared by chemical solution deposition process, i.e. the modified sol-gel-method. The stock s olutions were spin-coated onto either Pt/Ti/SiO2/Si(100) or Pt/TiO2/SiO2/Si (100) substrate. After multiple coating/baking steps, dried thin film stack s were annealed for crystallization at 850-1000 degreesC in oxygen. X-ray d iffraction (XRD) and scanning electron microscope (SEM) analyses revealed t hat the crystallization temperature by modified sol-gel process can be lowe red to 850 degreesC if Pt/TiO2/SiO2/Si(100) substrate was used, while tempe rature higher than 950 degreesC is required for Pt/Ti/SiO2/Si(100) substrat e. Leakage current and relative permittivity (epsilon (r)) values were meas ured in the range of about 10(-9)-10(-7) A/cm(2), and 30-45, respectively, depending on the composition, heat-treatment and substrate type. Polarizati on hysteresis loops were not saturated regardless of composition and anneal ing temperature. Remanent polarization (2P(r)) and coercive field (E-c) val ues for typical SNTO(30/70) film were approximately 1.9 muC/cm(2), and 17 k V/cm, respectively, when +/-5 V pulse was applied.