Thickness-dependent structural and electromechanical properties of (Na0.85K0.15)0.5Bi0.5TiO3multilayer thin film-based heterostructures

Yunyi Wu, Siu Wing Or

Research output: Journal article publicationJournal articleAcademic researchpeer-review

7 Citations (Scopus)


(Na 0.85K 0.15) 0.5Bi 0.5TiO 3 (NKBT) multilayer thin films with different thicknesses of 100–700 nm, corresponding to 2–14 layers with each layer of ~50 nm thickness, are synthesized on Pt(111)/Ti/SiO 2/Si substrates to form Pt/NKBT/Pt/Ti/SiO 2/Si heterostructures using different spin-coating and annealing conditions in a modified aqueous sol-gel process. The multilayer thin films spin-coated by two steps (step 1/2) at 600/4000 rpm for 6/30 s and annealed at 700 °C for 5 min with a heating rate of 30 °C/s show a dense, uniform, and continuous morphology as well as a pure perovskite structure with a rhombohedral–tetragonal phase transition at ~140 °C and no preferential orientation in the heterostructures. Their structural and electromechanical properties exhibit consistent improvement trends with increasing thickness from 100 to 550 nm (i.e., 2–11 layers). The 550 nm-thick, 11-layer films demonstrate the best ferroelectric, dielectric, piezoelectric, and electric performance in terms of the highest remnant polarization, saturation polarization, dielectric constant, and effective piezoelectric constant of 18.3 μC/cm 2, 53.6 μC/cm 2, 463, and 64 pm/V, as well as the lowest coercive field, dielectric loss tangent, and leakage current density of 116 kV/cm, 0.057, and 27 μA/cm 2, respectively. The observed thickness-dependent improvement is explained by an interfacial passive layer effect where the motion of both 180° and non-180° domain walls is enhanced in the thicker multilayer thin films by weakening the influence of domain pinning in the interfacial passive layers between the multilayer thin films and the substrates.

Original languageEnglish
Pages (from-to)153-164
Number of pages12
JournalMaterials and Design
Publication statusPublished - 5 Jul 2018


  • Heterostructures
  • Interfacial passive layer
  • Lead-free piezoelectric
  • Multilayer thin films
  • Thickness-dependent properties

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering


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