Surface Chemical and Leakage Current Density Characteristics of Nanocrystalline Ag–Ba_0.5Sr_0.5TiO₃ Thin Films

Abstract

Nanocrystalline xAg-(1Àx)Ba 0.5 Sr 0.5 TiO 3 (Ag-BST, 0rxr0.1, where x is the mole fraction of Ag) thin films have been deposited on Pt/Ti/SiO 2 /Si substrates by a sol-gel method. The films have been characterized by X-ray diffraction (XRD), scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The core-level XPS of oxygen (O1s) of the Ag-BST films indicate that an optimum amount of Ag (x 5 0.02 or 2 mol%) enhances the binding energy of oxygen, possibly through a mechanism in which the electrophilic oxygen dissociates from the Ag surface and fills the oxygen vacancies. Similarly, the binding energy of Ag (Ag3d) shows a shift toward a higher value with increasing Ag up to 4 mol%, probably because of the chemical shift of Ag in BST along the surface layers, surface relaxation, or changes in the Fermi level of small Ag particles in the solid solution range of Ag in BST films (xr0.04). The leakage current density of 2 mol% Ag-added BST (B10 À6 A/cm 2 ) is less by about an order of magnitude than pure BST at an electric field of 200 kV/cm. A defect model is proposed to explain the observed leakage current density of Ag-BST films satisfactorily.

Dielectric microwave characterizations of (Ba,Sr)TiO3 film deposited on high resistivity silicon substrate: Analysis by two-dimensional tangential finite element method

“…Ferroelectric thin films, such as ͑Ba, Sr͒TiO 3 ͑BST͒, are being widely investigated for applications in integrated dynamic random access memory cells, decoupling capacitors, and microwave tunable devices, including tunable mixers, delay lines, filters, and phase shifters for steerable antennas. [1][2][3] As Pb͑Zr, Ti͒O 3 for piezoelectric micro/ nanosystems applications, 4 BST has become the leading materials system for these devices due to its high dielectric response and its tunability near the ferroelectric phase transformation temperature. The transition temperature ͑Tc͒ can be controlled via adjusting composition; for example, the Tc of bulk Ba 0.60 Sr0 0.40 TiO 3 ͑60/40͒ is just below room temperature.…”

Perfectly (001)‐ and (111)‐Oriented (Ba,Sr)TiO3 Thin Films Sputtered on Pt/TiOx/SiO2/Si Without Buffer Layers

“…E pitaxial and polycrystalline Ba x Sr 1− x TiO 3 (BST) thin films have been the focus for dynamic random access memories and frequency agile passive rf/microwave devices 1,2 . For high‐density ferroelectric memory, the preferentially oriented films should be fabricated in order to continue scaling of ferroelectric memory devices.…”

“…E PITAXIAL and polycrystalline Ba x Sr 1Àx TiO 3 (BST) thin films have been the focus for dynamic random access memories and frequency agile passive rf/microwave devices. 1,2 For highdensity ferroelectric memory, the preferentially oriented films should be fabricated in order to continue scaling of ferroelectric memory devices. Epitaxial Ba x Sr 1Àx TiO 3 films have been prepared, using various techniques, on different single-crystal substrates such as LaAlO 3 and Al 2 O 3 .…”

Improved Dielectric Properties of Bi1.5Zn1.0Nb1.5O7/(111)‐Oriented Ba0.6Sr0.4TiO3 Bilayered Films for Tunable Microwave Applications

“…I n recent years, much attention has been devoted to the development of tunable dielectric materials for voltage‐controlled, frequency‐agile phase shifters and filters operating in the microwave regime 1–3 . Ferroelectrics such as Ba 1− x Sr x TiO 3 have emerged as leading candidates for such applications due to their highly nonlinear dielectric response to an applied electric field 4–8 .…”