Extremely High Tunability and Low Loss in Nanoscaffold Ferroelectric Films

Abstract

There are numerous radio frequency and microwave device applications which require materials with high electrical tunability and low dielectric loss. For phased array antenna applications there is also a need for materials which can operate above room temperature and which have a low temperature coefficient of capacitance. We have created a nanoscaffold composite ferroelectric material containing Ba(0.6)Sr(0.4)TiO(3) and Sm(2)O(3) which has a very high tunability which scales inversely with loss. This behavior is opposite to what has been demonstrated in any previous report. Furthermore, the materials operate from room temperature to above 150 °C, while maintaining high tunability and low temperature coefficient of tunability. This new paradigm in dielectric property control comes about because of a vertical strain control mechanism which leads to high tetragonality (c/a ratio of 1.0126) in the BSTO. Tunability values of 75% (200 kV/cm field) were achieved at room temperature in micrometer thick films, the value remaining to >50% at 160 °C. Low dielectric loss values of <0.01 were also achieved, significantly lower than reference pure films.

New strain states and radical property tuning of metal oxides using a nanocomposite thin film approach

“…1 In these composites, new phenomena also occur giving a very powerful way to tune device functionality. Very high ferroelectric Curie temperatures, 2 strongly improved dielectric tunability, 3 reducing dielectric loss, 4 enhanced multiferroic coupling, 5 photostriction-magnetic coupling, 6 strongly enhanced current densities in superconductors, 7 new kinds of memristor devices, 8 and strongly enhanced ionic conduction at lower temperatures have all been reported. 9,10 However, the understanding and origin of unusual strain states in nanocomposite films have not been explored to date.…”

“…Again, unusual strain states were thought to be responsible. 3 In this work, we explore the strain states in the (Ba 0.6 Sr 0.4 TiO 3 ) 1−x (Sm 2 O 3 ) x ((BSTO) x − (SmO) 1−x ) thin film system. The system is ideal from the chemical point of view because there is minimal intermixing between the two component phases.…”

“…3 favorable as it enables SmO lattice matching of 1.0927/4 × √ 2 = 0.3863 nm with [100] (0.3905 nm) in STO. 11 The lattice parameters of the films were determined from a combination of XRD reciprocal space maps (RSMs) of the asymmetric (113) reflections and 2θ − ω scans (not shown) of the symmetric (00l) peaks (Figs.…”

“…The analysis assumes that the BSTO is tetragonal which is expected from the literature. 3 Concentrating first on the RSMs and in-plane parameters, we focus on the position of the BSTO (113) peaks along q x . The position of the centers of these peaks along q x is shown by the white dashed lines and they indicate how the in-plane a lattice parameters change with x ( Fig.…”

Synthesis of Heteroleptic Strontium Complexes Containing Substituted Cyclopentadienyl and β-Diketonate Ligands

“…In the second step the mono cyclopentadienyl strontium iodide was treated with sodium salt of 2,2,6,6-tetramethyl-3,5-heptanedione in THF. The product was extracted to toluene and dried from the solvents to get the pure products as Sr( i Pr 3 Cp)(tmhd) (1) and Sr( t Bu 2 Cp) (tmhd) (2). Both the compounds were characterized by NMR, IR spectroscopy, and elemental analysis as well as thermogravimetric analysis to study the decomposition character.…”