Ferroelectric and dielectric study of strontium tantalum based perovskite oxynitride films deposited by reactive rf magnetron sputtering

Abstract

International audienceStrontium and tantalum based oxynitride perovskite thin films were deposited by reactive magnetron sputtering. Epitaxial films deposited on Nb-SrTiO₃ substrates show smooth surfaces with roughness values from 1.5 to 3.6 nm for a thickness of films in the range 20–1600 nm. The samples are yellow with band gap values around 2.35 eV. Piezo-force microscopy characterization pointed out the local piezoelectric and ferroelectric behavior of the oxynitride perovskite films. In the low frequency range, the 1600 nm-thick film exhibits a permittivity of 175 at 10 kHz, with dielectric losses of 0.055. Permittivity is lowered in high frequencies with a value around 65 obtained on a 1520 nm-thick film deposited on MgO substrate, which is textured with a preferential c-axis orientation. No accordability of the permittivity was highlighted at a macroscopic scale. The moderate crystallographic strain evidenced in the 20 nm thin film does not induce a high permittivit

Ferroelectricity and high tunability in novel strontium and tantalum based layered perovskite materials

“…We will compare our results to those obtained on standard ferroelectrics, for example Ba 1-x Sr x TiO 3 [3,4], as well as isotype layered perovskite systems such as (Sr,La) 2 (Ta,Nb) 2 O 7 ceramics [9] and Sr 2 (Ta 1-x Nb x ) 2 O 7 as single-crystals [10,11] and thin films [12][13][14]. The present work relies also on our previous studies concerning La 2 Ti 2 O 7 in the form of ceramics [15] and thin films [16] and our first attempt to produce directly STLT films [17].…”

Compositional effects on the electrical properties of extremely disordered molybdenum oxynitrides thin films

“…For oxynitrides, the oxidation state of the cations, the bond covalence and the band structure can be tuned by mixing oxygen and nitrogen. The wide range of electronic and optical properties make them promising candidates for photocatalysis [1,2], electronic [3,4,5] and solar energy applications [6].…”

Strain Engineering for Anion Arrangement in Perovskite Oxynitrides

“…First-principles calculations suggested that compressive biaxial stress stabilizes the metastable ferroelectric trans structure relative to the most stable cis structure, and classical ferroelectric behavior was observed in tetragonally strained SrTaO 2 N epitaxial thin films grown on Nb:SrTiO 3 (NSTO) substrates. However, no experimental evidence for the trans -type anion configuration was obtained. , Neutron diffraction analysis, which has been used to determine the anion arrangements in bulk mixed-anion compounds, is not applicable to thin-film samples, because of their small volumes. Consequently, the concept of strain engineering for anion arrangement in mixed-anion compounds is still a controversial issue.…”

“…However, no experimental evidence for the trans-type anion configuration was obtained. 16,17 Neutron diffraction analysis, which has been used to determine the anion arrangements in bulk mixed-anion compounds, is not applicable to thin-film samples, because of their small volumes. Consequently, the concept of strain engineering for anion arrangement in mixed-anion compounds is still a controversial issue.…”