Misfit Strain Driven Phase Transformations in Epitaxial Barium Strontium Titanate Films

2002 ◽  
Vol 718 ◽  
Author(s):  
Z.-G. Ban ◽  
S. P. Alpay
Keyword(s):  
Film Thickness ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Misfit Strain ◽  
Design Parameters ◽  
Misfit Dislocations ◽  
Barium Strontium ◽  
Bst Films ◽  
The One ◽  
Selection Of

AbstractWe develop phase diagrams for single domain epitaxial barium strontium titanate films on cubic substrates as a function of the misfit strain based on a Landau-Devonshire phenomenological model similar to the one developed by Pertsev et al. [Phys. Rev. Lett. 80, 1988 (1998)]. Unusual ferroelectric phases that are not possible in single crystals and bulk ceramics are demonstrated in epitaxially constrained BST films. The misfit strain is correlated with the film thickness quantitatively by taking into account the formation of misfit dislocations that relieve epitaxial stresses during deposition. Theoretical estimation of the dielectric constant of (001) Ba0.7Sr0.3TiO3 and Ba0.6Sr0.4TiO3 films grown on Si, MgO, LaAlO3, and SrTiO3 substrates as a function of film thickness is provided. It is shown that the selection of the substrate and the film thickness can be chosen as design parameters to manipulate the internal stress level in the film to achieve enhanced dielectric response.

Tuning the Tunability in Epitaxial Barium Strontium Titanate Film via Internal Stresses

2002 ◽  
Vol 748 ◽  
Author(s):  
Z.-G. Ban ◽  
S. P. Alpay
Keyword(s):  
Film Thickness ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Film Growth ◽  
Structural Phase ◽  
Misfit Strain ◽  
Substrate Material ◽  
Internal Stresses ◽  
Misfit Dislocations ◽  
Barium Strontium

ABSTRACTThe tunability of epitaxial barium strontium titanate films is analyzed theoretically for the first time using a modified phenomenological Landau-Devonshire approach taking into account the formation of unusual ferroelectric phases that cannot form in bulk and single-crystal ceramics. It is shown that enhanced tunability can be achieved by adjusting the misfit strain especially in the vicinity of a structural phase transformation. The internal stresses in epitaxial films as characterized by the misfit strain can be controlled by changing the substrate material and/or varying the film thickness. The latter is due to the possibility of stress relaxation by formation of misfit dislocations that relieve epitaxial stresses at film growth temperature. Based on the thermodynamic model, we provide quantitative estimations of tunability of (001) Ba0.5Sr0.5TiO3 films on (001) LaAlO3 (LAO) and SrTiO3 (STO) as a function of film thickness. The analysis indicates that films on STO substrates should be as thick as possible in order to achieve optimum tunability. To obtain maximum tunability on LAO substrates, the thickness of films should be as close as possible to a critical film thickness (∼120 nm).

Effects of thermal misfit strains on dielectric features of sandwich barium strontium titanate multilayer thin films on metal plates

2021 ◽  
pp. 2150030
Author(s):  
Hanting Dong ◽  
Liang Ke ◽  
Xiangjun Hui ◽  
Jiangfeng Mao ◽  
Haiqing Du ◽  
...  
Keyword(s):  
Thin Films ◽  
Dielectric Properties ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Composition Range ◽  
Multilayer Films ◽  
Multilayer Thin Films ◽  
Barium Strontium ◽  
Metal Plates ◽  
Bst Films

Effects of thermal misfit strains on dielectric features for sandwich structural barium strontium titanate (BST) thin films on metal plates were investigated via a modified thermodynamic model. When TEC of substrates is closer to that of BST, larger permittivity and tunability can be received. The tendency of permittivities and tunabilities of such films as a function of TEC of substrates agrees with that of single compositional BST films and compositionally graded BST multilayer films. The highest tunability reaches 60% at the biasing field of 300 kV/cm when the films are onto Ti metal. Moreover, Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3 structure can obtain higher tunability than Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3 structure, while Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3 films show better compatible composition range for relatively larger tunability. Dielectric properties of sandwich-like BST films in some references can also be analyzed based on our calculated results.

Effect of Annealing Temperature on the Microstructure of Barium Strontium Titanate Films

2008 ◽  
Vol 368-372 ◽  
pp. 56-58
Author(s):  
Jia Xuan Liao ◽  
En Qiu Li ◽  
Zhong Tian ◽  
Jiang Xu ◽  
Hai Guang Yang
Keyword(s):  
Magnetron Sputtering ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Annealing Temperature ◽  
Structural Characteristics ◽  
Rf Magnetron Sputtering ◽  
Surface And Interface ◽  
Barium Strontium ◽  
Bst Films

Barium strontium titanate (Ba1−xSrxTiO3, BST) films have been prepared on Pt/Ti/SiO2/Si by medium frequency (MF) magnetron sputtering, and subsequently in situ crystallized at 500-700°C. The microstructures of the MF-BST films are studied. BST films prepared by radio frequency (RF) magnetron sputtering and exhibited preferential (110) orientation, are compared. XRD shows that the MF-BST films exhibit preferential (111) orientation and better crystallization than the RF-BST films at the same annealing temperature. AFM displayed that the MF-BST films were smooth and compact. XPS analysis exhibited that the MF-BST films revealed better surface and interface structural characteristics. Their dielectric properties were also compared.

Tunability, Frequency, and Temperature Behavior of Cofired LTCC-Integrated Barium-Strontium-Titanate Shunt Capacitors up to 8 GHz

2013 ◽  
Vol 10 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Sven Rentsch ◽  
Jens Müller ◽  
Matthias Hein
Keyword(s):  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Microwave Properties ◽  
Electrical Field ◽  
New Approach ◽  
Barium Strontium ◽  
Bst Films ◽  
Effects Of Temperature ◽  
Shunt Capacitors ◽  
Shunt Capacitor

A new approach toward embedding barium-strontium-titanate (BST) patches into a commercial low temperature cofired ceramic (LTCC) is described, using a tape transfer technique. Pressure-assisted sintering is successfully employed to achieve flat multilayer multimaterial modules without internal cracks or delaminations. Apart from the description of the processing technology, the paper also presents a specific procedure of determining the microwave properties of embedded thick BST films, which is based on using the experimental evaluation of a shunt capacitor. The permittivity of the embedded BST determined at room temperature is about 214 and remains constant at least from 100 MHz up to 8 GHz. In addition, the effects of temperature and bias voltages on the microwave properties of LTCC BST were studied systematically from 1 MHz up to 8 GHz. We observed a tuning of the permittivity by about −49%, either by raising the temperature from 21°C to 125°C, or by applying a bias electrical field of up to 10 V/μm. Additionally, breakdown voltages were investigated. The embedded BST withstands field strengths of more than 20 V/μm under laboratory conditions.

Tunability, Frequency and Temperature Behavior of Cofired LTCC-Integrated Barium-Strontium-Titanate up to 8 GHz

2012 ◽  
Vol 2012 (CICMT) ◽  
pp. 000447-000454
Author(s):  
Sven Rentsch ◽  
Jens Müller ◽  
Matthias Hein
Keyword(s):  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Microwave Properties ◽  
Specific Procedure ◽  
Electrical Field ◽  
New Approach ◽  
Barium Strontium ◽  
Bst Films ◽  
Effects Of Temperature ◽  
Shunt Capacitor

A new approach towards embedding barium-strontium-titanate (BST) patches into a commercial low temperature co-fired ceramic (LTCC) is described, using a tape transfer technique. Pressure-assisted sintering is successfully employed to achieve flat multi-layer multi-material modules without internal cracks or delaminations. Beside the description of the processing technology, the paper presents also a specific procedure of determining the microwave properties of embedded thick BST films, which is based on using the experimental evaluation of a shunt capacitor. The permittivity of the embedded BST determined at room temperature is about 214 and remains constant at least from 100 MHz up to 8 GHz. In addition, the effects of temperature and bias voltages on the microwave properties of LTCC BST were studied systematically from 1 MHz up to 8 GHz. We observed a tuning of the permittivity by about −49 %, either by raising the temperature from 21°C to 125°C, or by applying a bias electrical field of up to 10 V/μm. Additionally, breakdown voltages were investigated. The embedded BST withstands field strengths of more than 20 V/μm under laboratory conditions.

A phase shifter on a slot line loaded with varactors designed on the basis on nanodimensional films of barium-strontium titanate

2007 ◽  
Vol 52 (11) ◽  
pp. 1300-1304 ◽  
Author(s):  
Vas. M. Mukhortov ◽  
S. I. Masychev ◽  
Yu. I. Golovko ◽  
A. V. Chub ◽  
Vl. M. Mukhortov
Keyword(s):  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Phase Shifter ◽  
Slot Line ◽  
Barium Strontium
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