Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> Films
Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> (BST-0.5) thin films (600 nm) were deposited on single crystal MgO, SrTiO<sub>3</sub> (STO), and LaAlO<sub>3</sub> (LAO) substrates by pulsed laser deposition at an oxygen partial pressure of...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-07-01
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| Series: | Crystals |
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| Online Access: | https://www.mdpi.com/2073-4352/11/8/852 |
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| author | Sandwip K. Dey Sudheendran Kooriyattil Shojan P. Pavunny Ram S. Katiyar Guru Subramanyam |
| author_facet | Sandwip K. Dey Sudheendran Kooriyattil Shojan P. Pavunny Ram S. Katiyar Guru Subramanyam |
| author_sort | Sandwip K. Dey |
| collection | DOAJ |
| description | Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> (BST-0.5) thin films (600 nm) were deposited on single crystal MgO, SrTiO<sub>3</sub> (STO), and LaAlO<sub>3</sub> (LAO) substrates by pulsed laser deposition at an oxygen partial pressure of 80 mTorr and temperature of 720 °C. X-ray diffraction and in situ reflection high-energy electron diffraction routinely ascertained the epitaxial quality of the (100)-oriented nanocrystalline films. The broadband microwave (1–40 GHz) dielectric properties were measured using coplanar waveguide transmission line test structures. The out-of-plane relative permittivity <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo stretchy="false">(</mo><msubsup><mi>ε</mi><mo>⏊</mo><mo>/</mo></msubsup><mo stretchy="false">)</mo></mrow></semantics></math></inline-formula> exhibited strong substrate-dependent dielectric (relaxation) dispersions with their attendant peaks in loss tangent (tanδ), with the former dropping sharply from tens of thousands to ~1000 by 10 GHz. Although homogeneous in-plane strain <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo stretchy="false">(</mo><msub><mi>ϵ</mi><mi>ǁ</mi></msub><mo stretchy="false">)</mo></mrow></semantics></math></inline-formula>, enhances <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ε</mi><mo>⏊</mo><mo>/</mo></msubsup></mrow></semantics></math></inline-formula> with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mmultiscripts><mi>ε</mi><mrow><mi>M</mi><mi>g</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>S</mi><mi>T</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>L</mi><mi>A</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo> </mo></mrow></semantics></math></inline-formula> at lower frequencies, two crossover points at 8.6 GHz and 18 GHz eventually change the trend to: <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mmultiscripts><mi>ε</mi><mrow><mi>S</mi><mi>T</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>L</mi><mi>A</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>M</mi><mi>g</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup></mrow></semantics></math></inline-formula>. The dispersions are qualitatively interpreted using (a) theoretically calculated (T)−<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo stretchy="false">(</mo><msub><mi>ϵ</mi><mi>ǁ</mi></msub><mo stretchy="false">)</mo></mrow></semantics></math></inline-formula> phase diagram for single crystal and single domain BST-0.5 film, (b) theoretically predicted <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>ϵ</mi><mi>ǁ</mi></msub></mrow></semantics></math></inline-formula>-dependent, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ε</mi><mo>⏊</mo><mo>/</mo></msubsup></mrow></semantics></math></inline-formula> anomaly that does not account for frequency dependence, and (c) literature reports on intrinsic and extrinsic microstructural effects, including defects-induced inhomogeneous strain and strain gradients. From the Vendik and Zubko model, the defect parameter metric, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>ξ</mi><mi mathvariant="normal">s</mi></msub></mrow></semantics></math></inline-formula>, was estimated to be 0.51 at 40 GHz for BST-0.5 film on STO. |
| first_indexed | 2024-03-10T08:54:32Z |
| format | Article |
| id | doaj.art-5fbe97df8f034e848877907db21f99fb |
| institution | Directory Open Access Journal |
| issn | 2073-4352 |
| language | English |
| last_indexed | 2024-03-10T08:54:32Z |
| publishDate | 2021-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Crystals |
| spelling | doaj.art-5fbe97df8f034e848877907db21f99fb2023-11-22T07:15:53ZengMDPI AGCrystals2073-43522021-07-0111885210.3390/cryst11080852Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> FilmsSandwip K. Dey0Sudheendran Kooriyattil1Shojan P. Pavunny2Ram S. Katiyar3Guru Subramanyam4Materials Science and Engineering Program (SEMTE), Arizona State University, Tempe, AZ 85287-6106, USADepartments of Physics, Sree Kerala Varma College, Thrissur 680011, IndiaDepartment of Physics, University of Puerto Rico, San Juan, PR 00925-2537, USADepartment of Physics, University of Puerto Rico, San Juan, PR 00925-2537, USACenter of Excellence for Thin-Film Research and Surface Engineering, University of Dayton, Dayton, OH 45469-0232, USABa<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> (BST-0.5) thin films (600 nm) were deposited on single crystal MgO, SrTiO<sub>3</sub> (STO), and LaAlO<sub>3</sub> (LAO) substrates by pulsed laser deposition at an oxygen partial pressure of 80 mTorr and temperature of 720 °C. X-ray diffraction and in situ reflection high-energy electron diffraction routinely ascertained the epitaxial quality of the (100)-oriented nanocrystalline films. The broadband microwave (1–40 GHz) dielectric properties were measured using coplanar waveguide transmission line test structures. The out-of-plane relative permittivity <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo stretchy="false">(</mo><msubsup><mi>ε</mi><mo>⏊</mo><mo>/</mo></msubsup><mo stretchy="false">)</mo></mrow></semantics></math></inline-formula> exhibited strong substrate-dependent dielectric (relaxation) dispersions with their attendant peaks in loss tangent (tanδ), with the former dropping sharply from tens of thousands to ~1000 by 10 GHz. Although homogeneous in-plane strain <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo stretchy="false">(</mo><msub><mi>ϵ</mi><mi>ǁ</mi></msub><mo stretchy="false">)</mo></mrow></semantics></math></inline-formula>, enhances <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ε</mi><mo>⏊</mo><mo>/</mo></msubsup></mrow></semantics></math></inline-formula> with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mmultiscripts><mi>ε</mi><mrow><mi>M</mi><mi>g</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>S</mi><mi>T</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>L</mi><mi>A</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo> </mo></mrow></semantics></math></inline-formula> at lower frequencies, two crossover points at 8.6 GHz and 18 GHz eventually change the trend to: <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mmultiscripts><mi>ε</mi><mrow><mi>S</mi><mi>T</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>L</mi><mi>A</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup><mo>></mo><mmultiscripts><mi>ε</mi><mrow><mi>M</mi><mi>g</mi><mi>O</mi></mrow><mrow><mi>B</mi><mi>S</mi><mi>T</mi><mo>−</mo><mn>0.5</mn></mrow></mmultiscripts><msubsup><mrow></mrow><mo>⏊</mo><mo>/</mo></msubsup></mrow></semantics></math></inline-formula>. The dispersions are qualitatively interpreted using (a) theoretically calculated (T)−<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo stretchy="false">(</mo><msub><mi>ϵ</mi><mi>ǁ</mi></msub><mo stretchy="false">)</mo></mrow></semantics></math></inline-formula> phase diagram for single crystal and single domain BST-0.5 film, (b) theoretically predicted <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>ϵ</mi><mi>ǁ</mi></msub></mrow></semantics></math></inline-formula>-dependent, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ε</mi><mo>⏊</mo><mo>/</mo></msubsup></mrow></semantics></math></inline-formula> anomaly that does not account for frequency dependence, and (c) literature reports on intrinsic and extrinsic microstructural effects, including defects-induced inhomogeneous strain and strain gradients. From the Vendik and Zubko model, the defect parameter metric, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>ξ</mi><mi mathvariant="normal">s</mi></msub></mrow></semantics></math></inline-formula>, was estimated to be 0.51 at 40 GHz for BST-0.5 film on STO.https://www.mdpi.com/2073-4352/11/8/852dielectric permittivityloss tangentepitaxial BST thin filmsmicrowave characterizationhomogeneous in-plane strain engineeringinhomogeneous strain |
| spellingShingle | Sandwip K. Dey Sudheendran Kooriyattil Shojan P. Pavunny Ram S. Katiyar Guru Subramanyam Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> Films Crystals dielectric permittivity loss tangent epitaxial BST thin films microwave characterization homogeneous in-plane strain engineering inhomogeneous strain |
| title | Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> Films |
| title_full | Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> Films |
| title_fullStr | Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> Films |
| title_full_unstemmed | Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> Films |
| title_short | Analyses of Substrate-Dependent Broadband Microwave (1–40 GHz) Dielectric Properties of Pulsed Laser Deposited Ba<sub>0.5</sub>Sr<sub>0.5</sub>TiO<sub>3</sub> Films |
| title_sort | analyses of substrate dependent broadband microwave 1 40 ghz dielectric properties of pulsed laser deposited ba sub 0 5 sub sr sub 0 5 sub tio sub 3 sub films |
| topic | dielectric permittivity loss tangent epitaxial BST thin films microwave characterization homogeneous in-plane strain engineering inhomogeneous strain |
| url | https://www.mdpi.com/2073-4352/11/8/852 |
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