| 1. |
- Bonetti, Stefano, et al.
(författare)
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Buried tantalate-niobate microwave varactors
- 2007
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Ingår i: 2006 15TH IEEE INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS. - 9781424413317 ; , s. 347-350
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Konferensbidrag (refereegranskat)abstract
- We present characteristics of microwave variable capacitors (varactors) buried in 2.5 mu m thick AgTa0.5Nb0.5O3 (ATN) film pulsed laser deposited on sapphire single crystal. 2 gm gap interdigital capacitors (IDC) were fabricated by photolithographic, dry etching and lift-off processes. For comparison, similar IDCs were also defined on top of ATN film. Capacitance and loss tangent have been determined using a modified de-embedding technique in the microwave range 25 MHz - 40 GHz. Buried structures show higher values of capacitance and tunability, keeping the same level of losses compared to standard topped devices and resulting in an increased K-factor = tunability/tan delta. Experimental results are explained within equivalent circuit model. Besides the increased performance, the new design avoids the need of a successive planarization step, which could be required in an integration process.
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| 2. |
- Kim, Jang-Yong, et al.
(författare)
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AgTa0.5Nb0.5O3 thin film coplanar waveguide microwave capacitors
- 2005
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 77, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- 400 nm thick AgTa0.5Nb0.5O3 (ATN) films have been prepared by pulsed laser depositiontechnique on LaAlO3 (001) and sapphire (Al2O3-0112, r -cut) single crystal substrates.Comprehensive X-ray diffraction analysis showed epitaxial quality of ATN/LaAlO3films and preferentially (001) orientation of ATN/Al2O3 films. Voltage tunable microwavecapacitors were fabricated by lift-off technique on the surface of ferroelectricfilms. Microwave on-wafer tests were performed in the range from 1 to 40 GHz. Frequencydispersion is about 4.3%, voltage tunability is 4.7% @ 20 GHz and 200 kV/cm,loss tangent ∼0.068 @ 20 GHz, K-factor=tunability/tanδ is ranged from 124% @10 GHz to 35% @ 40 GHz.
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| 3. |
- Kim, Jang-Yong, et al.
(författare)
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AgTaO3 and AgNbO3 thin films by pulsed laser deposition
- 2006
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 615-618
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Tidskriftsartikel (refereegranskat)abstract
- Silver tantalate AgTaO3 (ATO) and silver niobate AgNbO3 (ANO) films have been grown on to the LaAlO3 (001) and sapphire Al2O3 (0112, r-cut) single crystals by pulsed laser deposition technique from stoichiometric ATO and ANO targets. X-ray diffraction study revealed epitaxial quality of ATO and ANO films on the LaAlO3 (00 1) Whereas on the sapphire r-cut substrate they are preferential (I 10) and (00 1) oriented. To characterize microwave films properties in the range from I to 40 GHz, coplanar line interdigital capacitors were fabricated by photolithography and lift-off technique. ANO film capacitors show superior properties: frequency dispersion was as low as 13%, voltage tunability (40 V, 200 kV/ cm) was about 4.6% at 20 GHz, loss tangent similar to 0.106 at 20 GHz, K-factor-tunability/tan delta from 49% @ 10 GHz to 33% at 40 GHz.
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| 4. |
- Kim, Jang-Yong, et al.
(författare)
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Microwave properties of AgTa0.5Nb0.5O3 thin film varactors on various substrates
- 2007
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Ingår i: 2006 15TH IEEE INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS. - New York : IEEE. - 9781424413317 ; , s. 363-366
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Konferensbidrag (refereegranskat)abstract
- 400nm thick AgTa0.5Nb0.5O3 (ATN) films have been sintered by pulsed laser deposition technique on LaAlO3 (001), sapphire (Al2O3-01 (1) under bar2, r-cut) single crystal substrates and Coming 7059 Glass. Photolithography and metal lift-off technique were used to fabricate tunable Coplanar Waveguide Interdigital Capacitors (CPWIDCs). On-wafer test of varactors was performed with microwave network analyzer and G-S-G microwave probe. ATN/LaAlO3 capacitors demonstrated the highest tunability (similar to 5.8%@20GHz), ATN/Glass showed the best flat dispersion (similar to 3.9%) and ATN/ Al2O3 showed the lowest loss tangent (similar to 0.06@20GHz) in the microwave range from 1 to 40 GHz.
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| 5. |
- Kim, Jang-Yong, et al.
(författare)
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Niobate-tantalate thin films microwave varactors
- 2006
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 619-622
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Tidskriftsartikel (refereegranskat)abstract
- We present comparative characteristics of microwave variable capacitors (varactors) fabricated on Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN) and Ba0.5Sr0.5TiO3 (BST) ferroclectric films sintered by pulsed laser deposition technique. Two port 2 mu m finger gap coplanar waveguide interdigital capacitive (CPWIDC) structures were defined on ferroelectric films surface by a standard lift off technique. Results of the microwave on-wafer tests performed in frequency range 1 to 40 GHz have been examined with a de-embedding technique to extract device characteristics from the measured S-parameters. The frequency dispersion of capacitance was 37%, 4.3%, and 17%; the voltage tunability (200 kV/cm) 22%, 4.7%, and 22% at 20 GHz; loss tangent similar to 0.23, 0.068, and 0.137 at 20 GHz for NKN/Nd:YAlO3, ATN/Al2O3, and BST/Al2O3 films capacitors.
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| 6. |
- Kim, Jang-Yong
(författare)
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Novel tantalate-niobate films for microwaves
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, and electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies. Ferroelectric materials usually have high dielectric constants, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used in fabrication capacitors for electronic industry because of their high dielectric constants, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure, and electrically tunable microwave integrated circuits using ferroelectric thin films can be developed. Therefore, it is very important to characterize the dielectric constant and tunability of ferroelectric thin films. This thesis shows experimental results for growth, crystalline properties and microwave characterization of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering of a stoichiometric, high density, ceramic NKN, ATN, BST target onto single crystal LaAlO3(LAO), Al2O3 (sapphire), and Nd:YAlO3, and amorphous glass substrates. By x-ray diffractometry, NKN, ATN, BST films on LAO substrates were found to grow epitaxially, whereas films on r-cut sapphire substrates were found to be preferentially (00l) oriented. Coplanar waveguide interdigital capacitor (CPWIDC) structures were fabricated by standard photolithography processing and metal lift-off technique. Microwave properties of the NKN/Sapphire and ATN/Sapphire with CPW structures were characterized using on-wafer microwave measurement technique. Measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field through the connection between network analyzer and power supply was applied to measure voltage tunability. Measured S-parameter were used for the calculation of capacitance, loss tanδ, tunability and K-factor. The NKN films interdigital capacitors with 2 μm finger gap on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ∼ 0.13, K-factor = tunability/tanδ from 152% @ 10GHz to 46% @ 40GHz. The microwave performance of ATN film CPWIDC with 2 μm finger gap on sapphire substrate in the microwave range from 1 to 40 GHz showed that frequency dispersion is about 4.3%, voltage tunability was 4.7% @ 20GHz and 200 kV/cm, loss tangent ∼ 0.068 @ 20GHz, K-factor = tunability/tanδ is ranged from 124% @ 10GHz to 35% @ 40GHz. The BST films CPWIDC with 2μmfinger gap on Al2O3 substrate showed frequency dispersion of capacitance in the microwave range from 1 to 40 GHz about 17%, voltage tunability = 1 - C(40V)/C(0) ∼ 22.2%, loss tangent ∼ 0.137 @ 20GHz, and K-factor = tunability/tanδ from 281% @ 10GHz to 95% @ 40GHz.
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| 7. |
- Kim, Jang-Yong, 1971-
(författare)
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Processing and On-Wafer Test of Ferroelectric Film Microwave Varactors
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies. Ferroelectric materials usually have high dielectric constant, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used to fabricate capacitors for electronic industry because of their high dielectric constant, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure and used for electrically tunable microwave integrated circuits. It is an important task to sinter highly tunable and low loss ferroelectrics, fabricate and test the properties of microwave ferroelectric components. This thesis shows experimental results on growth, crystalline and microwave properties of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), and AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering techniques from stoichiometric high density ceramic NKN, ATN, ATO, ANO and BST targets onto LaAlO3 (LAO), Al2O3 (r-cut sapphire), Nd:YAlO3 single crystals and amorphous glass substrates. Advanced X-ray diffraction examinations showed NKN, ATN, BST films on LAO substrates grow epitaxially, whereas films on r-cut sapphire were found to be preferentially (00l) oriented. Coplanar waveguide 2 µm finger gap interdigital capacitor (CPWIDC) structures were fabricated by photolithography process and metal lift-off technique. On-wafer tests up to 40 GHz were performed to characterize microwave properties of the ferromagnetic film CPWIDC devices. The measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field was applied to planar capacitors to measure tunability. Original de-embedding technique has been developed to calculate capacitance, loss tan δ, and tunability of varactors from the measured S-parameters. NKN film interdigital capacitors on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ~ 0.13, K-factor = tunability/tan δ from 152% @ 10GHz to 46% @ 40GHz. The ATN/sapphire CPWIDCs showed the lowest dispersion ~ 4.3% in whole frequency range from 1 to 40 GHz, voltage tunability 4.7% @ 20GHz and 200 kV/cm, lowest loss tangent ~ 0.068 @ 20GHz, K-factor = tunability/tan δ ranged from 124% @ 10GHz to 35% @ 40GHz. BST film CPWIDCs on sapphire showed frequency about 17%, the highest voltage tunability ~ 22.2%, loss tangent ~ 0.137 @ 20GHz, and K-factor = 281% @ 10GHz to 95% @ 40GHz.
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| 8. |
- Kim, Jang. Yong, et al.
(författare)
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Processing and on-wafer test of ferroelectric film microwave varactors
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 88:19, s. 192905-
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Tidskriftsartikel (refereegranskat)abstract
- We present comparative characteristics of microwave variable capacitors (varactors) fabricated on Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), and Ba0.5Sr0.5TiO3 (BST) ferroelectric films grown by rf-magnetron sputtering (NKN) and pulsed laser deposition (ATN and BST) techniques on the sapphire. Two port 2 mu m finger gap coplanar waveguide interdigital capacitors (CPWIDCs) were defined on ferroelectric films surface by photolithographic lift-off technique. Deembedding method was employed to extract properties of CPWIDC from the S parameters measured in microwave range up to 40 GHz. BST films on sapphire substrates show superior tunability of 26% (20 GHz, 200 kV/cm), whereas ATN films possess the lowest tan delta=0.06 at 20 GHz and extremely low dispersion of 4.3% in a whole frequency range of 45 MHz-40 GHz.
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