Dielectric tunability transition in Ba0.6Sr0.4TiO3-based capacitors

Qiu, Jie; Liu, Guozhen; Sakai, Joe; Gervais, F.; Wolfman, J.

doi:10.1063/1.3641980

Cited by 7 publications

(3 citation statements)

References 22 publications

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“…Based on previous literature, it appears that a suitable equivalent circuit for the epitaxial PZT films should include at least the following elements: a Schottky type capacitance associated with the electrode interfaces; a parallel R-C connection associated with the ferroelectric volume; a resistance associated with the electrodes. [39][40][41] Here, we show that the above mentioned equivalent circuit can be generalized and used to simulate the frequency dependence of impedance in the case of epitaxial films of BTO and Pb(Zr 0.2 Ti 0.8 )O 3 (PZT), with different structural orientations and with different metals as electrodes. Furthermore, it is shown that the equivalent circuit of a capacitor based on epitaxial ferroelectric film can be reduced to a simple R-C serial connection, in contrast to the parallel R-C connections used for ceramics.…”

Section: Introductionmentioning

confidence: 94%

General equivalent circuit derived from capacitance and impedance measurements performed on epitaxial ferroelectric thin films

Pintilie

Hrib

Pasuk

et al. 2014

Journal of Applied Physics

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Voltage and frequency dependent capacitance measurements were performed on epitaxial BaTiO3 and Pb(Zr0.2Ti0.8)O3 thin films deposited on single crystal SrTiO3 substrates with (001) and (111) orientations. The measured capacitors have common bottom SrRuO3 contact and different metals as top electrodes: SrRuO3, Pt, Cu, Al, and Au. The capacitance-voltage characteristics were used to extract information regarding the density of the free carriers and the linear contribution to the static dielectric constant. The frequency dependent impedance was used to develop a suitable equivalent circuit for the epitaxial ferroelectric capacitors. It was found that the frequency dependence of the imaginary part of the impedance can be well simulated, in all cases, using a circuit composed of Schottky-type capacitance related to electrode interfaces, contact resistance, and the R-C parallel connection related to the ferroelectric volume of the film. Values for the components of the equivalent circuit were obtained by fitting the experimental data with the simulated curves. These were then used to extract quantities such as dielectric constant in the ferroelectric volume, the width of the depletion layers, and the apparent built-in potential. It was found that, although the investigated capacitors are of different ferroelectric materials, grown on substrates with different orientations, and having different metals as top electrodes, the values for the capacitance associated with the Schottky contacts and the apparent built-in potential are not very different. The results suggest a strong influence of ferroelectric polarization on the electrode interface properties in the case of epitaxial ferroelectric films.

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Section: Introductionmentioning

confidence: 94%

General equivalent circuit derived from capacitance and impedance measurements performed on epitaxial ferroelectric thin films

Pintilie

Hrib

Pasuk

et al. 2014

Journal of Applied Physics

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“…Barium strontium titanate (BST), as the material for nonlinear capacitors, exhibits high permittivity, high tunability and low dielectric loss at room temperature and in the microwave frequency range [1]. High quality BST films and capacitors have been prepared, and their electrical properties have also been investigated [2][3][4][5][6]. Since BST has a cubic crystal structure, BST films have been deposited on cubic crystal substrates such as MgO and SrTiO 3 .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Microwave Capacitors and Tunable Waveguides on (Ba, Sr)TiO<sub>3</sub> Films Deposited on Sapphire Substrates

Nishida

Onodera

2014

Trans. Mat. Res. Soc. Japan

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Tunable microwave devices have been widely investigated because next generation information communication equipment will require accommodation of several communication protocols and frequencies. Barium strontium titanate (Ba,Sr)TiO 3 (BST) thin films are expected to be applied in such devices because of their nonlinear dielectric characteristics in microwave frequencies. BST thin films have been deposited on various substrate materials, such as sapphire, MgO and glass, and the characteristics of thin film capacitors fabricated using BST have been investigated. The evaluation of electrical properties on in-plane type BST capacitors with inter-digital electrodes (IDE) and coplanar waveguide (CPW) type devices is important; however, there have been few detailed analyses or reports thus far. We prepared IDE and CPW electrodes of various sizes on BST films on sapphire. The size and voltage dependence of the capacitance and filter characteristics was determined. In this work, BST epitaxial films were deposited on sapphire substrates by rf magnetron sputtering. In order to obtain higher tunability, IDE electrodes with fine patterns below 1 µm were fabricated by electron beam (EB) lithography. The bias voltage dependence of the capacitance of the IDEs was measured. The tunability was found to increase with decreasing electrode spacing. The maximum tunability of 13.6 % was obtained at 100 nm IDE. CPW resonators of 6 mm length and 0.14 mm width were also prepared on BST (BST CPW) by EB lithography. The resonance frequency of 6.9 GHz of the BST CPW was calculated by a microwave simulator, which agreed with the measurement result of 7.47 GHz. A frequency shift of 1.1 % with bias voltage (50 V) was measured, revealing that a CPW type microwave tunable filter was successfully obtained on the BST/sapphire structure.

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“…Mostly deposited by PVD or PLD [1], alternative processes like sol-gel or metal oxide decomposition (MOD) are growing since a decade because of their low cost production [2][3][4] and more recently because of their ability to coat complex shapes (3D) [5]. To date, film densification and crack issues are the common technological bottle-necks for further improvements [6].…”

Section: Introductionmentioning

confidence: 99%