Realization of high tunability barium strontium titanate thin films by rf magnetron sputtering

Padmini, P.; Taylor, T. R.; Lefevre, M. J.; Nagra, A.S.; York, R.A.; Speck, J. S.

doi:10.1063/1.125272

Cited by 265 publications

(137 citation statements)

References 14 publications

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“…1 together with the reported ones for ͑Ba 0.5 Sr 0.5 ͒TiO 3 film. 2 The changes in capacitance between 0 and 900 kV/ cm for SBTi and CBTi films were 7.0% and 6.5%, respectively, while that for ͑Ba 0.5 Sr 0.5 ͒TiO 3 film was 59%. In addition, the dielectric loss was less than 3%, which was also independent of the applied electric field plotted in Fig.…”

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confidence: 93%

“…[1][2][3][4] The size effect in thin film dielectrics has made it difficult to design their performance characteristics. There has therefore been a strong motivation to discover size-effect-free highly insulating dielectric materials with a high dielectric constant.…”

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confidence: 99%

“…[1][2][3][4] However, the significant drop in the dielectric constant with decreased film thickness, widely known as "size effect," has been reported to become serious. [1][2][3][4] The size effect in thin film dielectrics has made it difficult to design their performance characteristics. There has therefore been a strong motivation to discover size-effect-free highly insulating dielectric materials with a high dielectric constant.…”

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confidence: 99%

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Thickness dependence of dielectric properties in bismuth layer-structured dielectrics

Takahashi

Suzuki

Kojima

et al. 2006

Applied Physics Letters

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1-4 However, the significant drop in the dielectric constant with decreased film thickness, widely known as "size effect," has been reported to become serious. [1][2][3][4] The size effect in thin film dielectrics has made it difficult to design their performance characteristics. There has therefore been a strong motivation to discover size-effect-free highly insulating dielectric materials with a high dielectric constant. In this letter, we propose thin films with c-axis-oriented bismuth layer-structured dielectrics ͑BLDs͒ as candidates for size-effect-free materials.BLDs have a natural superlattice structure along the c axis consisting of two kinds of two-dimensional nanolayers, i.e., a bismuth oxide ͑Bi 2 O 2 ͒ 2+ sheet and a pseudoperovskite block generally described as ͑A m−1 B m O 3m+1 ͒ 2− , where m is the number of BO 6 octahedra in a pseudoperovskite block. Interestingly, BLDs with even m exhibit no ferroelectricity along the c axis. 5,6 In our previous study, we found that c-axis-oriented epitaxial SrBi 2 Ta 2 O 9 ͑SBT, m =2͒ films exhibited no degradation in dielectric constant down to 20 nm in thickness, corresponding to eight unit cells.7 However, their dielectric constant of 55 was obviously not enough to replace the conventional perovskite-structured oxides. We therefore expanded our concept to a higher m of 4, i.e., SrBi 4 Ti 4 O 15 ͑SBTi͒ and CaBi 4 Ti 4 O 15 ͑CBTi͒, to obtain higher dielectric constant and to deepen the understanding of the basic characteristics of c-axis-oriented BLD films. As a result, we found the design concept of their properties and revealed that thin films of c-axis-oriented BLDs are promising candidates for high-density capacitor application. c-axis-oriented epitaxial SBTi and CBTi films were grown at a substrate temperature of 700°C by metal organic chemical vapor deposition. ͑001͒ c -oriented epitaxial SrRuO 3 ͑SRO͒ films having an atomically flat surface grown on ͑001͒STO single crystals were used as substrates. 8 The constituent phase and the orientation were identified by conventional x-ray diffraction ͑XRD͒. The crystal structure was analyzed in detail by XRD using synchrotron radiation ͑SPring-8, BL13XU͒. 9 The dielectric and insulation properties of the films were measured after formation of the top electrodes of 100 m Pt on the film surface followed by postannealing in an electrical furnace at 400°C for 30 min under 1 atm flowing oxygen ambience.a͒ Electronic

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Thickness dependence of dielectric properties in bismuth layer-structured dielectrics

Takahashi

Suzuki

Kojima

et al. 2006

Applied Physics Letters

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“…So, the film has high tunability. Padmini et al 17 reported that when a BST film was subjected to tensile stress, a contraction occurred along the c axis leading to an enhancement of the in-plane oriented polar axis. By a converse electrostrictive effect, the in-plane tensile stress reduces the capacitance in the thickness direction of the film.…”

Section: -2mentioning

confidence: 99%

Effect of CaRuO3 interlayer on the dielectric properties of Ba(Zr,Ti)O3 thin films prepared by pulsed laser deposition

Tang

Tian

Wang

et al. 2006

Applied Physics Letters

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Ba͑Zr 0.2 Ti 0.8 ͒O 3 ͑BZT͒ thin films on Pt͑111͒ / Ti/ SiO 2 /Si͑100͒ substrates without and with CaRuO 3 ͑CRO͒ buffer layer were fabricated at 650°C in situ by pulsed laser deposition. The BZT thin films showed a dense morphology, many clusters are found on the surface images of BZT/Pt films, which are composed by nanosized grains of 25-35 nm; the average grain size of BZT/CRO films is about 80 nm, which lager than that of BZT/Pt thin film. The dielectric constants and dissipation factors of BZT/Pt and BZT/CRO thin films were 392 and 0.019 and 479 and 0.021 at 1 MHz, respectively. The dielectric constant of BZT/Pt and BZT/CRO thin films changes significantly with applied dc bias field and has high tunabilities and figures of merit of ϳ70% and 37 and 75% and 36, respectively, under an applied field of 400 kV/ cm. The possible microstructural background responsible for the high dielectric constant and tunability was discussed. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2360177͔ Barium strontium titanate ͑Ba, Sr͒TiO 3 ͑BST͒ thin films have currently become very attractive for applications in decoupling capacitors, storage capacitors, dynamic randomaccess memory, and tunable microwave devices. 1,2 The large electric field-depended dielectric constant can be used for devices such as tunable oscillators, filters, and phase shifters. In such devices, it is desirable to have a high dielectric tunability in a certain electric field range and low dielectric loss. Ba͑Zr y Ti 1−y ͒O 3 ͑BZT͒ is a possible choice as an alternative to BST in the fabrication of ceramic capacitors 3,4 because Zr 4+ is chemically more stable than Ti 4+ . The ferroelectric phase transition at the Curie temperature ͑T C ͒ in BZT bulk ceramics is known to change significantly with Zr content. BZT ceramics exhibit a diffuse phase transition and have high tunability in compositions with y ജ 0.20. [3][4][5][6] The fabrication of BZT thin films by rf-magnetron sputtering, 7 sol-gel method, 8 and pulsed laser disposition ͑PLD͒, 9 and their dielectric properties have been reported recently. Many efforts have been made to improve the dielectric properties of the BST thin film capacitors, including using conductive oxide electrodes such as ͑Ba, Sr͒RuO 3 , 10 ͑La 0.7 Sr 0.3 ͒MnO 3 , 11 LaNiO 3 , 12 and yttrium barrium copper oxide ͑YBCO͒. 13 The effects of CaRuO 3 buffer layer on the dielectric properties and tunability of BZT films have not yet been reported. In this work, Ba͑Zr 0.2 Ti 0.8 ͒O 3 thin films growth on Pt/ Ti/ SiO 2 / Si substrate without and with CaRuO 3 buffer layer were prepared by pulsed laser disposition. The orientation characteristics of grains, dielectric properties, tunability, and figure of merit of the columnar-grained Ba͑Zr 0.2 Ti 0.8 ͒O 3 thin films on Pt/ Ti/ SiO 2 / Si substrate without and with CaRuO 3 buffer layer are also reported.CaRuO 3 ͑CRO͒ bottom electrode layer was grown on Pt/ Ti/ SiO 2 / Si substrates at 750°C by rf-magnetron sputtering and using a CRO target. Ba͑Zr 0.2 Ti 0.8 ͒O 3 ͑BZT͒ thin films were gr...

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“…TMOs have been grown by a number of techniques such as solvo-thermal synthesis, 11 sol-gel techniques, physical vapor deposition techniques such as radiofrequency (RF) sputtering 13,14 and e-beam evaporation, 15 and chemical vapor deposition (CVD) including metalorganic CVD (MOCVD) 16 and thermal CVD. [17][18][19][20] Synthesis techniques such as hydrothermal or sol-gel deposition are advantageous for low temperature synthesis of nanostructures, but often result in the inclusion of undesired precursor ions or solvent molecules that can have a significant impact on the electrical properties of the TMOs.…”

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confidence: 99%

Modulation of stoichiometry, morphology and composition of transition metal oxide nanostructures through hot wire chemical vapor deposition

et al. 2015

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A hot wire chemical vapor deposition technique is described for synthesis of 1D nanostructures of a controlled morphology, stoichiometry, and composition. The synthesis involves the evaporation and condensation of metal oxide vapor through the reaction of oxygen with the hot filaments of respective transition metals. The stoichiometry and morphology of MoO 3 and WO 3 were modulated by varying the filament temperature and partial pressure of oxygen in the growth chamber. Based on the results under different conditions, a morphological phase diagram, and a growth model based on the extent of gas phase supersaturation were developed to understand the growth mechanism. Further, ternary transition metal oxide, NiMoO 4, was synthesized as a proof-of-concept for tuning the composition of deposition through simultaneous evaporation of two metal oxides.

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Realization of high tunability barium strontium titanate thin films by rf magnetron sputtering

Abstract: TABLE I. Sputtering conditions for BST deposition. Target Ba 0.5 Sr 0.5 TiO 3 Target diameter 3 in. Source to substrate distance 4 in. RF power 90 W Sputtering gas Ar/O 2 ͑sccm͒ Substrate temperature 450-650°C Gas pressure 50 mT Deposition rate 0.4 nm/min

Cited by 265 publications

References 14 publications

Thickness dependence of dielectric properties in bismuth layer-structured dielectrics

Thickness dependence of dielectric properties in bismuth layer-structured dielectrics

Effect of CaRuO3 interlayer on the dielectric properties of Ba(Zr,Ti)O3 thin films prepared by pulsed laser deposition

Modulation of stoichiometry, morphology and composition of transition metal oxide nanostructures through hot wire chemical vapor deposition

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