The dielectric and flexoelectric properties of Mg2+/K+ doped BST films

ABSTRACTBa0.5Sr0.5TiO3 (BST) is one of the high-k candidates for replacing SiO2 as the gate dielectric in future generation devices. The biggest obstacle to scaling the equivalent oxide thickness (EOT) of BST is an interfacial layer, SixOy, which forms between BST and Si. Nitrogen (N2) implantation into the Si substrate has been proposed to reduce the growth of this interfacial layer. In this study, capacitors (Pt/BST/Si) were fabricated by depositing thin BST films (50Å) onto N2 implanted Si in order to evaluate the effects of implant dose and annealing conditions on EOT. It was found that N2 implantation reduced the EOT of RF magnetron sputtered and Metal Oxide Chemical Vapor Deposition (MOCVD) BST films by ∼20% and ∼33%, respectively. For sputtered BST, an implant dose of 1×1014cm−;2 provided sufficient nitrogen concentration without residual implant damage after annealing. X-ray photoelectron spectroscopy data confirmed that the reduction in EOT is due to a reduction in the interfacial layer growth. X-ray diffraction spectra revealed typical polycrystalline structure with (111) and (200) preferential orientations for both films. Leakage for these 50Å BST films is on the order of 10−8 to 10−5 A/cm2—lower than oxynitrides with comparable EOTs.

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K and Mg doping effects on structural and dielectric properties in multilayer BST/ST/BST films

Integrated Ferroelectrics ◽

10.1080/10584587.2018.1457338 ◽

2018 ◽

Vol 190 (1) ◽

pp. 91-100

Author(s):

Xiao Chao Xu ◽

Yun Feng Zhang ◽

Jia Xuan Liao ◽

Zi Qiang Xu

Keyword(s):

Dielectric Properties ◽

Mg Doping ◽

Doping Effects ◽

Bst Films

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

Functional Materials Letters ◽

10.1142/s1793604721500302 ◽

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.

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Low-temperature fabrication of high-quality (Ba, Sr)TiO3 films using charged liquid cluster beam method

Journal of Materials Research ◽

10.1557/jmr.2002.0279 ◽

2002 ◽

Vol 17 (8) ◽

pp. 1888-1891 ◽

Cited By ~ 5

Author(s):

Hyungsoo Choi ◽

Sungho Park ◽

Yi Yang ◽

HoChul Kang ◽

Kyekyoon (Kevin) Kim ◽

...

Keyword(s):

Dielectric Constant ◽

Low Temperature ◽

Cluster Beam ◽

High Quality ◽

Carboxylate Ligands ◽

Si Substrates ◽

Beam Method ◽

Temperature Deposition ◽

Bst Films ◽

Substrate Temperatures

Low-temperature deposition of high-quality (Ba, Sr)TiO3 (BST) thin films was achieved in air on Pt/Ti/SiO2/Si substrates using the charged liquid cluster beam (CLCB) method. The Ba, Sr, and Ti precursors were synthesized using alkoxy carboxylate ligands to tailor their physical properties to the CLCB process. The as-deposited BST films fabricated at substrate temperatures as low as 280 °C exhibited high purity. The leakage current density and dielectric constant of the film, deposited at 300 °C and subsequently annealed at 700 °C, were 2.5 × 10−9 A/cm2 at 1.5 V and 305, respectively.

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Improved Deposition Process of CVD-(Ba,Sr)TiO3 on Ru

MRS Proceedings ◽

10.1557/proc-655-cc6.5.1 ◽

2000 ◽

Vol 655 ◽

Author(s):

M. Tarutani ◽

T. Sato ◽

M. Yamamuka ◽

T. Kawahara ◽

T. Horikawa ◽

...

Keyword(s):

Electrical Properties ◽

Inductively Coupled Plasma ◽

Deposition Process ◽

Molar Ratio ◽

Inductively Coupled ◽

Icp Ms ◽

Plasma Mass Spectrometry ◽

Bst Films ◽

20 Nm ◽

Uniform Composition

Abstract(Ba,Sr)TiO3 [BST] films were deposited by the flash vaporization CVD method with a unique liquid delivery system. An inductively coupled plasma mass spectrometry [ICP-MS] analysis revealed the decline of (Ba+Sr)/Ti molar ratio of the initial BST-layer on Ru. By readjusting the flow ratio of liquid sources and using a two-step deposition method, we obtained 30-nm-thick BST films with uniform composition profile, exhibiting good electrical properties. The leakage property, however, was severely deteriorated in BST films less than 24 nm thick. A SEM observation showed the presence of micro-roughness or micro-hillocks in these films, which were confirmed to be caused by Ru oxidation. Therefore, an annealing process of the Ru electrode was added for its planarization, and the CVD process was also improved. As a result, we obtained smooth and finely crystallized ∼ 20-nm-thick BST films with good electrical properties of equivalent SiO2 thickness (teq) ∼ 0.45 nm and leakage current < 1 × 10−7 A/cm2. We also measured properties of BST films deposited on the 3-D Ru electrode. The results are briefly discussed.

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Pulsed Laser Deposition of BaxSr1−xTiO3 Films on MgO, LaAlO3 and SrTiO3 for Tunable Microwave Applications

MRS Proceedings ◽

10.1557/proc-541-693 ◽

1998 ◽

Vol 541 ◽

Cited By ~ 5

Author(s):

Wontae Chang ◽

James S. Horwitz ◽

Won-Jeong Kim ◽

Jeffrey M. Pond ◽

Steven W. Kirchoefer ◽

...

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Electric Field ◽

Pulsed Laser Deposition ◽

Pulsed Laser ◽

Dielectric Constants ◽

Laser Deposition ◽

Film Stress ◽

Donor Acceptor ◽

Bst Films

AbstractSingle phase BaxSr1−xTiO3 (BST) films (∼0.5-7 μm thick) have been deposited onto single crystal substrates (MgO, LaAlO3, SrTiO3) by pulsed laser deposition. Silver interdigitated electrodes were deposited on top of the ferroelectric film. The room temperature capacitance and dielectric Q (1/tanδ) of the film have been measured as a function of electric field (≤80 kV/cm) at 1 - 20 GHz. The dielectric properties of the film are observed to strongly depend on substrate type and post-deposition processing. After annealing (≤1000° C), it was observed that the dielectric constant and % tuning decreased and the dielectric Q increased for films deposited onto MgO, and the opposite effect was observed for films deposited onto LaA1O3. Presumably, this change in dielectric properties is due to the changes in film stress. Very thin (∼50 Å) amorphous BST films were successfully used as a stress-relief layer for the subsequently deposited crystalline BST (∼5000 Å) films to maximize % tuning and dielectric Q. Films have been deposited from stoichiometric targets and targets that have excess Ba and Sr. The additional Ba and Sr has been added to the target to compensate for deficiencies in Ba and Sr observed in the deposited BST (x=0.5) films. Films deposited from compensated targets have higher dielectric constants than films deposited from stoichiometric targets. Donor/acceptor dopants have also been added to the BST target (Mn, W, Fe ≤4 mol.%) to further improve the dielectric properties. The relationship between the dielectric constant, the dielectric Q, the change in dielectric constant with electric field is discussed.

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Mocvd of Polycrystalline and Epitaxial Complex Oxides by Liquid Delivery

MRS Proceedings ◽

10.1557/proc-474-21 ◽

1997 ◽

Vol 474 ◽

Cited By ~ 3

Author(s):

J. F. Roeder ◽

S. M. Bilodeau ◽

R. J. Carl ◽

T. H. Baum ◽

P. C. Van Buskirk ◽

...

Keyword(s):

Single Crystal ◽

Current Density ◽

Complex Oxides ◽

The Other ◽

Charge Storage ◽

Growth Mechanisms ◽

X Ray ◽

Unique Approach ◽

Bst Films ◽

Liquid Delivery

ABSTRACTA unique approach to MOCVD of complex oxides enables deposition of a number of materials of technological importance through the use of liquid delivery of metalorganic precursors. Methodologies for control of composition and exploration of. process space are compared for two film systems, one in a relatively mature state of development ((Ba,Sr)Ti03), the other in an early state of development (Ni-ferrite). In both cases, composition was controlled by mixing metalorganic precursors dissolved in solvents using a liquid delivery system. Films with excellent crystalline quality were deposited in both cases. Polycrystalline BST films displayed properties suitable for DRAM applications: charge storage densities > 80 fF/μm2 and leakage current density < 10−8 A/cm2 for films as thin as 15 nm. Growth mechanisms and rates were determined for the single component oxides of the ferrite films. Epitaxial NiFe204 films were deposited on MgO single crystal substrates at 650°C; x-ray rocking curves yielded FWHM values of 0.046°, commensurate with the substrate.

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Deposition of thin BST films in a multi-wafer planetary reactor

Integrated Ferroelectrics ◽

10.1080/10584580008222267 ◽

2000 ◽

Vol 30 (1-4) ◽

pp. 183-192 ◽

Cited By ~ 17

Author(s):

P. Ehrhart ◽

F. Fitsilis ◽

S. Regnery ◽

R. Waser ◽

F. Schienle ◽

...

Keyword(s):

Bst Films

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Thickness Dependence of the Domain Structure in Thin BST Films

Ferroelectrics ◽

10.1080/00150193.2015.998981 ◽

2015 ◽

Vol 477 (1) ◽

pp. 9-14

Author(s):

A. N. Kuskova ◽

O. M. Zhigalina ◽

R. V. Gainutdinov

Keyword(s):

Domain Structure ◽

Thickness Dependence ◽

Bst Films

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Termination switching of antiferromagnetic proximity effect in topological insulator

Science Advances ◽

10.1126/sciadv.aaz8463 ◽

2020 ◽

Vol 6 (33) ◽

pp. eaaz8463

Author(s):

Chao-Yao Yang ◽

Lei Pan ◽

Alexander J. Grutter ◽

Haiying Wang ◽

Xiaoyu Che ◽

...

Keyword(s):

Curie Temperature ◽

Topological Insulator ◽

Surface State ◽

Proximity Effect ◽

Surface States ◽

Double Exchange ◽

Exchange Interactions ◽

Stacking Order ◽

Bst Films ◽

Magnetic Proximity Effect

This work reports the ferromagnetism of topological insulator, (Bi,Sb)2Te3 (BST), with a Curie temperature of approximately 120 K induced by magnetic proximity effect (MPE) of an antiferromagnetic CrSe. The MPE was shown to be highly dependent on the stacking order of the heterostructure, as well as the interface symmetry: Growing CrSe on top of BST results in induced ferromagnetism, while growing BST on CrSe yielded no evidence of an MPE. Cr-termination in the former case leads to double-exchange interactions between Cr3+ surface states and Cr2+ bulk states. This Cr3+-Cr2+ exchange stabilizes the ferromagnetic order localized at the interface and magnetically polarizes the BST Sb band. In contrast, Se-termination at the CrSe/BST interface yields no detectable MPE. These results directly confirm the MPE in BST films and provide critical insights into the sensitivity of the surface state.

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