CONTROL OF ELECTRONIC PROPERTIES IN FERROELECTRIC PEROVSKITE HETEROSTRUCTURES: FROM THEORY TO APPLICATIONS
Project Director: Dr. Lucian Pintilie
Project ID: PN-III-P4-ID-PCCF-2016-0047 (contract PCCF no. 16 from 2018)
Project Director: Dr. Lucian Pintilie
Project Type: National
Program: Program 4 – Basic and Frontier Research: Complex Projects of Frontier Research
Fundin Agency: Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii - UEFISCDI
Contractor: NATIONAL INSTITUTE OF MATERIALS PHYSICS (INSTITUTUL NATIONAL DE CERCETARE - DEZVOLTARE PENTRU FIZICA MATERIALELOR)
Status: In progress
Starting Date: 10 Octombrie 2018
Endin Date: 9 Octombrie 2022
The main objective of the project is to obtain ferroelectric materials with controlled electronic properties at the same level as these properties are controlled in Si. This will be realized by hetero-valent doping, correlated with stress engineering and band gap engineering without affecting, as much as possible, the ferroelectric properties. The main objective is complex and ambitious because, up to date, there was no experimental demonstration that it possible to obtain n or/and p type conduction in epitaxial ferroelectrics. The successful achievement of this objective will open a new domain, that of ferroelectric electronics or ferrotronics, by producing electronic devices of p-n homo-junction type or junction transistors with ferroelectric materials. Two types of materials are envisaged, namely lead titanate-zirconate (PZT with tetragonal structure and a mixed bismuth ferrite (BFO) with bismuth chromit (BCO). In the first case the heterovalent doping will be studied on Pb or Zr/Ti sites with the aim to obtain n and p type conduction. The final goal is to produce a p-n homo-junction based on epitaxial PZT films. In the second case band gap engineering will be tested by varying the Fe/Cr content, and the dominant conduction mechanism will be identified, the goal being to use the material in photovoltaic applications. The activities will contain: theoretical studies regarding the relation between dopants, electronic properties and the ferroelectricity, including self-doping effects or electrostatic doping; target preparation for deposition of thin films; epitaxial growth of the film; characterization activities of the structure and physical properties. Not only classic doping in the target is envisaged but also doping during the epitaxial growth. The consortium is composed of 4 teams from three different institutions, including a number of 14 young researchers full time equivalent.
|Teams - Institution||Vacant
|First Name||Last Name||Role in project|
|1||Team 1 - Coordinator(CO)-NIMP||NO||Lucian||Pintilie||Experienced Researcher|
|3||Coordinator(CO)||NO||Lucian Dragos||Filip||Experienced Researcher|
|5||Coordinator(CO)||NO||Andra Georgia||Boni||Postdoc Researcher|
|20||Team 2 - Partner 1(P1)-NIMP||NO||Cristian Mihail||Teodorescu||Experienced Researcher|
|21||Partner 1(P1)||NO||Nicoleta||Apostol||Postdoc Researcher|
|22||Partner 1(P1)||NO||Liviu||Tanase||PhD Student|
|23||Partner 1(P1)||NO||Ioana Cristina||Bucur||PhD Student|
|24||Partner 1(P1)||NO||Amelia||Bocirnea||PhD Student|
|25||Partner 1(P1)||NO||Corneliu||Ghica||Experienced Researcher|
|26||Partner 1(P1)||NO||Raluca||Negrea||Postdoc Researcher|
|27||Partner 1(P1)||NO||Andrei||Kuncser||PhD Student|
|28||Partner 1(P1)||NO||Daniela||Ghica||Experienced Researcher|
|29||Partner 1(P1)||NO||Mariana||Stefan||Experienced Researcher|
|30||Partner 1(P1)||NO||Ionel||Stavarache||Postdoc Researcher|
|31||Partner 1(P1)||NO||Ana Maria||Lepadatu||Postdoc Researcher|
|32||Partner 1(P1)||YES||PhD Student|
|33||Team 3 - Partner 2(P2)-NIIMT||NO||Daniel||Bilc||Experienced Researcher|
|34||Partner 2(P2)||NO||Liviu Petru||Zarbo||Experienced Researcher|
|35||Partner 2(P2)||NO||Sorina||Garabagiu||Postdoc Researcher|
|36||Partner 2(P2)||YES||PhD Student|
|37||Team 4 - Partner 3(P3)-PUB||NO||Adelina Carmen||Ianculescu||Experienced Researcher|
|38||Partner 3(P3)||NO||Daniela Cristina||Berger||Experienced Researcher|
|39||Partner 3(P3)||NO||Mihaela Alina||Melinescu||Experienced Researcher|
|40||Partner 3(P3)||NO||Mihai||Eftimie||Experienced Researcher|
|41||Partner 3(P3)||NO||Bogdan||Vasile||Experienced Researcher|
|42||Partner 3(P3)||NO||Adina Mara||Mihai||PhD Student|
|43||Partner 3(P3)||NO||Vasile Adrian||Surdu||PhD Student|
|44||Partner 3(P3)||NO||Iuliana Madalina||Stanciu||Master’s Student|
|45||Partner 3(P3)||YES||PhD Student|
Theory and modelling-effect of dopants on PTO energetic structure
Figure 1: Comparison of total DOS between the non doped PTO structure (a) and three cases of unsuccessful p-type dopant: b) Na substitution of Pb atom; c) Pb vacancy and d) Na substitution of Ti atom.
Figure 2: Total DOS comparison between the non doped PTO (top plot) and the spin polarized total DOS for the Fe substitution of Ti atom case (bottom plot). The red and blue lines represent the contribution to the DOS of the Fe atom (spin-up in red and spin-down in blue).
PZT thin films-properties
It was evidenced that the background static dielectric constant in PZT is of low value and depends on the amount of structural defects and on the magnitude of the applied electric field.
Fig. 3a) The thickness dependence of the dielectric constant evaluated from C-V measurements performed at 100 kHz. Evaluation was performed in three cases: at 0V “static”; at 0V “dynamic”; at maximum applied voltage “dynamic”; b) TEM images for 20 nm and 150 nm thick samples (inside each image the notations are a-low magnification image cross-section; b-SAED image; c-low magnification HR-TEM image; d-high magnification HR-TEM image of PZT/SRO interface and SRO/STO interfaces; these images demonstrate the high quality of the epitaxial growth).
Memcapacitance and memcomputing was demonstrated in layered ferroelectric structures
FIG. 4. Logic operation using an F-I -F capacitor. The representation of the polarization states in an F-I -F structure during different stages (initialization and computation) of a logic operation for the OR/NOR case (a) and for the AND/NAND case (b), together with the corresponding simulations of the logic operations obtained by changing the capacitance state (HCS or LCS) of the system using different combinations of pulses. The HCS and LCS states can have 0 or 1 values associated for logic operations and the results are memorized on the computation cell and can be accessed at any time.
FIG. 5. Multiple stable states with continuous capacitive values. (a) A continuous spectrum of capacitance values, with stable intermediate states measured for the STO interlayer case at 1 kHz frequency with 0.5-V ac signal; insets show schematic illustrations of polarization configurations associated with distinct capacitive states. (b) An example of a voltage sequence combining pulses with different amplitudes and polarities used to access different capacitive states. (c) The piezoresponse phase signal obtained using the poling map: the upper PZT layer present totally reverses polarization toward the surface for negative applied bias (bright central rectangular zone) while for positive bias the polarization remains partially reversed, forming with 180◦ domain structure. (d) The piezoresponse phase signal obtained by applying the poling map with a voltage gradient on the totally reversed polarization area from (c): the switching of polarization takes place gradually with increasing the amplitude of voltage; different degrees of partial switching of polarization are obtained in the 8–37 V range.
It was shown, by XPS analysis, that the compensation mechanism changes from intrinsic (with carriers generated in ferroelectric by self-doping) to extrinsic (with carriers from metal electrodes, as the electrode thickness increases.
Variation of the atomic O/Ti ratio indicating the source of oxygen vacancy (a) for the system ferroelectric/metal, with different electrode metals and polarization orientations (b). (c) the charge profile associated to oxygen vacancy density for different thicknesses of the metal layer. (d) the band bending at the interface.
|1||Memcomputing and Nondestructive Reading in Functional Ferroelectric Heterostructures PHYSICAL REVIEW APPLIED 12, 024053 (2019)||Georgia A. Boni, Lucian D. Filip ,* Cristina Chirila, Alin Iuga, Iuliana Pasuk, Luminita Hrib, Lucian Trupina, Ioana Pintilie, and Lucian Pintilie||4.532||1.832|
Polarization branches and optimization calculation strategy applied to ABO(3) ferroelectrics MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING Volume: 27 Issue: 4 Article Number: 045008 Published: JUN 2019
|Filip, Lucian D.; Plugaru, Neculai;Pintilie, Lucian||1.826||0.672|
Low value for the static background dielectric constant in epitaxial PZT thin films Scientific Reports | (2019) 9:14698 | https://doi.org/10.1038/s41598-019-51312-8
|Georgia Andra Boni, Cristina F lorentina Chirila, Luminita Hrib, Raluca Negrea, Lucian Dragos Filip, Ioana Pintilie & Lucian Pintilie||4.011||1.286|
Designing functional ferroelectric interfaces from first-principles: Dipoles and band bending at oxide heterojunctions New Journal of Physics (accepted)
|Rusu, Dorin; Filip, Lucian; Pintilie, L; Butler, Keith; Plugaru, Neculai||3.783||1.489|
Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO3 PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS Volume: 13 Issue: 7 Article Number: 1900077 Published: JUL 2019
|Popescu, Dana Georgeta; Husanu, Marius Adrian; Chirila, Cristina; Pintilie, Lucian; Teodorescu, Cristian Mihail||3.729||0.790|
The interplay of work function and polarization state at the Schottky barriers height for Cu/BaTiO3 interface Applied Surface Science, accepted
|D.G. Popescu, M.A. Husanu, C. Chirila, L. Pintilie and C.M. Teodorescu||5.155||0.671|
(Ba,Sr)TiO3 solid solutions sintered from sol-gel derived powders: An insight into the composition and temperature dependent dielectric behavior Ceramics International, accepted
|Roxana Elena Patru, Constantin Paul Ganea, Catalina-Andreea Stanciu, Vasile-Adrian Surdu, Roxana Trusca, Adelina-Carmen Ianculescu, Ioana Pintilie, Lucian Pintilie
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