CONTROLUL PROPRIETATILOR ELECTRONICE IN HETEROSTRUCTURI BAZATE PE PEROVSKITI FEROELECTRICI: DE LA TEORIE LA APLICATII


Project Director: Dr. Lucian Pintilie

ID-ul Proiectului: PN-III-P4-ID-PCCF-2016-0047 (contract PCCF nr. 16 din 2018)

Director de Proiect: Dr. Lucian Pintilie

Tipul proiectului: National

Programul de incadrare al proiectului: Programul 4 - Cercetare fundamentala si de frontiera: Proiecte de Complexe de Cercetare de Frontiera

Finantare: Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii - UEFISCDI

Contractor: INSTITUTUL NATIONAL DE CERCETARE - DEZVOLTARE PENTRU FIZICA MATERIALELOR

Status: In progress

Data de inceput: 10 octombrie 2018

Data finalizarii: 9 octombrie 2022

Rezumatul Proiectului:

Obiectivul principal al proiectului este de a obtine materiale feroelectrice cu proprietati electronice controlabile la acelasi nivel la care aceastea sunt controlate in Si. Acest lucru va fi realizat prin dopaje heterovalente, corelate cu inginerie de stres mecanic si de banda interzisa, si fara a afecta, pe cat posibil, proprietatile feroelectrice. Obiectivul proiectului este complex si ambitios, intrucat pana in prezent nu a fost demonstrate posibilitatea de a obtine conductie de tip n si/sau p in feroelectrici epitaxiali. Atingerea cu succes a obiectivului va permite deschiderea unui nou domeniu, acela de electronica feroelectrica sau ferotronica, prin realizarea de dispozitive electronice de tip homodioada p-n sau transistor cu jonctiuni folosind materiale feroelectrice. Doua tipuri de materiale sunt avute in vedere, si anume titano-zirconatul de plumb (PZT) cu structura tetragonala si amestecul de ferita de bismut (BFO) cu cromat de bismut (BCO). In primul caz se vor realiza dopaje heterovalente pe pozitii Pb sau Zr/Ti cu scopul de obtine conductie de tip n si p. Scopul final este obtinerea unei homo-jonctiuni p-n pe baza de PZT epitaxial. In al doilea caz se va incerca modificarea benzii interzise prin varierea raportului Fe/Cr precum si identificarea tipului dominant de conductie, scopul fiind de a utiliza materialul in aplicatii fotovoltaice. Activitatea va contine: studii teoretice privind relatia intre dopanti, proprietatile electronice si cele feroelectrice, incluzand efecte de auto-dopaj sau de dopaj electrostatic, activitati de preparare a tintelior ceramice masive pentru depunere de straturi subtiri, activitati de crestere epitaxiala a structurilor, precum si activitati de caracterizare complexa a structurii si proprietatilor. Se are in vedere nu numai dopajul clasic in tinta ci si dopajul controlat in timpul depunerii epitaxiale. Consortiul este constituit din 4 echipe de cercetatori de la 3 institutii diferite, incluzand un numar de 14 tineri FTE.

Obiective specifice:

O1. Dopajul controlat al straturilor subtiri feroelectrice. In prima faza se va incerca obtinerea de straturi subtiri pure, depuse din tinte ceramice de puritate cat mai mare. In faza a doua se vor obtine straturi dopate din tinte dopate controlat. Intentia este de a obtine o homojonctiune p-n feroelectrica.

O2. Proiectarea si realizarea de celule de memorie FeRAM cu citire nedistructiva. Se vor testa citiri capacitive, conductive si piroelectrice.

O3. Proiectarea si realizarea de celule de memorie FeRAM cu stari multiple (multibit). Se va incerca obtinerea de structuri cu stari multiple de polarizare.

O4. Noi arhitecturi pentru generatia urmatoare de celule solare. Se va incerca obtinerea de straturi subtiri feroelectrice cu proprietati fotovoltaice, precum si integrarea feroelectricilor in celule solare perovskit.

Proiectul va fi realizat de un consortiu compus din: coordonator (CO-INCDFM, depuneri straturi, masuratori electrice, caracterizare dispozitive) partener 1 (P1-INCDFM, analize structurale si chimice folosind TEM si XPS), partener 2 (P2-INCDTIM, teorie), partener 3 (P#-UPB, realizare tinte ceramice).

Activitatile sunt grupate in 6 pachete de lucru (WP):

WP1. Teorie. CO si P2 vor colabora pentru modelarea teoretice a dopajelor in feroelectrici.

WP2. Prepararea tintelor. CO si P3 vor colabora pentru realizarea tintelor nedopate si dopate.

WP3. Cresterea straturilor fereoelectrice epitaxiale. CO va depune straturile feroelectrice epitaxiale prin PLD.

WP4. Caracterizarea structurala si chimica a straturilor epitaxial. CO si P1 vor colabora pentri caracterizarea structurala si chimia prin tehnici XRD, TEM, XPS.

WP5. Caracterizarea electrica a straturilor epitaxiale si a dispozitivelor ferotronice. CO va investiga proprietatile fizice ale straturilor epitaxiale prin masuratori electrice complexe si va caracteriza dispozitivele ferotronice pentru aplicatii de memorie si fotovoltaice.

WP6. Management, diseminare, patentare. Activitati de raportare, publicare, patentare.

Schema care arata relatia dintre cele 6 WP.

Nr. Crt.InstitutionName and link to brainmapScientific rank in Romanian research hierarchyRole in the project
1INCDFM-COLucian Pintilie

https://www.brainmap.ro/lucian-pintilie

Scientific Researcher rank IProject Director
2INCDFM-P1Teodorescu Cristian-Mihail

https://www.brainmap.ro/cristian-mihail-teodorescu

Scientific Researcher rank IResponsible P1
3INCDTIM-P2Liviu Zarbo

https://www.brainmap.ro/liviu-zarbo

Scientific Researcher rank IResponsible P2
4UPB-P3Adelina Carmen Ianculescu

https://www.brainmap.ro/adelina-carmen-ianculescu

University ProfessorResponsible P3
5INCDFM-COCristina Chirila

https://www.brainmap.ro/cristina-chirila

Scientific Researcher rank IIIPost Doc
6INCDFM-COBoni Andra Georgia

https://www.brainmap.ro/andra-georgia-boni

Scientific Researcher rank IIIPost Doc
7INCDFM-COLuminita Hrib

https://www.brainmap.ro/luminita-mirela-hrib

Scientific Researcher rank IIIPost Doc
8INCDFM-CORoxana Radu

https://www.brainmap.ro/roxana-radu

Scientific Researcher rank IIIPost Doc
9INCDFM-COIoana Pintilie

https://www.brainmap.ro/ioana-pintilie

Scientific Researcher rank IExperienced Researcher
10INCDFM-COIuliana Pasuk

https://www.brainmap.ro/iuliana-pasuk

Scientific Researcher rank IIIExperienced Researcher
11INCDFM-COLucian Trupina

https://www.brainmap.ro/lucian-trupina

Scientific Researcher rank IIIExperienced Researcher
12INCDFM-COViorica Stancu

https://www.brainmap.ro/viorica-stancu

Scientific Researcher rank IIIExperienced Researcher
13INCDFM-COAndrei Tomulescu

https://www.brainmap.ro/andrei-gabriel-tomulescu

Assistant ResearcherPhD student
14INCDFM-COCristina Besleaga

https://www.brainmap.ro/cristina-besleaga-stan

Scientific Researcher rank IIIPost Doc
15INCDFM-COGalca Catalin Aurelian

https://www.brainmap.ro/aurelian-catalin-galca

Scientific Researcher rank IExperienced Researcher
16INCDFM-COGeorge Stan

https://www.brainmap.ro/george-stan

Scientific Researcher rank IExperienced Researcher
17INCDFM-COLiliana Balescu

https://www.brainmap.ro/liliana-marinela-balescu

Scientific ResearcherPost Doc
18INCDFM-CORusu Dorin

https://www.brainmap.ro/dorin-rusu

Master studentMaster student
19INCDFM-CODaniela Dogaru

https://www.brainmap.ro/daniela-maria-dogaru

Master studentMaster student
20INCDFM-P1Nicoleta Georgiana Apostol

https://www.brainmap.ro/nicoleta-georgiana-apostol

Scientific Researcher rank IIExperienced Researcher
21INCDFM-P1Tanase Liviu

https://www.brainmap.ro/liviu-cristian-tanase

Scientific ResearcherPost Doc
22INCDFM-P1Ioana Cristina Bucur

https://www.brainmap.ro/ioana-cristina-bucur

Assistant ResearcherPhD student
23INCDFM-CONeculai Plugaru

https://www.brainmap.ro/neculai-plugaru

Scientific Researcher rank IExperienced Researcher
24INCDFM-COLucian Dragos Filip

https://www.brainmap.ro/lucian-dragos-filip

Scientific Researcher rank IIExperienced Researcher
25INCDFM-P1Bocirnea Amelia-Elena

https://www.brainmap.ro/amelia-bocirnea

Assistant ResearcherPhD student
26INCDFM-P1Corneliu Ghica

https://www.brainmap.ro/corneliu-ghica

Scientific Researcher rank IExperienced Researcher
27INCDFM-P1Raluca Negrea

https://www.brainmap.ro/raluca-florentina-negrea

Scientific ResearcherPost Doc
28INCDFM-P1Andrei Cristian Kuncser

https://www.brainmap.ro/andrei-kuncser

Scientific ResearcherPost Doc
29INCDTIM-P2Sorina Garabagiu

https://www.brainmap.ro/sorina-garabagiu

Scientific Researcher rank IIPost Doc
30UPB-P3Daniela Cristina Berger

https://www.brainmap.ro/daniela-cristina-berger

University ProfessorExperienced Researcher
31UPB-P3Melinescu Alina

https://www.brainmap.ro/alina-melinescu

Associate ProfessorExperienced Researcher
32UPB-P3Mihai Eftimie

https://www.brainmap.ro/mihai-eftimie

LectorExperienced Researcher
33UPB-P3Vasile Bogdan

https://www.brainmap.ro/bogdan-stefan-vasile

Scientific Researcher rank IIIExperienced Researcher
34UPB-P3Surdu Adrian Vasile

https://www.brainmap.ro/vasile-adrian-surdu

PhD studentPhD student
35INCDFM-P1Daniela Ghica

https://www.brainmap.ro/daniela-ghica

Scientific Researcher rank IIExperienced Researcher
36INCDFM-P1Mariana Stefan

https://www.brainmap.ro/mariana-stefan

Scientific Researcher rank IIExperienced Researcher
37INCDFM-P1Stavarache Ionel

https://www.brainmap.ro/ionel-stavarache

Scientific Researcher rank IIExperienced Researcher
38INCDFM-P1Ana Maria Lapadatu

https://www.brainmap.ro/ana-maria-lepadatu

Scientific Researcher rank IIIPost Doc
39INCDFM-COTeddy Tite

https://www.brainmap.ro/teddy-tite

Scientific Researcher rank IIIExperienced Researcher
40INCDFM-P1Marius-Adrian Husanu

https://www.brainmap.ro/marius-adrian-husanu

Scientific Researcher rank IIExperienced Researcher
41INCDFM-P1Elena Laura Abramiuc

https://www.brainmap.ro/laura-abramiuc

Scientific ResearcherPost Doc
42INCDFM-P1Marian Cosmin Istrate

https://www.brainmap.ro/marian-cosmin-istrate

Assistant ResearcherPhD student
43INCDFM-P1Adela Nicolaev

https://www.brainmap.ro/adela-nicolaev

Scientific Researcher rank IIIPost Doc
44INCDFM-CORoxana Elena Patru

https://www.brainmap.ro/roxana-elena-patru

Scientific ResearcherPost Doc
45INCDFM-P1Adrian - Constantin Pena

https://www.brainmap.ro/adrian-constantin-pena

PhD studentPhD student
46INCDTIM-P2Cristian Morari

https://www.brainmap.ro/ioan-cristian-morari

Scientific Researcher rank IExperienced Researcher
47INCDTIM-P2Calin Gabriel Floare

https://www.brainmap.ro/calin-gabriel-floare

Scientific Researcher rank IIIPost Doc
48UPB-P3Roxana Doina Trusca

https://www.brainmap.ro/roxana-doina-trusca

PhD studentPhD student
49UPB-P3Catalina Stanciu

https://www.brainmap.ro/catalina-stanciu

Scientific ResearcherPost Doc
50INCDFM-P1Cristian Radu

https://www.brainmap.ro/cristian-radu

PhD studentPhD student
51UPB-P3Nicoara Adrian

https://www.brainmap.ro/adrian-ionut-nicoara

PhD studentPhD student
52INCDTIM-P2Larisa Milena Timbolmas

https://www.brainmap.ro/larisa-milena-timbolmas

PhD studentPhD student
53INCDFM-COMihaela Botea

https://www.brainmap.ro/mihaela-botea

Scientific Researcher rank IIIPost Doc
54INCDFM-COSarah Derbali

https://www.brainmap.ro/sarah-derbali

Assistant ResearcherPhD student

During the project implementation interesting results were obtained regarding the presence of negative capacitance effect in ferroelectric capacitors of PZT type.  This effect can help to reduce the power consumption in field effect transistors, including for non-volatile memories. The topic is intensively studied, with publications in prestigious journals, such as Nature. The Project Director is co-author to the article published in Nature 565, 464 (2019).s41586-018-0854-z

 

Considering the importance of the subject, research was initiated to investigate the presence of the negative capacitance effect in the samples grown in the frame of the project. The obtained results were published in Physical Review Applied.

The Project Director was the main organizer of the 6th edition of the International Workshop of Materials Physics (IWMP). Below are the first announcement and the program of IMP.

 

First Announcement

14-16 of September 2021

The National Institute of Materials Physics (NIMP) announces the organization of the 6th edition of the International Workshop of Materials Physics (IWMP). The topic for 2021 edition is dedicated to ferroelectric and multiferroic materials, with special emphasis on thin films, multilayers, super-lattices and nano-objects. Aspects related to modeling, fabrication, characterization and potential applications will be presented and discussed.

Similar to the first five editions, the 6th edition of IWMP is organized on invitation only. The aim is to attract well known researchers in the field, the final purpose being to establish new collaborations concretized in common publications, projects and exchange of personnel.

Young researchers willing to present their latest results on topics related to the main topic of the workshop are invited to submit a 2 page abstract (A4, Times New Roman 11, single spacing, 2 cm margins, including figures and references) to the organizers (pintilie@infim.ro). The best abstracts will be selected for oral presentations during the workshop.

The workshop will take place at NIMP premises located in Magurele, Romania.

 

Workshop Program

 

14 of September

 

9:00 – 9:10 Opening

9:10-9:50: Liliana Mitoseriu: Scale-dependent properties in BaTiO3 ceramics with structural instability

9:50-10:30: Antonio Casares (on-line): Multi-Modal-Correlative Microscopy (sponsor presentation, Zeiss)

10:30-11:10: Maryline Guilloux-Viry (on-line): Niobates Ferroelectric Thin Films: i/ Growth and Characterization of Perovskite and TTB Phases in the K-Na-Nb-O System; ii/ Potential of Application in High Frequency Miniature Tunable Devices

 

11:10 – 11:30 coffee break

 

11:30-12:10: Michael Springborg: Shapes (of) Matter

12:10-12:50: Ibrahim Burc Misirlioglu (on-line): Interface limited stability of ferroelectricity in thin film heterostructures: Electrostatic interactions, elasticity effects and phase coexistence

12:50-13:30: Jorge Iniguez: Optimizing steady-state negative capacitance

 

13:30 – 14:30 lunch

 

14:30-15:10: Josep Fontcuberta: Electron transport and plasmonic response of metallic oxides

15:10-15:50: Valerie Demange: Oxide nanosheets as seed layers for epitaxial growth of complex oxides

15:50-16:30: Brian Rodriguez: AFM tip-induced strain effects in BiFeO3 films: from structural phase changes to polarization switching and nanofabrication

 

16:30 – 16:45 coffee break

 

16:45-17:25: Marty Gregg (on-line): Conducting Ferroelectric Domain Walls: Fundamentals of Transport and Device Opportunities

17:25-18:05: Alexei Gruverman (on-line): Unconventional Dynamics of Domain Walls in Uniaxial Ferroelectric Lead

Germanate

 

19:15 dinner

 

15 of September

 

9:00-9:40: Marin Alexe: Incommensurate spin crystal phases in ferromagnetic and ferroelectrics

9:40-10:20: Brahim Dkhil: Playing with domains in ferroelectric polymers and hidden states in relaxors for neuromorphic computing

10:20-11:00: Gustau Catalán: Switching dynamics and “giant” electrocooling effect of antiferroelectric PbZrO3.

 

11:00 – 11:20 coffee break

 

11:20-12:00: Vincent Garcia: Controlling antiferromagnetic textures in BiFeO3 multiferroic thin films

12:00-12:40: Nathalie Jedrecy (on-line): Electro- and magneto- resistance in perovskite-based multiferroic junctions

12:40-13:20: Pavlo Zubko (on-line): Domains and lattice curvature in ferroelectric superlattices and supercrystals

 

13:20 – 14:30 lunch

 

14:30-15:10 Torsten Granzow: Anomalous photovoltaic effect in low-leakage solution-deposited BiFeO3 films: Influence of doping and substrate stress

15:10-15:50: Igor Stolichnov: Switching in HfO2-based ferroelectrics: an insight from nanoscopic analysis

15:50-16:30: Marie-Helen Chambrier:  Ferroelectric state in a α-Ln2WO6 polymorphes stabilized in thin film

 

16:30 – 16:45 coffee break

 

16:45-17:25: Gregory S. Rohrer (on-line): High Throughput Studies of Metal Oxide Water Splitting Catalysts for the Development of Structure-Property Relations

17:25: 18:05: Eric L. Altman (on-line): Coupling Elastic, Electrostatic and Magnetic Responses in Transition Metal Silicate Monolayers

 

19:15 dinner

 

16 of September

 

9:00-9:40: Nick Barrett: Interface chemistry, oxygen vacancies, charge injection and polarization stability in ferroelectric hafnia-based films for non-volatile memories

9:40-10:20: Uwe Schroeder: Stabilization of the Ferroelectric Phase in Doped Hafnium Oxide Films: Influence of Dopants and Oxygen Vacancies

10:20-11:00: Athanasios Dimoulas (on-line): Scaling of HZO ferroelectric in Ge MFS for low power FTJ

 

11:00 – 11:20 coffee break

 

11:20-12:00: Bertrand Vilquin: Nanostructuration effect on the wake-up effect of Hf0.5Zr0.5O2 capacitor

12:00-12:20: Cristian Mihail Teodorescu: Charge accumulation, conduction band filling and ferroicity

12:20-12:40: Georgia Boni: Dynamic dielectric characterization of ferroelectric capacitors- Evidencing negative capacitance

12:40-13:00: Leontin Padurariu: Dynamic Finite Element Method for describing complex dielectric properties in ferroelectric-based composites

13:00-13:20: Marius Husanu: Ferroelectricity and rhombohedral distortion in the electronic band structure of strained PbZrTiO3

 

13:20 – 14:30 lunch

Group photo with the participants to 6th edition of IWMP.

Final Report 2022

Scientific Report Phase 2, 2019

Report Phase 3, 2020

Report Phase 4, 2021

Important results 

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 180domain 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.  

Important results 2020

The effect of negative capacitance (NC) was evidenced in PZT epitaxial capacitors (Phys. Rev. Applied 14, 014080 (2020)). NC occurs during polarization switching, being accompanied by a large increase of the current flowing through the capacitor.

 

Fig. 2 a) the opening of the polarization hysteresis loop as the amplitude of the triangular voltage pulse is gradually increased (the red arrow mark the increase); b) the C-V characteristics derived from the hysteresis loops presented in fig. 2a. The arrows mark the increase and decrease of negative capacitance observed for voltages corresponding to the domains marked in fig. 2a).

Fig. 3 a) current hysteresis recorded during the hysteresis measurements (associated to hysteresis loops presented in fig. 2a); b) the voltage dependence of the maximum value of negative capacitance in the positive voltage range (see also the arrows in fig. 2a), together with the voltage dependence of the current recorded at maximum applied voltage during the hysteresis measurement.

It was proposed that, in high quality epitaxial PZT films, the polarizations switching may have place without formation of domains with opposite orientation of polarization, as suggested by the Figure below.

Fig. 4 a) the poling map; b) the voltage variation while the PFM tip scanned the line in Figure 4 a)-it starts with +5.33 V, then after about 0.1 µm drops to -5.33 V and starts to slowly increase to +5.33 V while the tip is moving on the surface of the sample, after which drop again to -5.33 V for about 0.1 µm and suddenly change to +5.33 V for the final 0.1 µm; c) the phase contrast after applying the poling map from Figure 4 a); the phase variation while the tip scans the line in Figure 4 c).

Pure target was prepared (99.99 % purity) and films were deposited both from this target and from a commercial target with 99.9 % purity. The structural and physical characterization revealed important differences: c-lattice constant is slightly larger for the film deposited from commercial target; polarization is slightly lower for the film deposited from pure target; leakage current is lower in the film deposited from pure target and the potential barrier at electrode interfaces are higher. All these differences are attributed to anion impurities that are present in the commercial target and that an affect the electronic properties but also the strain in the lattice.

TEM and SAED images of the films deposited from commercial target (upper line) and pure target (lower line)

Measured leakage current in films deposited from commercial target (line) and pure target (markers).

First attempts were made to deposit doped films. Co-deposition method was used meaning successive deposition of layers from the pure PZT target and from Nb oxide or Fe oxide targets. TEM studies revealed that co-deposition is perturbing the epitaxial growth. However, significant differences were obtained in the electrical properties.

TEM images for the Nb doped PZT by co-deposition.

An interesting results was obtained when graphene was deposited on ferroelectric PZT. The graph below shows the conductance hysteresis in graphene, produced by polarization switching (published in RSC Adv., 2020, 10, 1522).

Left-the resistance hysteresis in graphene deposited on PZT; right-schematic showing how polarization switching in PZT can produce the hysteresis in the resistance of graphene sheet.

Some important results were obtained in 2021.

First, it was shown that there is s direct link between structural quality, polarization reversal (homogeneous versus non-homogeneous) and the amplitude of the dynamic/transitory, differential negative capacitance effect. The experimental results from electric and PFM investigations point out that the switching in high quality epitaxial films is, most probably, homogeneous, with a large amplitude of the dynamic/transitory NC effect associated to polarization switching, while in polycrystalline films the switching is non-homogeneous, with weak NC effect.

TEM images of PZT films deposited by PLD on SRO/STO substrates (epitaxial quality) or by sol-gel on Pt/Si substrates (polycrystalline).

     

Electric measurements on PZT epitaxial (left) and polycrystalline films (right)

   

PFM images (topography, amplitude and phase) for epitaxial PZT (left) and polycrystalline (right) films.

A last hour result is the change of polarization orientation by changing the doping of the epitaxial PZT from n-type (Nb doping) with polarization upward to p-type (Fe doping) with polarization downward. The evidence is in the PFM phase images below.

Box-in-box poling map (a) of PZT-Nb (b), PZT-Fe (c) and undoped PZT (d). One can observe that the surface outside the boxes has the same color as the inside box for PZT-Nb and undoped PZT, meaning polarization upward in n-type PZT (undoped PZT is n-type due to oxygen vacancies). For the PZT-Fe the surface outside the boxes has the same color as the outer box, meaning polarization downward in p-type PZT (results published in Scientific Reports 12, 755 (2022)).

The electric and electronic properties of PZT-Nb and PZT-Fe are summarized in the next table.

SamplePr(μC/cm2)EC(kV/cm)Eint(kV/cm)εSΦ0 (eV)Neff (1018 cm-3)
PZT6724711.81750.15±0.0025(5-7)
PZT-Fe5113023.52250.11±0.009(6-8)
PZT-Nb7633826.52070.32±0.02(3-5)

Interesting results were further obtained in 2022, in collaboration with project partners but also in collaboration with external partners.

For example, in collaboration with researchers from Demokritos research center from Greece, we have demonstrated the presence of a metastable ferroelectric phase in very thin HZO layers (results published in COMMUNICATIONS PHYSICS 5, 178 (2022))

Structural investigation of the very thin HZO layer, demonstrating a good crystallization and the presence of the orthorhombic (O) ferroelectric phase.

Another interesting result is that ferroelectricity modulates the polaronic coupling at multiferroic interfaces. The study was performed on PZT and BTO thin films grown on LSMO substrates, and the results were recently published in COMMUNICATIONS PHYSICS 5, 209 (2022).

a High resolution high-angle annular dark-field scanning transmission electron microscopy image at the
PbZr0.2Ti0.8O3-La0.7Sr0.3MnO3 (PZT|LSMO) interface, and Ti L, Mn L and La M maps at atomic level. The black arrow indicates the first ferroelectric
unit cell (b) Theoretical Hubbard U - corrected density functional theory band structure for SrTiO3-strained pseudocubic LSMO and (insets) local
density of states integrated ± 0.2 eV around the Г and A bands bottom. (c) Calculated Fermi surface (FS) for strained LSMO. d, e In-plane FS maps for
respectively bare LSMO and BaTiO3 (BTO) interface, LSMO|BTO in the ГMX planes recorded with hv = 643 eV. f, g In-plane FS maps for respectively
bare LSMO and BaTiO3 (BTO) interface, BTO|LSMO in the XZAR.plane recorded with hv = 708 eV. h Experimental out-of-plane FS maps for the BTO|
LSMO heterostructure in the XYMR and ΓXxXz planes. Colored frames enclosing the out-of-plane FSs encode the probed planes with the corresponding
colors from (c).

Table showing modulation of carrier concentration due to ferroelectricity.

There are also other interesting results which were not published yet. For example, it was found that the I-V characteristic of a ferroelectric p-n homojunction based on tetragonal PZT is quasi-linear, suggesting a resistive like behavior (see the graph below for a p-n homojunction with equal thicknesses of the component layers, of 100 nm). n-type conduction was obtained by doping with Nb, while p-type conduction was obtained by doping with Fe.

This behavior was explained assuming that the total current flowing through the ferroelectric p-n homojunctions is formed by summing the electron and hole currents injected at the electrode interfaces:

These results were presented for the first time at the international conference E-MRS Fall Meeting, held in Warsaw.

At present the PI is working on a new model for polarization switching in displacive ferroelectrics, based on the hypothesis that the switching is completely homogeneous, flip-flop type, and is triggered by the charge injection at electrode interfaces (invited presentations at E-MRS Spring Meeting and AMSE 2022, both presentations were on-line).

The hypothesis is base on the observation that the increasing part of the current peak recorded during polarization switching has a quasi-linear dependence on the applied voltage, therefore a conductance/resistance can be estimated from the slope of the I-V representation. This has voltage, frequency and temperature dependence, as shown in the above graphs.

The equation for the current density in the case of a Schottky injection influenced by the bulk mobility of the injected carriers suggests that the exponent can be negligible for high polarization values, low values of the dielectric constant, and large values of the applied voltage. In this case, when the exponential term is negligible (close to unity), the current density has an ohmic like form, as observed experimentally.

A sketch showing how the injected chares can trigger the polarization switching, just because they destabilize the previous charges involved in the compensation of the depolarization field.

The Project Director is Professor (associated) to the Doctoral School of Physics of the University of Bucharest.

Currently he has 4 PhD students, 2 of them being in the team of the project.

The Responsible of P1 is also Professor (associated) to the Doctoral School of Physics of the University of Bucharest.

He has 2 PhD students in the team.

The Responsible of P3 is Professor at University Politechnica Bucharest and has 2 PhD students in the team.

Updated list of publications

Nr.Titlu, jurnal, etc.AutoriIFAIS
1Memcomputing and Nondestructive Reading in Functional Ferroelectric

Heterostructures

PHYSICAL REVIEW APPLIED 12, 024053 (2019)

DOI 10.1103/PhysRevApplied.12.024053

WOS:000482588400002

ISSN 2331-7019

Georgia A. Boni, Lucian D. Filip ,* Cristina Chirila, Alin Iuga, Iuliana Pasuk, Luminita Hrib,

Lucian Trupina, Ioana Pintilie, and Lucian Pintilie

4.5321.832
2Polarization branches and optimization calculation strategy applied to ABO(3) ferroelectrics

MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING   27(4), 045008 (2019)

DOI 10.1088/1361-651X/ab146e

WOS:000464723100002

ISSN 0965-0393

Filip, Lucian D.; Plugaru, Neculai; Pintilie, Lucian1.8260.672
3Low value for the static background

dielectric constant in epitaxial PZT

thin films

SCIENTIFIC REPORTS 9, 14698 (2019) https://doi.org/10.1038/s41598-019-51312-8

WOS:000489701600034

ISSN 2045-2322

Georgia Andra Boni, Cristina Florentina Chirila, Luminita Hrib, Raluca Negrea,

Lucian Dragos Filip, Ioana Pintilie & Lucian Pintilie

4.0111.286
4Designing functional ferroelectric interfaces from first-principles: Dipoles and band bending at oxide heterojunctions

NEW J. PHYS. 21, 113005 (2019)

https://doi.org/10.1088/1367-2630/ab4d8b

WOS:000494826200005

ISSN 1367-2630

Rusu, Dorin; Filip, Lucian; Pintilie, L; Butler, Keith; Plugaru, Neculai 3.7831.489
5Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO3

PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS 13(7), 1900077 (2019)

DOI 10.1002/pssr.201900077

WOS:000477671800008

ISSN 1862-6254

Popescu, Dana Georgeta; Husanu, Marius Adrian; Chirila, Cristina; Pintilie, Lucian; Teodorescu, Cristian Mihail3.7290.790
6The interplay of work function and polarization state at the Schottky barriers height for Cu/BaTiO3 interface

APPLIED SURFACE SCIENCE

502, 144101 (2020)

DOI 10.1016/j.apsusc.2019.144101

WOS:000498639000070

ISSN 0169-4332

D.G. Popescu1,, M.A. Husanu1, C. Chirila1, L. Pintilie1 and C.M. Teodorescu15.1550.671
7(Ba,Sr)TiO3 solid solutions sintered from sol-gel derived powders: An insight into the composition and temperature dependent dielectric behavior

CERAMICS INTERNATIONAL

46(4), pp. 4180-4190 (2020)

DOI 10.1016/j.ceramint.2019.10.136

WOS:000512219600018

ISSN 0272-8842

Roxana Elena Patru1, Constantin Paul Ganea1, Catalina-Andreea Stanciu2, Vasile-Adrian Surdu2, Roxana Trusca2, Adelina-Carmen Ianculescu2*, Ioana Pintilie1*, Lucian Pintilie1

 

3.4500.454
8Polarization Switching and Negative Capacitance in Epitaxial PbZr0.2Ti0.8O3

Thin Films

PHYSICAL REVIEW APPLIED 14, 014080 (2020)

DOI 10.1103/PhysRevApplied.14.014080

WOS:000553429500002

ISSN 2331-7019

Lucian Pintilie, Georgia Andra Boni, Cristina Chirila, Luminita Hrib,

Lucian Trupina, Lucian Dragos Filip, and Ioana Pintilie

4.1941.649
9Resistance hysteresis correlated with synchrotron radiation surface studies in atomic sp2 layers of carbon synthesized on ferroelectric (001) lead zirconate titanate in an ultrahigh vacuum

RSC Adv. 10, 1522 (2020)

DOI 10.1039/c9ra09131a

WOS:000507296300035

eISSN 2046-2069

Nicoleta Georgiana Apostol, Daniel Lizzit, George Adrian Lungu,

Paolo Lacovig, Cristina Florentina Chiril˘a, Lucian Pintilie, Silvano Lizzit

and Cristian Mihai Teodorescu

3.1190.516
10Energy storage performance of ferroelectric ZrO2 film capacitors: effect of HfO2:Al2O3 dielectric insert layer,

JOURNAL OF MATERIALS CHEMISTRY A 8, 14171–14177 (2020).

DOI: 10.1039/d0ta04984k

WOS:000551538000029

ISSN 2050-7488

J. P. B. Silva*, J. M. B. Silva, K. C. Sekhar*, H. Palneedi*, M. C. Istrate, R. F. Negrea, C. Ghica, A. Chahboun, M. Pereira and M. J. M. Gomes,11.3011.999
11Polarization-dependent magnetism of the Ni/BaTiO3 interface,

PHYSICAL REVIEW MATERIALS 4, 034402 (11 pp.) (2020).

DOI: 10.1103/PhysRevMaterials.4.034402

WOS:000517972500002

ISSN 2475-9953

A. E. Bocirnea, D. G. Popescu*, C. Chirila, R. M. Costescu, V. Kuncser, V. Stancu, L. Trupina, I. Pasuk, A. M. Vlaicu, M. A. Husanu and C. M. Teodorescu3.3371.154
12Effect of strain and stoichiometry on the ferroelectric and pyroelectric properties of the epitaxial Pb(Zr0.2Ti0.8)O3 films deposited on Si wafers

MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS 266, 115042 (2021)

https://doi.org/10.1016/j.mseb.2021.115042

WOS:000621174300004

ISSN 0921-5107

C. Chirila, G. A. Boni, L. D. Filip, M. A. Husanu, S. Neatu, C. Istrate, L. G. Le Rhun, B. Vilquin, L. Trupina, I. Pasuk, M. Botea, I. Pintilie, L. Pintilie4.7060.605
13Negative capacitance in epitaxial ferroelectric capacitors evidenced by dynamic dielectric characterization

MATERIALS TODAY COMMUNICATIONS 26, 102076 (2021)

https://doi.org/10.1016/j.mtcomm.2021.102076

WOS:000635374100004

eISSN 2352-4928

G. A. Boni, C. F. Chirila, L. D. Filip, I. Pintilie, L. Pintilie2.6780
14The role of interface defect states in n and p-type Ge Metal-Ferroelectric-Semiconductor structures with Hf0.5Zr0.5O2 ferroelectric

PHYSICA STATUS SOLIDI A: APPLICATIONS AND MATERIALS SCIENCE 218, 2000500 (2021)

https://doi.org/10.1002/pssa.202000500

WOS:000605180400001

ISSN 1862-6300

Georgia A. Boni, Cosmin M. Istrate, Christina Zacharaki, Polychronis Tsipas, Stefanos Chaitoglou, Evangelos K. Evangelou, Athanasios Dimoulas, Ioana Pintilie, Lucian Pintilie1.7590.471
15Ferroelectricity in thin films driven by charges accumulated at interfaces

PHYSICAL CHEMISTRY CHEMICAL PHYSIC 23, 4085-4093 (2021)

https://doi.org/10.1039/D0CP05617K

WOS:000621595300004

ISSN 1463-9076

C. M. Teodorescu3.4300.854
16Accidental Impurities in Epitaxial Pb(Zr0.2Ti0.8)O-3 Thin Films Grown by Pulsed Laser Deposition and Their Impact on the Macroscopic Electric Properties

NANOMATERIALS 11, 1177 (2021)

DOI 10.3390/nano11051177

WOS:000657014200001

eISSN 2079-4991

Georgia Andra Boni, Cristina Florentina Chirila, Viorica Stancu, Luminita Amarande, Iuliana Pasuk, Lucian Trupina, Cosmin Marian Istrate, Cristian Radu, Andrei Tomulescu, Stefan Neatu, Ioana Pintilie, Lucian Pintilie4.3240.671
17Electro-active properties of nanostructured films of cytosine and guanine nucleobases

NANOTECHNOLOGY 32, 415702 (2021) https://doi.org/10.1088/1361-6528/ac10e4

WOS:000675211200001

ISSN 0957-4484

 

Marcela Socol, Lucian Trupina, Aurelian-Catalin Galca, Cristina Chirila, George E. Stan, Aurel-Mihai Vlaicu, Anda Elena Stanciu, Andra Georgia Boni, Mihaela Botea, Anca Stanculescu, Lucian Pintilie, Bogdana Borca3.5510.706
18Nd-doped ZnO films grown on c-cut sapphire by pulsed-electron beam deposition under oblique incidence

APPLIED SURFACE SCIENCE 563, 150287 (8 pp.) (2021).

DOI: 10.1016/j.apsusc.2021.150287

WOS: 000691459900003

ISSN 0169-4332

M. Nistor, E. Millon, C. Cachoncinlle, C. Ghica, C. Hebert, and J. Perriere6.7070.873
19Band-order anomaly at the gamma-Al2O3/SrTiO3 interface drives the electron-mobility boost

ACS Nano 15, 4347–4356 (2021).

DOI10.1021/acsnano.0c07609

WOS: 000634569100054

ISSN 1936-0851

A. Chikina, D. V. Christensen, V. Borisov, M. A. Husanu, Y. Z. Chen, X. Q. Wang, T. Schmitt, M. Radovic, N. Nagaosa, A. S. Mishchenko, R. Valenti, N. Pryds, and V. N. Strocov15.8813.681
20Homogeneous versus Inhomogeneous Polarization Switching in PZT Thin Films: Impact of the Structural Quality and Correlation to the Negative Capacitance Effect

NANOMATERIALS  11, 2124 (2021).

https://doi.org/10.3390/nano11082124

WOS:000690109600001

eISSN 2079-4991

Lucian Pintilie, Georgia Andra Boni, Cristina Florentina Chirila, Viorica Stancu, Lucian Trupina,

Cosmin Marian Istrate, Cristian Radu and Ioana Pintilie

5.0760.756
21New solid forms of the diuretic compound 4-Chloro Salicylic Acid-5-Sulfonamide

JOURNAL OF MOLECULAR STRUCTURE 1241, 130682 (2021).

https://doi.org/10.1016/j.molstruc.2021.130682

WOS:000670212600013

ISSN 0022-2860

Turza A., Miclaus O. M, Zarbo L., David M., Kacso I., Borodi G.3.1960.293
22Controlling polarization direction in epitaxial Pb(Zr0.2Ti0.8)O3 films through Nb (n-type) and Fe (p-type) doping

SCIENTIFIC REPORTS 12, 755 (2022)

https://doi.org/10.1038/s41598-022-04802-1

WOS:000804787700053

ISSN 2045-2322

 

Cristina Florentina Chirila, Viorica Stancu, Georgia Andra Boni, Iuliana Pasuk, Lucian

Trupina, Lucian Dragos Filip, Cristian Radu, Ioana Pintilie, and Lucian Pintilie

4.3801.285
23Progress and perspective on different strategies to achieve wake-up-free ferroelectric hafnia and zirconia-based thin films

APPLIED MATERIALS TODAY 26, 101394 (2022)

https://doi.org/10.1016/j.apmt.2022.101394

WOS:000820423500003

ISSN 2352-9407

J.P.B. Silva, K.C. Sekhar, R.F. Negrea , J.L. MacManus-Driscoll, L. Pintilie

 

10.411.775
24Electrode dependence of polydomain stability in ferroelectric thin films

SCRIPTA MATERIALIA 213, 114589 (2022)

DOI 10.1016/j.scriptamat.2022.114589

WOS:000791227200005

ISSN 1359-6462

I. B. Misirlioglu and L. Pintilie5.6111.409
25Metastable ferroelectricity driven by depolarization fields in ultrathin Hf0.5Zr0.5O2

COMMUNICATIONS PHYSICS 5, 178 (2022)

https://doi.org/10.1038/s42005-022-00951-x

WOS:000821604300002

ISSN 2399-3650

N. Siannas, P. Tsipas, C. Zacharaki, S. Chaitoglou, L. Bégon-Lours, C. Istrate, L. Pintilie, A. Dimoulas6.3682.365
26Nanoscopic correlations from curve fitting of photoelectron spectromicroscopy data cubes of lead zirconate titanate films

Ultramicroscopy, submitted (2021).

L. E. Abramiuc, L. C. Tănase, A. Barinov, C. F. Chirilă, C. M. Teodorescu2.6890.923
27Self-consistently derived sample permittivity in stabilization of ferroelectricity due to charge accumulated at interfaces

PHYS. CHEM. CHEM. PHYS.24, 5419 (2022)

DOI: 10.1039/d1cp05222e

WOS:000755898700001

ISSN 1463-9076

C. M. Teodorescu3.6760.823
28Ferroelectricity modulates polaronic coupling at multiferroic interfaces

COMMUNICATIONS PHYSICS 5, 209 (2022)

https://doi.org/10.1038/s42005-022-00983-3

WOS:000840841900001

ISSN 2399-3650

Marius Adrian Husanu, Dana Georgeta Popescu, Federico Bisti, Luminita Mirela Hrib, Lucian Dragos Filip, Iuliana Pasuk, Raluca Negrea, Cosmin Istrate, Leonid Lev, Thorsten Schmitt, Lucian Pintilie, Andrey Mishchenko, Cristian Mihail Teodorescu and Vladimir N. Strocov6.3682.365
29Memory Window Enhancement in Antiferroelectric RAM by Hf Doping in ZrO2

IEEE ELECTRON DEVICE LETTERS 43 (9), pp.1447-1450 (2022)

DOI 10.1109/LED.2022.3189159

WOS:000845067200018

ISSN 0741-3106

Lomenzo, Patrick D.; Li, Songrui; Pintilie, LucianIstrate, Cosmin M.; Mikolajick, Thomas; Schroeder, Uwe4.8160.931
  144.06333.298

Deposition of epitaxial ferroelectric films by PLD.

Complex electrical, photovoltaic and pyroelectric characterization of ferroelectric based structures.

Development of applications, such as memory devices, field effect transistors or pyroelectric detectors.


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