Stabilnost in tvorba inverznih mej v ZnO: DFT in eksperimentalno presejanje novih dopantov, ki tvorijo inverzne meje
Oznaka in naziv projekta
Z2-50056 Stabilnost in tvorba inverznih mej v ZnO: DFT in eksperimentalno presejanje novih dopantov, ki tvorijo inverzne meje
Z2-50056 Stability and formation of Inversion Boundaries in ZnO: DFT and experimental screening for new IB-forming dopants
Logotipi ARIS in drugih sofinancerjev
Projektna skupina
Vodja projekta: dr. Vesna Ribić
Sodelujoče raziskovalne organizacije: Povezava na SICRIS
Sestava projektne skupine: Povezava na SICRIS
Vsebinski opis projekta
Vsebina raziskovalnega projekta
SLO
Predlagani projekt se ukvarja s stabilnostjo in tvorbo kemijsko induciranih domenskih sten, ki so v zadnjem času deležne velike pozornosti pri načrtovanju funkcionalnih materialov. Ker povzročijo nenadno 2D spremembo lastnosti materiala, znanih kot kvantne jame, predstavljajo idealno orodje za krojenje fizikalnih lastnosti materialov. Kot primer kemijsko induciranih domenskih sten v tem projektu smo izbrali inverzne meje (IBs) v ZnO, ki je netoksičen, cenovno ugoden polprevodnik tipa n s polarno wurtzitno strukturo, ki kaže odlično kombinacijo elektronskih in optičnih lastnosti, vključno z ustrezno strukturo prepovedanega pasu, kemično odpornostjo in termodinamično stabilnostjo, zaradi česar je prilagodljiv za vrsto aplikacij v elektroniki. IB v ZnO so kemično inducirane domenske stene, preko katerih je polarnost kristala obrnjena. V literaturi jih povezujejo z izboljšanim transportom elektronov, povečanim sipanjem fononov in povišanjem Schottkyjeve bariere, kar se odraža na optoelektronskih, piezotronskih, termoelektričnih in varistorskih lastnostih, povezujejo pa jih tudi z nepojasnjenim p–tipom prevodnosti v ZnO. Poleg vpliva na številne fizikalne lastnosti pa je bila nedvoumno dokazana tudi njihova vloga pri razvoju mikrostrukture, ki je posledica pretirane in anizotropne rasti ZnO zrn z IB. ZnO je zelo prilagodljiv modelni sistem za vgradnjo širokega nabora dopantov, ki spreminjajo elektronsko strukturo ZnO, pri čemer je znano, da nekateri od njih tvorijo kompleksne tipe IB v različnih mrežnih ravninah ali celo večplastne strukture s kombinacijo serije IB. Ključni cilj te podoktorske raziskave je torej ugotoviti mehanizme vgradnje dopantov in tvorbe IB v ZnO. Raziskovalna metodologija v okviru projekta temelji na multidisciplinarnem pristopu, ki združuje različna znanja in ravni znanstvene analize. Nastanek IB v ZnO bom proučevala z originalno zasnovano metodologijo, ki vključuje elektronsko mikroskopijo s pripadajočimi spektroskopskimi metodami za preučevanje strukture in kemije domenskih mej na atomarnem nivoju, modeliranje IB na osnovi fazne rekonstrukcije in analize opaženih struktur, strukturno relaksacijo na osnovi teorije gostotnih funkcionalov (DFT) ter kvantno kemijsko računanje osnovnih fizikalnih lastnosti na IB. Opisana metodologija bo vključevala študij vseh doslej znanih dopantov, ki tvorijo IB v ZnO, poleg tega pa je izdelan načrt za presejalno študijo celotnega periodnega sistem za identifikacijo novih dopantov, ki tvorijo IB. Nastanek IB bom preverjala z uveljavljenimi eksperimentalnimi pristopi kot je in–situ TEM, hidrotermalno oz. keramično procesiranje ter metoda z bikristali, ki jo uporabljamo za študij termodinamske stabilnosti mej med kristali v specifičnih kristalografskih orientacijah. Nosilka podoktorskega projekta je dr. Vesna Ribić. V svojem pionirskem delu o stabilnosti IB v Sb2O3–dopiranem ZnO, je s kombinacijo teoretičnih in eksperimentalnih pristopov naredila pomemben preboj v študijah domenskih sten v materialih. Njeno delo, ki vključuje kvantno kemijske izračune pri napovedovanju najstabilnejše strukture IB, je navdahnilo skupino teoretikov iz Centra za materiale v Leobnu (MCL), da so nadaljevali raziskovalni izziv in razvili inovativen teoretični pristop, ki omogoča primerjavo energij tvorbe IB z različnimi kemijskimi sestavami kar z doslej znanimi teoretičnimi pristopi ni bilo mogoče. To je privedlo do vzajemnega sodelovanja med raziskovalci da so po nekaj kritičnih preliminarnih testih metodologije pristopili k načrtovanju tega podoktorskega projekta. Kombinacija znanja obeh skupin ima potencial za ustvarjanje odmevnih znanstvenih odkritij ter razvoj inovativnih raziskovalnih metodologij in rešitev v teku predlaganega projekta.
ANG
The proposed project deals with the stability and formation of chemically induced domain walls, which recently received a lot of attention in the design of functional materials. Because they cause a sudden 2D discontinuity in bulk properties, known as quantum wells, they represent an ideal tool for tailoring the physical properties of materials. As a case study of chemically induced domain walls in this project, we choose inversion boundaries (IBs) in ZnO, which is a low cost non-toxic, n–type semiconductor with a polar wurtzite structure, that exhibits an excellent combination of electronic and optical properties, including an appropriate band-gap structure, chemical resistance, and thermodynamic stability, making it adaptable for a range of applications in electronics. IBs are chemically induced domain walls across which the crystal polarity is reversed. They have been linked to improved electron transport, increased phonon scattering, and increased height of the Schottky barrier which is reflected on optoelectronic, piezotronic, thermoelectric and varistor properties of ZnO–based materials. Further, they have been related to yet unexplained p–type conduction of ZnO, and have clearly been proven to cause anisotropic and exaggerated grain growth, which was successfully employed to control microstructure development of ZnO–based ceramics. ZnO is a highly adaptive model system for the incorporation of a wide range of dopants that change the electronic structure of ZnO, and some of these are known to produce complex types of IBs on various lattice planes or layered structures with multiple IBs. The key objective of this project will be to resolve fundamental questions related to the stability and formation of IBs in ZnO that will help to disentangle their role in collective physical properties. The first research challenge will be to identify the mechanisms of dopant incorporation and the driving force influencing IB formation. IB formation will be studied by an originally devised methodology that involves theoretical approaches based on DFT, structural design, and targeted experiments to study the formation of IBs with selected dopants including in–situ and high–resolution electron microscopy with the associated spectroscopic methods to study the structure and chemistry of IBs at the atomic scale. The proposed research methodology has never been attempted before, and it represents a cutting-edge approach to studying chemically induced domain boundaries and their formation mechanisms. The second research challenge will be to identify new IB–forming dopants through screening of other elements of the periodic system for potential candidates in a high throughput study. The final challenge will be the prediction of physical properties. The principal investigator of this postdoctoral project is Dr. Vesna Ribić. With her work on the stability of IB in Sb2O3–doped ZnO, she made a significant breakthrough in the studies of domain walls in materials by combining theoretical and experimental approaches. Her pioneering work that involves quantum chemical calculations in predicting the most stable IB structure inspired a group of theoreticians at Materials Center Leoben (MCL) to follow–up on the research challenge and developed an innovative theoretical approach enabling comparison of IB formation energies across different chemistries. This led to mutual collaboration between researchers to perform a few critical tests and with confidence plot the outline for this postdoctoral project. The combined expertise of both groups has the potential to produce high-impact scientific discoveries and develop innovative research methodologies and solutions in the course of the project.
Osnovni podatki sofinanciranja so dostopni na spletni strani SICRIS.
Faze projekta in opis njihove realizacije
Cilj–1. Termodinamična stabilnost in mehanizmi nastanka IB v znanih sistemih.
Cilj–2. Presejalna DFT študija za identifikacijo novih dopantov, ki spontano tvorijo IB
Cilj–3. Teoretična napoved vloge IB na fizikalne lastnosti ZnO.
Bibliografske reference
[1] E. Guilmeau et al., Inversion boundaries and phonon scat.., Inorg. Chem. 56/1 (2017) 480-487. [2] J.B. Labégorre et al., .. electron doping ..,ACS Appl. Mater. Interfaces 10/7 (2018) 6415-6423. [3] P. Keil et al., Piezotronic tuning of potential barriers in ZnO, Adv. Mater. 30/10 (2018) 1705573. [4] A.B. Yankovich et al., Stable p-type conduction from Sb-.., Nano Lett. 12/3 (2012) 1311-1316. [5] S. Bernik, Inversion boundary induced grain growth.., J. Eur. Ceram Soc. 24 (2004) 3703–3708. [6] A.P. Goldstein et al., Zigzag inversion domain .., ACS Nano 7/12 (2013) 10747-10751. [7] V. Ribić et al., TEM and DFT study of basal-plane, Sci. Sinter. 53/2 (2021) 237-252. [8] A. Rečnik et al., Structure and chemistry .., J. Am. Ceram. Soc. 84/11 (2001) 2657-2668. [9] V. Ribić et al., New inversion boundary structure .., Acta Materialia 199 (2020) 633-648. [10] D. Scheiber et al, Understanding and controlling IBs in ZnO, Acta Mater. 229 (2022) 117804.