Semicondutor nanostructures and dedicated magneto-optical methodologies
Prof. Efrat Lifshitz’ group is among the poineers who initiated an exciting revolution in the synthesis of nanoscaled semiconductor materials. The group has developed and utilized complex magneto-optical methodologies, resulting in a tremendous contribution to the study of tailor-made physical properties of nano-scaled materials. Prof. Lifshitz’s program has developed progressively from two-dimensional materials, such as layered semiconductors and their intercalation compounds, to one-dimensional and zero-dimensional materials, including colloidal quantum dots, cubes, wires, rods, ribbons and multi-pods (see Figure 1).
The low dimensional materials represent a class of luminescent chromophores with quantized electronic states, and tunable intense optical transitions that vary with the material’s size, shape and composition. During the past decade, the Lifshitz’s group has focused on the development of nanostructures with optical activity in the UV, visible near infrared spectral regime. The group is well known for the contribution in the preparation of core/shell hetetrostructures with alloyed composition at the interface. The latter endows the materials with a unique photochemical stability, overcoming well known obstacles such as spectral instabilities (so-called fluorescence blinking). The materials developed exhibit potential as active components in telecommunication, gain devices, display devices, photodetectors, optical switches and filters, spintronics, and biological tagging. The following sections outline briefly the development of materials (past and current), methodologies, applications and theoretical models.
Materials: Nanostructures were produced either by colloidal chemical procedures or by vapor transport growth: (a) Colloidal quantum dots, rodes, wires, platelets of CdSe, CdTe, PbSe, PbS coated with organic ligands or by epitaxial layer of another semiconductor, known also as core-shell structures, such as PbSe/PbS, CdSe/CdS, CdTe/CdSe; (b) Colloidal nanostructures with alloyed composition, such as PbSexS1-x or PbSe/PbSexS1-x core-shell hetero-structures; (c) special efforts for the preparation of core and core/shell structures with a reduced toxicity, such as SnTe, SnTe/PbSe, InSb, In2S3; (c) Mn+2 doped core/shell nano-structures (dots, rods, nanoplatelets), placing dopants either at the core or at the shell; (d) Layered semiconductors from transition metal dichalcogenides or iodides (SnS2, PbI2, Bi2I3, In2S3) and metal phosphore-tri-chalcogenides (MPX3, M=Mn, Fe, Ni, Mg, Cd); (e) Chemically prepared Perovskites dot, rods and platelets; (f) Spray prepared nanostructures; (g), Metallic/magnetic nanostructures (g-Fe2O3); and their complex structures with CQDs; (h) Ordered or disordered packing of nanostructures, or dispersion with extremely high dilution for the isolation of a single particle.
Applications: Variety of materials were implemented for various applications in collaboration with industry or academic institude to form, eye-safe lasers, solar cells, up-conversion and biological tags.
Methodologies: Prof. Lifshitz’s group developed notable expertise in several distinctive methodologies combining magnetic resonance, cyclotron resonance, magnetic polarization, microwave absorption and optical spectroscopy, supplying information not revealed by conventional techniques, such as angular momentum of electronic states, g-factors, exchange interaction, Zeeman interaction, diamagnetic shift, crystal field and Rashba effects, all possessing considerable importance in understanding the physical properties of nano-scaled materials. These methodologies include the following: (a) Optically detected magnetic resonance (ODMR); (b) Microwave and thermal modulated photoluminescence; (c) Optically detected cyclotron resonance; (d) Circular polarized photoluminescence in the presence
of an external magnetic field; (e) Magneto-optical confocal microscopy, when detecting the photoluminescence of isolated single nanostructure
under the influence of an external magnetic field; (f) Atomic force microscopy combined with confocal microscopy for the manipulation and detection of a single nanostructure; (g) Confocal microscopy combined with magnetic resonance measurement at the excited state (viz, optically detected magentic resonance of an isolated single nanostructure). Experimental set-up or/and representative results are depicted in Figure 2.
Theory: The electronic band structure calculations of core and core/shell quantum dot and rods were calculated, using an effective mass approximation method. A distinct treatment beyond state-of-the-art was included, considering strain effects, their relaxation by a soft boundary and graded composition around core/shell interface, finite external barrier and dielectric confinement. Later, Coulomb interactions, exchange interactions, cross section for absorption and complex Auger processes, (in collaboration with Prof. A. Efros, USA), spin alignment and polarization effect were calculated and compared with experimental results. Another study included electrical conductivity in double quantum dots, emphasizing the influence of the inter-dot distance created by the capping ligands and their influence on the connectivity properties, showing exceptional phenomena such as induced recoil or negative resistance induced by application of charge or voltage (in collaboration with Prof. U. Peskin, Technion, Israel). Most recent study, focuses on the influence of spin-obrit coupling and symmetry breaking forming the Rashba effect, which induced electronic band split and the generation of polarized transitions (in collaboration with Prof. Andrew Rappe, Pennsylvania University). The theoretical tools are implemented now a days in various current projects under consideration.
Post Doc: University of Michigan and at the Weizmann Institute of Science, 1985-1989
Ph.D: University of Michigan, USA, 1984
B.Sc: Hebrew University in Jerusalem, 1979
Selective list (recent years): Lectureship speaker, Birkent University, Ankara, Turkey, (2018); The 2016 Israel Vacuum Society Excellence Award for Research (2016); Lectureship speaker, ETH, Switzerland, (2016); UK-Israel Lectureship Award, Oxford University (2015); Tenne Family Prize in Memory of Lea Tenne for Nanoscale Sciences, awarded by the Israel Chemical Society (2015); Fellow of the Freiburg Institute of Advanced Studies, University of Freiburg (2015); Matwei Gunsbuourgh Academic Chair at the Technion (2009).
2003 – Outstanding Women in Science and Technology, Haifa Municipality.
2000 – David Ben-Aharon for Achievements in Science, Technion.
1993-1996 – Theodore and Mina Bargman Lectureship, Technion.
1. Osovsky, R. et al. Continuous-Wave Pumping of Multiexciton Bands in the Photoluminescence Spectrum of a Single CdTe-CdSe Core-Shell Colloidal Quantum Dot. Phys. Rev. Lett.102, 197401 (2009).
2. Grumbach, N., Rubin-Brusilovski, A., Maikov, G. I., Tilchin, E. Lifshitz, E. Manipulation of Carrier–Mn2+ Exchange Interaction in CdTe/CdSe Colloidal Quantum Dots by Controlled Positioning of Mn2+ Impurities. J. Phys. Chem. C117, 21021–21027 (2013).
3. Tilchin, J. et al. Quantum Confinement Regimes in CdTe Nanocrystals Probed by Single Dot Spectroscopy: From Strong Confinement to the Bulk Limit. ACS Nano 9, 7840–7845 (2015).
4. Lifshitz, E., Evidence in Support of Exciton to Ligand Vibrational Coupling in Colloidal Quantum Dots. J. Phys. Chem. Lett. 6 (21), 4336-4347, (2015) (Invited Perspective).
5. Tilchin, J. et al. Hydrogen-like Wannier–Mott Excitons in Single Crystal of Methylammonium Lead Bromide Perovskite. ACS Nano 10, 6363–6371 (2016).
6. Kagan, C. R.; Lifshitz, E.; Sargent, E. H.; Talapin, D. V., “Building devices from colloidal quantum dots”. Science, 353 (6302), p. 885, aac 5523-1-9 (2016).
7. Isarov, M.; Tan, L. Z.; Bodnarchuk, M. I.; Kovalenko, M. V.; Rappe, A. M.; Lifshitz, E., Rashba Effect in a Single Colloidal CsPbBr3 Perovskite Nanocrystal Detected by Magneto-Optical Measurements. Nano Lett. 17 (8), 5020-5026 (2017).
8. Jang, Y.; Shapiro, A.; Isarov, M.; Rubin-Brusilovski, A.; Safran, A.; Budniak, A. K.; Horani, F.; Dehnel, J.; Sashchiuk, A.; Lifshitz, E., Interface Control of Electronic and Optical Properties in IV-VI and II-VI Core/Shell Colloidal Quantum Dots; Chem. Commun., 53 (6), 1002-1024 (2017) (Invited Review).
9. Barak, Y.; Meir, I.; Shapiro, A.; Jang, Y.; Lifshitz, E, Fundamental Properties in Colloidal Quantum Dots. Adv. Mater. DOI: 10.1002/adma.201801442, (2018) (Invited Review).
10. Shapiro, A.; Jang, Y.; Horani, F.; Kauffmann, Y.; Lifshitz, E., Kirkendall Effect: Main Growth Mechanism for a New SnTe/PbTe/SnO2 Nano-Heterostructure. Chem. Mater. 30 (9), 3141-3149 (2018).
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