1
|
Dhakar N, Zhao P, Lee HY, Kim SW, Kumar B, Kumar S. Significant Enhancement in THz Emission and Piezoelectricity in Atomically Thin Nb-Doped MoS 2. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 39176983 DOI: 10.1021/acsami.4c08011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2024]
Abstract
A significantly enhanced THz radiation generation from femtosecond photoexcited MoS2 layers due to Nb-doping is reported here. Different microscopic mechanisms involved in the THz photocurrent generation vary in their relative contributions in the two cases of photoexcitation, i.e., above and below the electronic bandgap of the layers. For a moderate Nb-doping level of just ∼0.05%, we have observed a multifold enhancement in the THz emission for the case of the above bandgap excitation, which is, though, nearly 1.5 times for the case of the below bandgap excitation of the monolayer MoS2. Alongside the difference in THz generation efficiency, the THz pulse polarity is also reversed at the above bandgap excitation of the Nb-doped layers, consequent to the reversed surface depletion field. Except for a slightly smaller difference in the THz enhancement factor, all the observations are reproducible in the bilayers as well to imply a weaker inversion symmetry and reduced screening of the surface depletion field due to Nb-doping. Furthermore, we employed pristine MoS2 and Nb-doped MoS2 monolayers to fabricate piezoelectric nanogenerator devices. Like enhancement in the ultrafast THz emission, the piezoelectric performance of the nanogenerator, fabricated with the Nb-doped MoS2 monolayer is also increased by a similar factor.
Collapse
Affiliation(s)
- Neetesh Dhakar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Pin Zhao
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hyeon Yeong Lee
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Sang-Woo Kim
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
- Center for Human-oriented Triboelectric Energy Harvesting, Yonsei University, Seoul 03722, Republic of Korea
| | - Brijesh Kumar
- Smart Materials and Photonics Laboratory, Department of Physics, University of Lucknow, Lucknow 226007, India
| | - Sunil Kumar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| |
Collapse
|
2
|
Kanistras N, Scheuer L, Anyfantis DI, Barnasas A, Torosyan G, Beigang R, Crisan O, Poulopoulos P, Papaioannou ET. Magnetic Properties and THz Emission from Co/CoO/Pt and Ni/NiO/Pt Trilayers. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:215. [PMID: 38276733 PMCID: PMC11154404 DOI: 10.3390/nano14020215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/02/2024] [Accepted: 01/12/2024] [Indexed: 01/27/2024]
Abstract
THz radiation emitted by ferromagnetic/non-magnetic bilayers is a new emergent field in ultra-fast spin physics phenomena with a lot of potential for technological applications in the terahertz (THz) region of the electromagnetic spectrum. The role of antiferromagnetic layers in the THz emission process is being heavily investigated at the moment. In this work, we fabricate trilayers in the form of Co/CoO/Pt and Ni/NiO/Pt with the aim of studying the magnetic properties and probing the role of very thin antiferromagnetic interlayers like NiO and CoO in transporting ultrafast spin current. First, we reveal the static magnetic properties of the samples by using temperature-dependent Squid magnetometry and then we quantify the dynamic properties with the help of ferromagnetic resonance spectroscopy. We show magnetization reversal that has large exchange bias values and we extract enhanced damping values for the trilayers. THz time-domain spectroscopy examines the influence of the antiferromagnetic interlayer in the THz emission, showing that the NiO interlayer in particular is able to transport spin current.
Collapse
Affiliation(s)
- Nikolaos Kanistras
- Institute of Physics, Martin Luther University Halle-Wittenberg, Von-Danckelmann Platz 3, 06120 Halle, Germany;
| | - Laura Scheuer
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, 67663 Kaiserslautern, Germany; (L.S.); (R.B.)
| | - Dimitrios I. Anyfantis
- Department of Materials Science, School of Natural Sciences, University of Patras, 26504 Patras, Greece; (D.I.A.); (A.B.); (P.P.)
| | - Alexandros Barnasas
- Department of Materials Science, School of Natural Sciences, University of Patras, 26504 Patras, Greece; (D.I.A.); (A.B.); (P.P.)
| | - Garik Torosyan
- Photonik Center Kaiserslautern, 67663 Kaiserslautern, Germany;
| | - René Beigang
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, 67663 Kaiserslautern, Germany; (L.S.); (R.B.)
| | - Ovidiu Crisan
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania;
| | - Panagiotis Poulopoulos
- Department of Materials Science, School of Natural Sciences, University of Patras, 26504 Patras, Greece; (D.I.A.); (A.B.); (P.P.)
| | - Evangelos Th. Papaioannou
- Institute of Physics, Martin Luther University Halle-Wittenberg, Von-Danckelmann Platz 3, 06120 Halle, Germany;
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania;
- Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| |
Collapse
|
3
|
Kumar S, Kumar S. Large interfacial contribution to ultrafast THz emission by inverse spin Hall effect in CoFeB/Ta heterostructure. iScience 2022; 25:104718. [PMID: 35865133 PMCID: PMC9293784 DOI: 10.1016/j.isci.2022.104718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 05/30/2022] [Accepted: 06/29/2022] [Indexed: 11/24/2022] Open
Abstract
Ultrafast THz radiation generation from ferromagnetic/nonmagnetic (FM/NM) spintronic heterostructures generally exploits the spin-charge conversion within the nonmagnetic layer and its interface with the ferromagnetic layer. Various possible sub-contributions to the underlying mechanism need to be exploited not only for investigating the intricacies at the fundamental level in the material properties themselves but also for improving their performance for broadband and high-power THz emission. Here, we report ultrafast THz emission from (CoFeB,Fe)/(Ta,Pt) bilayers at varying sample temperatures to unravel the role of intrinsic and extrinsic spin-charge conversion processes through the extracted values of spin-Hall conductivities. An enhanced THz emission along with temperature-dependent THz signal polarity reversal is observed in the case of annealed CoFeB/Ta. These results demonstrate a large interfacial contribution to the overall spin-Hall angle arising from the modified interface in the annealed CoFeB/Ta.
Collapse
Affiliation(s)
- Sandeep Kumar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Sunil Kumar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| |
Collapse
|
4
|
Agarwal P, Huang L, Ter Lim S, Singh R. Electric-field control of nonlinear THz spintronic emitters. Nat Commun 2022; 13:4072. [PMID: 35835753 PMCID: PMC9283400 DOI: 10.1038/s41467-022-31789-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 07/04/2022] [Indexed: 11/30/2022] Open
Abstract
Energy-efficient spintronic technology holds tremendous potential for the design of next-generation processors to operate at terahertz frequencies. Femtosecond photoexcitation of spintronic materials generates sub-picosecond spin currents and emission of terahertz radiation with broad bandwidth. However, terahertz spintronic emitters lack an active material platform for electric-field control. Here, we demonstrate a nonlinear electric-field control of terahertz spin current-based emitters using a single crystal piezoelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) that endows artificial magnetoelectric coupling onto a spintronic terahertz emitter and provides 270% modulation of the terahertz field at remnant magnetization. The nonlinear electric-field control of the spins occurs due to the strain-induced change in magnetic energy of the ferromagnet thin-film. Results also reveal a robust and repeatable switching of the phase of the terahertz spin current. Electric-field control of terahertz spintronic emitters with multiferroics and strain engineering offers opportunities for the on-chip realization of tunable energy-efficient spintronic-photonic integrated platforms.
Collapse
Affiliation(s)
- Piyush Agarwal
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
- Center for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore
| | - Lisen Huang
- Institute of Materials Research and Engineering A*STAR (Agency for Science, Technology and Research) 2 Fusionopolis Way, Innovis, Singapore, 138364, Singapore
| | - Sze Ter Lim
- Institute of Materials Research and Engineering A*STAR (Agency for Science, Technology and Research) 2 Fusionopolis Way, Innovis, Singapore, 138364, Singapore
| | - Ranjan Singh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.
- Center for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore.
| |
Collapse
|
5
|
Mag-usara VK, Escaño MC, Petoukhoff CE, Torosyan G, Scheuer L, Madéo J, Afalla J, Talara ML, Muldera JE, Kitahara H, Bacon DR, Nakajima M, Dani K, Papaioannou ET, Beigang R, Tani M. Optimum excitation wavelength and photon energy threshold for spintronic terahertz emission from Fe/Pt bilayer. iScience 2022; 25:104615. [PMID: 35800756 PMCID: PMC9253697 DOI: 10.1016/j.isci.2022.104615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 05/25/2022] [Accepted: 06/10/2022] [Indexed: 11/29/2022] Open
Abstract
Terahertz emission from ferromagnetic/non-magnetic spintronic heterostructures had been demonstrated as pump wavelength-independent. We report, however, the pump wavelength dependence of terahertz emission from an optimized Fe/Pt spintronic bilayer on MgO substrate. Maximum terahertz generation per total pump power was observed in the 1200- to 1800-nm pump wavelength range, and a marked decrease in the terahertz emission efficiency beyond 2500 nm (pump photon energies <0.5 eV) suggests a ∼0.35-eV threshold pump photon energy for effective spintronic terahertz emission. The inferred threshold is supported by previous theoretical results on the onset energy of significant spin-filtering at the Fe-Pt interface, and confirmed by Fe/Pt electronic structure calculations in this present work. The results of terahertz time-domain emission spectroscopy show the sensitivity of spintronic terahertz emission to both the optical absorptance of the heterostructure and the energy-dependent spin transport, as dictated by the properties of the metallic thin films. Excitation wavelength dependence of THz emission from spintronic Fe/Pt bilayer Maximum THz emission efficiency of Fe/Pt in the 1200 to 1800-nm pump wavelength range Inferred pump photon energy threshold linked to spin-filtering at the Fe-Pt interface Effect of pump absorptance and energy-dependent spin transport on Fe/Pt THz emission
Collapse
|
6
|
Vogel T, Omar A, Mansourzadeh S, Wulf F, Sabanés NM, Müller M, Seifert TS, Weigel A, Jakob G, Kläui M, Pupeza I, Kampfrath T, Saraceno CJ. Average power scaling of THz spintronic emitters efficiently cooled in reflection geometry. OPTICS EXPRESS 2022; 30:20451-20468. [PMID: 36224790 DOI: 10.1364/oe.453539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 04/06/2022] [Indexed: 06/16/2023]
Abstract
Metallic spintronic terahertz (THz) emitters have become well-established for offering ultra-broadband, gapless THz emission in a variety of excitation regimes, in combination with reliable fabrication and excellent scalability. However, so far, their potential for high-average-power excitation to reach strong THz fields at high repetition rates has not been thoroughly investigated. In this article, we explore the power scaling behavior of tri-layer spintronic emitters using an Yb-fiber excitation source, delivering an average power of 18.5 W (7 W incident on the emitter after chopping) at 400 kHz repetition rate, temporally compressed to a pulse duration of 27 fs. We confirm that a reflection geometry with back-side cooling is ideally suited for these emitters in the high-average-power excitation regime. In order to understand limiting mechanisms, we disentangle the effects on THz power generation by average power and pulse energy by varying the repetition rate of the laser. Our results show that the conversion efficiency is predominantly determined by the incident fluence in this high-average-power, high-repetition-rate excitation regime if the emitters are efficiently cooled. Using these findings, we optimize the conversion efficiency and reach highest excitation powers in the back-cooled reflection geometry. Our findings provide guidelines for scaling the power of THz radiation emitted by spintronic emitters to the milliwatt-level by using state-of-the-art femtosecond sources with multi-hundred-Watt average power to reach ultra-broadband, strong-field THz sources with high repetition rate.
Collapse
|
7
|
Scheuer L, Ruhwedel M, Karfaridis D, Vasileiadis IG, Sokoluk D, Torosyan G, Vourlias G, Dimitrakopoulos GP, Rahm M, Hillebrands B, Kehagias T, Beigang R, Papaioannou ET. THz emission from Fe/Pt spintronic emitters with L1 0-FePt alloyed interface. iScience 2022; 25:104319. [PMID: 35602944 PMCID: PMC9114522 DOI: 10.1016/j.isci.2022.104319] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 03/28/2022] [Accepted: 04/25/2022] [Indexed: 11/02/2022] Open
Abstract
Recent developments in nanomagnetism and spintronics have enabled the use of ultrafast spin physics for terahertz (THz) emission. Spintronic THz emitters, consisting of ferromagnetic (FM)/non-magnetic (NM) thin film heterostructures, have demonstrated impressive properties for the use in THz spectroscopy and have great potential in scientific and industrial applications. In this work, we focus on the impact of the FM/NM interface on the THz emission by investigating Fe/Pt bilayers with engineered interfaces. In particular, we intentionally modify the Fe/Pt interface by inserting an ordered L10-FePt alloy interlayer. Subsequently, we establish that a Fe/L10-FePt (2 nm)/Pt configuration is significantly superior to a Fe/Pt bilayer structure, regarding THz emission amplitude. The latter depends on the extent of alloying on either side of the interface. The unique trilayer structure opens new perspectives in terms of material choices for the next generation of spintronic THz emitters.
Collapse
Affiliation(s)
- Laura Scheuer
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Moritz Ruhwedel
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Dimitrios Karfaridis
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | - Isaak G Vasileiadis
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | - Dominik Sokoluk
- Fachbereich Elektro-Informationstechnik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Garik Torosyan
- Photonic Center Kaiserslautern, Kaiserslautern 67663, Germany
| | - George Vourlias
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | | | - Marco Rahm
- Fachbereich Elektro-Informationstechnik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Burkard Hillebrands
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Thomas Kehagias
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | - René Beigang
- Fachbereich Physik, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Evangelos Th Papaioannou
- Institut für Physik, Martin-Luther Universität Halle Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle, Germany
| |
Collapse
|