Spin transport in graphene - hexagonal boron nitride van der Waals heterostructures

Mallikarjuna Gurram

Spin transport in graphene - hexagonal boron nitride van der Waals heterostructures

Vertaalde titel van de bijdrage: Spintransport in grafeen - hexagonale boornitride van der Waals heterostructuren

Mallikarjuna Gurram

Fysica van Nano Devices

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De huidige micro-elektronicatechnologie gebruikt de ladingseigenschappen van een elektron voor informatieverwerking. Om de uitdagingen, zoals de vermogensdissipatie en downscaling van de elektronische apparaten te overwinnen, onderzoekt het vakgebied spintronica (spin-gebaseerde elektronica) een extra intrinsieke eigenschap van het elektron, spin genoemd, welke een puur kwantummechanische eigenschap is.

Grafeen, een één-atomige tweedimensionale laag koolstofatomen, is de laatste tien jaar ontstaan als een veelbelovend materiaal voor spintronica-toepassingen. Het onderzoek dat in dit proefschrift gepresenteerd wordt, behandelt de uitdagingen in grafeen-spintronica als gevolg van het onderliggende substraat, onzuiverheden op het oppervlak van grafeen en de kwaliteit van de ferromagnetische tunnelingcontacten. Hiervoor introduceren we een nieuwe device-geometrie waarbij grafeen volledig is ingekapseld tussen twee hexagonale boornitride (hBN) lagen.

We laten zien dat hBN een schone tunnelbarrière-grafeeninterface biedt die lange afstand-spintransport in grafeen mogelijk maakt. Verder laten we zien dat het mogelijk is om spin-injectie en detectiepolarisaties tot ± 100% te bereiken en een unieke tekeninversie van spinsignalen te maken door toepassing van een elektrisch veld over de ferromagnetische tunnelingcontacten. We hebben ook grootschalige, met chemische dampafzetting (CVD) gekweekte hBN als tunnelbarrières gebruikt en onze studie wijst op het belang van de kwaliteit en de kristallografische oriëntatie van hBN bij het bepalen van de tunnelingkenmerken.

De resultaten die gepresenteerd worden in dit proefschrift vertegenwoordigen belangrijke ontwikkelingen in het begrijpen van de aard van spintransport in grafeen en spin-injectie via hBN-barrieres. Dit inzicht zal zeker helpen bij het overwinnen van de uitdagingen bij het realiseren van praktische spintronische devices gebaseerd op grafeen-hBN-van der Waals-heterostructuren.

Vertaalde titel van de bijdrage	Spintransport in grafeen - hexagonale boornitride van der Waals heterostructuren
Originele taal-2	English
Kwalificatie	Doctor of Philosophy
Toekennende instantie	Rijksuniversiteit Groningen
Begeleider(s)/adviseur	van Wees, Bart, Supervisor Vera Marun, Ivan, Co-supervisor
Datum van toekenning	23-mrt.-2018
Plaats van publicatie	[Groningen]
Uitgever	University of Groningen
Gedrukte ISBN's	978-94-034-0543-8
Elektronische ISBN's	978-94-034-0542-1
Status	Published - 2018

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Title and contentsFinal publisher's version, 188 KB
Chapter 1Final publisher's version, 257 KB
Chapter 2Final publisher's version, 825 KB
Chapter 3Final publisher's version, 477 KB
Chapter 4Final publisher's version, 745 KB
Chapter 5Final publisher's version, 377 KB
Chapter 6Final publisher's version, 5,04 MB
Chapter 7Final publisher's version, 1,89 MB
Chapter 8Final publisher's version, 3,46 MB
AppendixFinal publisher's version, 405 KB
SummaryFinal publisher's version, 97,3 KB
SamenvattingFinal publisher's version, 98,6 KB
సారాంశాంFinal publisher's version, 130 KB
AcknowledgementsFinal publisher's version, 86 KB
PublicationsFinal publisher's version, 77,9 KB
Curriculum vitaeFinal publisher's version, 60,7 KB
Complete thesisFinal publisher's version, 11,6 MB
PropositionsFinal publisher's version, 289 KB

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Efficient spin injection into graphene through trilayer hBN tunnel barriers
Leutenantsmeyer, J. C., Ingla-Aynes, J., Gurram, M. & van Wees, B. J., 21-nov.-2018, In: Journal of Applied Physics. 124, 19, 6 blz., 194301.
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title = "Spin transport in graphene - hexagonal boron nitride van der Waals heterostructures",

abstract = "The current microelectronics technology utilizes the charge property of electron for information processing. To overcome the challenges such as the power dissipation and downscaling of the electronic devices, the field of study spintronics (spin based electronics) explores an additional intrinsic property of electron, called spin, purely a quantum mechanical property. Graphene, a one-atom thick two-dimensional layer of carbon atoms, has emerged in the last decade as a promise material for spintronics applications. The research presented in this thesis addresses the challenges in graphene spintronics due to the underlying substrate, impurities on graphene{\textquoteright}s surface and the quality of the ferromagnetic tunneling contacts. For this we introduce a new device geometry where graphene is fully encapsulated between two hexagonal boron nitride (hBN) layers. We show that hBN provides a clean tunnel barrier-graphene interface enabling long-distance spin transport in graphene. Furthermore, we show that it is possible to achieve spin-injection and detection polarizations up to ±100% and a unique sign inversion of spin signals via application of electric field across the ferromagnetic tunneling contacts. We also employed large-area chemical vapour deposition (CVD) grown hBN as tunnel barriers and our study points to the importance of the quality and the crystallographic orientation of hBN in determining the tunneling characteristics. The results presented in this thesis represent important developments towards understanding the nature of spin transport in graphene and spin injection via hBN barriers. This understanding will certainly be helpful in overcoming the challenges in realizing practical spintronic devices based on graphene-hBN van der Waals heterostructures.",

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N2 - The current microelectronics technology utilizes the charge property of electron for information processing. To overcome the challenges such as the power dissipation and downscaling of the electronic devices, the field of study spintronics (spin based electronics) explores an additional intrinsic property of electron, called spin, purely a quantum mechanical property. Graphene, a one-atom thick two-dimensional layer of carbon atoms, has emerged in the last decade as a promise material for spintronics applications. The research presented in this thesis addresses the challenges in graphene spintronics due to the underlying substrate, impurities on graphene’s surface and the quality of the ferromagnetic tunneling contacts. For this we introduce a new device geometry where graphene is fully encapsulated between two hexagonal boron nitride (hBN) layers. We show that hBN provides a clean tunnel barrier-graphene interface enabling long-distance spin transport in graphene. Furthermore, we show that it is possible to achieve spin-injection and detection polarizations up to ±100% and a unique sign inversion of spin signals via application of electric field across the ferromagnetic tunneling contacts. We also employed large-area chemical vapour deposition (CVD) grown hBN as tunnel barriers and our study points to the importance of the quality and the crystallographic orientation of hBN in determining the tunneling characteristics. The results presented in this thesis represent important developments towards understanding the nature of spin transport in graphene and spin injection via hBN barriers. This understanding will certainly be helpful in overcoming the challenges in realizing practical spintronic devices based on graphene-hBN van der Waals heterostructures.

AB - The current microelectronics technology utilizes the charge property of electron for information processing. To overcome the challenges such as the power dissipation and downscaling of the electronic devices, the field of study spintronics (spin based electronics) explores an additional intrinsic property of electron, called spin, purely a quantum mechanical property. Graphene, a one-atom thick two-dimensional layer of carbon atoms, has emerged in the last decade as a promise material for spintronics applications. The research presented in this thesis addresses the challenges in graphene spintronics due to the underlying substrate, impurities on graphene’s surface and the quality of the ferromagnetic tunneling contacts. For this we introduce a new device geometry where graphene is fully encapsulated between two hexagonal boron nitride (hBN) layers. We show that hBN provides a clean tunnel barrier-graphene interface enabling long-distance spin transport in graphene. Furthermore, we show that it is possible to achieve spin-injection and detection polarizations up to ±100% and a unique sign inversion of spin signals via application of electric field across the ferromagnetic tunneling contacts. We also employed large-area chemical vapour deposition (CVD) grown hBN as tunnel barriers and our study points to the importance of the quality and the crystallographic orientation of hBN in determining the tunneling characteristics. The results presented in this thesis represent important developments towards understanding the nature of spin transport in graphene and spin injection via hBN barriers. This understanding will certainly be helpful in overcoming the challenges in realizing practical spintronic devices based on graphene-hBN van der Waals heterostructures.

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SN - 978-94-034-0543-8

PB - University of Groningen

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Spin transport in graphene - hexagonal boron nitride van der Waals heterostructures

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Efficient spin injection into graphene through trilayer hBN tunnel barriers

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