Structure and reconfiguration of epitaxial GeTe/Sb2Te3 superlattices

Jama Momand

Structure and reconfiguration of epitaxial GeTe/Sb2Te3 superlattices

Vertaalde titel van de bijdrage: Structuur en reconfiguratie van epitaxiale GeTe/Sb2Te3 superroosters

Jama Momand

Nanostructured Materials and Interfaces

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De materialen bestaande uit gemengde GeTe/Sb2Te3 legeringen vertonen opmerkelijk omschakelbare opto-elektronische eigenschappen tussen hun amorfe en kristallijne fasen. Om die reden zijn ze met succes geïmplementeerd in herschrijfbare optische DVD en Blu-Ray schijven en worden ze momenteel intensief onderzocht voor toekomstige geheugen- en fotonische toepassingen. Recentelijk werd aangetoond dat nanostructurering van deze legeringen door GeTe en Sb2Te3 in de vorm van superroosters te laten groeien de prestaties van de resulterende phase-change geheugens aanzienlijk verbetert. Ondanks deze vooruitgang waren de oorsprong van de verbetering en het gedetailleerde schakelmechanisme nog niet begrepen. Vandaar dat de focus van dit proefschrift ligt op de groei en karakterisatie van dergelijke superroosters. Met behulp van voornamelijk transmissie-elektronenmicroscopie is de gedetailleerde kristalstructuur van dergelijke multilagen geanalyseerd en uitgelegd in termen van de elektronische binding van de legeringen. Verschillende schakelmechanismen van superrooster phase-change geheugens in de literatuur werden besproken en het werd aangetoond dat ze inconsistent waren met de feitelijke structuur van de lagen. Bovendien werd aangetoond dat GeTe/Sb2Te3 superroosters een interessant platform kunnen zijn om gemengde GeTe/Sb2Te3 legeringen te bestuderen door in detail de thermische reconfiguratie ervan in kaart te brengen. In de laatste delen van het proefschrift wordt de groei van dunne lagen besproken met speciale aandacht voor de substraat-film interface. Over het algemeen werpen de resultaten licht op de structuur en het schakelmechanisme van GeTe/Sb2Te3 superrooster phase-change geheugens en illustreren paden voor de groei van vergelijkbare materialen voor ferro-elektrische, spintronische en thermo-elektrische toepassingen.

Vertaalde titel van de bijdrage	Structuur en reconfiguratie van epitaxiale GeTe/Sb2Te3 superroosters
Originele taal-2	English
Kwalificatie	Doctor of Philosophy
Toekennende instantie	Rijksuniversiteit Groningen
Begeleider(s)/adviseur	Kooi, Bart, Supervisor Palasantzas, Georgios, Supervisor
Datum van toekenning	1-dec.-2017
Plaats van publicatie	[Groningen]
Uitgever	University of Groningen
Gedrukte ISBN's	978-94-034-0189-8
Elektronische ISBN's	978-94-034-0188-1
Status	Published - 2017

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Title and ContentsFinal publisher's version, 153 KB
Chapter 1Final publisher's version, 472 KB
Chapter 2Final publisher's version, 1,57 MB
Chapter 3Final publisher's version, 770 KB
Chapter 4Final publisher's version, 1,58 MB
Chapter 5Final publisher's version, 1,66 MB
Chapter 6Final publisher's version, 1,46 MB
SummaryFinal publisher's version, 40,6 KB
SamenvattingFinal publisher's version, 46,1 KB
AcknowledgementsFinal publisher's version, 80,7 KB
Complete ThesisFinal publisher's version, 6,89 MB
PropositionsFinal publisher's version, 55,2 KB

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title = "Structure and reconfiguration of epitaxial GeTe/Sb2Te3 superlattices",

abstract = "The materials based on mixed GeTe/Sb2Te3 alloys show remarkable switchable opto-electronic properties between their amorphous and crystalline phases. They are therefore successfully implemented in rewritable optical DVD and Blu-Ray disks and are currently under intense investigation for future memory and photonic applications. Recently, it was shown that nanostructuring these alloys by growing GeTe and Sb2Te3 in the form of superlattices considerably improves the performance of the resulting phase-change memories. Despite this significant advance the origin of the improvement and the detailed switching mechanism were not clearly understood. Hence, the focus of this thesis is on the growth and characterization of such superlattices. Using particularly transmission electron microscopy the detailed crystal structure of such multilayers has been analyzed and explained in terms of the bonding nature of the alloys. Several switching mechanisms of superlattice phase-change memory in the literature were debated and shown that they were inconsistent with the actual structure of the films. In addition, it was shown that GeTe/Sb2Te3 superlattices can be an interesting platform to study mixed GeTe/Sb2Te3 alloys by illustrating in detail its thermal reconfiguration. In the final parts of the thesis the thin film growth is discussed with particular focus on engineering the substrate-film interface. In general, the results shed light on the structure and switching mechanism of GeTe/Sb2Te3 superlattice phase-change memories and pave way for growth of similar materials for ferroelectric, spintronic and thermoelectric applications.",

author = "Jama Momand",

year = "2017",

language = "English",

isbn = "978-94-034-0189-8",

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AU - Momand, Jama

PY - 2017

Y1 - 2017

N2 - The materials based on mixed GeTe/Sb2Te3 alloys show remarkable switchable opto-electronic properties between their amorphous and crystalline phases. They are therefore successfully implemented in rewritable optical DVD and Blu-Ray disks and are currently under intense investigation for future memory and photonic applications. Recently, it was shown that nanostructuring these alloys by growing GeTe and Sb2Te3 in the form of superlattices considerably improves the performance of the resulting phase-change memories. Despite this significant advance the origin of the improvement and the detailed switching mechanism were not clearly understood. Hence, the focus of this thesis is on the growth and characterization of such superlattices. Using particularly transmission electron microscopy the detailed crystal structure of such multilayers has been analyzed and explained in terms of the bonding nature of the alloys. Several switching mechanisms of superlattice phase-change memory in the literature were debated and shown that they were inconsistent with the actual structure of the films. In addition, it was shown that GeTe/Sb2Te3 superlattices can be an interesting platform to study mixed GeTe/Sb2Te3 alloys by illustrating in detail its thermal reconfiguration. In the final parts of the thesis the thin film growth is discussed with particular focus on engineering the substrate-film interface. In general, the results shed light on the structure and switching mechanism of GeTe/Sb2Te3 superlattice phase-change memories and pave way for growth of similar materials for ferroelectric, spintronic and thermoelectric applications.

AB - The materials based on mixed GeTe/Sb2Te3 alloys show remarkable switchable opto-electronic properties between their amorphous and crystalline phases. They are therefore successfully implemented in rewritable optical DVD and Blu-Ray disks and are currently under intense investigation for future memory and photonic applications. Recently, it was shown that nanostructuring these alloys by growing GeTe and Sb2Te3 in the form of superlattices considerably improves the performance of the resulting phase-change memories. Despite this significant advance the origin of the improvement and the detailed switching mechanism were not clearly understood. Hence, the focus of this thesis is on the growth and characterization of such superlattices. Using particularly transmission electron microscopy the detailed crystal structure of such multilayers has been analyzed and explained in terms of the bonding nature of the alloys. Several switching mechanisms of superlattice phase-change memory in the literature were debated and shown that they were inconsistent with the actual structure of the films. In addition, it was shown that GeTe/Sb2Te3 superlattices can be an interesting platform to study mixed GeTe/Sb2Te3 alloys by illustrating in detail its thermal reconfiguration. In the final parts of the thesis the thin film growth is discussed with particular focus on engineering the substrate-film interface. In general, the results shed light on the structure and switching mechanism of GeTe/Sb2Te3 superlattice phase-change memories and pave way for growth of similar materials for ferroelectric, spintronic and thermoelectric applications.

M3 - Thesis fully internal (DIV)

SN - 978-94-034-0189-8

PB - University of Groningen

CY - [Groningen]

ER -

Structure and reconfiguration of epitaxial GeTe/Sb2Te3 superlattices

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