Formation of Ferroelectricity in Hafnium Oxide Based Thin Films (eBook)

Tony Schenk (Autor)

eBook Download: PDF

2017 | 1. Auflage
192 Seiten
Books on Demand (Verlag)
978-3-7448-4166-5 (ISBN)

Infos

In 2011, Böscke et al. reported the unexpected discovery of ferroelectric properties in hafnia based thin films, which has since initiated many further studies and revitalized research on the topic of ferroelectric memories. In spite of many efforts, the unveiling of the fundamentals behind this surprising discovery has proven rather challenging. In this work, the originally claimed Pca21 phase is experimentally proven to be the root of the ferroelectric properties and the nature of this ferroelectricity is classified in the frame of existing concepts of ferroelectric materials. Parameters to stabilize this polar phase are examined from a theoretical and fabrication point of view. With these very basic questions addressed, the application relevant electric field cycling behavior is studied. The results of first-order reversal curves, impedance spectroscopy, scanning transmission electron microscopy and piezoresponse force microscopy significantly advance the understanding of structural mechanisms underlying wake-up, fatigue and the novel phenomenon of split-up/merging of transient current peaks. The impact of field cycling behavior on applications like ferroelectric memories is highlighted and routes to optimize it are derived. These findings help to pave the road for a successful commercialization of hafnia based ferroelectrics.

Tony Schenk received his B.Eng. degree in Microtechnology (dual) and M.Eng. degree in Nano- and Surface Technology from the Westsaxon University of Applied Sciences Zwickau in 2011 and 2012, respectively. He joined NaMLab in 2012 to work on hafnia/zirconia based ferroelectrics. Within the frame of these activities, he authored and co-authored more than 20 peer-reviewed articles and received his doctoral degree from TU Dresden in 2016.

Inhalt

Title Page 3
Copyright 4
Abstract 5
Autorenreferat 5
Acknowledgements 6
Table of Contents 9
1 Motivation 11
2 Fundamentals of Ferroelectricity and Ferroelectric Memories 13
2.1 Ferroelectricity from the Electrical and Structural Point of View 13
2.2 Phenomenological Theory of Ferroelectricity and Phase Transitions 17
2.3 Preisach Model of Ferroelectric Hystereses 21
2.4 Assessment of Non-ideal Ferroelectric Hystereses 22
2.5 Non-volatile Random Access Memory and Ferroelectric Memory 32
2.6 Hafnium Oxide for Ferroelectric Memories 38
3 Sample Preparation and Characterization Methods 41
3.1 Fabrication of Metal-Insulator-Metal Capacitors 41
3.2 Basic Methods 43
3.3 Scanning Probe Microscopy 46
3.4 Transmission Electron Microscopy 52
3.5 Impedance Spectroscopy 56
3.6 First-Order Reversal Curves (FORC) 60
3.7 Harmonic Analysis 62
4 Stabilization of the Ferroelectric Phase in Hafnium Oxide 65
4.1 Previous Work and Simulation Results 65
4.2 Proof of the Ferroelectric Phase 72
4.3 Impact of Smaller and Larger Dopants 75
4.4 Influence of Film Thickness and Annealing Conditions 86
4.5 Electrode Effects 89
4.6 Texture of the Ferroelectric Thin Films 92
4.7 HfO(sub[2])—An Incipient Ferroelectric? 97
4.8 Summary 99
5 Electric Field Cycling Behavior of Ferroelectric Capacitors 101
5.1 Wake-up Effect 102
5.2 Polarization Fatigue 106
5.3 Split-up and Merging of Switching Peaks in Transient Currents 109
5.4 Discussion of Activation Energies 114
5.5 PFM to Study Switching on Nanoscale 119
5.6 Structural Evolution During Field Cycling 127
5.7 Routes to Improve the Field Cycling Behavior 137
5.8 Summary 138
6 Summary and Conclusion 140
Bibliography 142
A Appendix: Dopant Overview from J. Müller’s Dissertation 167
Figures 171
Tables 181
Abbreviations 182
Symbols 184
Curriculum Vitae 189
List of Scientific Publications 191

Produkt-Details

• Erscheint lt. Verlag: 10.4.2017
• Sprache: englisch
• Themenwelt: Technik
• ISBN-10: 3-7448-4166-9 / 3744841669
• ISBN-13: 978-3-7448-4166-5 / 9783744841665