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Tuning ferroelectric response of PMN-PT capacitors via engineering of the electrode-ferroelectric interface

Project description:

Ferroelectric materials exhibit remnant polarizations that are switchable by an external electrical field. They can be used for Ferroelectric RAM (FeRAM), Ferroelectric Tunnel Junctions (FTJs), and Ferroelectric Field Electron transistors (FETs), etc.[1]. Relaxor ferroelectric material is a special type of ferroelectrics, which shows a partially disordered structure and polar nanoregions [2]. A well-known type of such material is lead magnesium niobate-lead titanate (PMN-PT). Currently, we have found out that the ferroelectric response of PMN-PT capacitors is strongly related to the electrode-ferroelectric interface. The  PMN-PT capacitors show a normal ferroelectric response when the PMN-PT is in contact with an electrode that has a lower carrier density (Figure 1 left), whereas they demonstrate a relaxor ferroelectric response when the PMN-PT is in contact with an electrode that has a high carrier density (Figure 1 right). The aim of this project is to combine the electrode materials with a high and a low carrier density, and change their thickness ratio to achieve a tunable ferroelectric response of PMN-PT capacitors. The tunable ferroelectric response can have promising applications in the adaptive processing of information and neuromorphic computing[1,3]. Moreover, the impact of the electrode-ferroelectric contact on the switching kinetics of PMN-PT needs to be studied in detail.

Possible tasks of a MSc student:

  • Epitaxial Growth of the electrode/relaxor-ferroelectric/electrode layer stack
  • Characterization of thin films crystal structure and morphology using XRD, AFM, etc.
  • Fabrication of PMN-PT capacitors using clean room facilities
  • Characterization of ferroelectric response and switching dynamics of PMN-PT capacitors using  dynamic hysteresis mood and Positive Up Negative Down (PUND) mood of the ferroelectric tester
  • Fitting the data with the existing ferroelectric switching theories (KAI, NLS, etc.)


Figure 1:  Left : polarization hysteresis loop of PMN-PT in contact with a bottom electrode with a low carrier density; Right: polarization hysteresis loop of PMN-PT in contact with a bottom in contact with a bottom electrode with a high carrier density

Contact:
Shu Ni  s.ni@utwente.nl
Gertjan Koster  g.koster@utwente.nl

[1] Garcia, Vincent, and Manuel Bibes. "Ferroelectric tunnel junctions for information storage and processing." Nature communications 5.1 (2014): 1-12.
[2] Sun, Enwei, and Wenwu Cao. "Relaxor-based ferroelectric single crystals: Growth, domain engineering, characterization and applications." Progress in materials science 65 (2014): 124-210.
[3] Ghosh, Anirban, Gertjan Koster, and Guus Rijnders. "Multistability in bistable ferroelectric materials toward adaptive applications." Advanced functional materials 26.31 (2016): 5748-5756.