PhD - Leuven | More than two weeks ago
Data storage has increased tremendously in the internet era and there is no sign of slowing down this evolution. This requires ever larger densities in memory technology in order to keep data center dimensions and power consumption within certain limits.
3D NAND has proven to be the main workhorse for this evolution as the highest density nonvolatile solid-state memory known today. However, scaling limits are approaching rapidly and the quest for new technologies that work at substantially lower power is getting more and more attention. One very promising concept is the use of ferroelectric polarization as a means of storing information in a nonvolatile way with -so far- the lowest possible energy consumption per bit. The information can be stored in ferroelectric FETs, in ferroelectric capacitors or in ferroelectric tunnel junctions. However, the quest for such a material that can be integrated in silicon is still ongoing: perovskites were found to be less compatible with CMOS and therefore abandoned for high density memories, while the more recently discovered Hafnia are suffering from a highly defective structure containing different phases in a polycrystalline configuration, leading to reliability and variability issues.
Therefore, a very basic question arises: can we find a ferroelectric material that can be processed in a monocrystalline manner while not having the drawbacks from the perovskites such as very high dielectric constant and low bandgap? There are some studies showing that such material may exist in the Wurtzite family (e.g. MgS, AlN...) but they may require tuning to get the desired properties by doping, matching with the proper electrodes etc. If such a material can be realized, a rectangular hysteresis loop could be well achieved as we get more ‘coherent’ switching behavior. That would make a very efficient memory device as the separation between read and write condition (which is needed for disturb-free operation) can be optimal without compromising the low voltage and low power capability which is inherent to the ferroelectric switching mechanism.
This would also require a better understanding of the physics of ferroelectrics, as we approach the extreme case of ‘single dipole switching’.
The purpose of this project is to study the concept of single grain ferroelectricity from theoretical point of view as well as from experiments on new ferroelectric materials provided from the ferroelectric research program at imec. Collaboration with the materials characterization and modeling teams will be required to be successful.
Required background: master’s in physics, or nanoscience and nanotechnology
Type of work: 25% literature, 25% theoretical study, 50% experimental work
Supervisor: Valeri Afanasiev
Co-supervisor: Jan Van Houdt
Daily advisor: Jasper Bizindavyi
The reference code for this position is 2021-017. Mention this reference code on your application form.