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Bridging the electrode gap with ferroelectric thin films

Jeroen Beeckman UGent, Oliver Willekens, Xiaoning Jia UGent, John Puthenparampil George UGent and Kristiaan Neyts UGent (2016) p.I21-I21
abstract
Close to the edges of electrodes, strong electric fields are present which often give rise to unwanted effects in liquid crystal behavior. In liquid crystal microdisplays for projector applications, the gap between electrodes should be as small as possible and the liquid crystal orientation should vary sharply from one pixel to the other in order to achieve the highest possible resolution. In other applications however, a smooth variation in the liquid crystal orientation is desirable and fringe field effects are highly unwanted. Electrode based tunable lenses or beam steering devices are examples in which fringe fields should be suppressed as much as possible. A common way to alleviate the fringe field problem and to smoothen out the spatial variation of liquid crystal orientation is to deposit weakly conductive layers on top of the highly conductive electrodes. In such devices there is a trade-off between high electrical power consumption (high conductivity) and reduced smoothing effect (low conductivity). Also, it is technologically not always straightforward to obtain layers with the desired sheet conductivity. In this work, we demonstrate a new technique exploiting the extremely high dielectric permittivity of ferroelectric thin films based on lead zirconate titanate (PbZrxTi1-xO3, PZT). The high dielectric permittivity of the layer leads to similar effects as the conductivity of a weak conductor. The smoothening and spreading of the electrical field lines between two electrodes is clearly demonstrated in figure 1. At the same time we also prove the excellent reduction of fringe fields near electrode edges. Using multi-electrode designs with a PZT top layer, tunable lenses with high optical quality are demonstrated [1]. Also one-dimensional beam steering is demonstrated. In both cases a reference device was fabricated without PZT layer. The benefit of using a PZT layer is obvious when comparing the PZT and non-PZT devices. [1] O. Willekens, J.P. George, K. Neyts & J. Beeckman, Ferroelectric thin films with liquid crystal for gradient index applications, Optics Express 24, 8088-8096 (2016)
Please use this url to cite or link to this publication:
author
organization
year
type
conference
publication status
published
subject
pages
I21 - I21
conference name
6th Workshop on Liquid Crystals for Photonics
conference location
Ljubljana, Slovenia
conference start
2016-09-14
conference end
2016-09-16
language
English
UGent publication?
yes
classification
C3
copyright statement
I have retained and own the full copyright for this publication
id
8122780
handle
http://hdl.handle.net/1854/LU-8122780
date created
2016-10-20 13:58:03
date last changed
2016-12-19 15:37:47
@inproceedings{8122780,
  abstract     = {Close to the edges of electrodes, strong electric fields are present which often give rise to unwanted effects in liquid crystal behavior. In liquid crystal microdisplays for projector applications, the gap between electrodes should be as small as possible and the liquid crystal orientation should vary sharply from one pixel to the other in order to achieve the highest possible resolution. In other applications however, a smooth variation in the liquid crystal orientation is desirable and fringe field effects are highly unwanted. Electrode based tunable lenses or beam steering devices are examples in which fringe fields should be suppressed as much as possible. 
A common way to alleviate the fringe field problem and to smoothen out the spatial variation of liquid crystal orientation is to deposit weakly conductive layers on top of the highly conductive electrodes. In such devices there is a trade-off between high electrical power consumption (high conductivity) and reduced smoothing effect (low conductivity). Also, it is technologically not always straightforward to obtain layers with the desired sheet conductivity. In this work, we demonstrate a new technique exploiting the extremely high dielectric permittivity of ferroelectric thin films based on lead zirconate titanate (PbZrxTi1-xO3, PZT). The high dielectric permittivity of the layer leads to similar effects as the conductivity of a weak conductor. The smoothening and spreading of the electrical field lines between two electrodes is clearly demonstrated in figure 1. At the same time we also prove the excellent reduction of fringe fields near electrode edges. Using multi-electrode designs with a PZT top layer, tunable lenses with high optical quality are demonstrated [1]. Also one-dimensional beam steering is demonstrated. In both cases a reference device was fabricated without PZT layer. The benefit of using a PZT layer is obvious when comparing the PZT and non-PZT devices. 
[1] O. Willekens, J.P. George, K. Neyts \& J. Beeckman, Ferroelectric thin films with liquid crystal for gradient index applications, Optics Express 24, 8088-8096 (2016)},
  author       = {Beeckman, Jeroen and Willekens, Oliver and Jia, Xiaoning and Puthenparampil George, John and Neyts, Kristiaan},
  language     = {eng},
  location     = {Ljubljana, Slovenia},
  pages        = {I21--I21},
  title        = {Bridging the electrode gap with ferroelectric thin films},
  year         = {2016},
}

Chicago
Beeckman, Jeroen, Oliver Willekens, Xiaoning Jia, John Puthenparampil George, and Kristiaan Neyts. 2016. “Bridging the Electrode Gap with Ferroelectric Thin Films.” In , I21–I21.
APA
Beeckman, Jeroen, Willekens, O., Jia, X., Puthenparampil George, J., & Neyts, K. (2016). Bridging the electrode gap with ferroelectric thin films (pp. I21–I21). Presented at the 6th Workshop on Liquid Crystals for Photonics.
Vancouver
1.
Beeckman J, Willekens O, Jia X, Puthenparampil George J, Neyts K. Bridging the electrode gap with ferroelectric thin films. 2016. p. I21–I21.
MLA
Beeckman, Jeroen, Oliver Willekens, Xiaoning Jia, et al. “Bridging the Electrode Gap with Ferroelectric Thin Films.” 2016. I21–I21. Print.