Webinar

Investigating the phase changes in conductive polymers and ferroelectric oxides by in-situ biasing TEM

Session 1

Date: Wednesday, August 19 2020
Time: 9 AM Central European Summer Time (CEST) | 3 PM China Standard Time (CST)

Session 2

Date: Wednesday, August 19 2020
Time: 8 PM Central European Summer Time (CEST) | 11 AM Pacific Daylight Time (PDT)

This webinar will be given 2 times. Choose the time slot that best suits you.

Important: click ‘Show in My Time Zone’ on the registration page for your local time.

Abstract:

With recent advances in in-situ biasing holder chip designs and fast cameras it is now possible to analyse the dynamics of electronic materials and devices down in real time. In this talk, in-situ biasing is used to study two types of electronic materials:

1. Highly conductive polymers: Flexible electronics has been a field of intense research focus for the diverse and new class of applications not achievable by wafer-based electronics. [1-4] Polymers that are both conductive and stretchable have been put forward as a promising candidate for these device platforms. Due to the often amorphous nature of these material platforms the failure analysis knowledge gained in more traditional devices cannot be applied. The progression and innovation of flexible nanoelectronic manufacturing is dependent on understanding the fundamental physics governing the electronic breakdown of such materials and how to avoid this. In this study we investigate the highly conductive flexible amorphous 2D PEDOT [5-7] layers formed via liquid-liquid interface growth, Figure 1 (a). Utilising aberration corrected TEM and new fast camera technology we study the phase change from amorphous to crystalline at the atomic resolution by in-situ biasing.

In this study the use of high signal to noise aberration corrected imaging at a high frame rate and low sample drift provided by in-situ TEM MEMS chips made it possible to observe the formation of nucleation clusters and subsequent crystal growth mechanism during electrical breakdown, Figure 2. 4k X 4k TEM imaging at 12 frames per second was used with a ramp rate of 0.001 V per step to capture the nucleation and crystal growth pathway for the first time of conducting polymer crystal degradation. Several experiments were repeated to investigate the relationship between the density, size and twinning defects of the crystals formed with changing ramp of applied voltage.

2. Conducting domain walls in ferroelectrics is an emerging research focus in nano-electronics. [8-9] Previously overlooked, these walls have recently been reported to possess diverse functional characteristics that are completely different from the domains that they delineate.[10-12] They can have their own distinct chemistry and magnetic behaviour and in turn represent a completely new sheet phase. The characteristics of these confined regions are believed to have the same exotic functional behaviours as seen in 2D materials such as graphene, opening up a plethora of possible electronic applications. In addition, the walls have the unique property of being ‘agile’; they can be created or destroyed and even be controllably moved by an external field. However, this is an area of research at its very early stages, with a great deal of the fundamental physics still unknown. Since the region of interest (the domain wall) is atomically thin and dynamic, it is essential for the physical characterization to be at this scale and be time-resolved.

The mobility of these walls was investigated utilising the electric field applied by the STEM probe itself. A detailed analysis of the effect on the wall mobility by the applied electric field direction and electron dose was studied. To complement this, the investigation was done at various kVs and also in scanning electron microscopy (SEM) mode. We detail how the STEM probe can be utilised as a highly controlled applied electric field and not just as the source of imaging for investigating ferroelectric domain walls. We then compared the movement of the domain walls by the STEM probe electric field to the electric field applied by an in-situ TEM biasing holder. We also investigated the injection of the domain walls by in-situ heating. The lower dose and parallel beam allowed by transmission electron microscopy imaging avoided the movement of the walls due to the STEM probe and focus on the movement due to the in-situ heating and biasing.

Our results show in situ electron microscopy provide a new platform for understanding the fundamentals of ferroelectric material domain phase change and thus DW injection and movement. These new insights needed the resolution allowed by STEM/TEM due to the 2D nature of the walls.

refs:

[1] Lin, Zhaoyang, Y. H., Nature Electronics 2.9 (2019) 378-388.
[2] Caironi, M., & Yong-Young N., Large area and flexible electronics. John Wiley & Sons, 2015.
[3] Salvatore, G. A., et al. Nature communications 5.1 (2014) 1-8.
[4] Liu, Y., Matt P., & Giovanni, A. S., ACS nano 11.10 (2017): 9614-9635.
[5] Ni, D., et al. Journal of Materials Chemistry A 7.3 (2019) 1323-1333.
[6] Fan, Xi, et al. Advanced Science 6.19 (2019): 1900813.
[7] Lu, B., et al. Nature communications 10.1 (2019): 1-10.
[8] Li, Jing, et al. “In situ transmission electron microscopy for energy applications.” Joule 3.1 (2019): 4-8.
[9] Catalan, G et al. , Domain Wall Nanoelectronics. Rev. Mod. Phys 84 (2012), p. 119.
[10] McQuaid, R et al. , Nature Communications 8 (2017).
[11]Jiang, J et al. , Nature Materials 17 (17) (2017), p. 49.
[12]McGilly, L. J et al. , Nature Nanotechnology 10 (2015), p. 145.

Registration link: https://attendee.gotowebinar.com/rt/4526378618324541452