Over the past several decades, the application of transmission electron microscopy (TEM) has expanded from static characterization to in-situ observation and dynamic measurements, providing new opportunities for understanding structure-property relationships of materials. With the development of novel in situ TEM setups, it is now possible to apply external stimuli, such as heat, stress, electrical bias, and gaseous (or liquid) flow, to the sample and measure relevant properties in the limited space of the TEM holder. Dynamic structure change can be characterized through TEM imaging, electron diffraction and spectroscopy, revealing the process of interest as it happens. In-situ TEM study offers atomic-scale visualization and is therefore an essential complement to those other in-situ techniques providing averaged information over larger length scales ( e.g., in-situ X-ray diffraction, in-situ infrared spectroscopy, and in-situ X-ray photoelectron spectroscopy, etc. )
In-situ biasing test on BiFeO3 thin films
In BiFeO3, since most novel properties are derived from the polarization structures and switching behaviors of domains and domain walls, or from their coupling to other material functionalities, a fundamental understanding of the static polarization states and the dynamic processes at nanoscale is critical for the control of functional properties and the development of new applications.
The figure above shows a creation of a CDW that caused by applying a positive ramp bias using in situ TEM. A CDW can be created from a triangular domain wall junction composed of 109° and 180° domain walls that is commonly observed in the BiFeO3 films. During the switching, the shrinkage of the triangular domain led to upward motion of the triangular domain tip and resulted in the formation and elongation of a CDW (figure 30(b)). After the bias was removed, the system relaxed to a stable state, where the length of the CDW remained ~5 nm (figure 30(b)). This CDW can also be erased, with the local film reversing back to a high-resistance state. Using this effect, ultrahighdensity information storage based on CDWs may be possible.
Home-made double-tilt in situ holder with ultra-high stability
To take full advantage of the high spatial resolution of TEM and the adoption of aberration correctors, generally, a double-tilt in situ TEM holder is necessary for the collection of atomic-scale image along specific zone axes during dynamic manipulation. However, to our knowledge, the double tilting function is only realized in very few in situ TEM holders with limited probe motion and bad mechanical stability. Therefore, it was necessary and imperative to develop a double- tilt in situ TEM holder with ultra-high stability for acquiring atomic scale structure information and precision property measurements simultaneously.
-Probing system
The manipulation mechanism of the probe consists of three components for coarse, medium, and fine motion. A wide range of coarse and medium motion is realized by a “wobble stick” type mechanism. Fine motion of the probe is realized by a piezo tube mounted between the tip holder and the front end of the hollow tube.
-Unique seal-bearing components for ultra-high stability
The unique seal-bearing components endow our holder with ultra-high stability and vacuum sealing. The front seal- bearing consists of Viton o-rings and a polyether ether ketone disk with holes. The disc has internal o-ring grooves within each hole and is mounted inside the front end of the holder. With the other end of the STM component sealed in a similar fashion, the STM component is well insulated from both electric shorting and ambient environment.
-Double tilting function and optional fiber optic component
The sample stage can tilt 15 ° in both positive and negative directions, driven by a tilting rod, which is connected to a gear set for tilting angle control, sliding against the front seal-bearing.
The holder is designed to be compatible with most advanced JEOL transmission electron microscopes having a pole piece gap of at least 2.2 mm. A wide variety of in situ TEM applications including electrical measurement, lithiation reaction, STM mapping, photovoltaic, and CL spectroscopy, can be performed on this platform with high spatial resolution imaging and high electrical sensitivity at pA scale, which is not available in current commercial products.
Related publications
- Li, L., Xie, L., Pan, X.Q., Real-time Studies of Ferroelectric Domain Switching: a Review. Reports on Progress in Physics 2019 82 (12), 126502. https://doi.org/10.1088/1361-6633/ab28de
- Xu, M., Dai, S., Blum, T., Li, L., Pan, X., Double-tilt in situ TEM holder with ultra-high stability. Ultramicroscopy 2018, 192, 1-6. https://doi.org/10.1016/j.ultramic.2018.04.010
- Li, L., Zhang, Y., Xie, L., Jokisaari, J. R., Beekman, C., Yang, J. C., … Pan, X. Atomic-Scale Mechanisms of Defect-Induced Retention Failure in Ferroelectrics. Nano Letters 2017, 17(6), 3556–3562. https://doi.org/10.1021/acs.nanolett.7b00696
- Li, L., Britson, J., Jokissaari, Zhang, Y., Adamo C., Melville, A., Schlom, D.G., Chen, L.Q., Pan, X.Q., Giant Resistive Switching via Control of Ferroelectric Charged Domain Walls. Advanced Materials 2016, 28, 6574-6580. https://doi.org/10.1002/adma.201600160
- P. Gao, J. Britson, C. T. Nelson, J. R. Jokisaari, C. Duan, M. Trassin, S. H. Baek, H. Guo, L. Z. Li, Y. R. Wang, Y. H. Chu, A. M. Minor, C. B. Eom, R. Ramesh, L. Q. Chen, and X. Q. Pan, “Ferroelastic domain switching dynamics under electrical and mechanical excitations”, Nature Communications 5:3801 doi: 10.1038/ncomms4801 (2014).
- P. Gao, J. Britson, J. R. Jokisaari, C. T. Nelson, S. H. Baek, Y. R. Wang, C. B. Eom, L.-Q. Chen, and X. Q. Pan, “Atomic-scale mechanisms of ferroelastic domain-wall-mediated ferroelectric switching”, Nature Communications 4:2791 doi: 10.1038/ncomms3791 (2013).
- P. Gao, C. T. Nelson, J. R. Jokisaari, S.H. Baek, C.W. Bark, Y. Zhang, E.G. Wang, D.G. Schlom, C.B. Eom, and X.Q. Pan, “Revealing the role of defects on ferroelectric switching with atomic resolution,” Nature Communications, Vol. 2, pp. 591 (2011).
- Nelson, C.T., Gao, P., Jokisaari, J.R., Heikes, C., Adamo, C., Melville, A., Baek, S.H., Folkman, C.M., Winchester, B., Gu, Y., Liu, Y., Zhang, K., Wang, E., Li, J., Chen, L.Q., Eom, C.B., Schlom, D.G., Pan, X.Q., Domain Dynamics During Ferroelectric Switching. Science 2011, 224 (6058), 968-971. https://doi.org/10.1126/science.1206980