Two-dimensional nanomaterials exhibit a variety of electro-mechanical and electro-optical properties and are expected to be used in strain sensing devices, flexible energy storage devices, flexible diodes, transistors, detectors and diagnostic devices. In the past research, we are more to load the force to the direction perpendicular to the atomic surface of the two-dimensional material, to study the change of flexible devices. However, when the loading axis is parallel to the atomic plane, the effect of loading on the optical and optical-mechanical properties of layered nanomaterials has not been studied. Zhang Chao et al. studied the direct band gap semiconductor material-MoSe2 in situ using a scanning probe electrical sample rod integrated with an optical module. They contact the sample with a probe and apply a mechanical load to the sample in a specific direction to observe the photocurrent-dark current ratio of the sample. In addition, combined with high-resolution images, electron diffraction systematically analyzed the phenomena observed in the experiment. In the experiment, they mainly compared and studied the photocurrent characteristics and photocurrent spectroscopy changes of MoSe2 nanosheets under different deformation conditions: bending deformation perpendicular to the two-dimensional atomic plane (Bending deformation) and edge deformation parallel to the two-dimensional atomic plane (Edging deformation). The

study found that the bending deformation experiment will cause a stable small increase in the photocurrent, while the edge deformation effect tends to induce unstable and non-systematic photocurrent changes, but it will cause a red shift in the photocurrent spectrum. Then they combined with theoretical calculations to verify the experimental results, found that bending deformation will lead to the narrowing of the band gap, the sample from the direct band gap to the indirect band gap transition phenomenon is more and more obvious. The research results were published in Nano Letters under the title of Optomechanical Properties of MoSe2 Nanosheets as Revealed by In Situ Transmission Electron Microscopy, with ZhangChao of Queensland University of Science and Technology as the first author and corresponding author, and Dmitri V. Golberg as the co-corresponding author.

In-situ Link: https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.1c03796

Figure In this study, the PicoFemto of Zeyou Technology (ZepTools) was used.®The series of in-situ TEM photoelectricity sample rods set up an in-situ test environment.

(a) photocurrent spectroscopy test device,(b-c) schematic diagram of deformation method of sample in experiment, the author defines as "Bending deformation" and "Edging deformation"

(a-c) MoSe2 original, bending deformation in experiment, TEM images and diffraction data after load unloading,(d-e) bending and unbending state sample I-V curves and photoelectric response data. (f) The whole crystal property of the sample is well preserved in bending compression. Figure

(a-b) shows the TEM photo of the sample when "Edging deformation", and Figure C shows the diffraction spot splitting when "Edging deformation. (d-e) I-V curve under Schottky contact, and photoelectric response I-t curve

(a)Bending deformation (B) Edging deformation