Seminar "Recent advances in spectroscopic PEEM applied to low-dimensional semiconductors" by Prof. Renault

Title: “Recent advances in spectroscopic PEEM applied to low-dimensional semiconductors”

Speaker: Prof. Olivier Renault

Affiliation: Univ. Grenoble Alpes, and CEA, LETI, MINATEC Campus

Abstract:

The high lateral resolution of spectroscopic, energy-filtered PEEM combined with high energy and momentum resolutions is ideally suited for performing state-of-the-art, microscopic investigations of novel semiconducting materials with intrinsically low dimensionality. When a PEEM is combined with a high transmission imaging spectrometer and various kind of excitation sources (from monochromatic X-rays to VUV and UV light), as in the NanoESCA instrument, a high degree of versatility if reached. Systems of interest include, for instance, wide-band gap GaN wire structures for lighting and two-dimensional (2D) semiconductors such as graphene, transitions metal dichalcogenides and related 2D materials heterostructures.

In this seminal talk, we will review recent studies performed in this research field using the NanoESCA operated mainly with laboratory sources, first focusing on strongly n-doped GaN wires for lighting applications [2], before moving to the exciting field of 2D-systems: iodine doped graphene [3], MoS₂ [4, 5], MoSe₂/h-BN [6], GaSe [7]. In these examples, we will highlight, on the one hand, the necessity of getting a comprehensive set of imaging data specific of work function, surface steochiometry and chemistry, as well as band structure for a good understanding of these systems. On the other hand, we will show how rich such combined data sets can be at the quantitative level for validating growth processes [4-6] and electronic properties [2, 5-7] without the need for synchrotron radiation.

[1] M. Escher, K. Winkler, O. Renault, N. Barrett, J. Electron Spectrosc. Relat. Phenom 170-171 (2010), 303.

[2] O. Renault. J. Morin et al., Ultramicroscopy 159 (2015), 476.

[3] H. Kim, O. Renault, et al., Appl. Phys. Lett. 105, 011605 (2014); Ultramicroscopy 153 (2015), 453.

[4] M. Frégnaux, O. Renault, et al.,  Surf. Interface Anal. 48 (2015), 465.

[5] H. Kim, A. Kis, O. Renault et al., Phys. Rev. B 94, 081401(R) (2016).

[6] M. Chen, H. Kim, O. Renault, A. Kis, Nat. Phys. 2D Mater. Appl. 2017 (submitted).

[7] M. Chen, H. Kim, O. Renault, A. Kis, Nat. Comm. 2017 (submitted).