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Physics Seminar

Kinetics of GaAs (001) surfaces by combining Low Energy Electron Microscopy and Molecular Beam Epitaxy

Speaker: Dr Juan Pereiro (Cardiff University)
Date: Friday 20 November 2020
Time: 11:00 in UK
Venue: Zoom

In this talk I will describe our efforts to combine Low Energy Electron Microscopy (LEEM) and Molecular Beam Epitaxy (MBE) of III-As, and I will demonstrate how LEEM-MBE can provide new information about kinetic mechanisms of (In,Ga)As epitaxy. LEEM enable us to observe the surface of the sample in real time with 5 nm resolution in x/y plane and atomic resolution in z-axis. LEEM contrast provides information about local changes in diffraction conditions and dynamics of atomic steps. Therefore, LEEM enable us to obtain real-time imaging of kinetics of surface phases, changes in strain fields or changes of surface chemical potential of the different elements throughout the sample’s surface [1].

In our recent experiments we have imaged the formation of new terraces on the GaAs(001) surface and develop a technique that combines droplet epitaxy and LEEM to provide a full image of the surface phase diagram of GaAs (001). Our results shed light on the stability of the controversial 6x6 phase on GaAs (001) surfaces which is shown to be metastable during Langmuir evaporation, but can be stable over a narrow range of chemical potential under As flux [2,3]. We show that real-time imaging at growth conditions can be used as feedback to translate formation energy from T-0K to growth temperatures in density- functional theory calculations (Figure 1). Our recent results demonstrate that LEEM-MBE can help provide the missing pieces in the understanding fully epitaxial processes.

[1] E. Bauer, Rep. Prog. Phys. 57, 895 (1994) [2] K. Hannikainen et al. 123, 186102 (2019) [3] C.X. Zheng et al. 3, 124603 (2019) [4] A. Ohtake, Surf. Sci. Rep. 63, 295 (2008).