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Title: Kinetics of GaAs (001) surfaces investigated by LEEM-MBE
Author: Gómez Sánchez, Daniel
ISNI:       0000 0004 9354 4129
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2019
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Understanding the physical mechanisms behind epitaxial growth of semiconductors is crucial for the comprehensive control of the interfaces and ultimately for the fabrication of state-of-the-art optimised optoelectronic devices i.e. single-photon emitters or quantum computing. The current in-situ characterisation techniques have certain limitations in analysing dynamic processes during growth. Our unique III-Vs LEEM-MBE system at Cardiff, allows us to resolve dynamical processes on III-Vs under MBE conditions i.e. nucleation of nanostructures, with atomic resolution in the vertical axis and 5 nm in the XY plane at video rate. We have developed a new technique: Selective Energy Dark-Field Low Energy Electron Microscopy (SEDFLEEM), which conjoins the advantages of Dark-Field LEEM with the accuracy of the I-V curve of diffracted spots for identification of complex structures generated at GaAs(001) surfaces. This technique provides a very useful tool for the investigation of atomic arrangements and nanostructures nucleation. Studies on the c(8⨯2) and the (6⨯6) phase reconstructions for GaAs(001) using SEDFLEEM revealed a metastable (6⨯6) within the stable c(8⨯2) regime that is present in the surface at temperatures above 570°C. Using the principles of droplet epitaxy, we have from used a Gallium droplet, to generate a monotonically decreasing Gallium chemical potential (µGA) profile over a flat trail and we have utilised SEDFLEEM to map qualitatively different phase reconstructions around liquid gallium droplets at a fixed temperature. We have also analysed the coexistence of the c(8⨯2) and the (6⨯6) for GaAs(001) between 520°C and 570°C using SEDFLEEM. These discoveries have revealed that this transition is a first order transition and the theory of transitions for monoatomic systems can be applied to complex binary systems. The implementation of this knowledge is a key point for the growth of high-purity crystalline structures and will pave the way for the development of high-technology optoelectronic devices.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics