Van der Waals epitaxy of CdTe on 2D materials

Published : 15 July 2019

2D materials nowadays attract a great amount of research because of their unique properties directly derived from their graphene-like electronic structure and crystalline organization. These materials have strong in-plane chemical bounds while extremely weak, van der Waals type, out-of-plane interaction describing them a 2D sheets of monolayer material. 2D material epitaxy on conventional 3D semiconductors may thus occur without any lattice parameter mismatch strain. The opposite is also true when depositing a 3D onto a 2D. The PhD work consists in studying in details these new epitaxial systems with the proposal of realizing the strain free epitaxial growth of photovoltaics CdTe or infrared sensitive HgCdTe on 2D layers. These materials (2D and 3D) will be grown by molecular beam epitaxy allowing for an in-situ control of the interface. The growth mode of 3D(CdTe)/2D and 2D/3D(HgCdTe) will be first independently studied with the goal of providing a full 3D(CdTe)/2D/3D(HgCdTe) heterostructure where the 3D(CdTe) will promote, through the very thin 2D, the crystalline structure and orientation for the ultimate growth of HgCdTe. Inserting a weakly bonded 2D material also offer promising new functions by enabling the HgCdTe layer to be detached and transferred onto another substrate opening the way towards new optoelectronic applications. The thesis scientific environment will be brought to a broader range by considering the availability and proximity of the nano-characterization platform (CEA-PFNC) where skilled teams and last generation of equipment are dedicated to revealing the chemical nature and crystallographic structure of the epitaxial stacks.

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