Electron transport in ultra-thin films and ballistic electron emission microscopy. (3rd February 2017)

• Record Type: Journal Article
• Authors: Claveau, Y; Di Matteo, S; de Andres, P L; Flores, F
• Is Part Of: Journal of physics. Volume 29:Number 11(2017)
• Publication Date: 2017-02-03
• Subjects: ballistic electron emission microscopy (BEEM) -- non-equilibrium Keldysh's formalism -- Dyson's equation. Green's functions -- theory of electron transport -- ultra-thin films; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/1361-648X/aa575e
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: We have developed a calculation scheme for the elastic electron current in ultra-thin epitaxial heterostructures. Our model uses a Keldysh's non-equilibrium Green's function formalism and a layer-by-layer construction of the epitaxial film. Such an approach is appropriate to describe the current in a ballistic electron emission microscope (BEEM) where the metal base layer is ultra-thin and generalizes a previous one based on a decimation technique appropriated for thick slabs. This formalism allows a full quantum mechanical description of the transmission across the epitaxial heterostructure interface, including multiple scattering via the Dyson equation, which is deemed a crucial ingredient to describe interfaces of ultra-thin layers properly in the future. We introduce a theoretical formulation needed for ultra-thin layers and we compare with results obtained for thick Au(1 1 1) metal layers. An interesting effect takes place for a width of about ten layers: a BEEM current can propagate via the center of the reciprocal space ( Γ ̄ ) along the Au(1 1 1) direction. We associate this current to a coherent interference finite-width effect that cannot be found using a decimation technique. Finally, we have tested the validity of the handy semiclassical formalism to describe the BEEM current.