Thin Films and Superlattice Synthesis

Tuning the physical properties of thin films and of those emerging at the interfaces of heterostructures is an ever-growing field of research, thanks to the advances in the layer-by-layer deposition techniques that allow controlling the sample growth at the level of a single atomic layer. 

Interfacial and size effects in very thin layers have been a largely explored approach in the field of semiconductor technology [1]. A relevant example is the utilization of the difference in the bandgap at the interface between two semiconductors in order to tune the electronic energy levels and to engineer the optoelectronic properties. Extremely powerful devices can be obtained starting from binary semiconducting materials. 

Pemvskites and Related Mixed Oxides Concept and Applications, First Edition. 

Edited by Pascal Granger, Vasile I. Parvulescu, Serge Kaliaguine, and Wilfrid Prellier. 

One of the most relevant examples of new physical properties appearing at the interface of two materials is related to the interfiice reconstruction of transition metal perovskites. This is the case of LaAlOs/SrTiOs (LAO/STO) interface [9], where two-dimensional (2D) conductivity is observed at the interface between two insulating materials. The different properties are explained in terms of not only electronic reconstruction but also ion displacement, that is, polar deformations across the interface [10]. 

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Charge carriers in semiconductors can be confined in one spatial dimension (ID), two spatial dimensions (2D), or three spatial dimensions (3D). These regimes are termed quantum films, quantum wires, and quantum dots as illustrated in Fig. 9.1. Quantum films are commonly referred to as single quantum wells, multiple quantum wells or superlattices, depending on the specific number, thickness, and configuration of the thin films. These structures are produced by molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) [2j. The three-dimensional quantum dots are usually produced through the synthesis of small colloidal particles. 

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