Multifunctionality of Layered Materials

Layered materials have attracted a lot of attention due to their multifunctionality. We use the term “layered materials” to describe compounds with relatively strong chemical bonding in two dimensions (in-plane) compared to much weaker interactions in the out-of-plane direction due to interlayer distances that are much larger than typical interatomic spacings. We concentrate on the unique thermal, electrical and magnetic properties that arise from their two-dimensional connectivity. We divide the compounds into two categories. The first category includes the family of all-inorganic IV-VI semiconductors. We investigate the emerging family of Ge-chalcogenides with their rich polymorphism that can be obtained by alloying. The change in crystal structure influences the electronic band structure, which affects electrical transport properties significantly and increases the thermoelectric performance. The second category of layered compounds comprises two-dimensional organic-inorganic perovskites. We focus on their rich structural and magnetic properties. The structures of layered hybrid perovskites are flexible and compatible with a wide range of both inorganic and organic components, which together dictate the physical properties that they possess and lead to a large variety of different structures and properties. We pay particular attention to investigating the magnetic properties of layered organic-inorganic perovskites. This thesis shows that layered materials possess many functionalities for which the structure and physical properties are highly correlated. By studying only a few selected layered materials, we demonstrate that this research area is vast, and that many unique properties can be found only in materials with two-dimensional chemical connectivit