Non-epitaxial multilayers of 2D materials grown by Atomic Layer Deposition
Kornelius Nielsch1
1 Leibniz Institute for Solid State and Materials Research Dresden, Germany
Atomic layer deposition is a very versatile technology for the deposition of thin films with precise thickness control on large areas, non-planar surfaces and 3D objects. The chemical reaction is surface limited, well defined and works in most cases at low temperatures (RT to 250 °C). For a number of classical van der Waals 2D materials, there have been reports on ALD of transition metal dichalcogenide (TMDC) of MoS2, SnS2, WS2 and WSe2, which also included the electronic characterization as a field effect transistor (FET).
We have fabricated by atomic layer deposition (ALD) multilayers of layered materials based on topological insulators and van der Waals materials, called ferecrystals. These ferecrystals can be tailored to exhibit unusual properties such as high electrical conductivity or low thermal conductivity or magnetic properties. A detailed study was performed on multilayers of Sb2Te3 and SbOx, which has been grown at the same temperature as single layers of Sb2Te3. The carrier mobility is very high >150 Vs2/cm2 and is even improved when the thickness of the Sb2Te3 layers is reduced and the number of SbOx layers (typically 2 nm thickness) is increased. We have also grown ferecrystals based on Sb2Te3 and Sb2Se3 with tetrahedral and orthorhombic crystal structure, respectively. The p-type hole carrier concentration of Sb2Te3 films can be enhanced through the sublayer doping of Sb2Se3. As an outlook, we will also discuss other multilayered systems of layered materials and non-layered materials and show preliminary results on the ALD growth of oxychalcogenide layers.
