Objectives

The main objectives are - 

(A) Growth of single layer TMD layers by using molecular beam epitaxy (MBE) in an ultra-high vacuum (UHV) environment for 2D crystals of good crystallinity. While MBE method has been proven to provide samples of better quality, we also prepare the substrate in UHV conditions on which TMD layers can be grown. For such purpose, an ideal substrate is bilayer graphene (BLG) which is prepared in-situ by thermal flashing of atomically polished silicon carbide crystal (SiC 0001) at very high temperatures (~1500 K). The principal aim is to grow single layer 2D crystals of selective TMDs that are challenging to obtain by conventional mechanical exfoliation technique as well as to prepare potential TMDs materials in forms that are not available naturally.

(B) STM measurements of single layer TMDs at 4.2 K and 0.4 K. Using STM as a local probe technique, we study the electronic ground state properties of these 2D materials at the atomic scale. Primarily, information on the local electronic density of states (DOS) can be accessed by STM hence in order to study magnetism (in TMDs) an external magnetic field is applied perpendicular to the surface to modify the electronic DOS which can be distinguished later to obtain the magnetic properties (if any) of the material.

(C) Modifying electronic DOS of TMDs by means of electrostatic gating in a transistor device structure. We aim to grow and locally probe TMDs on a device structure under the influence of a back-gated voltage bias in order to modify the electronic density of states around the fermi level (EF). Reversible tuning by back-gating allows to navigate the changes in the collective ground state properties that can be spatially mapped at atomic scale by STM.