A Facile and Deterministic Transfer Method for 2D van der Waals Heterostructures in Quantum Devices

• Alexander Hutchinson, Physics, University of Delaware

• Chitraleema Chakraborty, Physics and Astronomy, Materials Science and Engineering, University of Delaware

Two-dimensional (2D) materials exhibit interesting properties primarily due to their structure. In 2D materials, atomic layers are held together with other atomic layers by van der Waals forces. These van der Waals forces are weaker than ionic or covalent bonds, so that in 2D materials, it is much easier to separate atomic layers than within traditional three-dimensional materials. Using this property, different 2D materials can be combined by transferring the layer of one 2D material onto the layer of a different type of 2D material. These structures or devices are oftentimes referred to as heterostructures and have interesting electronic properties, notably tunable band gaps. In order to create these heterostructures, it is important to develop a precise transfer method in which 2D-flakes can be cleanly and efficiently transferred from one surface to another.  In this study, a custom transfer method was developed in order to improve the ease and precision of 2D material transfer. In principle, this is a dry transfer technique in which a 2D material is picked up by a polymer, polydimethylsiloxane (PDMS), stamp. The PDMS stamp is then used to transfer the 2D material onto another surface. In this study, transfer onto several different surfaces was conducted. These surfaces included silicon dioxide (SiO2) substrates, electrodes of varying heights (36nm, 70nm, 100nm), and etched nanopillar structures on SiO2 substrates. Using the transfer method described, transfer onto each surface was successful and no residue from the PDMS stamp could be seen on any surface when examined under optical microscopy.