Since the pioneering study of graphene, a lot of other two-dimensional (2D) materials have been added into the 2D family. Beyond the studies of individual 2D materials, isolated 2D crystals can be reassembled layer by layer into heterostructures. To date, different heterostructures have been studied, revealing novel optical, electronic and magnetic properties. Usually, the fabrication of 2D heterostructure is based on polymer assisted transfer methods, which employs one of the following polymers: polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), polypropylene carbonate (PPC), and polycarbonate (PC). All of these methods lead to contamination being trapped between the layers during the stacking process, such as polymer residue, water, or air. In this work, a polymer-free transfer method is developed using almost transparent SiN membranes. This technique involves no polymer, is completely dry, and works at room temperature (for heat sensitive samples) and up to at least 570K, enabling the fabrication of van der Waals heterostructures (vdWH) with large bubble free areas, exhibiting excellent electronic transport properties. In addition, by using cantilevers patterned with holes, it is possible to fabricate suspended samples in the same manner, suitable for the product of transmission electron microscopy (TEM) liquid cells containing volatile organic solvents, which would be impossible using polymers. To demonstrate the advantage of this new method, we fabricated various 2D heterostructures in different environments, including air, glovebox, ultra-high vacuum, and liquid. From the measured results in this work, the polymer-free 2D transfer technology platform enables a significant improvement in the quality of vdWH assembled in air and inert gasses. It allows the elimination of all interlayer contamination when used in a ultra-high vacuum (UHV) environment. Access to vdWHs where the performance is limited only by the intrinsic quality and dimensions of the 2D crystals is expected to lead to many new research avenues for uncovering new scientific phenomena. Furthermore, as SiN films are readily available with wafer-scale sizes, this approach provides the first potential compatibility for the industrial fabrication of bespoke vdWHs by combining chemical vapour deposition (CVD) grown 2D materials at the wafer-scale. Moreover, this new transfer technique can be used to fabricate complex organic solvent GLCs for in-situ TEM measurement, which is impossible for polymer-assisted methods.
Date of Award | 31 Dec 2022 |
---|
Original language | English |
---|
Awarding Institution | - The University of Manchester
|
---|
Supervisor | Roman Gorbachev (Supervisor) & Sarah Haigh (Supervisor) |
---|
- inorganic transfer
- heterostructures
- SiN
Inorganic assembly of van der Waals heterostructures
Wang, W. (Author). 31 Dec 2022
Student thesis: Phd