Procedure for Fabrication and Characterization of Van-der-Waals Heterostructures

In this work we provide a step-by-step description of the technique for manufacturing various van der Waals heterostructures. First, we discuss the procedure to obtain monolayer and few-layer flakes from layered materials, in particular from graphite and hexagonal boron nitride. Next, we consider different approaches to the assembly depending on the required final device. Further, we describe in detail the procedure for making ohmic contacts and give the parameters for plasma chemistry and metal deposition. We observe the field effect in transport measurements but a number of features – a strong shift of the charge neutral point from the zero-gate voltage, a large resistance away from the charge neutral point, and low mobility – indicate a problem with the quality of the resulting devices. Nevertheless, one of the fabricated devices demonstrates reasonable quality – the maximum mobility is estimated at 15000 cm²V^–1s^–1, the magnetic field dependences demonstrate the quantum Hall effect, which is standard for high-quality graphene. Unexpectedly, scanning electron microscope images of the resulting devices reveal a large amount of contamination on the surface of the flakes, which may explain the corresponding quality of our devices. Preliminary results of flakes cleaning with chemical compounds and thermal treatment are given.