Edge-contacted graphene with slope engineering by stencil lithography

One approach to overcome the high contact resistance between 3D metals and 2D materials/heterostructures is employing edge contacts [1]. A low-resistance edge contact on boron nitride/graphene/boron nitride heterostructure using photolithography has been demonstrated in 2013[1]. The aim of this project is therefore to simplify the process by replacing the photolithography step with stencil lithography. In the first part of the project, the focus is on the transferring of chemical vapor grown graphene to SiO2/Si wafers. We were able to make two graphene transfers; however, in both cases the graphene had many cracks and tears which would distort any electrical measurements. Therefore, we used these samples for experimenting with etching of HfO2 and slope engineering and showed that ion beam etching is suitable for both purposes. Later, graphene on SiO2/Si chips were purchased which were accordingly processed and used for electrical characterization. Some of the (transfer length measurement) patterns showed conductive behavior; however, the measured contact resistance was considerably high (8kΩ). Further studies are required to explain the high contact resistance observed. A good starting point would be to obtain a cross-section sample from the contact area using focused ion beam and study the said area using transmission electron microscopy.