Atomically flat and thermally stable graphene on Si(111) with preserved intrinsic electronic properties

Ultrasensitive Biochemical Sensing Platform Enabled by Directly Grown Graphene on Insulator

To fabricate label-free and rapid-resulting semiconducting biosensor devices incorporating graphene, it is pertinent to directly grow uniform graphene films on technologically important dielectric and semiconducting substrates. However, it has long been intuitively believed that the nonideal disordered structures formed during direct growth, and the resulted inferior electrical properties will inevitably lead to deteriorated sensing performance. Here, graphene biosensor chips are constructed based on direct plasma-enhanced chemical vapor deposition (PECVD) grown graphene on a 4-inch silicon wafer with excellent film uniformity and high yield. To surprise, optimal operations of graphene biosensors permit ultrasensitive detection of SARS-CoV-2 virus nucleocapsid protein with dilutions down to sub-femtomolar concentrations. Such impressive limit of detection (LOD) is comparable to or even outperforms that of the state-of-the-art biosensor devices based on high-quality graphene. Further noise spectral characterizations and analysis confirms that the LOD is limited by molecular diffusion and/or known interference signals such as drift and instability of the sensors, rather than the electrical merits of the graphene devices along. Hence, result sheds light on processing directly grown PECVD graphene into high-performance sensor devices with important economic benefits and social significance.

Engineering Metal-spxy Dirac Bands on the Oxidized SiC Surface

The ability to construct 2D systems, beyond materials' natural formation, enriches the search and control capability of new phenomena, for instance, the synthesis of topological lattices of vacancies on metal surfaces through scanning tunneling microscopy. In the present study, we demonstrate that metal atoms encaged in a silicate adlayer on silicon carbide is an interesting platform for lattice design, providing a ground to experimentally construct tight-binding models on an insulating substrate. Based on the density functional theory, we have characterized the energetic and electronic properties of 2D metal lattices embedded in the silica adlayer. We show that the characteristic band structures of those lattices are ruled by surface states induced by the metal-s orbitals coupled by the host-p_xy states, giving rise to sp_xy Dirac bands neatly lying within the energy gap of the semiconductor substrate.