This work is devoted to the development and optimization of the parameters of graphene-based sensors. The graphene films used in the present study were grown on semi-insulating 6H-SiC substrates by thermal decomposition of SiC at the temperature of ~1700 °C. The results of measurements by Auger and Raman spectroscopies confirmed the presence of single-layer graphene on the silicon carbide surface. Model approach to the theory of adsorption on epitaxial graphene is presented. It is demonstrated that the Green-function method in conjunction with the simple substrate models permit one to obtain analytical results for the charge transfer between adsorbed molecules and substrate. The sensor structure was formed on the graphene film by laser. Initially, a simpler gas sensor was made. The sensors developed in this study demonstrated sensitivity to the NO₂ concentration at the level of 1–0.01 ppb. The results obtained in the course of development and the results of testing of the graphene-based sensor for detection of protein molecules are also presented. The biosensor was fabricated by the technology previously developed for the gas sensor. The working capacity of the biosensor was tested with an immunochemical system constituted by fluorescein and monoclonal antibodies (mAbs) binding this dye.

Epitaxial graphene layers are produced with the aid of thermal destruction of the surface of a semi-insulating SiC substrate. Raman spectroscopy and atomic-force microscopy are employed in the study...

The electronic and optoelectronic properties of van der Waals heterostructures are strongly affected by heterobarrier heights at the interfaces between monolayers forming the structure and the environment. In this work, properties of MoSe ₂ /graphene/6H-SiC heterostructures are studied by scanning probe microscopy and photoluminescence spectroscopy in various ambient conditions. To improve our understanding of the electronic processes, a work function of the monolayer MoSe ₂ and its dependence on the number of layers were determined by Kelvin probe microscopy. A nonuniform distribution of the photoluminescence intensity from the MoSe ₂ monolayer was observed because of bilayer graphene (BLG) inclusions in the monolayer graphene (MLG) covering the 6H-SiC substrate. The measured values of the MoSe ₂ work function allow the construction of band energy diagrams for MoSe ₂ /MLG and MoSe ₂ /BLG heterobarriers, which show an increased barrier height for MLG with respect to BLG. This relatively high potential barrier at MoSe ₂ /MLG leads to quenching of the photoluminescence because of separation of the electron–hole pairs at the barrier before the formation of the exciton. Moreover, selective photodegradation of the MoSe ₂ layers on MLG due to photooxidation during light illumination was observed. The photooxidation was promoted by accumulation of excess holes at the MoSe ₂ /MLG interface, which further participate in splitting of a surface water film. Generation of the oxygen at the heterojunction interface leads to the oxidation of the MoSe ₂ . The dependence of the photoluminescence and photodegradation of MoSe ₂ on the graphene layers shows the importance of the substrate selection for good device stability based on van der Waals heterostructures with MoSe ₂ .

Systematic studies of the effect of the electron concentration on the Raman spectra of single-layer graphene films have been carried out. The samples were grown by thermal destruction of the...