All-carbon vertical van der Waals heterostructures: non-destructive functionalization of graphene for electronic applications.

Non-destructive chemical functionalization of graphene for applications in electronic devices (e.g., sensors or transducers) is achieved via assembly of carbon nanomembrane (CNM)/single-layer graphene (SLG) van der Waals heterostructures. The CNMs are 1 nm-thick, dielectric molecular sheets terminated with functional amino groups. The structure and performance of heterostructured field-effect transistors (FETs) are characterized by photoelectron/Raman spectroscopy and by electric transport measurements in vacuum, ambient conditions and water.

Functional single-layer graphene sheets from aromatic monolayers.

Self-assembled monolayers of aromatic molecules on copper substrates can be converted into high-quality single-layer graphene using low-energy electron irradiation and subsequent annealing. This two-dimensional solid state transformation is characterized on the atomic scale and the physical and chemical properties of the formed graphene sheets are studied by complementary microscopic and spectroscopic techniques and by electrical transport measurements. As substrates, Cu(111) single crystals and the technologically relevant polycrystalline copper foils are successfully used.

AFM diagnostics of graphene-based quantum Hall devices.

In this paper we present the results of morphological, mechanical and electrical investigation of the properties of prepared graphene flakes and graphene-based quantum Hall devices. AFM imaging allowed us to identify the local imperfections and unintentional modifications of the graphene sheets which had caused severe deterioration of the device electrical performance. Utilizing the NanoSwing imaging method, based on the time-resolved tapping mode, we could observe non-homogeneities of the structural and mechanical properties. We also diagnosed the device under working conditions by Kelvin probe microscopy and detected its local electric field distribution.

Versatile sputtering technology for Al2O3 gate insulators on graphene.

We report a novel, sputtering-based fabrication method of Al2O3 gate insulators on graphene. Electrical performance of dual-gated mono- and bilayer exfoliated graphene devices is presented. Sputtered Al2O3 layers possess comparable quality to oxides obtained by atomic layer deposition with respect to a high relative dielectric constant of about 8, as well as low-hysteresis performance and high breakdown voltage. We observe a moderate carrier mobility of about 1000 cm2 V-1 s-1 in monolayer graphene and 350 cm2 V-1 s-1 in bilayer graphene, respectively. The mobility decrease can be attributed to the resonant scattering on atomic-scale defects, likely originating from the Al precursor layer evaporated prior to sputtering.

Tunneling/shear force microscopy using piezoelectric tuning forks for characterization of topography and local electric surface properties.

Characterization of novel nanoelectronic structures and materials requires advanced and high-resolution diagnostic methods. In this article new approach for high sensitivity measurements of electric surface properties using scanning probe microscopy is presented. In this procedure topography and tunneling current flowing between the metallic tip and the surface are observed simultaneously. In our design piezoelectric tuning fork equipped with metallic tip in shear force microscope is used. In our experiments we also applied an additional feedback loop to maintain constant tunneling current while scanning over electrical inhomogeneous surfaces. In this way crosstalk between topography and tunneling current measurements is reduced. The described method was tested on nanocrystalline diamond and gold thin films deposited on silicon substrates.

Ovine colostrum nanopeptide affects amyloid beta aggregation.

A colostral proline-rich polypeptide complex (PRP) consisting of over 30 peptides shows beneficial effects in Alzheimer's disease (AD) patients when administered in the form of sublinqual tablets called Colostrinin. The aim of the present studies was to investigate whether nanopeptide fragment of PRP (NP) - one of the PRP complex components can affect aggregation of amyloid beta (Abeta1-42). The effect of NP on Abeta aggregation was studied using Thioflavin T (ThT) binding, atomic force microscopy, and analyzing circular dichroism spectra. Results presented suggest that NP can directly interact with amyloid beta, inhibit its aggregation and disrupt existing aggregates acting as a beta sheet breaker and reduce toxicity induced by aggregated forms of Abeta.