ABSTRACT
2D van der Waals heterostructure paves a path towards next generation semiconductor junctions for nanoelectronics devices in the post silicon era. Probing the band alignment at a real condition of such 2D contacts and experimental determination of its junction parameters is necessary to comprehend the charge diffusion and transport through such 2D nano-junctions. Here, we demonstrate the formation of the p-n junction at the MoS2/Black phosphorene (BP) interface and conduct a nanoscale investigation to experimentally measure the band alignment at real conditions by means of measuring the spatial distribution of built-in potential, built-in electric field, and depletion width using the Kelvin probe force microscopy (KPFM) technique. We show that optimization of lift scan height is critical for defining the depletion region of MoS2/BP with nanoscale precision using the KPFM technique. The variations in the built-in potential and built-in electric field with varying thicknesses of MoS2are revealed and calibrated.
ABSTRACT
The century-old controversy over two contradicting theories on radiation pressure of light proposed by Abraham and Minkowski can come to an end if there is a direct method to measure the surface deformation of the target material due to momentum transfer of photons. Here we have investigated the effect of radiation pressure on the surface morphology of Graphene Oxide (GO) film, experienced due to low power focused laser irradiation. In-depth investigation has been carried out to probe the bending of the GO surface due to radiation pressure by Atomic Force Microscopy (AFM) and subsequently the uniaxial strain induced on the GO film has been probed by Raman Spectroscopy. Our results show GO film experience an inward pressure due to laser radiation resulting in inward bending of the surface, which is consistent with the Abraham theory. The bending diameter and depth of the irradiated spot show linear dependence with the laser power while an abrupt change in depth and diameter of the irradiated spot is observed at the breaking point. Such abrupt change in depth is attributed to the thinning of the GO film by laser irradiation.
ABSTRACT
Chemical vapour deposition (CVD) is emerging as a popular method for growing large-area graphene on metal substrates. For transferring graphene to other substrates the technique generally used involves deposition of a polymer support with subsequent etching of the metal substrate. Here we report a simpler one-step transfer process. Few-layer graphene (FLG) grown on a Cu substrate were transferred to a silanized wafer by just pressing them together. Hydrogen bonding between the hydroxyl group on FLG and the amine group on silane molecules facilitate the transfer.
ABSTRACT
The surface morphology of bucky papers (BPs) made from single-walled carbon nanotubes (CNTs) is modified by plasma treatment resulting in the formation of vertical microstructures on the surface. The shapes of these structures are either pillarlike or conelike depending on whether the gas used during plasma treatment is Ar or CH(4) . A complex interplay between different factors, such as the electric field within the plasma sheath, polarization of the CNT, intertubular cohesive forces, and ion bombardment, result in the formation of these structures. The roles played by these factors are quantitatively and qualitatively analyzed. The final material is flexible, substrate-free, composite-free, made only of CNTs, and has discrete vertically aligned structures on its surface. It shows enhanced field emission and electrochemical charge-storage capabilities. The field enhancement factor is increased by 6.8 times, and the turn-on field drops by 3.5 times from an initial value of 0.35 to 0.1 V µm(-1) as a result of the treatment. The increase in Brunauer-Emmett-Teller surface area results in about a fourfold improvement in the specific capacitance of the BP electrodes. Capacitance values before and after the treatments are 75 and 290 F g(-1) , respectively. It is predicted that this controlled surface modification technique could be put to good use in several applications based on macroscopic CNT films.
