Schematic drawing illustrating the idea of atomic scale nanofabrication with EBESA. The process is illustrated with a graphene layer, which is a monolayer of carbon atoms in a hexagonal lattice. The electron beam, focused into a spot of a size smaller than the distance between the atoms, is used to expel unwanted atoms from the graphene layer. By this approach, nanofabrication with atomic resolution might be achieved. The drawing illustrates a hypothetical tripod electronic device (yellow and black). The exact shape of the device can be tailored to the desired function of the device.
Electron beam modification of a freely suspended MWNT. (a) Freely suspended arc discharge MWNT (scale of ). (b) Freely suspended arc discharge MWNT with an e-beam drilled 2.5 nm diameter nanohole. The majority of the nanotube is unchanged (scale of ). Modification was in a hot stage at .
Various modifications of MWNTs with a focused electron beam. (a) A “small” ( diameter) nanohole in a MWNT (scale of ), (b) a “large” across elliptical nanohole in a 26 nm diameter MWNT (scale of ), and (c) a constriction in a MWNT fabricated by etching in from both sides (scale of ). Modification was in a hot stage at .
Drilling multiple holes in a niobium nanowire with a 200 keV electron beam. The width of the wire is about 20 nm. (a) Initial unmodified niobium wire (scale of ). (b) Single nanohole drilled with a focused electron beam (scale of ). (c) Two nanoholes drilled with a focused electron beam (scale of ). (d) Three nanoholes drilled with focused electron beam (scale of ). The sizes of the holes are 3, 2, and 2 nm, respectively. The distances between the holes are 6 and 9 nm. Grains of the material typically form near the holes drilled and are visible as darker spots. Modification was at room temperature.
Electron beam modification of a MWNT on a silicon nitride membrane. (a) TEM micrograph of an unmodified nanotube placed on the surface of a 50 nm low-stress silicon nitride membrane (scale of ). The gray colored background corresponds to the amorphous SiN membrane. The image is underfocused (creating white diffraction lines at the edges) to contrast the nanotube against the amorphous layer. The black spots are from the deposition process. (b) Close-up TEM micrograph of the unmodified tube in a scale of . (c) TEM micrograph of the nanotube after modification with the electron beam of the TEM (scale of ). (d) Close-up TEM micrograph of the modified nanotube with a nanohole (on the left, ) and two nanoconstrictions. In the nanoconstrictions, the silicon nitride can still be seen (scale of ). Modification was at room temperature.
A TEM micrograph of a nanopore etched in a SiN membrane with a 200 keV focused electron beam (scale of ). The white lines indicate the location of the MWNT. The hole is purposefully positioned near a MWNT. This sample design might be useful for experiments where molecules or nanoparticles are translocated through the pore and detected or characterized with the nanotubes. This sample design might be useful for DNA/nanopore sequencing.
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