14 research outputs found
Lattice dynamics localization in low-angle twisted bilayer graphene
A low twist angle between the two stacked crystal networks in bilayer
graphene enables self-organized lattice reconstruction with the formation of a
periodic domain. This superlattice modulates the vibrational and electronic
structures, imposing new rules for electron-phonon coupling and the eventual
observation of strong correlation and superconductivity. Direct optical images
of the crystal superlattice in reconstructed twisted bilayer graphene are
reported here, generated by the inelastic scattering of light in a nano-Raman
spectroscope. The observation of the crystallographic structure with visible
light is made possible due to lattice dynamics localization, the images
resembling spectral variations caused by the presence of strain solitons and
topological points. The results are rationalized by a nearly-free-phonon model
and electronic calculations that highlight the relevance of solitons and
topological points, particularly pronounced for structures with small twist
angles. We anticipate our discovery to play a role in understanding Jahn-Teller
effects and electronic Cooper pairing, among many other important
phonon-related effects, and it may be useful for characterizing devices in the
most prominent platform for the field of twistronics.Comment: 9 pages, 8 figure
Positioning of self-assembled, single-crystal, germanium islands by silicon nanoimprinting
Strain energy from the lattice mismatch of a heteroepitaxial system can create "self-assembled," single-crystal islands irregularly arranged on the surface. Alternatively, features of tens of nanometers can be patterned on a substrate by "nanoimprinting" using a mold and etching. When these two techniques are combined, the small patterned features can interact with the self-assembly process, causing the islands to form at the patterned features. The resulting regular array of very small islands may be useful for future devices. The positioning of single-crystal Ge islands by Si mesas formed by nanoimprinting and etching is demonstrated in this letter
Fabrication of a 34 × 34 Crossbar Structure at 50 nm Half-pitch by UV-based Nanoimprint Lithography
A hybrid nanomemristor/transistor logic circuit capable of self-programming
Memristor crossbars were fabricated at 40 nm half-pitch, using nanoimprint lithography on the same substrate with Si metal-oxide-semiconductor field effect transistor (MOS FET) arrays to form fully integrated hybrid memory resistor (memristor)/transistor circuits. The digitally configured memristor crossbars were used to perform logic functions, to serve as a routing fabric for interconnecting the FETs and as the target for storing information. As an illustrative demonstration, the compound Boolean logic operation (A AND B) OR (C AND D) was performed with kilohertz frequency inputs, using resistor-based logic in a memristor crossbar with FET inverter/amplifier outputs. By routing the output signal of a logic operation back onto a target memristor inside the array, the crossbar was conditionally configured by setting the state of a nonvolatile switch. Such conditional programming illuminates the way for a variety of self-programmed logic arrays, and for electronic synaptic computing