In this work, we analyzed numerically a multiscale nanosystem based on sMIM on TBG. Spontaneous formation of a water-meniscus by the approximation between the tip-sample concentrates the microwave ...fields, reaching resolutions of up to 1nm.
We introduce a chemical-thermodynamic model to explain the formation and annealing behavior of Ge nanocrystalline islands grown on Si(001). Assuming the nanocrystals are essentially large adsorbed ...molecules, we propose a simple free energy expression for islands of different shapes interacting with each other via the substrate on which they reside. Nanocrystal growth, disappearance, and shape transitions are all consonant with a near-equilibrium system constrained by mass conservation and characterized by interisland repulsions. We construct an equilibrium shape diagram from experimentally determined free energy differences between island shapes and use it to resolve several anomalies that have been noted for the Ge on Si(001) system.
In this work, we study the Raman spectra of twisted bilayer graphene samples as a function of their twist-angles (\(\theta\)), ranging from 0.03\(^\circ\) to 3.40\(^\circ\), where local \(\theta\) ...are determined by analysis of their associated moire superlattices, as imaged by scanning microwave impedance microscopy. Three standard excitation laser lines are used (457, 532, and 633 nm wavelengths), and the main Raman active graphene bands (G and 2D) are considered. Our results reveal that electron-phonon interaction influences the G band's linewidth close to the magic angle regardless of laser excitation wavelength. Also, the 2D band lineshape in the \(\theta\) < 1\(^\circ\) regime is dictated by crystal lattice and depends on both the Bernal (AB and BA) stacking bilayer graphene and strain soliton regions (SP). We propose a geometrical model to explain the 2D lineshape variations, and from it, we estimate the SP width when moving towards the magic angle.
We have developed a single-layer UV-nanoimprint process, which was utilized to fabricate 34 × 34 crossbar circuits with a half-pitch of 50 nm (equivalent to a bit density of 10 Gbit/cm2). This ...process contains two innovative ideas to overcome challenges in the nanoimprint at shrinking dimensions. First, our new liquid resist formulation allowed us to minimize the residual resist layer thickness after curing and requires the relatively low imprint pressure of 20 psi. Second, by engineering the surface energy of the substrate we also eliminated the problem of trapped air during contact with the mold such that it spreads the resist and expels trapped air uniformly. Our overall process required fewer processing steps than any bilayer process and yielded high quality results at 50 nm half-pitch.
Molecular and atomic imaging required the development of electron and scanning probe microscopies to surpass the physical limits dictated by diffraction. Nano-infrared experiments and pico-cavity ...tip-enhanced Raman spectroscopy imaging later demonstrated that radiation in the visible range can surpass this limit by using scanning probe tips to access the near-field regime. Here we show that ultimate resolution can be obtained by using scanning microwave imaging microscopy to reveal structures with feature sizes down to 1~nm using a radiation of 0.1~m in wavelength. As a test material we use twisted bilayer graphene, which is not only a very important recent topic due to the discovery of correlated electron effects such as superconductivity, but also because it provides a sample where we can systematically tune a superstructure Moiré patterns modulation from below one up to tens of nanometers. By analyzing the tip-sample distance dynamics, we demonstrate that this ultimate 10\(^8\) probe-to-pattern resolution can be achieved by using liquid immersion microscopy concepts and exquisite force control exerted on nanoscale water menisci.
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.
PDF