25 research outputs found
Ferromagnetic bubble clusters in Y0.67Ca0.33MnO3 thin films
No full textWe studied the ferromagnetic topology in a Y0.67Ca0.33MnO3 thin film with a combination of magnetic force microscopy and magnetization measurements. Our results show that the spin-glass like behavior, reported previously for this system, could be attributed to frustrated interfaces of the ferromagnetic clusters embedded in a non-ferromagnetic matrix. We found temperature dependent changes of the magnetic topology at low temperatures, which suggests a non-static Mn3+/Mn4+ ratio.Fil: Kim, Jeehoon. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Haberkorn, Nestor Fabian. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Kim, Suenne. Georgia Institute of Technology; Estados UnidosFil: Civale, L.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Dowden, P. C.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Movshovic, R.. Los Alamos National High Magnetic Field Laboratory; Estados Unido
Sliding on a Nanotube: Interplay of Friction, Deformations and Structure
No full textThe frictional properties of individual carbon nanotubes (CNTs) are studied by sliding an atomic force microscopy tip across and along its principle axis. This direction-dependent frictional behavior is found to correlate strongly with the presence of structural defects, surface chemistry, and CNT chirality. This study shows that it is experimentally possible to tune the frictional/adhesion properties of a CNT by controlling the CNT structure and surface chemistry, as well as use friction force to predict its structural and chemical properties. Copyright �� 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Parallelization of thermochemical nanolithography
No full textOne of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. Here, we demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of conjugated polymer nanostructures and graphene-based nanoribbons
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I-V transport measurements of a single unsupported MWCNT under various bending deformations
No full texttextThe first part of this dissertation is an introduction describing a brief historical background of carbon nanotubes (CNTs) and their pseudo 1D structure responsible for many exotic electronic properties. The second part describes our experimental setup. The third part is about the growing of Multi-Walled Carbon Nanotubes (MWCNTs) by the chemical vapor deposition (CVD) method. Then the fourth part demonstrates a simple but reliable method to make firm contact junctions between MWCNTs and metals such as tungsten (W). The novel point of our method consists, after making a mechanical preliminary contact at a selected MWCNT, in applying a series of voltage pulses across the contact. Thin oxide layers that may form between the MWCNT and the W wire, are removed in steps by the resistive heating and electron impact during the application of each voltage pulse. Furthermore, this simple process of contact welding in steps does not bring about any permanent change in the electronic transport properties of the MWCNTs. The fifth part discusses our bending experiments. We apply a uniform and continuous bending to a selected MWCNT at room and liquid nitrogen temperatures to study the strain effect on the electrical transport in the MWCNT. There are a few published experimental works related to the bending deformation; however, this is the first study of electronic transport properties in continuous bending and releasing deformations. We observed a saturation behavior with the MWCNT and also found the bending deformation causing an anomalous change in the saturation behavior. In the sixth part we depict some interesting phenomena due to the stretching deformation of MWCNT, where we were able to propose a simple model for electron localization induced by the deformation. The last part deals with the formation of the "X-junction" between two MWCNTs. A strong X-junction can be formed simply by means of the e-beam inside the Scanning Electron Microscope (SEM). The X-junctions may form the basic elements of nano-electronic circuits such as various metal-insulator junctions, quantum dots, and similar devices.Materials Science and Engineerin
Atomic-level Sharpening of a Carbon Nanotube Tip for High-resolution Scanning Tunneling Microscopy
No full textUsing a multi-walled carbon nanotube (MW-CNT) tip, we have observed the honeycomb lattice of highly oriented pyrolytic graphite (HOPG) via scanning tunneling microscopy (STM). This observation was made after acquiring typical STM images of HOPG, i.e., showing the triangular lattice. We consider this change is due to atomic reconfiguration at the apex of the MW-CNT tip induced by continuous STM scanning. The atomic-level sharpening of CNT tips will be useful to image samples with small lattice constants or to obtain orbital information from samples with an orbital ordering such as manganites.11Nsciescopuskc
Robust Ohmic contact junctions between metallic tips and multiwalled carbon nanotubes for scanned probe microscopy
No full textAccurate Atomic-Scale Imaging of Two-Dimensional Lattices Using Atomic Force Microscopy in Ambient Conditions
No full textTo facilitate the rapid development of van der Waals materials and heterostructures, scanning probe methods capable of nondestructively visualizing atomic lattices and moiré superlattices are highly desirable. Lateral force microscopy (LFM), which measures nanoscale friction based on the commonly available atomic force microscopy (AFM), can be used for imaging a wide range of two-dimensional (2D) materials, but imaging atomic lattices using this technique is difficult. Here, we examined a number of the common challenges encountered in LFM experiments and presented a universal protocol for obtaining reliable atomic-scale images of 2D materials under ambient environment. By studying a series of LFM images of graphene and transition metal dichalcogenides (TMDs), we have found that the accuracy and the contrast of atomic-scale images critically depended on several scanning parameters including the scan size and the scan rate. We applied this protocol to investigate the atomic structure of the ripped and self-folded edges of graphene and have found that these edges were mostly in the armchair direction. This finding is consistent with the results of several simulations results. Our study will guide the extensive effort on assembly and characterization of new 2D materials and heterostructures
Parallelization of thermochemical nanolithography
No full textOne of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. Here, we demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of conjugated polymer nanostructures and graphene-based nanoribbons.This work has been supported by the National Science Foundation CMMI 1100290 (E. R., W. P. K), MRSEC program DMR 0820382 (E. R., J.E.C.), PHYS 0848797 (J.E.C.), the Office of Basic Energy Sciences DOE DE-FG02-06ER46293 (E. R.), the Cariplo Foundation 2011-0373 (L. P., R. S.), and PRIN project GRAF (R.S.)
Controlled AFM manipulation of small nanoparticles and assembly of hybrid nanostructures
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