arXiv subjects

Colin Ophus

Publications and source records attributed to Colin Ophus.

111 records · Page 7Linked to original sources

arXiv2015

Large-Scale Experimental and Theoretical Study of Graphene Grain Boundary Structures

We have characterized the structure of 176 different single-layer graphene grain boundaries using $>$1000 experimental HRTEM images using a semi-automated structure processing routine. We introduce a new algorithm for generating grain boundary structures for a class of hexagonal 2D materials and use this algorithm and molecular dynamics to simulate the structure of $>$79000 graphene grain boundaries covering 4122 unique orientations distributed over the entire parameter space. The dislocation content and structural properties are extracted from all experimental and simulated boundaries, and various trends are explored. We find excellent agreement between the simulated and experimentally observed grain boundaries. Our analysis demonstrates the power of a statistically significant number of measurements as opposed to a small number of observations in atomic science. All experimental and simulated boundary structures are available online.

cond-mat.mtrl-sci↗

arXiv2015

Correcting nonlinear drift distortion of scanning probe microscopy from image pairs with orthogonal scan directions

Unwanted motion of the probe with respect to the sample is a ubiquitous problem in scanning probe microscopy, causing both linear and nonlinear artifacts in experimental images. We have designed a procedure to correct these artifacts by using orthogonal scan pairs to align each measurement line-by-line along the slow scan direction. We demonstrate the accuracy of our algorithm on both synthetic and experimental data and provide an implementation of our method.

cond-mat.mtrl-sci↗

arXiv2015

Three-dimensional coordinates of individual atoms in materials revealed by electron tomography

Crystallography, the primary method for determining the three-dimensional (3D) atomic positions in crystals, has been fundamental to the development of many fields of science. However, the atomic positions obtained from crystallography represent a global average of many unit cells in a crystal. Here, we report, for the first time, the determination of the 3D coordinates of thousands of individual atoms and a point defect in a material by electron tomography with a precision of ~19 picometers, where the crystallinity of the material is not assumed. From the coordinates of these individual atoms, we measure the atomic displacement field and the full strain tensor with a 3D resolution of ~1nm^3 and a precision of ~10^-3, which are further verified by density functional theory calculations and molecular dynamics simulations. The ability to precisely localize the 3D coordinates of individual atoms in materials without assuming crystallinity is expected to find important applications in materials science, nanoscience, physics and chemistry.

cond-mat.mtrl-sci↗