Kristen M. Burson

A Large-Area Transferable Wide Band Gap 2D Silicon Dioxide Layer

An atomically smooth silica bilayer is transferred from the growth substrate to a new support via mechanical exfoliation at millimeter scale. The atomic structure and morphology are maintained perfectly throughout the process. A simple heating treatment results in complete removal of the transfer medium. Low-energy electron diffraction, Auger electron spectroscopy, scanning tunneling microscopy, and environmental scanning electron microscopy show the success of the transfer steps. Excellent chemical and thermal stability result from the absence of dangling bonds in the film structure. By adding this wide band gap oxide to the toolbox of 2D materials, possibilities for van der Waals heterostructures will be broadened significantly.

Resolving amorphous solid-liquid interfaces by atomic force microscopy

Recent advancements in liquid atomic force microscopy make it an ideal technique for probing the structure of solid-liquid interfaces. Here, we present a structural study of a two-dimensional amorphous silica bilayer immersed in an aqueous solution utilizing liquid atomic force microscopy with sub-nanometer resolution. Structures show good agreement with atomically resolved ultra-high vacuum scanning tunneling microscopy images obtained on the same sample system, owing to the structural stability of the silica bilayer and the imaging clarity from the two-dimensional sample system. Pair distance histograms of ring center positions are utilized to develop quantitative metrics for structural comparison, and the physical origin of pair distance histogram peaks is addressed by direct assessment of real space structures.

Assessing the amorphousness and periodicity of common domain boundaries in silica bilayers on Ru(0 0 0 1)

Domain boundaries are hypothesized to play a role in the crystalline to amorphous transition. Here we examine domain boundary structures in comparison to crystalline and amorphous structures in bilayer silica grown on Ru(0 0 0 1). Atomically resolved scanning probe microscopy data of boundaries in crystalline bilayer films are analyzed to determine structural motifs. A rich variety of boundary structures including rotational, closed-loop, antiphase, and complex boundaries are identified. Repeating units with ring sizes of 558 and 57 form the two most common domain boundary types. Quantitative metrics are utilized to assess the structural composition and degree of order for the chemically equivalent crystalline, domain boundary, and amorphous structures. It is found that domain boundaries in the crystalline phase show similarities to the amorphous phase in their ring statistics and, in some cases, in terms of the observed ring neighborhoods. However, by assessing order and periodicity, domain boundaries are shown to be distinct from the glassy state. The role of the Ru(0 0 0 1) substrate in influencing grain boundary structure is also discussed.