Dislocation-driven surface dynamics on solids

Abstract

Dislocations are line defects that bound plastically deformed regions in crystalline solids. Dislocations terminating on the surface of materials can strongly influence nanostructural and interfacial stability, mechanical properties, chemical reactions, transport phenomena, and other surface processes. While most theoretical and experimental studies have focused on dislocation motion in bulk solids under applied stress and step formation due to dislocations at surfaces during crystal growth, very little is known about the effects of dislocations on surface dynamics and morphological evolution. Here we investigate the near-equilibrium dynamics of surface-terminated dislocations using low-energy electron microscopy. We observe, in real time, the thermally driven nucleation and shape-preserving growth of spiral steps rotating at constant temperature-dependent angular velocities around cores of dislocations terminating on the (111) surface of TiN in the absence of applied external stress or net mass change. We attribute this phenomenon to point-defect migration from the bulk to the surface along dislocation lines. Our results demonstrate that dislocation-mediated surface roughening can occur even in the absence of deposition or evaporation, and provide fundamental insights into mechanisms controlling nanostructural stability.

Effects of surface vibrations on interlayer mass transport: Ab initio molecular dynamics investigation of Ti adatom descent pathways and rates from TiN/TiN(001) islands

“…Crystal growth is a complex phenomenon governed by an intricate interplay between thermodynamic and surface kinetic effects [1][2][3]. Control of nanostructural evolution during synthesis allows a material's properties to be tailored to meet specific demands.…”

Kinetics of Ga droplet decay on thin carbon films

“…In case the observed decay of Ga droplets is due to diffusion of Ga into the bulk of the sample or evaporation into vacuum, all of the droplets would decrease in size. [33][34][35][36] We find that droplets B-I exhibit decay while the size of droplet A remains nearly constant at all t. Moreover, the rates of changes in droplet size are not the same for all the droplets. For example, the sizes of smaller droplets F and G decrease continuously, while the sizes of larger droplets B and C change little initially and decrease at later times.…”

Confocal microscopy of geometrically frustrated hard sphere crystals

“…This length scale makes them very suitable to be studied in realspace and real-time by microscopy techniques [22][23][24]. In particular, the combination of advanced colloidal particles and confocal microscopy has already made it possible to study several fundamental condensed matter problems, such as freezing, melting and glass formation, on the single-particle level [10,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Interestingly, colloidal systems exhibit similar phase-behaviour as atomic systems, making colloids a powerful model-system for condensed matter and atomic materials [37][38][39][40].…”