Capturing Dislocation Half-Loop Formation and Dynamics in Epitaxial Growth Atomistically at Diffusive Time Scales

Materialia ◽  
2021 ◽  
pp. 101253
Author(s):  
Salvador Valtierra Rodriguez ◽  
Mathieu Frick ◽  
Nathaniel Quitoriano ◽  
Nana Ofori-Opoku ◽  
Nikolas Provatas ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Time Scales ◽  
Loop Formation ◽  
Half Loop ◽  
Diffusive Time

Evolution of Basal Plane Dislocations during 4H-SiC Epitaxial Growth

2008 ◽  
Vol 600-603 ◽  
pp. 317-320 ◽  
Author(s):  
Robert E. Stahlbush ◽  
Brenda L. VanMil ◽  
Kendrick X. Liu ◽  
Kok Keong Lew ◽  
Rachael L. Myers-Ward ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Basal Plane ◽  
Gas Flow ◽  
Epitaxial Layers ◽  
Half Loop ◽  
Edge Dislocations

The evolution of basal plane dislocations (BPDs) in 4H-SiC epitaxy during its growth is investigated by using two types of interrupted growth in conjunction with ultraviolet photoluminescence (UVPL) imaging of the dislocations. For the first, each epitaxial growth was stopped after 10-20 μm and a UVPL map was collected. For the second, changing the gas flow interrupted the growth and the BPDs were imaged at the end. The first sequence made it possible to track the formation of half-loop arrays and show that they arise from BPDs that glide perpendicular to the offcut direction. For both types, each interruption causes between 30 – 50% of the BPDs to be converted to threading edge dislocations (TEDs). This result suggests that using interrupted growth may be an alternate method to producing epitaxial layers with low BPD concentration.

A Pictorial Tracking of Basal Plane Dislocations in SiC Epitaxy

2010 ◽  
Vol 645-648 ◽  
pp. 271-276 ◽  
Author(s):  
Robert E. Stahlbush ◽  
Rachael L. Myers-Ward ◽  
Brenda L. VanMil ◽  
D. Kurt Gaskill ◽  
Charles R. Eddy
Keyword(s):  
Epitaxial Growth ◽  
Basal Plane ◽  
Reduction Process ◽  
Epitaxial Layers ◽  
In Situ Growth ◽  
Half Loop ◽  
Insight Into

The recently developed technique of UVPL imaging has been used to track the path of basal plane dislocations (BPDs) in SiC epitaxial layers. The glide of BPDs during epitaxial growth has been observed and the role of this glide in forming half-loop arrays has been examined. The ability to track the path of BPDs through the epitaxy has made it possible to develop a BPD reduction process for epitaxy grown on 8° offcut wafers, which uses an in situ growth interrupt and has achieved a BPD reduction of > 98%. The images also provide insight into the strong BPD reduction that typically occurs in epitaxy grown on 4° offcut wafers.

Dislocation half loop formation in GaSb/(001)GaAs islands and steps role: a Monte Carlo simulation

1998 ◽  
Vol 336 (1-2) ◽  
pp. 277-280
Author(s):  
J.Dalla Torre ◽  
M.Djafari Rouhani ◽  
G. Landa ◽  
A.M. Rocher ◽  
R. Malek ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Loop Formation ◽  
Half Loop

scholarly journals Phase-field-crystal models for condensed matter dynamics on atomic length and diffusive time scales: an overview

2012 ◽  
Vol 61 (6) ◽  
pp. 665-743 ◽  
Author(s):  
Heike Emmerich ◽  
Hartmut Löwen ◽  
Raphael Wittkowski ◽  
Thomas Gruhn ◽  
Gyula I. Tóth ◽  
...  
Keyword(s):  
Time Scales ◽  
Phase Field ◽  
Condensed Matter ◽  
Diffusive Time ◽  
Phase Field Crystal

scholarly journals Heterogeneity in Nucleosome Spacing Governs Chromatin Elasticity

2019 ◽  
Author(s):  
Bruno Beltran ◽  
Deepti Kannan ◽  
Quinn MacPherson ◽  
Andrew J. Spakowitz
Keyword(s):  
Time Scales ◽  
Living Cell ◽  
Double Helix ◽  
Chromatin Organization ◽  
Chromatin Loop ◽  
Loop Formation ◽  
Dominant Source ◽  
Wormlike Chain ◽  
Dna Double Helix ◽  
Nucleosome Binding

Within a living cell, the myriad of proteins that bind DNA introduce heterogeneously spaced kinks into an otherwise semiflexible DNA double helix. To investigate the effects of heterogeneous nucleosome binding on chromatin organization, we extend the wormlike chain (WLC) model to include statistically spaced, rigid kinks. On time scales where nucleosome positions are fixed, we find that the probability of chromatin loop formation can differ by up to six orders of magnitude between two sets of nucleosome positions drawn from the same distribution. On longer time scales, we show that continuous re-randomization due to nucleosome turnover results in chromatin tracing out an effective WLC with a dramatically smaller Kuhn length than bare DNA. Together, these observations demonstrate that heterogeneity in nucleosome spacing acts as the dominant source of chromatin elasticity and governs both local and global chromatin organization.

scholarly journals Coherent and Diffusive Time Scales for Exciton Dissociation in Bulk Heterojunction Photovoltaic Cells

2014 ◽  
Vol 118 (47) ◽  
pp. 27235-27244 ◽  
Author(s):  
K. Birgitta Whaley ◽  
Aleksey A. Kocherzhenko ◽  
Abraham Nitzan
Keyword(s):  
Time Scales ◽  
Bulk Heterojunction ◽  
Photovoltaic Cells ◽  
Exciton Dissociation ◽  
Diffusive Time

Current Status of the Quality of 4H-SiC Substrates and Epilayers for Power Device Applications

MRS Advances ◽  
2016 ◽  
Vol 1 (2) ◽  
pp. 91-102 ◽  
Author(s):  
M. Dudley ◽  
H. Wang ◽  
Jianqiu Guo ◽  
Yu Yang ◽  
Balaji Raghothamachar ◽  
...  
Keyword(s):  
Relaxation Process ◽  
Epitaxial Growth ◽  
Driving Force ◽  
Lattice Parameter ◽  
Current Status ◽  
Concentration Difference ◽  
Before And After ◽  
Half Loop ◽  
Device Applications ◽  
Edge Dislocations

ABSTRACTInterfacial dislocations (IDs) and half-loop arrays (HLAs) present in the epilayers of 4H-SiC crystal are known to have a deleterious effect on device performance. Synchrotron X-ray Topography studies carried out on n-type 4H-SiC offcut wafers before and after epitaxial growth show that in many cases BPD segments in the substrate are responsible for creating IDs and HLAs during CVD growth. This paper reviews the behaviors of BPDs in the substrate during the epitaxial growth in different cases: (1) screw-oriented BPD segments intersecting the surface replicate directly through the interface during the epitaxial growth and take part in stress relaxation process by creating IDs and HLAs (Matthews-Blakeslee model [1] ); (2) non-screw oriented BPD half loop intersecting the surface glides towards and replicates through the interface, while the intersection points convert to threading edge dislocations (TEDs) and pin the half loop, leaving straight screw segments in the epilayer and then create IDs and HLAs; (3) edge oriented short BPD segments well below the surface get dragged towards the interface during epitaxial growth, leaving two long screw segments in their wake, some of which replicate through the interface and create IDs and HLAs. The driving force for the BPDs to glide toward the interface is thermal stress and driving force for the relaxation process to occur is the lattice parameter difference at growth temperature which results from the doping concentration difference between the substrate and epilayer.

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