Nonradiative Recombination via Conical Intersections Arising at Defects on the Oxidized Silicon Surface

2015 ◽  
Vol 119 (4) ◽  
pp. 1737-1747 ◽  
Author(s):  
Yinan Shu ◽  
Benjamin G. Levine
Keyword(s):  
Silicon Surface ◽  
Nonradiative Recombination ◽  
Conical Intersections

scholarly journals Porous Silicon Structural Evolution from In-Situ Luminescence and Raman Measurements

1996 ◽  
Vol 431 ◽  
Author(s):  
D. R. Tallant ◽  
M. J. Kelly ◽  
T. R. Guilinger ◽  
R. L. Simpson
Keyword(s):  
Porous Silicon ◽  
Silicon Surface ◽  
Structural Evolution ◽  
Surface Oxidation ◽  
Ethanol Solution ◽  
Nonradiative Recombination ◽  
Photoluminescence Intensity ◽  
Exciton Migration ◽  
Photoluminescence Mechanism

AbstractWe performed in-situ photoluminescence and Raman measurements on an anodized silicon surface in the HF/ethanol solution used for anodization. The porous silicon thereby produced, while resident in HF/ethanol, does not immediately exhibit intense photoluminescence. Intense photoluminescence develops spontaneously in HF/ethanol after 18–24 hours or with replacement of the HF/ethanol with water. These results support a quantum confinement mechanism in which exciton migration to traps and nonradiative recombination dominates the de-excitation pathways until silicon nanocrystals are physically separated and energetically decoupled by hydrofluoric acid etching or surface oxidation. The porous silicon surface, as produced by anodization, shows large differences in photoluminescence intensity and peak wavelength over millimeter distances. Parallel Raman measurements implicate nanometer-size silicon particles in the photoluminescence mechanism.

Locality of conical intersections in semiconductor nanomaterials

2019 ◽  
Vol 21 (21) ◽  
pp. 10870-10878 ◽  
Author(s):  
Benjamin G. Levine ◽  
Wei-Tao Peng ◽  
Michael P. Esch
Keyword(s):  
Semiconductor Nanoparticles ◽  
Nonradiative Recombination ◽  
Conical Intersections ◽  
Semiconductor Nanomaterials

We review recent efforts to model nonradiative recombination in semiconductor nanoparticles through conical intersections, focusing on the reasons for and consequences of the locality of such intersections.

scholarly journals Conical Intersections at the Nanoscale: Molecular Ideas for Materials

2019 ◽  
Vol 70 (1) ◽  
pp. 21-43 ◽  
Author(s):  
Benjamin G. Levine ◽  
Michael P. Esch ◽  
B. Scott Fales ◽  
Dylan T. Hardwick ◽  
Wei-Tao Peng ◽  
...  
Keyword(s):  
Materials Science ◽  
Theoretical Study ◽  
Nonradiative Recombination ◽  
Conical Intersections ◽  
Computational Tools ◽  
Recent Developments ◽  
Semiconductor Nanomaterials ◽  
Identification And Characterization ◽  
Nonradiative Processes

The ability to predict and describe nonradiative processes in molecules via the identification and characterization of conical intersections is one of the greatest recent successes of theoretical chemistry. Only recently, however, has this concept been extended to materials science, where nonradiative recombination limits the efficiencies of materials for various optoelectronic applications. In this review, we present recent advances in the theoretical study of conical intersections in semiconductor nanomaterials. After briefly introducing conical intersections, we argue that specific defects in materials can induce conical intersections between the ground and first excited electronic states, thus introducing pathways for nonradiative recombination. We present recent developments in theoretical methods, computational tools, and chemical intuition for the prediction of such defect-induced conical intersections. Through examples in various nanomaterials, we illustrate the significance of conical intersections for nanoscience. We also discuss challenges facing research in this area and opportunities for progress.

Defect-Induced Conical Intersections Promote Nonradiative Recombination

Nano Letters ◽  
2015 ◽  
Vol 15 (9) ◽  
pp. 6247-6253 ◽  
Author(s):  
Yinan Shu ◽  
B. Scott Fales ◽  
Benjamin G. Levine
Keyword(s):  
Nonradiative Recombination ◽  
Conical Intersections

Understanding Nonradiative Recombination through Defect-Induced Conical Intersections

2017 ◽  
Vol 8 (17) ◽  
pp. 4091-4099 ◽  
Author(s):  
Yinan Shu ◽  
B. Scott Fales ◽  
Wei-Tao Peng ◽  
Benjamin G. Levine
Keyword(s):  
Nonradiative Recombination ◽  
Conical Intersections

UHV-STM studies of silicon nano-pyramid growth on silicon surface at high temperature

1992 ◽  
Vol 50 (2) ◽  
pp. 1144-1145
Author(s):  
T. Sato ◽  
S. Kitamura ◽  
T. Sueyoshl ◽  
M. Iwatukl ◽  
C. Nielsen
Keyword(s):  
High Temperature ◽  
Relaxation Process ◽  
Thermal Effect ◽  
Bias Voltage ◽  
Silicon Surface ◽  
Growth Process ◽  
Tunneling Current ◽  
Fabrication Technique ◽  
Nano Fabrication ◽  
Electromigration Effect

Recently, the growth process and relaxation process of crystalline structures were studied by observing a SI nano-pyramid which was built on a Si surface with a UHV-STM. A UHV-STM (JEOL JSTM-4000×V) was used for studying a heated specimen, and the specimen was kept at high temperature during observation. In this study, the nano-fabrication technique utilizing the electromigration effect between the STM tip and the specimen was applied. We observed Si atoms migrated towords the tip on a high temperature Si surface.Clean surfaces of Si(lll)7×7 and Si(001)2×l were prepared In the UHV-STM at a temperature of approximately 600 °C. A Si nano-pyramid was built on the Si surface at a tunneling current of l0nA and a specimen bias voltage of approximately 0V in both polarities. During the formation of the pyramid, Images could not be observed because the tip was stopped on the sample. After the formation was completed, the pyramid Image was observed with the same tip. After Imaging was started again, the relaxation process of the pyramid started due to thermal effect.

Profile Imaging of Silicon Surface Reconstructions

1985 ◽  
Vol 43 ◽  
pp. 262-263
Author(s):  
O.L. Krivanek ◽  
G.J. Wood
Keyword(s):  
Electron Microscopy ◽  
Surface Structure ◽  
Structure Determination ◽  
Silicon Surface ◽  
Good Resolution ◽  
Surface Reconstructions ◽  
Bulk Structure ◽  
Point To Point ◽  
The Relationship

Electron microscopy at 0.2nm point-to-point resolution, 10-10 torr specimei region vacuum and facilities for in-situ specimen cleaning presents intere; ing possibilities for surface structure determination. Three methods for examining the surfaces are available: reflection (REM), transmission (TEM) and profile imaging. Profile imaging is particularly useful because it giv good resolution perpendicular as well as parallel to the surface, and can therefore be used to determine the relationship between the surface and the bulk structure.

Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates

1985 ◽  
Vol 43 ◽  
pp. 364-365
Author(s):  
K.M. Hones ◽  
P. Sheldon ◽  
B.G. Yacobi ◽  
A. Mason
Keyword(s):  
High Efficiency ◽  
Lattice Mismatch ◽  
Low Cost ◽  
Growth Conditions ◽  
Nonradiative Recombination ◽  
Device Structure ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dislocation Type

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.

Frustration and (111) silicon surface

1983 ◽  
Vol 44 (2) ◽  
pp. 257-261 ◽  
Author(s):  
B.K. Chakraverty
Keyword(s):  
Silicon Surface
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