Theoretical modeling of excitation and de-excitation processes of Er in SiO2 with Si nanocrystals

The low energy loss region of a EELS spectrum carries information about the valence electron excitation processes (e.g., collective excitations for free electron like materials and interband transitions for insulators). The relative intensities and the positions of the interband transition energy loss peaks observed in EELS spectra are determined by the joint density of states (DOS) of the initial and final states of the excitation processes. Thus it is expected that EELS in reflection mode could yield information about the perturbation of the DOS of the conduction and valence bands of the bulk crystals caused by the termination of the three dimensional periodicity at the crystal surfaces. The experiments were performed in a Philipps 400T transmission electron microscope operated at 120 kV. The reflection EELS spectra were obtained by a Gatan 607 EELS spectrometer together with a Tracor data acquisition system and the resolution of the spectrometer was about 0.8 eV. All the reflection spectra are obtained from the specular reflection spots satisfying surface resonance conditions.

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The role of ligands in electron transport in nanocrystal solids

Nanoscale ◽

10.1039/d0nr06892f ◽

2020 ◽

Vol 12 (45) ◽

pp. 23028-23035

Author(s):

Artem R. Khabibullin ◽

Alexander L. Efros ◽

Steven C. Erwin

Keyword(s):

Electron Transport ◽

Theoretical Modeling

Theoretical modeling of wavefunction overlap in nanocrystal solids elucidates the important role played by ligands in electron transport.

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Hysteresis in spectral state transitions – a challenge for theoretical modeling

Astronomy and Astrophysics ◽

10.1051/0004-6361:20041631 ◽

2005 ◽

Vol 432 (1) ◽

pp. 181-187 ◽

Cited By ~ 58

Author(s):

E. Meyer-Hofmeister ◽

B. F. Liu ◽

F. Meyer

Keyword(s):

Theoretical Modeling ◽

State Transitions ◽

Spectral State

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Epistemological Status of Models and Thought Experiments in Economics

Voprosy Ekonomiki ◽

10.32609/0042-8736-2015-2-123-140 ◽

2015 ◽

pp. 123-140 ◽

Cited By ~ 1

Author(s):

O. Koshovets ◽

T. Varkhotov

Keyword(s):

Natural Science ◽

Thought Experiment ◽

Thought Experiments ◽

Theoretical Modeling ◽

Epistemological Status ◽

Epistemological Analysis ◽

Field Of Inquiry

The paper considers the analogy of theoretical modeling and thought experiment in economics. The authors provide historical and epistemological analysis of thought experiments and their relations to the material experiments in natural science. They conclude that thought experiments as instruments are used both in physics and in economics, but in radically different ways. In the natural science, a thought experiment is tightly connected to the material experimentation, while in economics it is used in isolation. Material experiments serve as a means to demonstrate the reality, while thought experiments cannot be a full-fledged instrument of studying the reality. Rather, they constitute the instrument of structuring the field of inquiry.

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Theoretical modeling of the regular olivine intergrowths in the mimetic paramorphosis after ringwoodite and wadsleyite

Moscow University Bulletin. Series 4. Geology ◽

10.33623/0579-9406-2018-4-3-12 ◽

2018 ◽

pp. 3-12

Author(s):

B. B. Shkursky

Keyword(s):

Transition Zone ◽

Theoretical Modeling ◽

Mantle Transition Zone ◽

Misorientation Angles

Theoretical modeling of regular olivine grains misorientations in mimetic paramorphoses after ringwoodite and wadsleyite, the formation of which during the ascension of matter from the Mantle Transition Zone is expected, has been carried out. The coordinates of the misorientation axes and the misorientation angles, characterizing 10 operations of alignment in the pair intergrowths of olivine grains, eight of which are twins, are calculated. Possible conditions for the formation of mimetic paramorphoses predicted here, and the chances of their persistence are discussed. The calculated orientations are compared with the known twinning laws of olivine.

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Formation of Luminescent Si Nanocrystals by High-Temperature Annealing of Ion-Beam-Sputtered Si/SiO2 Multilayers

MRS Proceedings ◽

10.1557/proc-775-p9.57 ◽

2003 ◽

Vol 775 ◽

Author(s):

Suk-Ho Choi ◽

Jun Sung Bae ◽

Kyung Jung Kim ◽

Dae Won Moon

Keyword(s):

Quantum Confinement ◽

Radiative Recombination ◽

Ion Beam ◽

Quantum Confinement Effect ◽

Visible Range ◽

Ion Beam Sputtering ◽

Transmission Electron ◽

Si Nanocrystals ◽

Beam Sputtering ◽

Microscopy Images

AbstractSi/SiO2 multilayers (MLs) have been prepared under different deposition temperatures (TS) by ion beam sputtering. The annealing at 1200°C leads to the formation of Si nanocrystals in the Si layer of MLs. The high resolution transmission electron microscopy images clearly demonstrate the existence of Si nanocrystals, which exhibit photoluminescence (PL) in the visible range when TS is ≥ 300°C. This is attributed to well-separation of nanocrystals in the higher-TS samples, which is thought to be a major cause for reducing non-radiative recombination in the interface between Si nanocrystal and surface oxide. The visible PL spectra are enhanced in its intensity and are shifted to higher energy by increasing TS. These PL behaviours are consistent with the quantum confinement effect of Si nanocrystals.

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