Quantum-confined photoresponse tuning of an Esaki–Tsu-type doping superlattice

1991 ◽  
Vol 69 (1) ◽  
pp. 1-7 ◽  
Author(s):  
B. Ullrich ◽  
R. Hott ◽  
J. E. Cunningham
Keyword(s):  
Valence Band ◽  
Conduction Band ◽  
Host Material ◽  
Two Dimensional ◽  
Photocurrent Response ◽  
Contact Distance ◽  
Doping Technique ◽  
First Time ◽  
Direct Confirmation ◽  
Photocurrent Spectra

We performed photocurrent measurements on GaAs-type-A (Esaki–Tsu-type) doping superlattices produced by a δ-doping technique (impurity growth mode) using a new kind of p- and n-contact on a 500 μm × 500 μm mesa plane. We measured, for the first time, a monotonically increased photocurrent below the gap of the host material with horizontal plateaus, as expected for two-dimensional systems. This is the direct confirmation of the two-dimensional nature of this kind of superlattice. In this context, the influence of the contact distance on the photocurrent response is discussed showing that, in contrast to the general case, a variation of the distance between the contacts not only results in a scaling of the photocurrent spectra but changes the complete shape of the photocurrent response for these two-dimensional structures. The possible energetic transitions between the valence band and the conduction band below the gap of the host material, causing the absorption of the doping superlattice, are calculated and explained with an analytical theory. Furthermore, a comparison with other previously performed numerical calculations shows the limits of validity of the analytical calculations presented here.

INFLUENCE OF OPTICAL EXCITATION OF TWO-DIMENSIONAL SURFACE SUBBANDS ON PHOTOCURRENT ACROSS SEMICONDUCTOR–ELECTROLYTE INTERFACE

1997 ◽  
Vol 04 (05) ◽  
pp. 933-935 ◽  
Author(s):  
H. L. MARGARIAN ◽  
V. A. MELICKSETIAN ◽  
V. M. AROUTIOUNIAN
Keyword(s):  
Valence Band ◽  
Conduction Band ◽  
Optical Excitation ◽  
Optical Transitions ◽  
Two Dimensional ◽  
Electrolyte Interface ◽  
Dimensional Surface

It was shown that in the case of TiO 2 contacted with an electrolyte, optical transitions of electrons from the valence band to the two-dimensional surface subband located near the conduction band or covered with the band.

Electronic structure of the Peierls compound K0.9Mo6O17

2002 ◽  
Vol 12 (9) ◽  
pp. 95-96
Author(s):  
H. Guyot ◽  
H. Balaska ◽  
J. Marcus
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Fermi Level ◽  
Valence Band ◽  
Conduction Band ◽  
Room Temperature ◽  
Two Dimensional ◽  
Conduction Electrons ◽  
Peierls Transition ◽  
Good Agreement

The purple potassium bronze of molybdenum is a quasi two-dimensional compound showing a Peierls transition at 120 K. This transition is driven by the properties of the conduction electrons. In order to confirm the nature of the transition, we have investigated at room temperature the electronic structure of this oxide and established its band structure in the ΓK direction. A weak conduction band is detected, well separated from the valence band by a depleted region. The valence band shows several structures attributed to oxygen-type states and to the K3p shallow core level. The structures of the conduction band reveal the presence of at least two bands crossing the Fermi level, in relatively good agreement with the calculated band structure.

scholarly journals Influence of a Standing Wave Flow-Field on the Dynamics of a Spray Diffusion Flame

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 27
Author(s):  
J. Barry Greenberg ◽  
David Katoshevski
Keyword(s):  
Liquid Phase ◽  
Flow Field ◽  
Standing Wave ◽  
Diffusion Flame ◽  
Stokes Number ◽  
Flame Height ◽  
Wave Flow ◽  
Two Dimensional ◽  
Governing Equations ◽  
First Time

A theoretical investigation of the influence of a standing wave flow-field on the dynamics of a laminar two-dimensional spray diffusion flame is presented for the first time. The mathematical analysis permits mild slip between the droplets and their host surroundings. For the liquid phase, the use of a small Stokes number as the perturbation parameater enables a solution of the governing equations to be developed. Influence of the standing wave flow-field on droplet grouping is described by a specially constructed modification of the vaporization Damkohler number. Instantaneous flame front shapes are found via a solution for the usual Schwab–Zeldovitch parameter. Numerical results obtained from the analytical solution uncover the strong bearing that droplet grouping, induced by the standing wave flow-field, can have on flame height, shape, and type (over- or under-ventilated) and on the existence of multiple flame fronts.

scholarly journals Tetrazine molecules as efficient electronic diversion channel in 2D organic-inorganic perovskites

2021 ◽  
Author(s):  
Ferdinand Lédée ◽  
Pierre Audebert ◽  
Gaëlle Trippé-Allard ◽  
Laurent Galmiche ◽  
Damien Garrot ◽  
...  
Keyword(s):  
Organic Component ◽  
Two Dimensional ◽  
Diversion Channel ◽  
Halide Perovskites ◽  
First Time

We present the synthesis of two novel two-dimensional (2D) hybrid organic-inorganic halide perovskites incorporating for the first time 100% of a photoactive tetrazine derivative as the organic component. With this...

scholarly journals Exfoliation in a low boiling point solvent and electrochemical applications of MoO3

2020 ◽  
Vol 11 ◽  
pp. 662-670
Author(s):  
Matangi Sricharan ◽  
Bikesh Gupta ◽  
Sreejesh Moolayadukkam ◽  
H S S Ramakrishna Matte
Keyword(s):  
Energy Storage ◽  
Electrode Material ◽  
Electronic Devices ◽  
High Specific Capacitance ◽  
Two Dimensional ◽  
Energy Storage Devices ◽  
Intrinsic Nature ◽  
Storage Devices ◽  
Scan Rate ◽  
First Time

MoO3 is a versatile two-dimensional transition metal oxide having applications in areas such as energy storage devices, electronic devices and catalysis. To efficiently utilize the properties of MoO3 arising from its two-dimensional nature exfoliation is necessary. In this work, the exfoliation of MoO3 is carried out in 2-butanone for the first time. The achieved concentration of the dispersion is about 0.57 mg·mL−1 with a yield of 5.7%, which are the highest values reported to date. These high values of concentration and yield can be attributed to a favorable matching of energies involved in exfoliation and stabilization of MoO3 nanosheets in 2-butanone. Interestingly, the MoO3 dispersion in 2-butanone retains its intrinsic nature even after exposure to sunlight for 24 h. The composites of MoO3 nanosheets were used as an electrode material for supercapacitors and showed a high specific capacitance of 201 F·g−1 in a three-electrode configuration at a scan rate of 50 mV·s−1.

scholarly journals Salmonella Typhi and Salmonella Paratyphi A elaborate distinct systemic metabolite signatures during enteric fever

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Elin Näsström ◽  
Nga Tran Vu Thieu ◽  
Sabina Dongol ◽  
Abhilasha Karkey ◽  
Phat Voong Vinh ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Bacterial Infections ◽  
Enteric Fever ◽  
Salmonella Typhi ◽  
Two Dimensional ◽  
Flight Mass Spectrometry ◽  
Metabolite Profiles ◽  
Diagnostic Approaches ◽  
First Time

The host–pathogen interactions induced by Salmonella Typhi and Salmonella Paratyphi A during enteric fever are poorly understood. This knowledge gap, and the human restricted nature of these bacteria, limit our understanding of the disease and impede the development of new diagnostic approaches. To investigate metabolite signals associated with enteric fever we performed two dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC/TOFMS) on plasma from patients with S. Typhi and S. Paratyphi A infections and asymptomatic controls, identifying 695 individual metabolite peaks. Applying supervised pattern recognition, we found highly significant and reproducible metabolite profiles separating S. Typhi cases, S. Paratyphi A cases, and controls, calculating that a combination of six metabolites could accurately define the etiological agent. For the first time we show that reproducible and serovar specific systemic biomarkers can be detected during enteric fever. Our work defines several biologically plausible metabolites that can be used to detect enteric fever, and unlocks the potential of this method in diagnosing other systemic bacterial infections.

Quantum-Confined Optical Interband Transitions in 5-Doped Doping Superlattices

1989 ◽  
Vol 145 ◽  
Author(s):  
E. F. Schubert ◽  
T. D. Harris ◽  
J. E. Cunningham
Keyword(s):  
Emission Spectra ◽  
Doping Profile ◽  
Luminescence Spectra ◽  
Interband Transitions ◽  
Doping Technique ◽  
Quantum Confined ◽  
P Type ◽  
First Time ◽  
Experimental Absorption ◽  
Good Agreement

AbstractOptical absorption and photoluminescence experiments are performed on GaAs doping superlattices, which have a δ-function-like doping profile of alternating n-type and p-type dopant sheets. Absorption and emission spectra reveal for the first time the clear signature of quantum-confined interband transitions. The peaks of the experimental absorption and luminescence spectra are assigned to calculated energies of quantum-confined transitions with very good agreement. It is shown that the employment of the δ-doping technique results in improved optical properties of doping superlattices.

scholarly journals Structural Transitions at Microtubule Ends Correlate with Their Dynamic Properties in Xenopus Egg Extracts

2000 ◽  
Vol 149 (4) ◽  
pp. 767-774 ◽  
Author(s):  
Isabelle Arnal ◽  
Eric Karsenti ◽  
Anthony A. Hyman
Keyword(s):  
Dynamic Instability ◽  
Dynamic Properties ◽  
Microtubule Assembly ◽  
Two Dimensional ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Xenopus Egg Extracts ◽  
First Time ◽  
The Relationship ◽  
Dynamic Populations

Microtubules are dynamically unstable polymers that interconvert stochastically between growing and shrinking states by the addition and loss of subunits from their ends. However, there is little experimental data on the relationship between microtubule end structure and the regulation of dynamic instability. To investigate this relationship, we have modulated dynamic instability in Xenopus egg extracts by adding a catastrophe-promoting factor, Op18/stathmin. Using electron cryomicroscopy, we find that microtubules in cytoplasmic extracts grow by the extension of a two- dimensional sheet of protofilaments, which later closes into a tube. Increasing the catastrophe frequency by the addition of Op18/stathmin decreases both the length and frequency of the occurrence of sheets and increases the number of frayed ends. Interestingly, we also find that more dynamic populations contain more blunt ends, suggesting that these are a metastable intermediate between shrinking and growing microtubules. Our results demonstrate for the first time that microtubule assembly in physiological conditions is a two-dimensional process, and they suggest that the two-dimensional sheets stabilize microtubules against catastrophes. We present a model in which the frequency of catastrophes is directly correlated with the structural state of microtubule ends.

New Hopane Triterpenoids From Lichens in the Family Physiaceae

1989 ◽  
Vol 42 (8) ◽  
pp. 1415 ◽  
Author(s):  
AL Wilkins ◽  
JA Elix ◽  
KL Gaul ◽  
R Moberg
Keyword(s):  
Methyl Ester ◽  
Natural Occurrence ◽  
Two Dimensional ◽  
Triterpene Acid ◽  
The Family ◽  
First Time

Three new hopane triterpenes have been isolated from lichens of the family Physciaceae. Two of the triterpenes, 22-hydroxyhopan-6-one (2) and 6 α-acetoxyhopan-22-ol (1b), have been characterized previously but their natural occurrence is reported for the first time, while a new triterpene acid [ aipolic acid (1c)], was isolated and characterized as the corresponding methyl ester. One- and two-dimensional 1H-1H and 13C-lH correlated n.m.r. studies have revealed methyl aipolate to be methyl 6#945;-acetoxy-22-hydroxyhopan-25-oate (1d).

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