Perspective on construction of heterojunction photocatalysts and the complete utilization of photogenerated charge carriers

Environmental SEM operate at specimen chamber pressures of ∼20 torr (2.7 kPa) allowing stabilization of liquid water at room temperature, working on rugged insulators, and generation of an environmental secondary electron (ESE) signal. All signals available in conventional high vacuum instruments are also utilized in the environmental SEM, including BSE, SE, absorbed current, CL, and X-ray. In addition, the ESEM allows utilization of the flux of charge carriers as information, providing exciting new signal modes not available to BSE imaging or to conventional high vacuum SEM.In the ESEM, at low vacuum, SE electrons are collected with a “gaseous detector”. This detector collects low energy electrons (and ions) with biased wires or plates similar to those used in early high vacuum SEM for SE detection. The detector electrode can be integrated into the first PLA or positioned at any other place resulting in a versatile system that provides a variety of surface information.

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Direct imaging of charge transfer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165860 ◽

1996 ◽

Vol 54 ◽

pp. 680-681

Author(s):

Yimei Zhu ◽

J. Tafto

Keyword(s):

Charge Transfer ◽

Electron Diffraction ◽

Scattering Amplitude ◽

High Temperature Superconductors ◽

Charge Carriers ◽

Image Charge ◽

Net Charge ◽

Long Time ◽

Electron Holes ◽

First Time

The electron holes confined to the CuO2-plane are the charge carriers in high-temperature superconductors, and thus, the distribution of charge plays a key role in determining their superconducting properties. While it has been known for a long time that in principle, electron diffraction at low angles is very sensitive to charge transfer, we, for the first time, show that under a proper TEM imaging condition, it is possible to directly image charge in crystals with a large unit cell. We apply this new way of studying charge distribution to the technologically important Bi2Sr2Ca1Cu2O8+δ superconductors.Charged particles interact with the electrostatic potential, and thus, for small scattering angles, the incident particle sees a nuclei that is screened by the electron cloud. Hence, the scattering amplitude mainly is determined by the net charge of the ion. Comparing with the high Z neutral Bi atom, we note that the scattering amplitude of the hole or an electron is larger at small scattering angles. This is in stark contrast to the displacements which contribute negligibly to the electron diffraction pattern at small angles because of the short g-vectors.

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The outlook for the development of radiation sources in the middle-IR range based on the intraband transitions between the energy levels of charge carriers in injection laser heterostructures with quantum dots and wells

Uspekhi Fizicheskih Nauk ◽

10.3367/ufnr.0169.199904g.0459 ◽

1999 ◽

Vol 169 (4) ◽

pp. 459 ◽

Cited By ~ 1

Author(s):

L.E. Vorob'ev ◽

D.A. Firsov ◽

V.A. Shalygin ◽

V.N. Tulupenko ◽

N.N. Ledentsov ◽

...

Keyword(s):

Quantum Dots ◽

Energy Levels ◽

Injection Laser ◽

Charge Carriers ◽

Laser Heterostructures ◽

Radiation Sources

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Laser Engineering of Barrier Structures Based on Solid Solution ZnCdHgTe.

MRS Proceedings ◽

10.1557/proc-719-f8.35 ◽

2002 ◽

Vol 719 ◽

Author(s):

Galina Khlyap

Keyword(s):

Room Temperature ◽

Film Surface ◽

Charge Carriers ◽

Barrier Structure ◽

Free Charge ◽

Current Voltage ◽

Capacitance Voltage ◽

Laser Engineering ◽

Charged Defects ◽

Epilayer Surface

AbstractRoom-temperature electric investigations carried out in CO2-laser irradiated ZnCdHgTe epifilms revealed current-voltage and capacitance-voltage dependencies typical for the metal-semiconductor barrier structure. The epilayer surface studies had demonstrated that the cell-like relief has replaced the initial tessellated structure observed on the as-grown samples. The detailed numerical analysis of the experimental measurements and morphological investigations of the film surface showed that the boundaries of the cells formed under the laser irradiation are appeared as the regions of accumulation of derived charged defects of different type of conductivity supplying free charge carriers under the applied electric field.

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Effect of Illumination on Organic Polymer Thin-Film Transistors

MRS Proceedings ◽

10.1557/proc-771-l10.17 ◽

2003 ◽

Vol 771 ◽

Cited By ~ 3

Author(s):

Michael C. Hamilton ◽

Sandrine Martin ◽

Jerzy Kanicki

Keyword(s):

Thin Film ◽

Thin Film Transistors ◽

Drain Current ◽

Charge Carriers ◽

Electrical Performance ◽

Organic Polymer ◽

Light Illumination ◽

Polymer Thin Film ◽

Channel Region ◽

White Light Illumination

AbstractWe have investigated the effects of white-light illumination on the electrical performance of organic polymer thin-film transistors (OP-TFTs). The OFF-state drain current is significantly increased, while the drain current in the strong accumulation regime is relatively unaffected. At the same time, the threshold voltage is decreased and the subthreshold slope is increased, while the field-effect mobility of the charge carriers is not affected. The observed effects are explained in terms of the photogeneration of free charge carriers in the channel region due to the absorbed photons.

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Relation Between Local Structure, Electric Dipole and Charge Carrier Dynamics in DHICA Melanin, a Model for Biocompatible Semiconductors

10.26434/chemrxiv.11323016 ◽

2019 ◽

Author(s):

Micaela Matta ◽

Alessandro Pezzella ◽

Alessandro Troisi

Keyword(s):

Electronic Structure ◽

Degrees Of Freedom ◽

Structural Model ◽

Computational Study ◽

Oxidative Polymerization ◽

Radical Scavenging ◽

Charge Carriers ◽

Electronic Charge ◽

Polymer Semiconductors ◽

Synthetic Pigments

<div><div><div><p>Eumelanins are a family of natural and synthetic pigments obtained by oxidative polymerization of their natural precursors: 5,6 dihydroxyindole and its 2-carboxy derivative (DHICA). The simultaneous presence of ionic and electronic charge carriers makes these pigments promising materials for applications in bioelectronics. In this computational study we build a structural model of DHICA melanin considering the interplay between its many degrees of freedom, then we examine the electronic structure of representative oligomers. We find that a non-vanishing dipole along the polymer chain sets this system apart from conventional polymer semiconductors, determining its electronic structure, reactivity toward oxidation and localization of the charge carriers. Our work sheds light on previously unnoticed features of DHICA melanin that not only fit well with its radical scavenging and photoprotective properties, but open new perspectives towards understanding and tuning charge transport in this class of materials.<br></p></div></div></div>

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