Calculations of Some Transport Coefficients in Simple Semiconductors at Low Temperatures and High Electric Fields

1971 ◽  
Vol 49 (7) ◽  
pp. 876-880 ◽  
Author(s):  
Jyoti Kamal ◽  
Satish Sharma
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Low Temperatures ◽  
Transport Coefficients ◽  
Drift Mobility ◽  
Temperature Dependent ◽  
Hall Constant ◽  
The Difference ◽  
High Electric Fields ◽  
Model Semiconductor

In this paper the authors have calculated Hall mobility, drift mobility, and Hall constant for a non-degenerate simple model semiconductor at low temperatures for an arbitrary electric field strength. Following Paranjape the modified distribution of phonons has been taken into account. The difference between the calculations of transport coefficients made by taking into account the modified phonon distribution and by not taking it into account is quite appreciable at high electric field. Calculations also show that for Ne = 1016/cm3 the mobility of electrons remains temperature dependent.

scholarly journals Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

2021 ◽  
Vol 11 (8) ◽  
pp. 3317
Author(s):  
C.S. Quintans ◽  
Denis Andrienko ◽  
Katrin F. Domke ◽  
Daniel Aravena ◽  
Sangho Koo ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Level ◽  
Wet Chemical Synthesis ◽  
Single Molecule Junctions ◽  
Tunnelling Microscopy ◽  
The Difference

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

High Field Electron Drift in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
Qing Gu ◽  
Eric A. Schiff ◽  
Jean Baptiste Chevrier ◽  
Bernard Equer
Keyword(s):  
Electric Fields ◽  
High Field ◽  
Drift Mobility ◽  
Time Range ◽  
Electron Drift ◽  
Parameter Change ◽  
Transient Photocurrent ◽  
Field Mobility ◽  
High Electric Fields ◽  
Electron Drift Mobility

We have measured the electron drift mobility in a-Si:H at high electric fields (E ≤ 3.6 x 105 V%cm). The a-Si:Hpin structure was prepared at Palaiseau, and incorporated a thickp+ layer to retard high field breakdown. The drift mobility was obtained from transient photocurrent measurements from 1 ns - 1 ms following a laser pulse. Mobility increases as large as a factor of 30 were observed; at 77 K the high field mobility de¬pended exponentially upon field (exp(E/Eu), where E u= 1.1 x 105 V%cm). The same field dependence was observed in the time range 10 ns – 1 μs, indicating that the dispersion parameter change with field was negligible. This latter result appears to exclude hopping in the exponential conduction bandtail as the fundamental transport mechanism in a-Si:H above 77 K; alternate models are briefly discussed.

Effect of a High Electric Field on the Thermal and Phase Change Characteristics of an Impacting Drop

2019 ◽  
Author(s):  
Abhishek Basavanna ◽  
Prajakta Khapekar ◽  
Navdeep Singh Dhillon
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Phase Change ◽  
Electric Fields ◽  
High Speed ◽  
Impact Behavior ◽  
Liquid Drops ◽  
Active Interest ◽  
Post Impact ◽  
High Electric Fields

Abstract The effect of applied electric fields on the behavior of liquids and their interaction with solid surfaces has been a topic of active interest for many decades. This has important implications in phase change heat transfer processes such as evaporation, boiling, and condensation. Although the effect of low to moderate voltages has been studied, there is a need to explore the interaction of high electric fields with liquid drops and bubbles, and their effect on heat transfer and phase change. In this study, we employ a high speed optical camera to study the dynamics of a liquid drop impacting a hot substrate under the application of high electric fields. Experimental results indicate a significant change in the pre- and post-impact behavior of the drop. Prior to impact, the applied electric field elongates the drop in the direction of the electric field. Post-impact, the recoil phase of the drop is significantly affected by charging effects. Further, a significant amount of micro-droplet ejection is observed with an increase in the applied voltage.

OBIC Analysis of Different Edge Terminations of Planar 1.6 kV 4H-SiC Diodes

2007 ◽  
Vol 556-557 ◽  
pp. 1007-1010 ◽  
Author(s):  
Christophe Raynaud ◽  
Daniel Loup ◽  
Phillippe Godignon ◽  
Raul Perez Rodriguez ◽  
Dominique Tournier ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Breakdown Voltage ◽  
High Voltage ◽  
Semiconductor Devices ◽  
Optical Beam ◽  
Induced Current ◽  
Bipolar Diodes ◽  
High Electric Fields ◽  
Optical Beam Induced Current

High voltage SiC semiconductor devices have been successfully fabricated and some of them are commercially available [1]. To achieve experimental breakdown voltage values as close as possible to the theoretical value, i.e. value of the theoretical semi-infinite diode, it is necessary to protect the periphery of the devices against premature breakdown due to locally high electric fields. Mesa structures and junction termination extension (JTE) as well as guard rings, and combinations of these techniques, have been successfully employed. Each of them has particular drawbacks. Especially, JTE are difficult to optimize in terms of impurity dose to implant, as well as in terms of geometric dimensions. This paper is a study of the spreading of the electric field at the edge of bipolar diodes protected by JTE and field rings, by optical beam induced current.

scholarly journals Use of Transport Coefficients to Calculate Properties of Electrode Sheaths of Electric Arcs

1997 ◽  
Vol 50 (3) ◽  
pp. 539 ◽  
Author(s):  
J. J. Lowke ◽  
J. C. Quartel
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Cathode Surface ◽  
Transport Coefficients ◽  
Electric Arcs ◽  
Charge Effects ◽  
Positive Ions ◽  
Thermionic Cathodes ◽  
Principal Source ◽  
Electrode Sheath

Particle conservation equations for electrons and positive ions, together with Poisson"s equation to account for space-charge effects on the electric field, have been solved for the electrode sheath regions of electric arcs. For thermionic cathodes and the anode, we find that the ambipolar diffusion approximation is generally valid. At the surface of the anode we find that there is generally a small retarding electric field. For non-thermionic cathodes and no ionisation due to the electric field in the sheath, we calculate unrealistically high sheath voltages and even then, find that the electric fields at the cathode surface are insufficient for field emission. It is suggested that photoionisation in the region close to the cathode may be a principal source of electrons for non-thermionic cathodes.

scholarly journals Corona at Large Coated Electrodes

2018 ◽  
Author(s):  
Mats Larsson ◽  
Olof Hjortstam ◽  
Håkan Faleke ◽  
Liliana Arevalo ◽  
Dong Wu ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Negative Polarity ◽  
Electrode Geometry ◽  
Positive Polarity ◽  
Electrical Fields ◽  
Insulating Material ◽  
Air Gaps ◽  
High Electric Fields ◽  
Coated Electrodes

<p>In geometries relevant form HVDC applications where large electrodes and large air gaps are utilized, the observed corona can be quite different from geometries studied in the literature where needles or wires are used as high voltage electrodes. Corona discharges at large electrodes often initiates when the electric field on the electrode surface appears lower than the critical electric field strength, 2.4 kV/mm. Surface contamination of the electrode has been pointed out as the reason for such discharge events. Our experimental results indicate that one possible way to prevent such corona is to coat the electrode with an insulating material, such as epoxy or oxide layers. It seems that the layer separates any corona inducing particle from the electrode, which in turn hinders the corona to form. However, as the layer breaks down and gets punctured, the corona preventing propertied disappears and corona forms easily. We conclude that as long as the layer doesn’t get punctured, coating electrodes with insulating material is preventing corona to initiate at electrical fields below the critical electric field, as given by the electrode geometry. In contrast to positive polarity, for negative polarity the epoxy coating could withstand high electric fields without breaking down.</p>

Electric Conductance

1997 ◽  
Author(s):  
C. B. Li
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Colloidal Particles ◽  
Free Solution ◽  
Soil Particles ◽  
Electric Conductance ◽  
Variable Charge ◽  
Ac Electric Fields ◽  
The Difference ◽  
Variable Charge Soils

The migration of colloidal soil particles in an applied electric field has been discussed in Chapter 7. Soil particles carrying electric charges invariably adsorb equivalent amounts of ions of the opposite charge. Generally there is a certain amount of free ions present in soil solution. When an electric field is applied to a soil system, a phenomenon known as electric conductance occurs. As in the case for electrolyte solutions, soil particles and various ions interact with one another during their migration, and these interactions can affect the electric conductance of the system. Variable charge soils carry both positive and negative surface charges, and it can be expected that their interactions with various ions would be rather complicated during conductance. On the other hand, this makes the measurement of electric conductance an effective means in elucidating the mechanisms of interactions between variable charge soils and ions. Both direct-current (DC) electric fields and alternating-current (AC) electric fields can induce the migration of charged particles. In the latter case, the migration of these particles should be related to the frequency of the applied AC electric field. Therefore, in this chapter, after describing the principles of electric conductance of ions and colloids and the factors that affect the conductance of a soil, emphasis shall be placed on the interaction between variable charge soils and various ions as reflected by the frequency effect in electric conductance. For a colloidal suspension, the electric conductance may be regarded as the contribution of conductances of both charged colloidal particles and ions. These two parts may be called the electric conductance of colloidal panicles and the electric conductance of ions, respectively. However, in actual cases it is difficult to distinguish between these two parts. Therefore, it is a general practice to distinguish the electric conductance as that caused by colloidal particles plus their counterions from that caused by ions of the free solution. These may be called electric conductance of the colloid and electric conductance of the free solution. The former conductance is the difference between the electric conductance of the suspension and that of the free solution.

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