Interpretation of the absorption spectra of incompletely relaxed electrons in polar liquids as a direct measure of the energetic distribution of band-tail localized states

1988 ◽  
Vol 92 (22) ◽  
pp. 6454-6456 ◽  
Author(s):  
C. Houee-Levin ◽  
J. P. Jay-Gerin
Keyword(s):  
Absorption Spectra ◽  
Localized States ◽  
Direct Measure ◽  
Band Tail ◽  
Polar Liquids

Phosphorous and Boron Incorporation and its Effect on Optical Properties of Ge:H and Si0.01Ge0.99:HFilms Deposited by LF PECVD

2012 ◽  
Vol 1372 ◽  
Author(s):  
Nery Delgadillo ◽  
Andrey Kosarev ◽  
Afonso Torres ◽  
Lancelot Garcia ◽  
Brian Gonzales
Keyword(s):  
Gas Phase ◽  
Secondary Ion Mass Spectrometry ◽  
Solid Phase ◽  
Chemical Vapour ◽  
Low Frequency ◽  
Localized States ◽  
Optical Measurements ◽  
Band Tail ◽  
Frequency Plasma ◽  
Secondary Ion

ABSTRACTDeposition conditions that provided low absorption related to both band tail and deep localized states have been found for both materials Ge:H and Si1YGeY:H. Phosphorous incorporation on Si0.01Ge0.99:H films and boron incorporation on Ge:H films were deposited by low frequency plasma-enhanced chemical vapour deposition (LF PECVD). The phosphorous incorporation in solidphase was observed to preferential with the increase of the doping in the gas phase to 2.5 %, and 2.5% to 4% was observed preferential Si0.01Ge0.99 film, boron incorporation in solid phase increase linearly with the increase of the doping gas phase. The content of solid phase was characterized by Secondary ion mass spectrometry (SIMS) profiling. Hydrogen concentration in the films was determined from Fourier transform infrared spectroscopy (FTIR) and SIMS measurements. Optical measurements provided optical gap, localized states, and band tail. A significant reduction of both band tail and deep localized states were observed at boron incorporation in solid phase = 0.004% on Ge:H films and the same were observed at phosphorous incorporation in solid phase = 0.29% on Si0.01Ge0.99:H films.

L'ion positif géminé intervient-il sur le destin de l'électron piégé incomplètement relaxé dans les liquides polaires irradiés?

1992 ◽  
Vol 70 (6) ◽  
pp. 1869-1871
Author(s):  
J.-P. Jay-Gerin ◽  
C. Ferradini
Keyword(s):  
Absorption Spectrum ◽  
Optical Absorption ◽  
Coulomb Field ◽  
Early Time ◽  
Localized States ◽  
Polar Liquids ◽  
Time Dynamics ◽  
Electron Solvation ◽  
Trapped Electron ◽  
Positive Ion

A model is proposed concerning the influence of the parent positive ion on the fate of the incompletely relaxed trapped electron (eir−) in irradiated polar liquids. This model is based on the release, by a tunneling and (or) a trap-hopping mechanism in the Coulomb field of the cation, of the electrons captured in preexisting shallow localized states below the bottom of the conduction band of the solvent. The released electrons would either recombine with the parent positive ion or get retrapped. The net effect would be an accumulation of electrons in deeper traps. The removal of weakly trapped electrons would contribute to the decrease of the infrared part of the optical absorption spectrum during the very early time dynamics of electron solvation. Such a process would imply, as a consequence, the existence of a maximum of the eir− absorption spectrum.

Temperature Dependence of 1/f Noise and Electrical Conductivity Measurements on p-type a-Si:H Devices

2013 ◽  
Vol 1536 ◽  
pp. 181-186 ◽  
Author(s):  
V. C. Lopes ◽  
E. Hanson ◽  
D. Whitfield ◽  
K. Shrestha ◽  
C. L. Littler ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Temperature Dependence ◽  
Valence Band ◽  
Hole Mobility ◽  
Type A ◽  
Localized States ◽  
Conductivity Measurements ◽  
Band Tail ◽  
Resistance Change ◽  
P Type

ABSTRACTNoise and electrical conductivity measurements were made at temperatures ranging from approximately 270°K to 320°K on devices fabricated on as grown Boron doped p-type a-Si:H films. The room temperature 1/f noise was found to be proportional to the bias voltage and inversely proportional to the square root of the device area. As a result, the 1/f noise can be described by Hooge’s empirical expression [1]. The 1/f noise was found to be independent of temperature in the range investigated even though the device conductivity changed by a factor of approximately 4 over this range. Conductivity temperature measurements exhibit a T-0.25 dependence, indicative of conduction via localized states in the valence band tail [2,3]. In addition, multiple authors have analyzed hole mobility in a-Si:H and find that the hole mobility depends on the scattering of mobile holes by localized states in the valence band tail [4-7]. We conclude that the a-Si:H carrier concentration does not change appreciably with temperature, and thus, the resistance change in this temperature range is due to the temperature dependence of the hole mobility. Our results are applicable to a basic understanding of noise and conductivity requirements for a-Si:H materials used for microbolometer ambient temperature infrared detection.

Thickness Effects on the Activation Energy of Source-Drain Current in P and N Channel Polycrystalline Silicon Thin Film Transistors

1990 ◽  
Vol 182 ◽  
Author(s):  
Babar A. Khan ◽  
Ranjana Pandya
Keyword(s):  
Thin Film ◽  
Activation Energy ◽  
Thin Film Transistors ◽  
Drain Current ◽  
Localized States ◽  
Subthreshold Slope ◽  
Band Tail ◽  
Silicon Thin Film ◽  
Sharp Drop ◽  
P Type

AbstractWe report activation energy measurements of the source-drain current of polysilicon thin film transistors (TFTs). We have shown earlier that measurements carried out on unhydrogenated TFTs can be explained by the presence of band tail states in addition to deep localized states. After hydrogenation, the density of band tail states is greatly reduced and the data can be fitted with only the deep states.In the present work we have studied both n and p channel TFTs. This was done by measuring both type of devices on the same wafer so that differences due to processing conditions could be ruled out. Both type of devices had intentionally undoped channels and were identical except for the n or p type source-drain regions. The thinner TFTs discussed in this work have a sharper drop in the activation energy than would be expected from idealized calculations. This sharp drop in activation energy is also an indication of a sharp subthreshold slope. This decrease in subthreshold slope (Volts/decade) is due to the complete depletion of the channel polysilicon, which leads to a rapid increase (or decrease) in the surface potential as a function of the gate voltage.

A pulse radiolysis study of solvated electrons in dilute solutions of polar liquids in nonpolar solvents

1977 ◽  
Vol 55 (11) ◽  
pp. 1996-2002 ◽  
Author(s):  
J. H. Baxendale
Keyword(s):  
Absorption Spectra ◽  
Pulse Radiolysis ◽  
Electron Pulse ◽  
Pulse Irradiation ◽  
Dilute Solutions ◽  
Solvated Electrons ◽  
Polar Liquids ◽  
Tert Butanol ◽  
Nonpolar Solvents ◽  
Existence Of Equilibria

Measurements of the conductivities following electron pulse irradiation of dilute solutions of ethanol, n-propanol, tert-butanol, or dimethyl sulphoxide in n-hexane, cyclohexane, or i-octane are quantitatively consistent with the existence of equilibria between electrons in the hydrocarbon and electrons solvated by dimers of the polar molecules. With dimethylformamide solutions in alkanes the equilibrium could be with the monomeric anion of the solute but this assignment is not unequivocal. Absorption spectra of es− in n-hexane solutions of ethanol and of tert-butanol have been obtained.

Examination of the Defect Pool Model by An Improved Analysis of the Constant Photocurrent Method

1995 ◽  
Vol 377 ◽  
Author(s):  
Helmut Stiebig ◽  
Frank Siebke
Keyword(s):  
Valence Band ◽  
Defect Density ◽  
Localized States ◽  
Optical Transitions ◽  
Defect States ◽  
Band Tail ◽  
Defect Distribution ◽  
Density Of Localized States ◽  
Pool Model ◽  
Extended States

ABSTRACTWe have developed an improved analysis of constant photocurrent method (CPM) data. It is based on a numerical simulation of CPM spectra taking into account the full set of optical transitions between localized and extended states, capture and emission processes as well as the position of the Fermi level. Comparing measured and simulated CPM spectra provides information about the density of localized states in a-Si:H, i.e. the valence band tail, the integrated defect density, the energy distribution and the charge state of defect states. Based on these results we examine the predictions of the defect-pool model. The defect distribution in undoped and doped a-Si:H can be described by the defect-pool model taking into account the doping level dependence of principal parameters including the valence band tail, the equilibration temperature, and the width of the defect-pool.

Redox Properties of Platinum Uracil "Blues": A New Type of Paramagnetic Species

1981 ◽  
Vol 36 (2) ◽  
pp. 272-274 ◽  
Author(s):  
M. Seul ◽  
H. Neubacher ◽  
W. Lohmann
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Redox Properties ◽  
Localized States ◽  
Paramagnetic Species ◽  
Optical Absorption Spectra ◽  
Esr Spectrum ◽  
New Type ◽  
Characteristic Features

Abstract The observation of a new type of ESR spectrum in the course of redox experiments on a platinum uracil "blue" compound is reported. Some characteristic features of the ESR and optical absorption spectra are described. A tentative analysis of the ESR spectrum is pre-sented, based on the assumption of localized states.

Electronic Properties of Microcrystalline Silicon investigated by Photoluminescence Spectroscopy on Films and Devices

2003 ◽  
Vol 762 ◽  
Author(s):  
R. Carius ◽  
T. Merdzhanova ◽  
F. Finger
Keyword(s):  
Electronic Properties ◽  
Crucial Role ◽  
Film Growth ◽  
Photoluminescence Spectroscopy ◽  
Localized States ◽  
Micro Structure ◽  
Microcrystalline Silicon ◽  
Band Tail ◽  
Hydrogen Dilution ◽  
Silane Concentration

AbstractPhotoluminescence spectroscopy has been applied to investigate localized states in microcrystal-line silicon (μc-Si:H) films and to address the problem of the changes of the electronic properties of this material upon changes of the hydrogen dilution during film growth. By a comparison of photoluminescence and Raman spectra on device grade sample series prepared at different silane concentration in hydrogen (SC) by PE-CVD and HW-CVD a correlation between the micro-structure and the photoluminescence energy is found. It is proposed that the density of band tail states is reduced with increasing SC leading to the increase of the PL energy as well as to the increase of Voc of solar cells. The reason for the tails and their reduction is not clear but strain might play a crucial role and the amorphous hydrogenated phase might be effective for strain reduction.

Numerical Simulation of the Transient Photoconductivity in A-SI:H as a Function of the Excitation Density

1997 ◽  
Vol 467 ◽  
Author(s):  
H. Feist ◽  
M. Kunst
Keyword(s):  
Density Dependence ◽  
Conduction Band ◽  
Dynamic Equilibrium ◽  
Localized States ◽  
Time Range ◽  
Excitation Density ◽  
Band Tail ◽  
Transient Photoconductivity ◽  
Excess Electrons ◽  
Short Time

ABSTRACTThe dependence of the transient photoconductivity induced by pulsed excitation (TPC) on the excitation density is discussed with the help of numerical simulations. It is shown that recombination between excess mobile electrons and all excess holes (mainly localized) can explain the excitation density dependence of the TPC amplitude of standard a-Si:H at room temperature using a rate parameter kBB of 10−8cm3/s. This model leads to a decay faster than experimentally observed in the time range from 40ns to 1 μs. A variation of the recombination model is presented that gives a better fit for the longer time range still showing the correct excitation density dependence in the short time range. Moreover comparison of the simulations with experimental data yields limits for the parameters of the conduction band tail. In particular, the time necessary to establish a dynamic equilibrium of excess electrons between delocalized states in the conduction band and localized states in the tail appears to be very informative.

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