Observation of Configurational Switching of Deep Defects in a-Si:H Using Thermal Step Insertion During Capacitance Transient Measurements

1996 ◽  
Vol 420 ◽  
Author(s):  
Adam D. Gardner ◽  
J. David Cohen
Keyword(s):  
Thermal Emission ◽  
Full Range ◽  
Type A ◽  
Defect States ◽  
The Many ◽  
Capacitance Transient ◽  
Defect Relaxation ◽  
Transient Measurements ◽  
Temperature Switch ◽  
Emission Phase

AbstractIn standard, isothermal capacitance transient measurements, configurational changes in defect states are normally very difficult to identify because, depending on the relative rates of thermal emission to the configurational relaxation, charge will be emitted predominantly from only one configuration. We have found, however, that employing a thermal step during the emission phase of the transient enhances the effect of defect relaxation; one can then observe the resultant switch between distinct configurations. We have applied this method quite successfully to lightly doped n-type a-Si:H samples by varying the overall temperature (between 270K and 350K) and the magnitude of the temperature switch (from 20K to 35K). For the smallest temperature steps, the resultant transients suggest two distinct configurations that, we believe, reflect only a fraction of the many latent configurations that account for the full range of relaxation possible.

Defect Relaxation in a-Si:H Studied by Defect Absorption and Luminescence

1993 ◽  
Vol 297 ◽  
Author(s):  
Daxing Han ◽  
Yang Xiao
Keyword(s):  
Band Gap ◽  
Photon Emission ◽  
Forward Bias ◽  
Emission Spectra ◽  
Energy Position ◽  
Bias Effect ◽  
Band Absorption ◽  
Capacitance Transient ◽  
Defect Relaxation ◽  
Transient Measurements

The experimental results about defect relaxation in a-Si:H have been reported recently on several transient measurements, such as forward-bias-transient-current,1 optical bias effect on electron drift,2 and photo-capacitance transient.3 In this paper we report the steady state results of the bias effect on sub-band-gap absorption and photon-emission spectra measurements in undoped samples.The optical bias effects the sub-band absorption. In additional to an enhancement of the sub-band gap absorption, the absorption threshold moved from 0.8 eV to 0.6 eV for undoped samples under optical bias at room temperature. The effects are larger in the light-soaked-state than in the annealed-state.We also report on the generation rate dependence on photoluminescence (PL) spectra line shape. We found that the energy position of the defect PL band shifted from 1.1 eV to 0.9 eV when the excitation level increased 4,000 times.While motion of the quasi-Fermi level as a explanation cannot be eliminated, defect relaxation seems more plausible.

Exploration of Defect Relaxation Dynamics in Hydrogenated Amorphous Silicon using Temperature Switching Experiments

1994 ◽  
Vol 336 ◽  
Author(s):  
Adam Gardner ◽  
J. David Cohen
Keyword(s):  
Density Of States ◽  
Thermal Emission ◽  
Hydrogenated Amorphous Silicon ◽  
Relaxation Processes ◽  
Relaxation Dynamics ◽  
Temperature Step ◽  
Thermally Activated ◽  
Hydrogenated Amorphous ◽  
Defect Relaxation ◽  
Transient Measurements

ABSTRACTWe have carried out a series of charge transient measurements on a-Si:H in which we insert a double temperature step during the period when electrons are being emitted from deep defects. The behavior of this emitted defect charge is completely inconsistent with any density of states that remains static during the emission; that is, defect relaxation must be invoked. Such measurements allow us to separate the temperature dependence of relaxation from that of thermal emission. In particular, we demonstrate that the emission itself exhibits thermally activated behavior in spite of the ongoing relaxation processes.

Observation of Deep Defect Relaxation Processes in Hydrogenated Amorphous Silicon-Germanium Alloy

1993 ◽  
Vol 297 ◽  
Author(s):  
Fan Zhong ◽  
J.David Cohen
Keyword(s):  
Silicon Germanium ◽  
Thermal Emission ◽  
Relaxation Processes ◽  
Defect States ◽  
Energy Position ◽  
Deep Defect ◽  
Large Phase ◽  
Photocurrent Measurement ◽  
Amorphous Silicon Germanium ◽  
Defect Relaxation

Modulated photocurrent (MPC) spectroscopy has been used to investigate the energy distribution of deep defect states in photo-CVD grown a-Si1 -xGex:H alloys. We observe a distinct electron trapping feature at a thermal energy of 0.55eV below Ec for higher Ge concentration (x = 0.62) alloys. For those samples with Ge concentration between 30-50 at. %, an anomalously large phase shift was observed within a temperature window between 150K to 240K. The modulated photocurrent exhibits strong quenching at the edges of this window. We suggest that these MPC spectra are controlled by deep defect relaxation processes in this temperature region, which causes electron thermal emission processes to be greatly suppressed. This effect can be reduced by increasing the reverse bias. Under such conditions, the energy position of these defect states can be roughly estimated to lie near Ec - 0.33eV. This result supports the recent result obtained from transient photocapacitance and photocurrent measurement.

scholarly journals Clostridium botulinum in soil on the site of the former Metropolitan (Caledonian) Cattle Market, London

1979 ◽  
Vol 83 (2) ◽  
pp. 237-241 ◽  
Author(s):  
G. R. Smith ◽  
R. A. Milligan
Keyword(s):  
Small Proportion ◽  
Clostridium Botulinum ◽  
Type A ◽  
Soil Samples ◽  
Farm Animals ◽  
Clostridium Tetani ◽  
Faecal Contamination ◽  
The Many ◽  
Soil Surveys ◽  
Cattle Market

summarySixty soil samples were collected from the redeveloped site of the former Metropolitan (Caledonian) Cattle Market, Islington, London. Of these, 15 (25%) contained Clostridium botulinum and no less than four types (B, C, D and E) were demonstrated.Early British soil surveys suggested that only 4–8% of samples contained Cl. botulinum (type A or B). Although there can be no absolute proof, it seems likely that the striking prevalence at the Market site was the result of faecal contamination by a small proportion of the many millions of farm animals brought there from elsewhere.The distribution of Clostridium tetani was uneven, but of 18 soil samples taken from one area of the Market site, 16 (89%) were positive.

scholarly journals The General Factor of Psychopathology

2020 ◽  
Vol 16 (1) ◽  
pp. 75-98 ◽  
Author(s):  
Gregory T. Smith ◽  
Emily A. Atkinson ◽  
Heather A. Davis ◽  
Elizabeth N. Riley ◽  
Joshua R. Oltmanns
Keyword(s):  
Mental Health Treatment ◽  
Full Range ◽  
Empirical Support ◽  
Strong Relationship ◽  
General Factor ◽  
General Factor Of Personality ◽  
The Stability ◽  
The Many ◽  
P Factor ◽  
Empirical Approaches

An important advance in understanding and defining mental disorders has been the development of empirical approaches to mapping dimensions of dysfunction and their interrelatedness. Such empirical approaches have consistently observed intercorrelations among the many forms of psychopathology, leading to the identification of a general factor of psychopathology (the p factor). In this article, we review empirical support for p, including evidence for the stability and criterion validity of p. Further, we discuss the strong relationship between p and both the general factor of personality and the general factor of personality disorder, substantive interpretations of p, and the potential clinical utility of p. We posit that proposed substantive interpretations of p do not explain the full range of symptomatology typically included in p. The most plausible explanation is that p represents an index of impairment that has the potential to inform the duration and intensity of a client's mental health treatment.

Effect of Contacts on Capacitance Transient Measurements in N-Type Hydrogenated Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
W. B. Jackson ◽  
N. M. Johnson ◽  
J. Walker
Keyword(s):  
Amorphous Silicon ◽  
Pulse Duration ◽  
Ohmic Contacts ◽  
Hydrogenated Amorphous Silicon ◽  
Charge Injection ◽  
Current Injection ◽  
Anomalous Dependence ◽  
Capacitance Transient ◽  
Hydrogenated Amorphous ◽  
Transient Measurements

ABSTRACTMeasurement of the dependence of emission capacitance transients on filling pulse duration has been extended to devices with Ohmic back contacts. Capacitance transients on devices possessing identical bulk 20-ppm P doped a-Si:H but either Ohmic contacts or blocking contacts were compared. The devices with blocking contacts completely reproduced in quantitative detail the previously observed anomalous dependence of capacitance transients on filling pulse duration. The diodes with Ohmic contacts showed no evidence of the anomalous filling pulse effect even for light-degraded, resistive samples. Current injection measurements show that blocking contacts delay the charge injection into the device by about 10–100 msec.

DIVERSITY AND MEANING IN THE STUDY OF BLACK FATHERHOOD

2016 ◽  
Vol 13 (1) ◽  
pp. 5-23 ◽  
Author(s):  
Maria S. Johnson ◽  
Alford A. Young
Keyword(s):  
Black Men ◽  
Research Agenda ◽  
Full Range ◽  
Black Families ◽  
Cultural Analysis ◽  
Past Century ◽  
Black Fathers ◽  
The Past ◽  
Cultural Expectations ◽  
The Many

AbstractFor the past several decades, numerous studies have focused on the so-called “crisis of Black fatherhood”—that is, the many ways in which Black fathers struggle to fulfill traditional paternal roles and duties. Given major shifts in both the structural conditions and cultural expectations of fatherhood in general over the past century, we argue that it is necessary to reestablish not only what Black fatherhood looks like today—in particular, the internal diversity and dynamism of this category—but also how Black men (as well as other members of Black families and communities) make sense of these changes and meaningfully negotiate their implications. We outline a two-pronged research agenda that: first, identifies gaps in the existing literature that limit our knowledge of the full range of Black fathering practices and experiences; and second, reclaims and repurposes “cultural analysis,” not to pathologize “what’s wrong with Black families and fathers,” but to shed much needed light on the ways in which Black fathers themselves process and make meaning of their roles and realities.

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