Isolation of Temperature Effects on the Kinetics of Light Induced Defect Generation in a-Si:H

1992 ◽  
Vol 258 ◽  
Author(s):  
L. Benatar ◽  
M. Grimbergen ◽  
A. Fahrenbruch ◽  
A. Lopez-Otero ◽  
D. Redfield ◽  
...  
Keyword(s):  
Defect Formation ◽  
Defect Density ◽  
Dark Conductivity ◽  
Stretched Exponential ◽  
Defect Generation ◽  
Thermally Activated ◽  
A Value ◽  
Effects Of Temperature ◽  
Kinetics Of

ABSTRACTData are presented here that show the effects of temperature on the kinetics of metastable defect formation in undoped a-Si:H over the range 45°-110°C. CPM (Constant Photocurrent Method), photoconductivity, and dark conductivity measurements were made and provide independent checks of the defect generation behavior. A stretched exponential description of defect formation as a function of time was used to fit the CPM defect density data. The stretched exponential time constant, τSE, is thermally activated with an apparent activation energy of 1 eV, a value that agrees well with data for defect anneal and solar cell degradation. The data indicate that thermal terms are not negligible for temperatures as low as 45°C, and therefore should be included in any model of the kinetics of defect formation. The role of adistribution of anneal energies and the regimes of dominance of thermal and optical rate terms are discussed in the context of the model.

An Alternative Model for the Kinetics of Light-Induced Defects in A-Si:H

1991 ◽  
Vol 219 ◽  
Author(s):  
Paulo V. Santos ◽  
W. B. Jackson ◽  
R. A. Street
Keyword(s):  
Time Dependence ◽  
Valence Band ◽  
Defect Formation ◽  
Defect Density ◽  
Generation Rate ◽  
Band Tail ◽  
Defect Generation ◽  
Wide Range ◽  
Induced Defects ◽  
Kinetics Of

ABSTRACTThe kinetics of light-induced defect generation in a-Si:H was investigated over a wide range of illumination intensities and temperatures. The defect density around 1016cm-3 exhibits a power-law time dependence Ns ∼ G2εfε with ε = 0.2 to 0.3, where G is the photo-carrier generation rate. A model for the kinetics of defect generation is proposed based on the existence of an exponential distribution of defect formation energies in the amorphous network, associated with the valence band tail states. The model reproduces the observed time dependence of the defect density with an exponent e determined by the exponential width of the valence band tail. The temperature dependence of the defect generation rate is well-reproduced by the model, which provides a connection between the Stabler-Wronski effect and the weak-bond model.

Kinetics of Dopant Metastability in a-Si:H

1992 ◽  
Vol 258 ◽  
Author(s):  
C. E. Nebel ◽  
R. A. Street ◽  
N. M. Johnson ◽  
W. B. Jackson
Keyword(s):  
Thermodynamic Equilibrium ◽  
Opposite Effect ◽  
Dark Conductivity ◽  
Electron Hole ◽  
Small Temperature ◽  
Stretched Exponential ◽  
Thermally Activated ◽  
Hydrogenated Amorphous ◽  
Kinetics Of ◽  
Stretched Exponential Decay

ABSTRACTSmall temperature-induced perturbations from thermodynamic equilibrium of doped hydrogenated amorphous silicon (a-Si:H) are explored by dark conductivity measurements. The equilibration kinetics reveal significant differences between phosphorus and boron doping. Raising the temperature leads to an increase of electron/hole densities which are related to the activation of additional dopants, while a decrease of temperature causes the opposite effect of dopant passivation. The creation kinetics of P doped a-Si:H is stretched exponential with a temperature independent β value of 0.85 whereas dopant passivation in the same temperature range is also stretched exponential decay, but with values for β < 0.8. In contrast, the kinetics of boron activation and passivation are stretched exponential with equal β values. The time constant τ to achieve thermodynamic equilibrium for both activation and passivation is thermally activated with energies ≃ 1.1 eV for P and B doped a-Si:H. τ depends weakly on the degree of perturbation. A discussion and interpretation of the data based on hydrogen migration in a-Si:H is given.

Capacitance and Transient Photocapacitance Studies of Tetrahedral Amorphous Carbon

2000 ◽  
Vol 621 ◽  
Author(s):  
Kimon C. Palinginis ◽  
A. Ilie ◽  
W.I. Milne ◽  
J. David Cohen
Keyword(s):  
Amorphous Carbon ◽  
Urbach Energy ◽  
Defect Density ◽  
Intrinsic Property ◽  
Band Tail ◽  
Junction Capacitance ◽  
Tetrahedral Amorphous Carbon ◽  
Thermally Activated ◽  
A Value ◽  
Defect Densities

ABSTRACTWe have applied junction capacitance and transient photocapacitance measurements to undoped tetrahedral amorphous carbon (ta-C)/silicon carbide (SiC) heterostructures to deduce defect densities and defect distributions in ta-C. The junction capacitance measurements show two thermally activated processes. One can be related to the activation of carriers out of defects at the ta-C/SiC interface while the other one with an activation energy of 0.36eV is an intrinsic property of the ta-C. The defect density at the ta-C/SiC interface is estimated to be roughly 9 ± 2 × 109 cm−2. The transient photocapacitance measurements have allowed us to observe the broader band tail of ta-C, giving a value (Urbach energy) of 230meV.

scholarly journals On the Role of Isothermal Martensite Formation during Cryogenic Treatment of Steels

2020 ◽  
Vol 75 (5) ◽  
pp. 49-72
Author(s):  
Matteo Villa ◽  
Marcel A. J. Somers
Keyword(s):  
Martensitic Transformation ◽  
Cryogenic Treatment ◽  
Time Dependent ◽  
Cryogenic Temperatures ◽  
Martensite Formation ◽  
Steel Microstructure ◽  
Thermally Activated ◽  
Current State ◽  
Kinetics Of

Abstract This contribution addresses the effect of sub-zero Celsius treatments at cryogenic temperatures on the steel microstructure. It is shown that the formation of martensite, including the socalled isothermal, i. e. time dependent or thermally activated, martensitic product, can provide an explanation to the observations in the literature that both the temperature of cryogenic treatment and the holding time at cryogenic temperatures may have an influence on the performance of steel products in service. This review traces the most important stages in the development of cryogenic treatments along the last 95 years and describes it in parallel with the description of the current state of understanding of the kinetics of martensitic transformation in steel. In the last part of the contribution, the new insight is put into context with a practical example where various types of subzero Celsius treatments are applied.

Metastability of Light-Induced Defects in Very Low Density of Gap States α- Si1-αCα:H Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
M. Sebastiani ◽  
P. Fiorini ◽  
F. Alvarez ◽  
F. Pozzilli ◽  
O. Pulci ◽  
...  
Keyword(s):  
Defect Formation ◽  
Defect Density ◽  
Light Exposure ◽  
Bond Breaking ◽  
Silicon Carbon ◽  
Gap States ◽  
Model Conversion ◽  
Induced Defects ◽  
Kinetics Of ◽  
Actual Occupation

ABSTRACTWe have prepared silicon carbon alloys with Tauc's gap of 2.1 eV, low defect density (≃ 3–1015cm-3) and large photoconductivity (αPhoto/αdark=105 in AM 1.5 illumination). On these samples light soaking induces a large number of metastable gap defects which are annealed out at 250 °C. We have studied the kinetics of defect formation varying the duration of light exposure and the light intensity. The experimental data are consistent with a bond breaking model (conversion of tail weak bonds into dangling bonds), provided that the actual occupation of tail states is taken into account.

Metastable Defects in a-Si:H from Bond-length Disorder

1996 ◽  
Vol 420 ◽  
Author(s):  
Qiming li ◽  
R. Biswas
Keyword(s):  
Bond Length ◽  
Defect Formation ◽  
Defect Density ◽  
Relaxation Times ◽  
Thermally Activated ◽  
Equilibrium Defects ◽  
Induced Defects ◽  
Hydrogenated Amorphous ◽  
Good Agreement

AbstractA model of metastable defect formation via H-rebonding in hydrogenated amorphous silicon is developed where the defect density and defect formation energy are controlled by the bond-length disorder of the material. Dangling bond defects are created by H motion from SiH bonds to weak Si-Si bonds. The model predicts formation energies for thermal and light-induced defects in good agreement with experiment. The relaxation of thermal equilibrium defects is stretched exponential, with stretch parameters varying approximately linearly with temperature and relaxation times that are thermally activated- in good agreement with experiment. The annealing of light-induced defect densities also shows relaxation behavior. The model accounts for barriers of ≈ 1.5 eV for H diffusion. The energetics of the H*2 complex will also be discussed. The rms bond-length deviation is a new parameter that controls the quality of the material.

Endangered Butterflies and their Non-Native Host Plants: Examining Shifting Values of Belonging in Restoration

2019 ◽  
Vol 3 (1) ◽  
pp. 1-9
Author(s):  
Robert M. Anderson ◽  
Amy M. Lambert
Keyword(s):  
Ecological Restoration ◽  
Native Species ◽  
Puget Sound ◽  
A Value ◽  
The Social ◽  
Remote Island ◽  
Scientific Truth ◽  
Native Host

The island marble butterfly (Euchloe ausonides insulanus), thought to be extinct throughout the 20th century until re-discovered on a single remote island in Puget Sound in 1998, has become the focus of a concerted protection effort to prevent its extinction. However, efforts to “restore” island marble habitat conflict with efforts to “restore” the prairie ecosystem where it lives, because of the butterfly’s use of a non-native “weedy” host plant. Through a case study of the island marble project, we examine the practice of ecological restoration as the enactment of particular norms that define which species are understood to belong in the place being restored. We contextualize this case study within ongoing debates over the value of “native” species, indicative of deep-seated uncertainties and anxieties about the role of human intervention to alter or manage landscapes and ecosystems, in the time commonly described as the “Anthropocene.” We interpret the question of “what plants and animals belong in a particular place?” as not a question of scientific truth, but a value-laden construct of environmental management in practice, and we argue for deeper reflexivity on the part of environmental scientists and managers about the social values that inform ecological restoration.

Perempuan dan Liminalitas dalam Tradisi Perkawinan Adat di Timor Tengah Selatan

2020 ◽  
Vol 6 (1) ◽  
pp. 114
Author(s):  
Marsel Eliaser Liunokas
Keyword(s):  
Qualitative Research ◽  
Research Method ◽  
Literature Study ◽  
Qualitative Research Method ◽  
South Central ◽  
A Value ◽  
Traditional Marriage ◽  
The Village ◽  
As If

Timorese culture is patriarchal in that men are more dominant than women. As if women were not considered in traditional rituals so that an understanding was built that valued women lower than men. However, in contrast to the article to be studied, this would like to see the priority of women’s roles in traditional marriages in Belle village, South Central Timor. The role of women wiil be seen from giving awards to their parents called puah mnasi manu mnasi. This paper aims to look at the meaning of the rituals of puah mnasi maun mnasi and the role and strengths that women have in traditional marriage rituals in the village of Belle, South Central Timor. The method used for this research is a qualitative research method using interview techniques with a number of people in the Belle Villa community and literature study to strengthen this writing. Based on the data obtained this paper shows that the adat rituals of puah mnasi manu mnasi provide a value that can be learned, namely respect for women, togetherness between the two families, and brotherhood that is intertwined due to customary marital affrairs.

Influence of social networks on business processes’ development

2020 ◽  
Vol 19 (12) ◽  
pp. 2225-2252
Author(s):  
E.V. Popov ◽  
V.L. Simonova ◽  
O.V. Komarova ◽  
S.S. Kaigorodova
Keyword(s):  
Social Networks ◽  
Social Media ◽  
Business Models ◽  
Business Processes ◽  
Digital Economy ◽  
Theoretical Understanding ◽  
Sales Channels ◽  
A Value ◽  
The Impact

Subject. The emergence of new ways of interaction between sellers and buyers, the formation of new sales channels and product promotion based on the use of digital economy tools is at the heart of improving the business processes. Social networks became a tool for development; their rapid growth necessitates theoretical understanding and identification of potential application in enterprise's business process digitalization. Objectives. We explore the role of social media in the digitalization of business processes, systematize the impact of social networks on business processes of enterprises in the digital economy. Methods. The theoretical and methodological analysis of social networks as a tool for digitalization of company's business processes rests on the content analysis of domestic and foreign scientific studies, comparison, generalization and systematization. Results. We highlight the key effects of the impact of social networks on the business processes of the company; show that the digitalization of business processes should be considered in the context of a value-based approach, aimed at creating a value through the algorithmization of company operations. We determine that social networks are one of the most important tools for digitalization of company's business processes, as they have a high organizational and management potential. We also systematize the effects of social media on company's business processes. Conclusions. We present theoretical provisions of the impact of social networks on business processes of enterprises, which will enable to model and organize ideas about the development of digital ecosystems and the formation of business models.

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