scholarly journals The Combined Influence of Dopant Species and Surface Termination on the Electronic Properties of Diamond Surfaces

2020 ◽  
Vol 6 (2) ◽  
pp. 22 ◽  
Author(s):  
Karin Larsson
Keyword(s):  
Electron Emission ◽  
Electronic Structures ◽  
Theoretical Calculations ◽  
Diamond Surface ◽  
Diamond Surfaces ◽  
Surface Termination ◽  
Substitutional Doping ◽  
B Doping ◽  
High Level ◽  
Almost All

The combined effects of geometrical structure and chemical composition on the diamond surface electronic structures have been investigated in the present study by using high-level theoretical calculations. The effects of diamond surface planes [(111) vs. (100)], surface terminations (H, F, OH, Oontop, Obridge, vs. NH2), and substitutional doping (B, N vs. P), were of the largest interest to study. As a measure of different electronic structures, the bandgaps, work functions, and electron affinities have been used. In addition to the effects by the doping elements, the different diamond surface planes [(111) vs. (100)] were also observed to cause large differences in the electronic structures. With few exceptions, this was also the case for the surface termination species. For example, Oontop-termination was found to induce surface electron conductivities for all systems in the present study (except for a non-doped (100) surface). The other types of surface terminating species induced a reduction in bandgap values. The calculated bandgap ranges for the (111) surface were 3.4–5.7 (non-doping), and 0.9–5.3 (B-doping). For the (100) surface, the ranges were 0.9–5.3 (undoping) and 3.2–4.3 (B-doping). For almost all systems in the present investigation, it was found that photo-induced electron emission cannot take place. The only exception is the non-doped NH2-terminated diamond (111) surface, for which a direct photo-induced electron emission is possible.

Secondary Electron Emission Spectroscopy of Crystalline and Non-Crystalline Carbon Allotropes

1990 ◽  
Vol 201 ◽  
Author(s):  
Alon Hoffman ◽  
Steven Prawer
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Ion Irradiation ◽  
Quartz Substrate ◽  
Natural Diamond ◽  
Pyrolytic Graphite ◽  
Secondary Electron Emission ◽  
Diamond Surface ◽  
Diamond Surfaces ◽  
Diamond Thin Film

AbstractThe Secondary Electron Emission (SEE) spectra of type Ha diamond, highly oriented pyrolytic graphite (HOPG), amorphous carbon (e-beam evaporated), glassy carbon and amorphic-diamond (filtered arc evaporated) were measured in the 0–80 eV electron kinetic energy range, and found to be very distinctive for the different carbon allotropcs. The sensitivity of SEE spectroscopy to crystal damage for the type Ha diamond surface was studied by performing SEE measurements as function of 1 keV argon ion irradiation dose. Two examples of the use of SEE in the characterization of diamond surfaces are presented. In the first, the crystalline quality of the back and front surfaces of a chemically vapour deposited diamond thin film which had dclaminated from a fused quartz substrate were compared using SEE and, in the second, SEE was used to provide a qualitative estimate of the damage induced by mechanical polishing of a natural diamond surface.

scholarly journals A Theoretical Study of the Energetic Stability and Electronic Structure of Terminated and P-Doped Diamond (100)-2x1 Surfaces

2019 ◽  
Vol 3 (3) ◽  
Keyword(s):  
Electronic Structure ◽  
Work Function ◽  
Band Gap ◽  
Density Functional ◽  
Diamond Surface ◽  
Strong Impact ◽  
Diamond Surfaces ◽  
Surface Termination ◽  
Donor And Acceptor ◽  
Gap States

The combined effect of P-doping and surface-termination on the energetics, and especially the electronic structure, of a diamond (100) surface, has in the present study been investigated by using a Density Functional Theory method. The diamond surface was terminated with any of the following species: H, F, OH, Obridge and NH2 . These adsorbates have earlier experimentally been proven crucial for e.g. applications based on surface electrochemistry. The observed results were analysed with the purpose to obtain a deeper knowledge about the atomic-level cause to the observed effects by the P doping and surface termination. The P dopant was found to have a very minor influence on the averaged adsorption energy for the various terminating species (i.e. with less than 0.17 eV). Moreover, the adsorbates were found to reduce the stability of the P-dopant in the diamond lattice. When analysing the results of the calculated partial density of states, the P dopant was found to contribute with band gap states below the conduction band, out of which one is a donor band. In addition, the surfaces with their terminating species will contribute with empty band gap states just below the CBM of the diamond surfaces. Hence, the combination of P doping and surface termination will induce both donor and acceptor states in the diamond surface band gap, which will improve the usefulness of these specific diamond surfaces in various electronic devices. The work function of a diamond surface is one specific properties that will be affected by substitutional doping and surface termination. Within the present study, the terminating species were found to render a strong impact on the surface work function (as compared to a non-terminated diamond (100)-2x1 surface), with calculated work function values that were even further decreased by P-doping.

DFT Benchmark Study of the O--O Bond Dissociation Energy in Peroxides Validated with High-Level Ab-Initio Calculations

2019 ◽  
Author(s):  
Danilo Carmona ◽  
Pablo Jaque ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Reference Value ◽  
Basis Set ◽  
Basis Sets ◽  
Mean Deviation ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
The Mean ◽  
Experimental Values ◽  
High Level ◽  
Almost All

<div><div><div><p>Peroxides play a central role in many chemical and biological pro- cesses such as the Fenton reaction. The relevance of these compounds lies in the low stability of the O–O bond which upon dissociation results in radical species able to initiate various chemical or biological processes. In this work, a set of 64 DFT functional-basis set combinations has been validated in terms of their capability to describe bond dissociation energies (BDE) for the O–O bond in a database of 14 ROOH peroxides for which experimental values ofBDE are available. Moreover, the electronic contributions to the BDE were obtained for four of the peroxides and the anion H2O2− at the CBS limit at CCSD(T) level with Dunning’s basis sets up to triple–ζ quality provid- ing a reference value for the hydrogen peroxide anion as a model. Almost all the functionals considered here yielded mean absolute deviations around 5.0 kcal mol−1. The smallest values were observed for the ωB97 family and the Minnesota M11 functional with a marked basis set dependence. Despite the mean deviation, order relations among BDE experimental values of peroxides were also considered. The ωB97 family was able to reproduce the relations correctly whereas other functionals presented a marked dependence on the chemical nature of the R group. Interestingly, M11 functional did not show a very good agreement with the established order despite its good performance in the mean error. The obtained results support the use of similar validation strategies for proper prediction of BDE or other molecular properties by DF Tmethods in subsequent related studies.</p></div></div></div>

Methyl mercury in the dutch rhine delta

1994 ◽  
Vol 30 (10) ◽  
pp. 213-219 ◽  
Author(s):  
Hendrik Pieters ◽  
Victor Geuke
Keyword(s):  
Suspended Matter ◽  
Methyl Mercury ◽  
Mercury Contamination ◽  
Benthic Organisms ◽  
Considerable Decrease ◽  
Continuous Sedimentation ◽  
Highly Correlated ◽  
High Level ◽  
Almost All

Samples of yellow eel from various locations in the Dutch Rhine area have been analyzed for trend monitoring of mercury since 1977. In the western Rhine delta mercury levels in eels have hardly changed since the seventies, whereas in the eastern part of the Dutch Rhine area a considerable decrease of mercury concentrations in eel has occurred. Because of continuous sedimentation of contaminated suspended matter transported from upstream regions, accumulation rates and concentrations of mercury in eel in the western Rhine delta remained at a relatively high level. Analyses of methyl mercury in biota have been performed to elucidate the role of methyl mercury in the mercury contamination of the Dutch Rhine ecosystem. Low percentages of methyl mercury were observed in zooplankton (3 to 35%). In benthic organisms (mussels) percentages of methyl mercury ranged from 30 to 57%, while in fish species and liver of aquatic top predator birds almost all the mercury was present in the form of methyl mercury (&gt; 80%). During the period 1970-1990 mercury concentrations of suspended matter in the eastern Rhine delta have drastically decreased. These concentrations seemed to be highly correlated with mercury concentrations of eel (R = 0.84). The consequences of this relation are discussed.

scholarly journals Liquid Biopsy and Other Non-Invasive Diagnostic Measures in PCNSL

Cancers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2665
Author(s):  
Alexander Baraniskin ◽  
Roland Schroers
Keyword(s):  
Central Nervous System Lymphoma ◽  
Circulating Tumor Dna ◽  
Mri Findings ◽  
Diagnostic Measures ◽  
Non Hodgkin Lymphoma ◽  
Specificity And Sensitivity ◽  
Demyelinating Lesions ◽  
Granulomatous Diseases ◽  
High Level ◽  
Almost All

Primary central nervous system lymphoma is a rare but highly aggressive form of non-Hodgkin lymphoma that remains confined to the CNS neuroaxis. The diagnosis of PCNSL requires a high level of suspicion as clinical presentation varies depending on the involved CNS areas. Neurological symptoms and MRI findings may mimic gliomas, demyelinating lesions, or infectious and granulomatous diseases. Almost all PCNSL patients undergo invasive surgical procedures for definite diagnosis. Stereotactic biopsy is still the gold standard in achieving a diagnostic accuracy of 73–97%. Both the potential procedural morbidity and mortality, as well as the time to definite histopathologic diagnosis resulting in delays of treatment initiation, have to be considered. On the contrary, minimally invasive procedures, such as MRI, CSF cytology, and flow cytometry, still have limited value due to inferior specificity and sensitivity. Hence, novel diagnostic approaches, including mutation analyses (MYD88) in circulating tumor DNA (ctDNA) and the determination of microRNAs (miR-21, miR-19b, and miR-92) as well as cytokine levels (IL10 and IL6) in blood, cerebrospinal fluid (CSF), and vitreous fluid (VRF), move into the focus of investigation to facilitate the diagnosis of PCNSL. In this review, we outline the most promising approaches that are currently under clinical consideration.

Far-ultraviolet spectroscopy of solid and liquid states: characteristics, instrumentation, and applications

The Analyst ◽  
2016 ◽  
Vol 141 (13) ◽  
pp. 3962-3981 ◽  
Author(s):  
Yukihiro Ozaki ◽  
Ichiro Tanabe
Keyword(s):  
Electronic Structures ◽  
Basic Science ◽  
Ultraviolet Spectroscopy ◽  
Far Ultraviolet ◽  
Liquid States ◽  
Almost All ◽  
Solid And Liquid States

Far-ultraviolet spectroscopy (≥200 nm) can greatly contribute to the basic science of electronic structures for almost all materials and their applications.

POVERTY REDUCTION, UNEMPLOYMENT AND RURAL DEVELOPMENT; AFTERMATH OF COVID-19 PANDEMIC IN NIGERIA

2021 ◽  
Vol 9 (1) ◽  
pp. 36-49
Author(s):  
Oderinu Hassana ◽  
◽  
Kadir Mumini ◽  
Tijani Adebayo ◽  
Keyword(s):  
Economic Development ◽  
Rural Development ◽  
Rural Areas ◽  
Poverty Reduction ◽  
Design Method ◽  
Gear Up ◽  
Global Pandemic ◽  
High Level ◽  
Almost All ◽  
Self Administered Questionnaire

Nigeria has one of the countries whose experience of poverty and unemployment is on the high side makes this study to look into the effect of the economic lockdown during the global pandemic in the country, with the aim of making effort on how this effect can be translated into economic development. Survey research design method was adopted with self-administered questionnaire used to collect data. Findings revealed that in Nigeria COVID -19 outbreak effects was felt in almost all sectors and the aftermath greatly affected the country’s GDP and this adversely affect rural development in the country, which translated to a worrisome rate of poverty and unemployment. Hence, both individual and government have now seen that campaigning for economic diversification is not sufficient for economic development but rather a prompt swing into action by all is needed for sustainable development of rural areas to respond to the worrisome rate of unemployment and in turn high level of poverty caused by the COVID-19 lockdown in the country. It was recommended that government at all level as well as individuals and stakeholders should put in place actions that would gear up rural development and set policies at their various helms of affairs that would encourage economic participation of all citizens in all sector of the economy.

FOOD SAFETY KNOWLEDGE, ATTITUDES AND PRACTICES AMONG FEDERAL UNIVERSITY OF AGRICULTURE STUDENTS IN ABEOKUTA

2017 ◽  
Vol 15 (1) ◽  
pp. 94-107
Author(s):  
M O ADEGUNWA ◽  
M I SANUSI ◽  
H A BAKARE ◽  
A M OMEMU
Keyword(s):  
Food Safety ◽  
Contributing Factors ◽  
Safety Attitudes ◽  
Attitudes And Practices ◽  
Handling Practices ◽  
High Level ◽  
Almost All ◽  
The University ◽  
Safety Knowledge ◽  
Safety Attitude

Improper practices, poor attitudes and lack of knowledge by food handlers are contributing factors for the spread of foodborne diseases. Food safety knowledge is an important factor in improving food safety practices and subsequently food safety attitude. This study is aimed at exploring the food safety knowledge, practice and attitude of FUNAAB students. A self completed questionnaire was answered by randomly selected 270 students from each of the nine (9) colleges in the university and analyzed using SPSS software. The study revealed that almost all of the students had a high level of food safety awareness but the knowledge was not to large extent translated into practice. Majority of the students also had good food safety attitudes as many of them are willing to change their food handling behav-iour when they know they are incorrect (94.8%). The study further revealed similar level of food safety knowledge between the male and female. Despite the level of students’ knowledge, their choice of eating place on campus was determined by the price of the food. This study therefore concluded that good knowledge of food safety does not determine students’ safe handling practices and choice of eating place.Keywords: Food safety

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