3,807 research outputs found
The influence of atmosphere on the performance of pure-phase WZ and ZB InAs nanowire transistors
We compare the characteristics of phase-pure MOCVD grown ZB and WZ InAs
nanowire transistors in several atmospheres: air, dry pure N and O, and
N bubbled through liquid HO and alcohols to identify whether
phase-related structural/surface differences affect their response. Both WZ and
ZB give poor gate characteristics in dry state. Adsorption of polar species
reduces off-current by 2-3 orders of magnitude, increases on-off ratio and
significantly reduces sub-threshold slope. The key difference is the greater
sensitivity of WZ to low adsorbate level. We attribute this to facet structure
and its influence on the separation between conduction electrons and surface
adsorption sites. We highlight the important role adsorbed species play in
nanowire device characterisation. WZ is commonly thought superior to ZB in InAs
nanowire transistors. We show this is an artefact of the moderate humidity
found in ambient laboratory conditions: WZ and ZB perform equally poorly in the
dry gas limit yet equally well in the wet gas limit. We also highlight the
vital role density-lowering disorder has in improving gate characteristics, be
it stacking faults in mixed-phase WZ or surface adsorbates in pure-phase
nanowires.Comment: Accepted for publication in Nanotechnolog
An Invariant Dual-beam Snowflake Antenna for Future 5G Communications
A broadband snowflake antenna for future 5G and millimeter-wave communications is presented. The proposed antenna has a size of 8 × 5 mm 2 . The antenna consists of a central hexagon surrounded by a series of symmetrically placed smaller hexagons around it, resulting in broadband characteristics. The impedance bandwidth of the proposed antenna ranges from 25.284-29.252 GHz. The antenna has a gain of 3.12 dBi at 28 GHz and is more than 98% efficient. A distinct feature of the proposed antenna is its dual-beam radiation pattern. The two beams remain fixed at ±50° even if the frequency is varied with in its operating band. The proposed antenna is modelled on thin Rogers substrate which makes it very useful for future 5G smart phones
Gender representation in Pakistani print media- a critical analysis
The key objective of this study was to examine the representations of men and women in print media in Pakistan. Gender role stereotyping and sexism in print media is not a low-profile gender issue as printed communication and contents still hold an important place in contemporary digital world. Keeping in view the importance of newspapers as the leading source of credible content/messages, this paper examined gender stereotyping and sexism in print media in Pakistan and attempted to highlight whether print media reproduces or challenges gender stereotypes and sexism? Keeping in view the complexity of sexism in print media, content and discourse analyses were performed on four widely read national newspapers. The findings have been placed within the socio-cultural context of Pakistani society and feminists theories. The study’s findings indicated that print media in Pakistan reinforces gender stereotypes and provide little challenge to gender stereotyped imagery of males and females
Integration over matrix spaces with unique invariant measures
We present a method to calculate integrals over monomials of matrix elements
with invariant measures in terms of Wick contractions. The method gives exact
results for monomials of low order. For higher--order monomials, it leads to an
error of order 1/N^alpha where N is the dimension of the matrix and where alpha
is independent of the degree of the monomial. We give a lower bound on the
integer alpha and show how alpha can be increased systematically. The method is
particularly suited for symbolic computer calculation. Explicit results are
given for O(N), U(N) and for the circular orthogonal ensemble.Comment: 12 pages in revtex, no figure
Structural and electronic properties of oxygen defective and Se-doped p-type BiVO4(001) thin film for the applications of photocatalysis
This is the final version. Available on open access from Elsevier via the DOI in this record.There is another record in ORE for this publication: http://hdl.handle.net/10871/36011Monoclinic BiVO4 is being used as a photocatalyst due to its stability, cost-effectiveness, ease of synthesis, and narrow band gap. Although, the valence band maximum, VBM (∼−6.80 eV vs vacuum) of BiVO4 is well below the redox potential of water but having less positive conduction band minimum, CBM (−4.56 eV vs vacuum), responsible for its low efficiency. We have carried out a comprehensive periodic density functional theory (DFT) simulations for the pristine, Oxygen defective (Ov) and Se doped BiVO4, to engineer not only its CB edge position but the overall photocatalytic and charge carrier properties. Our theoretical method has nicely reproduced the experimental data of pristine BiVO4, which encouraged us to elaborate further its Ov and Se-doped characteristics. It is found that both the Ov (1% Oxygen vacancy) and Se-doped BiVO4 (1–2% Se) have ideal band edges, band gaps, and small effective masses of electrons and holes, responsible for high photocatalytic activities. Moreover, Se-doped BiVO4 behave as p-type semiconductor. Finally, the photocatalytic water-splitting behaviour of the selected surfaces were counterchecked with water interaction, where the strong water adsorption energy of about ∼−38 to −50 kcal/mol, confirms and predicts their higher efficiencies compared to that of parent BiVO4.The financial support was provided by Engineering and Physical Science Research Council, UK (EPSRC) under the research grant No EP/P510956/1
Structural and electronic properties of oxygen defective and Se-doped p-type BiVO4(001) thin film for the applications of photocatalysis
This is the final version. Available on open access from Elsevier via the DOI in this record.There is another record in ORE fro this publication: http://hdl.handle.net/10871/30528Monoclinic BiVO4 is being used as a photocatalyst due to its stability, cost-effectiveness, ease of synthesis, and narrow band gap. Although, the valence band maximum, VBM (∼−6.80 eV vs vacuum) of BiVO4 is well below the redox potential of water but having less positive conduction band minimum, CBM (−4.56 eV vs vacuum), responsible for its low efficiency. We have carried out a comprehensive periodic density functional theory (DFT) simulations for the pristine, Oxygen defective (Ov) and Se doped BiVO4, to engineer not only its CB edge position but the overall photocatalytic and charge carrier properties. Our theoretical method has nicely reproduced the experimental data of pristine BiVO4, which encouraged us to elaborate further its Ov and Se-doped characteristics. It is found that both the Ov (1% Oxygen vacancy) and Se-doped BiVO4 (1–2% Se) have ideal band edges, band gaps, and small effective masses of electrons and holes, responsible for high photocatalytic activities. Moreover, Se-doped BiVO4 behave as p-type semiconductor. Finally, the photocatalytic water-splitting behaviour of the selected surfaces were counterchecked with water interaction, where the strong water adsorption energy of about ∼−38 to −50 kcal/mol, confirms and predicts their higher efficiencies compared to that of parent BiVO4.Engineering and Physical Sciences Research Council (EPSRC
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