| 1. |
- Ashwin, M.J., et al.
(författare)
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The bonding of CAs acceptors in InxGa1-xAs grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon
- 1996
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 80:12, s. 6754-6760
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Tidskriftsartikel (refereegranskat)abstract
- InxGa1-xAs layers (0≤x≤0.37) doped with carbon (>1020 cm-3) were grown on semi-insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAs for values x up to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest-neighbor bonding configurations of CAs were investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A-1 symmetry) and the symmetric XH mode (A+1 symmetry) of the H-CAs pairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm-1 had been assigned to passivated Ga4CAs clusters. New modes at 2550 and 430 cm-1 increased in strength with increasing values of x and are assigned to passivated InGa3CAs clusters. These results were compared with ab initio local density functional theory. Modes due to AlInGaCAs clusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4 is an efficient C doping source since both In-CAs bonds as well as Ga-CAs bonds are formed, whereas there is no evidence for the formation of In-CAs bonds in samples doped with C derived from trimethylgallium or solid sources
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| 2. |
- Hourahine, B, et al.
(författare)
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Hydrogen molecules in silicon located at interstitial sites and trapped in voids
- 1998
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 57:20, s. 12666-12669
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Tidskriftsartikel (refereegranskat)abstract
- The vibrational modes of H2 molecules in Si are found using a first-principles method and compared with recent experimental investigations. The isolated molecule is found to lie at a Td interstitial site, oriented along [011] and is infrared active. The rotational barrier is at least 0.17 eV. The molecular frequency is a sensitive function of cage size and increases to lie close to the gas value for cages about 50% larger than the Td site. It is suggested that Raman-active modes around 4158 cm-1 are due to molecules within voids.
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| 3. |
- Newman, Jeffrey D., et al.
(författare)
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Catalytic materials, membranes and fabrication technologies suitable for the construction of amperometric biosensors
- 1995
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 67:24, s. 4594-4599
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A selection of recently available catalytic carbon powders were assessed and compared with the more conventionally used platinized material. Their suitability for incorporation in amperometric biosensors is discussed, In conjunction with this study, methods of applying membranes to the surfaces of these devices were investigated. Advanced fabrication technologies, potentially suitable for scale-up of sensor production, such as screen printing and ink-jet printing, were used for manufacture of the complete sensor structure. Hydrogen peroxide-sensing electrodes and glucose biosensors were produced as model systems, demonstrating the advantages of these approaches. The commercially available rhodinized carbon MCA4 produced a high current density at low potentials over a plateau region (300-400 mV vs SCE). In addition, direct oxidation of glucose (seen with platinized carbon) was not observed at the chosen potential of +350 mV. Further interference studies using fermentation media highlighted its suitability as an electrode material for use in complex samples. Ink-jet printing proved to be a successful method for the deposition of Nafion membranes of defined and reproducible geometry.
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