Defect structure of EFG silicon ribbon

The defect structure of EFG ribbons was studied using EBIC, TEM and HVEM. By imaging the same areas in EBIC and HVEM, a direct correlation between the crystallographic nature of defects and their electrical properties was obtained. (1) Partial dislocations at coherent twin boundaries may or may not be electrically active. Since no microprecipitates were observed at these dislocations it is likely that the different electrical activity is a consequence of the different dislocation core structures. (2) 2nd order twin joins were observed which followed the same direction as the coherent first order twins normally associated with EFG ribbons. These 2nd order twin joins are in all cases strongly electrically active. EFG ribbons contain high concentrations of carbon. Since no evidence of precipitation was found with TEM it is suggested that the carbon may be incorporated into the higher order twin boundaries now known to exist in EFG ribbons

Defect structure of web silicon ribbon

The results of a preliminary study of two dendritic web samples are presented. The structure and electrical activity of the defects in the silicon webs were studied. Optical microscopy of chemically etched specimens was used to determine dislocation densities. Samples were mechanically polished, then Secco etched for approximately 5 minutes. High voltage transmission electron microscopy was used to characterize the crystallographic nature of the defects

Comparative Laboratory Evaluation and Field Observations of a Modified Class I Base

A number of materials and methods have been used in the continuing search for a satisfactory initial bituminous treatment. Towards this end, three traffic bound roads were given initial treatment, in the summer of 1956, with three inches of Kentucky a Standard Class I Base mixture. The large size coarse aggregate -- either No. 36 or No. 48 stone -- in this mixture made the material difficult to work, however, and caused severe segregation during handling. Although a well integrated mixture of the type could have been compacted to about eight percent voids, the excessive segregation left many areas of the pavement very open. It was believed, therefore, that any initial treatment with this material would have to be sealed in order to prevent entry of water

Bridge Resurfacing with Silica Sand-Asphalt Mixture

The bituminous section has been engaged in testing silica sand-asphalt mixtures composed of various penetration grades of asphalt and sands from sand and sandstone deposits from several different areas of the state since early this year. The purpose of this study was to develop a surfacing mixture which would provide a skid-resistant surface and which could be machine laid in thin courses

Decoherence and single electron charging in an electronic Mach-Zehnder interferometer

We investigate the temperature and voltage dependence of the quantum interference in an electronic Mach-Zehnder interferometer using edge channels in the integer quantum-Hall-regime. The amplitude of the interference fringes is significantly smaller than expected from theory; nevertheless the functional dependence of the visibility on temperature and bias voltage agrees very well with theoretical predictions. Superimposed on the Aharonov-Bohm (AB) oscillations, a conductance oscillation with six times smaller period is observed. The latter depends only on gate voltage and not on the AB-phase, and may be related to single electron charging.Comment: 4 pages, 6 figures, discussion of charging effect change

Edge Channel Interference Controlled by Landau Level Filling

We study the visibility of Aharonov-Bohm interference in an electronic Mach-Zehnder interferometer (MZI) in the integer quantum Hall regime. The visibility is controlled by the filling factor $\nu$ and is observed only between $\nu \approx 2.0$ and 1.0, with an unexpected maximum near $\nu=1.5$. Three energy scales extracted from the temperature and voltage dependences of the visibility change in a very similar way with the filling factor, indicating that the different aspects of the interference depend sensitively on the local structure of the compressible and incompressible strips forming the quantum Hall edge channels.Comment: 5 pages, 5 figures, final version accepted for publication in Phys. Rev.

Direct observation of band-gap closure for a semiconducting carbon nanotube in a large parallel magnetic field

We have investigated the magnetoconductance of semiconducting carbon nanotubes (CNTs) in pulsed, parallel magnetic fields up to 60 T, and report the direct observation of the predicted band-gap closure and the reopening of the gap under variation of the applied magnetic field. We also highlight the important influence of mechanical strain on the magnetoconductance of the CNTs.Comment: 4 pages, 4 figure