Trap modulated photoresponse of InGaN/Si isotype heterojunction at zero-bias

n-n isotype heterojunction of InGaN and bare Si (111) was formed by plasma assisted molecular beam epitaxy without nitridation steps or buffer layers. High resolution X-ray diffraction studies were carried out to confirm the formation of epilayers on Si (111). X-ray rocking curves revealed the presence of large number of edge threading dislocations at the interface. Room temperature photoluminescence studies were carried out to confirm the bandgap and the presence of defects. Temperature dependent I-V measurements of Al/InGaN/Si (111)/Al taken in dark confirm the rectifying nature of the device. I-V characteristics under UV illumination, showed modest rectification and was operated at zero bias making it a self-powered device. A band diagram of the heterojunction is proposed to understand the transport mechanism for self-powered functioning of the device. (c) 2015 AIP Publishing LLC.

A modified auxiliary excitation signal for achieving unidirectional ion ejection in quadrupole ion trap mass spectrometers operating in the resonance ejection mode

This paper proposes a technique to cause unidirectional ion ejection in a quadrupole ion trap mass spectrometer operated in the resonance ejection mode. In this technique a modified auxiliary dipolar excitation signal is applied to the endcap electrodes. This modified signal is a linear combination of two signals. The first signal is the nominal dipolar excitation signal which is applied across the endcap electrodes and the second signal is the second harmonic of the first signal, the amplitude of the second harmonic being larger than that of the fundamental. We have investigated the effect of the following parameters on achieving unidirectional ion ejection: primary signal amplitude, ratio of amplitude of second harmonic to that of primary signal amplitude, different operating points, different scan rates, different mass to charge ratios and different damping constants. In all these simulations unidirectional ejection of destabilized ions has been successfully achieved. (C) 2015 Elsevier B.V. All rights reserved.

Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean

Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45 degrees E and 80 degrees E and 10 degrees N to 53 degrees S) were analysed and compared with the equilibrium delta O-18 and delta C-13 values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within similar to 0.25% for the region between 10 degrees N and 40 degrees S and 75-200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40 degrees S to 55 degrees S), however, the measured delta O-18 and delta C-13 values are higher than the expected values by similar to 2% and similar to 1% respectively. These enrichments can be attributed to either a `vital effect' or a higher calcification rate. An interesting pattern of increase in the delta C-13(DIC) value of the surface water with latitude is observed between 35 degrees S and similar to 60 degrees S, with a peak at similar to 42 degrees S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the delta C-13(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude.