Fluorescence lifetimes and emission patterns probe the 3D orientation of the emitting chromophore in a multichromophoric system

In this Communication, we report on the fluorescence behavior of an individual first generation multichromophoric dendrimer. The fact that each of the chromophores in time acts as a fluorescent trap is demonstrated by directly probing the dipole orientation of the emitting chromophore by means of defocused wide-field imaging and comparing experimental and calculated emission patterns. It is shown that in such cases the electromagnetic boundary condition effect results in discrete changes in the fluorescence lifetime as a function of time for individual dendrimers.     

The oxidation of 6- and 7-aryl-4(3h)-pteridinones by immobilized arthrobacter M-4 cells containing xanthine oxidase

The preparation of 6- and 7-(pX-phenyl)-4(3H)-pteridinones (X = H, CH₃, OCH₃) is described. The oxidation of these compounds by (immobilized) Arthrobacter M-4 cells containing xanthine oxidase has been studied. The oxidation monitored by uv spectroscopy usually goes fast, except for 7-(pX-phenyl)-4(3H)-pteridinones (X = CH₃, OCH₃), which are slowly oxidized. With bacterial cells immobilized in gelatine crosslinked with glutaraldehyde small laboratory-scale oxidations were carried out. Based on spectral data the products of the oxidation reactions are 6- and 7-aryllumazines.     

The variation of trace element concentrations in single human head hairs

The concentrations of nine trace elements in segments of individual human head hairs have been determined by neutron activation analysis. Concentration variations have been studied along individual hairs, among hairs plucked from various locations on the scalp, among hairs in different phases of the growth cycle, and before and after hair cleaning. Recent atomic absorption analysis data indicate strong concentration fluctuations in successive single hair segments of 2 to 5 mm in length. The results are discussed in a forensic context. Work supported by the National Research Council of Canada under Grant No. A2510, by the Canada Council through a bursary to D. Maes, by a grant from the President's Research Grant Fund of Simon Fraser University, and under a contract with the Department of the Solicitor-General of Canada through the Royal Canadian Mounted Police.     

Hole trapping during low gate bias, high drain bias hot-carrierinjection in n-MOSFETs at 77 K

Injection and trapping of holes in the gate oxide of n-channel MOS transistors during operation at large drain and small gate biases are investigated at liquid-nitrogen temperature. Experimental evidence is given that about three times less trapping of holes occurs in the gate oxide at 77 K as compared to 295 K. The authors show that this is due to the small hole mobility in SiO₂ at low temperature     

Investigation of the soft-write mechanism in source-side injectionflash EEPROM devices

The soft-write effect which occurs when reading the content of a source-side injection (SSI) flash EEPROM cell has been identified and thoroughly investigated. This effect is caused by an electron injection mechanism which has the same physical origin as the enhanced (or source-side) hot-electron injection that is used for fast flash EEPROM programming. A procedure for the prediction of the associated soft-write lifetime is proposed, subsequently applied to a state-of-the-art split-gate SSI cell, and found to be noncritical for a reliable device operation. Therefore, source and drain do not have to be interchanged during the read-out operation with respect to the programming operation, and the traditional forward read-out scheme can be maintained for SSI flash memories     

Modification and application of an emission microscope for continuous wavelength spectroscopy

A simple, cost effective, and highly sensitive spectroscopic technique for photon emission microscopy is proposed (SPEMMI). In contrast to earlier reported systems, this new system uses only one detector for both conventional failure localisation and spectral analysis. To demonstrate the functionality of the SPEMMI, emission spectra from forward and reversed biased diodes, and from a poly-Si resistor are presented. In addition, it is shown that the instrument allows fast determination, with μm resolution, of the temperature profile of devices.     

Observation of single interface traps in submicron MOSFET's bycharge pumping

The observation of single interface traps in small area MOSFET's by charge pumping is demonstrated for the first time, The dependence of the single trap charge pumping current on the base level voltage is described, Also the creation of one single interface trap under influence of low level hot carrier injection is demonstrated. A prediction of the charge pumping current behavior as a function of rise and fall time and temperature for the case of individual traps is made. The correlation with RTS-noise experiments is discussed