Controlled Doping Methods for Radial p/n Junctions in Silicon

P/n and n/p junctions with depths of 200 nm to several micrometers have been created in flat silicon substrates as well as on 3D microstructures by means of a variety of methods, including solid source dotation (SSD), low-pressure chemical vapor deposition (LPCVD), atmospheric pressure chemical vapor deposition, and plasma-enhanced chemical vapor deposition. Radial junctions in Si micropillars are inspected by optical and scanning electron micro­scopies, using a CrO3-based staining solution, which enables visualization of the junction depth. When applying identical-doping parameters to flat substrates, ball grooving, followed by staining and optical microscopy, yields similar junction depth values as high-resolution scanning electron microscopy imaging on stained cross-sections and secondary ion mass spectrometry depth profilometry. For the investigated 3D microstructures, doping based on SSD and LPCVD give uniform and conformal junctions. Junctions made with SSD-boron doping and CVD-phosphorus doping could be accurately predicted with a model based on Fick's diffusion law. 3D-microstructured silicon pillar arrays show an increased efficiency for sunlight capturing. The functionality of micropillar arrays with radial junctions is evidenced by improved short-circuit current densities and photovoltaic efficiencies compared with flat surfaces, for both n- and p-type wafers (average pillar arrays efficiencies of 9.4% and 11%, respectively, compared with 8.3% and 6.4% for the flat samples)

A high‐throughput Raman notch filter set

A chevron‐type Raman notch filter (RNF) set is described. lt combines a high signal throughput (up to 90% around 1600 cm−1 and ≳80% between and 700 and 2700 cm−1) with a laser line suppression of 108–109. The filter set can be used to replace the first two dispersion stages in triple‐stage Raman monochromators commonly employed in multichannel detection systems. This yields a gain in intensity of the detected Raman signal of a factor of 4. It is shown that in Raman spectrometers with a backscatter geometry, the filter set can also be used to optically couple the microscope and the spectrometer. This leads to a further increase in signal intensity of a factor of 3–4 as compared to the situation where a beam splitter is used. Additional advantages of the RNF set are the fact that signal throughput is almost polarization independent over a large spectral interval and that it offers the possibility to simultaneously record Stokes and anti‐Stokes spectra

Diffusion model for iontophoresis measured by laser-Doppler perfusion flowmetry, applied to normal and preeclamptic pregnancies

We present a physical model to describe iontophoresis time recordings. The model is a combination of monodimensional material diffusion and decay, probably due to transport by blood flow. It has four adjustable parameters, the diffusion coefficient, the decay constant, the height of the response, and the shot saturation constant, a parameter representing the relative importance of subsequent shots (in case of saturation). We test the model with measurements of blood perfusion in the capillary bed of the fingers of women who recently had preeclampsia and in women with a history of normal pregnancy. From the fits to the measurements, we conclude that the model provides a useful physical description of the iontophoresis process. (c) 2007 Society of Photo-Optical Instrumentation Engineers.</p

Control methods for Dermanyssus gallinae in systems for laying hens: results of an international seminar

This paper reports the results of a seminar on poultry red mite (PRM), Dermanyssus gallinae. Eighteen researchers from eight European countries discussed life cycle issues of the mite, effects of mites on hens and egg production, and monitoring and control methods for PRM in poultry facilities. It was determined that PRM probably causes more damage than envisaged, with the cost in The Netherlands alone reaching 11 million euro per annum. However a great deal is still unknown about PRM (e.g. reproduction, survival methods, etc.) and that PRM monitoring is an important instrument in recognising and admitting the problem and in taking timely measures. Currently, the most promising control method combines heating the hen house in combination with chemical treatments. Future areas of development which show promise include the use of entomopathogenic fungi, vaccination and predatory mites. The final aim is to solve the problem of D. gallinae in housing systems for laying hens

Ultrafast Photoinduced Heat Generation by Plasmonic HfN Nanoparticles

There is great interest in the development of alternatives to noble metals for plasmonic nanostructures. Transition metal nitrides are promising due to their robust refractory properties. However, the photophysics of these nanostructures, particularly the hot carrier dynamics and photothermal response on ultrafast timescales, are not well understood. This limits their implementation in applications such as photothermal catalysis or solar thermophotovoltaics. In this study, the light-induced relaxation processes in water-dispersed HfN nanoparticles are, for the first time, elucidated by fs transient absorption, Lumerical FDTD and COMSOL Multiphysics simulations, and temperature-dependent ellipsometry. It is unequivocally demonstrated that HfN nanoparticles convert absorbed photons into heat within <100 fs; no signature of hot charge carriers is observed. Interestingly, under high photon energy or intense irradiation stimulated Raman scattering characteristic of oxynitride surface termination is observed. These findings suggest that transition metal nitrides could offer benefits over noble metals in the field of plasmonic photothermal catalysis