Despite the fact that current-use pesticides (CUP) have different chemical properties to first-generation organochlorine products, the long-term and long-range environmental behavior of these chemicals is still unclear. Data for 45 active ingredients of CUPs were collected, most of which originate from the results of simulation tests submitted for authorization. According to the Stockholm Convention on persistent organic pollutants (POPs), two of the 45 CUPs exceed both screening level criteria for persistence and long-range transport potential (LRTP). Thirteen CUPs meet the persistence criterion and just one for LRTP. This classification is compared to the reference chemicals approach using overall persistence (P(ov)) and characteristic travel distance (CTD) calculated with a multimedia model. Although none of the 45 CUP have a CTD above the LRTP boundary line, three of them exceed the overall persistence criterion derived from legacy POPs for classification. Nineteen CUPs are transported over longer distances in water than in air. For such polar substances a LRTP boundary has yet to be defined. We recommend the multimedia model modeling approach to calculate P(ov) and LRTP as a second tier in persistence and LRTP assessment.

The piezoresistive response of n-and p-type hydrogenated nanocrystalline silicon thin films, deposited by hot-wire (HW) and plasma-enhanced chemical vapor deposition (PECVD) on thermally oxidized silicon wafers, has been studied using four-point bending tests. The piezoresistive gauge factor (GF) was measured on patterned thin-film micro-resistors rotated by an angle θ with respect to the principal strain axis. Both longitudinal (GF L) and transverse (GF T) GFs, corresponding to θ = 0º and 90º, respectively, are negative for n-type and positive for p-type films. For other values of θ (30º, 45º, 120º and 135º) GFs have the same signal as GF L and GF T and their value is proportional to the normal strain associated with planes rotated by θ relative to the principal strain axis. It is concluded that the films are isotropic in the growth plane since the GF-values follow a Mohr's circle with the principal axes 2 coinciding with those of the strain tensor. The strongest p-type pirezoresistive response (GF L = 41.0, GF T = 2.84) was found in a film deposited by PECVD at a substrate temperature of 250ºC and working pressure of 0.250 Torr, with dark conductivity 1.6 Ω-1 cm-1. The strongest n-type response (GF L =-28.1, GF T =-5.60) was found in a film deposited by PECVD at 150ºC and working pressure of 3 Torr, with dark conductivity 9.7 Ω-1 cm-1. A model for the piezoresistivity of nc-Si is proposed, based on a mean-field approximation for the conductivity of an ensemble of randomly oriented crystallites and neglecting grain boundary effects. The model is able to reproduce the measured GF L values for both n-and p-type films. It fails however to explain the transversal GF T data. Both experimental and theoretical data show that nanocrystalline silicon can have an isotropic piezoresistive effect of the order of 40% of the maximum response of crystalline silicon.

This study aims at a better understanding of the electronic surface passivation of monocrystalline silicon wafers by thin amorphous silicon carbide (a‐SiC:H) layers. Annealing a‐SiC:H coated Si wafers in forming gas up to an annealing temperature Tan = 700 oC, reveals the correlation between the effective charge carrier lifetime τeff and structural features of the a‐SiC:H monitored by Fourier‐Transform Infra Red (FTIR) spectroscopy. Passivation layers with low carbon content yield effective lifetimes τeff > 1 ms for Tan = 600 °C. Increasing the C content lowers the thermal stability of the electronic passivation. Out of detailed FTIR measurements, the absorption strength ratio R permits statements of microvoids in the amorphous layers. Comparing R with the effective lifetimes enables a qualitative forecast concerning the temperature stability of a‐SiC:H passivation layers. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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