The influence of different transparent conducting oxides (TCO) on the transverse photoelectrical properties of one-dimensional position sensitive detectors based on p-i-n amorphous silicon structures was studied. For both SnO 2 and indium tin oxide, poor quality of the p layer was revealed by secondary ion mass spectroscopy measurements. Good agreement between experimental and simulation characteristics of TCO/p-i-n structure was additionally conditioned by a strong increase in defect states at the p layer surface which can be attributed to the reduction/ oxidation process at the TCO/p interface. However, the analysis showed that under reverse bias the spectral response of the p-i-n structure is not significantly affected by different TCO layers and conditions at the TCO/p heterojunction. Nevertheless, indium tin oxide is less appropriate for a front TCO layer due to the poor reverse dark current-voltage characteristic, i.e., higher leakage current component leading to lower signal to noise ratio. © 1997 American Institute of Physics.

We consider singular integral operators with piecewise continuous coefficients on reflexive Orlicz spaces \(L_M(\Gamma)\), which are generalizations of the Lebesgue spaces \(L_p(\Gamma)\), \(1 < p < \infty\). We suppose that \(\Gamma\) belongs to a large class of Carleson curves, including curves with corners and cusps as well as curves that look locally like two logarithmic spirals scrolling up at the same point. For the singular integral operator associated with the Riemann boundary value problem with a piecewise continuous coefficient \(G\), we establish a Fredholm criterion and an index formula in terms of the essential range of \(G\) complemented by spiralic horns depending on the Boyd indices of \(L_M(\Gamma)\) and contour properties. Our main result is a symbol calculus for the closed algebra of singular integral operators with piecewise continuous matrix-valued coefficients on \(L_M^n(\Gamma)\).

From the flying spot technique (FST) the ambipolar diffusion length and the effective-lifetime of the carriers photogenerated by a moving light spot that strikes a p-i-n junction can be inferred. In this paper, those properties of a p-i-n junction are used together with an optical triangulation principle to determine the velocity of an object that is moving in the direction of a light source. The light reflected back from the object is analysed through an amorphous or a microcrystalline p-i-n structure. Its transient transverse photovoltage is dependent on the velocity of the object. A comparison between the performances of both kinds of devices is presented.

This paper is based on a study about the Setúbal region, included in the internacional project “The Future of Industry in Europe” for the programme FAST-MONITOR of the European Community (1992-94). There were some information on the project VW/Ford for this region and those that are connected with research networks on industrial sectors (specially, on the automobile industry), and the network on the spatial and regional factors of regional development. Those studies allowed the scenario development on evolution trends of European industry and, specifically, on the automobile sector, and on the Setúbal region that was studied by the Portuguese team.

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We have developed in the past a transient technique called Flying Spot Technique (FST)[1], based on the lateral photoeffect. It allows to determine the ambipolar diffusion length and the effective lifetime of the photogenerated carriers, once the light spot velocity and geometry of the structure are known. We propose to apply this technique backwards in order to detect the path and velocity of an object that is moving toward a light source direction. The light back reflected is analyzed by a p.i.n structure measuring the transient transverse photovoltage which is dependent on the object movement (position and velocity). Details concerning material characterization and device geometry will be presented.

In this work we report experimental results on light induced metastability of a-Si: H p.i.n. devices with different microscopic/macroscopic structures and we discuss them in terms of improved stability through spatial control of charged defects grown during light exposure. By placing a thin (few A) intrinsic layer (i) between both p/i and i/n a-Si: H interfaces we are able to reduce the effective degradation rate through spatial modification of the electric field profile in the device. The electronic transport and the stability changes that accompany the change in microstructure (R) and hydrogen content (CH) of the i- and i′-layer, were monitored throughout the entire light induced degradation process and compared with the corresponding μT product (for both carriers) inferred through steady state photoconductivity and Flying Spot Technique (FST) measurements. Results show that the degradation rate is a function of CH and R of both layers and can be correlated with the density of microvoids and di-hydride bonding. Since the i′-layers have a higher CH bonded mainly as SiF2 radicals (R≈0.4), they act as an hindrance to the growth of the defect, in the active region, generating "gettering centers" whose localisation and density are tailored in such a way that they will control spatially the electric field profile during light exposure. Preliminary results show improvements in film's stability when the interfacial layer is included. So future progress toward more stable and efficient a-Si: H solar cells will depend on a careful engineering design of the devices. © 1994 Materials Research Society.

In this paper we present results of PIN single and dual axis Thin Film Position Sensitive Detectors (TFPSD) based on hydrogenated amorphous silicon (a-Si:H) technology, with a wide detection area (up to 80 × 80 mm). These sensors provide an alternative to Charge Coupled Devices (CCDs) when large inspection areas are needed, under a requirement to use simpler technology. In this paper we analyse the forward and reverse I-V characteristics in the dark and under illumination, as well as the device linearity of TFPSD. © 1994.

On this paper we report the physical model that supports the theory of the Flying Spot Technique (FST). Through this technique it is possible to determine separately the ambipolar diffusion length (L*) and the effective lifetime (τ*) of the generated carriers, using either Schottky diodes or quasi-ohmic sandwich structures. We also report a new static method based on the Spectral Photovoltage (SPT) that allows to infer the ambipolar diffusion length and to estimate the surface recombination velocity. © 1991 Elsevier Science Publishers B.V. All rights reserved.