Large Area Flexible Amorphous Silicon Position Sensitive Detectors

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Large Area Flexible Amorphous Silicon Position Sensitive Detectors Elvira M.C. Fortunato, Donatello Brida, Isabel M.M. Ferreira, H. M.B. Águas, Patrícia Nunes, Ana Cabrita, Franco Giuliani, Yuri Nunes1, Manuel J.P. Maneira1, Rodrigo F.P. Martins Materials Science Department / CENIMAT, Faculty of Sciences and Technology of New University of Lisbon and CEMOP-UNINOVA, Quinta da Torre, 2825-114 Caparica, Portugal. 1 Physics Department / CEFITEC, Faculty of Sciences and Technology of New University of Lisbon and CEMOP-UNINOVA, Quinta da Torre, 2825-114 Caparica, Portugal. ABSTRACT Large area thin film position sensitive detectors based on amorphous silicon technology have been prepared on polyimide substrates using the conventional plasma enhanced chemical vapour deposition technique. The sensors have been characterised by spectral response, illuminated I-V characteristics and position detectability measurements. The obtained one dimensional position sensors with 5 mm wide and 60 mm long present a maximum spectral response at 600 nm, an open circuit voltage of 0.6 V and a position detectability with a correlation of 0.9989 associated to a standard deviation of 1×10-2, comparable to those ones produced on glass substrates. The surface of the sensors at each stage of fabrication was investigated by Atomic Force Microscopy. INTRODUCTION Since the introduction of concept of large area thin film position sensitive detectors by the present authors some years ago [1, 2, 3], most of the work done has been concentrated in the development of the device performances deposited in rigid substrates, such as glass. However, in applications where the control has to be made upon a rotating axis of a motor or if it is required the determination of the angular position of the rotor of a motor, is of great importance to have a curved sensor with a cylindrical shape. To do so, the sensing element should be deposited on a flexible substrate. In this paper we present by the first time the electro-optical performances of 1D large area (5 mm × 60 mm) a-Si:H thin film position detectors deposited on polymeric substrates (polyimide foil), compatible with all the steps related with the deposition of the materials as well as the photolithography techniques used. As far as the present knowledge of the authors, no position sensors have been deposited on polymeric flexible substrates. The only devices deposited on flexible substrates using the a-Si:H technology are solar cells [4, 5] and thin film transistors (TFTs) [6, 7]. Apart from that, for large area sensors the main works worldwide referred [8] are those of references [9-14]. Apart from that, we also demonstrate that when improved interfaces (i-n) are produced the top metal contact does not need to cover the entire active area of the sensor to produce the required lateral photovoltage. The obtained results clearly demonstrate the suitability of these devices for use in a new type of lightweight, highly durable, unbreakable and flexible position sensitive detectors.

A12.7.1

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