Thin film position sensitive detectors based on pin amorphous silicon carbide structures A. Cabrita * , J. Figueiredo, L. Pereira, H. A ´ guas, V. Silva, D. Brida, I. Ferreira, E. Fortunato, R. Martins Faculty of Sciences and Technology, Department of Materials Science, New University of Lisbon and CEMOP-UNINOVA, Quinta da Torre, P 2829-516 Caparica, Portugal Abstract The aim of this paper is to present data concerning the performances of position sensitive detectors based on silicon carbide alloys, able to detect the green colour and to compare their performances with the ones exhibit by position sensitive detectors, optimised to detect the red colour. The data achieved show that the device linearity is quite high with spatial resolution errors below 1%. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Position sensitive detectors; Silicon carbide alloys; Pin structure 1. Introduction Optical inspection systems to determine the posi- tion or the excursion of controlled arms are of great importance in a wide range of mecatronics applica- tions. Position sensitive detectors (PSD) are widely used in this application since they allow a continuous and unmanned detection process [1,2]. PSD using hydrogenated amorphous silicon as the active layer has been proposed either with the usual pin structure or alternatively using Schottky barrier diodes [3–5], aiming to avoid the use of complex optics, mainly in processes where the response time is pre-determined by the mechanical parts [6,7] or when PSD in flexible substrates are required [8]. In this case, the devices are matched to respond to light wavelengths in the range of 620–650 nm. Nevertheless, PSD able to respond to other wavelengths can also be produced by proper control of the optical gap of the semiconductor. So, to produce PSD able to detect the green or the blue colour, silicon carbide alloys should be used as the active layer. In this work, we investigate the effect of using silicon carbide active layers, with the target to obtain colour detectable position sensors, working in the range between the green and blue region of the light spectrum. With this objective we present by the first time the electro-optical performances achieved in a-Si x : C 1x :H=pin structure used as one-dimensional colour sensitive PSD, using a high quality low defect intrinsic layers deposited by a non-conventional mod- ified triode PECVD system [9], comparing them with the performances presented by conventional PSD based on a-Si:H pin structures. This new configuration allows the deposition of high quality a-Si x :C 1x :H layer, where the final device performances are mainly a function of the gas mixture composition and the thickness of the i-layer, used. Applied Surface Science 184 (2001) 443–447 * Corresponding author. Tel.: þ351-212948525; fax: þ351-212941365. E-mail address: amfc@uninova.pt (A. Cabrita). 0169-4332/01/$ – see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0169-4332(01)00532-3