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A9.03 - High Gain Amorphous Silicon-Based Microchannel Plate Detector 
April 24, 2014   4:00pm - 4:15pm

Microchannel plates (MCP) are attractive for amplification purposes for very fast detectors and are commonly used for image intensifying device [1]. Amplification of the signal is obtained by the multiplication of electrons in the microchannels upon avalanche mechanisms. In order to overcome some critical limitations of current MCP technology, we recently proposed to use hydrogenated amorphous silicon (a-Si:H) instead of lead silicate glass [2]. The use of a-Si:H associated with a new device structure should allow for better performance, simplify the construction of the device and permit a possible vertical integration of the MCP on top of the readout electronics. These advantages should broaden the range of application including particle detection and imaging.First a-Si:H based MCP prototypes were fabricated with a simple two-terminal designed [3]. Avalanches mechanisms could be demonstrated by electron beam induced current imaging, but analysis of the gain appeared very problematic. The main drawback of the simple 2-terminal device structure is the fact that separation of the signal (resulting from the avalanche process) from the leakage is almost impossible.To overcome these limitations, MCPs with a 3-terminal monolithic configuration were designed and successfully fabricated on oxidized Si wafer. These new devices comprise channels with a diameter of 3-5 µm drilled by deep reactive ion etching (DRIE) into 80-100 µm thick a-Si:H based layer stacks. The latter requires a careful control and optimization of the deposition to minimize the stress build up and integrity of MCP. Gain characterization was performed in continuous mode operation and gain values in excess of 30 could be recorded for an aspect ratio of only 12.5.In this paper, we will describe and discuss the processes and issues related to the fabrication of such 3 terminal a-Si:H based MCPs. Gain analysis in relation with device geometry will be presented. Present performances, limitations and possible improvements will be discussed.[1] J. L. Wiza, Nucl. Instr. and Meth. 162, 1979, 587-601.[2] A. Franco et al., Nucl. Instr. and Meth. in Phys. Res. A 695 (2012) 74.[3] N. Wyrsch et al., MRS Proc. Vol. Vol. 1245, (2010) 193.

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