Fabrication and characterization of monolithically integrated microchannel plates based on amorphous silicon
Citation
Franco, A., Geissbühler, J., Wyrsch, N. & Ballif, C. Fabrication and characterization of monolithically integrated microchannel plates based on amorphous silicon. Sci. Rep. 4, 4597; DOI:10.1038/srep04597 (2014).
- Microchannel plates (MCPs)
- Hydrogenated amorphous silicon (a-Si:H)
- Monolithic integration
- Electron multiplication
- Fabrication process
- Characterization
- Applications
Brief
This article presents the fabrication and characterization of the first microchannel plate made of hydrogenated amorphous silicon, a breakthrough enabling monolithic integration on various substrates.
Summary
This article presents a novel design for microchannel plates (MCPs) constructed from hydrogenated amorphous silicon (a-Si:H), termed AMCPs. AMCPs offer several advantages over conventional lead-glass MCPs, including:
- Vertical Integration: AMCPs can be directly integrated onto application-specific integrated circuits (ASICs) or solid-state detectors due to the low-temperature deposition process of a-Si:H. This monolithic integration minimizes dead area, allows for independent optimization of components, and reduces reliance on expensive bonding techniques.
- Material Properties of a-Si:H: The inherent resistivity of a-Si:H enables charge replenishment for secondary electrons without requiring an additional semiconducting layer, unlike lead-glass MCPs.
- Customizable Channel Geometry: Micromachining techniques from the microelectronics industry allow for customization of channel geometry in AMCPs.
The sources describe the fabrication process of AMCPs, which involves depositing thin layers of a-Si:H and other materials onto a silicon substrate, followed by a meticulous photolithography and deep reactive ion etching (DRIE) process to create the microchannels. They successfully demonstrated an electron multiplication factor exceeding 30 in AMCPs with an aspect ratio of 12.5:1. This gain was achieved at input photoelectron currents up to 100 pA, showing the a-Si:H's efficiency in replenishing electrons during the multiplication process.
While the achieved gain is less than conventional MCPs, it is expected to increase by orders of magnitude with further optimization of aspect ratio and by using high secondary-emission materials. The sources conclude by outlining future research directions for AMCPs, including integration with Medipix2 ASICs for particle tracking and photon-counting applications, and hybrid detectors with G-APDs for medical imaging.