VUVSiPM · Developing next-generation silicon photomultipliers with enhanced VUV sensitivity

The objective of this proposed project is to produce silicon photomultipliers (SiPMs) with improved photon detection efficiency (PDE) at vacuum-ultraviolet (VUV) wavelengths. Detectors incorporating liquid Argon (LAr) and Xenon (LXe) are a key part of the global strategy for dark matter and neutrino physics, and high-efficiency detection of VUV scintillation light from these media is a major driver of detector sensitivity. Recent R&D work has produced SiPMs which can detect these wavelengths directly, but PDE is insufficient for deployment in an LAr detector and remains a limiting factor for physics reach in LXe experiments.Working closely with the CERN DRD2 (Liquid detectors) and DRD4 (Photon detectors) collaborations, the fellow will research two avenues for improved VUV PDE:I) Graphene anti-reflection coatings (ARCs): Graphene has up to 96% transmission for VUV light, and preliminary measurements indicate that a graphene/silicon interface may offer up to a 400% decrease in VUV reflectivity compared to bare silicon. The fellow will deposit graphene films on photodiodes and SiPMs and test the efficacy of graphene as an ARC at optical, UV, and VUV wavelengths. II) A backside-illuminated (BSI) structure: BSI design can improve PDE by increasing the device fill factor to close to 100%, as well as improving compatibility with 3D-integrated digital readout architecture. Production of BSI SiPMs is ongoing as part of the CERN DRD2 and DRD4 collaborations - the fellow will contribute to the design and characterisation effort, develop simulation software to optimise VUV PDE, and incorporate graphene coatings on a BSI device. Devices will be tested in liquid Argon to test their response to LAr scintillation light.This project will contribute significant technological developments to an area which has been identified as critical for next-generation particle physics detectors, and will operate fully embedded in the existing community for particle detector R&D.