Measuring the transmission yield of ultra-thin membranes

Abstract

The goal of this research is to characterize thin membranes used as transmission dynodes (tynodes) for electron multiplication. A stack of tynodes could be used in a novel ultra fast soft photon counter. A combination of a charge sensitive TimePix1 CMOS chip and a pulsed electron gun were used as part of a setup deemed Tytest. The pixel chip was calibrated using a surrogate function that is fitted to the single pixel responses of 76 different pixels. The calibration is used to perform Transmission Secondary Electron Yield (TSEY) measurements on a 20 nm thick alumina membrane. The maximum TSEY value observed is 2.76 ± 0.64 for a incident energy of 1675 eV. The maximum TSEY value seems to be at higher incident energies which cannot be reached using our setup. A unexplained spread in electrons being emitted by the tynode is observed.
The second part of this research was to create a stack of tynodes which can be used to convert a single electron into a measurable signal. The goal is to stack the tynodes using a self aligning mechanism and measure the misalignment. A ZEISS Axio-zoom V16 light microscope in combination with two µm precision manipulators placed in a clean room at Nikhef in Amsterdam is setup in this research used to stack tynodes. The aim was to have a misalignment better than 5 µm, and this setup a misalignment of 4.1±1.3 µm was measured. It’s important to note that only the misalignment between two tynodes is measured, since no more were readily available.