  Large-area transmission dynodes were fabricated by depositing an ultra-thin
continuous film on a silicon wafer with a 3-dimensional pattern. After removing
the silicon, a corrugated membrane with enhanced mechanical properties was
formed. Mechanical materials, such as this corrugated membrane, are engineered
to improve its strength and robustness, which allows it to span a larger
surface in comparison to flat membranes while the film thickness remains
constant. The ultra-thin film consists of three layers (Al$_2$O$_3$
/TiN/Al$_2$O$_3$) and is deposited by atomic layer deposition (ALD). The
encapsulated TiN layer provides in-plane conductivity, which is needed to
sustain secondary electron emission. Two types of corrugated membranes were
fabricated: a hexagonal honeycomb and an octagonal pattern. The latter was
designed to match the square pitch of a CMOS pixel chip. The transmission
secondary electron yield was determined with a collector-based method using a
scanning electron microscope. The highest transmission electron yield was
measured on a membrane with an octagonal pattern. A yield of 2.15 was achieved
for 3.15 keV incident electrons for an Al$_2$O$_3$ /TiN/Al$_2$O$_3$ tri-layer
film with layer thicknesses of 10/5/15 nm. The variation in yield across the
surface of the corrugated membrane was determined by constructing a yield map.
The active surface for transmission secondary electron emission is near 100%,
i.e. a primary electron generates transmission secondary electrons regardless
of the point of impact on the corrugated membrane.
