Ultra-thin corrugated metamaterial film as large-area transmission dynode

Abstract

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 metamaterials, 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 (Al2O3/TiN/Al2O3) 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 Al2O3/TiN/Al2O3 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.

Measurement of the transmission secondary electron yield of nanometer-thick films in a prototype Timed Photon Counter

“…The agreement between the yield curve obtained in this work and that obtained in [6] is good. However, at landing energies of 1.7 and 1.8 keV we observe some outliers.…”

“…Using the approach outlined in the previous section, we measure the yield of the thin-film-covered windows as a function of landing energy. The results of this measurement are plotted in figure 8 and compared to yield measurements obtained in [6] from a SEM-based method presented in [4,5]. In this figure, we have removed the results for windows (0, 3), (3, 0) and (3, 3) (see figure 4a).…”

“…The scattered dots correspond to our measured values, using the same colouring and markers as presented in figure 4 for spot identification. We compare our data to the yield obtained in [6] by a SEM-based method presented in [4,5] (dashed line). The inset shows the full yield-curve obtained by this method.…”

“…The last window is left open as a reference. The covered windows are schematically depicted in figure 3b and their fabrication is described in [6]. SEs are created in the Al 2 O 3 layers with respective thicknesses of 10 and 15 nm.…”

“…Previously, tynodes have been fabricated with a (transmission SE) yield up to 5.5 [3][4][5][6]. In this work we take the next step in the realisation of TiPC by combining two of the three main components.…”