Visual inspection revealed dark spots on MCP7 after testing at up to 3kV (in series with MCP8):

3 darkspots

What are the dark spots?How far into pores does gold electrode extend?

Structure of MCP7, MCP8:100 nm ALD AZO resistive layer

80 nm NiCr + 200 nm Au electrodes6 nm ALD Al2O3 emissive layer

SEM of the 3 dark spots:

Gold electrode has melted and de-wetted the MCP surface. Also, gold has solidified into ~1 micron spherical droplets

Gold droplets on inside wall of MCP channel

In dark spots, gold also melted inside of MCP channels

Local heating (from arcs?) melted gold electrodes at dark spots. Dark color might result from the finely dispersed gold droplets (similar to black metal powder)

How far into MCP channels does gold film extend?

gold film shows morphology of coalesced islands

gold film visible up to 40 microns deep into the 40 micron pores

Cross-section of cleaved MCP (the pores here are not cleaved through the middle, so the cross section is only ~20 microns wide instead of 40 microns).

Au

Al Zn

SEM and EDAX Elemental Mapping of 1 Pore in MCP

Pore wall is rich in Al and Zn as expected for ALD AZO coatingGold film here extends ~20 microns into pore.“Tail” structure of gold film is because MCP was not rotated during gold evaporation.

singlepore