Atomic Layer Deposition for Microchannel Plates Jeffrey Elam Argonne National Laboratory September 24, 2009

Atomic Layer Deposition (ALD) Layer-by-layer thin film coating method Atomic level control over thickness and composition Precise coatings on 3-D objects Deposit nearly any material (oxides, nitrides, metals, etc.) Example: ALD Zinc Oxide in deep trenches

Large Area Photodetector Microchannel Plate (MCP) –Electron amplifier (x ) 3

Microchannel Plates (MCPs) Conventional Fabrication: –Draw glass fiber bundle –Slice and polish –Chemical etch, heat in hydrogen Problems: –Expensive –Resistance and secondary emission properties are linked –Long conditioning process needed –Thermal runaway 4

ALD for Fabrication of MCPs Start with porous, insulating substrate –Glass capillary plate –Anodic aluminum oxide (AAO) membrane ALD of resistive film on all surfaces (inside of pores, on faces, etc.) ALD of secondary electron emissive film Deposit metal electrodes on outer surfaces 5 33 mm

MCP Structure 6 1)resistive coating (ALD) 2)emissive coating (ALD) 3)conductive coating (thermal evaporation or sputtering) pore

ALD for Resistive Coating Target: MΩ through MCP ZnO: conductor Al 2 O 3 : insulator ZnO/ Al 2 O 3 alloy – tunable resistivity Tune composition and thickness of film to adjust MCP resistance 7

ALD for Emissive Coating 8 Many material possibilities Tune SEE along pore SiO 2 Al 2 O 3 MgO ZnO

Cross-Sectional Elemental Maps of ALD MCP 9 Zn SEM Si Al Au ALD ZnO and Al 2 O 3 extend into pores Sputtered Au only on edge of pores Glass capillary plate ALD ZnO/Al 2 O 3 Sputter gold electrodes

Cross-Sectional Image of ALD Film in MCP 10 ALD Film 100 nm ALD film visible in middle of MCP Glass

Questions? 11