Atomic Layer Depositionfor 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 (x104-107)

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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

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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

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33 mm

MCP Structure

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1) resistive coating (ALD)2) emissive coating (ALD)3) conductive coating (thermal

evaporation or sputtering)

pore

ALD for Resistive Coating

Target: 10-100 MΩ through MCP ZnO: conductor Al2O3: insulator

ZnO/ Al2O3 alloy – tunable resistivity

Tune composition and thickness of film to adjust MCP resistance

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ALD for Emissive Coating

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Many material possibilities Tune SEE along pore

SiO2Al2O3

MgO

ZnO

Cross-Sectional Elemental Maps of ALD MCP

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Zn

SEM Si

Al Au

ALD ZnO and Al2O3 extend into pores

Sputtered Au only on edge of pores

Glass capillary plate ALD ZnO/Al2O3

Sputter gold electrodes

Cross-Sectional Image of ALD Film in MCP

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ALD Film

100 nm ALD film visible in middle of MCP

Glass

Questions?

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