MCP: Fabrication with Borosilicate Glass (Glass Capillary Array)

ALD MCP Manufacturing

The ALD MCP manufacturing process begins with the creation of glass capillary arrays (GCAs). Borosilicate glass is drawn into hollow capillary tubes, similar to the process used for conventional MCPs. The fibres are bundled together and fused in parallel, then sliced into flat plates to form the GCAs. This process differs from conventional MCP manufacturing in that the glass fibres are hollow, eliminating the need for a core etching step and making the manufacturing process more cost-effective. A thin film is added to the GCA to establish the plate resistance, followed by another layer to create a secondary emission layer, transforming the GCA into an MCP.

Atomic Layer Deposition (ALD)

ALD is a thin film deposition technique chosen for its ability to coat the inside surfaces of high length-to-diameter ratio capillaries, a feat not achievable with conventional line-of-sight coating techniques like vacuum evaporation or sputtering.

ALD MCP Thin Film Layers

  • Resistive Layer: This layer, approximately 0.1μm thick, is deposited using ALD and establishes the DC or strip current through the MCP. The resistance level can be adjusted depending on the intended application. This layer is typically composed of a metal oxide, such as aluminum oxide (high resistance), and a metal, such as tungsten (low resistance).
  • Secondary Electron Emission (SEE) Layer: Applied over the resistive coating, this layer serves as the innermost surface of the pore and can be made of materials like Al(2)O(3) (good long-term gain stability) or MgO (higher gain).
  • Nichrome Electrode Layer: This layer is deposited on the top and bottom surfaces of the MCP to control the potential and provide a pathway for restoring charge to the MCP pores.

Advantages of ALD MCPs

  • Independent Selection: The glass, resistive, and emissive properties can be selected independently, allowing for greater control over the MCP characteristics.
  • Enhanced Robustness: ALD-coated MCPs exhibit increased robustness compared to conventional MCPs because the glass substrate can be chosen for its desired mechanical properties.
  • Curved Formats: The ALD approach allows for the creation of curved, non-planar MCPs.

ALD MCPs represent a significant advancement in MCP technology, offering several advantages over traditional methods and opening up possibilities for novel applications.