Patented Superfinishing Method

Conventional machining  of a raw Single Crystal Si boule induces surface and subsurface damage.  Our patented superfinishing method provides a finish with ≤5um of subsurface damage ready for single point diamond turning and final polishing. 

Surface finish directly affects the performance of Single Crystal Si.  Damage on the surface affects thermal-optical properties like transmission, absorption and reflection, while subsurface damage affects thermal-mechanical properties like strength, microyield, hardness, and fracture toughness.  The surface and subsurface damage introduced during rough and intermediate machining and grinding operations extends deeper than etching and polishing alone can remove therefore the McCarter superfinishing method is critical for producing top quality optics and optical structures.

 Superfinishing on a Conical surface

Superfinishing on a Conical surface

Our patented superfinishing method allows us to offer a material, Single Crystal Si, that inherently does not creep or jitter, is thermally and optically stable, and is ready to perform and endure in hostile environments.

In addition, our finishing process yields components that are near net shaped reducing or completely eliminating the time and cost of lapping and pre-polishing. 

As shown in the table from Argonne National Laboratory, only a thin layer of damage remains after the McCarter superfinishing method which can then be easily removed by acid etching.

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 Results from tests performed at Argonne National Lab

Results from tests performed at Argonne National Lab

 Single Crystal Si Boule

Single Crystal Si Boule

The key to producing stress-free Single Crystal Si components is the starting material.  We use only zero-defect, near perfect single crystal boules that are free of residual stress. This enables rapid machining with conventional CNC machines and tools.  Boules are readily available from several suppliers in sizes to 300mm diameter and 800mm long. Larger sizes have also been drawn, but frit bonding makes it possible to build up blanks to sizes in excess of one meter.

Bonded Single Crystal Si Planks with Finished Ring above