Sealable stagnation flow geometries for the uniform deposition of materials and heat

A method for minimizing the consumption of reactant species in a gas deposition process, comprising the steps of:

• a.) causing a reactant gas to flow into a gas reactor about a central axis of a gas inlet, creating a flow directed substantially perpendicular to a substrate planar surface such that a stable axisymmetric staganation gas flow is established radially across and generally parallel with said planar surface, said reactant gas entering said inlet having a substantially uniform and radially invariant temperature, velocity and composition, and axisymmetric stagnation gas flow delivering a radially uniform material flux to said planar surface;
• b.) maintaining said substrate at a substantially uniform temperature;
• c.) constraining said axisymmetric stagnation gas flow to within a critical radius as said reactant gas exits said gas inlet thereby providing a constrained axisymmetric stagnation gas flow, said constrained gas flow bounded by a boundary streamline at said critical radius;
• d.) placing said substrate at a fixed distance from said gas inlet such that a reaction zone is established proximal to, and parallel with, said planar surface, said reaction zone extending radially outward to said boundary streamline;
• and
• e.) adjusting said critical radius such that said boundary streamline intercepts an edge of said substrate planar surface thereby establishing a maximum deposition area while minimizing consumption of said reactant gas during said gas deposition process.