Deposition system with vacuum pre-loaded deposition head

A thin film deposition system includes a vacuum-preloaded gas bearing deposition head positioned in an external environment having an ambient pressure, the deposition head having an output face including a plurality of source openings through which gaseous materials are supplied and one or more exhaust openings. An exhaust pressure at the exhaust openings is less than ambient pressure, and a source pressure at the source openings is greater than that at the exhaust openings, with the pressure at the outermost source openings being greater than ambient pressure. A motion control system moves a substrate unit over the output face in the in-track direction without constraining its motion in a direction normal to the output face to a point where a center of gravity of the substrate unit is beyond the first edge of the output face.