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Abstract

A grating light valve with reduced surface charging is disclosed. Surface charging is measured by the propensity an insulating surface to accept and transport a charge. The grating light valve of the instant invention has a plurality of spaced and movable ribbons formed from Si.sub.3 N.sub.4 coupled to a substrate structure formed of SiO.sub.2. A portion of the ribbons are moved to alternate between conditions for constructive and destructive interference with an incident light source having a wavelength .lambda. by applying the appropriate switching voltages across the portion of ribbons and the substrate structure. When charging occurs on surfaces of the grating light valve, the switching voltages required to operate the grating light valve are shifted and diminishing the performance of the grating light valve. By drying silicon-based surfaces of the grating light valve and exposing the silicon-based surfaces of the grating light valve to a Nitrogen-rich pacify gas environment, the surfaces of the grating light valve exhibit reduced charging and consistent response to applied bias voltages. In the drying step, residual water or moisture is removed from the surfaces by elevating the temperature of the grating light valve structure in a vacuum environment. Preferably, the drying is carried at temperatures of 250 degrees Celsius or greater and at vacuum pressures of 10.sup.-6 Torr or less. After the surface of the grating light valve are dried, the surfaces are exposed to the Nitrogen-rich pacifying gas environment at ambient temperature. Presumably, the Nitrogen-rich pacify gas environment blankets the silicon-based surfaces of the grating light valve with adsorbed, physisorbed, or chemi-adsorbed Nitrogen and thus reduces the propensity of those surfaces to accept water or moisture, which is believed to facilitate the charging. After the surfaces of the grating light valve are treated according to the current invention, charging of the surface remains low and stable even for several days in open air conditions.

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First Claim