SIMPLIFIED PROCESS TO ACHIEVE UNIFORM COMPOSITION PHOTOCONDtJC- TIVE FILMS
Original Publication Date: 1977-Aug-31
Included in the Prior Art Database: 2004-Mar-30
Xerox Disclosure Journal
A method for producing an alloy, e.g., an arsenic-selenium alloy, of uniform composition is disclosed. Methods for pro-ducing alloys of uniform compositions by known techniques, such as flash evaporation and co-evaporation or partial evap-oration are not always amenable to mass production techniques. Since arsenic-selenium alloys of various compositions are routinely used as photoconductors for xerographic applica-tions, these alloys are routinely produced by thermal evapor-ation in a vacuum. The alloys fractionate during the evapor-ation resulting in a composition gradient throughout the film, e.g., arsenic is concentrated at the surface. Control of the fabrication process is generally difficult. Therefore, it is suggested that an evaporation boat be designed and operated in such a way which will permit alloys of constant arsenic composition to be formed. More specifically, the process involves the evaporation of congruently evaporating components simultaneously from different compartments of the same source boat. Since the vapor pressure of selenium is higher than that of arsenic triselenide, the method is especially amenable to fabricating photoconductors with low arsenic context. By adjusting the area of the compartments, it is possible to adjust the composition of the condensing vapor to whatever arsenic content is desired. This method thus eliminates the alloy fractionation by using materials which vaporize congruently, e.g., selenium and arsenic triselenide. This method does not require separate source boats for each component as in conventional co-evaporation.