NOVELTY - Synthesizing a thin film or composition layer from precursor layers (14) supported on a substrate (12), involves exposing the precursor layers to non-contact pressure; and heating the precursor layers under the non-contact pressure to a reaction temperature to promote the formation of the film or composition layer. Each of the precursor layers is selected from elemental series of the periodic table consisting of Group I elements, Group III elements, and/or Group VI elements. The non-contact pressure is fluid pressure.    USE - For synthesizing a thin film or composition layer from precursor layers supported on a substrate (claimed) used in various applications such as in optoelectronic devices including photovoltaic devices such as solar cells.    ADVANTAGE - The process for synthesizing a film or composition layer via non-contact pressure containment provides precise control over the reaction thermodynamics and precise material grading profiles across the film thickness. In this manner, the process achieves a film or composition layer of favorable crystalline structure, nanostructure and desirable electronic properties, especially for use in photovoltaic applications. The process facilitates the synthesis of films or composition layers of desired crystalline structure, nanostructure and electronic properties using precursor layers deposited on a substrate, and non-contact pressure containment. The process provides at least two precursor layers deposited in a stacked or laminate arrangement on a substrate. The process promotes chemical and/or physical interaction between adjacent precursor layers to produce the resulting film or composition layer. The process promotes interaction between adjacent precursor layers to produce the resulting film or composition layer. The process separates the material deposition and reaction process into two discrete steps for improved management of the process requirements for each step. This facilitates better control of the composition, structure and deposition of the precursor layers on a substrate, and optimization of the chemical and/or physical reactions forming the final film or composition layer (e.g. product layer).    DETAILED DESCRIPTION - Synthesizing a thin film or composition layer from precursor layers (14) supported on a substrate (12), involves exposing the precursor layers to non-contact pressure; and heating the precursor layers under the non-contact pressure to a reaction temperature to promote the formation of the film or composition layer. Each of the precursor layers is selected from elemental series of the periodic table consisting of Group I elements, Group III elements, and/or Group VI elements. The non-contact pressure is fluid pressure. The fluid pressure is gas pressure. The exposing step further involves enclosing precursor layers in a closed volume; and increasing the pressure within the closed volume to generate the non-contact pressure. The pressure increasing step further involves supplying a fluid into the closed volume, so that the pressure within the closed volume increases. The pressure increasing step further involves adding a vaporizable material in association with the precursor layers within the closed volume; and vaporizing the vaporizable material within the closed volume to generate the non-contact pressure. The vaporizable material is selected from the elemental series of the periodic table consisting of Group I elements, Group III elements, and/or Group VI elements. The vaporizable material is selected from indium, gallium, selenium, copper, sulfur, and/or sodium. The process further involves depositing the precursor layers on a substrate.    DESCRIPTION OF DRAWING(S) - The figure shows assembly view of a reaction containment assembly or reactor with precursor layers supported on a substrate.    Reaction containment assembly or reactor (10)    Substrate (12)    Precursor layers (14)    Base portion or sample carrier (16)    Upper portion or cover plate (18)    Sidewall (20)    Central area (22)    Top end of the sidewall (24)    Vaporizable material layer (26)