Methods are described for depositing a film or discontinuous layer of discrete clusters, of material (e.g., metals, metal mixtures or alloys, metal oxides, or semiconductors) on the surface of a substrate, e.g., a patterned silicon wafer, by i) dissolving a precursor of the material into a supercritical or near-supercritical solvent to form a supercritical or near-supercritical solution; ii) exposing the substrate to the solution, under conditions at which the precursor is stable in the solution; and iii) mixing a reaction reagent into the solution under conditions that initiate a chemical reaction involving the precursor, thereby depositing the material onto the solid substrate, while maintaining supercritical or near-supercritical conditions. The invention also includes similar methods for depositing material particles into porous solids, and films of materials on substrates or porous solids having material particles deposited in them. The invention also covers methods of preparing a plated substrate by depositing a catalytic layer followed by a plating layer.