NOVELTY - The method comprises contacting a first bonding surface of a first substrate with a second bonding surface of a second substrate to form an assembly in an atmosphere comprising steam and oxygen, under suitable conditions to form a bonding layer between the first surface and the second surface, and optionally compressing the assembly, where the first bonding surface comprises a polarized surface layer. The second bonding surface comprises a hydrophilic surface layer. The first and second bonding surfaces are different. The first and second substrates are wafers or beads.    USE - The method is useful for bonding substrates such as silicate wafers to form a bonded substrate, which is useful in a implantable medical device, a solar cell (all claimed), glass panel photovoltaic panels and biosensors.    ADVANTAGE - The method is capable of economically and simply bonding substrates with high uniformity, hermeticity and strength of bond and without any surface contamination of the substrates.    DETAILED DESCRIPTION - The method comprises contacting a first bonding surface of a first substrate with a second bonding surface of a second substrate to form an assembly in an atmosphere comprising steam and oxygen, under suitable conditions to form a bonding layer between the first surface and the second surface, and optionally compressing the assembly at a pressure of 1-1.1 atm and at a temperature of 25-200 degrees C, where the first bonding surface comprises a polarized surface layer, the second bonding surface comprises a hydrophilic surface layer and the first bonding surface and the second bonding surface are different. The first and second substrates are wafers or beads. The atmosphere comprising steam and oxygen is water saturated air, and has 80-100% of relative humidity. The compressing step is maintained for 1-2 hours. The first surface and the second surface are essentially flat. The bonding layer has a bonding strength of 8-12 MPa. The first substrate and the second substrate are silicate wafers. The first bonding surface is formed by cleaning the silicon wafer with the Herbots-Atluri clean. The second bonding surface is formed by chemical etching followed by chemical oxidation of the silicate wafer.    DESCRIPTION OF DRAWING(S) - The figure shows high resolution transmission electron micrographs of silicon dioxide formed on silicon wafers prepared using different cleaning techniques.