A method for depositing, by microwave plasma enhanced chemical vapor deposition, a modified, silicon oxide, barrier coating atop a temperature sensitive substrate; said barrier coating having barrier properties to at least gaseous oxygen and water vapor. The precursor gaseous mixture includes at least a silicon-hydrogen containing gas, an oxygen containing gas and a gas containing at least one element selected from the group consisting of germanium, tin, phosphorus, and boron. The method requires introducing a sufficient flow rate of oxygen-containing gas into the precursor gaseous mixture to eliminate the inclusion of silicon-hydrogen bonds into the deposited coating. The preferred modifier is germanium. Also, a composite material having a microwave-plasma-enhanced-chemical-vapor-deposited silicon oxide (modified or non-modified) barrier coating. The barrier coating has barrier properties to at least gaseous oxygen and water vapor and is substantially free of Si-H bonds. The barrier coating is deposited by the instant method on a temperature sensitive substrate.