Control of the deposition of metals on the surfaces of conjugated polymers determines the electronic properties of the electrical contacts. The detrimental effects arising from the physical vapor deposition of metal atoms on conjugated polymer surfaces can be controlled by using a carefully chosen intermediate ultrathin layer of a "protection material." In particular, the influence of an intermediate layer of barium atoms on the chemical effects that occur when aluminum atoms are deposited on the surfaces on substituted poly(p-phenylenevinylene)s has been studied using x-ray and ultraviolet photoelectron spectroscopy. In order to render the results somewhat more general, a series of substituted poly(p-phenylenevinylene)s was used, each with bulky side groups containing at least one oxygen atom, and the results presented are generalized beyond one particular substituted polymer system.