Polymer films formed with monolayer growth steps by molecular layer deposition

Molecular layer deposition is the process in which molecules are stacked on substrates one by one in order of preference in a vacuum. We studied the possibility using two kinds of molecules: pyromellitic dianhydride (A) and 2,4-diaminonitrobenzene or 4,4′-diaminodiphenyl ether (B). After forming a layer consisting of A (or B), we supplied molecule B (or A). The film rapidly thickened and became saturated in 10–60 s. The change in thickness induced in this step was about 5 Å, close to the size of the molecules involved. This indicates that a monomolecular layer of B (or A) grew on layer A (or B) and film growth self-terminated automatically. 15 steps of alternately supplying A and B produced a polymer film 100 Å thick.