Origin of contaminants in photochemically deposited chromium films

A systematic investigation of the composition of Cr films deposited by cw 257 nm photolysis of Cr(CO)6 has been performed in order to identify sources of C and O contamination. In the absence of oxygen, the films have the approximate stoichiometry CrCO, independent of light intensity (40-2900 W/cm2). Five carbonyl groups are removed by a combination of surface photochemical and spontaneous processes; the sixth cannot be desorbed in the absence of heating. Deposits grown by purely gas phase photolysis have the approximate composition Cr(CO)2. Oxygen containing species present in the cell during deposition and/or exposure to air rapidly and efficiently convert these films to Cr2O3.