Deposition of iron, nickel and iron-nickel layers from carbonyl vapors

Abstract

The rate of deposition of iron, nickel and iron-nickel layers from carbonyl vapors is shown to be controlled by diffusion across the gas phase boundary layer in contact with the heated substrate. At a constant flow rate the rate of deposition is shown to increase with increase in temperature up to a critical value above which the rate of deposition either remains constant (for high flow rates) or decreases (for low flow rates). This behavior is explained in terms of the thermal convection contribution to mass transfer in the reaction system. It is shown that the composition of alloy films produced from carbonyl mixtures at temperatures greater than 200°C (473 K) can be predicted to be approximately equal to the molar ratios of iron and nickel in the vapor phase when the carbonyls alone constitute the vapor phase. These predictions cannot be extended to situations where high dilution of the carbonyls in another gas is used, or to deposition temperatures of less than 200°C (473 K).