The effect of oxygen adsorption on Cu{111} thin film growth stresses

Thin film stress evolution during physical vapor deposition is highly sensitive to the exact nature of the growth environment. It has been previously observed that during the growth of Cu films, stress evolution is acutely affected by oxygen partial pressure. However, changes in partial pressure imply a number of changes to the growth environment and to the condition of the growth surface. To specifically examine the role of adsorption on growth stresses, in this work we have grown Cu Volmer-Weber films, adsorbed a known quantity of oxygen, and continued growth once ultrahigh vacuum conditions were again achieved. This enabled the study of stress evolution as a function of adsorbate coverage, independent of background pressure. We found that even at low coverages, adsorbed oxygen has a profound impact on stress evolution. Additionally, we found that the adsorbed oxygen is consumed by the growing film over a significant thickness of growth and we have extracted the rate of oxygen consumption. We also observed an epitaxial stress associated with the continued growth of Cu on the underlying strained O-dosed Cu film, and show that the reversible stress is apparently unaffected by the oxygen adsorption step.