Yuh Fukai

Influence of hydrogen on room temperature recrystallisation of electrodeposited Cu films: thermal desorption spectroscopy

Abstract The mechanism of recrystallisation observed at room temperature in electrodeposited Cu films has been examined in light of the enhancement of metal atom diffusion by hydrogen induced superabundant vacancies. Thermal desorption spectroscopy revealed that Cu films electrodeposited from acid sulphate bath containing some specific additives showed a pronounced peak, which was ascribed to the break-up of vacancy–hydrogen clusters. The amount of desorbed hydrogen was comparable to that of vacancy type clusters estimated in previous positron annihilation experiments. The grain size of Cu films increased as hydrogen desorption proceeded. Such grain growths were not observed in the films deposited from the baths without additives. These results indicate that the room temperature recrystallisation of electrodeposited Cu films is caused by hydrogen induced superabundant vacancies.

Hydrogen-Induced Superabundant Vacancies in Metals: Implication for Electrodeposition

The equilibrium concentration of vacancies in metals is invariably enhanced in the presence of interstitial hydrogen atoms – a phenomenon called superabundant vacancy (SAV) formation. It has been recognized that the SAV formation occurs in electrodeposition, as M-, H-atoms and M-atom vacancies are deposited by atom-by-atom process. Effects of SAV formation are described for electrodeposited Ni, Ni-Fe alloys, Fe-C alloys and Cu. Possible implication of SAV formation for corrosion in Al and steels is also briefly described.

Hydrogen-Induced Enhancement of Atomic Diffusion in Metals

Atomic diffusion in metals is invariably enhanced by dissolution of hydrogen, in some cases by many orders of magnitude. This is a consequence of the formation of superabundant vacancies (SAVs), one of the general properties of M-H systems. Some examples of H-induced enhancement of interdiffusion in alloys and a detailed investigation of self-diffusion in Nb hydride, NbHx, are described, together with accelerated atomic migration observed in electrodeposited metals, also a consequence of SAV formation in the electrodeposition process.