Impurity segregation at well-defined interfaces: Sulphur at (111)Cu(110)Mo and (111)Ag(110)Mo interfaces
✍ Scribed by J.M Moison; J.L Domange; J Oudar
- Publisher
- Elsevier Science
- Year
- 1978
- Weight
- 512 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0001-6160
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✦ Synopsis
and Cu/Mo interfaces are created by evaporating a silver (or copper) thin film onto a (1 IO) molybdenum single crystal. Growth takes place according to epitaxial relations and the interface is expected to be as coherent and clean as possible. Both samples are stable at all temperatures. in vacuum or in Hz. even under fast quenching or very long annealing. Under exposition to H&H, mixtures. sulphur adsorbs on silver (or copper), diffuses through the thin film, and segregates at the interface. The segregated quantity. as measured by radiotracer techniques through the thin film. is found to be about one sulphur monolayer (7 x IO'* at/cm') in both cases at low sulphur chemical potential. Such quantities, and the very accuracy of the results, indicate that segregated atoms are located precisely at the interface and even organized as a true monolayer, bound to silver (or copper) and molybdenum on its both sides. The presence of sulphur at Cu/Mo interfaces then induces a decomposition of the film into small crystallites which wet only partially the molybdenum substrate. Under classical assumptions. contact angle measurements lead to values of the shift of the interfacial energy caused by the segregated sulphur la>:r. R&urn&--On a fabriqui des interfaces Ag,'Xlo et Cu/Mo en tvaporant de I'argent (ou du cuivre) sur un monocristal (I IO) de molybd6ne. La croissance se produit par epitaxie, et l'on s'attend g obtenir un interface aussi cohirent et propre que possible. Les deux types d'ichantillons sont stables g toutes tempkratures, dans le vide ou dans I'Hz. m&me dans le cas d'une trempe rapide ou d'un tr6s long recuit. Par exposition g des mClanges H&H?, le soufre est adsorb6 sur I'argent (ou le cuivre). il diffuse g travers la couche mince et se sCgrtge a I'interface. La quantitt: s&rtgte, mesuree B travers la couche mince par des techniques de radiotraceurs correspond, dans les deux cas et pour un potentiel chimique du soufre faible. B une couche atomique de soufre environ (7 x 10" at&m'). Compte tenu de leur grande pr&ision, ces resultats montrent que les atomes segrtges sent situ& tr6s precisement sur I'interface, ou mtme qu'ils constituent une vCritable couche monoatomique, lice de part et d'autre B I'argent (ou au cuivre) et au molybdene. La pr&ence du soufre aux interfaces Cu/Mo produit une decomposition du film en petits cristallites qui ne mouillent que partiellement le substrat de molybd&ne.