Agglomeration and diffusion of Ag associated with electrical contacts on single crystal Bi < inf > 2 < /inf > Sr < inf > 2 < /inf > CaCu < inf > 2 < /inf > O < inf > y < /inf >

Abstract

For the purpose of obtaining good small-area electrical contacts on single crystals of Bi2Sr2CaCu2Oy (Bi-2212) for transport study, the nature of the Ag film on a Bi-2212 single crystal was examined. Ag films of ∼ 100 nm thickness deposited on cleaved surfaces of Bi-2212 crystals and annealed at 500°C have been studied for microstructural changes and diffusive behavior by scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA). It is found that the Ag films undergo a thermally activated softening/roughening on annealing. On prolonged annealing, film break-up and segregation takes place, accompanied by a small diffusion of Ag into and along the surface of Bi-2212. Based on these results, a method for electrical contact formation on a Bi-2212 crystal cleaved surface is presented.