Diffusion barriers at mercury--cadmium--telluride/metal interfaces: The case of Hg/sub 1-//sub x/Cd/sub x/Te(110)/Yb/Al

The rare-earth metals Yb and Sm show unique reactive behavior on mercury--cadmium--telluride (MCT) surfaces, due to the large rare-earth affinity for both Hg and Te. Semiempirical calculations of thermodynamic parameters using Miedema's model suggest that the rare earths should act as effective diffusion barriers at the interface between MCT and prototypical reactive metals such as Al, In, or Cr. We present here a synchrotron radiation photoemission investigation of the effect of Yb interlayers at the Hg/sub 1-//sub x/Cd/sub x/Te(110)/Al junction. Our results indicate that layers of Yb are effective in preventing Al--Te reaction and reducing the Al-induced mercury depletion of the substrate. Our data confirm that such a diffusion barrier effect is the result of the superior thermodynamic stability of the MCT/Yb reaction products at the interface