Formation of the equilibrium intermetallic compound NiZr in sputter deposited Ni/Zr diffusion couples is suppressed by the formation of a metastable amorphous NiZr alloy until a critical thickness of the amorphous NiZr interlayer is reached. The temperature dependence of this critical thickness is studied experimentally. A phenomenological model based on the premise of interfacial heterogeneous nucleation is proposed to understand the evolution of Ni/Zr diffusion couples.

We report the first experimental observation of negative differential resistance (NDR) due to electron tunneling in a single barrier heterostructure. The largest peak-to-valley current ratio attained is slightly greater than 2:1. The single barrier structure studied here consists of a thin CdTe layer sandwiched between two Hg0.78Cd0.22Te electrodes. In this particular material system, NDR can only be achieved at low temperatures (T=4.2 K) due to the dominance of thermionic hole currents at high temperatures. The observation of NDR in this system suggests that the low-temperature valence-band discontinuity at the HgTe-CdTe interface is small (less than 100 mV). Room-temperature operation of single barrier NDR structures may be possible in other semiconductor systems.

Experimental and theoretical studies of angular resolved uv photoemission from singlecrystal surfaces of copper

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Cubic phase Y 2 O 3 films 1.6-10 nm thick of excellent quality have been epitaxially grown on Si ͑111͒ with Y 2 O 3 ͑111͒ ʈ Si͑111͒ using electron beam evaporation of Y 2 O 3 in ultrahigh vacuum. Structural and morphological studies were carried out by x-ray scattering and reflectivity and high-resolution transmission electron microscopy, with the growth being in situ monitored by reflection high energy electron diffraction. There are two Y 2 O 3 domains in the initial stage of the oxide growth with equal population, and the B-type domain of Y 2 O 3 ͓211͔ ʈ Si͓112͔ becomes predominating over the A-type domain of Y 2 O 3 ͓211͔ ʈ Si͓211͔ with increasing film thickness. Besides the excellent crystallinity of the films as derived from the small-rocking curve width of 0.014°, our results also show atomically sharp smooth surface and interfaces.