ELECTRONIC-PROPERTIES OF EPITAXIAL TIN VN(001) SUPERLATTICES

Single-crystal TiN/VN superlattices with layer thicknesses l(TiN) = l(VN) and period LAMBDA ranging from 0.96 to 12.4 nm have been grown on MgO(001) substrates at 750-degrees-C by reactive magnetron sputtering. The superlattice structures had uniform layer thicknesses as observed by cross-sectional transmission electron microscopy and a comparison of x-ray superlattice diffraction spectra with calculated spectra indicated that any interfacial mixing had to be less than +/- three atomic layers, (i.e., < +/- 0.6 nm). Electrical resistivity and Hall measurements carried out as a function of LAMBDA showed that the room-temperature electron carrier concentration n remained constant at 4.5 x 10(22) cm-3 while the resistivity rho-increased and the electron mobility mu-decreased rapidly with LAMBDA < 6 nm. For superlattices with longer periods, rho approximately 30-mu-OMEGA cm, the expected value for bulk TiN and VN connected in parallel, and mu approximately 5 cm2 V-1 s-1. The temperature coefficient of resistivity between 80 and 300 K decreased with decreasing LAMBDA but remained positive (i.e., metallic). A modified quantum size effect model accounting for diffuse and specular scattering of electrons at superlattice interfaces was used to explain the electronic transport properties. Best fit results showed that the fraction of specularly scattered electrons was approximately 0.3.