Chromium exhibits (110) textured growth on Al2O 3(0001) substrates induced by epitaxy. Epitaxy occurs in nine distinct orientations, leading to a polycrystalline film of grains with (110) out-of-plane orientation but different in-plane orientations. For e-beam evaporated films, scanning electron microscopy shows acicular Cr grains elongated in the 001 direction. Grain boundaries occur along (1 1 0) and (1 10) planes, which is explained by the low surface energy of {110} planes in the bcc structure. The direction of the long axes of the grains relative to the substrate is defined by the underlying hexagonal symmetry of the substrate, leading to a unique tri-directional microstructure. © 2013 AIP Publishing LLC.

The spin-density wave properties of polycrystalline chromium thin films were determined by using infrared reflectivity to determine the gap energies. The incommensurate spin-density wave of bulk chromium is highly sensitive to perturbations from stress, disorder, and finite size effects, such as those found in polycrystalline films. Films prepared under various conditions display three different types of spin-density wave behavior: incommensurate, commensurate, and mixed. Unexpectedly, the mixed phase includes the incommensurate spin-density wave and two different forms of commensurate spin-density wave. A phenomenologically determined low-temperature phase diagram is created to describe the spin-density wave in chromium in the stress-disorder plane. The effects of stress and disorder on the spin-density wave of chromium films are analogous to the effects of dilute alloying in bulk chromium. In this case, tensile stress has a similar effect to Mn impurities, while disorder has a similar effect to Al. © 2007 The American Physical Society.

The resistivity as a function of temperature from 0.6 to 300 K for epitaxial and polycrystalline Cr thin films is presented and fit to a model which includes electron-phonon scattering and resonant impurity scattering. Resonant impurity scattering from localized defect states in the spin-density wave gap leads to very high residual resistivity (up to 400 μΩcm) and a minimum at low temperatures (below 100 K). This is strong experimental evidence for resonant impurity scattering due to defects in pure Cr rather than dopant atoms. The magnitude of the resistivity minimum scales linearly with the residual resistivity over 2 orders of magnitude. At moderate temperatures (100-300 K) the resistivity shows a positive, linear temperature dependence due to electron-phonon scattering. Defects affect the electron-phonon scattering as well leading to a variation in the effective Debye temperature and resistivity slope between samples, a significant deviation from Matthiessen's rule. © 2009 The American Physical Society.