Pulsed growth and electronic structure of layered CuFe films on Cu(100)

The authors have attempted the preparation of CuFe superlattice structures by pulsed metal deposition in an atomic layer-by-layer fashion upon a Cu(100) substrate at 300 K. The electronic structure of a single crystal 6*(1 ML Fe:1 ML Cu)(100)CuFe film has been probed by angle-resolved ultraviolet photoemission spectroscopy. Experimental photoemission results have been critically compared with both fully self-consistent linear muffin-tin orbital (LMTO) predictions of the ground state electronic structure and with photocurrent calculations using time reversed LEED formalism. Theoretical predictions indicate the expected large rearrangements in the valence electron states which are shown to be large enough in certain E(k) points to provide a definite 'fingerprint' of superlattice formation. Despite LEED/AES measurements which indicate a high quality p(1*1) single crystal film exhibiting strong compositional modulation they show by comparing experimental and theoretical angle-resolved photoemission spectra that the attempted Brillouin zone folding in the growth direction has not been imposed. Their result suggests that formation of metallic superlattice with short repeat periods (2 ML) is a nontrivial task despite the apparent ideality of the CuFe system for this purpose. Results presented here are supportive of nonideality in the growth mechanism of Fe/Cu(100).