Nanowires on stepped metal surfaces

Abstract

The electronic properties of solids can be tailored by structuring them on the nanometer scale. Such a program is becoming reality as surface analysis techniques and sophisticated growth methods are merging. Here, we present results of a venture into one-dimensional nanostructures, grown by decoration of steps at metal surfaces. The growth modes and electronic states are studied using scanning tunneling microscopy (STM) and inverse photoemission. Two-dimensional analogs of Stranski-Krastanov and layer-by-layer growth are found for Cu on stepped Mo(110) and W(110), respectively. Contrast between different metals is achieved in STM pictures by resonant tunneling via surface states and image states, with the latter providing a map of the work function. The limit of single atomic rows decorating step edges is studied by inverse photoemission, and an energy shift of 0.4 eV is found for electronic states of step atoms. Stripe structures are attractive for the study of two- versus one-dimensional magnetism, for magnetoresistive sensors, and in the design of anisotropic materials.