One-dimensional surface states on a striped Ag thin film with stacking fault arrays

Abstract

One-dimensional (1D) stripe structures with a periodicity of 1.3 nm are formed by the introduction of stacking fault arrays into a Ag thin film. The surface states of such striped Ag thin films are studied using a low-temperature scanning tunneling microscope. Standing waves running along the stripes and characteristic spectral peaks are observed by differential conductance ($dI/dV$) measurements, revealing the presence of 1D states on the surface. Their formation can be attributed to quantum confinement of Ag(111) surface states into a stripe by stacking faults. To quantify the degree of confinement, the effective potential barrier at the stacking fault for Ag(111) surface states is estimated from independent measurements. A single quantum well model with the effective potential barrier can reproduce the main features of $dI/dV$ spectra on stripes, while a Kronig-Penney model fails to do so. Thus the present system should be viewed as decoupled 1D states on individual stripes rather than as anisotropic 2D Bloch states extending over a stripe array. The result is discussed in terms of electron localization into stripes due to strain-induced inhomogeneities and absorption from surface to bulk states.