Nonuniform quantum-confined states and visualization of hidden defects in thin Pb(111) films

Abstract

The spatial distribution of the differential conductance for ultrathin Pb films grown on Si(111)7x7 substrate is studied by means of low-temperature scanning tunneling microscopy and spectroscopy. The formation of the quantum--confined states for conduction electrons and, correspondingly, the appearance of local maxima of the differential tunneling conductance are typical for Pb films; the energy of such states is determined mainly by the local thickness of Pb film. We demonstrate that the magnitude of the tunneling conductivity within atomically flat terraces can be spatially nonuniform and the period of the small-scale modulation coincides with the period of Si(111)7x7 reconstruction. For relatively thick Pb films we observe large-scale inhomogeneities of the tunneling conductance, which reveal itself as a gradual shift of the quantized levels at a value of the order of 50 meV at distances of the order of 100 nm. We believe that such large-scale variations of the tunneling conductance and, respectively, local density of states in Pb films can be related to presence of internal defects of crystalline structure, for instance, local electrical potentials and stresses.

arXiv comment7 pages, 6 figures

References in corpus (2)

• Anisotropic Metal-Insulator Transition in Epitaxial Thin Films
• Tunneling interferometry and measurement of thickness of ultrathin metallic Pb(111) films

Cited by in corpus (4)

• Quantum-well and modified image-potential states in thin Pb(111) films: an estimate for the local work function
• Observation of hidden parts of dislocation loops in thin Pb films by means of scanning tunneling spectroscopy
• Field-Emission Resonances in Thin Metallic Films: Nonexponential Decay of the Tunneling Current as a Function of the Sample-to-Tip Distance
• Oscillatory Bias Dependence of Visible Height of Monatomic Pb(111) Steps: Consequence of Quantum-Size Effect for Thin Metallic Films