Step-doubling at Vicinal Ni(111) Surfaces Investigated with a Curved Crystal

Abstract

Vicinal surfaces may undergo structural transformations as a function of temperature or in the presence of adsorbates. Step-doubling, in which monatomic steps pair up forming double-atom high staircases, is the simplest example. Here we investigate the case of Ni(111) using a curved crystal surface, which allows us to explore the occurrence of step-doubling as a function of temperature and vicinal plane (miscut α and step type). We find a striking A-type ({100}-like microfacets) versus B-type ({111}-like) asymmetry towards step-doubling. The terrace-width distribution analysis performed from Scanning Tunneling Microscopy data points to elastic step interactions overcoming entropic effects at very small miscut α in A-type vicinals, as compared to B-type steps. For A-type vicinals, we elaborate the temperature/miscut phase diagram, on which we establish a critical miscut α c = 9.3 • for step-doubling to take place.

Structure and electronic states of vicinal Ag(111) surfaces with densely kinked steps

“…The asymetric broadening of the curves increases dramatically when comparing to the sharplypeaked histograms of panel figure 3(a). This drastic change in the shape of P(d) is common to other metal surfaces [7,8], but only in the present case the smooth histograms of figure 3(c) allow the observation of fine modulations on the right hand tail that can be fitted with a set of Gaussian functions, which suggest the presence of terrace-width fluctuations around preferred (or 'magic') d n values.…”

“…During the last decade, a number of studies have been aimed at systematically exploring vicinal surfaces using crystal samples with both spherical and cylindrical shapes, mostly metals [3][4][5][6][7][8][9], but also semiconductors [10]. Using such samples one can probe entire families of vicinal planes, and hence provide a comprehensive understanding of all physical-chemical properties connected to the presence of surface steps.…”

“…Using such samples one can probe entire families of vicinal planes, and hence provide a comprehensive understanding of all physical-chemical properties connected to the presence of surface steps. In fact, the ability to compare a high-symmetry surface with its vicinal stepped planes on the same sample has been proved essential to clarify controversial issues, such as the quantum-mechanical nature of surface electronic states away from the high-symmetry plane [4,11], or to unveil new general properties, such as structural transitions and fluctuations of the surface as a function of the vicinal angle α [3,4,[7][8][9]. The latter is particularly important, due to its direct connection with the equilibrium shape of three-dimensional nanocrystals, but also attractive from a fundamental point of view, since a vicinal surface can be regarded as a superlattice of steps subject to thermal disorder, equivalent to a one-dimensional (1D) gas of fermions [12][13][14][15].…”

“…In this work we follow the curved surface approach to investigate structural and electronic properties of vicinal Ag(111) surfaces featuring fully-kinked steps. In general, vicinal (111) surfaces of fcc crystals are chosen to exhibit steps with close-packed configuration (oriented along the [1-10] direction), whereas vicinals with fully-kinked steps (oriented along the [1][2][3][4][5][6][7][8][9][10][11][12] direction, and also called 100% kinked [16]) have been very scarcely studied. This is striking, since due to the lower atomic coordination of such kinks these surfaces are particularly attractive to investigate chemical reactions and catalysis [17].…”

Boron nitride monolayer growth on vicinal Ni(1 1 1) surfaces systematically studied with a curved crystal

“…Both techniques reveal the homogeneous wetting of the entire substrate by a single hBN monolayer, which in turn induces a deep structural transformation of the curved Ni substrate underneath. The bare c-Ni(111) surface is characterized by patterns of one- 40 20 distance (nm) 0 -12 and two-atom-high steps [63], but after hBN growth such simple step lattices transform into hill-and-valley structures of hBN-covered (111) terraces alternated with nanofacets oriented along other Ni crystal directions. Early studies of hBN grown on Ni(755) have already suggested substrate faceting [25] and here we confirm that the hBN monolayer growth leads to general faceting at all A-type and B-type vicinal planes.…”