Abstract
The surface structure of Bi(111) was investigated by low-energy electron diffraction (LEED) intensity analysis for temperatures between 140 and $313\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and by first-principles calculations. The diffraction pattern reveals a $(1\ifmmode\times\else\texttimes\fi{}1)$ surface structure and LEED intensity versus energy simulations confirm that the crystal is terminated with a Bi bilayer. Excellent agreement is obtained between the calculated and measured diffraction intensities in the whole temperature range. The first interlayer spacing shows no significant relaxation at any temperature while the second interlayer spacing expands slightly. The Debye temperatures deduced from the optimized atomic vibrational amplitudes for the two topmost layers are found to be significantly lower than in the bulk. The experimental results for the relaxations agree well with those of our first-principles calculation.
Highlights
Bismuth is a semimetal with a very small overlap between valence and conduction band
The surface structure of Bi111͒ was investigated by low-energy electron diffractionLEEDintensity analysis for temperatures between 140 and 313 K and by first-principles calculations
The diffraction pattern reveals a1 ϫ 1͒ surface structure and LEED intensity versus energy simulations confirm that the crystal is terminated with a Bi bilayer
Summary
Bismuth is a semimetal with a very small overlap between valence and conduction band. In bulk Bi, each atom has three equidistant nearest-neighbor atoms and three equidistant next-nearest neighbors slightly further away. This results in puckered bilayers of atoms perpendicular to the111͔ direction in which each atom is covalently bonded to its three nearest neighbors. The atoms’ next-nearest neighbors are in the adjacent bilayers and the bonding within each bilayer is much stronger than the interbilayer bonding. This explains why Bi crystals cleave along the111͒ plane. The A7 structure has two atoms per bulk unit cell, corresponding to the two atoms in the bilayers
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