In-plane strain-free stanene on a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Pd</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>Sn</mml:mi><mml:mrow><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math> surface alloy
Junji Yuhara, Tsuyoshi Ogikubo, Masaaki Araidai, Sho‐ichi Takakura, Masashi Nakatake, G. Le Lay
Abstract
Here we report the growth of laterally strain-free stanene, that is a two-dimensional (2D) honeycomb structure of tin atoms, on a Pd(111) crystal terminated by a ${\mathrm{Pd}}_{2}\mathrm{Sn}$ surface alloy. The atomic geometry and the electronic structure have been thoroughly investigated by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), Auger electron spectroscopy, high-resolution synchrotron radiation photoemission spectroscopy, and advanced first principles calculations. The STM images clearly reveal the epitaxial growth of honeycomb stanene on the preformed ${\mathrm{Pd}}_{2}\mathrm{Sn}$ surface alloy. LEED patterns clearly show commensurate (\ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}3)R30\ifmmode^\circ\else\textdegree\fi{} spots, corresponding to a lattice constant of 0.47 nm, in perfect accord with the cell size of free-standing stanene. The measured very low buckling, within 20 pm, is derived from section profiles of atomic-scale STM images. This contrasts the significantly larger buckling of free-standing stanene, possibly due to a STM tip effect as well as a non-negligible interaction with the underlying surface alloy. The electronic structure exhibits a characteristic 2D band with parabolic dispersion, which is in good accordance with electronic structure calculations in density functional theory.