AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP12
Tunable Lattice Parameter of Ultrathin Bismuth Film

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: J.T. Sadowski, Tohoku University, Japan
Authors: J.T. Sadowski, Tohoku University, Japan
Y. Fujikawa, Tohoku University, Japan
T. Nagao, Tohoku University, Japan
A. Al-Mahboob, Tohoku University, Japan
T. Sakurai, Tohoku University, Japan
Correspondent: Click to Email
The study of the structure and electronic properties of ultra-thin metal films on semiconductor surfaces has always attracted significant attention. To establish better control of the crystalline and electronic properties of the metallic layers, it is necessary to understand the factors governing their epitaxial growth, namely, surface free energies and stress relaxation effects. Semimetal bismuth (Bi) has distinctive electronic properties due to its covalent-like bonds and highly anisotropic Fermi surface. Moreover, results of our electron diffraction and scanning tunneling microscopy (STM) experiments show that Bi undergoes an allotropic transformation as a function of thickness on the scale of several layers, during the RT growth on Si(111)-7x7. After the initial formation of the Bi wetting layer, Bi grows with a new {012}-oriented phase, with a structure different from bulk Bi. With increasing the Bi coverage, above the critical thickness the film transforms into the bulk-like Bi(001) phase. Calculations suggest that the {012} phase with even-number layers is stabilized by forming a puckered-layer structure, which results in the formation of flat and well ordered film, reflecting the 2D structure of the {012} phase. Most interestingly, the lattice parameter of the Bi{012} phase can be tuned to a great extent by changing the nature and strength of the interactions between the Bi film and the substrate. Using the results of systematic diffraction and STM studies combined with the theoretical calculations, we will discuss the atomic structure of the Bi{012} film grown on the various surfaces (clean Si(111), H-Si(111), Bi and Au superstructures on Si(111)).