AVS 49th International Symposium
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA5
Self-organization of Semimetal Bi on Si(111)

Monday, November 4, 2002, 3:20 pm, Room C-110

Session: Nucleation & Growth of Metals on Oxides & Semiconductors
Presenter: T. Nagao, Tohoku University, Japan
Authors: T. Nagao, Tohoku University, Japan
T. Kogure, University of Tokyo, Japan
J.T. Sadowski, Tohoku University, Japan
T. Sekiguchi, University of Tokyo, Japan
S. Hasegawa, University of Tokyo, Japan
T. Sakurai, Tohoku University, Japan
Correspondent: Click to Email
We have studied the self-organization of epitaxially grown semimetal bismuth on Si(111) surfaces by in situ reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and 4-probe conductivity measurement. On the 7x7 surface, up to around 4ML, the system grows in a S-K like manner: [102] oriented flat-top islands grow after completion of disordered wetting layer. Sharp height distribution of these flat-top islands peaked at 1.2nm was clarified in a wide growth temperature range (290-550 K) as well as wide deposition rate (0.1-2.0 ML/min), which indicates the significance of the electronic effect in the film growth. After the connection of the flat-top islands, the growth mode switches to a nearly perfect FvM growth, and the connected layer self-organizes into a single-crystal ultrathin film with Bi(001)-1x1 surface as evidenced by in situ RHEED and ex situ XTEM. Four-probe measurements showed the largest resistance drop at around 4 ML followed by another gradual drop around 4-10 ML and finally approached to a conductivity only several times lower than the bulk value, unusual value for such thin films. The initial drop was associated with the percolation of the flat-top islands. The following gradual drop was assigned to the reduction in the (surface and bulk) roughness scattering, due to self alignment in the crystal orientation via drastic interfacial glide and mass transport of the flat-top nanocrystals which are initially loosely bound on the disordered wetting layer. The origin of this new type of electronic growth and its self-organization into perfectly ordered ultrathin film will be discussed in detail.