A real space investigation of the dimer defect structure of Si(001)‐(2times8)

Abstract

The atomic arrangement of the Si(001)‐(2 times 8) surface has been directly imaged in real space by scanning tunnelling microscopy. The superstructure is impurity induced and stablilized by as little as 1% Ni. Clean Si(001) surfaces do not form the (2times8) phase. The two‐dimensional Fourier transforms of the STM topographs correspond well to the (2times8) LEED pattern, but the real space images are in fact considerably more complex than previously concluded on the basis of recent diffraction technique measurements. The STM images clearly demonstrate that the (2times8) surface consists of a complex missing dimer structure, namely one and multiple dimer vacancies. Such a dimer defect appears related to the Ni impurity and intimately related to the ordering of the dimer defects probably by third layer dimerization to produce quasi‐ordered ‘channels’. 1988 Blackwell Science Ltd