Three-dimensional Strain Relaxation in the As/Si (001)-(2 × 1) Surface(Surfaces, Interfaces, and Films)

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Surface X-ray diffraction experiments and elastic-energy calculations have been performed to determine strain relaxation in the As/Si (001)-(2 × 1) surface. The result of the in-plane analysis shows that symmetric As dimers formed on the Si(001) substrate have a bond length of 2.54Å, while the inward displacement of second-layer Si atoms is 0.19Å in an irreducible (2 × 1) unit cell. From the subsequent out-of-plane analysis, we confirmed that the Si atoms in the third and fourth substrate layers are displaced upward (x = 0.75) and downward (x = 0.25) alternately. The observation is supported by an elastic-energy calculation using the Keating model. The determined structure includes in-plane and out-of-plane substrate Si atoms up to the sixth layer. A preliminary measurement of a fractional-order reflection intensity as a function of temperature has shown that the As/Si(001)-(2 × 1) surface becomes more ordered in the temperature range of 710 to 817 K. The intensity rapidly decreases above 817K, which is interpreted to be due to the desorption of As_2 molecules from the surface with an activation energy of 5.9 ± 1.1 eV.
社団法人応用物理学会の論文
2002-01-15