THE STRUCTURE OF THE SI(100)2X1-H-SURFACE

The SLAB-MINDO method has been employed to determine the structure of the Si(100)2 × 1: H surface. The positions of the adsorbed hydrogen atoms with respect to the nearest neighbour silicon atoms have been calculated, along with the displacements of all the silicon atoms within the first four silicon layers from their ideal bulk positions. The structure is obtained from the minimisation of the total energy for a film of 16 layers. The optimum geometry is found to be that of a symmetric dimer with a Si-Si dimer bond length close to the bulk nearest neighbour distance. This is in contrast to the significantly shorter dimer bond length which has been found to characterise the clean surface. The significant atomic displacements which occur within the deeper layers of the Si(100)2 × 1 topology are found to be only slightly modified by the formation of the monohydride. © 1990.