X-ray diffraction study of theSi(111)−3×3−Agsurface structure

The tip role on STM images of Ag/Si(111)√3 × √3

“…A transition from a surface described by the symmetric HCT model at RT to an asymmetric IET model was proposed to occur at LT. The transition temperature is believed below 150 K based on photoemission and x-ray diffraction measurements [10,11]. This result is, however, in contrast with earlier photoemission studies, showing that the valence band spectra are essentially the same down to 70 K [12,13].…”

Ag∕Si(111)3×3: Surface band splitting and the inequivalent triangle model

“…The transition temperature is believed to be somewhat below 150 K based on photoemission and x-ray diffraction measurements. 5,10 The hexagonal appearance of the empty-state STM images and the IET model was supported by a theoretical calculation, 3 which found that the IET model is more favorable, energetically, than the HCT model. As a consequence of the two different Ag trimers in the IET structure, the plane containing the surface normal and the ͓112͔ direction is no longer a mirror plane.…”

“…5 of the split surface bands at the K point was intended as a support of the IET model that has currently been subjected to intensive studies. 5,9,10,[12][13][14] It was concluded that the Ag/ Si͑111͒ ͱ 3 ϫ ͱ 3 surface exhibits a disorder-order phase transition from RT to LT, meaning that S 2 and S 3 are already split at room temperature. Since we find that the spectra do not show any detectable split, we have to conclude that a discussion of an order-disorder transition cannot be based on the photoemission data.…”

STM observation of the Si(111)-c(12*2)-Ag surface

“…For example, the √ 3 × √ 3-Ag surface exhibits an empty-state STM image of a hexagonal-lattice pattern at low temperature but a honeycomb-lattice one at room temperature [11,12]. The transition has now been vigorously argued whether it is an order-disorder type or a displacive type [8,9,20,21]. On the other hand, the 3×1-Ag phase transforms to 6×1 below 500 K and subsequently to c(12×2) below 100 K [10].…”

“…These surfaces have been model systems to develop surface science techniques and almost all the methods have been used to determine their atomic/electronic structures [8][9][10]. The ground state of the Si(111)-√ 3 × √ 3-Ag surface has now been widely accepted to possess a so-called "InEquivalent Triangle (IET)" structure [11,12], while the structure of the Si(111)-3×1-Ag is well described by the "Honeycomb Chain Channel (HCC)" model [13].…”