Abstract:Helium atom scattering has been used to investigate the structure of the Si͑111͒ surface in the temperature range from 900 to 1600 K. Even below the well-known ͑7ϫ7͒ to ''͑1ϫ1͒'' transition the adatoms become mobile, and, when the transition is reached near 1140 K, the specular-and integral-order diffraction peaks have sudden intensity changes, some up and others down, while the seventh-order peaks disappear. Above the transition the adatoms remain, moving rapidly on, and supported by, the ordered but relaxed,… Show more
“…A quantitative analysis of the elastic intensities shown in figure 18 has been performed by Farías et al (1997c). An important result of this study was that the asymmetry reversal observed along [112] for T > T c actually reflects the occurrence of a similar reversal in the structure of the surface, which cannot be reproduced by a simple reduction of the top bilayer spacing as previously suggested (Lange et al 1997).…”
Section: Order-order Transitionsmentioning
confidence: 72%
“…These experiments include studies of the phase transitions on the Ge(111) surface at 550 K (Ha and Greene 1989b), on the Ge(100) surface above 600 K (Meli and Greene 1994), as well as on the (111) and (100) surfaces of Si near 1000 K (Ha and Greene 1989a). The transitions observed on Ge(111) and Si(111) above 1000 K have been re-investigated in collaboration with the Toennies group using high-resolution HAS (Meli et al 1995, Lange et al 1997. In what follows we will describe in some detail the results reported for the order-order transition on Ge(111) near 1050 K (Meli et al 1995).…”
Atomic beam techniques are presently being used in many branches of surface physics such as studies of the particle-surface physisorption potential, surface structure, surface phonons, nucleation and growth on metal and insulator surfaces, surface diffusion and accommodation and sticking of molecules. This review concentrates on diffractive phenomena from surfaces, which up to now were investigated mainly with helium. The theoretical background for diffraction calculations is outlined and representative examples of different applications are given. The main subjects covered are: structural determinations of chemisorbed and physisorbed systems, investigations of disordered surfaces, selective adsorption resonances, diffusion and nucleation studies and investigations of growth and phase transitions on surfaces. Diffraction results obtained with Ne, Ar, H 2 and D 2 are also summarized.
“…A quantitative analysis of the elastic intensities shown in figure 18 has been performed by Farías et al (1997c). An important result of this study was that the asymmetry reversal observed along [112] for T > T c actually reflects the occurrence of a similar reversal in the structure of the surface, which cannot be reproduced by a simple reduction of the top bilayer spacing as previously suggested (Lange et al 1997).…”
Section: Order-order Transitionsmentioning
confidence: 72%
“…These experiments include studies of the phase transitions on the Ge(111) surface at 550 K (Ha and Greene 1989b), on the Ge(100) surface above 600 K (Meli and Greene 1994), as well as on the (111) and (100) surfaces of Si near 1000 K (Ha and Greene 1989a). The transitions observed on Ge(111) and Si(111) above 1000 K have been re-investigated in collaboration with the Toennies group using high-resolution HAS (Meli et al 1995, Lange et al 1997. In what follows we will describe in some detail the results reported for the order-order transition on Ge(111) near 1050 K (Meli et al 1995).…”
Atomic beam techniques are presently being used in many branches of surface physics such as studies of the particle-surface physisorption potential, surface structure, surface phonons, nucleation and growth on metal and insulator surfaces, surface diffusion and accommodation and sticking of molecules. This review concentrates on diffractive phenomena from surfaces, which up to now were investigated mainly with helium. The theoretical background for diffraction calculations is outlined and representative examples of different applications are given. The main subjects covered are: structural determinations of chemisorbed and physisorbed systems, investigations of disordered surfaces, selective adsorption resonances, diffusion and nucleation studies and investigations of growth and phase transitions on surfaces. Diffraction results obtained with Ne, Ar, H 2 and D 2 are also summarized.
“…Thus, the surface disorder caused by a certain amount of defects makes it difficult to determine the surface termination only by atomically-resolved STM observations. Note that the maximum annealing temperature in this study is restricted up to ~1030 °C since the temperature of the underlying Si(111) substrate nearly reaches its melting point of ~1200 °C 19 – 21 , although further increasing annealing temperature may decrease the defect density and improve the surface quality. Figure 4 ( a ) Atomically-resolved STM image of the SmB 6 (001) surface annealed at 1030 °C.…”
Structural and electronic properties of the SmB6(001) single-crystal surface prepared by Ar+ ion sputtering and controlled annealing are investigated by scanning tunneling microscopy. In contrast to the cases of cleaved surfaces, we observe a single phase surface with a non-reconstructed p(1 × 1) lattice on the entire surface at an optimized annealing temperature. The surface is identified as Sm-terminated on the basis of spectroscopic measurements. On a structurally uniform surface, the emergence of the in-gap state, a robust surface state against structural variation, is further confirmed inside a Kondo hybridization gap at 4.4 K by temperature and atomically-resolved spatial dependences of the differential conductance spectrum near the Fermi energy.
“…Incomplete melting of the first two layers has been observed in Si(001) by photoelectron diffraction [7], later discussed also by other authors (see, for example, [8,10,13]) using different techniques, above about 1400 K. Metallization of the Si(001) surface was observed to occur at much lower temperatures between 900 and 1200 K [12,13]. The Si(111) surface behaves differently; in fact, it shows a transition between the 7 Â 7 and 1 Â 1 reconstruction completed around 1140 K. At higher temperatures, the top bilayer was found to become disordered [9,14,15] around 1470 K. Moreover, recent ex situ atomic force microscopy images of Si(111) surfaces [16] showed structures assigned to ''premelting'' of about 3 bilayers (about 9 A ˚) around 1500 K.…”
An original approach for measuring the depth profile of melting and metallization of the Si(111) and Si(001) surfaces is proposed and applied. The different probing depths of the Auger electron and electron energy loss (EELS) spectroscopies are exploited to study the number of molten and metallic layers within 5-30 Å from the surface up to about 1650 K. Melting is limited to 3 atomic layers in Si(001) in the range 1400-1650 K while the number of molten layers grows much faster (5 layers at about 1500 K) in Si(111) as also indicated by the L(3)-edge shift observed by EELS. The relationship between melting and metallization is briefly discussed.
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