Decomposition of N2O on the Si(100)2 × 1 and Si(111)7 × 7 surfaces: Determination of the density of broken bonds

This paper reports on the site-specific decomposition behaviour of N2O onthe clean Si(100)2 × 1 and Si(111)7 × 7 surfaces at room temperature, studied by spectroscopic differential reflectometry (SDR) and Auger electron spectroscopy (AES). It has been established that Si---O bond formation occurs at the toplayer Si atoms, mainly via attachment of the unsaturated broken bonds. In this way it is possible to determine the density of broken (dangling) bonds at the clean Si surface. Our results confirm the high dangling bond density at the 2 × 1 reconstructed Si(100) surface for which we assume a defect density of 15 ± 10%. The density of dangling bonds per 7 × 7 unit cell (49 atoms), 23 ± 4, is in agreement with the established 19 as revealed by current imaging tunneling spectroscopy (CITS)

The adsorption behaviour of O2 on the clean Si(110) surface in the early stage

This Letter reports on the early stage of adsorption of O2 on the clean Si(110) surface, showing a prominent 5×1 reconstruction, in ultrahigh vacuum at 300 K. Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) have been used to monitor this solid-gas reaction. Careful measurements of the normalized oxygen Auger signal in the low exposure region reveal, for the first time, a remarkably fast adsorption of O2 up to 0.15 monolayer of oxygen, the initial sticking probability being about 1. The LEED measurements suggest that those surface sites which constitute the additional higher order reconstructions, are highly reactive

Kinetics of the adsorption of atomic oxygen (N2O) on the Si(001)2x1 surface as revealed by the change in the surface conductance

The adsorption behaviour of N2O on the Si(001)2 × 1 surface at 300 K substrate temperature has been investigated by measuring in situ the surface conductance during the reaction process. For comparison we monitored in the same way the adsorption of O2 on the same surface which ultimately leads to the flat band situation. The adsorption of atomic oxygen as released by decomposition of the N2O molecule, in contrast with molecular oxygen, was found to result in an increase of the band bending. The difference in behaviour of the change of the surface conductance between the two solid-gas reactions can be explained by considering that the adsorption of O2 will also remove deep-lying backbond states in addition to the dangling bond (DB) and dimer bond (DM) related surface states. It is well known that only the DB and DM surface states are affected by N2O. The surface conductance measurements (SCM) presented in this paper complement our previous spectroscopic differential reflectivity measurements and Auger electron spectroscopic results for the system Si(001)2 × 1 + N2O; we have found evidence that the second step of the proposed three-stage adsorption process of atomic oxygen can be divided into two substages. From our SCM data we could derive that the distance between the valence band edge and the Fermi energy of the clean Si(001)2 × 1 surface is 0.32 ± 0.02 eV, which is in agreement with previous photoemission results

Scanning Auger microscopy as applied to the analysis of highly textured YBaCu3Ox thin films

Scanning Auger electron spectroscopy and scanning electron microscopy have been used to investigate the local composition and structure of highly textured axis oriented YBaCuO films with thicknesses in the range 0.4–1 μm. The cuprate films were sputtered on MgO and sapphire (100)-oriented single-crystal substrates at room temperature followed by several anneal stages below or at 920°C in pure oxygen. The YBaCuO/sapphire sample was examined again after an additional 750°C air anneal for 24 h. By applying Auger line profiling on a freshly prepared cross-sectional surface of a thin cuprate film deposited on a sapphire substrate we have been able to show that barium aluminate segregation at grain boundaries is the main cause of the higher electrical resistance usually observed for cuprate films on Al2O3. The (drastic) reduction in Tc can be attributed to the substitution of aluminium in the cuprate at copper sites. Severe interdiffusion has been observed for the epitaxial c axis oriented YBaCu oxide films grown on an MgO substrate, which leads to a deterioration in the superconductivity. The main reason for reduced Tc and quality of cuprate films on MgO is the copper loss into the substrate, the depth of penetration of copper extending more than 400 nm below the YBaCuO---MgO interface. From our experimental results it is evident that Auger line profiling is an important tool in the analysis of high Tc superconducting thin films

The Devil is in YOUR Closet: 48 square feet can change EVERYTHING

Using a real grocery list, cash money, and an unexpected situation, attendees put themselves in the shoes (or socks) of the children-at-risk and families who need support in a hands on, solution centered workshop. Workshop participants walk away with culturally relevant materials that will allow them to find funding for a 6\u27x8\u27 corner of hope--at little or no cash cost. But that makes all the difference in the world

Are there spurious temperature trends in the United States Climate Division database

The United States (U.S.) Climate Division data set is commonly used in applied climatic studies in the United States. The divisional averages are calculated by including all available stations within a division at any given time. The averages are therefore vulnerable to shifts in average station location or elevation over time, which may introduce spurious trends within these data. This paper examines temperature trends within the 15 climate divisions of New England, comparing the NCDC\u27s U.S. Divisional Data to the U.S. Historical Climate Network (USHCN) data. Correlation and multiple regression revealed that shifts in latitude, longitude, and elevation have affected the quality of the NCDC divisional data with respect to the USHCN. As a result, there may be issues with regard to their use in decadal- to century-scale climate change studies

Adsorption of atomic and molecular oxygen on Si(100)2x1: coverage dependence of the Auger O KVV lineshape.

By means of Auger electron spectroscopy (AES) we have monitored the room temperature adsorption of O2 and N2O on the clean Si(0 0 1)2 × 1 surface. We have found, for the first time, a significant variation in the intensity ratio of the K L1 L1 and K L23 L23 O Auger lines in the submonolayer range. This variation can be related to a change in bonding configuration of the oxygen atom/molecule in the initial adsorption stage in which the influence of inter-atomic matrix elements of the Auger process cannot be neglected

Frank's constant in the hexatic phase

Using video-microscopy data of a two-dimensional colloidal system the bond-order correlation function G6 is calculated and used to determine the temperature-dependence of both the orientational correlation length xi6 in the isotropic liquid phase and the Frank constant F_A in the hexatic phase. F_A takes the value 72/pi at the hexatic to isotropic liquid phase transition and diverges at the hexatic to crystal transition as predicted by the KTHNY-theory. This is a quantitative test of the mechanism of breaking the orientational symmetry by disclination unbinding