Detailed Synchrotron Radiation Research Articles

Synchrotron radiation study of metallic titanium deposited on dielectric substrates

In this work, the authors present a detailed synchrotron radiation photoemission study of the interactions of metallic titanium with dielectric substrates. In particular, the authors focus on the formation of titanium silicide upon deposition when titanium interacts with SiO2 based substrates. Both TiSi and TiSi2 are present, but TiSi2 grows preferentially upon annealing. When deposited on carbon-containing low-k materials, titanium interacts with the surface to form titanium carbide and titanium silicide. At elevated temperature, carbon in the low-k dielectric assists in the conversion of titanium silicide to titanium silicate.

Origin of p-type conductivity of Sb-doped ZnO nanorods and the local structure around Sb ions

To probe the origin of p-type conductivity in Sb-doped ZnO, a careful and detailed synchrotron radiation study was performed. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy investigations provided the evidence for the formation of the complex defects comprising substitution Sb ions at Zn sites (SbZn) and Zn vacancies within the Sb-doped ZnO lattice. Such complex defects result in the increases of Sb-O coordination number and the Sb valence and thereby lead to the p-type conductivity of Sb-doped ZnO. The back-gate field-effect-transistors based on single nanorod of Sb-doped ZnO were constructed, and the stable p-type conduction behavior was confirmed.

Jet simulations and gamma-ray burst afterglow jet breaks

The conventional derivation of the gamma-ray burst afterglow jet break time uses only the blast wave fluid Lorentz factor and therefore leads to an achromatic break. We show that in general gamma-ray burst afterglow jet breaks are chromatic across the self-absorption break. Depending on circumstances, the radio jet break may be postponed significantly. Using high-accuracy adaptive mesh fluid simulations in one dimension, coupled to a detailed synchrotron radiation code, we demonstrate that this is true even for the standard fireball model and hard-edged jets. We confirm these effects with a simulation in two dimensions. The frequency dependence of the jet break is a result of the angle dependence of the emission, the changing optical depth in the self-absorbed regime and the shape of the synchrotron spectrum in general. In the optically thin case the conventional analysis systematically overestimates the jet break time, leading to inferred opening angles that are underestimated by a factor 1.32 and explosion energies that are underestimated by a factor 1.73, for explosions in a homogeneous environment.

Perturbation of Ge(1 1 1) and Si(1 1 1)√3α-Sn surfaces by adsorption of dopants

We test the response of the √3 × √3α reconstructions formed by 1/3 monolayer of tin adatoms on silicon and germanium (1 1 1) surfaces upon doping with electrons or holes, using potassium or iodine as probes/perturbers of the initial electronic structures. From detailed synchrotron radiation photoelectron spectroscopy studies we show that doping with either electrons or holes plays a complimentary role on the Si and Ge surfaces and, especially, leads to complete conversion of the Sn 4d two-component spectra into single line shapes. We find that the low binding energy component of the Sn core level for both Si and Ge surfaces corresponds to Sn adatoms with higher electronic charge, than the Sn adatoms that contribute to the core level high binding energy signal. This could be analyzed as Sn adatoms with different valence state.

Reaction and growth of Yb/Hg1−xCdxTe(110) interfaces

Detailed synchrotron radiation photoemission studies of Yb/Hg1−xCdxTe junctions as a function of Yb coverage were performed at room temperature. Photoemission from physisorbed xenon after cooling the sample to 35 K was also used to examine the local overlayer work function and the development of interface morphology. For Yb coverages less than 6 Å, the data provide evidence for the lateral growth of islands consisting of Yb-Te reaction products involving divalent Yb, and an associated Hg depletion within an 18-Å-thick near-surface layer. Upon island coalescence at an Yb coverage of 6 Å, the formation of a metallic Yb-rich layer at the surface is observed. This layer traps Hg atoms diffusing across the interface through the formation of an Yb-Hg alloy, and is responsible for the nonmonotonic behavior of the Hg interface concentration as a function of Yb coverage.

Chemical reaction at the Ge(111)-Ag and Si(111)-Ag interfaces for small Ag coverages

We present a detailed synchrotron radiation photoemission study of the elemental semiconductor-Ag interfaces for very small coverages (up to 2.5 monolayers). Our results provide the first evidence of a chemical reaction and intermixing between Ag and the (IV) semiconductors at room temperature.

Chemical reaction at the Ge(111)-Ag and Si(111)-Ag interfaces for small Ag coverages

We present a detailed synchrotron radiation photoemission study of the elemental semiconductor-Ag interfaces for very small coverages (up to 2.5 monolayers). Our results provide the first evidence of a chemical reaction and intermixing between Ag and the (IV) semiconductors at room temperature.