Circular dichroism in radiative and nonradiative inelastic XUV scattering

Accepted: 6 March 1997     

A cadmium photoionization laser pumped by laser induced plasma radiation from a multi foci device

Soft x-rays from a laser-produced plasma were used to perform innershell photoionization of Cd atoms and to generate laser radiation at 442 nm. To achieve longer interaction zones between the Cd vapor and the soft x-ray flux, up to three plasma spots have been applied. In this way a maximum laser energy of 300 J with a 600 mJ Nd:YAG laser for the plasma production was achieved. Experimental investigations and corresponding rate-equation calculations indicate, that photoelectrons play an important role in the total laser kinetics.     

Synthesis and growth mechanism of rough PbTe polycrystalline thermoelectric nanorods

Rough PbTe polycrystalline one-dimensional nanostructure is expected to exhibit improved thermoelectric properties, compared to single-crystal one. In this article, polycrystalline PbTe thermoelectric nanorods with rough surfaces are successfully synthesized with or without surfactants by a simple alkaline reducing chemical route. Microstructural analyses show that these nanorods range from 50 to 200 nm in diameter with lengths up to 1 μm, and are composed of PbTe nanoparticles of about 30–50 nm. The formation mechanism of PbTe nanorods can be reasonably explained by tellurium template-based process from the time-dependent experiments.     

Antiphase domain growth in BCC metallic alloys via vacancies

We study by Monte Carlo simulation the influence of vacancies on the growth of antiphase domains after a quench of a BCC binary alloy. We find a powerlaw regime (R(t)t ^x withx depending on temperature and larger than the Allen-Cahn value 0.5. We have verified the scaling of the structure factor and performed a finite size analysis of the excess energy evolution and vacancy diffusion.     

Energy levels and optical oscillator strengths of inner-shell excited states and photoionizations of the ground and first excited states of C IV ion

Extensive configuration interaction wave functions are determined to calculate the energies of the inner-shell excited states and the oscillator strengths of the optically allowed inner-shell transitions of C IV ion. Photoionization cross-sections of the ground and the first excited states of C IV ion are also obtained by using the R-matrix method. The positions of some inner-shell excited states are redetermined more accurately by analyzing the resonance structures of the photoionization processes. Some of the results are compared with other available theories and experiments. Received 29 September 1999 and Received in final form 8 December 1999     

Photoelectron and photoion spectroscopy on atomic Lu in the region of the 5p excitation

The resonances of atomic Lu have been investigated by photoelectron and photoion spectroscopy using monochromatized synchrotron radiation in the vacuum ultraviolet energy region. The total photoion yield has been compared to calculations in which the extended Fano theory (Mies formalism) and the Hartree-Fock method were applied. The resonance structure is dominated by the spin-orbit splitting of the 5p core hole. In the photoion yield spectra of singly and doubly charged ions a high fraction of Lu²⁺ ions has been found in the region of the 5p ^-1 (² P _1/2 )nd resonances. Photoelectron spectra, recorded in this resonance region, have been investigated with respect to deexcitation channels connected with Lu²⁺ ions. The 5p ^-1 (² P _1/2 )nd resonances predominantly autoionize by spin-flip into states, which decay in the second step into Lu²⁺ final ionic states. Received: 2 September 1998 / Accepted: 17 September 1998     

Observation of triangle pits in PbSe grown by molecular beam epitaxy

PbSe thin films on BaF₂ (1 1 1) were grown by molecular beam epitaxy with different selenium beam flux. Evolution of PbSe surface morphologies with Se/PbSe beam flux ratio (R_f) has been studied by atomic force microscopy and high-resolution X-ray diffraction. Growth spirals with monolayer steps on PbSe surface are obtained using high beam flux ratio, R_f ≥ 0.6. As R_f decreases to 0.3, nano-scale triangle pits are formed on the surface and the surface of PbSe film changes to 3D islands when R_f = 0. Glide of threading dislocations in 〈1 1 0〉{1 0 0}-glide system and Pb-rich atom agglomerations are the formation mechanism of spiral steps and triangle pits. The nano-scale triangle pits formed on PbSe surface may render potential applications in nano technology.     

Nitrogen and Silicon Co-Doping of Ge2Sb2Te5 Thin Films for Improving Phase Change Memory Performance

Electrical properties and phase structures of （Si＋N）-codoped Oe2Sb2Te5 （GST） for phase change memory are investigated to improve the memory performance. Compared to the films with N or Si dopants only in previous reports, the （Si＋N）-doped GST has a remarkable improvement of crystalline resistivity of about 104mΩcm. The Fourier-transform infrared spectroscopy spectrum reveals the Si-N bonds formation in the film. X-ray diffraction patterns show that the grain size is reduced due to the crystallization inhibition of the amorphous GST by SiNx, which results in higher crystalline resistivity. This is very useful to reduce writing current for phase change memory applications.     

Tailoring of nickel silicide contacts on silicon carbide

Co-deposition technique by means of simultaneous ion beam sputtering of nickel and silicon onto SiC was performed for tailoring of Ni-silicide/SiC contacts. The prepared samples were analysed by means of XRD and XPS in order to obtain information about the surface and interface chemistry. Depth profiling was used in order to analyse in-depth information and chemical distribution of the specimens. XRD results showed that the main phase formed is Ni₂Si. The XPS analysis confirmed the formation of the silicide on the surface and showed details about the chemical composition of the layer and layer/substrate interface. Moreover, the XPS depth profiles with detailed analysis of XPS peaks suggested that tailoring of C distribution could be monitored by the co-deposition technique employed.     

Combinatorial fabrication and screening of organic light-emitting device arrays

The combinatorial fabrication and screening of 2-dimensional (2-d) small molecular UV-violet organic light-emitting device (OLED) arrays, 1-d blue-to-red arrays, 1-d intense white OLED libraries, 1-d arrays to study Förster energy transfer in guest-host OLEDs, and 2-d arrays to study exciplex emission from OLEDs is described. The results demonstrate the power of combinatorial approaches for screening OLED materials and configurations, and for studying their basic properties.