Si Si Research Articles

LOWER PALEOGENE COMPLEX ANT NESTS FROM ARGENTINA: EVIDENCE FOR EARLY POLYDOMY IN ANTS?

Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales Bernardino Rivadavia; Argentina

Study of the a-Si:H/c-Si Heterointerface by Ex-Situ Spectroscopic Ellipsometry, Infrared Spectroscopy, and Solar Cell Modeling

The interface formation between plasma-enhanced chemical vapor-deposited (PECVD) silicon thin films and H-terminated, p-type c-Si was investigated. The formation of hydrogenated amorphous silicon (a-Si:H), epitaxial Si, and mixed phase Si was detected through spectroscopic ellipsometry (SE) and high-resolution transmission electron mi- croscopy (HRTEM). The evolution of the hydrogen content and hydrogen bonding configurations in the films were monitored by attenuated total reection infrared spectroscopy (FTIR-ATR). The dependence of the hydrogen binding configuration on the film morphology was observed. Even with an observed epitaxial layer in the structure of the intrinsic a-Si:H, a silicon heterojunction (SHJ) solar cell with 9.2% efficiency was obtained, which is the largest-active-area (72 cm^2) SHJ cell on p-type c-Si. The numerical simulation tool AFORS-HET was used to model the layers and interface properties of the cell. The simulation results were consistent with the experimental results, demonstrating the importance of interface defect passivation in SHJ solar cells.

The Influence of a Single Transition Metal Atom on the Reactivity of Main Group Metal Clusters in the Gas Phase

Collision induced dissociation experiments of the metalloid clusters [(CO)5CrGe9R3]– 2 and [(CO)3CrGe9R3]– 3 are presented, showing that 2 can lose Cr(CO)5 or CO to give [Ge9R3]– 1 or 3, respectively. Further dissociation from 3 leads first of all to the metalloid cluster [CrGe9R3]– 4, from which different elimination routes start. Thereby significant differences with respect to the chromium free cluster [Ge9R3]– 1 are observed, where beside C–H also Si–C and Si–Si bond dissociation at low threshold energy take place, showing that 4, with its additional chromium atom, is an ideal model system for a single atom catalyst.

Mineralogical composition and functionality of clays used for pottery education by physically challenged learners at the Ikwezi-Lokusa Educational Centre, Eastern Cape, South Africa

Clays used for pottery education to physically challenged learners were mineralogically analysed to appraise their suitability both for usage in making pottery products and convenience for the learners. The suitability is alluded to the fact that the clays have undergone basic beneficiation which include grinding, removal of unwanted materials through sieving, prior to their usage. The clays were mineralogically characterised using Munsell Soil Color Chart, X-ray powder diffractometry (XRPD) and optical microscopy. Results revealed that the color of the samples were light yellow brown to white. Mineral phases identified by XRPD depicted both quartz (SiO 2 ) and kaolinite as the dominant minerals in the samples with traces of smectite ((Na,Ca)(Al,Mg) 6 (Si 4 O 10 ) 3 (OH) 6-n (H 2 O)), mica (AB 2-3 (Al,Si)Si 3 O 10 )(F,OH) 2 ) and feldspar (Na/K(AlSi 3 O 8 )). Optical morphology tests depicted quartz particles were generally coarse; and angular to very angular in morphology. Due to the beneficiation process the quartz particles were reduced making the clays easy to handle during both creation and firing stages of the pottery making. The mineralogical composition of the clays influenced their functionality as raw materials for pottery. Keywords: Clay processing, color, disability, kaolinite, quartz, X-ray powder diffraction.

Complexation of Si—Si σ Bonds to Metals

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hexa‐tert‐butylcyclotrisilane, a Strained Molecule with Unusually Long SiSi and SiC Bonds

Hexa‐<i>tert</i>‐butylcyclotrisilane, a Strained Molecule with Unusually Long SiSi and SiC Bonds

X-ray diffraction study of the effect of hydrogen atoms on the Si–Si atomic short-range order in amorphous silicon

Evaporated a-Si and glow discharge a-Si–H samples are studied by X-ray diffraction and the radial distribution functions are calculated. Special attention is given to the Fourier transform procedure in order to avoid non-physical features in the critical interval between 4 and 6 A. An important growth of a pair distance peak at 4.9 A is observed for the hydrogenated material. This peak which corresponds to a 35° to 45° dihedral angle is attributed to the formation of seven membered Si rings or larger ones in the Si–H bond vicinity. The Si–Si first neighbour peak has an asymetrical shape likely due to the inhomogeneity of the material. The coordination number is found to be 3.5 instead of 4 for pure a-Si. From this value a 33% H content is derived for the g.d. a-Si–H sample which is deposited on a substrate hold at 25°C. Une etude comparative par diffraction X a ete effectuee sur un echantillon de Si amorphe evapore et un echantillon hydrogene prepare par „glow discharge” sur un support maintenu a 25°C. On a apporte un soin particulier au processus de la transformee de Fourier pour eviter que des oscillations parasites ne viennent perturber l'information dans l'intervalle crucial entre 4 et 6 A. On observe une croissance importante d'un pic a 4,9 A sur la courbe relative a Si–H. Ce pic, correspondant a un angle diedral situe entre 35° et 45°, s'explique par la formation d'anneaux de 7 atomes ou plus dans le voisinage immediat des liaisons Si–H. Le pic des premiers voisins Si–Si a une forme asymetrique, preuve d'une inhomogeneite dans la distribution de ces atomes. La coordinence mesuree est de 3,5 au lieu de 4 pour Si pur d–ou l'on deduit une concentration de 33% d'hydrogene.