873 research outputs found
Radiation hard design of HfO2 based 1T1R cells and memory arrays
No full textIn this work the electrical performance of a Rad-Hard designed 1T-1R device based on the combination of an Enclosed Layout Transistor (ELT) and a TiN/HfO2/Ti/TiN based resistor is presented for the first time. Moreover, an architectural solution for 1Mbit radiation hard RRAM array implementation is proposed
NMR-Spektroskopie an den intermetallischen Verbindugen BaAl und Ba mit = Al, Ga und In
No full textDue to the varying properties of intermetallic Compounds, these are used in many different areas. In spite of that, most of the production processes are solely experience-based [1]. To allow the creation of materials with well-defined properties, it is necessary to gain more insight into the chemical bonding and the relationship between structure, bonding and properties. This study discusses the investigation of local atomic order in Ba21Al40 and solid solutions of BaM4 with M = Al, Ga and In because material properties often depend strongly on defects and their concentration. The combination of diffraction, quantum mechanical (QM) calculations and NMR-spectroscopy has proven to be very effective for the investigation of intermetallic compounds [2,3]. Superlattice structure models for different local atomic arrangements can be created based on the crystal structure from diffraction experiments. Subsequently NMR-coupling parameters can be determined via QM-calculations and compared to experimental coupling parameters. This allows the verification, falsification or refinement of the used models.This method was used to detect that the triel-elements preferably occupy different crystallographic sites in the solid solutions Ba(Al1 xGax)4, Ba(Ga1 xInx)4 und Ba(Al1-xInx)4. The Ga-atoms favour the five-bonded (5b) position and In-atoms the (4b) position in the BaAl4-structuretype. The Al-atoms preferably occupy the other site. The NMR-Signals show that, the substitution’s influence is quite strong on the charge distribution of the neighbouring Atoms. The extraction of relevant NMR parameters from experimental data was performed with the Matlab-program Simgui, which can simulate NMR-spectra for various measurement methods and Isotopes simultaneously. Results from QM-calculations can be incorporated into the analysis of experimental NMR-data. These capabilities allow Simgui to be a simple and powerful interface between QM-calculations and NMR-spectroscopy, which might assist in future investigation of intermetallic compounds.[1] R. Nesper,. Angewandte Chemie, 103, 805-834 (1991). [2] O. Pecher, B. Mausolf, V. Peters, K. Lamberts, A. Korthaus, F. Haarmann, Chem. Eur. J., 22(49), 17833-17842 (2016). [3] O. Pecher, B. Mausolf, K. Lamberts, D. Oligschläger, U. Englert, F. Haarmann, Chem. Eur. J., 21(40), 13971-13982 (2015)
Ternary rhombohedral Laves phases RE2Rh3Ga (RE = Y, La-Nd, Sm, Gd-Er)
No full textAbstract:
The ordered Laves phases RE
2Rh3Ga (RE=Y, La–Nd, Sm, Gd–Er) were synthesized by arc-melting of the elements and subsequent annealing. The samples were characterized by powder X-ray diffraction (XRD). They crystallize with the rhombohedral Mg2Ni3Si type structure, space group R3̅m. Three structures were refined from single crystal X-ray diffractometer data: a=557.1(1), c=1183.1(2), wR2=0.0591, 159 F
2 values, 10 variables for Y2Rh3Ga, a=562.5(2), c=1194.4(2) pm, wR2=0.0519, 206 F
2 values, 11 variables for Ce2Rh3Ga and a=556.7(2), c=1184.1(3) pm, wR2=0.0396, 176 F
2 values, 11 variables for Tb2Rh3Ga. The Rh3Ga tetrahedra are condensed via common corners and the large cavities left by the network are filled by the rare earth atoms. The RE
2Rh3Ga Laves phases crystallize with a translationengleiche subgroup of the cubic RERh2 Laves phases with MgCu2 type. Magnetic susceptibility measurements reveal Pauli paramagnetism for Y2Rh3Ga and La2Rh3Ga. Ce2Rh3Ga shows intermediate cerium valence while all other RE
2Rh3Ga phases are Curie–Weiss paramagnets which order magnetically at low temperatures. The 89Y and 71Ga solid state nuclear magnetic resonance (NMR) spectra of the diamagnetic representative Y2Rh3Ga show well-defined single resonances in agreement with an ordered bulk phase. In comparison to the binary Laves phase YRh2 a strongly increased 89Y resonance frequency is observed owing to a higher s-electron spin density at the 89Y nuclei as proven by density of states (DOS) calculations.</jats:p
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