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Generation of anionic and cationic iron-dioxygen adducts (FeO2) in the gas phase involves chemical ionization of a mixture of Fe(CO)5 and O2. Neutralization reionization mass spectrometry helps generate neutral FeO2 molecules from the cation or anion. Mass spectrometric techniques help characterize all these adducts. (FeO2)+ exhibits isomerism and the isomers are side-on and end-on complexes. Ab initio calculation help analyze the interconversion and energetics of both isomers, and the side-on complex exhibits higher stability than the end-on complex.

The top‐seeded solution growth for rutile GeO2 single crystals using alkali carbonates or fluorides as flux is applied. Structural data of obtained single crystals confirm the rutile phase with a = b = 4.3966 Å and c = 2.8612 Å. The crystals with diameter of 5–15 mm are either undoped or intentionally doped with Sb5+, Sn4+, Al3+, Ga3+, and F− ions. It is found that Sb5+ is a very efficient n‐type donor enabling free electron concentration even above 1020 cm−3; thus, Sb‐doped GeO2 is a potential substrate for vertical power devices. In contrast, crystals doped with Al and Ga do not show p‐type conductivity suggested by the theory. The onset of the absorption occurs at 5.0 and 5.5 eV perpendicular and parallel to the c‐axis, respectively. Rutile GeO2 shows a very intense photoluminescence peaking at 420 nm (blue) and 520 nm (green). Raman spectra show narrow lines, in particular at high phonon energy (B1g, 170 cm−1). Prepared wafers show FWHM values of rocking curves below 30 arcsec and polishing is achieved down to RMS roughness of 0.15 nm. Transmission electron microscopy images do not show point or extended structural defects with uniform Sb distribution. [ABSTRACT FROM AUTHOR]

The application of collisional activation mass spectrometry (MS) on the (Fe,C,H4,O)+ potential energy surface readily identified the presence of CH4.FeO+, CH3-Fe-OH+, CH3O(H)Fe+ and CH2=Fe-OH2+ isomers in the gas phase. The four isomers were prepared from different ion/molecule gas phase reactions. In addition, attempts to prepare the insertion products H3CO-Fe-H+ and H-Fe-CH2OH+ failed possibly due to the complex potential energy surfaces involved in their formation. Moreover, the results from the ab initio molecular orbital calculations of the four isomers using MP2/ECP-DZ level of theory correlated with the MS analysis.

The quasi-static anisotropic permittivity parameters of electrically insulating beta gallium oxide (β-Ga2O3) were determined by terahertz spectroscopy. Polarization-resolved frequency domain spectroscopy in the spectral range from 200 GHz to 1 THz was carried out on bulk crystals along different orientations. Principal directions for permittivity were determined along crystallographic axes c and b and reciprocal lattice direction a * . No significant frequency dispersion in the real part of dielectric permittivity was observed in the measured spectral range. Our results are in excellent agreement with recent radio frequency capacitance measurements as well as with extrapolations from recent infrared measurements of phonon mode and high-frequency contributions and close the knowledge gap for these parameters in the terahertz spectral range. Our results are important for applications of β-Ga2O3 in high-frequency electronic devices. [ABSTRACT FROM AUTHOR]

Truly bulk ZnGa2O4 single crystals were obtained directly from the melt. High melting point of 1900 ± 20 °C and highly incongruent evaporation of the Zn- and Ga-containing species impose restrictions on growth conditions. The obtained crystals are characterized by a stoichiometric or near-stoichiometric composition with a normal spinel structure at room temperature and by a narrow full width at half maximum of the rocking curve of the 400 peak of (100)-oriented samples of 23 arcsec. ZnGa2O4 is a single crystalline spinel phase with the Ga/Zn atomic ratio up to about 2.17. Melt-grown ZnGa2O4 single crystals are thermally stable up to 1100 and 700 °C when subjected to annealing for 10 h in oxidizing and reducing atmospheres, respectively. The obtained ZnGa2O4 single crystals were either electrical insulators or n-type semiconductors/degenerate semiconductors depending on growth conditions and starting material composition. The as-grown semiconducting crystals had the resistivity, free electron concentration, and maximum Hall mobility of 0.002–0.1 Ωcm, 3 × 1018–9 × 1019 cm−3, and 107 cm2 V−1 s−1, respectively. The semiconducting crystals could be switched into the electrically insulating state by annealing in the presence of oxygen at temperatures ≥700 °C for at least several hours. The optical absorption edge is steep and originates at 275 nm, followed by full transparency in the visible and near infrared spectral regions. The optical bandgap gathered from the absorption coefficient is direct with a value of about 4.6 eV, close to that of β-Ga2O3. Additionally, with a lattice constant of a = 8.3336 Å, ZnGa2O4 may serve as a good lattice-matched substrate for magnetic Fe-based spinel films. [ABSTRACT FROM AUTHOR]

A Sn-doped (100) \beta -Ga2O3 epitaxial layer was grown via metal–organic vapor phase epitaxy onto a single-crystal, Mg-doped semi-insulating (100) \beta -Ga2O3 substrate. Ga2O3-based metal–oxide–semiconductor field-effect transistors with a 2- \mu \textm gate length ( LG) , 3.4- \mu \textm source–drain spacing ( L\textrm {SD}) , and 0.6- \mu \textm gate–drain spacing ( L\textrm {GD}) were fabricated and characterized. Devices were observed to hold a gate-to-drain voltage of 230 V in the OFF-state. The gate-to-drain electric field corresponds to 3.8 MV/cm, which is the highest reported for any transistor and surpassing bulk GaN and SiC theoretical limits. Further performance projections are made based on layout, process, and material optimizations to be considered in future iterations. [ABSTRACT FROM PUBLISHER]

The compounds, ([SnSe]1.15)1(VSe2)nwith n= 1, 2, 3,and 4, were prepared using designed precursors in order to investigatethe influence of the thickness of the VSe2constituenton the charge density wave transition. The structure of each of thecompounds was determined using X-ray diffraction and scanning transmissionelectron microscopy. The charge density wave transition observed inthe resistivity of ([SnSe]1.15)1(VSe2)1was confirmed. The electrical properties of the n= 2 and 3 compounds are distinctly different. The magnitudeof the resistivity change at the transition temperature is dramaticallylowered and the temperature of the resistivity minimum systematicallyincreases from 118 K (n= 1) to 172 K (n= 3). For n= 1, this temperature correlates withthe onset of the charge density wave transition. The Hall-coefficientchanges sign when nis greater than 1, and the temperaturedependence of the Hall coefficient of the n= 2 and3 compounds is very similar to the bulk, slowly decreasing as thetemperature is decreased, while for the n= 1 compoundthe Hall coefficient increases dramatically starting at the onsetof the charge density wave. The transport properties suggest an abruptchange in electronic properties on increasing the thickness of theVSe2layer beyond a single layer. [ABSTRACT FROM AUTHOR]