Search results for "Molecular beam"

High quality epitaxial Mn 2 Au (001) thin films grown by molecular beam epitaxy

2020

The recently discovered phenomenon of Neel spin–orbit torque in antiferromagnetic Mn2Au [Bodnar et al., Nat. Commun. 9, 348 (2018); Meinert et al., Phys. Rev. Appl. 9, 064040 (2018); Bodnar et al., Phys. Rev. B 99, 140409(R) (2019)] has generated huge interest in this material for spintronics applications. In this paper, we report the preparation and characterization of high quality Mn2Au thin films by molecular beam epitaxy and compare them with magnetron sputtered samples. The films were characterized for their structural and morphological properties using reflective high-energy electron diffraction, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and temperature dependen…

Radial composition of single InGaN nanowires: a combined study by EDX, Raman spectroscopy, and X-ray diffraction

2013

Optical properties of InN nanocolumns: Electron accumulation at InN non‐polar surfaces and dependence on the growth conditions

2009

InN nanocolumns grown by plasma-assisted molecular beam epitaxy have been studied by photoluminescence (PL) and photoluminescence excitation (PLE). The PL peak energy was red-shifted with respect to the PLE onset and both energies were higher than the low temperature band-gap reported for InN. PL and PLE experiments for different excitation and detection energies indicated that the PL peaks were homogeneously broadened. This overall phenomenology has been attributed to the effects of an electron accumulation layer present atthe non-polar surfaces of the InN nanocolumns. Variations in the growth conditions modify the edge of the PLE spectra and the PL peak energies evidencing that the densit…

Polarity conversion of GaN nanowires grown by plasma-assisted molecular beam epitaxy

2019

International audience; It is demonstrated that the N-polarity of GaN nanowires (NWs) spontaneously nucleated on Si (111) by molecular beam epitaxy can be reversed by intercalation of an Al-or Ga-oxynitride thin layer. The polarity change has been assessed by a combination of chemical etching, Kelvin probe force microscopy, cathodo-and photoluminescence spectroscopy and transmission electron microscopy experiments. Cathodoluminescence of the Ga-polar NW section exhibits a higher intensity in the band edge region, consistent with a reduced incorporation of chemical impurities. The polarity reversal method we propose opens the path to the integration of optimized metal-polar NW devices on any…

Nucleation of GaN nanowires grown by plasma-assisted molecular beam epitaxy: The effect of temperature

2011

Abstract The growth of GaN nanowires by means of plasma assisted molecular beam epitaxy directly on Si(1 1 1) has been investigated as a function of temperature. Statistical analysis of scanning electron microscopy pictures taken for different growth temperatures has revealed that density, diameter, length and length dispersion of nanowires were strongly dependent on temperature. Length dispersion, in particular, was found to be significant at high temperature. These features have been assigned to the different duration of the nucleation process with temperature, namely to the dependence with temperature of the time necessary for the size increase of the three-dimensional precursors up to a…

ZnMgO-based UV photodiodes: a comparison of films grown by spray pyrolysis and MBE

2016

Detecting the UV part of the spectrum is fundamental for a wide range of applications where ZnMgO has the potential to play a central role. The shortest achievable wavelength is a function of the Mg content in the films, which in turn is dependent on the growth technique. Moreover, increasing Mg contents lead to an electrical compensation of the films, which directly affects the responsivity of the photodetectors. In addition, the metal-semiconductor interface and the presence of grain boundaries have a direct impact on the responsivity through different gain mechanisms. In this work, we review the development of ZnMgO UV Schottky photodiodes using molecular beam epitaxy and spray pyrolysis…

Direct observation of elemental segregation in InGaN nanowires by X-ray nanoprobe

2011

Using synchrotron radiation nanoprobe, this work reports on the elemental distribution in single Inx Ga1–xN nanowires (NWs) grown by molecular beam epitaxy directly on Si(111) substrates. Single NWs dispersed on Al covered sapphire were characterized by nano-X-ray fluorescence, Raman scattering and photoluminescence spectroscopy. Both Ga and In maps reveal an inhomogeneous axial distribution inside sin- gle NWs. The analysis of NWs from the same sample but with different dimensions suggests a decrease of In segregation with the reduction of NW diameter, while Ga distribution seems to remain unaltered. Photoluminescence and Raman scattering measurements carried out on ensembles of NWs exhibi…

Gas-Phase Synthesis of the Elusive Trisilicontetrahydride Species (Si3H4)

2016

The bimolecular gas-phase reaction of ground-state atomic silicon (Si; 3P) with disilane (Si2H6; 1A1g) was explored under single-collision conditions in a crossed molecular beam machine at a collision energy of 21 kJ mol–1. Combined with electronic structure calculations, the results suggest the formation of Si3H4 isomer(s) along with molecular hydrogen via indirect scattering dynamics through Si3H6 collision complex(es) and intersystem crossing from the triplet to the singlet surface. The nonadiabatic reaction dynamics can synthesize the energetically accessible singlet Si3H4 isomers in overall exoergic reaction(s) (−93 ± 21 kJ mol–1). All reasonable reaction products are either cyclic or …

Exotic SiO(2)H(2) Isomers: Theory and Experiment Working in Harmony.

2016

Replacing carbon with silicon can result in dramatic and unanticipated changes in isomeric stability, as the well-studied CO2H2 and the essentially unknown SiO2H2 systems illustrate. Guided by coupled-cluster calculations, three SiO2H2 isomers have been detected and spectroscopically characterized in a molecular beam discharge source using rotational spectroscopy. The cis,trans conformer of dihydroxysilylene HOSiOH, the ground-state isomer, and the high-energy, metastable dioxasilirane c-H2SiO2 are abundantly produced in a dilute SiH4/O2 electrical discharge, enabling precise structural determinations of both by a combination of isotopic measurements and calculated vibrational corrections. …

The Stern-Gerlach experiment revisited

2016

The Stern-Gerlach-Experiment (SGE) of 1922 is a seminal benchmark experiment of quantum physics providing evidence for several fundamental properties of quantum systems. Based on today's knowledge we illustrate the different benchmark results of the SGE for the development of modern quantum physics and chemistry. The SGE provided the first direct experimental evidence for angular momentum quantization in the quantum world and thus also for the existence of directional quantization of all angular momenta in the process of measurement. It measured for the first time a ground state property of an atom, it produced for the first time a `spin-polarized' atomic beam, it almost revealed the electr…