Elastic scattering of molecular beams for the determination of intermolecular potentials.
High energy and thermal energy molecular beams elastic scattering for intermolecular potentials determination
Bernstein, R. B.↗
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Results for “molecular beam”
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Hyperfine spectrum of NaCl by molecular-beam electric resonance.
Hyperfine spectrum analysis of NaCl at low field using molecular beam electric resonance method, discussing Hamiltonian function representation
Cederberg, J. W.↗
Molecular-beam investigations of the dissociation of nitrous oxide on tungsten
Nitrous oxide molecular beam reflection and dissociation on tungsten surface at high temperatures from angular distribution measurements
Coltharp, R. N.↗
Coherent growth and characterization of van der Waals 1T-VSe2 layers on GaAs(111)B using molecular beam epitaxy
We report epitaxial growth of vanadium diselenide (VSe₂) thin films in the octahedrally coordinated (1T) structure on GaAs(111)B substrates by molecular beam epitaxy. Film thickness from a single monolayer (ML) up to 30 ML is demonstrated. Structural and chemical studies using x-ray diffraction, transmission electron microscopy, scanning tunneling microscopy, and x-ray photoelectron spectroscopy indicate high-quality thin films. Further studies show that monolayer VSe₂ films on GaAs are not air stable and are susceptible to oxidation within a matter of hours, which indicates that a protective capping layer should be employed for device applications. This work demonstrates that VSe₂, a candidate van der Waals material for possible spintronic and electronic applications, can be integrated with III-V semiconductors via epitaxial growth for two- and three-dimensional hybrid devices.
2D materials↗
Adsorption-controlled growth of MnTe(Bi2Te3)n by molecular beam epitaxy exhibiting stoichiometry-controlled magnetism
We report the growth of the intrinsic magnetic topological system MnTe ( Bi 2 Te 3 ) n by molecular beam epitaxy. By mapping the temperature and the Bi:Mn flux ratio, it is shown that there is a narrow growth window for the n = 1 phase Mn Bi 2 Te 4 with 2.0 < Bi : Mn < 2.6 at 225°C. In this work, the films are stoichiometric and excess Bi and Te is not incorporated. At higher flux ratios (Bi:Mn≥4.5) it is found that the n = 2 Mn Bi 4 Te 7 phase is stabilized. Transport measurements indicate that the Mn Bi 2 Te 4 and Mn Bi 4 Te 7 undergo magnetic transitions around 25 and 10 K, respectively, consistent with antiferromagnetic phases found in the bulk. Further, for Mn-rich conditions (Bi:Mn<2), ferromagnetism emerges that exhibits a clear hysteretic state in the Hall effect, which likely indicates Mn-doped Mn Bi 2 Te 4 . Understanding how to grow ternary chalcogenide phases is the key to synthesizing new materials and to interface magnetism and topology, which together are routes to realize and control exotic quantum phenomena.
36 MATERIALS SCIENCE↗
Precursor selection in hybrid molecular beam epitaxy of alkaline-earth stannates
One of the challenges of oxide molecular beam epitaxy (MBE) is the synthesis of oxides containing metals with high electronegativity (metals that are hard to oxidize). The use of reactive organometallic precursors can potentially address this issue. To investigate the formation of radicals in MBE, we explored three carefully chosen metal-organic precursors of tin for SnO 2 and BaSnO 3 growth: tetramethyltin (TMT), tetraethyltin (TET), and hexamethylditin (HMDT). All three precursors produced single-crystalline, atomically smooth, and epitaxial SnO 2 (101) films on r-Al 2 O 3 (101¯2) in the presence of oxygen plasma. The study of growth kinetics revealed reaction-limited and flux-limited regimes except for TET, which also exhibited a decrease in the deposition rate with increasing temperature above ~800 °C. Contrary to these similarities, the performance of these precursors was dramatically different for BaSnO 3 growth. TMT and TET were ineffective in supplying adequate tin, whereas HMDT yielded phase-pure, stoichiometric BaSnO 3 films. Significantly, HMDT resulted in phase-pure and stoichiometric BaSnO 3 films even without the use of an oxygen plasma (i.e., with molecular oxygen alone). Furthermore, these results are discussed using the ability of HMDT to form tin radicals and therefore assisting with Sn → Sn 4+ oxidation reaction. Structural and electronic transport properties of films grown using HMDT with and without oxygen plasma are compared. This study provides guideline for the choice of precursors that will enable the synthesis of metal oxides containing hard-to-oxidize metals using reactive radicals in MBE.
36 MATERIALS SCIENCE↗
Pyrolysis_Molecular_Beam_Mass_Spectra_for_Standard_Biomass_Samples_and_Natural_Variants_of_Switchgrass_Grown_Under_Different_Conditions
This data consists of total ion chromatogram (TIC) normalized Pyrolysis-Molecular Beam Mass Spectrometry (py-MBMS) spectra collected to predict lignin content and lignin monomeric ratios for “Variation in Biomass Yield and Cell Wall Composition in Switchgrass Natural Variants Under Two Nitrogen Regimes” (https://doi.org/10.1007/s12155-025-10838-8).
09 BIOMASS FUELS↗
A 100 microsec, reliable, 10 Hz pulsed supersonic molecular beam source
A 10-Hz repetition rate, 100-microsec duration, reliable pulsed supersonic molecular beam source is described. Mechanical and electrical design of the pulsed valve are given in detail. Characteristics of the supersonic expansion obtained using coherent anti-Stokes Raman spectroscopy in acetylene are presented. They include pulse shape, gas rotational and translational cooling as a function of distance from the nozzle, clustering effects, and shock heating at the leading edge of the pulse.
Byer, R. L.↗
Heavily boron-doped Si layers grown below 700 C by molecular beam epitaxy using a HBO2 source
Boron doping in Si layers grown by molecular beam epitaxy (MBE) at 500-700 C using an HBO2 source has been studied. The maximum boron concentration without detectable oxygen incorporation for a given substrate temperature and Si growth rate has been determined using secondary-ion mass spectrometry analysis. Boron present in the Si MBE layers grown at 550-700 C was found to be electrically active, independent of the amount of oxygen incorporation. By reducing the Si growth rate, highly boron-doped layers have been grown at 600 C without detectable oxygen incorporation.
Lin, T. L.↗
Fabrication of IrSi(3)/p-Si Schottky diodes by a molecular beam epitaxy technique
IrSi(3)/p-Si Schottky diodes have been fabricated by a molecular beam epitaxy technique at 630 C. Good surface morphology was observed for IrSi(3) layers grown at temperatures below 680 C, and an increasing tendency to form islands is observed in samples grown at higher temperatures. Good diode current-voltage characteristics were observed and Schottky barrier heights of 0.14-0.18 eV were determined by activation energy analysis and spectral response measurement.
Lin, T. L.↗
Evidence for In-Plane Electrical Polarization in 3R-β’-In 2 Se 3 Thin Films Grown by Molecular Beam Epitaxy
β-In 2 Se 3 has been identified as a potential ferroelectric. This work describes the growth of β-In 2 Se 3 via molecular beam epitaxy along with a description of its properties, including the search for switchable polarization in 3R-β’-In2Se3. The thin-film morphology, crystal structure, and phase maps of β-In 2 Se 3 on Si(111) and Al 2 O 3 (0001) were evaluated by atomic force microscopy, X-ray diffraction, and Raman spectroscopy as a function of the atomic Se/In flux ratio and growth temperature. Smooth β-In 2 Se 3 thin films were successfully realized on Si(111) at a substrate temperature of 150 °C using a Se/In flux ratio of 5.7, as well as on Al 2 O 3 (0001) at 450 °C using a Se/In flux ratio of 5.5. Scanning transmission electron microscopy (STEM) confirms the 3R polytype of β-In 2 Se 3 in films on both substrates, with a minor disorder associated with the 2H polytype at the interface. Indications of in-plane Se atom displacements characteristic of the 3R-β’-In 2 Se 3 polytype were found by STEM and second harmonic generation analysis in films on Al 2 O 3 (0001), but not in films on Si(111). Furthermore, attempts at electrical polarization switching did not produce compelling evidence for ferroelectricity. Instead, electrical transport measurements demonstrated locally varying anisotropic responses with the applied electric fields along different in-plane directions, with some hysteresis associated with the trapping of charges.
36 MATERIALS SCIENCE↗
Machine learning analysis of perovskite oxides grown by molecular beam epitaxy
Reflection high-energy electron diffraction (RHEED) is a ubiquitous in situ molecular beam epitaxial (MBE) characterization tool. Although RHEED can be a powerful means for crystal surface structure determination, it is often used as a static qualitative surface characterization method at discrete intervals during a growth. A full analysis of RHEED data collected during the entirety of MBE growths is made possible using principle component analysis (PCA) and $\textit{k}$-means clustering to examine significant boundaries that occur in the temporal clusters grouped from RHEED data and identify statistically significant patterns. This process is applied to data from homoepitaxial SrTiO 3 growths, heteroepitaxial SrTiO 3 grown on scandate substrates, BaSnO 3 films grown on SrTiO 3 substrates, and LaNiO 3 films grown on SrTiO 3 substrates. We report this analysis may provide additional insights into the surface evolution and transitions in growth modes at precise times and depths during growth, and that video archival of an entire RHEED image sequence may be able to provide more insight and control overgrowth processes and film quality.
36 MATERIALS SCIENCE↗
Elimination of remnant phases in low-temperature growth of wurtzite ScAlN by molecular-beam epitaxy
Growth of wurtzite ScxAl1−xN (x < 0.23) by plasma-assisted molecular-beam epitaxy on cplane GaN at high temperatures significantly alters the extracted lattice constants of the material due to defects likely associated with remnant phases. In contrast, ScAlN grown below a composition-dependent threshold temperature exhibits uniform alloy distribution, reduced defect density, and atomic-step surface morphology. The c-plane lattice constant of this low-temperature ScAlN varies with composition as expected from previous theoretical calculations and can be used to reliably estimate alloy composition. Moreover, lattice-matched Sc0.18Al0.82N/GaN multiquantum wells grown under these conditions display strong and narrow near-infrared intersubband absorption lines that confirm advantageous optical and electronic properties.
Dzuba, Brandon↗
Silicon sheet with molecular beam epitaxy for high efficiency solar cells
The capabilities of the new technique of Molecular Beam Epitaxy (MBE) are applied to the growth of high efficiency silicon solar cells. Because MBE can provide well controlled doping profiles of any desired arbitrary design, including doping profiles of such complexity as built-in surface fields or tandem junction cells, it would appear to be the ideal method for development of high efficiency solar cells. It was proposed that UCLA grow and characterize silicon films and p-n junctions of MBE to determine whether the high crystal quality needed for solar cells could be achieved.
Allen, F. G.↗
X-ray photoelectron spectroscopic study of the oxide removal mechanism of GaAs /100/ molecular beam epitaxial substrates in in situ heating
A standard cleaning procedure for GaAs (100) molecular beam epitaxial (MBE) substrates is a chemical treatment with a solution of H2SO4/H2O2/H2O, followed by in situ heating prior to MBE growth. X-ray photoelectron spectroscopic (XPS) studies of the surface following the chemical treatment show that the oxidized As is primarily As(+ 5). Upon heating to low temperatures (less than (350 C) the As(+ 5) oxidizes the substrate to form Ga2O3 and elemental As, and the As(+ 5) is reduced to As(+ 3) in the process. At higher temperatures (500 C), the As(+ 3) and elemental As desorb, while the Ga(+ 3) begins desorbing at about 600 C.
Vasquez, R. P.↗
Extrema-effect in total elastic molecular beam scattering cross sections for characterization of the potential well.
Extrema-effect in total elastic molecular beam scattering cross sections for characterizing potential well
MOLECULAR COLLISION↗
Pyrolysis Molecular Beam Mass Spectrometry_Analysis_of_Natural_Variants_of_Poplulus_Trichocarpa_Leaves
Select leaves from natural variants of Poplar (Populus Trichocarpa) grown in a greenhouse at Oak Ridge National Laboratory were analyzed by Pyrolysis-Molecular Beam Mass Spectrometry (Py-MBMS). Leaves were harvested, cryomilled and kept frozen until analysis. Py-MBMS analysis was conducted using approximately 4 mg of biomass and each sample was analyzed in duplicate. A Frontier PY2020 unit pyrolyzed samples at 500°C for 30 s in 80 µL deactivated stainless steel cups. An Extrel Super-Sonic MBMS Model Max 1000 was used to collect mass spectral data fromm/z30 to 450 at 17 eV and processed using Merlin Automation software (V3). Spectral ion intensities were normalized to the total ion chromatogram signal for each sample for analysis of spectral variance. Lignin content (wt %) was estimated based on relative responses from standards of known Klason lignin content using mean-normalized ion intensities ofm/z120, 124 (G), 137 (G), 138 (G), 150 (G), 152, 154 (S), 164 (G), 167 (S), 168 (S), 178 (G), 180, 181, 182 (S), 194 (S), 208 (S) and 210 (S) where G indicates guaiacyl-derived ions, S indicates syringyl-derived ions, and other ions either derive from other lignin monomers or multiple sources. Ratios of S and G lignin monomer units (S/G) were obtained by dividing the sum of S-based ions by the sum of G-based ions using mean-normalized ion intensities.
CBI↗
Study of the structure, structural transition, interface model, and magnetic moments of CrN grown on MgO(001) by molecular beam epitaxy
Structural phase transition is studied in high quality CrN thin films grown by molecular beam epitaxy on MgO(001) substrates. Cross-sectional transmission electron microscopy and x-ray diffraction reveal that the epitaxial relationship between CrN film and MgO substrate is [100] CrN /[100] MgO , [110] CrN /[110] MgO , and [001] CrN /[001] MgO . The films show tensile strain/compression at the CrN/MgO(001) interface, which relaxes gradually with the film growth. Temperature dependent x-ray diffraction measurements show a first-order structural phase transition. In addition to the experimental measurements, first-principles theoretical calculations have been carried out for finding a stable model for the CrN/MgO interface. Furthermore, these calculations determine two possible models for the interface, where a monolayer of chromium oxide is formed between the CrN and MgO layers.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗