Pure Se glass and ternary A
To understand the unique physical properties of GaSbSe glasses, high‐resolution X‐ray photoelectron spectroscopy (XPS) studies are performed on representative compositions within the glass‐forming region. The observed peaks in the valence band as well as in Ga, Sb, and Se core‐level XPS spectra are related to the main structural building blocks of the covalent network. On the basis of disproportionality equations and quantitative XPS analysis, the SeSeSe fragments are shown to exist in the glasses with 65 and 68 at% of Se, whereas the samples with lower Se content are shown to contain a significant concentration of SeSe bonds instead. Although the majority of Ga atoms are deemed to form fourfold coordinated units, the existence of Ga atoms in threefold coordination, those bonded to other metal, and forming Ga clusters of undissolved Ga are also plausible on the basis of Ga 3
- NSF-PAR ID:
- 10221182
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- physica status solidi (b)
- Volume:
- 258
- Issue:
- 6
- ISSN:
- 0370-1972
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
x By Se1−x −y glasses where A = Ge and B = P or As, in the low mean coordination number, ⟨r ⟩, range of 2.00 < ⟨r ⟩ < 2.12 display a 3‐ to 5‐fold reduction in the width of the glass transition when aged at room temperature over 4–8 months. Group IV (Ge) and group V (P, As) additives serve to crosslink the base Se glass polymeric chains, Sen , withn > 250 atoms and to reduce the length “n ” between cross‐link points asx andy are increased. Herein, it is shown that in such weakly crosslinked glasses, the continued narrowing of the glass transition widthT gby a factor of 3–5, as in pure Se, stems from the fact that polymeric Sen chain segments between the crosslink points continue to have a lengthn of at least eight atoms or more. Such polymeric Sen chains are super‐flexible and reconstruct with each, as in pure Se, promoting structural ordering responsible forT gnarrowing. Whenn < 8, super flexibility is steadily lost. Along with the flexible, intermediate, and stressed‐rigid phases, a new super‐flexible phase of Se and Se‐rich glasses is obtained. -
Material properties of Ga–Sb binary alloy thin films deposited under ultra-high vacuum conditions were studied for analog phase change memory (PCM) applications. Crystallization of this alloy was shown to occur in the temperature range of 180–264 °C, with activation energy >2.5 eV depending on the composition. X-ray diffraction (XRD) studies showed phase separation upon crystallization into two phases, Ga-doped A7 antimony and cubic zinc-blende GaSb. Synchrotron in situ XRD analysis revealed that crystallization into the A7 phase is accompanied by Ga out-diffusion from the grains. X-ray absorption fine structure studies of the local structure of these alloys demonstrated a bond length decrease with a stable coordination number of 4 upon amorphous-to-crystalline phase transformation. Mushroom cell structures built with Ga–Sb alloys on ø110 nm TiN heater show a phase change material resistance switching behavior with resistance ratio >100 under electrical pulse measurements. TEM and Energy Dispersive Spectroscopy (EDS) studies of the Ga–Sb cells after ∼100 switching cycles revealed that partial SET or intermediate resistance states are attained by the variation of the grain size of the material as well as the Ga content in the A7 phase. A mechanism for a reversible composition control is proposed for analog cell performance. These results indicate that Te-free Ga–Sb binary alloys are potential candidates for analog PCM applications.more » « less
-
Photoelectrochemical (PEC) hydrogen generation is a promising solar energy harvesting technique to address the concerns about the ongoing energy crisis. Antimony selenide (Sb2Se3) with van der Waals‐bonded quasi‐1D (Q1D) nanoribbons, for instance, (Sb4Se6)
n , has attracted considerable interest as a light absorber with Earth‐abundant elements, suitable bandgap, and a desired sunlight absorption coefficient. By tuning its anisotropic growth behavior, it is possible to achieve Sb2Se3films with nanostructured morphologies that can improve the light absorption and photogenerated charge carrier separation, eventually boosting the PEC water‐splitting performance. Herein, high‐quality Sb2Se3films with nanorod (NR) array surface morphologies are synthesized by a low‐cost, high‐yield, and scalable close‐spaced sublimation technique. By sputtering a nonprecious and scalable crystalline molybdenum sulfide (MoS2) film as a cocatalyst and a protective layer on Sb2Se3NR arrays, the fabricated core–shell structured MoS2/Sb2Se3NR PEC devices can achieve a photocurrent density as high as −10 mA cm−2at 0 VRHEin a buffered near‐neutral solution (pH 6.5) under a standard simulated air mass 1.5 solar illumination. The scalable manufacturing of nanostructured MoS2/Sb2Se3NR array thin‐film photocathode electrodes for efficient PEC water splitting to generate solar fuel is demonstrated. -
Abstract We present a nearly complete rapid neutron-capture process ( r -process) chemical inventory of the metal-poor ([Fe/H] = −1.46 ± 0.10) r -process-enhanced ([Eu/Fe] = +1.32 ± 0.08) halo star HD 222925. This abundance set is the most complete for any object beyond the solar system, with a total of 63 metals detected and seven with upper limits. It comprises 42 elements from 31 ≤ Z ≤ 90, including elements rarely detected in r -process-enhanced stars, such as Ga, Ge, As, Se, Cd, In, Sn, Sb, Te, W, Re, Os, Ir, Pt, and Au. We derive these abundances from an analysis of 404 absorption lines in ultraviolet spectra collected using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope and previously analyzed optical spectra. A series of appendices discusses the atomic data and quality of fits for these lines. The r -process elements from Ba to Pb, including all elements at the third r -process peak, exhibit remarkable agreement with the solar r -process residuals, with a standard deviation of the differences of only 0.08 dex (17%). In contrast, deviations among the lighter elements from Ga to Te span nearly 1.4 dex, and they show distinct trends from Ga to Se, Nb through Cd, and In through Te. The r -process contribution to Ga, Ge, and As is small, and Se is the lightest element whose production is dominated by the r -process. The lanthanide fraction, log X La = −1.39 ± 0.09, is typical for r -process-enhanced stars and higher than that of the kilonova from the GW170817 neutron-star merger event. We advocate adopting this pattern as an alternative to the solar r -process-element residuals when confronting future theoretical models of heavy-element nucleosynthesis with observations.more » « less
-
Abstract This research provides a new method for preparing nanoparticle‐coated viscose nonwoven fabrics, which has broad application prospects in the functional fiber industry. In this work amino‐terminated hyperbranched polymer (HBP)‐capped Selenium nanoparticles (Se NPs) were synthesized for coating viscose nonwoven fabric (VNF) via impregnation method to produce a controllable and uniform Se NPs coating on the viscose fiber surface. The prepared Se NPs and the treated VNF were characterized by the transmission electron microscope (TEM), x‐ray diffraction (XRD), x‐ray photoelectron spectroscopy (XPS), field emission scanning electron microcopy (FE‐SEM), and antibacterial measurement. The results indicate that the Se NPs were spherical shaped with an average size of 50 nm. FESEM, XRD, and XPS characterizations demonstrated that Se NPs can adsorbed and distributed uniformly on the fiber surface. Se NPs‐coated VNF showed above 99.9% bacterial reduction of
Staphylococcus aureus andEscherichia coli while the Se element content on VNF was about 2.92 mg/g.