Identification of the fundamental vibrational modes of trigonal, α - monoclinic and amorphous selenium

Lucovsky, G.; Mooradian, A.; Taylor, W.; Wright, George B.; Keezer, R.C.

doi:10.1016/0038-1098(67)90006-3

Cited by 388 publications

(173 citation statements)

References 8 publications

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“…Selenium exists mainly in three polymorphs, the principal one being a trigonal phase, consisting of helical chains, with a less stable monoclinic phase, consisting of Se 8 rings, and amorphous selenium consisting of a mixture of disordered chains. These three different structures have Raman resonance peaks at ~235 cm 1 , ~256 cm 1 , and ~264 cm 1 , respectively [22]. Figure 2 displays the Raman spectrum of the a-Se powder product.…”

Section: Resultsmentioning

confidence: 99%

Preparation of monodisperse Se colloid spheres and Se nanowires using Na2SeSO3 as precursor

Liu

Peng

2008

Nano Res.

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Nearly monodisperse spherical amorphous Se colloids are prepared by the dismutation of Na 2 SeSO 3 solution at room temperature; by altering the pH of the solution, amorphous Se colloid spheres with sizes of about 120 nm, 200 nm, 300 nm, and 1 μm can be obtained. Se@Ag 2 Se core/shell spheres are successfully synthesized by using the obtained amorphous Se (a-Se) spheres as templates, indicating the potential applications of these Se nanomaterials in serving as soft templates for other selenides. Meanwhile, selenium nanowires are obtained through a "solid-solution-solid" growth process by dispersing the prepared Se spheres in ethanol. This simple and environmentally benign approach may offer more opportunities in the synthesis and applications of nanocrystal materials.

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Section: Resultsmentioning

confidence: 99%

Preparation of monodisperse Se colloid spheres and Se nanowires using Na2SeSO3 as precursor

Liu

Peng

2008

Nano Res.

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“…The other feature at 257 cm −1 matches the characteristics of a mode associated to selenium 26,38 and its width (∼20 cm −1 ) suggests an amorphous phase (a-Se) 39,40 . The narrower peak (∼5 cm −1 ) at 241 cm −1 appears last and is associated 41 to a selenium crystalline phase (c-Se). As it has been often demonstrated, a-Se easily photocrystallizes 42,43 .…”

Section: Fig 1 Evolution Of the Raman Spectrum Of A 45 Nm-thickmentioning

confidence: 99%

Oxidation dynamics of ultrathin GaSe probed through Raman spectroscopy

Bergeron

Ibrahim

Leonelli

et al. 2017

Applied Physics Letters

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Gallium selenide (GaSe) is a 2D material with a thickness-dependent gap, strong non-linear optical coefficients and uncommon interband optical selection rules, making it interesting for optoelectronic and spintronic applications. In this work, we monitor the oxidation dynamics of GaSe with thicknesses ranging from 10 to 200 nm using Raman spectroscopy. In ambient temperature and humidity conditions, the intensity of all Raman modes and the luminescence decrease rapidly with moderate exposure to above-gap illumination. Concurrently, several oxidation products appear in the Raman spectra: Ga 2 Se 3 , Ga 2 O 3 and amorphous and crystalline selenium. We find that no safe measurement power exists for optical measurements on ultrathin GaSe in ambient conditions. We demonstrate that the simultaneous presence of oxygen, humidity, and abovegap illumination is required to activate this photo-oxidation process, which is attributed to the transfer of photo-generated charge carriers towards aqueous oxygen at the sample surface, generating highly reactive superoxide anions that rapidly degrade the sample and quench the optical response of the material.

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“…To understand the nature of the experimentally observed differences between the bulk and the surface VDoS, ab initio and semiempirical calculations based on molecular orbital theory were employed for various Se clusters containing coordination defects. At the outset, Se 6 and Se 8 rings, vibrational features of which are accurately known from Raman scattering experiments 22,23 , were calculated by both methods ( Supplementary Fig. S1).…”

Section: Experimental Vdos For Bulk and Surface-sensitive Geometriesmentioning

confidence: 99%

Vibrational dynamics and surface structure of amorphous selenium

et al. 2011

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In contrast to crystalline solids in which structural order governs dynamics and thermodynamics, the lack of long-range periodicity in amorphous materials is responsible for several anomalies. Although the relation between these anomalies and the 'bulk structure' is generally understood, the surface structure and the corresponding vibrational spectrum of amorphous solids is practically an unexplored theme. In this study, we resolve the differences in vibrational dynamics and atomic structure between bulk and surface (top 5 nm) atoms of amorphous selenium. We combine experimental (grazing incidence inelastic X-ray scattering) and computational (ab initio and semiempirical molecular orbital theoretical calculations) methods to scrutinize a variety of possible structural models. We find that a high concentration of particular types of 'coordination defects' in the surface layer is responsible for the observed differences. Resolving the structure of amorphous surfaces is, for example, important for understanding nanoparticles' properties where the surface-to-bulk ratio has a crucial role.

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Identification of the fundamental vibrational modes of trigonal, α - monoclinic and amorphous selenium

Cited by 388 publications

References 8 publications

Preparation of monodisperse Se colloid spheres and Se nanowires using Na2SeSO3 as precursor

Preparation of monodisperse Se colloid spheres and Se nanowires using Na2SeSO3 as precursor

Oxidation dynamics of ultrathin GaSe probed through Raman spectroscopy

Vibrational dynamics and surface structure of amorphous selenium

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