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Unusual behaviour of the spin-phonon coupling in the quasi-one-dimensional antiferromagnet RbCoCl 3. Sci Rep 2022; 12:14065. [PMID: 35982099 PMCID: PMC9388675 DOI: 10.1038/s41598-022-18073-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 08/04/2022] [Indexed: 11/09/2022] Open
Abstract
We present an experimental and theoretical study for the lattice vibrational (phonon) modes in the quasi-one-dimensional (or chain-like) antiferromagnet RbCoCl3 at low temperatures both above and below the two different magnetic phase transitions. Clear evidence is found for the role of spin-phonon interactions in providing a temperature-dependent contribution for the frequencies of the E1g and E2g symmetry phonons that occur with frequencies comparable to those of the spin wave excitations (magnons) in this compound. The behaviour in RbCoCl3, as studied here by Raman scattering experiments, is quite different from that typically observed in rutile-structure antiferromagnets where the spin-phonon coupling has been well characterized. The theory is modified to take account of the strong Ising-like component in the spin Hamiltonian. This enables the spin-phonon coupling parameters to be deduced, with the analysis also revealing the onset of an extra frequency shift for the phonons below the transition temperature TN1 = 28 K associated with magnetic ordering along the Co chains.
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Bright photoluminescence from ordered arrays of SiGe nanowires grown on Si(111). BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2014; 5:2498-504. [PMID: 25671145 PMCID: PMC4311733 DOI: 10.3762/bjnano.5.259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 11/24/2014] [Indexed: 06/02/2023]
Abstract
We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE) in ordered arrays on SiO2/Si(111) substrates. The production method employs Au catalysts with self-limited sizes deposited in SiO2-free sites opened-up in the substrate by focused ion beam patterning for the preferential nucleation and growth of these well-organized NWs. The NWs thus produced have a diameter of 200 nm, a length of 200 nm, and a Ge concentration x = 0.15. Their photoluminescence (PL) spectra were measured at low temperatures (from 6 to 25 K) with excitation at 405 and 458 nm. There are four major features in the energy range of interest (980-1120 meV) at energies of 1040.7, 1082.8, 1092.5, and 1098.5 meV, which are assigned to the NW-transverse optic (TO) Si-Si mode, NW-transverse acoustic (TA), Si-substrate-TO and NW-no-phonon (NP) lines, respectively. From these results the NW TA and TO phonon energies are found to be 15.7 and 57.8 meV, respectively, which agree very well with the values expected for bulk Si1- x Ge x with x = 0.15, while the measured NW NP energy of 1099 meV would indicate a bulk-like Ge concentration of x = 0.14. Both of these concentrations values, as determined from PL, are in agreement with the target value. The NWs are too large in diameter for a quantum confinement induced energy shift in the band gap. Nevertheless, NW PL is readily observed, indicating that efficient carrier recombination is occurring within the NWs.
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Abstract
Selective growth and self-organization of silicon-germanium (SiGe) nanowires (NWs) on focused ion beam (FIB) patterned Si(111) substrates is reported. In its first step, the process involves the selective synthesis of Au catalysts in SiO₂-free areas; its second step involves the preferential nucleation and growth of SiGe NWs on the catalysts. The selective synthesis process is based on a simple, room-temperature reduction of gold salts (Au³⁺Cl₄⁻) in aqueous solution, which provides well-organized Au catalysts. By optimizing the reduction process, we are able to generate a bidimensional regular array of Au catalysts with self-limited sizes positioned in SiO₂-free windows opened in a SiO₂/Si(111) substrate by FIB patterning. Such Au catalysts subsequently serve as preferential nucleation and growth sites of well-organized NWs. Furthermore, these NWs with tunable position and size exhibit the relevant features and bright luminescence that would find several applications in optoelectronic nanodevices.
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Abstract
ABSTRACTOxide films, 0.2-2.0 μm in thickness on Zr-2.5Nb and 11 μm thick on Zr-20Nb alloys, formed in steam at 673 K, have been examined using TEM, XRD and Raman spectroscopy. Columnar grains of mostly monoclinic Zr02 in oxide films on Zr-2.5Nb exhibit a dual texture: a fibre mode with an axis close to the 102m pole and a [001]m growth mode with an orientation relationship [100]m // [4510]α and (010)m // (0001)α with the α-Zr metal. In both modes, “tetragonal” (and/or cubic) ZrO2 was present. Raman spectroscopy differentiated two non-cubic “tetragonal” forms of ZrOz within the [001]m growth texture. In thin oxides (0.5 μm or less), this corresponds to the tetragonal ZrO2 observed in ceramic zirconia and is characterised by a Raman band near 260 cm−1. The 278 and related 438 cm−1 Raman bands observed here in some oxide films (and in other Zr corrosion oxides) are attributed to a separate, non-cubic phase structurally related to the tetragonal ZrO2. The intensities of the 278 and 438 cm−1 bands are dependent not only on the amount of this modified-tetragonal phase but also on the oxide texture (related to the metal texture) and the beam orientation. The lack of Raman response from the “tetragonal” ZrO2 within the fibre mode of texture indicates either a low volume fraction or a cubic-like structure. For oxide on Zr-20Nb, XRD and Raman spectroscopy show a mixture of monoclinic and “tetragonal” ZrO2; the Raman results indicate the “tetragonal” ZrO2 has a high crystal symmetry or nearly cubic structure.
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Abstract
ABSTRACTUltrathin single quantum wells of crystalline silicon (c-Si) confined by SiO2 have been prepared by chemical and thermal processing of silicon-on-insulator wafers. The photoluminescence (PL) produced by these nanometer-thick single wells contains two bands: one exhibits a peak energy of ∼1.8 eV, while the second increases rapidly in peak energy with decreasing c-Si layer thickness. Comparison with theories based on self-consistent first-principles calculations shows that the increase in PL peak energy of the second band is consistent with that predicted for the c-Si energy gap of such wells. It also agrees with the measured band gap variation. The ∼1.8 eV PL band is attributed to the recombination of electron-hole pairs confined at the c-Si/SiO2 interface.
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Direct observation of polarons in electron populated quantum dots by resonant Raman scattering. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2008; 8:789-794. [PMID: 18464407 DOI: 10.1166/jnn.2008.a068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The general problem of the pairing of strongly interacting elementary excitations producing new quasiparticles such as polarons arises in many areas of solid state physics. Recent interest in polaron formation in semiconductor quantum dots has been motivated by the need to understand the physical nature of the carrier relaxation processes and their role in quantum-dot based devices. We report on the direct observation of polarons in InAs/GaAs self-assembled quantum dots populated by few electrons where the polarons are strongly coupled modes of quantum dot phonons and electron intersublevel transitions. The degree of coupling is varied in a systematic way in a set of samples having electron intersublevel spacing changing from larger to smaller than the longitudinal optical phonon energy. The signature of polarons is evidenced clearly by the observation of a large (12-20 meV) anticrossing for both InAs and GaAs-like quantum dot phonons using resonant Raman spectroscopy.
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Stable electroluminescence from passivated nano-crystalline porous silicon using undecylenic acid. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/pssc.200461142] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Spin waves in nickel nanorings of large aspect ratio. PHYSICAL REVIEW LETTERS 2005; 94:137208. [PMID: 15904029 DOI: 10.1103/physrevlett.94.137208] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Indexed: 05/02/2023]
Abstract
The spin dynamics of high-aspect-ratio nickel nanorings in a longitudinal magnetic field have been investigated by Brillouin spectroscopy and the results are compared with a macroscopic theory and three-dimensional micromagnetic simulations. Good agreement is found between the measured and calculated magnetic field dependence of the spin wave frequency. Simulations show that as the field decreases from saturation, the rings switch from a "bamboo" to a novel "twisted bamboo" state at a certain critical field, and predict a corresponding dip in the dependence of the spin wave frequency on the magnetic field.
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Abstract
Hydrogen-terminated porous silicon (pSi-H) films were fabricated through electrochemical anodization of crystalline silicon in hydrofluoric-acid-based solutions. The pSi-H surface was chemically functionalized by thermal reaction with undecylenic acid to produce an organic monolayer covalently attached to the silicon surface through SiC bonds and bearing an acid terminal group. Bovine serum albumin (BSA) was adsorbed onto such surface-modified pSi structures. The resulting surfaces were characterized using scanning electron microscopy (SEM), reflection FT-IR spectroscopy, and ellipsometry. SEM showed that the porous films were damaged and partially lifted off the silicon substrate after a prolonged BSA adsorption. Ellipsometry analysis revealed that the BSA penetrated ∼1.3 µm into the porous structure. The film damage is likely a result of BSA anchoring itself tightly through strong electrostatic interaction with the acid-covered Si sidewalls. A change in surface tension during BSA film formation then causes the pSi layer to buckle and lift off the underlying Si substrate. FT-IR results from the undecylenic-acid-modified pSi surfaces before and after BSA adsorption showed the presence of strong characteristic amide I, II, and III vibrational bands after BSA adsorption. The surface properties of the pSi matrix and its interactions with BSA are examined in this study.Key words: ellipsometry, porous silicon, protein adsorption, surface passivation.
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Magnon squeezing in an antiferromagnet: reducing the spin noise below the standard quantum limit. PHYSICAL REVIEW LETTERS 2004; 93:107203. [PMID: 15447444 DOI: 10.1103/physrevlett.93.107203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Indexed: 05/24/2023]
Abstract
We report the first experimental demonstration of quantum squeezing of a collective spin-wave excitation (magnon) using femtosecond optical pulses to generate correlations involving pairs of spins in an antiferromagnetic insulator MnF2. In the squeezed state, the fluctuations of the magnetization of a crystallographic unit cell vary periodically in time and are reduced below that of the ground-state quantum noise.
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Photoluminescence quenching of chemically functionalized porous silicon by a ruthenium cluster. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/pssa.200306548] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Coupled electron-phonon modes in optically pumped resonant intersubband lasers. PHYSICAL REVIEW LETTERS 2003; 90:077402. [PMID: 12633270 DOI: 10.1103/physrevlett.90.077402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2002] [Indexed: 05/24/2023]
Abstract
Intersubband lasing at 12-16 microm based on a CO2 laser pumped stimulated resonant Raman process in GaAs/AlGaAs three-level double-quantum-well structures is reported. The presence, or lack of, lasing action provides evidence for resonantly coupled modes of collective electronic intersubband transitions and longitudinal optical phonons. An anticrossing behavior of these modes is clearly seen when the difference between the pump and lasing energies (i.e., Stokes Raman shift) is compared with the subband separation. This work reveals the significance of the strong coupling between intersubband transitions and phonons and raises a new possibility of realizing a phonon "laser."
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Spin-wave quantization in ferromagnetic nickel nanowires. PHYSICAL REVIEW LETTERS 2002; 89:027201. [PMID: 12097013 DOI: 10.1103/physrevlett.89.027201] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2002] [Indexed: 05/23/2023]
Abstract
The dynamical properties of uniform two-dimensional arrays of nickel nanowires have been investigated by inelastic light scattering. Multiple spin waves are observed that are in accordance with dipole-exchange theory predictions for the quantization of bulk spin waves. This first study of the spin-wave dynamics in ferromagnetic nanowire arrays reveals strong mode quantization effects and indications of a subtle magnetic interplay between nanowires. The results show that it is important to take proper account of these effects for the fundamental physics and future technological developments of magnetic nanowires.
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The Raman spectrum of tin tetraiodide: temperature and pressure measurements and lattice dynamical calculations. ACTA ACUST UNITED AC 2001. [DOI: 10.1088/0022-3719/11/8/027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Structural and magnetic transitions in nickel iodine boracite: a light scattering study. ACTA ACUST UNITED AC 2001. [DOI: 10.1088/0022-3719/11/23/012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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24
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Examples of a dynamic Jahn-Teller system: Raman scattering from electronic excitations and phonons in paramagnetic and antiferromagnetic FeCl2and FeBr2. ACTA ACUST UNITED AC 2001. [DOI: 10.1088/0022-3719/11/10/025] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Raman spectroscopy and dielectric constants of ferroelectric Rochelle salt and calcium tartrate. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/17/20/017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Magnetic ordering and Raman scattering from electronic excitations and phonons in uranium trichalcogenides. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/20/12/016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Shell Structure and Electronic Excitations of Quantum Dots in a Magnetic Field Probed by Inelastic Light Scattering. PHYSICAL REVIEW LETTERS 1996; 77:354-357. [PMID: 10062430 DOI: 10.1103/physrevlett.77.354] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Surface structure, lattice dynamics, and Raman spectroscopy of sulphur passivated InP(001). PHYSICAL REVIEW LETTERS 1995; 75:878-881. [PMID: 10060141 DOI: 10.1103/physrevlett.75.878] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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42
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Brillouin spectroscopic evidence for a relaxation mode in ferroelectric PbHPO4 and PbDPO4. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:8005-8011. [PMID: 9977408 DOI: 10.1103/physrevb.51.8005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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43
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Depth-dependent disordering in a-Si produced by self-ion-implantation. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:17080-17084. [PMID: 9976105 DOI: 10.1103/physrevb.50.17080] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Birefringence-induced vibrational Raman and Rayleigh optical activity in uniaxial crystals. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:182-188. [PMID: 10009272 DOI: 10.1103/physrevb.49.182] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Resonant Raman scattering in an InSb/In1-xAlxSb strained-layer superlattice and in In1-xAlxSb epilayers on InSb. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:11234-11239. [PMID: 10007431 DOI: 10.1103/physrevb.48.11234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Phonon Raman scattering in InSb/In1-xAlxSb strained-layer superlattices. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:11228-11233. [PMID: 10007430 DOI: 10.1103/physrevb.48.11228] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Finite-size effects on superlattice acoustic phonons. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:11960-11964. [PMID: 10007539 DOI: 10.1103/physrevb.48.11960] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Resonant Raman scattering in InSb/In1-xAlxSb superlattices. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:8442-8445. [PMID: 10007044 DOI: 10.1103/physrevb.48.8442] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Magnon and acoustic-phonon light scattering from Bi-doped yttrium iron garnet. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:6099-6103. [PMID: 10009146 DOI: 10.1103/physrevb.48.6099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Raman scattering from folded acoustic phonons and photoluminescence in multilayer GaAs-AlAs superlattices. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:13553-13560. [PMID: 10005666 DOI: 10.1103/physrevb.47.13553] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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