Infrared lattice vibration spectra of tetragonal ZnP2

Infrared reflectivity spectra of tetragonal ZnP₂ are measured in the frequency range from 40 to 600 cm^-1 for both polarization directions E ⊥ c and E 6 c. The parameters of 9 E modes and 4 A₂ modes are determined by a dispersion analysis of the spectra. Three additional A₂ modes are detected by infrared transmission measurements. The results obtained are compared with previous Raman scattering and two-phonon combination mode spectra.     

Raman spectrum of metallic layered compound NbSe2

Raman spectrum of layer-type compound NbSe₂ has been obtained at liquid nitrogen temperature. The frequencies of the Raman active modes E²_2g, A_1g and E¹_2g are measured to be 29.6 cm^?1, 230.9 cm^?1 and 238.3 cm^?1 respectively. The observed second order Raman spectrum of NbSe₂ is very different from the corresponding spectrum of MoS₂. These results show that the force constants of NbSe₂ are less anisotropic than those of MoS₂.     

Raman-scattering spectrum of GaN straight nanowires

The Raman spectrum of GaN straight nanowires deposited on a LaAlO₃ crystal substrate was studied. The E₂ (high) phonon frequency at 560 cm^-1 shows a 9 cm^-1 shift compared with the calculated value. The low-energy shift and band broadening of the Raman modes result from the nanosize effect. The unique property of the low intensity ratio of I_E2/I_A1(LO) on the Raman spectrum from the GaN straight nanowires was observed. Received: 5 June 2000 / Accepted: 7 June 2000 / Published online: 2 August 2000     

Photoluminescence of glassy and single-crystalline GeSe2 measured at 77K

Photoluminescence (PL) and excitation (E) spectra of glassy and crystalline GeSe₂ at 77 K have a broad-band peaked at energy $\text{E}{}_{\mathrm{R}}\text{<}\text{1}\text{2}\text{E}{}_{\mathrm{g}}$. PL spectra have a Gaussian form: the Stokes shift (W_S=?ω?E_R) for crystalline GeSe₂ is greater than that for the glass. The absorption coefficient α at the maxima of E spectra is ～ 10²cm^-1 for the glassy form, and ～ 10⁴cm^-1 for the crystalline form. The results are interpreted in terms of the Mott-Davis-Street model supposing a strong electron-phonon coupling in these types of amorphous semiconductors which explains the large Stokes shift and the broad emission band.     

Influence of thickness on the optical properties of amorphous GeSe2 thin films: analysis using Raman spectra,Urbach energy and Tauc parameter

An analysis is reported of thickness-induced defects in amorphous GeSe₂ thin films deposited by the vacuum evaporation technique. X-ray diffraction studies confirmed the amorphous nature of the thin films. Optical absorption measurements revealed an indirect transition with an energy gap that increases with film thickness. A blue shift in optical transmittance edges was observed in annealed GeSe₂ thin films. The obtained lower values of Urbach energy (E _U) indicate that as thickness increases more ordered films can be produced. Raman spectra suggest that annealing promotes corner-sharing GeSe_4/2 tetrahedra and edge-sharing Ge₂Se_8/2 bi-tetrahedra bonding and leads to the reduction in disorder in bonding network, which is amply supported by the way of increase in band gap, increase in Tauc parameter (B ^1/2) and reduction in E _U from the analysis of transmittance spectra. Increasing the thickness promotes tetrahedral and bi-tetrahedral bonding through the reduction in bonding defects.     

Raman and infrared spectra of CdIn2S4 and ZnIn2S4

Four one-phonon Raman lines have been found in CdIn₂S₄ (ZnIn₂S₄) spinels at 92 (72) cm^-1, 186 (184) cm^-1, 246 (253) cm^-1, and 367 (372) cm^-1 for incident photon energies well below the energy gap E_G ～ 2.4 (2.2) eV at 300 K. For photon energies close to E_G, the 367 cm^-1 mode underwent a resonant enhancement in CdIn₂S₄ and four infrared active but Raman forbidden F_1u modes appeared in the CdIn₂S₄ and ZnIn₂S₄ Raman spectra: TO modes at 226 (221) cm^-1 and 309 (312) cm^-1, and LO modes at 274 (272) cm^-1 and 340 (342) cm^-1.     

Far infrared optical properties of proustite (Ag3AsS3)

The infrared reflection and transmission spectra of Ag₃AsS₃ single crystals have been between 20 and 650 cm^-1 at room temperature. Fourteen phonon modes were observable in reflectivity with the dominant restrahlen bands occuring at 360 cm^-1 and 35 cm^-1 for E? c and at 335 cm^-1 and 35 cm^-1 for E⊥ c. These measurements indicate that generation of far infrared radiation by mixing of two laser frequencies using proustite as the down-conversion crystal is not possible.     

Raman and infrared spectra of ZnSiAs2

The optical phonons at k = 0 of ZnSiAs₂ have been investigated by Raman scattering and infrared reflectivity measurements at 300 K. Eleven of thirteen expected optically active phonons have been observed and identified with respect to their symmetry types. The phonon frequencies appear in the range from 415 cm^-1 to 75 cm^-1 with predominant polar modes at 400 cm^-1 (gG₅), 389 cm^-1 (Γ₄) and 242 cm^-1 (Γ₄). The dielectric dispersion for E ⊥ c and E 6 c has been determined by Kramers-Kronig integrations.     

Vibrational spectra of nitromethanes and the effects of internal rotation

Infrared spectra have been obtained in gas and crystalline phases for CH₃NO₂, CD₃NO₂, and CHD₂NO₂. A few Raman liquid measurements have also been made. The crystal spectra show the methyl group to be locked in conformation I,

with isolated CH stretching frequencies 3065 (ν_∥CH) and 3000 (ν_⊥CH), respectively. In the gas phase, the bands due to ν_aCH₃ and ν_aCD₃ are split, the splitting being compatible with isolated frequencies of 3065 (ν_∥CH) and 3006 (ν_⊥CH) cm^?1, respectively. These indicate a variation of 0.006 Å in bond length during internal rotation. The gas phase infrared band at 3028.7 cm^?1 and the Raman liquid band at 3024 cm^?1 in the spectra of CHD₂NO₂ represent averages of the frequencies during internal rotation. All calculations are performed with a potential function involving variations both in diagonal bond stretching, and in off-diagonal stretching interaction constants, proportional to cos2π, where π is the internal rotation angle.In the Appendix, vibrational assignments below 1600 cm^?1 are examined. Product rule considerations and intensity changes upon deuteration lead to a conflict with the infrared gas phase band contour over the assignment of the rCD₃ mode at 884 cm^?1. This and other features in the gas phase spectra may arise from the internal rotation.     

Raman spectroscopic study of the selenite mineral: ahlfeldite,NiSeO3·2H2O

Raman spectroscopy has been used to study the selenite mineral ahlfeldite. A comparison is made with the Raman spectra of chalcomenite, cobaltomenite and clinochalcomenite. Selenite minerals are characterised by the position of the symmetric stretching mode which is observed at higher wavenumbers than the anti‐symmetric stretching mode. The selenite ion has C_3v symmetry and four modes, 2A₁ and 2E. These modes are observed at 813, 472 cm⁻¹ (A₁) and 685, 710, 727 and 367 and 396 cm⁻¹ (E). Bands assigned to the water stretching vibrations are observed for ahlfeldite at 3385 cm⁻¹, for chalcomenite at 2953, 3184 and 3506 cm⁻¹ and for clinochalcomenite at 2909, 3193 and 3507 cm⁻¹. A comparison of the Raman spectra of chalcomenite, clinochalcomenite and cobaltomenite is made. The position of these bands enabled hydrogen bond distances in the selenite structure to be estimated. Hydrogen bond distances for ahlfeldite, chalcomenite and clinochalcomenite were determined to be similar. Copyright © 2008 John Wiley & Sons, Ltd.     

Optical phonons in CuAlS2

The optical phonons at k=0 of CuAlS₂ have been investigated by Raman scattering, infrared reflectivity and absorption measurements from 50 to 1000 cm^-1 at T=300 K. Eleven of the thirteen expected optically active phonons have been observed and identified with respect to their symmetry types. The phonon frequencies appear in a range from 498 to 76 cm^-1 with predominant polar modes at 445 and 266 cm^-1. The dielectric dispersion for E ⊥ c and E ∥ c has been determined by Kramers-Kronig integrations.     

Raman scattering in FeF3

Peaks in the FeF₃ phonon Raman spectrum are assigned to the A_1g(312 cm^-1) and E_g(105, 187, 450 cm^-1) representations of the D⁶_3d group. Anomalous temperature dependence of the frequency, intensity and line width of the 187 cm^-1 line has been observed.     

High pressure tuning of optical transitions in Mg[Pt(CN)4]·7H2O

Mg[Pt(CN)₄]·7H₂O belongs to the class of tetracyanoplatinates(II) which crystallize in columnar structures. In different M_x[Pt(CN)₄]·yH₂O (MCP) single crystals the in-chain Pt-Pt-distance R varies between 3.67 Å (NaCP) and 3.15 Å (MgCP). Two optical transitions can be observed in polarized emission with the electric field vector E either parallel or perpendicular to the columnar (c)-axis. Polarized emission spectra of MgCP are recorded under hydrostatic pressure up to p ≈ 18 kbar (at 295 K). The transition energy v?₆ can be tuned from 17,600 cm^-1 to about 12,000 cm^-1 (2.18-1.48 eV). The pressure induced red shift for the two transitions is: E 6 c: dv?₆/dp = -320±20 cm^-1/kbar, E ⊥ c: dv?_⊥/dp = -270±20 cm^-1/kbar. These values are discussed in the context of the known functional relationship (for ambient conditions) between v? and R.     

Vibrational spectra of antiferromagnetic FeBO3

Transmission spectra of powdered ferric borate have been measured in the wave number region from 6000 cm^-1 to 30 cm^-1 at room and liq. N₂ temperatures. Eight absorption bands observed are assigned as three A_2u and five E_u phonon modes. Of those modes, the temperature dependence of the E_u mode ar 230 cm^-1 (300 K) and the A_2u mode at 277 cm^-1 (300 K) have been measured in the temperature range containing the Néel temperature. They do not show the influence of magnetic ordering.     

六方相InGaN外延膜的显微Raman散射

用X射线衍射(XRD)技术和显微Raman散射方法对金属有机化学气相沉积(MOCVD)法生长的六方相In_xGa_1-xN薄膜样品进行了研究，观察到了相分离现象和LO声子-等离子耦合模(LPP⁺)，讨论了In_xGa_1-xN的A₁(LO)模被屏蔽的主要物理机制.同时，对Raman谱中E₂和A₁(TO)声子模进行了分析和讨论.在In_xGa_1-xN样品的低温Raman谱中还观察到单电子跃迁产生的Raman散射信号. 关键词： Raman散射 X射线衍射 相分离 应力 LO声子-等离子耦合     

Raman spectroscopic study of the sulfite‐bearing minerals scotlandite,hannebachite and orschallite: implications for the desulfation of soils

The structures of the naturally occurring sulfite‐bearing minerals scotlandite, hannebachite and orschallite have been studied by Raman spectroscopy. Raman bands are observed for scotlandite PbSO₃ at 935, 880, 622 and 474 cm⁻¹ and are assigned to the (SO₃)²⁻ν₁(A₁), ν₃(E), ν₂(A₁) and ν₄(E) vibrational modes, respectively. For hannebachite (CaSO₃)₂·H₂O these bands are observed at 1005, 969 and 655 cm⁻¹ with multiple bands for the ν₄(E) mode at 444, 492 and 520 cm⁻¹. The Raman spectrum of hannebachite is very different from that of the compound CaSO₃·2H₂O. It is proposed, on the basis of Raman spectroscopy, that in the mineral hannebachite, the sulfite anion bonds to Ca through the sulfur atom. The Raman spectrum of the mineral orschallite Ca₃[SO₄](SO₃)₂·12H₂O is complex resulting from the overlap of sulfate and sulfite bands. Raman bands at 1005 cm⁻¹, 1096 and 1215 cm⁻¹ are assigned to the (SO₄)²⁻ν₁ symmetric and ν₃ asymmetric stretching modes. The two Raman bands at 971 and 984 cm⁻¹ are attributed to the (SO₃)²⁻ν₃(E) and ν₁(A₁) stretching vibrations. The formation of sulfite compounds in nature offers a potential mechanism for the removal of sulfates and sulfites from soils. Copyright © 2008 John Wiley & Sons, Ltd.     

Surface polariton dispersion measurement by Raman scattering excited in total reflection condition

We report the first measurement of phonon surface polariton (s.p.) dispersion by a non-forward Raman scattering geometry. The Raman scattering from surface modes was excited by the evanescent electromagnetic wave produced by total reflection at the interface between two transparent media. This Raman Scattering excited in condition of Total Reflection, RSTR, has been applied to the NaClO₃-sapphire interface for studying the surface polariton dispersion in the gap between the TO frequency at 966 cm^-1 and the LO frequency at 983 cm^-1 of sodium chlorate. Comparison is made between the experimental and theoretical dispersion curves.     

Study of （Ga,Mn）N prepared by Mn-ion implantation using optical techniques

This paper reports that （Ga, Mn）N is prepared using implantation of 3at.% Mn Ions into undoped GaN. Structural characterization of the crystals was performed using x-ray diffraetion（XRD）. Detailed XRD measurements have revealed the characteristic of Mn-ion implanted GaN with a small contribution of other compounds. With Raman spectroscopy measurements, the spectra corresponding to the intrinsic GaN layers demonstrate three Raman active excitations at 747, 733 and 566 cm-1 identified as EI（LO）, A1 （LO） and E~, respectively. The Mn-doped GaN layers exhibit additional excitations at 182, 288, 650 725, 363, 506cm^-1 and the vicinity of E~ mode. The modes observed at 182, 288, 650 725em 1 are assigned to macroscopic disorder or vacancy-related defects caused by Mn-ion implantation. Other new phonon modes are assigned to Mnx-Ny, Gax-Mny modes and the local vibrational mode of Mn atoms in the （Ga, Mn）N, which are in fair agreement with the standard theoretical results.     

Infrared reflection spectra of the one-dimensional ionic conductor K— and RbAl priderites

The reflection spectra of the one-dimensional ionic conductors K_1.6Al_1.6Ti_6.4O₁₆ and Rb_1.49Al_1.65Ti_6.35O_15.92 have been measured for the polarizations E ∥ c (channel direction) and E 6 c in the frequency region 60–2000 cm^-1. The spectra of these two compounds are very similar with their features and have the same number of bands. The vibrational mode frequencies are obtained from a Kramers-Kronig analysis for each polarized reflectivity spectrum. A comparison of the corresponding mode frequencies for both priderites shows that only the lowest frequency mode observed in the E 6 c spectra is strongly associated with the alkali ion, while the others are not. The effect due to the non-stoichiometry is not found in the infrared reflection spectra.     

Observation of electronic Raman transitions from the transition metal ions Ti3+ and V4+ highly diluted in α-Al2O3

α-Al₂O₃ : Ti³⁺ (300 mass ppm concentration) at 10 K shows two electronic Raman transitions at 38 cm^-1 and 109 cm^-1. The E symmetry of the scattering matrix agrees with the selection rules for transitions between the ground state B_{$\text{3}\text{2}$} and the E_{$\text{1}\text{2}$} of the ground state manifold ²t_2g.α-Al₂o₃ : V⁴⁺ shows two very weak electronic Raman transitions at about 30 cm^-1 and 56 cm^-1 respectively.