Transmission spectra of epitaxial layers of Pb1 ? xEuxTe (0 ≤ x ≤ 0.37) solid solutions in the frequency range 7–4000 cm?1

The spectra of epitaxial Pb_{1 − x} Eu _x Te (0 ≤ x ≤ 0.37) solid solution layers grown on BaF₂ and Si substrates have been investigated over a wide frequency range 7–4000 cm⁻¹ at temperatures of 5–300 K. Apart from the phonon and impurity absorption lines, the absorption in a local mode in PbEuTe layers of substrates and buffer layers has been observed in the frequency range 110–114 cm⁻¹. As the temperature decreases from 300 to 5 K, the transverse phonon mode softens from 33.0 to 19.5 cm⁻¹.     

A Raman spectroscopic study of humite minerals

Raman spectroscopy has been used to study the structure of the humite mineral group ((A₂SiO₄)_n–A(OH, F)₂ where n represents the number of olivine and brucite layers in the structure and is 1, 2, 3 or 4 and A²⁺ is Mg, Mn, Fe or some mix of these cations). The humite group of minerals forms a morphotropic series with the minerals olivine and brucite. The members of the humite group contain layers of the olivine structure that alternate with layers of the brucite‐like sheets. The minerals are characterized by a complex set of bands in the 800–1000 cm⁻¹ region attributed to the stretching vibrations of the olivine (SiO₄)⁴⁻ units. The number of bands in this region is influenced by the number of olivine layers. Characteristic bending modes of the (SiO₄)⁴⁻ units are observed in the 500–650 cm⁻¹ region. The brucite sheets are characterized by the OH stretching vibrations in the 3475–3625 cm⁻¹ wavenumber region. The position of the OH stretching vibrations is determined by the strength of the hydrogen bond formed between the brucite‐like OH units and the olivine silica layer. The number of olivine sheets and not the chemical composition determines the strength of the hydrogen bonds. Copyright © 2006 John Wiley & Sons, Ltd.     

Layer‐dependent resonant Raman scattering of a few layer MoS2

We report resonant Raman scattering of MoS₂ layers comprising of single, bi, four and seven layers, showing a strong dependence on the layer thickness. Indirect band gap MoS₂ in bulk becomes a direct band gap semiconductor in the monolayer form. New Raman modes are seen in the spectra of single‐ and few‐layer MoS₂ samples which are absent in the bulk. The Raman mode at ~230 cm⁻¹ appears for two, four and seven layers. This mode has been attributed to the longitudinal acoustic phonon branch at the M point (LA(M)) of the Brillouin zone. The mode at ~179 cm⁻¹ shows asymmetric character for a few‐layer sample. The asymmetry is explained by the dispersion of the LA(M) branch along the Γ‐M direction. The most intense spectral region near 455 cm⁻¹ shows a layer‐dependent variation of peak positions and relative intensities. The high energy region between 510 and 645 cm⁻¹ is marked by the appearance of prominent new Raman bands, varying in intensity with layer numbers. Resonant Raman spectroscopy thus serves as a promising non invasive technique to accurately estimate the thickness of MoS₂ layers down to a few atoms thick. Copyright © 2012 John Wiley & Sons, Ltd.     

Theoretical calculations and Raman spectrum of intercalation modes in LixInSe

By using an extended linear-chain model which includes the interlayer forces, we have calculated the new vibrational modes, of Li intercalated InSe. The dispersion curves along thek _z wavevector perpendicular to the layers for the -polytype are determined in the first Brillouin zone. Assuming that the interlayer interaction is not modified upon intercalation and the interaction between lithium atom and adjacent layers in the van der Waals plane has the same value than the interlayer one, the new modes are determined with the force constant given by the rigid layer mode of the, -polytype at 18 cm^–1. This model gives the variation of the acoustic branches and the appearance of two optical intercalation modes at higher frequencies. The Brillouin zone boundary modes of the acoustic branches at 18 and 41 cm^–1 in the pure material are calculated to be 22 and 50 cm^–1 respectively forx=1/2. The dispersion of the new optical branches is flat along thez-direction and frequencies are obtained at 96 cm^–1 for the Li mode perpendicular tok _z and at 218 cm^–1 for the Li mode parallel tok _z. We compare also our results with the Li mode frequencies obtained in a total energy calculation. Raman scattering experiments have been performed in intercalated sample in order to verify the proposed model.     

张应力对准同形相界Pb(Zr,Ti)O3薄膜相变和铁电性能影响

采用射频磁控溅射法在Pt/TiO_x/SiO₂/Si基片上制备了以BaPbO₃(BPO)为缓冲层的Pb(Zr_0.52,Ti_0.48)Nb_0.04O₃ (Nb掺杂PZT, PZTN)薄膜.通过调整BPO层厚度,为该PZTN薄膜引入了不同的张应力.当BPO层厚度分别为68 nm和135 nm时,PZTN薄膜呈现随机取向,采用2θ-s 关键词： PZT 准同形相界 掠射扫描方式 结构精修     

Four-wave mixing spectroscopy of aqueous suspensions of single-wall carbon nanotubes in the ranges of 0.1–10 and 100–250 cm<Superscript>−1</Superscript>

Distinctive optical properties of single-wall carbon nanotubes (SWNT) are highly sensitive to variations in the environment. Here, we have studied SWNT in aqueous suspensions at a low (less than 0.1 μg ml⁻¹) concentration by four-wave mixing (FWM) spectroscopy in the spectral bands of 0.1 to 10 cm⁻¹ (≈300 GHz) and 100 to 250 cm⁻¹ (3 to 7.5 THz). We directly investigated the hydration layers around SWNT. A comparison of the FWM spectra of an SWNT aqueous suspension and Milli-Q water shows a considerable increase in the intensity of low-frequency Raman modes, which are attributed to the rotational transitions of H₂O₂ and H₂O molecules. We explain the observed phenomenon by the hydrogen peroxide production and formation of a low-density depletion layer at the water-nanotube interface. We have observed several SWNT radial breathing modes ω _RBM =118.5, 164.7, and 233.5 cm⁻¹ in an SWNT aqueous suspension and estimated the corresponding SWNT diameters as ≈2.0, 1.5, and 1 nm.     

Raman spectroscopic study of the tellurite minerals: graemite CuTeO3·H2O and teineite CuTeO3·2H2O

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO₃), (b) A(XO₃)·xH₂O, (c) A₂(XO₃)₃·xH₂O, (d) A₂(X₂O₅) and (e) A(X₃O₈). Raman spectroscopy has been used to study the tellurite minerals teineite and graemite; both contain water as an essential element of their stability. The tellurite ion should show a maximum of six bands. The free tellurite ion will have C_3v symmetry and four modes, 2A₁ and 2 E. Raman bands for teineite at 739 and 778 cm⁻¹ and for graemite at 768 and 793 cm⁻¹ are assigned to the ν₁ (TeO₃)²⁻ symmetric stretching mode while bands at 667 and 701 cm⁻¹ for teineite and 676 and 708 cm⁻¹ for graemite are attributed to the ν₃ (TeO₃)²⁻ antisymmetric stretching mode. The intense Raman band at 509 cm⁻¹ for both teineite and graemite is assigned to the water librational mode. Raman bands for teineite at 318 and 347 cm⁻¹ are assigned to the (TeO₃)²⁻ν₂(A₁) bending mode and the two bands for teineite at 384 and 458 cm⁻¹ may be assigned to the (TeO₃)²⁻ν₄(E) bending mode. Prominent Raman bands, observed at 2286, 2854, 3040 and 3495 cm⁻¹, are attributed to OH stretching vibrations. The values for these OH stretching vibrations provide hydrogen bond distances of 2.550(6) Å (2341 cm⁻¹), 2.610(3) Å (2796 cm⁻¹) and 2.623(2) Å (2870 cm⁻¹) which are comparatively short for secondary minerals. Copyright © 2008 John Wiley & Sons, Ltd.     

Rovibrational constants for the ground state and ν8 = 1 state of ethylene-d3 (C2HD3) by high-resolution FTIR spectroscopy

The Fourier transform infrared (FTIR) spectrum of the ν₈ fundamental band of ethylene-d₃ (C₂HD₃) was recorded with a unapodized resolution of 0.0063 cm⁻¹ in the wavenumber region of 840–980 cm⁻¹. By assigning and fitting a total of 738 infrared transitions using a Watson’s A-reduced Hamiltonian in the I^r representation, rovibrational constants for the upper state (ν₈ = 1) up to all five quartic centrifugal distortion terms were derived for the first time. The root-mean-square (rms) deviation of the fit was 0.00076 cm⁻¹. The ground state rovibrational constants of C₂HD₃ were also determined for the first time by a fit of 450 combination-differences from the present infrared measurements, with rms deviation of 0.00075 cm⁻¹. Local frequency perturbations were not detected in the C-type ν₈ band of C₂HD₃ which is centred at 918.73199 ± 0.00007 cm⁻¹.     

High-resolution FTIR spectroscopy of the Coriolis interacting nu3 and nu9 fundamentals of methylene fluoride-d2

The Fourier transform infrared spectrum of the υ ₃ and υ ₉ bands of methylene fluoride-d ₂ (CD₂F₂) has been recorded with an unapodized resolution of 0.0024cm^-1 in the frequency range 970-1080cm^-1. These two bands with band centres approximately 26 cm^-1 apart were mutually coupled by Coriolis interactions. By fitting a total of 1639 infrared transitions of both υ ₃ and υ ₉ with a standard deviation of 0.00084cm^-1 S/S using a Watson's A-reduced Hamiltonian in the I ^r representation with the inclusion of a first order c-type Coriolis resonance term, two sets of rovibrational constants for υ ₃ = 1 and υ ₉ = 1 states were derived. The υ ₃ band is B-type while the υ9 band is A-type with band centres at 1030.1573 ± 0.0003 and 1003.7435 ± 0.0001cm^-1, respectively.     

Excited Even-Symmetry States of Metallocomplexes of Porphin and Its Derivatives

Based on calculations by the CNDO/S method, data on the excited molecular states of even parity of the magnesium complexes of porphin (P), tetraazaporphin (TAP), tetrabenzoporphin (TBP), and phthalocyanine (Phc) are obtained. It is only in MgP that the first excited g-state 1¹ B _2g (29,000 cm^–1) is located 300 cm^–1 higher than the B level (28,700 cm^–1). In MgTBP, the two states 1¹ B _1g (24,700 cm^–1) and 1¹ B _2g (25,500 cm^–1) are found to be near the B level (27,500 cm^–1), while the states 1¹ B _2g (25,500 cm^–1) in MgTAP and 1¹ B _2g (21,000 cm^–1) and 1¹ B _1g (23,100 cm^–1) in MgPhc are located much lower than the B level; the energy of the latter is 31,900 and 32,400 cm^–1 in MgTAP and MgPhc respectively. The results obtained are in good agreement with experimental data on two-photon absorption: in the zinc complex of tetraphenylporphin (TPhP), the g-state is detected in the region of the B level, while in ZnPhc, two bands at 20,400 and 21,700 cm^–1 show up.     

Optical management in high‐efficiency thin‐film silicon micromorph solar cells with a silicon oxide based intermediate reflector

In the effort to increase the stable efficiency of thin film silicon micromorph solar cells, a silicon oxide based intermediate reflector (SOIR) layer is deposited in situ between the component cells of the tandem device. The effectiveness of the SOIR layer in increasing the photo‐carrier generation in the a‐Si:H top absorber is compared for p–i–n devices deposited on different rough, highly transparent, front ZnO layers. High haze and low doping level for the front ZnO strongly enhance the current density (J_sc) in the μc‐Si:H bottom cell whereas J_sc in the top cell is influenced by the angular distribution of the transmitted light and by the reflectivity of the SOIR related to different surface roughness. A total J_sc of 26.8 mA/cm² and an initial conversion efficiency of 12.6% are achieved for 1.2 cm² cells with top and bottom cell thicknesses of 300 nm and 3 μm, and without any anti‐reflective coating on the glass. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Absolute line wavenumbers in the near infrared: 12C2H2 and 12C16O2

40 absolute line wavenumbers in the 3v ₃ band of ¹²C¹⁶O₂ between 6927 cm^?1 and 6989 cm^?1 and 626 absolute line wavenumbers in the near infrared absorption spectrum of ¹²C₂H₂ between 7060 cm^?1 and 9900 cm^?1 have been measured using high resolution Fourier transform spectroscopy. The calibration of the CO₂ line wavenumbers relied on heterodyne frequencies available in the v ₁ + v ₃ band of ¹²C₂H₂ near 6556 cm^?1. The absolute uncertainty of the calibrated CO₂ line wavenumbers is estimated to 0.000 08 cm^?1. The acetylene spectra were calibrated using heterodyne frequencies available in the 2—0 band of ¹²C¹⁶O and the line wavenumbers obtained in the 3v ₃ band of ¹²C¹⁶O₂. The absolute uncertainty of the calibrated acetylene line wavenumbers is estimated to range from 0.0003 cm^?1 to 0.006 cm^?1 for strong to very weak isolated lines. Comparison with absolute line wavenumbers obtained independently at JPL in the 3v ₃ band of ¹²C₂H₂ near 9649 cm^?1, calibrated using absolute wavenumbers available in the 2—0 and 3—0 (near 6350 cm^?1) bands of ¹²C¹⁶O, shows very good agreement. Also, the vibration—rotation constants for the observed upper vibrational states of ¹²C₂H₂ were determined, but without accounting for the perturbations affecting these states.     

基态S和D原子的低能弹性碰撞及SD(X2Π)自由基的准确相互作用势与分子常数

使用Gaussian03程序包提供的CCSD（T）理论及Duning等的相关一致基cc-pVnZ和aug-cc-pVnZ （n=2, 3, 4, 5）, 对SD（X²Π）自由基的平衡核间距、谐振频率及相互作用势进行了计算, 并拟合出了相应的光谱常数. 在CCSD（T）/aug-cc-pV5Z理论水平下, 光谱常数D₀, D_e, R 关键词： 弹性碰撞 总截面 光谱常数 分子常数     

High-resolution FTIR spectroscopy of the v11 and v2 + v7 bands of ethylene-d4

The Fourier transform infrared spectrum of the v₁₁ band of ethylene-d₄ (C₂D₄) has been recorded with an unapodized resolution of 0.006 cm^?1 in the frequency range 2150 to 2250cm^?1. The v₁₁ band, with a band centre of about 2201 cm^?1, was found to be perturbed by the nearby v₂ + v₇ band centred at about 2235 cm^?1 by a b-type Coriolis interaction. By fitting a total of 772 infrared transitions of v₁₁ using a Watson's A-reduced Hamiltonian in the I^r representation with the inclusion of b-type Coriolis interaction term, two sets of constants, up to quartic distortion constants for the v₁₁ = 1 state, and principal rotational constants for the v₂ + v₇ = 1 dark state, were derived. The inertia defect of the v₁₁ state was found to be 0.0693 ± 0.0004u Ų.     

Selective laser induced melting of ultrathin nanoporous silicon layers

Short laser pulses (wavelength 337 nm, duration time 0.5 ns) are used for thermal processing of ultra thin nanoporous silicon layers (UPSL) prepared electrochemically on n- and p-type Si(1 1 1) in aqueous NH₄F solution. The theoretical threshold for melting (W _m ) of UPSL is about 0.01 J/cm². This is about one order of magnitude belowW _m of crystalline silicon. A selective laser induced melting regime can be realized for which an UPSL is practically completely molten on the top of an unmolten crystalline silicon substrate. Investigations with scanning and high resolution transmission electron microscopy show the formation of crystalline silicon spheres with diameters in the range of some of ten nm in this regime.     

Higher ro-vibrational levels of H2O deduced from high resolution oxygen-hydrogen flame spectra between 6200 and 9100 cm-1

The spectra of hydrogen-oxygen and acetylene-oxygen flames have been recorded on a Fourier transform spectrometer in the region 6200–9100 cm^-1 with a resolution of 0·015 cm^-1. In this region, we have performed a detailed analysis of the 2v ₂ + v ₃, v ₁ + v ₃, v ₁ + v ₂ + v ₃ - v ₂ and v ₁ + v ₂ + v ₃ bands. A primary motive for this study was to obtain higher rotational energy levels for the (021), (101) and (111) vibrational states. Moreover an extensive set of rotational levels of the (010) vibrational state has been deduced from the combined study of hot bands involving the (011), (021) and (111) vibrational states. A room-temperature absorption spectrum of water recorded on a Fourier transform spectrometer in the region 1750–2300 cm^-1 (resolution 0·005 cm^-1) has also been used to confirm the analysis.     

Vibrational properties of graphene and graphene layers

The phonon dispersions of graphene and graphene layers are theoretically investigated within fifth‐nearest‐neighbor force‐constant approach. Based on their symmetry groups, the number of Raman‐ and infrared‐active modes at the Γ point is given. Interatomic force constants are recalculated by fitting them to experimental phonon energy dispersion curves. Wavenumbers of optically active modes are presented as a function of number of layers (n). Our calculated results reproduce well the experimental data of G peak for graphene (1587 cm⁻¹) and graphite (1581.6 cm⁻¹) and clearly give the relation that ω_G = 1581.6 + 11/(1 + n^1.6). Copyright © 2009 John Wiley & Sons, Ltd.     

The effects of GaN capping layer thickness on two-dimensional electron mobility in GaN/AlGaN/GaN heterostructures

In this paper we present a study of the effect of GaN capping layer thickness on the two-dimensional (2D)-electron mobility and the two-dimensional electron gas (2DEG) sheet density which is formed near the AlGaN barrier/buffer GaN layer. This study is undertaken using a fully numerical calculation for GaN/Al_xGa_1−xN/GaN heterostructures with different Al mole fraction in the Al_xGa_1−xN barrier, and for various values of barrier layer thickness. The results of our analysis clearly indicate that increasing the GaN capping layer thickness leads to a decrease in the 2DEG density. Furthermore, it is found that the room-temperature 2D-electron mobility reaches a maximum value of approximately 1.8×10³ cm² /Vs⁻¹ for GaN capping layer thickness grater than 100 Å with an Al_0.32Ga_0.68N barrier layer of 200 Å thick. In contrast, for same structure, the 2DEG density decreases monotonically with GaN capping layer thickness, and eventually saturates at approximately 6×10¹² cm⁻² for capping layer thickness greater than 500 Å. A comparison between our calculated results with published experimental data is shown to be in good agreement for GaN capping layers up to 500 Å thickness.     

Theoretical investigations of spectroscopic parameters and molecular constants for electronic ground state of Cl2 and its isotopes

The potential energy curve of the Cl 2(X1Σg+) is investigated by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with the largest correlation-consistent basis set, aug-cc-pV6Z, in the valence range. The theoretical spectroscopic parameters and the molecular constants of three isotopes, 35Cl2, 35Cl37Cl and 37Cl2, are studied. For the 35Cl2 (X1Σg+), the values of D0 , De , Re , ωe , ωeχe , αe and Be are obtained to be 2.3921 eV, 2.4264 eV, 0.19939 nm, 555.13 cm-1 , 2.6772 cm-1 , 0.001481 cm-1 and 0.24225 cm-1 , respectively. For the 35Cl37Cl(X1Σg+), the values of D0 , De , Re , ωe , ωeχe , αe and Be are calculated to be 2.3918 eV, 2.4257 eV, 0.19939 nm, 547.68 cm-1 , 2.6234 cm-1 , 0.00140 cm-1 and 0.23572 cm-1 , respectively. And for the 37C2 (X1Σg+), the values of D0 , De , Re , ωe , ωeχe , αe and Be are obtained to be 2.3923 eV, 2.4257 eV, 0.19939 nm, 540.06 cm-1 , 2.5556 cm-1 , 0.00139 cm-1 and 0.22919 cm-1 , respectively. These spectroscopic results are in good agreement with the available experimental data. With the potential of Cl2 molecule determined at the MRCI/aug-cc-pV6Z level of theory, the total of 59 vibrational states is predicted for each isotope when the rotational quantum number J equals zero (J = 0). The theoretical vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined when J = 0, which are in excellent accordance with the available experimental findings.     

High‐resolution stimulated Raman spectroscopy and analysis of the ν1/ν5 (C–H) stretching dyad of C2H4

The high‐resolution stimulated Raman spectra of the ν₁/ν₅ C–H stretching bands of C₂H₄ have been recorded and analyzed by means of the tensorial formalism developed in Dijon for X₂Y₄ asymmetric‐top molecules. A total of 689 lines (428 for ν₅ and 261 for ν₁) were assigned and fitted as a dyad including Coriolis coupling constants. We obtained a global root mean square deviation of 4.39 × 10^{− 3} cm^{− 1} (4.61 × 10^{− 3} cm^{− 1} for ν₁, 4.25 × 10^{− 3} cm^{− 1} for ν₅). The nearby 2ν₂ band, extrapolated from ν₂, was included in the analysis. However, no interaction parameter involving it could be fitted. The analysis is quite satisfactory, although some parts of ν₅ are not very well reproduced, probably indicating some yet unidentified resonances. This region is indeed quite dense, with many interacting dark states that cannot be included at present. Copyright © 2012 John Wiley & Sons, Ltd.