The ground-state rotational constants of germane

The ground-state rotational constants B₀, D₀, and H₀ have been determined for GeH₄ from the analysis of ground-state combination differences in the infrared spectra of isotopically enriched ⁷⁰GeH₄, ⁷²GeH₄, and ⁷⁴GeH₄. The spectra were recorded at 0.06-cm^?1 resolution and about 0.005-cm^?1 precision for unblended lines. Suitable combination differences were found in both the ν₂ and the ν₄ infrared bands. The ground-state constants were assumed to be invariant to isotopic substitution at Ge, and the tensor distortion constants were held fixed at their microwave values. The results obtained are: B₀ = 2.69587 ± 0.00007 cm^?1, D₀ = (3.34 ± 0.03) × 10^?5 cm^?1, H₀ = (1.3 ± 0.5) × 10^?9 cm^?1.     

Interaction of germanium with silicon dioxide

The interaction of germanium (Ge) adatoms with SiO₂ (silica) plays an important role in selective, heteroepitaxial growth of Ge(100) through windows created in silica on Si(100) and in the selective growth of Ge nanoparticles on hafnia, located at the bottom of pores etched through silica. Both processes rely on the inability of Ge to accumulate on silica. In hot wire chemical vapor deposition of Ge nanoparticles from GeH₄, etching of the silica has been invoked as one path to prevent accumulation of Ge on silica; whereas dense silica is not etched when Ge atoms are incident on the surface in molecular beam processes. Surface studies were conducted to determine the nature of oxidized Ge on SiO₂, to reconcile the etching claim with GeH₄, and to look for the additional etching product that must accompany GeO, namely SiO. Etching of silica is not found with GeH₄ or GeH_x fragments. A more complete examination of the Ge isotopes reveals instead the m/e 90 signal, previously attributed to GeO, originates from interactions between iron oxide impurities in the molybdenum holder, and hydrogen and GeH_x fragments. Coating the Mo with gold eliminates m/e 90 from Ge TPD spectra. The high temperature m/e 74 and m/e 2 peaks observed from 800 to 900 K are attributed to GeH_x decomposition to Ge and H followed by their desorption, while the appearance of GeO_x is attributed to possible reactions between GeH_x species with hydroxyl groups and/or oxidation of Ge clusters by background oxidants.     

High resolution FTIR spectroscopy of CH2DF: analysis of the v 3 and v 4 interacting bands

The high resolution (0.004cm^?1) Fourier transform infrared spectrum of the monodeuterated form of methyl fluoride, CH₂DF, has been recorded and analysed in the v ₃ and v ₄ band region around 1420cm^?1. Both bands, coming from A′ symmetry vibrations, have a/b hybrid character, although in v ₃ the b-type component prevails over the a-type. The rotational structure has been analysed using a dyad model including c-type Coriolis coupling and high order vibrational resonance between these states. Accurate upper state molecular parameters and interaction terms have been obtained by fitting about 3270 assigned transitions to Watson's A-reduced Hamiltonian in the I^r representation. In addition, from a simultaneous fit of ground state combination differences coming from this analysis and 42 literature microwave transitions, an improved and more complete set of ground state constants, including three new sextic centrifugal distortion terms (Φ_JK, Φ_KJ and Φ_K), has been derived.     

Vibrational spectra of monoisotopic SiH<Subscript>4</Subscript> and GeH<Subscript>4</Subscript> in low-temperature matrices

IR absorption spectra of monoisotopic ²⁸SiH₄ and ⁷⁶GeH₄ are studied in Ar and N₂ matrices at 10 K. It is shown that the absorption spectra of silane and germane are similar in the regions of the stretching ν₃ and bending ν₄ vibrations. Four groups of bands can be separated out in the spectra of each molecule: (1) narrow bands characteristic of the matrix isolation studies, (2) broad bands, (3) diffuse absorption with a large value of the spectral moment M ₂^* the intensity of which increases upon annealing, and (4) bands of dimers the intensity of which increases quadratically with concentration. The spectra of ²⁸SiH₄ and ⁷⁶GeH₄ in nitrogen matrices contain a triplet in the stretching region and a doublet in the bending region, which is explained by the change in the molecular symmetry from T _d to C _3V on passage from the gas phase to solid nitrogen.     

Microwave and low-frequency vibrational spectra of bullvalene

The microwave spectrum of bullvalene has been investigated in the region 18–40 GHz. In addition to transitions in the ground vibrational state, transitions arising from five excited vibrational states below 600 cm⁻¹ have also been observed. A combination of microwave intensity measurements and infrared and Raman data has been utilized to assign these vibrations. Three of the vibrations are E-type modes at 241, 355, and 588 cm⁻¹. One is an A₁-type mode at 445 cm⁻¹, and another is an A₂-type at 266 cm⁻¹. The microwave spectrum indicates the presence of a first-order Coriolis interaction for the E modes at 241 and 588 cm⁻¹. The first-order Coriolis coupling constant q = 0.557 MHz for the 241 cm⁻¹ vibration. The spectral results are consistent with C_3v symmetry for bullvalene.     

Mechanism of GeH4 dissociation on Si(1 1 1)-(7 × 7)

Results of an STM study of dissociative GeH₄ adsorption on Si(1 1 1)-(7 × 7) at 300 K show that GeH₄ adsorbs under scission of two Ge-H bonds according to GeH₄(g) + 4db → GeH₂(ad) + 2H(ad). GeH₂ binds to two adatom dangling bonds in a bridged configuration, while the two released hydrogen atoms saturate two additional dangling bonds. The GeH₄ sticking coefficient under these conditions is 1.2 × 10⁻⁶, one order of magnitude smaller than for SiH₄.     

The ν2 Raman band of CD4

The rather weak ν₂ Raman band of CD₄ has been recorded with a resolution of about 0·45 cm^-1. The data have been analysed in two ways: (i) treating ν₂ as an isolated band, and (ii) analysing the ν₂ and ν₄ bands together by a simultaneous diagonalization of the v ₂=1 and v ₄=1 states coupled by the Bζ_2,4 Coriolis interaction term. Although the former treatment is satisfactory for low J values, the explicit inclusion of the Coriolis coupling is necessary to reproduce the observed spectrum for all J values.     

High resolution infrared synchrotron study of CH2D81Br: ground state constants and analysis of the ν5, ν6 and ν9 fundamentals

The high resolution infrared absorption spectrum of CH₂D⁸¹Br has been recorded by Fourier transform spectroscopy in the range 550–1075?cm^?1, with an unapodized resolution of 0.0025?cm^?1, employing a synchrotron radiation source. This spectral region is characterized by the ν₆ (593.872?cm^?1), ν₅ (768.710?cm^?1) and ν₉ (930.295?cm^?1) fundamental bands. The ground state constants up to sextic centrifugal distortion terms have been obtained for the first time by ground-state combination differences from the three bands and subsequently employed for the evaluation of the excited state parameters. Watson's A-reduced Hamiltonian in the I^r representation has been used in the calculations. The ν ₆?=?1 level is essentially free from perturbation whereas the ν ₅?=?1 and ν ₉?=?1 states are mutually interacting through a-type Coriolis coupling. Accurate spectroscopic parameters of the three excited vibrational states and a high-order coupling constant which takes into account the interaction between ν₅ and ν₉ have been determined.     

High-resolution infrared spectroscopy of CH2D79Br: ro-vibrational analysis of the ν4 and ν8 fundamental bands

The high-resolution Fourier transform infrared spectrum of CH₂D⁷⁹Br has been recorded and analysed in the region of the ν₄ and ν₈ fundamentals located in the range 1125?1360 cm^?1. The strong ν₄ band, centred at 1225 cm^?1, shows an a/b-hybrid structure with predominant a-type character, whereas ν₈, at 1253 cm^?1, generates a c-type contour comparable in intensity to the b-type component of ν₄. The upper states of these fundamentals are coupled through a- and b-type Coriolis resonances; further complications in this band system arise from perturbations due to the ν₆ = 2 (1183 cm^?1) and ν₅ = ν₆ = 1 (1359 cm^?1) dark states. The former interacts with ν₈ = 1 by b-type Coriolis coupling, whereas the latter perturbs the ν₄ = 1 and ν₈ = 1 levels by anharmonic and a-type Coriolis resonances, respectively. Accurate upper state parameters and interaction terms have been determined for the tetrad system ν₄/ν₈/2ν₆/ν₅+ν₆ by also including in the dataset the assigned transitions of the 2ν₆?ν₆ and ν₅+ν₆?ν₆ hot bands obtained from previous analysis.     

The millimeterwave spectrum of germyl fluoride: Determination and comparison of the effective, substitution, and equilibrium structures

The ground state rotational spectrum of germyl fluoride was measured up to 1273 GHz (J ≤ 63). The rotational constants and quartic and sextic centrifugal distortion constants have been determined accurately for five isotopic species in natural abundance (^{70/72/73/74/76}Ge). The high accuracy of the rotational constants of these five isotopomers allowed us to study the mass dependence of the substitution coordinate of Ge. Equilibrium rotational constants of ⁷⁴GeH₃F were deduced with the help of the axial rotational constant and the rotation-vibration interaction constants determined by high resolution infrared spectroscopy. The r₀, r_,I, and r_e structures of GeH₃F were determined.     

Infrared absorptions and band widths of dilute solutions of CF3H in liquid Ar,N2, and Xe

The spectra of fluoroform (CF₃H) in the solvents Ar, N₂, and Xe have been obtained in the fundamental region (400–4000cm^?1) using a low temperature cryostat and a Fourier transform infrared spectrophotometer. Ab initio calculations at the HF/6-31G? level have been performed to obtain the calculated vibrational frequencies of the isolated CF₃H molecule and CF₃H in the presence of the solvents (Ar, N₂, and Xe). Comparison of the frequency shifts of CF₂H in solution with respect to the gas phase frequencies is made for the experimental and theoretical results. Lorentzian functions were used to fit the bands and obtain the wavenumber at the peak absorbance and the vibrational band widths. An analysis of the dynamics of relaxation has been made based on the infrared time correlation functions for three of the fundamental modes (ν₁, ν₃, and ν₄). Bandwidths, band moments, and relaxation times were obtained by appropriate fitting of the experimental correlation functions to theoretical models. In liquid argon, the temperature dependence of the second moment (M ₂) indicates that rotational relaxation explains the bandwidth of the ν₃ mode. For the ν₄ mode, the temperature dependence of M ₂ can be attributed to rotational relaxation if it is corrected with a Coriolis coupling term. The bandwidths of the ν₁ mode do not follow the rotational relaxation model, and probably vibrational relaxation is the dominant mechanism.     

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.     

Simultaneous analysis of the ν2 and ν4 bands of methane

Vibration-rotation spectra of the ν₂ and ν₄ bands of CH₄ have been analysed by a simultaneous diagonalization of the hamiltonian matrices for the v ₂=1 and v ₄=1 states coupled by the Bξ_2,4 Coriolis interaction term. The effective hamiltonians used extend to sextic centrifugal distortion terms. The results are a significant improvement on any previous analysis; 438 assigned transitions up to J′=16 have been fitted with an overall standard deviation of 0·016 cm^-1. The method used is compared with an alternative theoretical approach given by Berger.     

High-Resolution Infrared Spectrum of H3SiI in the ν1/ν4Region near 2200 cm

The Fourier transform infrared spectrum of H₃SiI has been recorded in the ν₁/ν₄region from 2075 to 2315 cm⁻¹at an optical resolution of 2.3 × 10⁻³cm⁻¹. The ν₁/ν₄fundamental bands and the (ν₁+ ν₃) − ν₃/(ν₄+ ν₃) − ν₃hot bands have been rotationally investigated. Numerous local perturbations have been observed in the ν₁and ν₄bands and in the hot bands. Without the lines involved in perturbations, more than 2900 transitions of the ν₁/ν₄bands were used to determine the band origins and the vibration–rotation parameters of the ν₁= 1 and νv₄= 1 states. A least-squares fit of 766 apparently unperturbed transitions of the hot bands gave the parameters of the ν₁= ν₃= 1 and ν₄= ν₃= 1 states. Thel(2, 2) resonance in ν₄and theA₁–E Coriolis coupling between ν₁and ν₄have been investigated. Most of the local perturbations have been studied individually using a simple model by which the main perturber for each resonance was identified.     

High resolution FTIR spectra of AsD3 in the 20-1000 cm−1 region. The ground, 98, v2 = 1 and v4 = 1 states

The pure rotational spectrum of the near-spherical oblate symmetric top AsD₃ has been recorded in the 20–120cm^?′ region with a resolution of 2.3 × 10^?3 m^?1 employing an FT interferometer. Rotational transitions with 5 ? J ? 29 and 0 ? X ? 25 of the ground state (GS) and the v₂ = 1 and v₄ = 1 excited states have been assigned. Splittings were observed for the GS, 98, K = 3 and 6 levels, the K = 3 levels of v₂ and the kl = ?2, 1, 4 and 7 levels of v₄. Furthermore the x,y Coriolis coupled v₂ and v₄ bands, v ⁰ ₂ = 654.4149cm^?1, and v ⁰ ₄ = 714.3399 cm^?1, have been examined with a resolution of 2.4 × 10^?3 cm^?1, and ca. 2500 allowed and 336 ‘forbidden’ lines with J′_max = 31 and K′_max = 28 have been assigned. Appropriately weighted GS data comprising FIR lines, allowed and ‘forbidden’ (up to ΔK = ±6) GS combination differences, mmw data, and ΔJ = 0, ΔK = ±1 distortion moment transitions were fitted together, and GS parameters complete through H parameters have been determined. Two different reductions of the Hamiltonian, either with ΔK = ±6 (h₃) or ΔK = ±3 (ε) off-diagonal elements, have been employed. Equivalence of these reductions up to J = 22 was established while for J > 22 the ε reduction is superior. The v₂ and v₄ data have been fitted with two equivalent models based on different reductions of the rovibrational Hamiltonian. In addition to the dominating x,y Coriolis resonance, ζ ^y ₂₄ 0.520, Δ(k ? l) = ±3 and ±6 interactions are important and were accounted for by the models. The transition moment ratio |M₄: M₂| =0.75 has been determined, with a positive sign of the product M ₂ζ ^y ₂₄ M ₄. An improved r₀ structure, r₀(AsD) = 1.51753 Å and α₀(DAsD) = 92.000°, has been determined.     

6H碳化硅衬底上硅碳锗薄膜的生长特性研究

采用低压热壁化学气相沉积法,在6H-SiC衬底(0001)面上生长了不同温度(1100—1250℃),不同GeH₄流量比(6.3%—25%)的SiCGe薄膜样品,研究了SiCGe薄膜的表面形貌、生长特性以及样品中Ge组分含量的变化. 扫描电镜测试结果表明,SiCGe薄膜在低温下倾向于岛状生长模式,随着生长温度提高,岛状生长逐渐过渡到层状生长模式,同时伴有岛形状和密度的变化. X射线光电子能谱测试得出SiCGe样品中的Ge含量约为0.15％—0.62％,在其他参数不变的情况下,样品的G 关键词： 碳化硅 化学气相沉积 反相边界 岛状生长     

The millimeter-wave spectra of germyl fluoride in excited vibrational states

Millimeter-wave spectra of GeH₃F in the v₃ = 1, v₆ = 1, v₂ = 1, and v₅ = 1 excited states have been recorded. Strong Coriolis resonance between the v₂ = 1 and v₅ = 1 states results in a highly perturbed spectrum which shows no obvious resemblance to the normal symmetric top excited state pattern. A similar, but not so strong coupling, exists between the v₃ = 1 and v₆ = 1 states. These spectra are analyzed by setting up the Coriolis coupled Hamiltonian matrices for these states. It has been shown that the apparently anomalous distortion constants of these states are due to the Coriolis coupling and the distortion parameters obtained with the model presented are, as expected, close to the ground state values.     

High resolution IR spectrum of the ν8 band of CH2DF: analysis of the interactions with the near vibrational levels

The IR spectrum of the ν₈ band of monodeutero methyl fluoride has been recorded with a resolution of 0.004 cm^?1 using a Fourier transform spectrometer. The ν₈ vibration, of A′′ symmetry species, gives rise to a pure c-type envelope centred at 1298.58 cm^?1, resembling a perpendicular band of a prolate symmetric rotor. From the spectral analysis it has been found that ν₈ is coupled with ν₄ for the low K_a sublevels while for the higher ones other vibrational states, directly or indirectly, are also interacting. For satisfactory reproduction of the rovibrational data of ν₈, the Watson's Hamiltonian in the I^r representation has been implemented with interaction parameters, which included first- and second-order a-, b-type and c-type Coriolis couplings with ν₄ and ν₉, respectively. Being these states also interacting with other levels, the effective spectroscopic parameters of the analysed band up to fourth order have been obtained from a data set formed by the six fundamentals located below 1500 cm^?1.     

High-resolution Fourier-transform infrared spectroscopy of the ν1 and ν8 fundamental bands of sulphur tetrafluoride (SF4)

The vibration-rotation spectra of the ν₁ and ν₈ fundamental bands of ³²SF₄ have been observed using Fourier-transform infrared spectroscopy. The band centre of the c-type ν₁ symmetric sulphur-equatorial-fluorine stretching vibration was observed at 891.6 cm^?1 and that for the b-type ν₈ asymmetric sulphur-equatorial-fluorine stretching vibration at 864.6 cm^?1. In total, 2044 rovibrational transitions have been assigned. Analysis of the spectra showed that the rotational states of the ν₁ = 1 and ν₈ = 1 upper vibrational levels are coupled by an a-type Coriolis interaction. This coupling has been treated both using perturbation theory and by the explicit inclusion of an appropriate Hamiltonian matrix element in a combined fit of the data for both bands. Spectroscopic parameters have been determined for the ground, ν₁ = 1 and ν₈ = 1 vibrational levels. Weaker transitions resulting from difference bands and the fundamental bands of the ³⁴SF₄ isotopomer have been identified but could not be assigned, because of the density of lines in the room-temperature spectrum. The possibility that discrepancies between the observed and predicted spectra of the ν₁ fundamental may result from either a Coriolis interaction with the states of another vibrational level, or the effects of intramolecular exchange of axial and equatorial fluorine atoms is considered. The discussion is supported by theoretical calculations which show that the likely path for intramolecular exchange is via a C _4v transition state.     

Rotation–torsion analysis of the Si2H6 infrared fundamental ν9, perturbed by excited torsional levels of the vibrational ground state

The lowest infrared active perpendicular fundamental ν₉ of disilane has been analysed on a Fourier transform spectrum between 320 and 430?cm^?1, at the spectral resolution of 0.0012?cm^?1. The rotation–torsion structure of this band is affected by x,y Coriolis interactions with excited torsional levels of the vibrational ground state, correlating with components of 3ν₄ and 4ν₄ in the high barrier limit. The interaction of ν₉ and 4ν₄, forbidden in the D_3d symmetry limit, is allowed between components of E torsional symmetry under the G₃₆(EM) extended molecular group, because of the large amplitude of the internal rotation motion. We could determine the values of the main vibration–rotation–torsion parameters of ν₉, interaction parameters, and the vibrational wavenumbers of the four torsional components of 3ν₄ and of the E_3d component of 4ν₄. The intrinsic torsional splitting of ν₉ is found to be smaller than in the ground vibrational state by 0.0066?cm^?1, in good agreement with our theoretical predictions. The possibility of observing the effects of D_3d-forbidden interactions in the spectra of ethane-like molecules is also discussed.