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We report on the growth of Sn-catalyzed GeSn nanowires (NWs) having a GeSn core and a c-Ge shell in the presence of germane plasma at substrate temperatures (TS) below the GeSn eutectic temperature (TE), containing an exceptional Sn concentration of 30 at. % in their core. The differences between the NWs produced at TS above and below TE of the GeSn alloy are highlighted. Two types of NW growth process are identified: the previously reported in-plane solid–liquid–solid (IPSLS) process for TS ≥ TE and a plasma-assisted IPSLS (PA-IPSLS) method taking place at TS < TE; the crucial role of plasma in providing the energy necessary to melt the Sn catalyst at substrate temperatures lower than TE is discussed. The thermal activation window for each method is determined. The PA-IPSLS process is shown to provide an efficient strategy for the growth of crystalline GeSn NWs with a high Sn incorporation in a growth duration of less than 3 min.

The spectra of germane 72GeH4 enriched up to 99.9% in the sample were recorded with high resolution (0.003 cm − 1 ) at different pressures with the Bruker IFS 125HR Fourier transform spectrometer (Nizhny Novgorod, Russia). The region of 700–4400 cm − 1 , where the Dyad and Pentad are located, was theoretically analyzed. The 9112 transitions belonging to the seven “cold” bands (6761 transitions) of the Dyad and Pentad and to the nine “hot” Dyad–Pentad bands (2351 transitions) were assigned and analyzed with an effective hamiltonian model which takes into account the presence of resonance interactions. The obtained set of 53 fitted parameters reproduces the initial 9112 experimental line positions with a d r m s = 2.44 × 10 − 4 cm − 1 .

The spectra of germane enriched up to 99.9 % of 73GeH4 were recorded with a high resolution (0.003 cm − 1 ) at different pressures with the Bruker IFS 125HR Fourier transform spectrometer (Nizhny Novgorod, Russia) in the region of 650–4400 cm − 1 and analyzed in the Dyad and Pentad region. The 9208 transitions belonging to the seven “cold” bands (6987 transitions) of the Dyad and Pentad and to the nine “hot” Dyad–Pentad bands (2221 transitions) were assigned and theoretically analysed in the frame of the effective Hamiltonian model. The obtained set of 68 fitted parameters reproduces the initial 9208 experimental line positions with the d r m s = 2.82 × 10 − 4 cm − 1 .

The steady-state kinetics of growth of Si1 – xGex layers in one version of hybrid molecular beam epitaxy with a molecular germane source and a sublimating silicon bar has been studied. It has been demonstrated that the processes of capture of hydride molecule radicals by the epitaxial surface and their subsequent decomposition must be taken into account in the analysis of growth kinetics. The comparison of experimental data with the results of kinetic analysis has revealed a close match between them. At low germane pressures \({P_{Ge{H_4}}}\) < 0.5 mTorr, the nature of the growth process is defined exclusively by the specifics of interaction between the molecular beam of Ge monohydride with the growth surface. The influence of the atomic Ge beam from the Si source only manifests at germane pressures exceeding 1 mTorr. Under these conditions, the fluxes of Ge and Si atoms from the sublimating Si source become equal, and the concentration of germyl molecules on the surface reaches saturation. The observed increase in the \({V_{Ge{H_3}}}\) parameter is associated with the activating influence of the flux of silicon atoms from the sublimating source on the decomposition of molecules.

A simplified model of Silicon Germanium Chemical Vapor Deposition is proposed for the determination of Vapor – Solid distributions via any precursor route. The incorporation of the atomic element into the crystal lattice imposes to the chemical precursor the loss of all the ligands. Thus, dichlorosilane, silane, and disilane are discriminated on the basis of the amount of the atomic element brought into the equilibrium, instead of being different chemicals. Experimental trends show the ratio relative to silane is 2 for disilane and about ½ for dichlorosilane. The ratio relative to Si{100} is 0.59 for Si{110} and 0.82 for Si{111} for a growth via dichlorosilane and germane. Furthermore, Silicon Germanium alloy content is controlled by a thermodynamic equilibrium and the theoretical VS distribution is demonstrated for a growth via silane and germane. VS distribution of any chemistry onto any substrate orientation can therefore be estimated with the application of a straightforward corrective coefficient to a reference silane and germane chemistry.

This work investigates the crystal quality of SiGe layers grown at low temperatures using trisilane, and germane precursors. The crystal quality sensitivity was monitored for hydrogen chloride and/or minor oxygen amount during SiGe epitaxy or at the interface of SiGe/Si layers. The quality of the epi-layers was examined by quantifying noise parameter, K 1/f obtained from the power spectral density vs. 1/f curves. The results indicate that while it is difficult to detect small defect densities in SiGe layers by physical material characterization, the noise measurement could reveal the effects of oxygen contamination as low as 0.16 mPa inside and in the interface of the layers.

We have studied the very low temperature epitaxy of pure Ge and of Ge-rich SiGe alloys in a 200 mm industrial reduced pressure chemical vapour deposition tool. We have, first of all, benchmarked germane (GeH 4 ) and digermane (Ge 2 H 6 ) for the growth of pure Ge. Used Ge 2 H 6 instead of GeH 4 enabled us to dramatically increase the Ge growth rate at temperatures 425 °C and lower (5.6 nm min −1 compared to 0.14 nm min −1 at 350 °C with a Ge 2 H 6 mass-flow one fourth that of GeH 4 ). We have also evaluated at 400 °C, 100 Torr, the impact of the GeH 4 or Ge 2 H 6 mass-flow on the Ge growth rate. For a given Ge atomic flow, the higher surface reactivity of digermane yielded roughly five times higher growth rates than with germane. We have then combined digermane with disilane (Si 2 H 6 ) or dichlorosilane (SiH 2 Cl 2 ) in order to study the GeSi growth kinetics at 475 °C, 100 Torr. While the SiH 2 Cl 2 mass-flow did not have any clear influence on the GeSi growth rate (with a 14 nm min −1 mean value, then), a Si 2 H 6 mass-flow increase resulted in a slight GeSi growth rate increase (from 11 nm min −1 up to 14 nm min −1 ). Significantly higher Ge concentrations were otherwise accessed with dichlorosilane than with disilane, in the 77–82% range compared to the 39–53% range, respectively.

In CEA-LETI, GeSn/SiGeSn stacks are typically grown at 100 Torr with Ge2H6, Si2H6 and SnCl4 and temperatures in the 301°C-363°C range. Ge2H6 has however a reputation of being unstable for high concentrations (10% in H2). The short shelf time can be adressed by switching over to lower concentrations and regularly changing bottles, which is complex as Ge2H6 is costly and complicated to order. One solution could be to switch from digermane to germane, which was shown by several R&D institutes to yield high quality GeSn layers. The epitaxy tools used, then, were capable of Atmospheric Pressure CVD (i. e. @ 760 Torr), while we have Reduced Pressure CVD chambers that can operate only up to a few hundreds of Torr. We have thus investigated the growth of tens of nm thick GeSn layers on 2.5 µm thick Ge Strain-Relaxed Buffers, themselves on Si(001). First GeSn growth trials at 349°C, 100 Torr with the same GeH4 flow than Ge2H6 did not yield any peaks in X-Ray Diffraction (XRD). Changing the Mass-Flow Controller and using a GeH4 flow 4 times higher resulted in modest Sn content layers, with some Sn surface segregation, however. Increasing, for fixed GeH4 and SnCl4 flows, the precursor partial pressures by (i) reducing the H2 carrier flow or (ii) increasing the chamber pressure resulted in linear GeSn Growth Rate (GR) and Sn content increases. Sn droplets were present on the surface up to 300 Torr, however. By contrast, GeSn layers grown at 400 Torr were high quality in XRD (well defined, intense peaks with thickness fringes, as shown in Fig. 1), with cross-hatched surfaces as the Ge SRBs underneath (Fig. 2). For a fixed GeH4 partial pressure (1.28 Torr), we have then evidenced a linear increase of the GeSn GR with the SnCl4 flow at 349°C. This increase was sub-linear at 325°C, with a slope change for P(SnCl4) = 0.008 Torr (Fig. 3). By contrast, the Sn content x was almost steady with the SnCl4 flow at 349°C. At 325°C, we had first of all an increase of the Sn content up to P(SnCl4) = 0.008 Torr, then a decrease, as shown in Fig. 4. Two SnCl4 partial pressures were therefore selected for the investigation of the impact of temperature on GeSn growth kinetics: 0.008 and 0.016 Torr (i.e. F(SnCl4)/F(H2) = 2E-05 or 4E-05). We had exponential increases, over the 301°C - 349°C range, of the GeSn GR with the temperature, with similar activation energies for both chemistries: 8.6 – 11.8 kcal mol.-1 for GeH4 ó 10.4 kcal. mol.-1 for Ge2H6 (Fig. 5). Meanwhile, the Sn content linearly decreased as the growth temperature increased, with a slope which was less for GeH4 than for Ge2H6 (- 1.0 or -1.1 % / 10°C, to be compared with - 1.7% / 10°C) (Fig. 6). Although the GeH4 flow was 4 times the Ge2H6 one and the chamber pressure 4 times higher (400 Torr ó 100 Torr), the GeSn GR was almost the same for a given SnCl4 flow. Sn contents were by contrast significantly lower with GeH4 than with Ge2H6. Halving, for the same GeH4 flow, the SnCl4 flow resulted in GeSn GR 40% lower but slighly higher Sn contents, which was once again counterintuitive! The Ge GR component (= (1-x)*GeSn GR) increased exponentially with the temperature, with similar values and activation energies for both precursors. Meanwhile, we had, over the 301°C-349°C range, a slight decrease of the Sn GR component (= x*GeSn GR) as the temperature increased. This was likely due to Sn sublimation. Sn GR components were 50% higher, for the same SnCl4 flow, with Ge2H6 than with GeH4. Complex interplays between precursors thus govern the GeSn growh kinetics with both precursors. Higher Sn contents and GeSn GR are nevertheless feasible with Ge2H6 + SnCl4 instead of GeH4 + SnCl4. Finally, while the GeSn GR and Sn contents were rather uniform over the 200mm wafer surface with Ge2H6 + SnCl4, the situation was definitely worse with GeH4 + SnCl4. GR were then significantly higher at the wafer edges than close to the center (although the Sn content was fairly uniform). Figure 1

We report on the synthesis of Si1−x Ge x alloy nanocrystals by very-high-frequency plasma-enhanced chemical vapor deposition (VHF PECVD) technique at different silane to germane gas flow ratio (R) in a mixture of (H2+Ar) dilution gas and H2 dilution gas alone. TEM, SAED, EDS studies and HAADF-STEM mapping of the samples were done to investigate the NCs' size, crystallinity and distribution of Si and Ge in the Si1−x Ge x alloy NCs. The average estimated size of the NCs in all the samples are in the order of exciton Bohr radius of Ge (24.3 nm), thereby indicating the probability of good quantum confinement. The alloy nature of NCs was confirmed in Raman study. The content of Ge in SiGe NCs was evaluated from Raman spectra which show a direct correlation with the fraction of hydrogen flow in the dilution gas mixture.

The SAGE experiment, which measures the flux of solar neutrinos, contains approximately 50 tonnes of liquid gallium metal. Low-energy neutrinos interact with the isotope Ga 71 in the Ga and convert it into Ge 71 at a rate of approximately one atom per day. In each measurement of the solar neutrinos about 210 μg of a stable Ge isotope in a Ga matrix is added to the Ga and the mixture is stirred to homogeneity. After a 30-day exposure of the gallium to solar neutrinos, any germanium is chemically extracted from the gallium. The Ge is converted into the gas germane and the number of Ge 71 atoms that it contains is measured in a proportional counter. After 6 months of counting, the Ge is removed from the counter, dissolved in an aqueous solution, and the isotopic content of Ge in this solution is measured by ICP-MS. The efficiency of extraction of Ge from the Ga is calculated from the measured mass and isotopic content of added and extracted Ge. In 75 recent exposures of the Ga to solar neutrinos the average Ge extraction efficiency was 97.7 ± 1.1%. This uncertainty in extraction efficiency is much less than the 3.3% uncertainty obtained by measurements of Ge mass alone, i.e., without isotopic analysis.

Specific features of the pyrolysis of hydride molecules on the surface of a Si1–x Ge x film under conditions of epitaxial film deposition of a mixture of silicon and germanium hydrides have been studied. Temperature dependences of the kinetic coefficients responsible for the rate of hydrogen desorption from the Si1–x Ge x film surface and the rate of dissociation of gas molecule radicals adsorbed by the surface of the growing film have been obtained for the first time, using the developed kinetic models of surface pyrolysis and the results of engineering experiments in the temperature range 450–800°C. A correlation between the dissociation frequencies of silane and germane molecules, as well as a correlation of the dissociation frequencies with other kinetic parameters of the system were revealed.

The paper considers two main approaches discussed in literature for conversion of gaseous fluorides SiF4, GeF4 and hydrogen-containing compound of germanium, i.e., GeH4, isotopic enriched by centrifugal method, into target products—stable isotopes of silicon and germanium in the form of bulk polycrystals and thin layers. In the first two-step (chemical) approach the fluorides are converted into intermediate compounds which are further subjected either to pyrolysis or to reduction by hydrogen. In the second single-step (plasma-chemical) approach the gaseous fluorides are reduced by hydrogen in plasma sustained by the discharges of different types.

Effects of RF power on optical, electrical, and structural properties ofμc-Si1−xGex:H films was reported. Raman and FTIR spectra fromμc-Si1−xGex:H films reflected the variation in microstructure and bonding configuration. Unlike increasing the germane concentration for Ge incorporation, low RF power enhanced Ge incorporation efficiency inμc-Si1−xGex:H alloy. By decreasing RF power from 100 to 50 W at a fixed reactant gas ratio, the optical bandgap ofμc-Si1−xGex:H was reduced owing to the increase in Ge content from 11.2 to 23.8 at.%, while Ge-related defects and amorphous phase were increased. Consequently, photo conductivity of 1.62 × 10−5 S/cm was obtained for theμc-Si1−xGex:H film deposited at 60 W. By applying 0.9 μm thickμc-Si1−xGex:H absorber withXCof 48% and [Ge] of 16.4 at.% in the single-junction cell, efficiency of 6.18% was obtained. The long-wavelength response ofμc-Si1−xGex:H cell was significantly enhanced compared with theμc-Si:H cell. In the case of tandem cells, 0.24 μm a-Si:H/0.9 μmμc-Si1−xGex:H tandem cell exhibited a comparable spectral response as 0.24 μm a-Si:H/1.4 μmμc-Si:H tandem cell and achieved an efficiency of 9.44%.

We have studied the in-situ boron (B) doping of germanium (Ge) and silicon (Si) in Reduced Pressure-Chemical Vapor Deposition. Three growth temperatures have been investigated for the B-doping of Ge: 400, 600 and 750 °C at a constant growth pressure of 13300 Pa (i.e. 100 Torr). The B concentration in the Ge:B epilayer increases linearly with the diborane concentration in the gaseous phase. Single-crystalline Ge:B layers with B concentrations in-between 9 ∙ 1017 and 1 ∙ 1020 cm− 3 were achieved. For the in-situ B doping of Si at 850 °C, two dichlorosilane mass flow ratios (MFR) have been assessed: F[SiH2Cl2]/F[H2] = 0.0025 and F[SiH2Cl2]/F[H2] = 0.0113 at a growth pressure of 2660 Pa (i.e. 20 Torr). Linear boron incorporation with the diborane concentration in the gas phase has been observed and doping levels in-between 3.5 ∙ 1017 and 1 ∙ 1020 cm− 3 were achieved. We almost kept the same ratio of B versus Si atoms in the gas phase and in the Si epilayer. By contrast, roughly half of the B atoms present in the gas phase were incorporated in the Ge:B layers irrespective of the growth temperature. X-Ray Diffraction (XRD) allowed us to extract from the angular position of the Ge:B layer diffraction peak the substitutional B concentration. Values close to the B concentrations obtained by 4-probe resistivity measurements were obtained. Ge:B layers were smooth (

The spectra of germane 72GeH4 and 73GeH4 enriched up to 99.9 % were recorded with high resolution (0.003 cm − 1 ) at different pressures with the Bruker IFS 125HR Fourier transform spectrometer (Nizhny Novgorod, Russia). The region of 4020–4260 cm − 1 , where the 2ν1(A1) and ν 1 + ν 3 ( F 2 ) bands are located, was theoretically analyzed. The 2025 and 1774 transitions with J max = 21 were assigned to these bands of the 72GeH4 and 73GeH4 species. Rotational, centrifugal distortion, tetrahedral splitting, and interaction parameters of the (2000, A1) and (1010, F2) vibrational states were determined from the fit of experimental line positions of both isotopologues. The obtained sets of 13/13 fitted parameters reproduce the initial 2025/1774 experimental line positions with a d rms = 2.9 × 10 − 4 cm − 1 and d rms = 2.7 × 10 − 4 cm − 1 (for 72GeH4 and 73GeH4, respectively).

The synthesis of 6-bromo-2,2-di-tert-butyl-4H-1,3,2-benzo[d]dioxagermine (1) via an alcohol/alkoxide exchange starting from di-tert-butyl-di-ethoxy germane is reported. Characterization of the title compound including single crystal X-ray diffraction and TGA/DSC analysis, mass spectrometry, 1H NMR, 13C{1H} NMR and IR spectroscopy is reported. DFT-D calculations have been carried out to assign the absorption band maxima of the IR spectrum to the corresponding vibrational modes. The suitability for Twin Polymerization of the novel dioxagermine 1 has been studied by TGA/DSC analysis and mass spectrometry. Proton-assisted Twin Polymerization of 1 results in an organic–inorganic hybrid material composed of a phenolic resin and [tBu2GeO]n.

Hydrogenated microcrystalline silicon germanium (μc-Si1−xGex:H) films were investigated as a bottom cell absorber in multi-junction solar cells. μc-Si1−xGex:H films were prepared using very high frequency (VHF, 60 MHz) plasma enhanced chemical vapor deposition (PECVD) systems working pressure of about 1.5 Torr. The precursor flow rates were carefully controlled to determine the phase transition point and to improve the crystallinity of μc-Si1−xGex:H. A relatively high plasma power was necessary to have the high hydrogen (H2) dilution. Raman spectroscopy study showed transition steps from amorphous to microstructure morphology as hydrogen dilution increasing. Crystallite Si–Ge and Ge–Ge bonds were occurred at relatively higher H2 dilution compare to crystallite Si–Si bond. The rapidly increased Ge content as increasing the H2 dilution is believed mainly due to the different decomposition rate of silane (SiH4) and germane (GeH4). The other reason of high Ge content even at the low GeH4 precursor flow rate is probably due to the preferential etching of silicon atom by H2. The preferential etching of Si–H possibly occurred in very highly concentrated H2 plasma due to the preferential attachment of Si–H. The compositions of μc-Si1−xGex:H films measured using RBS were Si0.83Ge0.17, Si0.67Ge0.33 and Si0.59Ge0.41 at H2/SiH4 flow rate of 60, 80 and 100, respectively. μc-Si1−xGex:H films showed the dark (σd) and photo conductivity (σp) of about 10−7 and 10−5 S/cm, respectively and photo response (σp/σd) was about 102. This study will present the comprehensive evaluation of crystallization behavior of μc-Si1−xGex:H films.

The structural evolution and nanocrystallization of hydrogenated amorphous silicon germanium (a-Si1 − xGex:H) thin films deposited by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) through decomposition of silane and germane diluted with argon gas have been investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopy, respectively. The results show that argon dilution gas plays a significant role in the growth of nanocrystalline grains in a-Si1 − xGex:H thin films. It is observed that the nanocrystalline grains have been developed in amorphous network when the argon dilution ratio is about 4, a relatively low ratio compared to hydrogen dilution. Moreover, the surface roughness, nano-grain size, crystalline volume fraction and hydrogen content of the thin films increase with the rise of argon dilution ratio. Besides, the electrical and optical properties of the samples with different argon dilution ratios have been also measured. Finally, the effect of germanium content on the nanocrystallization of the thin films with fixed argon dilution ratio has been studied. It is found that the a-Si1 − xGex:H thin films with high germanium content are prone to nanocrystallization.

The effect of germanium (Ge) on n-type 4H-SiC is experimentally studied by electrical characterization of homoepitaxial layers grown by chemical vapor deposition (CVD). Measurements show that electrical properties of epitaxial layers can be changed by intentional incorporation of germane (GeH4) gas during the deposition process. On the nanoscale, two-dimensional mappings acquired with conductive atomic force microscopy show preferential conductive paths on the surface of Gedoped samples, which are related to the presence of this isoelectronic impurity. Hall effect measurements confirm that also macroscopic electrical properties of n-type 4H-SiC are improved due to incorporation of Ge into SiC during CVD growth. In particular, despite equal free electron concentration, enhanced mobility in a wide temperature range is measured in Ge-doped samples as compared to a pure 4H-SiC layer. Based on our results from Hall effect measurements as well as admittance spectroscopy and deep level transient spectroscopy, it is speculated that Ge influences the generation and annealing of other point defects and thus helps to reduce the total concentration of defects.

We have studied the effect of Ge-concentration in gas phase on electronic properties of GeXSiY:H alloys deposited by RF-PECVD. The relative gas phase Ge concentration was varied from [Ge] gas = 50 % to 100 %. The electronic properties of the films were studied by the measurements of temperature dependence of dark conductivity σ dark (T) in the range of T= 300 to 430 K. The temperature dependence curves were described by the thermal activated conduction model and activation energy and Fermi level parameters were calculated. A change in dark conductivity was found from 1.7×10−6 Ω−1cm−1 at [Ge] gas = 50 % to 1.1×10−4 Ω−1cm−1 at [Ge] gas =100 %. The correlation between Ge in gas phase and conductivity was reflected in activation energy and Fermi level values that varied from E a = 0.37 to 0.23 eV and E F =0.27 to 0.10 eV, respectively.

High quality Ge epitaxy on a GaAs (100) substrate was grown by metal-organic chemical vapor deposition using germane. The effects of growth temperature and deposition rate on the quality of the Ge epitaxy are investigated. Significant improvement in surface root-mean-square roughness is observed with increasing Ge growth temperature or deposition rate, while keeping all other deposition parameters unchanged. Investigation of the Ge material quality grown after different GaAs surface preparation conditions shows that Ga rich surfaces are beneficial for smooth Ge surfaces, which is attributed to the formation of Ge–Ga bonds at the initiation of the Ge deposition. The good crystalline quality of grown Ge film was further confirmed by high-resolution X-ray diffraction and secondary ion mass spectrometry characterization.

Hydrogenated amorphous silicon–germanium–carbide (a-SiGeC:H) has been fabricated by monomethyl germane (MMG, GeH 3 CH 3 ) under various deposition conditions, inter-electrode distance ( d ele ) in VHF-PECVD and gas flow ratios. With decreasing d ele , it is observed from optical emission spectroscopy (OES) that the generation of atomic hydrogen in plasma gradually increases. It is also found that the enhanced atomic hydrogen tends to take both Ge and C away from growing surfaces, leading to the decrease in Ge and C contents. The total content of hydrogen bonds increases as a result of the increase in both Si H and Ge H bonds as the d ele decreases. Consequently, the a-SiGeC:H solar cells fabricated at narrower d ele exhibit the improved performance. Even though the optical band gap ( E opt ) of the a-SiGeC:H increases with decreasing d ele , the quantum efficiency (QE) spectra reveal even an increasing trend of long wavelength regions because of the significant improvement in i-layers. It is also confirmed that a lot lower MMG/SiH 4 was needed for the films having certain E opt , when fabricated near amorphous-to-crystalline transition, and the solar cell fabricated near the transition region shows the better performance.

NMR relaxation methods probe biomolecular motions over a wide range of timescales. In particular, the rotating frame spin-lock R(1ρ) and Carr-Purcell-Meiboom-Gill (CPMG) R(2) experiments are commonly used to characterize μs to ms dynamics, which play a critical role in enzyme folding and catalysis. In an effort to complement these approaches, we introduced the Heteronuclear Adiabatic Relaxation Dispersion (HARD) method, where dispersion in rotating frame relaxation rate constants (longitudinal R(1ρ) and transverse R(2ρ)) is created by modulating the shape and duration of adiabatic full passage (AFP) pulses. Previously, we showed the ability of the HARD method to detect chemical exchange dynamics in the fast exchange regime (k(ex)∼10(4)-10(5) s(-1)). In this article, we show the sensitivity of the HARD method to slower exchange processes by measuring R(1ρ) and R(2ρ) relaxation rates for two soluble proteins (ubiquitin and 10C RNA ligase). One advantage of the HARD method is its nominal dependence on the applied radio frequency field, which can be leveraged to modulate the dispersion in the relaxation rate constants. In addition, we also include product operator simulations to define the dynamic range of adiabatic R(1ρ) and R(2ρ) that is valid under all exchange regimes. We conclude from both experimental observations and simulations that this method is complementary to CPMG-based and rotating frame spin-lock R(1ρ) experiments to probe conformational exchange dynamics for biomolecules. Finally, this approach is germane to several NMR-active nuclei, where relaxation rates are frequency-offset independent.

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.

In this study, the growth kinetics of SiGe in a reduced pressure chemical vapor deposition system using dichlorosilane (SiH2Cl2) and germane (GeH4) as the Si and Ge precursors were investigated. The SiGe growth rate and Ge content were found to depend on the deposition temperature, GeH4 flow and reactor chamber pressure. The SiGe growth rate escalates with increasing deposition temperature, while the Ge content is reduced. The SiGe growth rate accelerates with increasing GeH4 flow, while the Ge content increases more slowly. According to the experimental data, a new relationship between Ge content (x) and F(GeH4)/F(SiH2Cl2) mass flow ratio is deduced: x2.5/(1−x) = nF(GeH4)/F(SiH2Cl2). The SiGe growth rate and Ge content improve with increasing reactor chamber pressure. By selecting proper precursor flows and reactor pressure, SiGe films with the same Ge content can be fabricated at various temperatures. However, the quality of the SiGe crystals is clearly dependent on the deposition temperature. At lower deposition temperature, higher crystalline quality is achieved. Because the growth rate dramatically drops with lower temperatures, the optimum growth temperature must be a compromise between the crystalline quality and the growth rate. X-ray diffraction, Raman scattering spectroscopy and atomic force microscopy results indicate that 650°C is the optimum temperature for fabrication of Si0.75Ge0.25 film.

In this paper, we report on deposition and properties of nanocrystalline Ge:H films . The films were grown from germane and hydrogen mixtures using Radio frequency Plasma-enhanced chemical vapor deposition (RF-PECVD) process using ∼45 MHz frequency. The crystallinity of the films was measured using Raman measurements and from x-ray diffraction techniques, it was found that the grain size was a strong function of deposition pressure, temperature and hydrogen/germane ratios. High hydrogen ratios and high powers led to films with smaller grains. Higher pressures and smaller hydrogen/germane ratio led to films with larger grain sizes, as did higher growth temperatures. The mobility of electrons and holes was measured using space charge limited current (SCLC) techniques in n+-n-n+ devices. It was found that nominally undoped films were generally n type with carrier concentrations in the 1E14/cm3 range. Mobility was found to increase with grain size, with 60 nm grains showing mobility in the 2-3 cm2/V-s range.

A method has been developed for the extraction of single 71Ge atoms from the gallium target of a Ga-Ge neutrino detector. The key features of this chemical process stem from the extremely low content of the element to be extracted in the sample (n × 10−27 at %), the large sample weight (up to n × 103 kg), the limited time available for the extraction and measurement of the extracted atoms (≤20 h), and small permissible loss (≤0.1%) of the target material at high degrees of 71Ge extraction (≥90%). The method involves forced generation and maintenance of a disperse system of liquid gallium droplets with an oxide surface film in an acid-peroxide solution. The small droplet size ensures a rapid 71Ge transfer from the bulk target to a small amount of gallium oxide. The 71Ge passes from the oxide film to the solution, is concentrated, and converts to germane, which is delivered to a proportional counter. We have assessed the completeness of germanium extraction in relation to process conditions. The results, in particular the completeness of extraction, have been verified in experiments with Ga + Ge mixtures at germanium concentrations of 10−4 and 10−17 to 10−16 wt %. The adequacy of the approaches used to develop the technology of the Ga-Ge detector is supported by satisfactory agreement between the solar neutrino fluxes obtained with gallium and gallium-chloride detectors.

Negative ion formation by low-energy electron impact to germane (GeH4) has been performed in an electron energy region from 6 to 11 eV with an energy resolution of ∼500 meV. Anion efficiency curves of four anions have been measured. Product anions are observed mainly in the 6–11 eV energy region, yielding GeHx− (x = 0–3). Comparative studies with methane (CH4) and silane (SiH4) are also presented with the most intense signals observed at 14 amu (CH2−), 31 amu (SiH3−) and 75 amu (GeH3−) from CH4, SiH4 and GeH4, respectively. Fragmentation into these negative ions is attributed to resonant dissociative electron attachment processes.

The hyperbranched copolymers of tris(pentafluorophenyl)germane (C6F5)3GeH and bis(pentafluorophenyl)germane (C6F5)2GeH2, synthesized by the method of activated copolycondensation, have been studied by means of dynamic and static light scattering methods, analytical ultracentrifugation, isothermal translational diffusion, and capillary viscometry in dilute chloroform solutions. It has been shown that the copolymer molar mass grows with increasing content of (C6F5)2GeH2. The molecules of polymer investigated have a compact dense structure, their shape being slightly different from the spherical one.

Controlled boron doping of Si1 − xGex epilayers has been achieved during low-temperature growth of SiGe/Si(100) heterostructures by sublimation of boron-doped silicon in a germane medium. Boron-doped single-crystalline silicon plate was sublimed by resistive heating to ∼1300°C. Using this source, heterostructures with selectively doped layers, sharp dopant concentration profiles, and a maximum boron concentration of ∼1 × 1019 cm−3 were obtained.

We report on the growth of n- and p-doped Germanium (Ge) on Ge substrates by Metal-Organic Vapor Phase Epitaxy (MOVPE). Iso-butyl germane, a liquid metal-organic source less toxic than Germane, is used as Ge precursor. We demonstrate the p-doping of Germanium by MOVPE using Trimethylgallium. The influence of the growth parameters for n and p-type doping is studied in order to optimize the morphology, the structural and the electrical properties of the Ge layers. The controlled growth of p and n doped Ge layers opens the possibility to realize totally epitaxially grown Ge diodes with improved performances, for example, for solar cell applications.

Hydrogenated amorphous silicon–germanium–carbide (a-SiGeC:H) thin films have been fabricated by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) using monomethyl germane (MMG, GeH 3 CH 3 ) as the germanium source. It was found that C incorporation into the films was considerably suppressed under high hydrogen dilution ( R H ) and substrate temperature ( T S ). Under high R H and T S , we were able to narrow the optical band gap ( E opt ) of a-SiGeC:H thin films to 1.39 eV, whereas under low R H and T S , E opt increased up to 1.9 eV with increasing MMG. The best electrical properties were obtained for a sample of a-Si 0.68 Ge 0.29 C 0.03 :H, whose E opt and photosensitivity were 1.58 eV and 10 5 , respectively. When this film was used as an absorber layer in a p–i–n structured solar cell, significant enhancements were observed in its quantum efficiency for long wavelengths.

Hydrogenated amorphous silicon–germanium (a-Si x Ge 1− x :H) thin films were grown using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD, 27.13 MHz). The films were used in a silicon-based thin film solar cell. The films were grown from a gas mixture of silane (SiH 4 ) and tunable germane (GeH 4 ) gas that was diluted in hydrogen (H 2 ). The results show that the optical band gap ( E g ), optical adsorption coefficient ( α ), grain size and chemical composition depend on the germane contents of the films. The relationships among optical properties, structural properties, and chemical structural features were characterized by UV–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), X-ray photoelectron spectrometer (XPS), and Raman spectroscopy. a-Si x Ge 1− x :H solar cells with an efficiency of 5.59% were obtained the films.

Chemical processes in course of low pressure CVD of tris(trimethylsilyl)germane (SiCH3)3GeH leading to formation of shelled germanium nanowires are discussed. The nanowires were grown in the flow mode at 50–60 Pa and 365 °C of substrate temperature. The wires consist of a crystalline Ge core surrounded by a two-layer jacket. FTIR measurements and GC–MS analysis let conclude that precursor decomposition starts by an intramolecular elimination of trimethylsilane HSiMe3 yielding bis(trimethylsilyl)germylene (SiMe3)2Ge: that polymerizes. Parallely, Si–Ge bonds split, SiC based moieties form Si/C shell and Ge atoms crystalline core and nanocrystalline inner jacket. The samples were studied by SEM, HRTEM, EDX, FTIR and GC–MS techniques.

IR laser irradiation of an equimolar silane–germane mixture in Ar results in the decomposition of both compounds and allows chemical vapour deposition (CVD) of solid nanostructured Si/Ge film that was analyzed by FTIR and Raman spectroscopy, X-ray diffraction and electron microscopy. The film is deduced to be formed via coalescence/intermixing of extruded Si and Ge atoms and revealed as metastable and consisting of the crystalline d-c Ge and crystalline Si/Ge alloys embedded in an amorphous Si and Si/Ge phase. The reported IR laser CVD of the nanostructured Si/Ge film represents a simple way for synthesis of binary alloys from volatile hydride precursors.

For future CMOS technologies, epilayers such as Si, SiGe and SiC are intensively investigated as candidates for Sources and Drains and channel materials. A low thermal budget and high growth rate is mandatory, mainly for FDSOI applications in order to overcome a Si dewetting phenomenon which occurs at high temperature. In this context, conventional precursors such as Silane (SiH4) and DichloroSilane (SiH2Cl2) are not sufficiently reactive to get high growth rate at low temperature (< 600°C). Due to the lower activation energy for breaking Si-Si bond vs Si-H bond, new precursors, like Trisilane (Si3H8) 4 and Disilane (Si2H6), are promising candidates. In the first part of this paper, we investigate the efficiency of Disilane based Si epitaxy at low temperature. The results obtained are compared to those obtained with conventional chemistry (i.e. SiH4). The growth rate as well as the surface roughness will be addressed. Then, we will discuss on the incorporation of Ge as the function of the growth temperature and the growth rate will be compared to the one obtained with a conventional chemistry. Thin films, either Si or SiGe are epitaxially grown in an industrial ASM epsilon E3200 reduced pressure chemical vapor deposition (RPCVD) reactor on 300mm Si (001) substrates. SiH4 and Si2H6 are used as silicone precursor while the germanium source gas was diluted Germane (10% GeH4 in H2). The Si layer thickness is evaluated by differential weight measurements. The layer thickness is assessed by Atomic Force Microscopy (AFM) on a DI3100 Nanoscope III. Low temperature epitaxial growth of Si layers : The growth rate of Si as a function of the growth temperature for Silane and Disilane chemistry is plotted in figure 1. The partial pressure is remained constant whatever the precursor used is.

We have regulated the number density and the size of the fine particles/clusters called nanoparticles into the a-SiGe:H films deposited from silane and germane diluted in hydrogen by applying a square wave pulse modulations (SWPM) of the rf (13.56 MHz) amplitude in plasma enhanced chemical vapor deposition (PECVD). The plasma “on” time Ton and “off” time Toff were controlled over a wide range from 300 μsec to 30 msec. Growth rate (γr) of the number density (Nr) of the particles of size r shows a lognormal dependence on r. Tendency towards formation of nanocrystallites was observed on reducing the Ton. Ge content within nanocrystallites was found to increase with decrease in nanocrystallites size. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The synthesis of the model functionalized polymers of various molecular weight–containing active pentafluorophenylgermanium end groups was performed through chain-transfer reaction to germanium organic compounds-tris(pentafluorophenyl)germane by a free-radical polymerization of styrene. Upon subsequent activated copolycondensation of the obtained polymers with tris(pentafluorophenyl)germane in methyl ethyl ketone environment in the presence of the activator triethylamine hybrid linear-dendritic the block copolymers of polystyrene and perfluorinated poly(phenylenegermane) were obtained. Molar mass and hydrodynamic characteristics of model and hybrid polymers were studied by the methods of size exclusion chromatography, static and dynamic light scattering, and viscometry.

TEA CO2 laser-induced dielectric breakdown of an equimolar mixture of gaseous stannane and germane in Ar allows decomposition of both metal hydrides and chemical vapour deposition of the nanostructured Ge/Sn films. Analysis of the films by FTIR and Raman spectroscopy, X-ray diffraction analysis and electron microscopy revealed nanoregions of crystalline Sn and Sn-rich Ge/Sn alloys surrounded by an amorphous Ge/Sn phase. The crystalline Ge/Sn nanoalloys contain different amounts of Sn incorporated into the Ge lattice and undergo changes in composition at temperatures as low as 200 °C.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Epitaxial growth of germanium is attractive for Ge/III–V hetero devices such as multi-junction solar cells. We investigated the growth of Ge with iso-butyl germane (IBGe) as germanium source and found a strong memory effect in our AIX2600-G3 metalorganic vapor phase epitaxy (MOVPE) reactor. The germanium background led to a higher n-type doping of i-GaAs and strongly reduced the photoluminescence (PL) intensity of Al 0.3 Ga 0.7 As and Ga 0.5 In 0.5 P. With secondary ion mass spectroscopy (SIMS) the quantity of Ge in Al 0.3 Ga 0.7 As could be determined to be in the range of 2×10 17 cm −3 , whereas a Ge-atom concentration in Ga 0.5 In 0.5 P of up to 2×10 18 cm −3 was measured. The memory effect could be eliminated by changing all contaminated parts inside the MOVPE reactor.

The ion-molecule reactions occurring in GeH(4)/NF(3), GeH(4)/SF(6), and GeH(4)/SiF(4) gaseous mixtures have been investigated by ion trap mass spectrometry and ab initio calculations. While the NF(x)(+) (x=1-3) react with GeH(4) mainly by the exothermic charge transfer, the open-shell Ge(+) and GeH(2)(+) undergo the efficient F-atom abstraction from NF(3) and form GeF(+) and F-GeH(2)(+) as the only ionic products. The mechanisms of these two processes are quite similar and involve the formation of the fluorine-coordinated complexes Ge-F-NF(2)(+) and H(2)Ge-F-NF(2)(+), their subsequent crossing to the significantly more stable isomers FGe-NF(2)(+) and F-GeH(2)-NF(2)(+), and the eventual dissociation of these ions into GeF(+) (or F-GeH(2)(+)) and NF(2). The closed-shell GeH(+) and GeH(3)(+) are instead much less reactive towards NF(3), and the only observed process is the less efficient formation of GeF(+) from GeH(+). The theoretical investigation of this unusual H/F exchange reaction suggests the involvement of vibrationally-hot GeH(+). Passing from NF(3) to SF(6) and SiF(4), the average strength of the M-F bond increases from 70 to 79 and 142 kcal mol(-1), and in fact the only process observed by reacting GeH(n)(+) (n=0-3) with SF(6) and SiF(4) is the little efficient F-atom abstraction from SF(6) by Ge(+). Irrespective of the experimental conditions, we did not observe any ionic product of Ge-N, Ge-S, or Ge-Si connectivity. This is in line with the previously observed exclusive formation of GeF(+) from the reaction between Ge(+) and C-F compounds such as CH(3)F. Additionally observed processes include in particular the conceivable formation of the elusive thiohypofluorous acid FSH from the reaction between SF(+) and GeH(4).

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 GeHx 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 GeHx 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 GeHx decomposition to Ge and H followed by their desorption, while the appearance of GeOx is attributed to possible reactions between GeHx species with hydroxyl groups and/or oxidation of Ge clusters by background oxidants.

Bare and partially hydrogenated Si x Ge y H z ( x = 1–3, y = 1–5, z = 0–4) clusters were observed upon flash pyrolysis of a 1:1 mixture of silane (SiH 4 ) and germane (GeH 4 ), diluted to 2% each in He at temperatures above ∼1200 K. Thermal decomposition occurred on a short (∼20 μs) time scale after which pyrolysis products were cooled and isolated in a supersonic molecular beam and detected by single photon vacuum ultraviolet (VUV) photoionization time-of-flight mass spectrometry (TOFMS). Cluster formation occurs primarily through insertion of SiH 2 and GeH 2 into silane, germane, polysilanes and polygermanes. Formation of larger Si x Ge y clusters where x + y > 4 may also result from combination of smaller clusters.

Effect of the post-growth annealing on the morphology of a Ge mesa selectively grown on Si was studied from the viewpoint of near-infrared photodiode applications. By ultrahigh-vacuum chemical vapor deposition, Ge mesas were selectively grown at 600°C on Si (001) substrates partially covered with SiO2 masks. The as-grown Ge mesas showed trapezoidal cross-sections having a top (001) surface and {311} sidewall facets, as similar to previous reports. However, after the subsequent post-growth annealing at -800°C in the ultrahigh-vacuum chamber, the mesas were deformed into rounded shapes having a depression at the center and mounds near the edges. Such a deformation cannot be observed for the samples annealed once after cooled and exposed to the air. The residual hydrogen atoms on the Ge surface from the germane (GeH4) decomposition is regarded as a trigger to the observed morphological instability, while the final mesa shape is determined in order to minimize a sum of the surface and/or strain energies.

There is a great interest in electronic transitions in hydrogen-rich materials under extreme conditions. It has been recently suggested that the group IVa hydrides such as methane (CH 4 ), silane (SiH 4 ), and germane (GeH 4 ) become metallic at far lower pressures than pure hydrogen at equivalent densities because the hydrogen is chemically compressed in group IVa hydride compounds. Here we report measurements of Raman and infrared spectra of silane under pressure. We find that SiH 4 undergoes three phase transitions before becoming opaque at 27–30 GPa. The vibrational spectra indicate the material transforms to a polymeric (framework) structure in this higher pressure range. Room-temperature infrared reflectivity data reveal that the material exhibits Drude-like metallic behavior above 60 GPa, indicating the onset of pressure-induced metallization.

In this work we study the atomic composition in SiGe:H films as a function of hydrogen dilution. Silane and germane fluxes are kept constant while hydrogen flow is varying to achieve dilutions up to 80 times. Solid content of principle elements as well as contaminants are determined by SIMS. For low dilutions (from 9 to 30), germanium solid content strongly depends on hydrogen dilution since it varies from 0.485 to 0.675. Higher presence of hydrogen in the mixture does not change germanium content which remains close to the value of 0.69.

Germanium tin alloys were grown directly on Si substrate at low temperatures using a cold-wall ultra-high vacuum chemical vapor deposition system. Epitaxial growth was achieved by adopting commercial gas precursors of germane and stannic chloride without any carrier gases. The X-ray diffraction analysis showed the incorporation of Sn and that the Ge1-xSnx films are fully epitaxial and strain relaxed. Tin incorporation in the Ge matrix was found to vary from 1% to 7%. The scanning electron microscopy images and energy dispersive X-ray spectra maps show uniform Sn incorporation and continuous film growth. Investigation of deposition parameters shows that at high flow rates of stannic chloride the films were etched due to the production of HCl. The photoluminescence study shows the reduction of bandgap from 0.8 eV to 0.55 eV as a result of Sn incorporation.

The digermene molecule, Ge 2 H 4 (X 1 A g ), and the digermenyl radical, Ge 2 H 3 (X 2 A″), together with their fully deuterated isotopomers were observed for the first time in low temperature germane and D4-germane matrices at 12 K via infrared spectroscopy upon irradiation of the ices with energetic electrons. The ν 3 fundamentals were detected at 1825 cm −1 and 1317 cm −1 for Ge 2 H 3 (X 2 A″) and Ge 2 D 3 (X 2 A″), respectively, whereas the digermene molecule H 2 GeGeH 2 (X 1 A g ) and its D4-isotopomer were monitored via their absorptions at 845 cm −1 ( ν 11 ) and 1476 cm −1 ( ν 5 ), respectively. The infrared absorptions of the hitherto elusive digermene and digermenyl species may aid in monitoring chemical vapor deposition processes of germane via time resolved infrared spectroscopy and can also provide vital guidance to search for this hitherto undetected germanium-bearing molecule in the atmospheres of Jupiter and Saturn.