Si OD Research Articles

X-ray and Neutron Study on the Structure of Hydrous SiO2 Glass up to 10 GPa

The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature conditions and its structure was investigated by small angle X-ray scattering, X-ray diffraction, and neutron diffraction experiments at pressures of up to 10 GPa and room temperature. This hydrous glass is separated into two phases: a major phase rich in SiO2 and a minor phase rich in D2O molecules distributed as small domains with dimensions of less than 100 Å. Medium-range order of the hydrous glass shrinks compared to the anhydrous SiO2 glass by disruption of SiO4 linkage due to the formation of Si–OD deuterioxyl, while the response of its structure to pressure is almost the same as that of the anhydrous SiO2 glass. Most of D2O molecules are in the small domains and hardly penetrate into the void space in the ring consisting of SiO4 tetrahedra.

Structure of the Hydroxyl Groups and Adsorbed D2O Sites in the DX Zeolite: DFT and Experimental NMR Data

We report on density functional theory computations combined with the results of measurements of the quadrupole coupling constants for 17O, hydroxyl deuterons, and adsorbed water deuterons in DX zeolite (n(Si)/n(Al) = 1). Calculations are performed for the crystalline periodic model of the DX zeolite. The local structural parameters are found for various oxygen positions at equilibrium. The quadrupole coupling constants for 17O are in the range CQ(17O) = 7.75 ± 0.5 and 3.75 ± 0.5 MHz for (Si–OD–Al) and (Si–O–Al) substructures, respectively. Related values of the asymmetry parameter η fall in the ranges of 0.9 ± 0.5 and 0.15 ± 0.1, respectively. The quadrupole coupling constant for deuterons depends on the OD distance according to the relation CQ(D)[MHz] = −2.732dOD[MHz/A] + 2.938 MHz. Deuterons are assigned to labeled oxygen positions according to the decreasinng quadrupole coupling constant CQ(D) as O1 ≥ O4 > O2 > O3, with their relative abundances of 54.4, 7.6, 26.6, and 11.4%, respectively. The binding...

The relaxation of intrinsic compressive stress in complementary metal-oxide-semiconductor transistors by additional N ion implantation treatment with atomic force microscope-Raman stress extraction

Based on the stress extraction and measurement by atomic force microscope-Raman technique with the nanometer level space resolution, the high compressive stress about 550 MPa on the Si active region (OD) is observed for the current complementary metal-oxide-semiconductor (CMOS) transistor. During the thermal budget for the standard manufacture process of the current CMOS transistor, the difference of thermal expansion coefficients between Si and Shallow Trench Isolation (STI) oxide results in this high compressive stress in Si OD and further degrades the electron carrier mobility seriously. In order to relax this intrinsic processed compressive stress in Si OD and try to recover this performance loss, the novel process is proposed in this work in addition to the usage of one-side pad SiN layer. With this novel process of additional N-ion implantation (IMP) treatment in STI oxide, it can be found that the less compressive stress about 438 MPa in Si OD can be achieved by the smaller difference of thermal expansion coefficients between Si and N-doped SiO2 STI oxide. The formation of Si-N bonding in N-doped SiO2 STI region can be monitored by Fourier transform infrared spectroscopy spectra and thermal expansion coefficients for Si, SiO2, and SiN are 2.6 ppm/K, 0.4 ppm/K, and 2.87 ppm/K, respectively. The effective relaxation of intrinsic processed compressive stress in Si OD about 112 MPa (from 550 MPa to 438 MPa) by this proposed additional N IMP treatment contributes ∼14% electron carrier mobility enhancement/recovery. The experimental electrical data agree well with the theoretical piezoelectricity calculation for the strained-Si theory.

The systematic study and simulation modeling on nano-level dislocation edge stress effects

The comprehensive investigation on the effect of dislocation edge stress for Si N-type metal-oxide-semiconductor field-effect transistors is presented in this work by the experimental measurement and proposed simulation model. The accurate stress measurement in Si OD region with and without dislocation edge stress treatment is extracted by atomic force microscope-Raman technique with the nanometer level space resolution. Less compressive stress in Si OD region on the real transistor with dislocation edge stress treatment is observed successfully and has its corresponding higher electron carrier mobility, agreed with the strained Si theory. Main reasons for the less compressive stress in the device with dislocation edge stress treatment are the more stress relaxation of the STI intrinsic compressive stress in modern CMOS process and one layer Si atom missing near the source and drain region along the dislocation line. The measured stress from AFM-Raman spectra experimentally, the simulated stress from proposed finite element method, and its corresponding electrical characteristics agrees well with each other in this work. After the comprehensive understanding and calibrated model for the dislocation edge stress, the relationship between channel stress and dislocation edge shapes, including the angle and length of dislocation lines is simulated and investigated clearly. It can be found that longer dislocation line and smaller dislocation angle can relax the intrinsic STI compressive stress more and should have the better electron carrier mobility and device performance for N-MOSFETs.

Activation of dihydrogen on supported and unsupported silver catalysts

The activation of dihydrogen on silica, silver, and silica-supported silver (9 wt% Ag) was investigated. Both silica and silver are individually able to dissociate dihydrogen. Silanol groups on silica undergo H → D exchange at 393 K in D 2 as detected by IR spectroscopy. HD is observed in temporal analysis of products (TAP) experiments when H 2 and D 2 are sequentially pulsed on silver at 673 K; even when the time delay between the isotopes is 4 s, HD is formed, indicating that long-lived surface hydrogen species are present. Differential scanning calorimetry (DSC) shows that the activation of dihydrogen is an activated process: heat signals evoked through H 2 pulses on Ag/SiO 2 grow with increasing temperature (373–523 K). Nonetheless, the presence of silver on the silica surface accelerates the Si–OH → Si–OD exchange. Investigation of the exchange kinetics on Ag/SiO 2 shows that diffusion processes of the activated hydrogen species are rate determining at higher temperatures (⩾373 K), when the activation of D 2 on silver becomes facile. Indications of diffusion limitation are observed already at 313 K on Pt/SiO 2. TAP and DSC measurements show that H 2 is more readily activated on silver that has been treated in O 2 at 673 K followed by reduction in H 2 at 673 K. Morphological changes induced to the silver surfaces or (sub)surface oxygen species are presumed responsible for this effect.

2H-solid-state-NMR study of hydrogen adsorbed on catalytically active ruthenium coated mesoporous silica materials

2H solid-state NMR measurements were performed on three samples of ruthenium nanoparticles synthesized inside two different kinds of mesoporous silica, namely SBA-3 silica materials and SBA-15 functionalized with –COOH groups and loaded with deuterium gas. The line-shape analyses of the spectra reveal the different deuteron species. In all samples a strong –OD signal is found, which shows the catalytic activity of the metal, which activates the D–D bond and deuterates the –SiOH groups through the gas phase, corroborating their usability as catalysts for hydrogenation reactions. At room temperature the mobility of the –Si–OD groups depends on the sample preparation. In addition to the –Si–OD deuterons, the presence of different types of deuterons bound to the metal is revealed. The singly coordinated –Ru–D species exhibit several different quadrupolar couplings, which indicate the presence of several non-equivalent binding sites with differing binding strength. In addition to the dissociated hydrogen species there is also a dihydrogen species –Ru–D 2, which is attributed to defect sites on the surface. It exhibits a fast rotational dynamics at all temperatures. Finally there are also indications of three-fold coordinated surface deuterons and octahedrally coordinated deuterons inside the metal.

H2 adsorption and H/D exchange on Au/TS-1 and Au/S-1 catalysts

We report a combined quantum-mechanics/molecular-mechanics (QM/MM) analysis of H2 dissociation and hydrogen–deuterium (H/D) exchange on four potential active sites inside the TS-1 pores: (1) Au3/T6–Ti-non-defect, (2) Au3/T6–Si-non-defect, (3) Au3/T6–Ti-defect, and (4) Au3/T6–Si-defect. We provide full kinetic and thermodynamic data calculated at standard conditions (298.15 K, 1 atm) for Eley–Rideal mechanisms on these sites. The H/D exchange on Au3/TS-1 occurs in two steps: (1) first H2 dissociation on Au3/TS-1 to form H–Au3–H species and (2) D2 (or second H2) attack on these H–Au3–H species to form HD. The energetics of the first H2 dissociation step is site-sensitive (with respect to Au sites), while that of the D2 (or second H2) addition step is not site-sensitive. We found that two different mechanisms for the second step are both kinetically and thermodynamically favorable. The most favorable mechanism (ΔE act ~ 28 kcal/mol) involves an attack of D2 on both the H atoms in the H–Au3–H intermediate, and two HD molecules are formed simultaneously. The first H2 dissociation step is almost thermoneutral and the D2 (or second H2) addition step is somewhat exothermic. A comparison of the pure QM and QM/MM calculations on Au3/TS-1 suggests that the formation of the H–Au3–H species inside the TS-1 pores becomes thermodynamically more favorable due to the long-range interactions. The activation energies for the first H2 dissociation step (19–24 kcal/mol) are lower than those for the D2 (or second H2) addition step (28–31 kcal/mol). Therefore, the increase in the HD formation rate with temperature is likely to be stronger than the increase in the H–Au3–H formation rate. On the basis of the calculated activation energies and the reaction thermochemistry, we predict a viable Eley–Rideal H/D exchange pathway that may operate at or above 573 K. We also found potential H/D exchange channels on bare TS-1 (without Au3) where gas-phase D2 (or second H2) attacks the Ti–OH or Si–OH groups (of defect sites) and exchanges one of the D atoms to form HD and Ti–OD or Si–OD groups.

Control of the nucleation density of Si quantum dots by remote hydrogen plasma treatment

The influence of surface pretreatments by remote hydrogen and/or argon plasma on the silicon nucleation density on thermally grown SiO 2 in the early stages of low pressure chemical vapor deposition (LPCVD) using monosilane (SiH 4) has been studied to control the areal density of Si quantum dots (Si-QDs) on SiO 2. In the remote H 2 (or D 2) plasma treatments prior to SiH 4-LPCVD, the formation of Si OH (Si OD) surface bonds, which act as reactive sites, was confirmed from no changes in the SiO 2 surface microroughness and in the thickness. In fact, by a H 2 plasma pretreatment, the areal density of Si-QDs as high as 7 × 10 10 cm −2 was obtained in the LPCVD condition of the dot density with as low as 6 × 10 8 cm −2 on as-grown SiO 2. By changing the pressure and the substrate temperature in the H 2 plasma pretreatment, the dot density was controlled in the range of 4 × 10 9 to 7 × 10 10 cm −2. Further increase in the dot density and improvement of the dot size uniformity was also demonstrated by the pretreatment of Ar plasma followed by H 2 plasma, presumably because of improved uniformity and integrity in SiO 2 surface coverage with OH bonds just before LPCVD.

Interaction of deuterium with SIMOX buried oxide

We have studied SIMOX buried oxide samples implanted with D + (10 14–10 15 cm −2) or annealed in D 2 (300–500 kPa at 1073 K). Thermal desorption spectrometry (TDS) performed on these samples after removal of the top Si layer shows two main peaks related to release of deuterium from Si–D and Si–OD defects. The first peak is dominant in implanted samples and the second in deuterium-annealed samples. In TDS experiments on samples with top layer the deuterium release is limited by diffusion in SiO 2, D 2-cracking at the Si/SiO 2 interface and permeation through the top Si layer. In these samples the D 2 signal is related to release through lateral surfaces, whereas the HD signal is produced by release through the top Si layer.

The behaviour of deuterium incorporated into the buried oxide of SIMOX

The buried oxide (BOX) layer of SIMOX samples was implanted with 20–30 keV D + ion implantation at doses from 10 14 to 10 16 cm −2 . Other samples were exposed to pure deuterium gas (0–1 MPa) at temperatures in the range 800–1100 K. Thermal desorption spectrometry (TDS) revealed two main trapping sites for deuterium in the buried oxide. The first releases deuterium at ∼900 K (activation energy ∼2.5 eV) and the second at ∼1250 K (activation energy ∼3.4 eV). They are attributed to dissociation of Si–D and Si–OD groups, respectively. The first peak is dominant in the implanted samples while the second is the dominant one for samples exposed to deuterium gas. The formation of the Si–OD groups is a temperature-activated process. The trapping of deuterium in the implanted samples is related to implantation-induced vacancy-like defects that are detected by means of positron beam analysis (PBA). Annealing at 900 K leads to a complete defect recovery. Deuterium profiling by SIMS confirms the trapping in the defects.

Dynamic Multiple Tracing with D2and C2D4in Ethylene Hydroformylation over Mn–Rh/SiO2

Combined FT-IR/mass spectrometry was used to study the dynamic behavior of hydrogen/deuterium adsorbates in response to D2and C2D4pulses during ethylene hydroformylation on Mn–Rh/SiO2at 513 K and 0.1 MPa. Variation of exposure time of the catalyst to the D2and C2D4pulses revealed that readsorption did not play a significant role in the product responses; long exposure time allows more deuterium to enter the slower pathway ofd1- andd2-propionaldehyde. The two-unequal-hump HD response from both the D2and C2D4pulses indicates the presence of an isotope effect on hydrogen/deuterium adsorption. The rapid responses of the deuterated ethylene and ethane can be described by the Horiuti-Polanyi mechanism and indicate that their intermediates have small θ (surface coverage) and τ (residence time) which cannot be resolved by the time resolution of their transient responses. Thed1- andd2-propionaldehyde products show a two-hump response, which can be explained by the different deuterium incorporation pathways into the propionaldehyde. The first hump is due to hydrogen/deuterium exchange on adsorbed acyl and acyl hydrogenation. The second hump is due to H/D exchange on the adsorbed alkyl species, which then undergoes CO insertion and acyl hydrogenation. The second hump decay is partly due to the reaction with Si–OD as indicated by the parallel decay ofd1- andd2-propionaldehyde and Si–OD.

Vibrational interactions at surfaces: H 2O on Si(100)

The structures and vibrational frequencies of water dissociatively adsorbed on a Si(100)-(2 × 1) surface are investigated by accurate quantum chemical cluster calculations. This Letter addresses the experimentally observed puzzling isotopic shift from the SiOH stretch (825 cm −1) to the SiOD stretch (840 cm −1) measured upon D 2O exposure, which is opposite to the decrease in frequency expected from simple mass arguments. Our calculations show that vibrational interactions between the SiOH stretch and the SiOH bending modes account for all the observed effects.

Effect of pressure on reaction between deuterated water and thin amorphous silica films

Abstract Nuclear reaction analysis has been used to measure deuterium content in SiO2 thin films (224–230 nm) grown in dry oxygen and treated in D2O steam at 700–930°C and 0·22–16 mbar. The deuterium profiles are nearly flat. It is argued that the deuterium is predominantly in the form of Si–OD. The OD concentration does not vary as the square root of the steam pressure, as expected, and saturates above ∼ 7 mbar. This is interpreted in terms of a decrease in the reactivity between water and silica with increasing pressure. We discuss the latter point.

Collection Institut za Narodnu Umjetnost/Institute for Folk Art - Da si od srebra, da si od zlata. Iz vorni glazbeni folklor Hrvatske (‘Were you of silver, were you of gold. Original music folklore of Croatia’). One 12” LP Record. Jugoton LPY-V-739. Selection of the recordings by Dr. Ivan Ivančan and Dr. Jerko Bezić; Yugoslav-English commentaries (3 pp.) by Dr. J.

Collection Institut za Narodnu Umjetnost/Institute for Folk Art - Da si od srebra, da si od zlata. Iz vorni glazbeni folklor Hrvatske (‘Were you of silver, were you of gold. Original music folklore of Croatia’). One 12” LP Record. Jugoton LPY-V-739. Selection of the recordings by Dr. Ivan Ivančan and Dr. Jerko Bezić; Yugoslav-English commentaries (3 pp.) by Dr. J.

Collection Institute for Folk Art, Zagreb - Da si od Srebra, da si od Zlata: Were you of silver, were you of gold. Original Music-Folklore of Croatia. One 12″ LP Record. Jugoton LPY-V-739. Mono. Yugoslavian and English notes by J. Benzič, Dr. I. Ivančan and Dunja Rithman. Zagreb: Institute for Folk Art, 1975.

Collection Institute for Folk Art, Zagreb - Da si od Srebra, da si od Zlata: Were you of silver, were you of gold. Original Music-Folklore of Croatia. One 12″ LP Record. Jugoton LPY-V-739. Mono. Yugoslavian and English notes by J. Benzič, Dr. I. Ivančan and Dunja Rithman. Zagreb: Institute for Folk Art, 1975.

Infrared Absorption Spectra of Silica Gel-H216O, D216O, and H218O Systems

Abstract Infrared absorption spectra of the systems of silica gel - H216O,D216O,H218O, and some organic vapors were measured in order to assign the bands senstive to adsorption at 870 and around 950 cm−1. Deuteration of silica gel caused the absorption decrease at 870 cm−1 and the appearance of a band at 620 cm−1. The band around 950 cm−1 appearing by adsorption not only of water but also of organic vapors showed no shift on deuteration, but shifted toward low frequency side by 25 cm−1 on the substitution of 16O of surface silanol groups with 18O. From these facts the bands at 870, 620 and 950 cm−1 were assgned to Si–OH bending, Si–OD bending and Si–O stretching vibrations of surface silanol groups, respectively. The oxygen atom of silanol groups of silca gel was found to exchange with that of adsorbed water molecules even at room temperature for a sample treated at temperature below 300°C. On the other hand, higher reaction temperature of ca. 200°C was necessary for a sample calcined at 800°C. mechanism of the oxygen atom exchange recation was discussed.