Low Hydrogen Content Research Articles

21.3: 4.0 In. QVGA AMOLED Display Using In‐Ga‐Zn‐Oxide TFTs with a Novel Passivation Layer

AbstractWe have developed a 4.0 inch QVGA AMOLED display using amorphous In‐Ga‐Zn‐Oxide TFTs, focusing on a passivation layer. Threshold voltage of the TFTs can be controlled to have “normally off” characteristics by using SiOx with a low hydrogen content. Besides, small subthreshold swing and high saturation mobility are obtained.

Structural evolution of nanocrystalline silicon thin films synthesized in high-density,low-temperature reactive plasmas

Silicon thin films with a variable content of nanocrystalline phase weredeposited on single-crystal silicon and glass substrates by inductively coupledplasma-assisted chemical vapor deposition using a silane precursor withoutany hydrogen dilution in the low substrate temperature range from 100 to300 °C. The structural and optical properties of the deposited films are systematicallyinvestigated by Raman spectroscopy, x-ray diffraction, Fourier transform infraredabsorption spectroscopy, UV/vis spectroscopy, scanning electron microscopyand high-resolution transmission electron microscopy. It is shown that thestructure of the silicon thin films evolves from the purely amorphous phase to thenanocrystalline phase when the substrate temperature is increased from 100 to150 °C. It is found that the variations of the crystalline fractionfc, bonded hydrogencontent CH, optical bandgapETauc, film microstructureand growth rate Rd are closely related to the substrate temperature. In particular, at a substrate temperature of300 °C, the nanocrystalline Si thin films of our interest feature a high growth rate of1.63 nm s−1, a low hydrogen content of 4.0 at.%, a high crystalline fraction of 69.1%, a low opticalbandgap of 1.55 eV and an almost vertically aligned columnar structure with a mean grainsize of approximately 10 nm. It is also shown that the low-temperature synthesis ofnanocrystalline Si thin films without any hydrogen dilution is attributed to the outstandingdissociation ability of the high-density inductively coupled plasmas and effectiveplasma–surface interactions during the growth process. Our results offer a highlyeffective yet simple and environmentally friendly technique to synthesize high-qualitynanocrystalline Si films, vitally needed for the development of new-generation solar cellsand other emerging nanotechnologies.

Growth behavior of hydrogen micropores in aluminum alloys during high-temperature exposure

X-ray microtomography was used to observe hydrogen micropores and their growth behavior at high temperatures in several aluminum alloys. High-density micropores were observed in high-purity Al–Mg alloys, but their density and volume fraction were much lower in pure aluminum. Our results have revealed that the growth behavior of micropores is dominated by Ostwald ripening. About 53% of hydrogen is trapped in micropores in Al–Mg alloy with low hydrogen content, making micropores the predominant hydrogen trap site. Although total hydrogen content is similar to that in the alloy, the ratio of hydrogen trapped in micropores is below 7% in pure aluminum. This difference is attributable to the lack of hydrogen precipitation sites in pure aluminium. Although the overall amounts of hydrogen at dislocations and grain boundaries are small in all the materials, the occupancies for these trap sites were concluded to be very high.

Hydrogen-rich gas from catalytic steam gasification of biomass in a fixed bed reactor: Influence of temperature and steam on gasification performance

The catalytic steam gasification of biomass was carried out in a lab-scale fixed bed reactor in order to evaluate the effects of temperatures and the ratio of steam to biomass ( S/ B) on the gasification performance. The bed temperature was varied from 600 to 900 and the S/ B from 0 to 2.80. The results show that higher temperature contributes to more hydrogen production. The introduction of steam improves the dry gas yield and carbon conversion efficiency. But excessive steam will lower hydrogen content and degrade fuel gas quality. As S/ B are 2.10, the hydrogen content reach the maximum, up to 52.7%.

Precursor Cat-CVD a-Si films for the formation of high-quality poly-Si films on glass substrates by flash lamp annealing

Amorphous Si (a-Si) films with lower hydrogen contents show better adhesion to glass during flash lamp annealing (FLA). The 2.0 µm-thick a-Si films deposited by plasma-enhanced chemical vapor deposition (PECVD), containing 10% hydrogen, start to peel off even at a lamp irradiance lower than that required for crystallization, whereas a-Si films deposited by catalytic CVD (Cat-CVD) partially adhere even after crystallization. Dehydrogenated Cat-CVD a-Si films show much better adhesion to glass, and are converted to polycrystalline Si (poly-Si) without serious peeling, but are accompanied by the generation of crack-like structures. These facts demonstrate the superiority of as-deposited Cat-CVD a-Si films as a precursor material for micrometer-thick poly-Si formed by FLA.

Influence of fillers on hydrogen penetration properties and blister fracture of rubber composites for O-ring exposed to high-pressure hydrogen gas

Ethylene–propylene rubber (EPDM) and nitrile–butadiene rubber (NBR) composites having carbon black, silica, and no fillers were exposed to hydrogen gas at a maximum pressure of 10 MPa; then, blister tests and the measurement of hydrogen content were conducted. The hydrogen contents of the composites were proportional to the hydrogen pressure, i.e., the behavior of their hydrogen contents follows Henry's law. This implies that hydrogen penetrates into the composite as a hydrogen molecule. The addition of carbon black raised the hydrogen content of the composite, while the addition of silica did not. Based on observations, the blister damages of composites with silica were less pronounced, irrespective of the hydrogen pressures. This may be attributed to their lower hydrogen content and relatively better tensile properties than the others.

Rapid, low-temperature synthesis of nc-Si in high-density, non-equilibrium plasmas: enabling nanocrystallinity at very low hydrogen dilution

Nanocrystalline silicon thin films were deposited on single-crystal silicon and glass substrates simultaneously by inductively coupled plasma-assisted chemical vapor deposition from the reactive silane reactant gas diluted with hydrogen at a substrate temperature of 200 °C. The effect of hydrogen dilution ratio X (X is defined as the flow rate ratio of hydrogen to silane gas), ranging from 1 to 20, on the structural and optical properties of the deposited films, is extensively investigated by Raman spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/VIS spectroscopy, and scanning electron microscopy. Our experimental results reveal that, with the increase of the hydrogen dilution ratio X, the deposition rate Rd and hydrogen content CH are reduced while the crystalline fraction Fc, mean grain size δ and optical bandgap ETauc are increased. In comparison with other plasma enhanced chemical vapor deposition methods of nanocrystalline silicon films where a very high hydrogen dilution ratio X is routinely required (e.g. X > 16), we have achieved nanocrystalline silicon films at a very low hydrogen dilution ratio of 1, featuring a high deposition rate of 1.57 nm/s, a high crystalline fraction of 67.1%, a very low hydrogen content of 4.4 at.%, an optical bandgap of 1.89 eV, and an almost vertically aligned columnar structure with a mean grain size of approximately 19 nm. We have also shown that a sufficient amount of atomic hydrogen on the growth surface essential for the formation of nanocrystalline silicon is obtained through highly-effective dissociation of silane and hydrogen molecules in the high-density inductively coupled plasmas.

Alloying effects of Ru and W on the resistance to hydrogen embrittlement and hydrogen permeability of niobium

The alloying effects of ruthenium and tungsten on the hydrogen solubility, the resistance to hydrogen embrittlement and the hydrogen permeability are investigated for Nb–M (M = Ru and W) alloys. The hydrogen solubility decreases by alloying and also by increasing the temperature of the alloy. As a result, the resistance to hydrogen embrittlement is improved owing to the low hydrogen content in the alloy. On the other hand, the hydrogen flux increases with increasing hydrogen concentration difference, Δ C, between the inlet and outlet sides of the alloy membrane. It is found that Nb–5 mol%X (X = Ru and W) alloys possess excellent hydrogen permeability without showing any hydrogen embrittlement when used under the appropriate permeation conditions of the temperatures and hydrogen pressures.

Observations of nanoscopic, face centered cubic Ti and TiH x

Transmission electron microscopy has been used to study ball milled and H cycled NaAlH4 with 10 mol% TiCl3. Isolated from the main phases in this hydrogen storage system, nanocrystalline aggregates of fcc TiH x (0≤x<0.67) were found. The value of x was determined based on the assumption of a linear increase of the TiH x lattice parameter by increasing H content. The size of the TiH x crystallites was in the range 10 to 20 nm, and the lattice parameter decreased from 4.22 A in TiH0.67 to 4.10 A in pure fcc Ti. Non-equilibrium ball milling and subsequent H cycling in combination with a small crystallite size are believed to make the TiH x phase stable. The present results are the first observations of fcc TiH x with low hydrogen content, and the measured fcc lattice parameter of Ti matches first-principles calculations.

Sub-45 nm SiO2 Etching with Stacked-Mask Process Using High-Bias-Frequency Dual-Frequency-Superimposed RF Capacitively Coupled Plasma

By using a stacked mask process (S-MAP) with spun-on-carbon (SOC) film, 38 nm line patterns were successfully etched by controlling the ion energy using high-bias-frequency dual-frequency-superimposed (DFS) rf capacitively coupled plasma in combination with the low hydrogen content SOC film. It was found that ions with higher energy enhance the fluorination of SOC and induce pattern wiggling under fluorine exposure. By using a higher bias frequency to control the ion energy distribution and reduce the maximum ion energy, the SOC pattern wiggling was effectively suppressed.

Effects of a Thermal CVD SiN Passivation Film on AlGaN/GaN HEMTs

In AlGaN/GaN high electron mobility transistors (HEMTs), drain current reduction by current collapse phenomenon is a big obstacle for a high efficient operation of power amplifier application. In this study, we investigated the effects of SiN passivation film quality on the electrical characteristics of AlGaN/GaN HEMTs. First, we conducted some experiments to investigate the relationship between electrical characteristics of AlGaN/GaN HEMTs and various conditions of SiN passivation film by plasma enhanced chemical vapor deposition (PE-CVD). We found that both gate current leakage and current collapse were improved simultaneously by SiN passivation film deposited by optimized condition of NH3 and SiH4 gas flow. It is found that the critical parameter in the optimization is a IN-H/ISi-H ratio measured by Fourier transforms infrared spectroscopy (FT-IR) spectra. Next, a thermal CVD SiN was applied to the passivation film to be investigated from the same point of view, because a thermal CVD SiN is well known to have good quality with low hydrogen content and high IN-H/ISi-H ratio. We confirmed that the thermal CVD SiN passivation could improve much further both of the gate leakage current and the current collapse in AlGaN/GaN-HEMTs. Furthermore, we tried to apply the thermal CVD SiN to the gate insulator in MIS (Metal Insulator Semiconductor) structure of AlGaN/GaN HEMTs. The thermal CVD SiN passivation was more suitable for the gate insulator than PE-CVD SiN passivation in a view of reducing current collapse phenomena. It could be believed that the thermal CVD SiN film is superior to the PE-CVD SiN film to achieve good passivation and gate insulator film for AlGaN/GaN HEMTs due to the low hydrogen content and the high IN-H/ISi-H ratio.

Hydrogen Embrittlement Behavior of High Mn TRIP/TWIP Steels

The hydrogen embrittlement susceptibility of high strength TRIP/TWIP steels with the tensile strength of 600Mpa to 900Mpa grade was investigated using cathodically hydrogen charged specimens. TWIP steels with full austenite structure show a lower hydrogen content than do TRIP steels. The uniform distribution of strong traps throughout the matrix in the form of austenite is considered beneficial to reduce the hydrogen embrittlement susceptibility of TWIP steels. Moreover, an austenite structure with very fine deformation twins formed during straining could also improve the ductility and reduce notch sensitivity. In Ubend and deep drawing cup tests, TWIP steels show a good resistance to hydrogen embrittlement compared with TRIP steels.

Influence of hydrogen dilution on structural, electrical and optical properties of hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared by plasma enhanced chemical vapour deposition (PE-CVD)

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited from pure silane (SiH 4) and hydrogen (H 2) gas mixture by conventional plasma enhanced chemical vapour deposition (PE-CVD) method at low temperature (200 °C) using high rf power. The structural, optical and electrical properties of these films are carefully and systematically investigated as a function of hydrogen dilution of silane ( R). Characterization of these films with low angle X-ray diffraction and Raman spectroscopy revealed that the crystallite size in the films tends to decrease and at same time the volume fraction of crystallites increases with increase in R. The Fourier transform infrared (FTIR) spectroscopic analysis showed at low values of R, the hydrogen is predominantly incorporated in the nc-Si:H films in the mono-hydrogen (Si H) bonding configuration. However, with increasing R the hydrogen bonding in nc-Si:H films shifts from mono-hydrogen (Si H) to di-hydrogen (Si H 2) and (Si H 2) n complexes. The hydrogen content in the nc-Si:H films decreases with increase in R and was found less than 10 at% over the entire studied range of R. On the other hand, the Tauc's optical band gap remains as high as 2 eV or much higher. The quantum size effect may responsible for higher band gap in nc-Si:H films. A correlation between electrical and structural properties has been found. For optimized deposition conditions, nc-Si:H films with crystallite size ∼7.67 nm having good degree of crystallinity (∼84% ) and high band gap (2.25 eV) were obtained with a low hydrogen content (6.5 at%). However, for these optimized conditions, the deposition rate was quite small (1.6 Å/s).

A hard graphitelike hydrogenated amorphous carbon grown at high deposition rate (&gt;15nm∕s)

Hard graphitelike hydrogenated amorphous carbon with distinct infrared absorption spectra in the C–Hx stretching region is reported. These spectra are characterized by two separated peaks corresponding predominantly to sp3 CH and sp2 CH stretching modes and reveal a distinct absence of endgroups (sp2 CH2 and sp3 CH3). The relatively dense films (∼2.1g∕cm3) have low hydrogen content (∼20%), high refractive index (∼2.4 at 3μm), nanohardness exceeding 16GPa, and a characteristic optical dispersion relation. These films are deposited at growth rates >15nm∕s, in the absence of high-energy ion bombardment, indicating the importance of the specific Ar–C2H2 chemistry of the remote plasma used.

Antifoaming performance of polysiloxanes modified with fluoroalkyls and polyethers

AbstractA series of polysiloxanes modified with fluoroalkyls and polyethers were synthesized. Antifoaming performance of such modified polysiloxanes in the mixture of diesel and mobile fuel was studied. The effects of factors such as polyethers type, molar ratio between polyether and fluoroalkyl, hydrogen‐contents and viscosity of polysiloxanes, length of fluoroalkyls, etc., on the performance of modified products were discussed. It shows that polysiloxane modified with allyl polyoxypropylene ether and hexafluorobutyl acrylate has better breaking and inhibiting foam performance, when compared with that replacing allyl polyoxypropylene ether with allyl polyoxyethylene polyoxypropylene block ether and allyl polyoxyethylene ether. And when the molar ratio between allyl polyoxypropylene ether and hexafluorobutyl acrylate is 3 : 7, modified polysloxane has the best foam controlling performance. Low viscosity polysiloxane or low hydrogen content polysiloxane modified with allyl polyoxypropylene ether and hexafluorobutyl acrylate has better foam controlling performance. Polysiloxane modified with longer carbon chain fluoroalkyl and allyl polyoxypropylene ether has better antifoaming performance than that modified with shorter carbon chain fluoroalkyl and polyether and lower surface tension. The change of surface tension of foaming liquid between initially added with modified polysiloxane and after testing antifoaming performance was studied, and it shows that after testing performance of antifoam, the surface tension of foaming liquid becomes bigger which is one possible reason for antifoam exhausting. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation of various DLC films by T-shaped filtered arc deposition and the effect of heat treatment on film properties

Different types of diamond-like carbon (DLC) films (ta-C, a-C, ta-C:H and a-C:H) were prepared on super hard alloy (WC-Co) substrate using a T-shape filtered arc deposition (T-FAD) system. At first, the film properties, such as structure, hydrogen content, density, hardness, elastic modulus, were measured. Ta-C prepared with a DC bias of −100 V showed the highest density (3.1 g/cm 3) and hardness (70–80 GPa), and the lowest hydrogen content (less than 0.1 at. %). It was found that the hardness of the DLC film is proportional to approximately the third power of film density. The DLC films were then heated for 60 min in an electric furnace at 550 °C in N 2. Only the ta-C film hardly change its structure, although other films were graphitized. The 200-nm thick ta-C film was then heated for 60 min through the temperature range from 400 to 800 °C in N 2 with 2 vol.% of O 2 and the film structure found to be stable up to 700 °C. The substrate was oxidized at 800 °C, indicating the ta-C film had a thermal barrier function up to that temperature.

Characteristics of hydrogen co-doped ZnO : Al thin films

ZnO films co-doped with H and Al (HAZO) were prepared by sputtering ZnO targets containing 1 wt% Al2O3 on Corning glass at a substrate temperature of 150 °C with Ar and H2/Ar gas mixtures. The effects of hydrogen addition to Al-doped ZnO (AZO) films with low Al content on the electrical, the optical and the structural properties of the as-grown films as well as the vacuum- and air-annealed films were examined. Secondary ion mass spectroscopy analysis showed that the hydrogen concentration increased with increasing H2 in sputter gas. For the as-deposited films, the free carrier number increased with increasing H2. The Hall mobility increased at low hydrogen content, reaching a maximum before decreasing with a further increase of H2 content in sputter gas. Annealing at 300 °C resulted in the removal of hydrogen, causing a decrease in the carrier concentration. It was shown that hydrogen might exist as single isolated interstitial hydrogen bound with oxygen, thereby acting like an anionic dopant. Also, it was shown that the addition of hydrogen to ZnO films doped with low metallic dopant concentration could yield transparent conducting films with very low absorption loss as well as with proper electrical properties, which is suitable for thin film solar cell applications.

Towards Designing Stable Pd‐Based Membranes for Hydrogen Gas Separation: A Statistical Thermodynamics Approach

AbstractA method to design new, not yet synthesized, multicomponent alloys based on knowledge of binary alloys is applied to develop Pd‐alloys for membranes for gas separation. The approach couples the cluster variation method with effective pair potentials to describe the phase boundaries between theα‐solid solution (low hydrogen content) andβ‐hydride phases. The calculations illustrate (i) that the method can predictα − βphase boundaries of hydrogen in binary and ternary Pd‐alloys, (ii) how the relative interaction strengths of filled and empty interstitial sites influence the width of the miscibility gap, (iii) that the hydrogen absorption capacity of an alloy is related to the hydride phase stability and (iv) the presence of short range order of hydrogen inβ‐hydrides.

Redeposition of amorphous hydrogenated carbon films during thermal decomposition

Thermally induced decomposition of hard and soft amorphous hydrocarbon films was investigated by thermal effusion spectroscopy. Released species were detected by a sensitive quadrupole mass spectrometer using two different experimental setups for thermal effusion. Species released in a molecular beam setup were detected in direct line of sight to the sample surface, while species released in a remote UHV oven had no direct line of sight to the mass spectrometer. Soft, hydrogen-rich carbon films exhibit a desorption maximum at T≈740K while hard films with a low hydrogen content have their maximum at T≈870K. Additionally, the spectrum of released species differs dramatically between hard and soft films. We found a significant redeposition of species released from soft films. From the redeposited fraction of material we estimated an average redeposition probability of about 50% for species released from soft films.

Preparation and Property of Electrodeposited Zn-Fe-SiO&lt;sub&gt;2&lt;/sub&gt; Composite Coating

Electrodeposited Zn and Zn-Fe alloy have been applied widely to protect steel from corrosion, but the property of coating still needs to be improved. In this paper, Zn-Fe-SiO2 composite coatings are electrodeposited from Zn-Fe alloy electrolyte containing SiO2 particles. Zinc based coatings with Fe% &gt;1%(mass) are deposited from sulfate bath, and coatings with Fe% &lt;1%(mass) are deposited from chloride bath. Particle content in the composite coating generally increases with particle concentration under an adequate agitation and then tends to saturation. The optimum particle content in the composite coating is 0.5%(mass). Corrosion resistance, porosity, hydrogen embrittlement and surface morphology of Zn-Fe-SiO2 composite coatings have been tested and compared with electrodeposited Zn and Zn-Fe alloy. The data implies that Zn-Fe-SiO2 composite coating has the best corrosion resistance, lowest porosity, lowest hydrogen content and the finest crystal. All the results show that Zn-Fe-SiO2 composite coating is satisfactory to be used as anti-corrosion material for steel and has a great future in application.