High-pressure H2O Research Articles

Effect of high-pressure H2O treatment on elimination of interfacial GeOX layer between ZrO2 and Ge stack

This investigation demonstrates the effect of high-pressure H2O treatment on the elimination of the interfacial germanium suboxide (GeOX) layer between ZrO2 and Ge. The formation of GeOX interlayer increases the gate-leakage current and worsen the controllability of the gate during deposition or thermal cycles. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy reveal that high-pressure H2O treatment eliminates the interfacial GeOX layer. The physical mechanism involves the oxidation of non-oxidized Zr with H2O and the reduction of GeOX by H2. Treatment with H2O reduces the gate-leakage current of a ZrO2/Ge capacitor by a factor of 1000.

Effects of gate insulator using high pressure annealing on the characteristics of solid phase crystallized polycrystalline silicon thin-film transistors

The oxidizing ambient was built using high pressure H2O vapor at 550 °C. For the solid phase crystallization (SPC) polycrystalline silicon (poly-Si) that is annealed for 1 h at 2 MPa, the oxide thickness is about 150 Å. The oxide layer is approximately 90 Å above the original surface of the poly-Si and 60 Å below the original surface. The oxide layer is used as the first gate insulator layer of thin-film transistors (TFTs). The heating at 550 °C with 2 MPa H2O vapor increased the carrier mobility from 17.6 cm2/V s of the conventional SPC process to 30.4 cm2/V s, and it reduced the absolute value of the threshold voltage (Vth) from 4.13 to 3.62 V. The subthreshold swing also decreased from 0.72 to 0.60 V/decade. This improvement is attributed mainly to the reduction in defect density at the oxide/poly-Si interface and in the poly-Si film by the high pressure annealing (HPA) process. Since the realization of excellent performance at the oxide/poly-Si interface and in poly-Si depends on the defect density, the poly-Si having the thermal oxide formed by a combined process of SPC and HPA may be well suited for fabrication of poly-Si TFTs for flat panel displays such as active matrix organic light emitting diodes.

Improvement in SiO2 Film Properties Formed by Sputtering Method at 150 °C

The quantity of hysteresis phenomena in capacitance response for metal–oxide–semiconductor (MOS) capacitors with 100-nm-thick SiO2 films formed by the sputtering method was reduced by remote oxygen plasma treatment followed by high-pressure H2O vapor heat treatment at 150 °C. In order to determine the quantity of hysteresis phenomena in capacitance response, we defined hysteresis charge as the difference in fixed oxide charge density for round bias voltage application. As-fabricated MOS capacitor samples had a high density of hysteresis charges of 1.0×1012 cm-2. The density of hysteresis charge was not decreased by 4.7×105-Pa-H2O-vapor heat treatment at 150 °C for 3 h. On the other hand, it was markedly reduced to 1.0×1011 cm-2 by 13.56-MHz-radio frequency remote oxygen plasma treatment at 300 W and 150 °C followed by 4.7×105-Pa-H2O-vapor heat treatment at 150 °C for 3 h. Hysteresis phenomena are probably caused by a temporal electron charging up of SiO2 films.

Influence of temperature, composition, silica activity and oxygen fugacity on the H2O storage capacity of olivine at 8 GPa

Olivine crystals were grown in the presence of a hydrous silicate fluid during multi-anvil experiments at 8 GPa and 1,000–1,600°C. Experiments were conducted both in a simple system (FeO–MgO–SiO2–H2O) and in a more complex system containing additional elements (CaO–Na2O–Al2O3–Cr2O3–TiO2–FeO–MgO–SiO2–H2O). Silica activity was buffered by the presence of either pyroxene (high a SiO2) or ferropericlase (low a SiO2), and $$f_{{\text{O}}_{\text{2}} }$$ was buffered by the presence of Ni + NiO or Fe + FeO, or constrained by the presence of Fe2O3. Raman spectroscopy was used to identify pyroxene polymorphs in the run products. Clinoenstatite was present in the 1,000°C experiment, and enstatite in experiments at 1,400–1,520°C. The H2O content of olivine was measured using secondary ion mass spectroscopy, and infrared spectroscopy was used to investigate the nature of hydrous defects. The H2O storage capacity of olivine decreases with increasing temperature at 8 GPa. In contrast to previous experimental results at ≤2 GPa, no significant effect of varying oxygen fugacity is evident, but H2O storage capacity is enhanced under conditions of low silica activity. No significant growth of low wavenumber (<3,400 cm−1) peaks, generally associated with high $$f_{{\text{O}}_{\text{2}} }$$ at low pressure, was observed in the FTIR spectra of olivine from the high $$f_{{\text{O}}_{\text{2}} }$$ experiments. Our experiments show that previous high pressure H2O storage capacity measurements for olivine synthesized under more oxidizing conditions than the Earth’s mantle are not likely to be compromised by the $$f_{{\text{O}}_{\text{2}} }$$ of the experiments. However, the considerable effect of temperature on H2O storage capacity in olivine must be taken into account to avoid overestimation of the bulk upper mantle H2O storage capacity.

Polysilazane Precursor Used for Formation of Oxidized Insulator

ABSTRACTWe report on SiO2 film formation using Polysilazane precursor treated with remote oxygen plasma and high-pressure H2O vapor heating. Polysilazane precursor films with a thickness of 130 nm were formed on silicon substrates by spin coating method. They were annealed at 350°C in remote oxygen plasma at a pressure of 2.0×10−2 Pa and a 13.56×106 Hz radio frequency power of 300 W for 3h followed by 1.3×106-Pa-H2O vapor heating at 260°C for 3 h. Polysilazane precursor films were entirely oxidized by high-pressure H2O vapor heat treatment, and the density of Si-N bonding and Si-H bonding in Polysilazane precursor films were effectively dissociated by the combination of high-pressure H2O vapor heat treatment with remote oxygen plasma treatment. While MOS(Metal-Oxide-semiconductor) capacitors fabricated only by high-pressure H2O vapor heat treatment had a high specific dielectric constant of 6.1, a fixed oxide charge density of 1.3×1012 cm−2 and a density of interface trap of 5.4×1011 cm−2eV−1, the remote oxygen plasma treatment followed by high-pressure H2O vapor heat treatment allowed us to reduce them to 4.1 and 1.6×1011 cm−2, 4.2×1010 cm−2eV−1, respectively.

Modification of SiO&lt;sub&gt;2&lt;/sub&gt;/4H-SiC Interface Properties by High-Pressure H&lt;sub&gt;2&lt;/sub&gt;O Vapor Annealing

We performed high-pressure H2O vapor annealing on 4H-SiC n-MOS capacitors to control SiO2/4H-SiC interface properties. High-pressure H2O annealing was performed at 270～ 420oC at a pressure of 1.31～1.67MPa. Effective negative fixed oxide charge decreased with increasing anneal temperature in the case annealed with Al gate electrodes. However, it increased with increasing anneal temperature in the case annealed without Al gate electrodes. The effect of annealing was much larger on the C-face than that of Si-face. Interface state densities near the conduction band edge was decreased at 420oC under 1.67MPa compared to other samples, especially on the C-face n-MOS capacitors.

Defect Reduction in Polycrystalline Silicon Thin Films by Heat Treatment with High-Pressure H2O Vapor

We investigated defect reduction in laser crystallized polycrystalline silicon (poly-Si) films by heat treatment with 1.3×106 Pa H2O vapor. The H2O vapor heat treatment at 260 °C for 6 h reduced the spin density in laser crystallized poly-Si films from 2.0×1018 (initial) to 6.5×1016 cm-3. The activation energy of the reaction for defect reduction was 0.26 eV. Photoconductivity under 532 nm light illumination at 100 mW/cm2 was increased from 2.7×10-6 (initial) to 3.3×10-5 S/cm by heat treatment for 1 h. The oxygen concentration in the silicon films was increased by 1.1×1019 cm-3 by heat treatment, although the hydrogen concentration was decreased by 1.4×1020 cm-3. This suggests that oxygen atoms have an important role in defect state reduction in polycrystalline silicon films.

Micrometer-scale discharge in high-pressure H2O and Xe environments including supercritical fluid

We generated micrometer-scale discharge in high-pressure H2O and Xe up to supercritical conditions. In our previous paper, we reported the existence of two peculiar features in the breakdown voltages under high-pressure CO2. The first one was the downward shift at the right-hand side of Paschen’s curve above about 2.5MPa, and the second one was the drastic decrease in the breakdown voltages near the critical point. We have experimentally confirmed that these features are also observed in H2O and Xe, even though there are some differences among these materials. Our theoretical fitting involving a density fluctuation term FD agrees well with the experimental results, especially for Xe. We suppose that these unique features are brought about by decreases in the electron-to-particle cross section σ, ionization potential φi, and secondary electron coefficient γ′ and changes in the discharge space.

Improving Water Spray Efficacy for Fire Suppression via CO2 Addition at High Pressures and Low Temperatures: Evidence for CO2 Clathrate Hydrate Formation

This paper describes a technique for achieving a compact aqueous spray that incorporates CO2 into the spray at low temperatures (T < 10 °C) and high pressures (P > 10 MPa). A high-pressure spray apparatus was used to explore the effects of temperature (4−25 °C), nominal CO2 mole fraction (0−0.12), in-line filter pore size (0.5−7 μm), and additives on the high-pressure (12−19 MPa) water spray patterns. Divergence of the high-pressure H2O−CO2 spray was significantly reduced at low temperatures, with addition of sodium lauryl sulfate or aqueous film-forming foam (AFFF), and with a small-pore-size (0.5 μm) filter. The observed trends, based on digital images, can be explained by the formation of CO2 clathrate hydrate within the continuous-flow system. The concepts discussed herein may be applied to conventional H2O/AFFF fire-suppression systems, where the introduction of CO2 as a foaming agent can increase fire-suppression efficacy.

Defect Reduction Treatment for Plasma–Tetraethylorthosilicate–SiO2 by High-Pressure H2O Vapor Heat Treatment

Improvements in the electrical and structural properties of tetraethylorthosilicate (TEOS) SiO2 films fabricated by plasma-enhanced chemical vapor deposition (PECVD) method were investigated using high-pressure H2O vapor heat treatment. The density of interface trap states was reduced from 3.3×1012 (initial) to 5.1×1010 cm-2 eV-1 by 1.3×106 Pa H2O vapor heat treatment at 260°C for 9 h. The density of fixed charges was also reduced from 6.1×1011 to 1.3×1011 cm-2. The full width at half-maximum (FWHM) of the optical absorption band corresponding to vibration of Si–O–Si bonding was reduced from 82.9 to 78.1 cm-1. Narrowing in FWHM of the Si 2p core level peak measured by X-ray photoelectron spectroscopy (XPS) was also observed. The reduction in the FWHM probably results from improvement of the Si–O bonding network.

Improved Optoelectronic Characteristics of Nanocrystalline Porous Silicon by High-Pressure Water Vapor Annealing

ABSTRACTA high-pressure H2O vapor annealing technique has been applied to nanocrystalline porous silicon (PS). The effects on the photoluminescence (PL) are reported here for PS samples of different initial porosities, in different conditions of the annealing pressure. A drastic enhancement of the PL intensity has been achieved, while both the emission band and the peak wavelength remain almost unchanged. The best results have been obtained with an initial PS porosity of about 68 %. The resulting layers consist of Si nanocrystals embedded into an SiO2tissue. The high external quantum efficiency obtained in treated PS (23%) may be attributed mainly to a very high surface passivation by high quality oxide and an enhancement in the localization of photoexcited carriers.

Oxygen plasma and high pressure H 2 O vapor heat treatments used to fabricate polycrystalline silicon thin film transistors

Oxygen plasma and high pressure H2O vapor heat treatment were applied to fabrication of n-channel polycrystalline silicon thin film transistors (poly-Si TFTs). 13.56 MHz-oxygen-plasma treatment at 250 °C, 100 W for 5 min effectively reduced defect states of 25-nm-thick silicon films crystallized by 30 ns-pulsed XeCl excimer laser irradiation. 1.3×106-Pa-H2O vapor heat treatment at 260 °C for 3 h was carried out in order to improve electrical properties of SiOx gate insulators and SiOx/Si interfaces. A carrier mobility of 470 cm2/V s and a low threshold voltage of 1.8 V were achieved for TFTs fabricated with crystallization at 285 mJ/cm2.

The role of H2O during crystallization of primitive arc magmas under uppermost mantle conditions and genesis of igneous pyroxenites: an experimental study

Exposed, subduction-related magmatic arcs commonly include sections of ultramafic plutonic rocks that are composed of dunite, wehrlite, and pyroxenite. In this experimental study we examined the effects of variable H2O concentration on the phase proportions and compositions of igneous pyroxenites and related ultramafic plutonic rocks. Igneous crystallization experiments simulated natural, arc magma compositions at 1.2 GPa, corresponding to conditions of the arc lower crust. Increasing H2O concentration in the liquid changes the crystallization sequence. Low H2O concentration in the liquid stabilizes plagioclase earlier than garnet and amphibole while derivative liquids remain quartz normative. Higher H2O contents (>3%) suppress plagioclase and lead to crystallization of amphibole and garnet thereby producing derivative corundum normative andesite liquids. The experiments show that alumina in the liquid correlates positively with Al in pyroxene, as long as no major aluminous phase crystallizes. Extrapolation of this correlation to natural pyroxenites in the Talkeetna and Kohistan arc sections indicates that clinopyroxenes with low Ca-Tschermaks component represent near-liquidus phases of primitive, Si-rich hydrous magmas. Density calculations on the residual solid assemblages indicate that ultramafic plutonic rocks are always denser than upper mantle rocks in the order of 0.05 to 0.20 g/cm3. The combination of high pressure and high H2O concentration in the liquid suppresses plagioclase crystallization, so that ultramafic plutonic rocks form over a significant proportion of the crystallization interval (up to 50% crystallization of ultramafic rocks from initial, mantle-derived liquids). This suggests that in subduction-related magmatic arcs the seismic Moho might be shallower than the petrologic crust/mantle transition. It is therefore possible that calculations based on seismic data have overestimated the normative plagioclase content (e.g., SiO2, Al2O3) of igneous crust in arcs.

Improvement In Electrical Properties of Polycrystalline Silicon Films by The H2O Vapor Annealing Method

ABSTRACTImprovement of electrical properties by heat treatment with high-pressure H2O vapor was discussed for 7.4×1017cm−3 phosphorus-doped pulsed laser crystallized silicon films. The analysis of the electrical conductivity resulted in that 1.3×106-Pa-H2O vapor annealing at 270°C for 3 h reduced the density of defect states from 5.5 ×1018 cm−3(as crystallized) to 5.0×1017 cm−3 for tail states and from 1.0×1018 cm−3(as crystallized) to 3.0×1017 cm−3 for deep level defect states. The potential barrier height at grain boundaries decreased from 0.34 eV (as crystallized) to 0.05 eV by the heat treatment. The combination of oxygen plasma with high-pressure H2O vapor annealing effectively reduced the densities of defect tail sates as well as deep level defect states. It achieved a high performance of thin film transistors with a threshold voltage of 1.3 V and an effective mobility of 160 cm2/Vs.

Heat Treatment with High-Pressure H2O Vapor of Pulsed Laser Crystallized Silicon Films

Improvement of electrical properties for 7.4 ×1017 cm-3 phosphorus-doped pulsed laser crystallized silicon films of 50 nm thickness formed on quartz glass substrates was achieved by heat treatment with high-pressure H2O vapor. The electrical conductivity was increased from 1.3 ×10-5 S/cm (as-crystallized) to 2 S/cm by annealing at 270°C for 3 h with 1.3 ×106 Pa H2O vapor. The spin density of undoped laser crystallized silicon films was reduced from 1.6 ×1018 cm-3 (as-crystallized) to 1.2 ×1017 cm-3 by annealing at 310°C for 3 h with 1.3 ×106 Pa H2O vapor. Theoretical analysis revealed that the potential barrier height at grain boundaries decreased from 0.3 eV (as-crystallized) to 0.002 eV. High-pressure H2O vapor annealing offer the possibility of reducing the density of defects states through oxidation of the defects at low temperature.

Passivation of SiO2/Si Interfaces Using High-Pressure-H2O-Vapor Heating

High-pressure H2O vapor heating was used for the passivation of silicon surface. The thermally evaporated SiOx films formed on the silicon surface was oxidized and Si–O bonding density increased with an activation energy of 0.035 eV with increasing heating temperature upon heat treatment with 1.0 ×106 Pa H2O vapor. The peak wave number and full width at half maximum of the Si–O absorption band due to the Si–O–Si antisymmetric stretching vibration mode were changed to 1077 cm-1 and 72 cm-1, respectively. The density of silicon dangling bonds was reduced from 2.0 ×1017(as deposited) to 1.4 ×1015 cm-3 by heat treatment. The effective surface recombination velocity of the p-type silicon wafer that was coated with SiOx films was markedly reduced from 405 cm/s (as deposited) to 13 cm/s by heat treatment with 2.1 ×106 Pa-H2O vapor at 260°C for 3 h. The interfaces retained the low recombination velocity 8000 h after keeping the sample in air. Effective field effect passivation was demonstrated using a SiOx/SiO2 double layered structure formed by the combination of thermal evaporation and heat treatment with high-pressure H2O vapor.

Defect reduction and surface passivation of SiO 2 /Si by heat treatment with high-pressure H 2 O vapor

Heat treatment with high-pressure H2O vapor was applied to improve interface properties of SiO2/Si and passivate the silicon surface. Heat treatment at 180–420 °C with high-pressure H2O vapor changed SiOx films, 150 nm thick formed at room temperature by thermal evaporation in vacuum, into SiO2 films with a Si-O-Si bonding network similar to that of thermally grown SiO2 films. Heat treatment at 130 °C with 2.8×105 Pa H2O for 3 h reduced the recombination velocity for the electron minority carriers from 405 cm/s (as-fabricated 150-nm-thick SiOx/Si) to 5 cm/s. Field-effect passivation was demonstrated by an additional deposition of defective SiOx films on the SiO2 films formed by heat treatment at 340 °C with high-pressure H2O vapor. The SiOx deposition reduced the recombination velocity from 100 cm/s to 48 cm/s.

Heat Treatment of Amorphous and Polycrystalline Silicon Thin Films with High-Pressure H2O Vapor

Changes in electrical and optical properties induced by heat treatment with high-pressure H2O vapor are discussed for low pressure chemical-vapor deposited amorphous silicon (LPCVD a-Si) and laser-crystallized polycrystalline silicon films. Heat treatment at 190°C with ∼1 ×106-Pa-H2O vapor reduced the dark conductivity to ∼10-11 S/cm and increased the photoconductivity to ∼10-7 S/cm. The photoconductivity was also increased for laser-crystallized polycrystalline silicon films. Optical absorption in the photon energy range lower than 1.5 eV was reduced for the a-Si films. Heat treatment at 190–270°C resulted in a minimal change in optical band gap, which was 1.50 ±0.02 eV for the LPCVD a-Si. The increase in hydrogen concentration was less than 2 ×1020 cm-3 after the treatment for the amorphous and polycrystalline silicon films. These results show that the heat treatment with high-pressure H2O vapor can reduce the defect density in the silicon films at low temperatures.

Structural and Electronic Properties of Laser Crystallized Silicon Films

AbstractFundamental properties of silicon films crystallized by a 30-ns-pulsed XeCI excimer laser were discussed. Although crystallization of 50-nm thick silicon films formed on quartz substrates occurred through laser hearing at the crystalline threshold energy density of 160 mJ/cm2, a higher laser energy density at 360 mJ/cm2 was necessary to crystallize silicon films completely. Analyses of free carrier optical absorption revealed that phosphorus-doped silicon films with a carrier density about 2×1020 cm−3 had a high carrier mobility of 20 cm2/Vs for irradiation at the crystallization threshold energy density, while Hall effect measurements gave a carrier mobility of electrical current traversing grain boundaries of 3 cm2/Vs. This suggested that the crystalline grains had good electrical properties. As the laser energy density increased to 360 mJ/cm2 and laser pulse number increased to 5, the carrier mobility obtained by the Hall effect measurements markedly increased to 28 cm2/Vs because of improvement of grain boundary properties, while the carrier mobility obtained by analysis of free carrier absorption increased to 40 cm2/Vs. A post annealing method at 190°C with high-pressure H2O vapor was developed to reduce the density of defect states. Increase of carrier mobility to 500 cm2/Vs was demonstrated in the polycrystalline silicon thin film transistors fabricated in laser crystallized silicon films.

Preparation and fusion properties of protoplasts from mature pollen of Nicotiana tabacum

A method to remove the exine from mature tobacco pollen and to release numerous intact pollen protoplasts has been developed. Post-anthesis binucleate pollen was treated with water, buffered with MES at pH 5.5, for two hours. Rupture of the exine was caused by the force of pollen hydration exposing the intine to subsequent enzymatic maceration. The high osmotic pressure (1000 mOsm·kg(-1) H2O) of pollen protoplasts required a special maceration medium, 4% KCl (w/v). Action of an enzyme solution containing 1% (w/v) Macerozyme and 1% (w/v) Cellulase gave rise to viable protoplasts within 4 hours. When cultured in a tobacco mesophyll protoplast culture medium, the pollen protoplasts underwent regeneration of a cell wall, formation of various tube-shaped structures, and division of the generative nucleus into two nuclei. Using a PEG/Ca(2+) method pollen protoplasts were fused with diploid mesophyll protoplasts. Evidence of transfer of chloroplasts into the pollen protoplasts was observed after one day of culture.