Temperature Thermal Oxidation Research Articles

Ethanol Sensing Characteristics of ZnO Nanostructures Impregnated by Gold Colloid

ZnO nanostructures were synthesized by thermal oxidation reaction from zinc powder and then impregnated by gold colloid. The gold colloid was prepared by chemical reduction technique and had red color. The heating temperature and sintering time of thermal oxidation were 700 °C and 24 hours, respectively under oxygen atmosphere. The morphology of ZnO nanostructures and ZnO impregnated gold colloid were studied by field emission scanning electron microscope (FE-SEM). The diameter and length of pure ZnO and ZnO impregnated gold colloid were about the same value and were in the range of 100-500 nm and 2.0-7.0 µm, respectively. The ethanol sensing properties of ZnO impregnated by gold colloid were tested in ethanol atmosphere at ethanol concentrations of 1000 ppm and at an operating temperature of 260-360 °C. It was found that the sensitivity and response time were improved for gold impregnated sensor with an optimum operating temperature of 300°C due to the enhanced reaction between the ethanol and the adsorbed oxygen at an optimum temperature.

Thermal stability and oxidation behavior of Al-containing nanocrystalline powders produced by cryomilling

Al-containing nanostructured coatings provide excellent protection from high temperature corrosion. Aluminum oxide scales generally provide better oxidation resistance and yield lower oxidation rates than other oxide scale compositions. In this study, nanocrystalline 316L stainless steel containing 6 wt.% Al was synthesized using cryogenic milling (cryomilling). Complete alloying was obtained after 32 h of milling and the average grain size was found to be 7 nm. High temperature thermal stability and oxidation kinetics of the alloyed powders were examined. The powder demonstrated good grain growth stability at 500 °C, at which point, the powders had been heat treated for 120 h and the average grain size was found to be 11.4 nm. The oxidation kinetics of the powder were studied for 48 h at 500, 800, and 1,000 °C, respectively. For comparison, conventional 316LSS powder was also tested. Nanocrystalline 316LSS-6 wt.% Al showed lower weight gain than the conventional 316LSS powders. During the oxidation of nanocrystalline 316LSS-6 wt. % Al at 500 °C, protective aluminum oxide scale formed at the surface. At 800 °C and 1,000 °C, most of the nanocrystalline 316LSS-6 wt.% Al particles showed completed outer aluminum oxide scale. However, at 800 and 1,000 °C, some particles showed growth of chromium oxide scale underneath the aluminum oxide scale. In those samples, Al depletion was also observed due to a non-homogenous distribution of Al during cryomilling. The activation energy of the oxidation reaction was calculated and was found to be affected by the enhancement of the grain boundary diffusion in nanostructured particles.

Structural, optical and electrochromic properties of nickel oxide thin films grown from electrodeposited nickel sulphide

Nickel oxide thin films were grown onto FTO-coated glass substrates by a two-step process: electrodeposition of nickel sulphide and their thermal oxidation at 425, 475 and 525 °C. The influence of thermal oxidation temperature on structural, optical, morphological and electrochromic properties was studied. The structural properties undoubtedly revealed NiO formation. The electrochromic properties were studied by means of cyclic voltammetry. The films exhibited anodic electrochromism, changing from a transparent state to a coloured state at +0.75 V versus SCE, i.e. by simultaneous ion and electron ejection. The transmittance in the coloured and bleached states was recorded to access electrochromic quality of the films. Colouration efficiency and electrochromic reversibility were found to be maximum (21 mC/cm 2 and 89%, respectively) for the films oxidized at 425 °C. The optical band gap energy of nickel oxide slightly varies with increase in annealing temperature.

Visible Light Active Carbon Modified (CM)-p-WO3 Thin Film Electrodes for Photosplitting of Water

Carbon modified p-type tungsten oxide (CM-p-WO3) photoelectrodes were synthesized by flame oxidation of tungsten metal sheets (Alfa Co. 0.25 mm thick) at several temperatures for different lengths of time. The photocatalytic activity of CM-p-WO3 was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density, jp. Carbon modified tungsten oxide photoelectrodes exhibited p-type photoresponse in acidic medium of 0.5 M H2SO4. The highest photocurrent density of 2.08 mA cm-2 was observed under illumination intensity of 80 mW cm-2 from a 150 Watt (Kratos Model LH 150/1) Xenon arc lamp at an optimal thermal oxidation temperature of 900 {degree sign}C for15 min at applied potential of -0.4 V vs Eaoc. These CM-p-WO3 photoelectrodes were found to generate highest photoconversion efficiency of 2.16 % for photosplitting of water.

Thermal oxidation temperature dependence of 4H-SiC MOS interface

The thermal oxidation temperature dependence of 4H-silicon carbide (SiC) is systematically investigated using X-ray photoelectron spectroscopy (XPS) and capacitance–voltage ( C– V) measurements. When SiC is thermally oxidized, silicon oxycarbides (SiC x O y ) are first grown and then silicon dioxide (SiO 2) is grown. It is identified by XPS that the SiO 2 films fall into two categories, called SiC-oxidized SiO 2 and Si-oxidized SiO 2 in this paper. The products depend on thermal oxidation temperature. The critical temperature is between 1200 and 1300 °C. The interface trap density ( D it) of the sample possessing Si-oxidized SiO 2, at thermal oxidation temperature of 1300 °C, is lower than SiC-oxidized SiO 2 at and below 1200 °C, suggesting that a decrease of the C component in SiO 2 film and SiO 2/SiC interface by higher oxidation temperature improves the metal-oxide–semiconductor (MOS) characteristics.

P-type tin–indium oxide films prepared by thermal oxidation of metallic InSn alloy films

P-type transparent conducting tin–indium oxide (TIO) films were successfully fabricated on quartz substrates by thermal oxidation of InSn alloy (In / Sn = 0.2) films that were deposited by magnetron sputtering at room temperature (R.T.). Structural and electrical properties of TIO films were investigated. X-ray diffraction studies showed that all TIO films were polycrystalline with an orthorhombic structure. The surface morphology of TIO films viewed by field emission scanning electron microscope (SEM) revealed that the films are composed of uniformly distributed submicron grains. Hall effect measurement results indicated that hole concentration as high as 9.61 × 10 18 cm − 3 was achieved. It's found that 600 °C was the optimum thermal oxidation temperature to get p-type TIO films with highest hole concentration.

Properties of Thermal Gadolinium Oxide Films on Silicon

The formation and electrical characteristics of thermal gadolinium (Gd) oxide films were investigated. A good uniform interface formed by proper treatment was observed by transmission electron microscopy (TEM) examination. The dielectric constant of the thermal Gd oxide films was approximately 10 from capacitance–voltage measurements. The X-ray diffraction (XRD) pattern of the thermal Gd oxide (Gd2O3) films showed that they had a cubic structure. The Gd oxides that were oxidized at higher temperatures exhibited smaller grain boundaries than those oxidized at lower temperatures. The grain boundary size of the Gd oxides significantly affects the leakage property. A good Gd oxide quality can be obtained when the thermal oxidation temperature is above 900°C.

Preparation and property control of nano-sized indium tin oxide particle

Indium tin oxide (ITO) particles of 20–30 nm in diameter, which would be used as coating material for electromagnetic wave shield, were synthesized by co-precipitation of indium chloride and tin chloride. Size and shape of particles were controlled by pH of co-precipitation solution, thermal oxidation temperature and tin contents. The prepared particles were thermally reduced under hydrogen gas to control electrical properties. When the solution pH was 6.75, plate type of particles with 60 nm size was coexisted with spherical particles of 20 nm size and the part of crystal structure was hexagonal. As pH was increased, plate type of particles was disappeared and 20–30 nm size of spherical particles were formed. Size of ITO particles was increased and particle resistance was decreased with increasing thermal oxidation temperature of indium tin hydroxide in the range of 400–700 °C. Particle size was decreased as tin content was increased from 3.18 to 21.11 at.% Sn/In in co-precipitation. The resistance of particles had a minimum point with changing of tin contents. The lowest resistance was shown in the region of about 3–5 at.% Sn in ITO. It was confirmed by Auger electron spectroscopy (AES) that tin ratio of ITO particle was increased with increasing tin contents.

Preparation and property control of nano-sized indium tin oxide particle

Indium tin oxide (ITO) particles of 20–30 nm in diameter, which would be used as coating material for electromagnetic wave shield, were synthesized by co-precipitation of indium chloride and tin chloride. Size and shape of particles were controlled by pH of co-precipitation solution, thermal oxidation temperature and tin contents. The prepared particles were thermally reduced under hydrogen gas to control electrical properties. When the solution pH was 6.75, plate type of particles with 60 nm size was coexisted with spherical particles of 20 nm size and the part of crystal structure was hexagonal. As pH was increased, plate type of particles was disappeared and 20–30 nm size of spherical particles were formed. Size of ITO particles was increased and particle resistance was decreased with increasing thermal oxidation temperature of indium tin hydroxide in the range of 400–700 °C. Particle size was decreased as tin content was increased from 3.18 to 21.11 at.% Sn/In in co-precipitation. The resistance of particles had a minimum point with changing of tin contents. The lowest resistance was shown in the region of about 3–5 at.% Sn in ITO. It was confirmed by Auger electron spectroscopy (AES) that tin ratio of ITO particle was increased with increasing tin contents.

Gate dielectrics on strained-Si/SiGe heterolayers

The purpose of this article is to report on the recent developments on the gate dielectric formation on strained-Si/SiGe heterolayers. In the first part, growth of a high quality strained-Si layer on a relaxed, linear or step-graded SiGe buffer layer and SiGe-free strained-Si on Silicon-on-Insulator (SSOI) is briefly reviewed. Characterization results of strained-Si films using atomic force microscopy (AFM), transmission electron microscopy (TEM) and Raman spectroscopy are then presented. In the second part, the processing issues of gate dielectric formation on strained-Si films are critically examined and the thermal oxidation of strained-Si layers are discussed. Low thermal budget processing, such as rapid thermal oxidation (RTO) and low temperature microwave plasma oxidation and nitridation of strained-Si layers are discussed in the third part. Microwave plasma deposition of various high- k gate dielectrics, such as ZrO 2, Ta 2O 5, and TiO 2 on strained-Si, their electrical properties and the current conduction mechanisms are also discussed.

Characteristics of ZnO whiskers prepared from organic-zinc

ZnO micro-whiskers were successfully prepared by oxidizing of sublimated zinc acetylacetonate (Zn(C 5H 7O 2) 2) products. Crystallinity of ZnO whiskers was considerably improved by increasing thermal oxidation temperature. Full width at half maximum (FWHM) of ZnO ( 1 0 1 ̄ 1 ) plane peak observed in the X-ray diffraction was 0.186°. SEM images of the whiskers oxidized at 1000 °C were a bundle of very fine whiskers and almost uniform for surface morphology. Room temperature photoluminescence (PL) spectrum of the whiskers oxidized over 400 °C shows a blue emission at wavelength of 420 nm. In the low temperature (4.2 K) PL spectrum of the ZnO whiskers oxidized over 800 °C, the emission from exciton bound to natural donor and that from free-exciton recombination were observed at 3.361 and at 3.376 eV, respectively.

Photoacoustic Spectra of Mixed TiO2 Ultrafine Powders with Rutile and Anatase Structures

We have measured the optical absorption of mixed TiO2 ultrafine powders with rutile and tanatase structures by photoacoustic (PA) spectroscopy, which is a powerful technique for detecting small amounts of strongly scattered materials. The values of band-gap energies, Eg, of the TiO2 ultrafine powders with different rutile contents were determined by the theory of interband transition in semiconductors. The values of Eg of rutile and anatase structures of TiO2 ultrafine powders are 3.00 eV and 3.20 eV, respectively, obtained from PA intensity and PA phase spectra, indicating the usefulness of PA spectroscopy. Mixed TiO2 ultrafine powders with rutile and anatase structures (20–140 nm diameters) were obtained by thermal oxidation of TiCl4. Rutile structure contents depend on the thermal oxidation temperature. The value of Eg of a mixed TiO2 ultrafine powder with rutile and anatase structures decreases continuously with the increase of the rutile content. This indicates that the apparent Eg can be controlled by mixing the nanometer-sized TiO2 powders with rutile and anatase structures, hence, we can control and obtain TiO2 materials with an arbitrary apparent Eg between rutile and anatase structures.

Oxidized silicon surfaces studied by high resolution Si 2p core-level photoelectron spectroscopy using synchrotron radiation

Abstract The Si 2p soft X-ray photoemission study of various oxidized surfaces (thermal oxidation and room temperature (RT) oxidation) shows the benefit derived from the use of high-energy resolution (70 meV). Interesting structural information can be retrieved from an analysis of the line widths of the oxides, suboxides, and elemental Si peaks. In particular the binding energy (BE) of elemental silicon layers adjacent to the oxidized layer can be distinguished from that of deeper silicon layers (the two prominent `interfacial' elemental Si lines are shifted by about +0.2 and −0.2 eV). These new data show a possible effect of oxygen second neighbors on elemental Si 2p binding energies. Moreover, changes in the oxide/suboxide line widths – as seen in a comparative study of the Si(1 1 1)-7×7 surface thermally oxidized in O2 and exposed at RT to O2 or H2O – may be attributed to static disorder, i.e., variations in Si–O bond lengths.

Toughened polypropylene with balanced rigidity. IV. Morphology, crystallization behavior, and thermal properties

The morphology of toughened polypropylene with balanced rigidity (TRPP) was characterized by using transmission electron microscopy and polarizing light microscopy. The crystallization behavior and thermal properties were investigated by differential thermal analysis and thermogravimetric analysis. The PP component in the polymer blend was realized as the continuous phase and the elastomer component as the dispersed phase with a cellular structure (salami structure) containing some PP. The particles of the dispersed phase were small and regular. The cellular structure of the TRPPs resulted from the introduction of toughening master batches and was similar to the morphology of acrylonitrile-butadiene-styrene and high-impact polystyrene synthesized by graft copolymerization. By gradually cooling from the melt, crystallization of TRPPs was nucleated heterogeneously and the crystallization temperature was slightly higher than that of PP whereas the crystallite size was remarkably reduced. For the samples with different compositions, the number, shape, and size of the cellular dispersed particles and the crystallite size were different. Considering the toughening theories and our experimental data, it was concluded that the samples with more regular and small cellular dispersed particles generally had better mechanical properties and the remarkably reduced crystallite size of PP was favorable for toughness improvement. The melting point, thermal oxidation temperature, and thermal oxidation onset temperature of the TRPPs were all a little lower than those of PP and the processability remained good.

SiGe virtual substrate N-channel heterojunction MOSFETs

Heterojunction MOSFETs (HMOSFETs), grown on a virtual substrate of SiGe and having a strained silicon channel, have been fabricated. A conventional silicon MOS process was used, including dry thermal oxidation and high temperature source-drain annealing. Good transistor I-V characteristics were obtained for devices having drawn gate lengths between 150 nm and 10 µm and an extrinsic transconductance of 220 mS mm-1 is reported for the 150 nm gate length device. Technology computer aided design (TCAD) is used to determine that the bulk low field mobility of the strained silicon which forms the channel is 1500 cm2 V-1 s-1, while the source-drain series resistance is 1.5 mm. Good agreement between simulated and experimental I-V data is obtained.

Characterization of light emitting silicon nanopillars produced by lithography and etching

Silicon nanopillars were produced by using deep-UV lithography, fluorine based highly anisotropic silicon etching and further thinning by high temperature thermal or chemical oxidation and oxide removal. The obtained structures were fully characterized by scanning and transmission electron microscopy, electron diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. It was verified that the obtained nanopillars by the above process are of perfect crystallinity, the bottom silicon surface on which they lie is very smooth and that minor surface contamination by carbon or oxygen is present on both the bottom silicon surface and the surface surrounding the nanopillars. The obtained luminescence peak is in the red-green spectral region.

FTIR study of thermal oxidation of ENR

Thermal oxidation of two grades of purified epoxidized natural rubber (ENR 25 and ENR 50) and one grade of unmodified natural rubber (purified SMR L grade) were studied using Fourier Transform Infrared Spectroscopy (FTIR). Changes in the characteristic absorption band, particularly the hydroxyl and carbonyl peaks of the degraded rubbers are carefully monitored. Results indicate that thermal oxidation occurs in the double bond region for SMR L to form oxidative products which mainly consist of hydroperoxide, hydroxyl and carbonyl compounds. In the case of ENR, thermal oxidation occurs not only in the double bond region, but also involves epoxide ring-opening reaction to yield oxidative products having similar functional groups as that of SMR L. For the three rubbers studied, increasing temperature of thermal oxidation increases the rate of oxidation. From a time-dependent study, it suggests that thermal oxidation of ENR is an autocatalytic process. No attempt, however, is made to ascertain the exact chemical structures of the oxidative products formed in this study.

Integrated processing of MOS gate dielectric structures

Integrated processing of MOS gate dielectric structures has been carried out in an ultraclean, multichamber processing system as a prototype for cluster (multichamber) processing in order to understand the potential and limitations of cluster processing for this application. With the enhanced surface cleanliness and contamination control enabled in this process environment, etching of the clean Si surface can occur when very low concentrations of oxygen species impinge on the surface at elevated temperatures, an intrinsic consequence of Si-O chemistry. Such etching leads to statistical roughening of the Si surface topography and thereby degrades the electrical properties of subsequently fabricated MOS structures. Identification of the etching reaction leads directly to prescriptions for cluster process integration which prevent etching: (1) ramping up to thermal oxidation temperature in an ambient with sufficient oxygen concentrations; and/or (2) in-situ formation of a passivating oxide surface layer as part of the pre-oxidation cleaning step. >

Chemical Oxide Passivation for Very Thin Oxide Formation

Electrical characteristics of the very thin oxides including oxide films formed in various chemicals were evaluated by means of the ultraclean oxidation system. The very thin oxides including the oxide films formed in H2SO4/H2O2, O3/H2O, and Hot-H2O22 have been found superior terms of reliability to those including the oxide films formed in NH4OH/H2O2/H2O and HCI/H2O2/H2O. The oxide films formed in H2SO4/H2O2, O3/H2O, and Hot–H2O2 have been found to function as the controlled passivation films which suppress increase of surface microroughness when heating of the wafer to thermal oxidation temperature in the inert gas ambience.

Preoxide-Controlled Oxidation for Very Thin Oxide Films

Very thin oxide films with high insulating performance and high reliability are formed by controlling preoxide growth with an ultraclean oxidation method during heating of the wafer to thermal oxidation temperature. The current level through the preoxide-controlled ultraclean oxide is lower than that through the oxide incorporating a thicker preoxide, and the preoxide-controlled ultraclean oxide has high reliability with respect to hot electron injection.