Thermal Oxide Films Research Articles

The effect of oxide scale on the corrosion resistance of SUS301L stainless steel welding joints

The effect of thermal oxidates on the corrosion of SUS301L stainless steel welded joint was investigated using electrochemical corrosion test and TEM microstructure observation. Activation dissolution behavior without passive region was found in the potentiodynamic polarization curves on the welding zone and heat affected zone. The activation corrosion is related to the preferential dissolution of the NiFe layer at the interface between chromium oxide and substrate. However, the passive region in the polarization curve reappears after the unstable NiFe dissolves in the salt-frog test. The passivation behavior due to microstructure evolution beneath the thermal oxide film was discussed during the corrosion process.

DC-free Method to Evaluate Nanoscale Equivalent Oxide Thickness: Dark-Mode Scanning Capacitance Microscopy.

This study developed a DC-free technique that used dark-mode scanning capacitance microscopy (DM-SCM) with a small-area contact electrode to evaluate and image equivalent oxide thicknesses (EOTs). In contrast to the conventional capacitance-voltage (C-V) method, which requires a large-area contact electrode and DC voltage sweeping to provide reliable C-V curves from which the EOT can be determined, the proposed method enabled the evaluation of the EOT to a few nanometers for thermal and high-k oxides. The signal intensity equation defining the voltage modulation efficiency in scanning capacitance microscopy (SCM) indicates that thermal oxide films on silicon can serve as calibration references for the establishment of a linear relationship between the SCM signal ratio and the EOT ratio; the EOT is then determined from this relationship. Experimental results for thermal oxide films demonstrated that the EOT obtained using the DM-SCM approach closely matched the value obtained using the typical C-V method for frequencies ranging from 90 kHz to 1 MHz. The percentage differences in EOT values between the C-V and SCM measurements were smaller than 0.5%. For high-k oxide films, DM-SCM with a DC-free operation may mitigate the effect of DC voltages on evaluations of EOTs. In addition, image operations were performed to obtain EOT images showing the EOT variation induced by DC-stress-induced charge trapping. Compared with the typical C-V method, the proposed DM-SCM approach not only provides a DC-free approach for EOT evaluation, but also offers a valuable opportunity to visualize the EOT distribution before and after the application of DC stress.

Electron-enhanced SiO2 atomic layer deposition at 35 °C using disilane and ozone or water as reactants

Electrons can enhance SiO2 atomic layer deposition (ALD) at low temperatures using disilane (Si2H6) and either ozone (O3/O2) or water (H2O) as reactants. SiO2 electron-enhanced ALD (EE-ALD) was demonstrated at 35 °C by exposing the sample to sequential electron, oxygen reactant, and Si2H6 exposures. The reaction sequence was electron beam exposure for 3 s, purge for 5 s, O3/O2 or H2O exposure at 0.5–1.0 Torr for 3 s, purge for 10 s, Si2H6 exposure at 100 mTorr for 1 s, and purge for 15 s. The electron exposure was an electron current of ∼150 mA for 3 s. The electrons were produced by a hollow cathode plasma electron source typically operating with a grid bias of ≈−300 V. These electrons could irradiate a sample area of ∼2 × 2 cm2. In situ spectroscopic ellipsometry measurements determined that SiO2 EE-ALD films nucleated rapidly and deposited linearly versus number of EE-ALD cycles. The SiO2 EE-ALD growth rate was 0.89 Å/cycle using O3/O2 and 0.88 Å/cycle using H2O. The SiO2 growth rate was also self-limiting at higher electron and Si2H6 exposures. In addition, SiO2 EE-ALD films were grown by changing the reaction sequence or codosing the electrons with the oxygen reactant. The SiO2 EE-ALD films could be grown on conducting silicon wafers or insulating SiO2 films. SiO2 EE-ALD is believed to be possible on insulating SiO2 films because the secondary electron yield for SiO2 at electron energies of ∼100–300 eV is greater than unity. Under these conditions, the SiO2 film charges positive during electron exposure and then pulls back secondary electrons to maintain charge neutrality. The SiO2 EE-ALD films had properties that were comparable with thermal SiO2 oxides. The refractive indices of the SiO2 EE-ALD films were similar at n = 1.44 ± 0.02 for various process conditions and equivalent to the refractive index of a wet thermal SiO2 oxide film. In addition, all the SiO2 EE-ALD films yielded etch rates in dilute buffered oxide etch solution that were only slightly higher than the etch rate of a thermal SiO2 oxide film. SiO2 EE-ALD should be useful to deposit high-quality SiO2 films for various applications at low temperatures.

Enhanced corrosion and wear resistance via thermal oxidation treatment on Zr-2.5Nb alloy for implant applications

The Zr-2.5Nb alloys were selected for thermal treatment from 500 to 800 °C in air. The effects of oxidation temperature on microstructure, phase composition, oxide film thickness, hardness, and element distribution were investigated. The results revealed that the oxide film thickness and hardness showed a positive correlation as the oxidation temperature increased. The oxide film was mainly composed of ZrO2 and Nb2O5. The effect of oxidation temperature on the phase composition of the oxide film was also investigated, and it was found that the content of m-ZrO2 gradually increased with increasing temperature, and the content of Nb2O5 remained basically unchanged. Impedance and potentiodynamic polarization curves technique of oxide films in simulated body fluids at pH = 2.86 were investigated, and the results showed that a suitable thermal oxidation temperature could significantly improve the corrosion resistance of the Zr-2.5Nb alloy. In addition, the wear resistance of the specimens after thermal oxidation was investigated, and it was found that the wear resistance of the oxidized specimens was significantly improved. And the biocompatibility of the thermal oxide film was investigated by hemolysis test and contact angle experiments.

Surface Cleaning and Modification of Oxide Films by Atomic Hydrogen Annealing

To suppress degradation of the electrical property of field-effect transistors, the removal of C contamination without damaging oxide films is important in the semiconductor industry. In addition, to reduce bonding failure, it is necessary to remove native oxide films from metal films. To achieve this, atomic hydrogen was generated by the decomposition of H2 gas on a heated tungsten mesh. This surface treatment is referred to as atomic hydrogen annealing (AHA). The reaction of atomic hydrogen with various oxide films, such as AlOx, TiOx, CrOx, NiOx, CuOx, and SiOx, was investigated. The O concentrations in Al, Ti, and Cr slightly decreased by AHA. The thermal oxide films prepared at 400 ℃ were not changed by AHA, except for CuOx. The reduction in the reactivity of the oxide film due to atomic hydrogen depends on the metal–oxygen bond strength. In addition, although the thermal oxide film of the Si substrate prepared at 1000 ℃ was not etched, AHA resulted in the etching of the Si-rich SiOx. These findings are useful for the removal of C contamination and native oxide films and for controlling the surface properties of oxide films.

Femtosecond laser micromachining for stress-based figure correction of thin mirrors

The fabrication of a large number of high-resolution thin-shell mirrors for future space telescopes remains challenging, especially for revolutionary mission concepts such as NASA’s Lynx X-ray Surveyor. It is generally harder to fabricate thin mirrors to the exact shape than thicker ones, and the coatings deposited onto mirror surfaces to increase the reflectivity typically have high intrinsic stress that deforms the mirrors further. Since the rapid development of femtosecond laser technologies over the last few decades has triggered wide applications in materials processing, we have developed a mirror figure correction and stress compensation method using a femtosecond laser micromachining technique for stress-based surface shaping of thin-shell x-ray optics. We employ a femtosecond laser to selectively remove regions of a stressed film that is grown onto the back surface of the mirror, to modify the stress states of the mirror. In this paper, we present experimental results to create both isotropic and anisotropic stress states on thin flat silicon mirrors with thermal oxide ( S i O 2 ) films using femtosecond lasers. We show that equibiaxial stress can be generated through uniformly micromachined holes, while non-equibiaxial stress arises from the ablation of equally spaced troughs. We also present results from strength tests to show how this process minimally affects the strength of mirrors. These developments are beneficial to the high-throughput correction of thin-shell mirrors for future space-based x-ray telescopes.

Degradation of thermal oxide film on pure titanium in an acidic environment containing fluoride

Electrochemical degradation behavior of thermally oxidized pure Ti in the fluoride-containing acidic environments was investigated. Compact TiO2 oxides with acceptable hardness and superior corrosion resistance are formed through the thermal oxidation at 650 °C for 24 h. Corrosion of the oxidized Ti depends on the oxidation condition and fluoride content, resulting in the various interfacial structures at the oxide/solution and metal/solution interface. Degradation of the oxidized Ti consists of three stages during long-term immersion, while its critical fluoride concentration is increased by 1~2 orders of magnitude, attributed to the high stability of the TiO2 thermal oxides.

Unraveling the formation mechanism of hybrid Zr conversion coating on advanced high strength stainless steels

This research unravels the formation mechanism of a hybrid conversion treatment including the well-established Zr conversion coating with a silane-based organic additive and Cu-based inorganic additive. The deposition mechanism of this coating was investigated on the thermal oxide film of Advanced High Strength Stainless Steels (AHSSS). This coating has been characterized using advanced surface analytical techniques such as XPS, FEG-AES, GDOES, and ToF-SIMS. The results showed that the simultaneous presence of these two additives results in the formation of a donor-acceptor complex between amine groups and Cu ions. The final coating contains Cu oxide together with a Cu-aminosilane complex, Zr oxide deposited mainly around Cu oxide and the aminosilane layer on the outer surface.

Improving the reliability of MOS capacitor on 4H-SiC (0001) with phosphorus diffused polysilicon gate

The interface states and reliability of 4H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs) with thermal gate oxides have been researched widely. Several reports have researched the gate oxide process itself, but the effects of subsequent processes should not be ignored. In this paper, the reliability of thermal gate oxide films followed by polysilicon gate (poly-gate) process, which are widely used in MOSFET manufacture, and Al gates were compared. The poly-gate samples markedly affected the performance measured by time-zero dielectric breakdown and time-dependent dielectric breakdown methods because the phosphorus content diffused during poly-gate formatting; this was especially advantageous in reducing leakage current and improving the charge-to-breakdown (Q BD). After electronic characteristics measurements, scanning electron microscopy cross-sections were also used to analyze the breakdown mechanism. We observed an intermediate layer between the Al gate and the oxide that may cause the barrier height to be smaller than that of the poly-gate. The Al work function and polysilicon Fermi level determine the gate leakage currents and the resultant gate oxide reliability, whereas the Al2O3 gate sample has a smaller work function offset (0.7 eV) than ideal Al gate and poly-gate samples. The results imply that the reliability of the Al gate samples may be an intrinsic problem.

Electroluminescence of SiO2 films grown on Si by thermal oxidation and plasma-enhanced chemical vapor deposition

Emission of the silicon oxide films grown on Si by wet thermal oxidation at 900 °С and by plasma-enhanced chemical vapor deposition from the SiH4 + N2O mixture at 350 °С has been compared using electroluminescence. The electroluminescence spectra were recorded in electrolyte – insulator – semiconductor system. The intense band in the red range with a maximum at 1.9 eV dominates the electroluminescence spectrum of the thermal oxide film. It was concluded that this band is related with the existence of silanol groups (Si — OH) in the oxide matrix. Multiband emission in the UV range is observed in the electroluminescence spectrum of the oxide film formed by plasma-enhanced chemical vapor deposition. Additional investigations using IR and RS spectroscopy revealed that observed spectrum modulation is of an oscillatory nature and is not the result of interference. Presumably, the luminescence in the UV region is due to the presence of oxygen deficiency centers containing bonds with hydrogen atoms.

Unraveling the mechanism of the conversion treatment on Advanced High Strength Stainless Steels (AHSSS)

In this research, a novel governing mechanism has been proposed for the formation of conversion coating on the thermal oxide film of Advanced High Strength Stainless Steels (AHSSS). These new lightweight and engineered materials are being designed to impart emission reduction and solid performance. This coating has been characterized using advanced surface analysis such as HAADF-STEM, GDOES, and ToF-SIMS. The results showed that the conversion components can be found not only on the surface but also at the oxide/metal interface. This deposition in the depth happens preferentially in the Si-poor regions and with the penetration of the conversion components into depth. It was indicated that fluoride ions play an important role to facilitate this penetration by dissolving the less stable components in the oxide film. Dissolution of the Fe in the Fe-Cr solid solution structure results in the formation of a mixed chemical structure containing Cr and P. This novel mechanism brings a new insight into the field of conversion coating when a thick oxide film is present on the top surface.

Study on thermal, mechanical, microstructural properties and failure analyses of lanthanum zirconate based thermal barrier coatings: A review

This research study summarizes the recent information about the characteristics of multi layer and composite lanthanum zirconate based thermal barrier coatings (TBCs) that provide high-temperature thermal protection for the jet engines parts. Thus the outcome of lightweight gas turbine components able to work at 3000° F nearly 1650 °C needs to be built. Such difficulties can be solved using coatings with optimized microstructure and chemical composition. Recently, Lanthanum zirconate (La2Zr2O7-LZ) based pyrochlore oxides (Ra2Zr2O7, Re = rare earth) are now developing TBC material, owing to their fewer thermal conductivity with enhanced stability at elevated operating temperatures. Even though LZ cannot be directly replaced for standard YSZ because of its mismatch between the grew of thermal oxide (TGO) film. When LZ compared to Zirconia partially stabilized with yttria (YSZ), LZ possesses a poor thermal conductivity, lesser coefficient of thermal expansion, lower sintering ability, and lack of toughness than YSZ. Hence LZ comes to be combined with standard TBC YSZ in order to integrate advantages in multilayer architecture. In this study describes the thermal, mechanical and physical properties and failure analysis of Multilayer LZ/YSZ were described. It also reviews the characterization of coatings according to different criteria and conditions. At last, suggestions for investigation on layered LZ based TBCs applications for next-generation was indicated.

The mechanism of thermal oxide film formation on low Cr martensitic stainless steel and its behavior in fluoride-based pickling solution in conversion treatment

(Attention for corrosion science, the abstract must not exceed more than 100 words)In this research, first a multi-analytical approach was carried out to propose a mechanistic model for the formation of the thermal oxide film on low Cr stainless steel. It describes the effects of kinetically and thermodynamically driven phenomena on the growth of a Fe-Cr complex oxide film at 950℃. Second, the behavior of the thermal oxide film in the presence of fluoride ions, as a relevant pickling agent in conversion treatment, was investigated. It was shown that fluoride ions enter the oxide film and form a complex with Fe and preferentially dissolve hematite islands through a complexation mechanism.

Atomic and Electronic Structure of SiOx Films Obtained with Hydrogen Electron Cyclotron Resonance Plasma

The silicon oxide thin films obtained by thermal SiO2 treatment in hydrogen electron cyclotron resonance plasma at various exposure times are investigated. Using X-ray photoelectron spectroscopy, we have established that such treatment leads to a significant oxygen depletion of thermal SiO2, the more so the longer the treatment time. The atomic structure of the SiOx < 2 films obtained in this way is described by the random bonding model. The presence of oxygen vacancies in the plasma-treated films is confirmed by comparing the experimental valence band photoelectron spectra and those calculated from first principles, which allows the parameter x to be estimated. We show that thermal silicon oxide films treated in hydrogen plasma can be successfully used as a storage medium for a nonvolatile resistive memory cell.

Phonon-assisted electron tunneling between traps in silicon oxide films treated in hydrogen plasma

The charge transport in thin thermal silicon oxide films treated in electron cyclotron resonance hydrogen plasma at different exposure times was investigated. X-ray photoelectron studies show that such treatment leads to the oxygen deficiency of the films. It was established that the treatment of the films in plasma leads to an increase of their conductivity by a factor of about 102. The film charge transport properties were studied at different temperatures and analyzed within four theoretical dielectric conductivity models. It was found that the charge transport mechanism is described by Fowler-Nordheim model in the initial silicon oxide and by the model of phonon-assisted electron tunneling between neutral traps after the treatment in hydrogen plasma. The thermal trap ionization energy value (Wt = 1.6 eV) measured from transport experiments is in agreement with that obtained from ab initio calculations for the oxygen vacancy (Si-Si bond) in SiO2.

An Automated System for Reactive Accelerated Aging of Implant Materials with In-Situ Testing.

The efficacy of implantable medical devices is limited by the longevity of devices in the body environment. Due to the aqueous and mobile-ion rich environment of tissue, robust and long-lasting encapsulation materials are critical for chronic implants. Assessing the reliability of medical devices is commonly performed through saline soak tests with reactive oxidative species at elevated temperatures and lifetime data are fit to an Arrhenius model to predict lifetime under physiological conditions. While effective, these systems often require frequent human involvement to maintain system temperature and reactive oxidative species concentration, as well as monitor sample lifetime, which makes long term testing of multiple samples difficult. Here we present an automated, low-cost, low-solution volume, and high-throughput reactive accelerated aging system to assay many thin film samples in an easy and low maintenance manner. The efficacy of up to 16 thin film coating samples can be assessed by our system through in-situ current leakage tests in a mock biological environment. We validate our system by aging thermal oxide and a-SiC thin films at 93 °C with 20 mM H2O2. Our system shows early failure of the thermal oxide compared to the a-SiC, in agreement with the current literature.

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Modification of nanoscale thermal oxide films formed on indium phosphide under the influence of tin dioxide

Modification of nanoscale thermal oxide films formed on indium phosphide under the influence of tin dioxide

Study of the Electrical and Diffusion Barrier Properties in Ultrathin Carbon Film-Coated Copper Microwires for Interconnects

Four specimen patterns with the microstructure of a microcopper wire are deposited on the Si-wafer substrate plus thermal oxide (SiO2) film as the top layer. Each pattern was prepared to have two kinds of specimens, including with and without ultrathin carbon film between the copper wire and the top layer (SiO2). The effect of carbon film on electrical properties is evaluated via the measurements of the I (current)–V (voltage) curve, sheet electrical resistance, current leakage, and its ratio and effective permittivity. A rapid thermal annealing (RTA) technique is provided as an economic and efficient method to grow the ultrathin carbon film rapidly as the interlayer. Appropriate choices of 900 °C and 3 min as the annealing temperature and time can produce ultrathin carbon film with nearly 100% coverage of the copper surface. The sheet resistance of specimen demonstrates the behavior exactly opposite to that of the carbon film coverage of wire surface. The combined effect of elevating the voltage and annealing temperature of the specimen with carbon film on the current leakage is much lower than that arising in the specimen without carbon film, so long as the carbon films operating at that temperature (between 350 and 500 °C) are still sustainable. The differences in current leakage and effective permittivity between these two kinds of specimen are significantly increased by raising the temperature. The intensity (IC) of copper diffusions into the SiO2 layer in the specimens with the carbon film demonstrates behavior similar to that of current leakage (CL). The IC and CL values for the temperatures ≦ 350 °C are much lower than those obtained at 500 °C.

Frequency analysis for investigation of the thermomechanical mechanisms in thermal oxides growing on metals

In the present work, mechanical features in thermal oxide films growing on metals have been investigated during cyclic thermal loadings. An adapted model is considered to describe the stress evolution within oxide films, taking into account thermomechanical couplings. These numerical predictions are compared with experimental results obtained using synchrotron diffraction at ESRF. In order to obtain the features of the system, an innovative data treatment is thus proposed and performed. By dealing with the frequency analysis of the system, the method is able to identify some mechanisms. This mechanical spectroscopy allows thus to confirm the thermomechanical description of a chromia-former alloy.