Layer-By-Layer Oxidation of Silicon Surfaces

1999 ◽  
Vol 567 ◽  
Author(s):  
Heiji Watanabe ◽  
Noriyuki Miyata ◽  
Masakazu Ichikawa
Keyword(s):  
Subsurface Layer ◽  
Initial Step ◽  
Silicon Surfaces ◽  
Layer By Layer ◽  
First Principles Calculations ◽  
Initial Oxidation ◽  
Si Substrates ◽  
Interfacial Structures ◽  
Reflection Electron Microscopy ◽  
Kinetics Of

ABSTRACTLayer-by-layer oxidation of Si(111) and (001) surfaces has been studied by using scanning reflection electron microscopy (SREM). We found that SREM images reveal interfacial structures of the SiO2/Si system. Our results showed that the initial step structure of Si substrates was preserved at SiO2/Si interfaces and that interfacial steps did not move laterally during oxidation. We also observed a periodic reversal of terrace contrast in SREM images during the initial oxidation of Si(001) surfaces. These results indicate layer-by-layer oxidation of Si surfaces, which is promoted by the nucleation of nanometer-scale oxide islands at SiO2/Si interfaces. In addition, we investigated the kinetics of initial layer-by-layer oxidation of Si(001) surfaces. We found that a barrierless oxidation of the first subsurface layer, as well as oxygen chemisorption onto the top layer, occur at room temperature. The energy barrier of the second-layer oxidation was found to be 0.3 eV. The initial oxidation kinetics are discussed based on first-principles calculations. Moreover, we confirmed that the layer-by-layer oxidation of Si surfaces holds true for conventional furnace oxidation.

Surface and Interfacial Topography of Oxides on Si(111) With Ultra-Low Atomic Step Density

1999 ◽  
Vol 592 ◽  
Author(s):  
Antonio C. Oliver ◽  
Jack M. Blakely
Keyword(s):  
Initial Step ◽  
Oxide Thickness ◽  
Interface Roughness ◽  
Oxide Surface ◽  
Atomic Step ◽  
Layer By Layer ◽  
Initial Oxidation ◽  
Atomic Steps ◽  
Si Substrates ◽  
Step Density

ABSTRACTAtomic force microscopy has been used to study the morphology of the oxide surface and the Si-SiO2 interface after oxidation of Si(111) surfaces that are either totally free of atomic steps or have well characterized low step density. The step-free areas were formed by thermally processing a patterned Si surface in which flat areas are enclosed by a square array of ridges; flow of the atomic steps into the surrounding ridge barriers produces a regular array of step-free areas each of which can be up to ∼50µm×50µm. Arrays of widely spaced steps (e.g. 5µm) can also be produced in the step-free areas. AFM scans of the same areas were taken prior to (dry) oxidation, after oxidation, and after chemical removal of the oxide. It was found that at an oxide thickness in the 5-13nm range, the initial step structure of the underlying Si substrates is translated through the oxide to the surface after oxidation with the oxide surface being somewhat rougher than the initial substrate. Furthermore, the initial step morphology of the substrate remains at the Si-SiO2 interface after etching away the oxide by HF. The interface roughness is less than that of the oxide surface. The results suggest that the initial oxidation of silicon proceeds in a ‘layer by layer’ manner and not through a preferential step-flow oxide growth mode.

Oxidation Kinetics of Silicon Surfaces: Reactive Sticking Coefficient, Apparent Saturation Coverage and Effect of Surface Hydrogen

1988 ◽  
Vol 131 ◽  
Author(s):  
S. M. George ◽  
P. Gupta ◽  
C. H. Mak ◽  
P. A. Coon
Keyword(s):  
Surface Temperature ◽  
Silicon Surfaces ◽  
Sticking Coefficient ◽  
Initial Oxidation ◽  
Surface Hydrogen ◽  
Oxygen Coverage ◽  
Saturation Coverage ◽  
Temperature Programmed ◽  
Kinetics Of ◽  
Effect Of Surface

ABSTRACTThe kinetics of the initial oxidation of silicon surfaces by O2 were studied using laser-induced thermal desorption (LITD), temperature programmed desorption (TPD) and Fourier Transform Infrared (FTIR) spectroscopy. The LITD results showed that the oxidation of Si(111)7×7 by O2 was characterized by two kinetic processes: an initial rapid oxygen uptake followed by a slower growth that asymptotically approached an apparent saturation oxygen coverage. The initial reactive sticking coefficient of O2 on Si(111)7×7 decreased with surface temperature. In contrast, TPD experiments on Si(111)7×7 and FTIR studies on porous silicon demonstrated that the apparent saturation oxygen coverage increased as a function of surface temperature. Experiments with preadsorbed hydrogen also revealed that silicon oxidation was inhibited as a function of increasing hydrogen coverage on the Si(111)7×7 surface.

Transmission Electron Microscopy characterization of epitaxial III-V semiconductor thin films grown on Si(100) by ion-assisted deposition

1990 ◽  
Vol 48 (4) ◽  
pp. 686-687
Author(s):  
L. Hultman ◽  
C.-H. Choi ◽  
R. Kaspi ◽  
R. Ai ◽  
S.A. Barnett
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Irradiation ◽  
High Energy ◽  
Nucleation Mechanism ◽  
Layer By Layer ◽  
Extended Defect ◽  
Island Formation ◽  
Si Substrates ◽  
Transmission Electron

III-V semiconductor films nucleate by the Stranski-Krastanov (SK) mechanism on Si substrates. Many of the extended defects present in the films are believed to result from the island formation and coalescence stage of SK growth. We have recently shown that low (-30 eV) energy, high flux (4 ions per deposited atom), Ar ion irradiation during nucleation of III-V semiconductors on Si substrates prolongs the 1ayer-by-layer stage of SK nucleation, leading to a decrease in extended defect densities. Furthermore, the epitaxial temperature was reduced by >100°C due to ion irradiation. The effect of ion bombardment on the nucleation mechanism was explained as being due to ion-induced dissociation of three-dimensional islands and ion-enhanced surface diffusion.For the case of InAs grown at 380°C on Si(100) (11% lattice mismatch), where island formation is expected after ≤ 1 monolayer (ML) during molecular beam epitaxy (MBE), in-situ reflection high-energy electron diffraction (RHEED) showed that 28 eV Ar ion irradiation prolonged the layer-by-layer stage of SK nucleation up to 10 ML. Otherion energies maintained layer-by-layer growth to lesser thicknesses. The ion-induced change in nucleation mechanism resulted in smoother surfaces and improved the crystalline perfection of thicker films as shown by transmission electron microscopy and X-ray rocking curve studies.

scholarly journals Oxidation behavior of non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution powders in air

2021 ◽  
Author(s):  
Huilin Lun ◽  
Yi Zeng ◽  
Xiang Xiong ◽  
Ziming Ye ◽  
Zhongwei Zhang ◽  
...  
Keyword(s):  
Solid Solution ◽  
Oxidation Resistance ◽  
Oxidation Behavior ◽  
Group Iv ◽  
Hypersonic Vehicles ◽  
Metal Carbides ◽  
Initial Oxidation ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Kinetics Of

AbstractMulti-component solid solutions with non-stoichiometric compositions are characteristics of ultra-high temperature carbides as promising materials for hypersonic vehicles. However, for group IV transition-metal carbides, the oxidation behavior of multi-component non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution has not been clarified yet. The present work fabricated four kinds of (Zr,Hf,Ti)Cx carbide solid solution powders by free-pressureless spark plasma sintering to investigate the oxidation behavior of (Zr,Hf,Ti)Cx in air. The effects of metallic atom composition on oxidation resistance were examined. The results indicate that the oxidation kinetics of (Zr,Hf,Ti)Cx are composition dependent. A high Hf content in (Zr,Hf,Ti)Cx was beneficial to form an amorphous Zr-Hf-Ti-C-O oxycarbide layer as an oxygen barrier to enhance the initial oxidation resistance. Meanwhile, an equiatomic ratio of metallic atoms reduced the growth rate of (Zr,Hf,Ti)O2 oxide, increasing its phase stability at high temperatures, which improved the oxidation activation energy of (Zr, Hf, Ti)Cx.

scholarly journals Characteristics and Kinetics of Rosin Pentaerythritol Ester via Oxidation Process under Ultraviolet Irradiation

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2816 ◽  
Author(s):  
Yuanlin Li ◽  
Xiongmin Liu ◽  
Qiang Zhang ◽  
Bo Wang ◽  
Chang Yu ◽  
...  
Keyword(s):  
Light Intensity ◽  
Oxidation Kinetics ◽  
Pseudo First Order Reaction ◽  
Initial Oxidation ◽  
Photo Oxidation ◽  
Average Value ◽  
Pentaerythritol Ester ◽  
Fundamental Information ◽  
The Stability ◽  
Kinetics Of

A self-designed reaction device was used as a promising equipment to investigate the oxidation characteristics and kinetics of rosin pentaerythritol ester (RPE) under UV irradiation. Photo-oxidation kinetics and the initial quantum yield (Φ) of RPE were calculated. The initial oxidation product of the photo-oxidation reaction—peroxide was analyzed by iodimetry. The peroxide concentration is related to the light intensity (I) and the temperature (T), and the increasing T and I would destabilize the RPE by accelerating peroxide forming. Photo-oxidation of RPE follows the pseudo first-order reaction kinetics. The relationship between activation energy and logarithm of light intensity (ln I) is linear, and it is expressed as Ea = −4.937ln I + 45.565. Φ was calculated by the photo-oxidation kinetics, and the average value of Φ was 7.19% in the light intensity range of 200–800 μW cm−2. This research can provide fundamental information for application of RPE, and help obtain a better understanding of the stability of rosin esters.

Effect of degradation kinetics on the microstructure of anaerobic biogranules

1995 ◽  
Vol 32 (8) ◽  
pp. 165-172 ◽  
Author(s):  
Herbert H. P. Fang ◽  
Chui Ho-Kwong ◽  
Li Yu-You
Keyword(s):  
Degradation Kinetics ◽  
Monosodium Glutamate ◽  
Initial Step ◽  
Upflow Anaerobic Sludge Blanket ◽  
Anaerobic Sludge ◽  
Electron Microscopies ◽  
Subsequent Degradation ◽  
Anaerobic Sludge Blanket ◽  
Rate Limiting ◽  
Kinetics Of

The microstructure of anaerobic biogranules treating a wide variety of wastewaters was investigated using light and scanning electron microscopies. Biogranules were sampled from upflow anaerobic sludge blanket (UASB) reactors treating wastewater individually containing formate, acetate, propionate, butyrate, peptone, sucrose, starch, benzoate, brewery and monosodium glutamate. Results indicated that the microstructure of the biogranules was strongly dependent on the degradation kinetics of substrates. Anaerobic degradation is a multi-step process, involving fermentation/acidogenesis, acetogenesis and methanogenesis. For substrates, such as carbohydrates, of which the initial step of degradation was considerably faster than the subsequent degradation of intermediates, biogranules developed a layered microstructure. On the other hand, for substrates, such as proteins, of which the initial step of degradation was rate-limiting, a uniform microstructure would be developed. These findings are of significance for the development of kinetic models for biogranule and biofilm.

2. Adhesion of the plasma-polymerized fluorocarbon films to silicon substrates The adhesion properties of the plasma-polymerized FC coatings were determined by using a test, already employed by Yasuda and Sharma [13] (see Fig. 1 and Table 1) in which the silicon substrates coated with plasma FC-films were boiled in a0.9% sodium chloride solution. The FC thin films produced in the processes 1 and 2 were lifted after a very short time (15 minutes). Coatings generated in process 3 were lifted after the second cycle of boiling. The films produced in processes 4 and 5 withstood the complete test procedure. The results are shown in Fig. 3. The poor adhesion of the polymerized films in the first two processes is due to the fact that these processes do not involve a plasma pre-treatment process. The difference between processes 1 and 3 is only in the plasma pre-treatment (process 1 does not contain the pre-treatment step of the silicon surface). The fluorocarbon films deposited by processes 4 and 5 have shown the best adhesion. These test results indicate that the plasma pre-treatment is very important and necessary for a good adhesion of the FC coatings to the silicon surfaces. 2.3. Patterning of FC films 2.3.1. Patterning through resist mask. The patterning of the FC films through a photoresist mask (conventional All resist AR-P351) was examined after deposition for process No. 5. Different coating parameters were investigated to improve the adhesion of the resist to the FC surface. The best adhesion results were obtained using the process parameters, shown in Table 3. Differences in the thickness uniformity of so-deposited resists were in a range below 5%. The samples were etched in a pure oxygen plasma in an RIE-system after the lithography steps (pre-bake, exposure, development, post-bake). A resolution of 2 /xm was obtained. A significant increase in the surface energy was not observed after resist stripping. The sessile contact angle of water was 103°. 2.3.2. Lift-off process for patterning thin plasma polymerized FC films. A lift-off process was also examined to pattern the thin FC films. The lithography steps were used before the plasma polymerization process was carried out (Fig. 2). A standard resist AR-P351 was coated directly onto the Si substrates. After all lithography

2014 ◽  
pp. 275-278
Keyword(s):  
Treatment Process ◽  
Test Procedure ◽  
Silicon Surfaces ◽  
Silicon Substrates ◽  
Fluorocarbon Films ◽  
Si Substrates ◽  
Complete Test ◽  
The Difference ◽  
Pre Treatment ◽  
Lift Off

First-Principles Investigations of Hydrogen and Fluorine on Silicon Surfaces

1992 ◽  
Vol 259 ◽  
Author(s):  
Chris G. Van De Walle
Keyword(s):  
First Principles ◽  
Etch Rate ◽  
State Of The Art ◽  
Interstitial Impurity ◽  
Silicon Surfaces ◽  
Hydrogen Solubility ◽  
First Principles Calculations ◽  
Energy Diagram

ABSTRACTState-of-the-art first-principles calculations allow detailed studies of the mechanisms by which hydrogen and fluorine interact with silicon. The results for hydrogen are presented in the form of an energy diagram which includes many different configurations. The theoretical values allow a discussion of issues such as hydrogen solubility, and desorption from a Si surface. For fluorine, we investigate the behavior as an interstitial impurity in the bulk, as well as Si-F interactions at or near the surface. A study of the insertion of F atoms into Si-Si bonds elucidates the microscopic mechanisms of etching, and the dependence of etch rate on doping. Thermodynamic aspects of HF etching are briefly discussed.

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