Numerical investigation on atomic oxygen undercutting of the protective polymer film using Monte Carlo approach

Atomic oxygen undercutting effect of the protective polymer film in low earth orbit space environment is a potential threat to vulnerable long duration exposure facility. A Monte Carlo computational model is developed to simulate the interactions between atomic oxygen undercutting course with polyimide film. Physical process of the atomic oxygen undercutting, the definition of parameters, the affected by atomic oxygen fluence, orbit angle, protection coating thickness and thermal assimilation and the additive anti-undercutting components as well as a new three-dimensional reaction probability are discussed in detail. Simulated results are in good agreement with flight experimental data. With the increment of the atomic oxygen fluence, all the undercutting profiles, the depth and the width increased. Maximum undercutting depth is always larger than maximum undercutting width and the larger thermal assimilation coefficient causes the smaller undercutting damage. Using three-dimensional reaction probability, maximum depth decreased by approximately 20% than that of 28.5° orbit angle.     

Facile preparation of super-hydrophobic and super-oleophilic silica film on stainless steel mesh via sol-gel process

A super-hydrophobic and super-oleophilic silica film on stainless steel mesh was obtained by simple sol-gel method using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) as precursors. The super-hydrophobic and super-oleophilic properties were achieved owing to the hierarchical structure of the silica film with methyl groups terminated domains constructed on the mesh. The effects of the particle size, molar ration of MTES/TEOS, molar concentration of TEOS and aging of the silica sol on the hydrophobicity of the silica film were discussed. With increasing the dimensional size of silica particle, molar ration of MTES/TEOS, molar concentration of TEOS and aging period, the hydrophobicity of the silica film can be enhanced due to the increase of the surface roughness or coverage of the methyl groups. Besides, diiodomethane droplet can spread out on the silica film within 6.71 s for the capillary force and intrinsic oleophilicity of the methyl groups.     

Effect of organosilane agents on the vulcanizate structure and physical properties of silica-filled solution styrene butadiene rubber compounds

Physical properties of rubber compounds are affected by the filler-rubber interaction, filler dispersion in the rubber matrix, and crosslink structure formed during vulcanization. Organosilane agents are essentially used in silica-rubber compounds to inhibit the formation of silica agglomerates and increase the formation of silica-rubber networks. Generally, organosilane agents have an alkoxysilyl alkyl sulfide structure and are classified into silane coupling and covering agents depending upon the presence of sulfur. Coupling agents have a sulfur moiety and serve as a sulfur donor during the vulcanization process, thus increasing the formation of filler-rubber and chemical crosslink networks. On the other hand, covering agents promote the hydrophobation of silica surfaces, decreasing the adsorption loss of vulcanization additives, which increases the formation of chemical crosslink networks. This implies that organosilane agents can affect the vulcanizate structure, which causes a variation in the properties of silica compounds. Therefore, in this study, the effect of coupling (bis(3-triethoxysilylpropyl)disulfide (TESPD) and bis(3-triethoxysilylpropyl)tetrasulfide (TESPT)) agents and a covering (triethoxy(octyl)silane) agent on the vulcanizate structure and properties of silica compounds was investigated and compared. In the comparative study of coupling and covering agents, the influence of sulfur donors on the formation of vulcanizate structures was investigated. In the case of the coupling agents, the effect of sulfur rank on the vulcanizate structure and properties of silica-rubber compounds was quantitatively analyzed through various characterization techniques.     

Atomic oxygen erosion resistance of polyimide/ZrO2 hybrid films

A series of polyimide/zirconia (PI/ZrO₂) hybrid films were synthesized based on zirconium n-butoxide, pyromellitic acid dianhydride (PMDA) and 4,4′-oxydianiline (ODA) by a sol-gel process. The atomic oxygen (AO) exposure tests were carried out using a ground-based atomic oxygen effects simulation facility. The effects of ZrO₂ content on the morphology and structure evolvement of PI/ZrO₂ hybrid films were investigated using field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectrometer (XPS), respectively. The results indicated that a zirconia-rich layer was formed on the polyimide film sourcing from the zirconium n-butoxide after AO exposure, which decreased the erosion rate and obviously improved the AO resistance of polyimide films.     

Effects of atomic oxygen treatment on structures, morphologies and electrical properties of ZnO:Al films

ZnO:Al (ZAO) film has a potential application in providing spacecrafts the protection against atomic oxygen (AO) erosion. To advance the understanding of the AO resisting mechanisms and the relationships between the structures, morphologies and conductive properties of ZAO film, direct current magnetron sputtered ZAO films with different thicknesses were treated with AO in a ground-based simulation facility. The microstructure, surface chemical state, morphologies and electrical properties of pristine films and irradiated ones were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and Hall measurement. It is found that AO exposure produces novel, oriented recrystallization of the surface particles. It also increases the content of oxygen ions in fully oxidized stoichiometric surroundings on the surface, resulting in the decrease of the conductivity. As the thickness of ZAO film increases, the crystallinity, conductivity and resistance to AO erosion are all improved.     

提拉法SiO2化学膜厚度与折射率的变化规律研究

采用提拉法在硅基底上制备了多孔溶胶凝胶SiO2膜,用椭偏法测量薄膜的厚度与折射率,考察了提拉速度和胶体浓度对膜层厚度与折射率的影响。对厚度与提拉速度的关系进行线性与幂函数拟合,并比较分析两种拟合的关系及其对工艺流程的作用。比较了不同浓度胶体所得到的同一厚度薄膜的折射率变化规律。结果表明：对于同一胶体浓度下薄膜厚度与提拉速度的正相关关系,线性拟合相比幂函数拟合可以更好地解释实验结果的规律性。同时,折射率在一定范围内也会随着提拉速度的增加而减小。镀同一厚度膜时,浓度大的胶体膜层折射率大。通过对提拉速度和胶体浓度的控制可以得到理想的薄膜厚度与折射率。     

Improvement of anti-oxidation capability and tribological property of arc ion plated Ag film by alloying with Cu

Ag-Cu alloy film was deposited by arc ion plating (AIP). Atomic oxygen (AO) irradiation experiments were conducted using a ground AO simulation facility. The structure, morphology, composition and tribological property of the Ag-Cu alloy film before and after AO irradiation were investigated and compared with Ag film using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. In depth XPS analysis clearly shows that the affected thickness of Ag-Cu alloy film was greatly reduced and the oxidation product was mainly Ag₂O, but AgO and Ag₂O in case of pure Ag film. As a result, the Ag-Cu alloy film exhibited better AO resistant behaviors, and showed a stable friction and low wear after the AO irradiation. The AO resistant behaviors of the Ag-Cu alloy film were discussed in terms of the film microstructure.     

溶胶-凝胶法MgF2紫外增透膜的制备和性能研究

 采用溶胶-凝胶法,以醋酸镁和氟化氢为原料,以甲醇为溶剂制备了MgF₂溶胶,利用浸渍提拉法在洁净石英基片上镀膜,考察了反应温度对溶胶微结构、薄膜结构和性能的影响。样品采用激光动态光散射、透射电镜、X射线粉体衍射仪、紫外-可见光谱仪、原子力显微镜进行表征。结果表明：通过该方法制备的表面平整的低折射率MgF₂薄膜,在紫外区具有很好的增透性能,同时在紫外波长355 nm激光的辐照下（脉宽6 ns）,薄膜具有较高的抗激光损伤性能,激光损伤阈值达10.85 J·cm^-2。     

提拉法SiO_2化学膜厚度与折射率的变化规律研究

采用提拉法在硅基底上制备了多孔溶胶凝胶SiO2膜,用椭偏法测量薄膜的厚度与折射率,考察了提拉速度和胶体浓度对膜层厚度与折射率的影响。对厚度与提拉速度的关系进行线性与幂函数拟合,并比较分析两种拟合的关系及其对工艺流程的作用。比较了不同浓度胶体所得到的同一厚度薄膜的折射率变化规律。结果表明:对于同一胶体浓度下薄膜厚度与提拉速度的正相关关系,线性拟合相比幂函数拟合可以更好地解释实验结果的规律性。同时,折射率在一定范围内也会随着提拉速度的增加而减小。镀同一厚度膜时,浓度大的胶体膜层折射率大。通过对提拉速度和胶体浓度的控制可以得到理想的薄膜厚度与折射率。     

溶胶-凝胶法MgF2紫外增透膜的制备和性能研究

采用溶胶-凝胶法,以醋酸镁和氟化氢为原料,以甲醇为溶剂制备了MgF2溶胶,利用浸渍提拉法在洁净石英基片上镀膜,考察了反应温度对溶胶微结构、薄膜结构和性能的影响。样品采用激光动态光散射、透射电镜、X射线粉体衍射仪、紫外-可见光谱仪、原子力显微镜进行表征。结果表明：通过该方法制备的表面平整的低折射率MgF2薄膜,在紫外区具有很好的增透性能,同时在紫外波长355 nm激光的辐照下（脉宽6 ns）,薄膜具有较高的抗激光损伤性能,激光损伤阈值达10.85 J·cm-2。     

Effect of ammonia treatment on laser-induced damage of nano-porous silica film

The sol-gel monolayer silica films on K9 glass substrates were prepared with the dip method, and then treated in saturated ammonia gas. The laser-induced damage threshold (LIDT) of silica films with and without ammonia treatment was measured. Properties of the films were analyzed by using Stanford photo-thermal solutions (SPTS), ellipsometry, atomic force microscopy (AFM), and optical microscopy to study the effect of ammonia treatment on laser-induced damage of sol-gel monolayer silica film under laser irradiation. The experimental results showed that compared with the as-grown silica film, the silica film with ammonia treatment had larger absorption and smaller porous ratio, and it had smaller LIDT. Considering the improved abrasion resistance of films with ammonia treatment, a trade-off is always needed between abrasion resistance and LIDT in practice.     

溶胶-凝胶工艺制备SiO2薄膜的结构控制和稳定性研究

 采用溶胶-凝胶工艺在酸性、碱性和碱/酸两步催化条件下制备纳米多孔结构的SiO₂薄膜。使用透射电子显微镜（TEM）、激光粒子分析仪测试了溶胶的微观结构和颗粒分布;使用反射式扫描椭偏仪、扫描电子显微镜（SEM）、原子力显微镜（AFM）测试了薄膜的光学性能和微观形貌。结果表明：通过改变溶胶-凝胶过程中的催化条件可控制薄膜微观结构和光学性能。溶胶在长期存贮期间符合镀膜的稳定性要求。     

银纳米膜的电化学制备方法及性能表征

采用电沉积方法在表面活性剂与电解液的界面上制备了银纳米膜。通过对甲磺酸银体系和硝酸银体系中纳米银膜的电沉积速率及纳米银膜颗粒进行比较发现，相同条件下硝酸银体系得到的纳米膜晶粒粒径比较小，膜的生长速率较快。选定硝酸银体系为电沉积体系。考察了槽压、电解液的浓度和温度及溶液的pH值对制备银纳米膜的影响，确立了制备银纳米膜的最佳工艺条件为硝酸银浓度5mmol/L，槽压4V，pH3.0,硬脂酸的质量浓度0.2g/L。实验表明，最佳工艺条件下制备的银纳米膜晶粒粒径均匀，平均粒径在20nm左右，近似球形。本方法制备的银纳米膜将在非线性光学材料方面得到应用。     

Effect of hydrogen dilution on the silicon cluster volume fraction of a hydrogenated amorphous silicon film prepared using plasma-enhanced chemical vapor deposition

We investigated the effect of hydrogen dilution on the Si cluster volume fraction of hydrogenated amorphous films by varying the hydrogen dilution ratio at 0.5 Torr and compared it to that obtained at pure silane discharge at 0.3, 0.4, and 0.5 Torr. The correlation between the plasma emission characteristic, deposition rate, and cluster volume fraction in the hydrogen dilution plasma was described. The cluster volume fractions of films under hydrogen dilution conditions were similar to those of the pure silane but showed a higher deposition rate. The results suggest that under hydrogen dilution conditions, it is possible to maintain a higher deposition rate with a lower cluster incorporation rate.     

氧等离子体处理对氧化锆薄膜性质的影响

用低能氧等离子体对电子束热蒸发后的沉积氧化锆薄膜进行了后处理。通过对其光学性质、缺陷密度、弱吸收及抗激光辐照等性质的研究后发现,经氧等离子体处理后的氧化锆薄膜的折射率、消光系数、缺陷密度及吸收率等均有所降低,薄膜的激光损伤阈值较未处理的样品有了较大的提高。分析探讨了氧等离子体处理技术对薄膜性质的影响。     

The nature of radiative centers formed by nonbridge oxygen in especially pure sol-gel glasses

We carry out measurements of the optical absorption of sol-gel quartz glasses that have been exposed to γ-radiation. The dependence of optical density on irradiation dose is analyzed, and two types of centers formed by nonbridge oxygen are distinguished. We revealed a difference in the peak wavelengths of absorption bands with an energy of 2.0 eV for various types of centers. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 600–603, July–August, 1998.     

Oxidation of Ni(Pt)Si by molecular vs. atomic oxygen

X-ray photoelectron spectroscopy (XPS) has been used to characterize the oxidation of a clean Ni(Pt)Si surface under two distinct conditions: exposure to a mixed flux of atomic and molecular oxygen (O + O₂; PO+O₂ = 5 × 10⁻⁶ Torr) and pure molecular oxygen (O₂; PO₂ = 10⁻⁵ Torr) at ambient temperatures. Formation of the clean, stoichiometric (nickel monosilicide) phase under vacuum conditions results in the formation of a surface layer enriched in PtSi. Oxidation of this surface in the presence of atomic oxygen initially results in formation of a silicon oxide overlayer. At higher exposures, kinetically limited oxidation of Pt results in Pt silicate formation. No passivation of oxygen uptake of the sample is observed for total O + O₂ exposure <8 × 10⁴ L, at which point the average oxide/silicate overlayer thickness is 23 (3) Å (uncertainty in the last digit in parentheses). In contrast, exposure of the clean Ni(Pt)Si surface to molecular oxygen only (maximum exposure: 5 × 10⁵ L) results in slow growth of a silicon oxide overlayer, without silicate formation, and eventual passivation at a total average oxide thickness of 8(1) Å, compared to a oxide average thickness of 17(2) Å (no silicate formation) for the as-received sample (i.e., exposed to ambient.) The aggressive silicon oxidation by atomic oxygen, results in Ni-rich silicide formation in the substrate and the kinetically limited oxidation of the Pt.     

Effect of poly silicon thickness on the formation of Ni-FUSI gate by using atomic layer deposited nickel film

The effect of poly-Si thickness on silicidation of Ni film was investigated by using X-ray diffraction, auger electron spectroscopy, cross-sectional scanning transmission electron microscopy, resistivity, I–V, and C–V measurements. The poly-Si films with various thickness of 30–200 nm were deposited by LPCVD on thermally grown 50 nm thick SiO₂, followed by deposition of Ni film right after removing the native oxide. The Ni film was prepared by using atomic layer deposition with a N²-hydroxyhexafluoroisopropyl-N¹ (Bis-Ni) precursor. Rapid thermal process was then applied for a formation of fully silicide (FUSI) gate at temperature of 500 °C in N₂ ambient during 30 s. The resultant phase of Ni-silicide was strongly dependent on the thickness of poly-Si layer, continuously changing its phase from Ni-rich (Ni₃Si₂) to Si-rich (NiSi₂) with increasing the thickness of the poly-Si layer, which is believed to be responsible for the observed flat band voltage shift, ΔV_FB, in C–V curves.     

Etching of silicon nanowires on Ag(1 1 0) by atomic hydrogen

Scanning Tunnelling Microscopy, High Resolution Electron Energy Loss Spectroscopy and High Resolution X-Ray Photoelectron Spectroscopy have been used to study the adsorption of atomic hydrogen onto Si nanowires grown on Ag(1 1 0). We demonstrate that the hydrogen strongly interacts with the Si nanowires modifying their structural and electronic properties. Hydrogen atoms etch the Si nanowires and eventually lead to their complete removal from the Ag(1 1 0) surface.     

高通量中性原子氧束流的发生与控制

 采用微波同轴耦合氧气放电产生高密度氧等离子体, 经磁场约束后与一施加负偏压的金属板碰撞复合并反射, 得到通量在10¹³~10¹⁶atom/cm²×s范围可控, 动能约为6-10eV的中性氧原子束流。用双探针技术对生成的氧等离子体进行了诊断测量。根据聚酰亚胺在原子氧作用下的剥蚀率对原子氧束流进行了标定测量。