Substrate Surface Microstructure Research Articles

Wettability of molten Na2CO3–K2CO3 on coal fly ash ceramic substrates with expanded graphite

The wettability of materials influences highly the stability of form-stable phase change materials (FSPCMs). In this study, the wetting behavior of Na2CO3–K2CO3 on the coal fly ash (CFA) ceramic substrates with different expanded graphite (EG) contents was studied through contact angle measurements at 707 °C. The influences of surface microstructure of substrates, adhesion of molten salt to the substrates, and salt infiltration during the contact angle measurements were taken into consideration. The results found that the eutectic carbonate salt on the CFA ceramic substrates generally showed a good wettability, which can be influenced by the surface microstructure of the CFA ceramic substrates and the adhesion of molten salt to the substrates. Due to the presence of salt infiltration phenomenon during the experiments, the measured contact angle should be modified to eliminate the infiltration effect. Increasing the EG content in the substrates caused a decrease of surface roughness of substrate and salt infiltration, resulting in the evident increase of modified contact angle. Besides, using high forming pressure of the prepared substrate also decreased the surface cracks and surface roughness, and increased the modified contact angle.

Microstructure and magnetic properties of Ta/Ni81Fe19/Ta tri-layer thin films on mono-like cast silicons

The microstructure and magnetic properties of Ta/Ni81Fe19/Ta tri-layer thin films on three types of mono-like cast silicon substrates (flat, upright pyramid and inverted pyramid surfaces) were investigated. Results show that the surface topography structures of the films followed those of the substrates generally. But the thickness of the film on pyramid surface increases from the pyramid tip to the bottom. This is caused by the anisotropical diffusion of incident atoms/ions on the pyramid surfaces during the film growth process. The films on pyramid structured substrates have smaller saturation magnetizations but larger in-plane coercivity than that of on the flat substrate. This should be mainly caused by the non-zero angle between the magnetic field and the substrates as suggested by the angular dependent magnetic properties of the films. The hysteresis loops measured from in-plane to out-of-plane directions show that the coercivities of films on all the mono-like cast silicons are highly angular dependent. A further post-annealing of the films suggests that the magnetic properties of the films are dominantly determined by the surface microstructure of substrates instead of the fabrication conditions. The above results can help better integration of NiFe thin films on mono-like cast silicon based devices.

Microstructured SiOx thin films deposited from hexamethyldisilazane and hexamethyldisiloxane using atmospheric pressure thermal microplasma jet

Mictrostructured silicon oxide (SiOx) thin films were deposited on glass and metal substrates from 1,1,1,3,3,3-hexamethyldisilazane (HMDSN) and hexamethyldisiloxane (HMDSO) by using atmospheric-pressure thermal microplasma jet. Two kinds of string-like products, randomly bent string-like products and linear string-like products, were deposited and they formed microstructured films. The bent string-like products formed labyrinth-like structures and the linear string-like products lay in parallel to form a large aligned structure. The width of both the bent and linear string-like products was from 1 to 3 μm, regardless of the kind of the precursor but depending on the plasma irradiation conditions. The influence of various surface microstructure of substrates on the formation of the SiOx microstructure was investigated to make clear the mechanism for the formation of the microstructures.

Influence of sputtering pressure on microstructure and layer properties of iridium thin films

Iridium layers with low stress, high density, and low surface roughness find widespread use in different high-technology applications. This paper presents a study of the influence of the sputtering pressure on the properties of iridium thin films and of its effect on the substrate surface microstructure. We analysed the dependence of the microstructure, crystalline structure, electrical resistivity, and deposition rate on the sputtering pressure and surface defects of the substrate. For the latter, plasma etching of the substrate was performed for different processing times and its effect on the surface roughness of substrates and, subsequently, on the grown iridium films, was examined. The sputtering pressure and the substrate plasma etching time both had a strong influence on the microstructure and surface roughness. These microstructural changes are in good agreement with the tendency described in the Thornton Structure-Zone Model for different sputtering pressures and the microstructure phase map of Alvarez. The electrical resistivity, deposition rate, and crystalline structure were highly dependent on the sputtering pressure.

Performance of photocatalytic cementitious material: Influence of substrate surface microstructure

Photocatalytic cementitious material (PCM) was prepared by porous magnesium oxychloride cement (PMOC) and TiO2 photocatalyst. Influences of PMOC substrate surface microstructure on TiO2 loading and photocatalytic performance had been investigated. The results revealed that loading effect mostly depends on PMOC substrate surface microstructure which could be controlled by its curing age. Appropriate interlaced microstructure enhanced TiO2 dispersity, loaded mass and adsorption capability. PCM-14d specimen (14-day curing before TiO2 loading) had the best photocatalytic performance, which could completely purify toluene (200ppm) within 80min. Practical simulation experiment indicated that PCM-14d specimen was 1.3 times better than nickel foam based photocatalytic material.

Effect of Substrate Surface Microstructure on Heterogeneous Nucleation Behavior

The heterogeneous nucleation behaviors of NH4Cl crystal on a rough chilling surface of aluminum immerged in NH4CI-H2O solution were experimentally analyzed and the relationship between the surface roughness and the nucleation site selection behaviors on polished aluminum substrate was investigated, and it was discovered that the number of nucleation sites decreases significantly with decreasing the roughness of the polished substrate. Further nucleation experiments were carried out on chemically etched aluminum substrate with regular micro-morphology on its surface. It has been shown that both the micro-morphology and the wettability vary with the substrate surface prepared by different etching process. The prepared surface with step-like structures has a strong wettability with NH4Cl-70 wt% H2O solution and the nucleation density of NH4Cl on the its surfaces is significantly higher than that of the reference surfaces, which shows that the geometrical morphology features have important effects on both the wettability and the nucleation behaviors.

Oriented growth and assembly of zeolite crystals on substrates

The aligned array and thin film of zeolites and molecular sieves possess a variety of potential applications in membrane separation and catalysis, chemical sensors, and microelectronic devices. There are two main synthesis methods for manufacturing the aligned arrays and thin films of zeolites and molecular sieves, i.e. in situ hydrothermal reaction and self-assembly of crystal grains on substrates. Both of them have attracted much attention in the scientific community worldwide. A series of significant progress has been made in recent years. By the in situ hydrothermal synthesis, the oriented nucleation and growth of zeolite and molecular sieve crystals can be achieved by modifying the surface properties of substrates or by changing the composition of synthesis solutions, leading to the formation of uniformly oriented multicrystal-aligned arrays or thin films. On the other hand, the crystal grains of zeolites and molecular sieves can be assembled onto the substrate surface in required orientation using different bondages, for instance, the microstructure in the array or thin film can be controlled. This review is going to summarize and comment the significant results and progress reported recently in manufacturing highly covered and uniformly aligned arrays or thin films of zeolites and molecular sieves. It involves (1) in situ growth of highly aligned zeolite arrays and thin films via embedding functional groups on the substrate surface, modifying the surface microstructure of substrates, as well as varying the composition of synthesis solutions; (2) assembly of zeolite and molecular sieve crystals on various substrates to form aligned arrays and thin films with full coverage by covalent, ionic, and intermolecular coupling interactions between crystals and substrates; (3) coupling surface assembly with microcontact printing or photoetching technique to produce patterned zeolite arrays and thin films. Finally, the functionality and applications of zeolite arrays and thin films are briefly introduced. Some critical issues are addressed for future studies.

薄膜媒体の面内磁気異方性の考察

The macroscopic in-plane magnetic anisotropy induced in Co-alloy thin-film media deposited on textured substrates, arises mainly from the orientation of easy magnetization axis of the Co-alloy in the circumferential direction. This anisotropy correlates with in-plane distortion of the crystal structure of the Cr under layer. Correlation between the substrate surface microstructure and distortion of the Cr crystal structure was investigated as an effect of anisotropic stress caused by the thermal expansion of substrates. We found that the Cr crystal structure becomes distorted, and a large magnetic anisotropy is induced, when the grain size is less than half the width of texture grooves. In this case, the different thermal expansion coefficients of NiP and Al make the thermal strain of the inclined plane of texture grooves larger in the circumferential direction than in the radial slope direction. The stress on Cr grains from the substrate surface therefore becomes anisotropic and induces distortion of the Cr crystal structure. The anisotropic stress also correlates with the in-plane magnetic anisotropy.

Atomic Force Microscopy Study of Nickel Oxide Films Modified by Reactive Element

ABSTRACTThe evolution of microstructure of thin oxide films during growth has been quantitatively analysed by atomic force microscopy (AFM). The oxide films were formed in pure oxygen atmosphere at temperatures ranging from 873 to 1173 K on polycrystalline nickel substrates. The substrates were both pure and superficially modified by nanometer-sized dispersions of CeO2. The incorporation of reactive element into the oxide inhibits the growth kinetics and affects the microscopic surface morphology. The extent of this effect depends essentially on the substrate surface microstructure prior to modification and the size of CeO2 particles. A correlation was found between the surface topography and the reduction of oxide growth rate caused by the reactive element.

High resolution electron microscope study of epitaxial CdTe-GaAs interfaces

CdTe films have been grown on (100) GaAs substrates with two different epitaxial relations: (111)CdTe∥(100)GaAs and (100)CdTe∥(100)GaAs. High resolution electron microscope observation of these two types of interfaces was carried out in order to investigate the role of the substrate surface microstructure in determining which type of epitaxy occurs. The interface of the former type shows a direct contact between the CdTe and GaAs crystals, while the interface of the latter type has a very thin layer (∼10 Å in thickness), which is most likely an oxide, between the two crystals. These observations suggest that the GaAs substrate preheating cycle prior to CdTe film growth is crucial in determining which type of epitaxy occurs in this system.

Observation of the CdTe-GaAs Interface by High Resolution Electron Microscopy

AbstractCdTe films have been grown on GaAs substrates with two types of interfaces - one with the epitaxial relation (111)CdTe║ (100)GaAs and the other with (100)CdTe║ (100)GaAs,. High resolution electron microscope observation of the two types of interfaces was carried out in order to determine the role of the substrate surface microstructure in determining the epitaxy. The interface of the former type shows a direct contact between the CdTe and GaAs crystals, while the interface of the latter type has a very thin oxide layer (∼10 Å in thickness) between the two crystals. These observations suggest that details of the substrate preheating cycle prior to film growth is the principle factor in determining which epitaxial relation occurs in this system. The relation between interfacial structures and the origin of the two epitaxial relations is discussed.