Papers by Keyword: Substrate

Abstract: Information on deformation of coatings at different loading levels during peeling is given. It is shown that the deformations of the organosilicon coating appear already at the initial stages of loading, and the obtained data correlate with the data on acoustic emission. For a polyvinyl acetate coating at low loading levels, equal to 0.3-0.4 R, the release of acoustic signal energy is not observed. The absence of signals with a large amplitude at loading levels up to 0.7-0.8 R indicates the development of plastic deformations in the contact zone of the coating with the substrate. It was found that early localization of bond breaking in the contact zone, leading to the formation of a fracture focus, occurs in organosilicon coatings KO-168. For PVAC coatings, an abrupt growth of cracks is characteristic, which is preceded by its slow growth. The pseudoplastic mechanism of destruction of PVAC coatings has been established. The influence of the nature of the substrate on the change in the nature of the peeling of the coatings is considered.

Abstract: The influence of the main structure-forming oxides Li₂O/Al₂O₃, SiO₂/Al₂O₃ and H₂O/Al₂O₃ on the physical, rheological and colloidal-chemical properties of lithium-containing alumosilicate suspensions xLi₂O-Al₂O₃-nSiO₂-mH₂O in the system are presented for the first time. As a result of optimization, the optimal area of influence of variable factors was determined for the ratio of oxides Li₂O/Al₂O₃ from 0.82 to 1.05 mol, SiO₂/Al₂O₃ from 3.4 to 4.5 mol and H₂O/Al₂O₃ from 19 to 21.5 mol, providing normative levels of properties of lithium-containing alumosilicate suspensions, namely: density from 1.4 to 1.521 g/cm³, process viscosity from 15 to 47 sec, pH from 11.15 to 11.34, surface tension from 51.4 to 60.4 mN/m, cosine of the substrate contact angle from 0, 57 to 0.91, work of adhesion forces from 97 to 116 mN/m, work of cohesion forces from 103 to 121 mN/m, work of wetting forces from 27 to 52 mN/m, wetting coefficient from 0.78 to 0.96, spreading coefficient from –5 to –20 mN/m. The data obtained will form the basis for the creation of protective materials of new generation that, in the event of emergencies, can provide both the protection of people and technological equipment, buildings and constructions.

Abstract: Information on the stress state of protective and decorative coatings during the curing process, in particular on the cohesive state of destruction, is given. The influence of the type of substrate on the change in internal stresses in the coating is considered. It was revealed that the greatest value of shear stresses is observed in coatings on a heavyweight concrete substrate. The subsequent increase in temperature after curing to 50°C leads to an increase in the value of the normal stresses. The probability of cracking of coatings during thermal aging is estimated. It was revealed that during aging there is an exponential decrease in the cohesive strength of coatings and an increase in internal stresses. Aging tends to increase the likelihood of cracking of coatings. The change in stresses in coatings as a result of seasonal fluctuations in air temperature is considered.

Abstract: It is commonly thought that, in the development of SiC power devices with low on-state resistance (R_on), several critical processes in the device fabrication line can strongly impact the final warpage of wafers. High warpage would lead to bad definition of masks, preventing uniform deposition of resist materials and disturbing the normal handling procedures. All these factors would then result in a potential decrease of the electrical yield of the devices, especially for MOSFETs. This study reveals the lack of correlation between critical line processes such as epitaxial growth, oxidations, ion implantations, annealing processes with the final bending of wafers. Conversely, a strong dependence with the resistivity of the substrates is observed. A new parameter defined as RMR (Resistivity Modulation Rate) is taken proposed and, together with the starting value of ingot resistivity, this parameter shows a strong relationship with the final warpage after wafer thinning. A safe region having warpage low enough to allow the workability of the wafers is found.

Abstract: Surface-enhanced Raman scattering (SERS) spectroscopy technology has broad application prospects in food safety, environmental monitoring, surface science and material analysis because of the characteristics of ultra-high sensitivity and non-destructive testing. However, there are still some challenges in the preparation of SERS substrates. As SERS substrates, the common colloidal noble metal nanoparticles usually show low storage stability and poor repeatability of analytical results. In order to overcome these limitations, a coaxial microfluidic spinning device was designed to prepare flexible SERS substrates in this paper. Based on the microfluidic spinning and subsequent in-situ reduction reaction of AgNO₃, novel gel fibers uniformly loaded with AgNPs were successfully prepared. The effects of the concentration of AgNO₃ solution and UV irradiation duration on the formation of AgNPs were investigated. Transmission electron microscopy (TEM) showed that the average particle size was about 2.7 nm. The gel fibers loaded with AgNPs were used as SERS substrates to detect 4-mercaptobenzoic acid (4-MBA), which showed obvious Raman enhancement effect and good repeatability. The relative standard deviation of 10 test results was 4.75%, and the detection line range was 10^-14-10^-5 mol·L^-1.

Abstract: Understanding the microstructure evolution of metal thin films on various substrates is essential for developing thin films that need specific requirements. The microstructure of thin films has been identified to be related to the mobility of the adatoms during growth. Recently, the theory of non-classical crystallisation of thin films has been introduced to explain the structure formation in chemical vapor deposition (CVD) and physical vapor deposition (PVD) processes. Much work has been conducted on CVD deposited thin films, while little data appears on PVD techniques. The effect of substrate material on the microstructure of the deposited nickel-titanium (NiTi) thin film and its optical absorbance is studied in this work. Three different substrates with identified surface conditions were used to deposit thin films of NiTi in the same chamber under the same processing conditions. The NiTi thin film was deposited using radio frequency (RF) PVD sputtering process on stainless steel (SS), aluminium (Al) and copper (Cu) substrates. The results were analysed in view of state of art structure models and mechanisms. The microstructure was studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The optical absorbance was measured by spectrophotometery. The results have shown that the structure and morphology of the grown films have varied in all conditions. Amorphous structures were obtained for Al and Cu substrates, while crystalline structures were obtained for the stainless-steel substrate at the same sputtering conditions.

Abstract: The article is intended to convince the reader of the need to characterise the contact of the adhesive with the substrate. The concept of contact layer and intensity of adhesive interaction is introduced. The specific examples demonstrate the effectiveness of the proposed approach for solving boundary problems with stress concentration The Cauchy problem in this case is strictly solved.

Abstract: As a promising third generation semiconductor material, gallium nitride (GaN) has become a research hotspot in optoelectronic field nowadays. In this paper, GaN thin films were grown by radio frequency (RF) planar magnetron sputtering of a powder GaN target in a pure nitrogen atmosphere at (0.2 – 2.0) Pa, (10 - 100) W onto various substrates such as GaAs (100), Si (100), Si (111), Al₂O₃(0001) and glass without any buffer layer. A clear phase transition from the metastable cubic zinc-blende (c - ZB) to the stable hexagonal wurtzite (h - WZ) dependence on substrates has been found in the GaN thin films. And the phase transition of GaN films were studied by X-ray diffraction (XRD), photoluminescence (PL) and Raman spectroscopy.

Abstract: In this work a deep investigation of the dislocation on 4H-SiC substrate has been shown. The dislocation intersecting the surface were enhanced by KOH etching at 500 deg. C. performed on whole 6 inches substrate. A comparison between basal plane dislocations and threading screw dislocations in the substrate with the defects in the epitaxial layer (mainly stacking faults and carrots) was performed. The comparison between shows a correlation between basal plane dislocations density and stacking faults density maps.

Abstract: We report on the results of intense third party evaluation of the COLD SPLIT technology. In total nine different SiC manufactures supplied test material. The results confirm the tremendous potential of the technology with total kerf losses per wafer of less than 100μm. Furthermore, our general approach led to comparable results for all vendors. The vendor specific difference like lateral doping level were addressed via control loops in our lasering process. These loops take crystal properties into account and adjust the applied laser energy and the depth of the laser process accordingly. Even the current best case results of sub 80μm split loss per wafer are dominated by systematic effects, which are addressed by continuous improvement efforts.