Albedo parameter-based characterization of surface roughness in chemically etched zirconium samples.

Chemical etching is usually utilized to measure, reduce, and remove the subsurface micro-cracks in optical components, which makes it significant to study the surface evolution of optical components during the etching process. Etching experiments were carried out for glass with artificial cracks and micro-cracks under different etching conditions. The etching rate was obtained, which is linear with the hydrofluoric acid (HF) concentration and greatly affected by etching temperature. By measuring the surface roughness (SR) and morphology of glasses after etching, it is found that the crack width always increases with etching time, while the crack depth remains unchanged after the crack is completely exposed. Meanwhile, the SR increases sharply at first, then increases slowly, and finally decreases with the increase of etching time. Considering the influence of HF concentration, etching temperature, and the diffusion coefficient on the etching rate, simulation models were established for etching trailing indent cracks (TICs) to further analyze the evolution of SR and morphology. The simulation results were compared with the experimental ones, also indicating that the maximum SR (Ra) increases greatly with the crack's aspect ratio and the model for analyzing the crack's morphology evolution is more reasonable.

Wettability is one of the important properties of solid surfaces from both fundamental and practical aspects. Among various factors, surface energy and roughness are the dominant factors for the wettability. Static wettability, that is, water contact angle (WCA) has been commonly used as a criterion for the evaluation of hydrophobicity of solid surface. In recent years, WCA can be designed easily by controlling surface energy and roughness based on Young’s, Wenzel’s, and Cassie’s equations. On the other hand, dynamic wettabilities such as sliding property on the hydrophobic surface are poorly undersutood. Although water sliding angle (WSA: the critical angle where a water droplet with a certain weight begins to slide down the inclined plate) and contact angle hysteresis (the cosine of receding contact angle minus that of advancing contact angle) are often measured to evaluate the water-repellent property of the hydrophobic surface, comprehensive understanding of the water-repellent properties is still limited because the relationships between the WSA and the WCA are not clear [1-2]. In this study, we used nanoporous silicon surfaces with different surface morphologies, which were formed by metal-assisted chemical etching using Ag nanoparticles, as a solid surface. Static and dynamic wettabilities of their surfaces were investigated with focusing on the influences of pore size and surface roughness on wettability of porous silicon surfaces. p-type silicon (100) substrates were immersed in a mixed solution of 2×10-2 mol dm-3 AgNO3 and 5 mol dm-3 HF to deposit Ag particles on the entire surface of silicon substrates. After deposition of Ag particles, silicon substrates were immersed in a mixed solution of 10 mol dm-3 HF and 1 mol dm-3 H2O2at room temperature at different time. SEM images of obtained porous silicon after etching with different surface roughness are shown in Fig. 1. WCAs (approximately 135°) of etched silicon were higher than that of flat silicon (75°), presumably due to decrease of contact area between porous structure and droplet based on Cassie’s model. Although surface roughness increased with increasing etching time, however, WCAs of etched silicon were about the same (135°) despite the difference in surface morphologies (Fig. 1a-c). On the other hand, WSAs increased with increasing surface roughness. The changes in WSAs were thought to be caused by the pinning effect generated by increase of pore diameter and surface roughness during chemical etching. These results indicate that WSA is affected more significantly by physical inhomogeneity such as surface roughness of the etched surface than WCA. [1] M. Miwa, A. Nakajima, A. Fujishima, K. Hashimoto, T. Watanabe, Langmuir, 16, 5754-5760 (2000). [2] S. Suzuki, A. Nakajima, Y. Kameshima, K. Okada, Surface Science Letters, 557, L163-L168 (2004). Figure 1

Si-based semiconductor devices are not suitable for stable operations in the aerospace environments. Among the ultra-wide bandgap semiconductor materials, gallium oxide (Ga2O3) is attracting attention as the next-generation material for high-power semiconductor devices in extreme condition beyond Si, owing to its large band gap of 4.5-5.3 eV, high breakdown electric fields of 7-10 MV/cm, excellent chemical and thermal stability and radiation hardness. Alpha gallium oxide (α-Ga2O3) has the largest bandgap (4.8-5.3 eV) and the highest breakdown electric fields (~10 MV/cm) among the five Ga2O3 polymorphs, which facilitates the application of α-Ga2O3 as a high power device. However, the research on etching technology for α-Ga2O3 is rare. Etching technology is a crucial step of device fabrication. Chemical etching is free from plasma-induced damage which leads to superior device performance compared with dry etching, and high throughput with low cost is beneficial to industrial implementations. Chemical stability of Ga2O3 hinders the effective reaction with most chemical etchants. However, the photo-enhanced inverse metal assisted chemical (I-MAC) etching, where a noble metal with a high work function is utilized as a catalyst under UV irradiation, has emerged as a candidate for the chemical etching of Ga2O3. Deep-UV irradiation generates electron-hole pairs (EHPs) in the uncovered region of Ga2O3, and the metal electrode withdraws carriers from the photo-generated EHPs. The holes that are accumulated in the uncovered region of Ga2O3 react with gallium ions which produce gallium fluoride (GaF3) in a reaction with Hydrofluoric acid (HF). The etching process continues as the oxidant re-oxidizes the metal. The etch rate can be controlled by various parameter, including concentration and temperature of the etchant. In this work, for the I-MAC etch of α-Ga2O3 on sapphire substrate grown by halide vapor phase epitaxy, Pt was deposited on α-Ga2O3. Etch rate and surface roughness were characterized by atomic force microscopy after each step of the I-MAC etch. The I-MAC etch using HF and potassium persulfate (K2S2O8) solution with 185-nm UV irradiation was performed at constant durations under different etchant temperature conditions. The etch rates obtained at each temperature condition were fitted with the Arrhenius plot to estimate the activation energy of 0.898 eV. The etch depth showed a linear increase with time and the etch rate exhibits a direct dependency on the temperature of the etchant, indicating that the I-MAC etching of α-Ga2O3 is an activation-controlled reaction. As the I-MAC etching proceeded, surface roughness of α-Ga2O3 showed a tendency to increase. The rate at which the surface roughness increased increased with raising the etchant temperature. In the case of Pt there was no significant difference in the surface roughness after etching. After the completion of the I-MAC etch, the remaining Pt can be removed using aqua regia. The I-MAC etch process of α-Ga2O3 can allow us to fabricate α-Ga2O3 without plasma-damage. Figure 1

The aim of this study was to examine the effect of different acid etching times on the surface roughness and flexural strength of a lithium disilicate-based glass ceramic. Ceramic bar-shaped specimens (16 mm x 2 mm x 2 mm) were produced from ceramic blocks. All specimens were polished and sonically cleaned in distilled water. Specimens were randomly divided into 5 groups (n=15). Group A (control) no treatment. Groups B-E were etched with 4.9% hydrofluoric acid (HF) for 4 different etching periods: 20 s, 60 s, 90 s and 180 s, respectively. Etched surfaces were observed under scanning electron microscopy. Surface profilometry was used to examine the roughness of the etched ceramic surfaces, and the specimens were loaded to failure using a 3-point bending test to determine the flexural strength. Data were analyzed using one-way ANOVA and Tukey's test (?=0.05). All etching periods produced significantly rougher surfaces than the control group (p<0.05). Roughness values increased with the increase of the etching time. The mean flexural strength values were (MPa): A=417 ± 55; B=367 ± 68; C=363 ± 84; D=329 ± 70; and E=314 ± 62. HF etching significantly reduced the mean flexural strength as the etching time increased (p=0.003). In conclusion, the findings of this study showed that the increase of HF etching time affected the surface roughness and the flexural strength of a lithium disilicate-based glass ceramic, confirming the study hypothesis.

The chemical etching properties of ferroelectric LiTaO3 crystal in near-stoichiometric compositions were quantitatively investigated with various ratios of HF and HNO3 acid mixtures by scanning force microscopy in the nanoscale range. Along with congruent LiTaO3 crystal, the −Z surfaces of near-stoichiometric LiTaO3 crystal were etched preferentially with pure HF acid and mixtures of HF and HNO3 acids. The etching rates on the −Z surface of near-stoichiometric LiTaO3 crystal were slower than that of congruent LiTaO3 crystal. The roughness (peak to peak) of etched surfaces were about 2nm after being etched in all ratios of HF and HNO3 acids to a 70-nm etch depth. The temperature dependence of the etch rate followed the Arrhenius law. By taking advantage of the chemical preferential etching properties, precision surface structures could be fabricated on near-stoichiometric LiTaO3 crystal.

Effect of substrate roughness and film thickness on the magnetic properties of CoFeB films on polymer substrate

GaN etch rate and surface roughness evolution in Cl2/Ar based inductively coupled plasma etching

The present paper discusses the development of the first and second order model for predicting the chemical etching variables, namely, etching rate, surface roughness and accuracy of advanced ceramics. The first and second order etching rate, surface roughness and accuracy equations were developed using the Response Surface Method (RSM). The etching variables included etching temperature, etching duration, solution and solution concentration. The predictive models’ analyses were supported with the aid of the statistical software package – Design Expert (DE 7). The effects of the individual etching variables and interaction between these variables were also investigated. The study showed that predictive models successfully predicted the etching rate, surface roughness and accuracy readings recorded experimentally with 95% confident interval. The results obtained from the predictive models were also compared with Multilayer Perceptron Artificial Neural Network (ANN). Chemical Etching variables predictive by ANN were in good agreement with those with those obtained by RSM. This observation indicated the potential of ANN in predicting chemical etching variables thus eliminating the need for exhaustive chemical etching in optimization.

Surface quality of the substrate is widely acknowledged to be essential for the niobium thin film deposition. Much effort has thus been spent to improve the surface roughness by using various chemical etching techniques. However, surface preparation before the chemical etching also plays a part in obtaining a satisfactory substrate, but has rarely been studied before. This paper aims to define a specification for the pre-polished copper substrate prior chemical etching and searches for suitable alternative non-chemical grinding methods for the copper cavity. Copper samples were mechanically pre-polished at first by using flap sanding wheels of different grits and then chemically etched by using the well-established SUBU solutions. Surface roughness, as a figure of merit, was measured and compared before and after SUBU. Optimum practice for pre-polishing may therefore be determined. The mechanical grinding was subsequently applied on the 1.3-GHz mono-cell copper cavity. Meantime, the previously reported centrifugal barrel polishing method was also applied with new abrasive materials and modified schemes. A comprehensive study of etching rate, surface roughness and morphologies was conducted. The specification for surface roughness prior SUBU was determined. Due to a complex geometry and curved surfaces possessed by the 1.3-GHz copper cavity, the traditional mechanical grinding was proved to be not ideal. Satisfactory surface quality was obtained by using the alternative centrifugal barrel polishing on the cavity. The proposed new scheme and new abrasive materials were demonstrated to be effective, and a mirror-like surface was achieved on the copper cavity. The traditional mechanical grinding can therefore be replaced. This constitutes a dedicated study on pre-polishing of the 1.3-GHz copper cavity substrate prior chemical etching for niobium sputtering.

Surface patterning is one of importance aspect in the development of a QCM biosensor. This paper describes a method by which a KOH (Potassium Hydroxide) etchant is utilized for the pattern formation on the surface of the quartz crystal sensor. The etching process is preferable in order to produce a flat surface roughness. The etchant concentration affects etching rate and surface roughness. In this experiment, the effect of etchant concentration on the etching rate and surface roughness was investigated. The etching of the quartz crystal was carried out using KOH concentration of 25 %, 30% and 35 % by weight at a temperature of 80°C for 2 hours. Aurum palladium (AuPd) was used as a mask to protect the rest of the quartz crystal. The AuPd mask was coated on the quartz crystal by a sputter coater in a high vacuum chamber. The etched surfaces were observed using a white light profilometer TMS 1200. The results show that best anisotropic patterns formation were obtained in 30% wt KOH solution. Furthermore, the TMS indicates that the surface roughness of the etched surface tends to increase with the increasing of KOH concentration.

Influences of deformation defects on etching behaviors of high-strength and high-conductivity Cu alloy for lead frame

AFM and SEM study of the effects of etching on IPS-Empress 2 TM dental ceramic

Objective: To evaluate and compare the influence of fiber post surface treatments (Er,Cr:YSGG laser sandblasting, and 9% hydrofluoric acid ) on surface roughness and morphology. Materials and Methods: A total of sixty fiber posts were used in this study. They were randomly divided into 4 groups according to surface treatment method into: Group I: control (no pretreatment), Group II: sandblasting (Al2O3), Group III: etch 9% hydroflouric acid etching , Group IV: Er,Cr:YSGG laser iradiation (2790 nm) .Group IV was further subdivided according to laser power to; subgroup A: 0.5W, subgroup B: 1W, subgroup C: 1.5W. Surface roughness (Ra) of the posts before and after surface treatment was measured using surface profilometer. The posts were examined under SEM for assessment of surface morphology. One-way ANOVA followed by Tukey post hoc test was used to compare between more than two groups in non-related samples. Results: There was statistical significant difference in the Ra value between the control group and all the tested groups (p&lt;0.001). Sandblasting showed the highest significant mean Ra value while hydrofluoric acid had the lowest significant values. Conclusion: All the tested surface treatments method increased the surface roughness, and changed the surface morphology of the tested fiber posts.

Surface etching before cementation is a vital step that determines the clinical performance of ceramic restorations. Etching alters surface topography that contributes effective bonding between ceramic restoration and resin cement. This study aimed to compare etching techniques to determine the most effective etching method contributing the highest bond strength that helps in improving dental implants. Materials and methods: sixty discs of feldspathic ceramic measuring 10 mm diameter and 4 mm thickness were prepared. The 60 samples were divided into four equal groups based on the surface treatment technique used: group A: 9.6% hydrofluoric acid; group B: coarse diamond burs; group C: CO2 laser; and group D: no treatment. Ceramic disc specimens were examined under a Scanning Electron microscope (SEM) after surface treatment to characterize their surface morphology. Further, the specimens were luted with a resin luting agent and incubated for 24 h at a temperature of 37 °C simulating the oral environment. After 24 h, shear bond strength (SBS) and the nature of bond failure was determined for each specimen using a universal Instron testing machine. Results: significant change in surface morphology was noticed on hydrofluoric acid treatment forming larger irregular roughness (4.83 ± 1.78 µm) with multiple patterns of grooves and pores compared to other groups. Further, the highest SBS value was measured on hydrofluoric acid etching that display the highest bond strength due to the high surface roughness. In conclusion, our findings report a strong association between the surface roughness and bond strength upon hydrofluoric acid compared to other methods. Further work in this direction will enhance the utility of the etching technique on the improvement of dental implants.

Etch characteristics and mechanisms of TiSbTe thin films in inductively coupled HBr-He, HBr-Ar, HBr-N2, and HBr-O2 plasmas were studied in this paper. The etch rate of TiSbTe thin film was measured as functions of the additive gas fraction for He, Ar, N2 and O2 at a fixed gas pressure (5 mTorr, 1 mTorr = 0.133Pa), input power (700 W), bias power (300 W), and total gas flow rate (200 sccm). The etch rate and surface roughness of TiSbTe thin films showed non-monotonic behaviors as the increasing additive gas fraction in four plasma systems. Meanwhile, different kinds of additive gas resulted in different quantitative correlations between chemical and physical etching pathway, which eventually make difference on the etch rate and surface roughness of TiSbTe thin film. The surface chemical status of each component was also investigated in this study. The good performance of etch rate, surface roughness and low plasma damage suggested that HBr-Ar plasma is the best choice for TiSbTe etching compared with HBr-He, N2 and O2 plasma.