Effect of substrate morphology on the roughness evolution of ultra thin DLC films

The effect of substrate roughness on growth of ultra thin diamond-like carbon (DLC) films has been studied. The ultra thin DLC films have been deposited on silicon substrates with initial surface roughness of 0.15, 0.46 and 1.08 nm using a filted cathodic vacuum arc (FCVA) system. The films were characterized by Raman spectroscope, transmission electron microscope (TEM) and atomic force microscopy (AFM) to investigate the evolution of the surface roughness as a function of the film thickness. The experimental results show that the evolution of the surface morphology in an atomic scale depends on the initial surface morphology of the silicon substrate. For smooth silicon substrate (initial surface roughness of 0.15 nm), the surface roughness decreased with DLC thickness. However, for silicon substrate with initial surface roughness of 0.46 and 1.08 nm, the film surface roughness decreased first and then increased to a maximum and subsequently decreased again. The preferred growth of the valley and the island growth of DLC were employed to interpret the influence of substrate morphology on the evolution of DLC film roughness.     

Perception of Pitch and Roughness in Vocal Signals with Subharmonics

Pitch and roughness were rated according to the extent of amplitude modulation (AM) and frequency modulation (FM) of a subharmonic [fundamental frequency (F0)/2]. The objective was to determine the identification boundaries for pitch and roughness and to discover how both kinds of modulation affect these boundaries. Another objective was to judge the reliability between subjects when identifying subharmonic-related pitch and roughness. Three procedures were used: ABX comparisons, method of adjustment, and rating of roughness. Results indicated that the crossover point to the lower pitch (associated with the subharmonic) occurred between 10% and 30% modulation, depending on modulation type and F0. Subjects demonstrated highly variable perceptions of pitch and roughness, with poor intersubject reliability.     

Wetting mode transition of nanoliter scale water droplets during evaporation on superhydrophobic surfaces with random roughness structure

During evaporation, shape changes of nanoliter-scale (80-100 nL) water droplets were evaluated on two superhydrophobic surfaces with different random roughness (nm-coating, μm-coating). The square of the contact radius and the square of the droplet height decreased linearly with evaporation time. However, trend changes were observed at around 170 s (nm-coating) and around 150 s (μm-coating) suggesting a wetting mode transition. The calculated droplet radii for the wetting mode transition from the average roughness distance and the average roughness height of these surface structures were approximately equal to the experimental values at these trend changes. A certain level of correlation between the roughness size and droplet radius at the wetting mode transition was confirmed on surfaces with random roughness.     

二氧化钛薄膜表面粗糙度研究

为了探究二氧化钛(TiO₂)薄膜表面粗糙度的影响因素, 利用离子束辅助沉积电子束热蒸发技术对不同基底粗糙度以及相同基底粗糙度的K9玻璃完成二氧化钛(TiO₂)光学薄膜的沉积。采用TalySurf CCI非接触式表面轮廓仪分别对镀制前基底表面粗糙度和镀制后薄膜表面粗糙度进行测量。实验表明, TiO₂薄膜表面粗糙度随着基底表面的增大而增大, 但始终小于基底表面粗糙度, 说明TiO₂薄膜具有平滑基地表面粗糙的作用; 随着沉积速率的增大, 薄膜表面粗糙度先降低后趋于平缓; 对于粗糙度为2 nm的基底, 离子束能量大小的改变影响不大, 薄膜表面粗糙度均在1.5 nm左右; 随着膜层厚度的增大, 薄膜表面粗糙度先下降后升高。     

二氧化锆薄膜表面粗糙度的研究

采用电子束蒸发工艺,利用泰勒霍普森相关相干表面轮廓粗糙度仪,研究了不同基底粗糙度、不同二氧化锆薄膜厚度以及不同的离子束辅助能量下所沉积的二氧化锆薄膜的表面粗糙度。结果表明：随着基底表面粗糙度的增加,二氧化锆薄膜表面粗糙度呈现出先缓慢增加,当基底的粗糙度大于10nm后呈现快速增加的趋势;随着二氧化锆薄膜厚度的增加,其表面均方根粗糙度（RMS）先减小后增大;随着辅助沉积离子能量的增加,其表面粗糙度呈现出先减小后增加的趋势。     

Flame acceleration process and detonation transition in a channel with roughness elements on a wall

We experimentally investigated the effect of small roughness elements, which could be regarded as the wall roughness, on flame acceleration and deflagration-to-detonation transition (DDT). Our previous experiments (Maeda et al., 2019) using the sandpaper-like irregular roughness indicated that the flame acceleration and the associated DDT were greatly enhanced by the roughness. In this study, CH* chemiluminescence imaging as well as schlieren imaging was conducted in parallel with pressure measurements using an ethylene-oxygen combustion in the channel (486 mm long, 10 mm square cross-section) with the regular roughness (square pyramid elements with a base length and a height of 1 mm) in order to directly link the interference between the flow-field affected by the roughness and the propagating flame surface resulting the enhancement of chemical reactions, whereas the schlieren imaging alone could not allow to discuss the chemical reaction field in the previous study. After the leading shock wave was formed by the initial finger flame acceleration process, multiple interactions were observed on the flame front with the flow-field and pressure disturbances of the unreacted gas near the roughness elements. The results provided clear evidence that the roughness emphasized the effect of boundary layer, and the region where the disturbance layer and the flame were interacting coincided with the strong chemical reaction in the chemiluminescence image, indicating increase of the flame surface area caused by the turbulence on the flame front, which was also validated by the rough estimation of the burning velocity. The detonation onset was observed at the flame surface near the wall with the roughness elements. The possible factors of the final detonation transition were deduced to be the hot spot formation based on the multiple interactions of pressure waves with the roughness elements and entrainment of the unreacted gas of the highly turbulent flame front.     

Application of an acoustic backscatter technique for characterizing the roughness of porous soil

An acoustic backscatter technique proposed by Oelze et al. [J. Acoust. Soc. Am. 109, 1826-1832 (2001)] was used to characterize the roughness of porous soil surfaces. Roughness estimation errors are minimized when the effective flow resistivity of the porous soil is high, e.g., above 300,000 mks Rayls/m. Four soil plots were constructed by roughening soil with farming implements. Three plots were sealed using Saran powder dissolved in methyl ethyl ketone (MEK) and then covered to prevent further weathering. A fourth plot was left in the open and exposed to rainfall, which also acted to seal the surface and further change the roughness. In sealing the surface the effective flow resistivity of the surface was increased above 300,000 mks Rayls/m, which is typical for weathered agricultural surfaces. The roughness power spectra of the soil surfaces were measured by acoustic backscatter and alternatively by a laser profiler. Regression analysis was used to approximate each roughness power spectrum versus roughness wave number with a best-fit line. The best-fit line was used to calculate the rms height and the correlation length of the rough surface by integrating the approximate roughness power spectrum over a range of roughness wave number values. The range of roughness wave number values defines the roughness length scales used in the statistical calculations. High-roughness wave numbers correspond to smaller length scales of roughness and low-roughness wave numbers correspond to larger length scales of roughness. Over certain ranges of roughness wave number values the statistics from the acoustic backscatter and laser profiler measurements is in good agreement. However, as the low-cutoff roughness wave number is decreased and the high-cutoff roughness wave number is increased, agreement between the laser and acoustic techniques diminishes.     

Fractal analysis and atomic force microscopy measurements of surface roughness for Hastelloy C276 substrates and amorphous alumina buffer layers in coated conductors

In coated conductors, surface roughness of metallic substrates and buffer layers could significantly affect the texture of subsequently deposited buffer layers and the critical current density of superconductor layer. Atomic force microscopy (AFM) is usually utilized to measure surface roughness. However, the roughness values are actually relevant to scan scale. Fractal geometry could be exerted to analyze the scaling performance of surface roughness. In this study, four samples were prepared, which were electro polished Hastelloy C276 substrate, mechanically polished Hastelloy C276 substrate and the amorphous alumina buffer layers deposited on both the substrates by ion beam deposition. The surface roughness, described by root mean squared (RMS) and arithmetic average (R_a) values, was analyzed considering the scan scale of AFM measurements. The surfaces of amorphous alumina layers were found to be fractal in nature because of the scaling performance of roughness, while the surfaces of Hastelloy substrates were not. The flatten modification of AFM images was discussed. And the calculation of surface roughness in smaller parts divided from the whole AFM images was studied, compared with the results of actual AFM measurements of the same scan scales.     

表面粗糙度对激光诱导击穿光谱信号的影响

硅橡胶复合绝缘子是高压输电线路的关键设备,长期在复杂外界环境条件下带电运行后会发生表面老化,表现为粉化、褪色、粗糙度和硬度上升等现象。粗糙度作为复合绝缘子的老化特征量之一,其测量是复合绝缘子在线带电检测的难题。激光诱导击穿光谱技术(laser-induced breakdown spectroscopy, LIBS)适用于开展输电线路复合材料的远程在线检测,但粗糙度对LIBS信号的影响还没有得到系统的研究,利用这种基体效应进行绝缘子表面粗糙度的测量尚无报道。制备了不同粗糙度的硅橡胶新样品,与500 kV线路退运的复合绝缘子样品进行对比分析,研究了硅橡胶材料的粗糙度对LIBS信号的影响,结果表明,对于新制备硅橡胶材料随着粗糙度的增加,各主体元素特征谱线强度会随之增强,不同主体元素之间的原子谱线强度比（Si 288.2 nm/C 247.9 nm和Al 394.4 nm/Si 288.2 nm）随之下降,说明样品粗糙度对LIBS测量结果影响显著。但特征谱线强度及不同主体元素原子谱线强度比与粗糙度之间的函数关系不明显,难以用于粗糙度测量。硅橡胶的主体元素为Si,Al,C和O等,考虑元素含量及特征谱线的选取方便选择Si为主要分析元素。对于Si原子谱线强度比,选取了两条上能级相近（E_ki＝40 991.88, 39 955.05 cm-1）的原子谱线（SiⅠ288.2 nm,SiⅠ250.7 nm）作为分析线,在满足局部热力学平衡与光学薄的条件下两条谱线的强度比应为定值,但样品粗糙度的改变会影响脉冲激光烧蚀材料表面的过程,从而改变等离子体的状态,使得谱线强度比值也随之变化。上述两条硅原子谱线强度比和粗糙度建立的定标关系,线性相关系数为0.88。对于500 kV输电线路退运的老化硅橡胶材料,其表面由于老化有部分氢氧化铝填料析出,使得基体成分不均匀性更为显著,其表面也变得更为粗糙,这导致一对谱线强度比值作为定标函数,实用性降低。因此针对老化硅橡胶材料,除了选择Si元素谱线(SiⅠ250.7 nm,SiⅠ251.4 nm,SiⅠ251.9 nm)以外,还引入了Al元素谱线(AlⅠ305.7 nm, AlⅠ305.9 nm),利用三组谱线强度比进行多元回归分析,对于两个实测粗糙度为2.659和2.523 μm老化硅橡胶样品,LIBS测量的相对误差分别为0.218和0.189。结果表明对同样成分的复合材料,表面粗糙度对LIBS信号的影响是必须考虑的,而利用这种基体效应,开展远程在线测试复合绝缘子表面粗糙度,对于高压输电线路检测运维具有重要的应用价值。     

应用碳化硅表面改性技术降低全息-离子束刻蚀光栅刻槽的粗糙度

采用具有良好比刚度和热稳定性的碳化硅材料作为基底,使用全息-离子束刻蚀技术制作了光栅。碳化硅材料表面固有缺陷导致制作的光栅刻槽表面粗糙度高,槽底和槽顶粗糙度分别达到了29.6 nm和65.3 nm (R_q)。通过等离子辅助沉积技术在碳化硅表面镀制一层均匀的硅改性层,经过抛光可以获得无缺陷的超光滑表面。XRD测试表明制备的硅改性层为无定形结构。原子力显微镜的测试结果表明:经过抛光后,表面粗糙度为0.64 nm(R_q)。在此表面上制作的光栅刻槽表面粗糙度明显降低,槽底和槽顶粗糙度分别为2.96 nm和7.21 nm,相当于改性前的1/10和1/9。     

Properties of the roughness in NiFe/FeMn exchange-biased system

X-ray reflectivity and atomic force microscopy analyses were performed in the Si/WTi (7 nm)/NiFe (5 nm)/FeMn (13 nm)/WTi (7 nm) exchange-biased system prepared by magnetron sputtering. Layer-by-layer analyses were done in order to have interfacial roughness parameters quantitatively. X-ray reflectivity results indicate that the successive layer deposition gives rise to a cumulative roughness. In addition, the atomic force microscopic images analyses have revealed that the roughness enhancement caused by the successive layer deposition can be associated with an appearance of a longer wavelength roughness induced by the NiFe layer deposition.     

Effect of annealing on the surface and band gap alignment of CdZnS thin films

Effects of the annealing temperature on structural, optical and surface properties of chemically deposited cadmium zinc sulfide (CdZnS) films were investigated. X-ray diffraction (XRD) results showed that the grown CdZnS thin films formed were polycrystalline with hexagonal structure. Atomic force microscopy (AFM) studies showed that the surface roughness of the CdZnS thin films was about 60-400 nm. Grain sizes of the CdZnS thin films varied between 70 and 300 nm as a function of annealing temperature. The root mean square surface roughness of the selected area, particular point, average roughness profile, topographical area of roughness were measured using the reported AFM software. The band gaps of CdZnS thin films were determined from absorbance measurements in the visible range as 300 nm and 1100 nm, respectively, using Tauc theory.     

一种光学探测海底粗糙度的算法及其实验研究

海底微地形粗糙度作为海底沉积物重要的物理性质, 对于海洋工程以及海洋科学考察都有着重要意义, 如何利用光学理论进行海底微地形粗糙度测量, 是近年来该领域研究关注的热点。基于光学中的从明暗恢复形状(shame from shading, SFS)算法, 提出一种快速的海底微地形粗糙度测量算法, 在模型构建同时, 添加水下光传播时的吸收和衰减模型, 测量出海底的微地形, 并用幂律形式进行参数拟合, 以表征粗糙度。仿真证明该算法具有95%的置信度, 是一种适用于海底微地形粗糙度测量的光学算法, 并经过实验验证, 证明其有效性和正确性。     

Influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings

The present study has been conducted in order to determine the influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Six types of coating samples with different substrate roughness were tested. The surface roughness and real surface area of both the substrates and coatings were studied by atomic force microscopy (AFM) techniques. The scratch tests performed at progressive loads were employed to evaluate the adhesion of the coatings. Cyclic oxidation tests were performed at 1100 °C in air for 50 cycles, each cycle consisting of 1 h heating in the tube furnace followed by 15 min cooling in the open air. The AFM measurements exhibit that the surface roughness of the sputtered NiCoCrAlY coating increases with the increasing of the superalloy substrate roughness. The NiCoCrAlY coatings present slightly lower roughness than the corresponding superalloy substrate. The scratch adhesion tests indicate that the coatings on substrates with a smoother surface possess better adhesion than on those with a rougher surface. Both the real surface area and oxidation weight gain of the coatings decrease with the decreasing of the superalloy substrate roughness. The NiCoCrAlY coating sputtered on the superalloy substrate with lower roughness provides relatively higher antioxidant protection than that provided by the coating with rougher substrate.     

Effect of Interface Roughness on Perpendicular Magnetic Anisotropy of Fe/Tb Multilayers

Fe/Tb multilayers have been prepared which exhibit significant perpendicular magnetic anisotropy (PMA) even at RT. The effect of systematic variation in the interface roughness on PMA has been studied in these multilayers which were deposited simultaneously on a set of float glass substrates prepared with varying root mean square surface roughness. The amount of intermixing at the interfaces and uncorrelated part of the interface roughness of different multilayers remain similar, thus allowing one to separate out the effect of the correlated interface roughness only. X-ray reflectivity and conversion electron Mössbauer spectroscopy and SQUID magnetometry was used to characterise the systems. PMA was found to depend weakly on the correlated interface roughness.     

Evaluation of nanoscale roughness measurements on a plasma treated SU-8 polymer surface by atomic force microscopy

A comparison between roughness data obtained with an atomic force microscope (AFM) on different surfaces requires reliable roughness parameters. In order to specify the appropriate parameters for nanoscale roughness measurements, we compared the root mean square (rms) roughness and the relative surface area (sdr) as function of varying scan size, speed and pixel size. By using oxygen plasma (24 kJ) treated SU-8 with an average rms roughness of 2.6 ± 0.5 nm as reference surface, the repeatability of the method was evaluated for dynamic (tapping) and contact mode. The evaluation of AFM images indicated a decrease of the effective tip radius after a few measurements. This degradation of the tip lowers the resolution of the image and can affect roughness measurements.     

Effect of surface roughness on leakage current and corrosion resistance of oxide layer on AZ91 Mg alloy prepared by plasma electrolytic oxidation

The influence of the surface roughness of Mg alloys on the electrical properties and corrosion resistance of oxide layers obtained by plasma electrolytic oxidation (PEO) were studied. The leakage current in the insulating oxide layer was enhanced by increasing the surface roughness, which is a favorable characteristic for the material when applied to hand-held electronic devices. The variation of corrosion resistance with surface roughness was also investigated. The corrosion resistance was degraded by the increasing surface roughness, which was confirmed with DC polarization and impedance spectroscopy. Pitting corrosion on the passive oxide layer was also analyzed with a salt spray test, which showed that the number of pits was not affected by the surface roughness when the spray time reached 96 h.     

Roughness evolution of highly ordered nanoporous anodic aluminum oxide films

In this paper, we report on the surface roughness evolution of highly ordered anodic aluminum oxide (AAO) films based on an atomic force microscopy (AFM) study. Root mean square of the surface roughness was measured on AFM images taken from highly ordered AAO films produced by two-step anodization under different conditions including electrolyte type, anodization voltage, and anodization time. Surface roughness of highly ordered AAO films increases step by step through the two-step anodizing process including electropolishing, first-step anodization, dissolution, and second-step anodization. However, increase of the surface roughness is proportional to the anodization voltage and time. The surface roughness of AAO films changes as a function of length scale until it finally approaches a maximum termed the saturation roughness. The variation of roughness of the growth of AAO could be scaled with an anomalous dynamic behavior as it saturates over a critical length scale while the saturation roughness is dependent on the anodizing time and voltage.     

Roughness of pigment coatings and its influence on gloss

A robust method is used for analyzing roughness at a wide range of lateral length scales. The method is based on two-point correlation where both the amplitude and lateral spacing of surface heights are considered when determining the roughness. Atomic force microcopy and confocal optical microscopy images were captured for a set of pigment-coated samples. The effects of sampling interval, image size and filtering on surface roughness were studied. Isotropy and periodicity of roughness were determined by analyzing the angular distribution of the correlation length (T) and the autocorrelation function (ACF). A clear dependence of root mean square (RMS) roughness (σ) on T was established for randomly distributed surfaces. By taking into account the σ-T dependence it was possible to obtain σ for various length scales for each sample and thus attaining the most relevant σ for a certain surface function, which in this study was specular reflection of light (gloss). The roughness analysis showed that a small amount of DPP coating was sufficient to completely cover and change the surface of the substrate, while kaolin coatings gave a different response.     

磁控溅射制备Ni/Ti多层膜表面粗糙度

采用磁控溅射方法制备了周期数分别为10,30,50和75的Ni/Ti多层膜,利用X射线掠入射反射测量了多层膜表面和界面的状态,并用原子力显微镜测量了多层膜的表面粗糙度,研究了不同周期数的Ni/Ti多层膜表面粗糙度的变化规律。结果表明:Ni/Ti多层膜表面粗糙度随着膜层数增加而增加,当Ni/Ti多层膜的周期数从10变化到75时,其表面粗糙度由0.80 nm增大到1.69 nm。实验数据拟合表明:Ni/Ti多层膜表面粗糙度与周期数成3次方关系;但在周期数较小时,粗糙度与周期数成线性关系。