Optimization of sputtered Cr/Au thin film for diaphragm-based MEMS applications

An optimization study on the sputtering of Cr/Au thin film for diaphragm-based MEMS applications is presented. The effects of the film thickness, process pressure and process power on the residual stress of the film are investigated. A low-stress silicon nitride diaphragm-based device characterization platform is fabricated to study the influence of the Cr/Au film stress on the diaphragm compliance. The fabricated devices are characterized by measuring the capacitance change under a bias voltage from 0 to 40 V. For the 8-µm and 10-µm air gap device characterization platforms, the largest capacitance changes of 5.1% and 4.3%, respectively, occur at a compressive film stress of − 200 MPa. A large capacitance change indicates a more sensitive diaphragm, which is desired in pressure sensor design.     

Corrosion behaviour of CrN/Cr multilayers on stainless steel deposited by unbalanced magnetron sputtering

This paper reports the results of the influence of bilayer period (Λ) and total thickness (f) on the corrosion resistance of magnetron-sputtered CrN/Cr multilayers. Corrosion tests were carried out by potentiodynamic polarization with 0.5 M H₂SO₄ + 0.05 M KSCN solution and electrochemical impedance spectroscopy (EIS) with 3% NaCl solution. Measurements were also taken on the uncoated substrate and hard chromium coatings for comparison. Multilayer microstructure and morphology were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) and chemical composition was studied by energy dispersive X-ray analysis (EDX).The experiments showed that CrN/Cr coatings having lower bilayer period and lower thickness increased their efficiency as a barrier and improved the corrosion resistance of all coatings evaluated.     

Cr/Cr2O3多层膜的研究

用真空蒸镀及自然氧化方法在玻璃基底上制备纳米量级的4、5、6、7对层的Cr／Cr2O3多层膜。采用称重法测定薄膜的厚度；在常温和低温下使用三点法测定多层膜的电特性；用扫描电镜（SEM）观察薄膜的表面和截面的形貌及成分；用X射线衍射仪检测相结构。结果表明：制备的是纳米量级非晶态的Cr／Cr2O3多层膜，在常温和低温（77K）下均具有类似负阻的特性。     

Microstructure and mechanical properties of nanostructure multilayer CrN/Cr coatings on titanium alloy

Five different nanostructured, multilayer coatings (CrN/Cr)x8 with different thickness ratio of Cr and CrN layers were deposited by PAPVD (Plasma Assisted Physical Vapour Deposition) vacuum arc method on Ti6Al4V titanium alloy. The microstructure, chemical and phase composition of the CrN and Cr sub-layers were characterized by SEM with EDX and Cs-corrected dedicated STEM on cross-sections prepared by focus ion beam. Besides, hardness and Young's modulus of the (Cr/CrN)x8 coatings has been measured. The adhesion has been tested by scratch test method. The obtained (CrN/Cr) multilayer coatings, 5-6 μm in thickness, have homogeneous and nanocrystalline structure, free of pores and cracks. The microstructures of Cr and CrN layers consist of columnar grains below 100 nm in diameter. The hardness and Young's modulus of these coatings depend linearly on thickness ratio of Cr and CrN layers. The decrease of the thickness ratio Cr/CrN 0.81 to 0.15 results in the increase of hardness from 1275 HV to 1710 HV and Young's modulus from 260 GPa to 271 GPa.     

Auger electron spectroscopy analysis of interface roughness of Fe/Cr bilayers

In this work we investigate the surface and interfacial properties of Fe/Cr and Cr/Fe bilayers before and after annealing using Auger electron spectroscopy (AES). The roughness of the interface is also determined with the X-ray reflection method. The fitted values of inelastic mean free path λ_{Cr in Fe} reproduce the calculated value for Cr in Fe well, whereas the values of λ_{Fe in Cr} are significantly larger than the calculated ones, suggesting mutual segregation of atoms during growth. The low-energy range Auger spectra demonstrated that the MNN lines of Cr covered with Fe and Fe covered with Cr disappear after the deposition of 1 nm overlayer, this being an indication of continuous deposited film, but not excluding mixing at interfaces. The results of X-ray reflectometry measurements, which give the values of Fe/Cr and Cr/Fe roughness, are in accordance with this observation. The LMM Auger spectra of annealed samples showed that at the largest applied temperature, Cr diffuses into Fe, but the reverse effect of Fe diffusion into Cr is not observed.     

Microstructure and shear strength of Mo-Cu/Cr18-Ni8 brazing joint in vacuum

High density Mo-Cu composite and Cr18-Ni8 stainless steel were brazed with Ag-Cu filler metal in vacuum of 10⁻⁵ Pa. The microstructure characteristics of Mo-Cu/Cr18-Ni8 brazed joint were investigated by field-emission scanning electron microscope (FESEM) with energy dispersive spectrometer (EDS) and shear strength was measured by shearing test. The results indicated that a Mo-Cu/Cr18-Ni8 joint with shear strength of 125 MPa was obtained at 940 °C for 20 min. There were Ag-Cu eutectic and Cu-rich phase without brittle intermetallic compounds formed in the joint. The shear fracture exhibited plastic feature with shear dimple and fracture located at the interface between braze seam and Cr18-Ni8 stainless steel.     

Structural design of Cr/GLC films for high tribological performance in artificial seawater: Cr/GLC ratio and multilayer structure

In this paper,graphite-like carbon(GLC)films with Cr buffer layer were fabricated by DC magnetron sputtering technique with the thickness ratio of Cr to GLC films varying from 1:2 to 1:20.The effect of Cr/GLC modulation ratio on microstructure,mechanical and tribological properties in artificial seawater was mainly investigated by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),nano-indenter and a reciprocating sliding tribo-meter.The propagation of defects plays an important role in the evolution of delamination,which is critical to wear failure of GLC films in artificial seawater.Designing the proper multilayer structure could inhibit the defects propagation and thus protect the basis material.The multilayer Cr/GLC film with optimized ratio of 1:3 demonstrates a low average friction coefficient of 0.08±0.006 and wear rate of(2.3±0.3)×10~(-8)mm~3/(N m)in artificial seawater,respectively.     

新型工艺制备Fe/Cr/Si复合薄膜的结构研究

采用改进的水热法和新型工艺在SUS304不锈钢表面制备了Fe/Cr掺杂SiO2薄膜,并通过扫描电镜(SEM)、X射线衍射(XRD)、电子探针(EPMA)和X射线光电子能谱深度分析(XPS)等检测手段对薄膜结构进行了分析.结果表明膜层主要分为两层:表层为共溶氧化物层;底层为Cr、Fe的氧化物,主要为尖晶石结构和Si网状结构.通过XPS检测结果得知,Si元素的加入不是简单的物理混合,而是与金属元素生成了Si-Fe键,进一步提高了膜层的结合力和耐酸性.     

The effect of Cr barrier on interfacial reaction of Au/Zn/Au/Cr/Au contacts to p-type InGaAs/InP

Alloy-type metal is widely used to reduce contact resistance in optoelectronic devices. Among the alloy-types, Au/Zn is one of the most common metallization systems. In this paper, we studied the alloy morphology of p-InP/p-InGaAs/Au/Zn/Au/Cr/Au systems. We found that the amount of Au-Zn alloy depended upon the thickness of the Cr layer. When Cr thickness was reduced to 135 Å, both Au-rich and GaAs-rich excessive compound formation started to occur. The Au diffusion punched through the InGaAs layer and penetrated into the InP. Comparison of Au/Zn/Au and Au/Zn/Au/Cr/Au suggested that the top Au layer maybe very influential during the alloy reaction. The Au-Zn alloy was significantly less in the Au/Zn/Au than that in the Au/Zn/Au/Cr/Au.     

Effects of ion-assisted growth on the layer definition in Cr/Sc multilayers

Nano-structural evolution of layer morphology and interfacial roughness in Cr/Sc metal multilayers grown with ion assistance during magnetron sputter deposition has been investigated by high resolution transmission electron microscopy and hard X-ray reflectivity. Calculations based on a binary collision model predict an ion-assisted growth window for optimized Cr/Sc multilayer interface sharpness, within the ion energy range of 21 eV to 37 eV and an ion flux of ∼ 10 ions per deposited atom. Multilayers with nominal modulation periods in the range of 1.6 nm to 10.2 nm, grown with these conditions, exhibit a well-defined layer structure with an improved flattening and abruptness of the interfaces. It is shown that multilayers with a modulation period smaller than 3.4 nm have clear benefit from the reduced intermixing obtained by utilizing a two-stage ion energy modulation for each individual layer. The amorphization of Sc and Cr layers, below certain thicknesses, is found to be independent of the low energy ion-assistance. It is also shown that the Cr/Sc multilayers, containing periods less than ∼ 2 nm are ‘self healing’ i.e. they re-gain abrupt interfaces and flat layers after morphological disturbances during ion assisted growth. In comparison, multilayers grown without ion-assistance exhibited severe roughness and layer distortions.     

磁控溅射C靶电流对Cr/C和Cr/C/N复合镀层组织和性能的影响

利用控溅射技术,通过改变溅射C靶电流工艺参数,在45#钢上制备出Cr/C和Cr/C/N复合镀层.用能谱仪(EDS),X射线衍射仪(XRD)、扫描电子显微镜(SEM)检测镀层的微观组织;用HX-1000型维氏显微硬度计、球-盘摩擦磨损试验机(POD)、光学显微镜(OM)测试镀层的力学性能.结果表明:随C靶电流增加,镀层微...     

Corrosion resistance of multilayer coatings of nanolayered Cr/Ni electrodeposited from Cr(III)-Ni(II) bath

In this study the corrosion resistance of chromium and nickel single layers and multilayer coatings of nanolayered Cr/Ni, electrodeposited from Cr(III)-Ni(II) baths on low carbon steel substrates, has been studied. The coatings were electrodeposited from a bath using pulse current and modulated agitation. The total thickness of single layer and multilayer coatings was fixed at 5 μm and multilayer coatings with different modulation wavelengths and Cr to Ni thickness ratio were electrodeposited. Corrosion behavior of coatings was then studied by using potentiodynamic polarization test and electrochemical impedance spectroscopy in 0.1 M H₂SO₄. The results showed that Cr and Ni single layers had low corrosion resistance due to the presence of surface cracks and pores, respectively. On the other hand, optimized 20 nm Cr/50 nm Ni multilayer deposition significantly improved corrosion resistance.     

Effect of layer thickness on thermal properties of multilayer thin films produced by PVD

Cr/CrN/CrAlN, CrN/CrAlN and Cr/CrN thin layers were deposited by PVD (Physical Vapor Deposition). The multilayers were obtained from the combined deposition of different layers Cr, CrN and CrAlN thick films on on AISI4140 steel and silicon substrates at 200 °C, and evaluated with respect to fundamental properties such as structure and thermal properties. Cr, CrN and CrAlN single layers were also prepared for comparison purposes. The structural and morphological properties of PVD layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS + WDS microanalyses, stresses were determined by the Newton’s rings methods using the Stoney’s equation and surface hardening and hardness profiles were evaluated by micro hardness measurements. The XRD data and HRTEM showed that both the Cr/CrN, CrN/CrAlN and Cr/CrN/CrAlN multilayer coatings exhibited B1NaCl structure with a prominent reflection along (200) plane, and CrAlN sub-layer microstructures composed of nanocrystallites uniformly embedded in an amorphous matrix. The innovation of this work was to use the thickness of three different coating types to determine the thermal properties. Furthermore, an empirical equation was developed for the thermal properties variations with temperature of AISI4140 steel coated with different multilayer coatings. The thermal conductivity of CrAlN single layered was lower than the multilayer and the bulk material AISI4140. Moreover, the influences of structure and composition of the multilayer coatings on the thermal properties are discussed.The thermal conductivity of nanoscale thin film is remarkably lower than that of bulk materials because of its various size effects.     

Cr/Cu/Ag/Cu/Cr新型银基复合薄膜电极的防氧化性能研究

采用直流磁控溅射技术和光刻工艺制备了Cr/Cu/Ag/Cu/Cr复合薄膜及其电极,研究不同温度热处理对复合薄膜和电极结构、表面形貌和电性能的影响。Ag层与最外层的Cr层之间的Cu层不仅增强了Cr和Ag之间的粘附力,而且起到了牺牲层和氧气阻挡层的作用;Cr和Cu对Ag的双重保护使得薄膜电极在温度小于500℃时电阻率保持较为稳定,约为3.0×10-8~4.2×10-8Ω·m之间。然而由于电极表面氧化和边沿氧化的共同作用,薄膜电极的电阻率在热处理温度超过575℃出现了显著的上升。尽管如此,Cr/Cu/Ag/Cu/Cr薄膜电极仍然是一种能够承受高温热处理并且保持较低电阻率的新型电极,满足场发射平板显示器封接过程中的热处理要求。     

Electrophysical properties of Cu/Cr and Fe/Cr film systems within elastic and plastic deformation range

We have investigated the electrophysical properties of metallic thin films based on Cu/Cr and Fe/Cr systems. We find that the longitudinal gauge factor of two-layer films is significantly greater as compared with one-layer films, which have the same thickness as the total thickness of a two-layer film. Interface and intensive grain–boundary electron scattering explain such an increase in the longitudinal gauge factor. We find that the longitudinal gauge factor increases in transition from elastic to plastic zone.     

Formation and mechanism of nanoscale zerovalent iron supported by phosphoric acid modified biochar for highly efficient removal of Cr(VI)

The effect of phosphoric acid modified biochar on activity of nanoscale zero valent iron particles is not clear until now. In this research, Egeria najas powder driven biochar-supported nanoscale zero valent iron was modified by phosphoric acid (P-BC/nZVI) for highly effective removal of Cr(VI) from wastewater. The TEM and XRD of P-BC/nZVI indicated that nZVI particles were successfully immobilized on the P-BC surface. The batch experiment results show that the Cr(VI) removal efficiency by P-BC/nZVI was higher than that of BC/nZVI, nZVI, P-BC and BC. Moreover, the optimal ratio of nZVI to P-BC lies at 3:1 with fixed P-BC/nZVI dosage of 0.75 g/L, initial Cr(VI) concentration of 20 mg/L, solution pH of 2, and reaction temperature of 333 K. Additionally, Cr(VI) removal capacities by nZVI, BC/nZVI and P-BC/nZVI aged for 15 days in water were 12.9 %, 28.55 % and 99.35 %, respectively. Furthermore, corresponding reaction kinetics fitted well with pseudo-second order model, and adsorption isotherm fitted to Sips isothermal model. The SEM-EDS and XPS confirm that Cr(VI) was participated in the reaction, and about 63.43 % of Cr(VI) was reduced to Cr(III), and the rest was adsorbed on the surface of P-BC/nZVI. The removal mechanism of Cr(VI) by P-BC/nZVI was complex, including adsorption, reduction and surface complex formation.     

锌漆薄膜/2Cr13钢基体系统薄膜裂纹试验与模拟

本文采用试验和数值模拟方法研究锌漆薄膜/2Cr13钢基体系统薄膜开裂和裂纹扩展情况。创新性地使用三点弯曲试验结合声发射技术监测到薄膜裂纹萌生时刻,并计算薄膜断裂韧性。采用扩展有限元法研究三点弯曲作用下薄膜裂纹扩展过程,发现模拟得到的荷载-位移曲线与试验曲线相吻合。模拟结果表明,薄膜裂纹尖端区域存在应力峰值,当该值达到损伤判据临界应力时,裂纹发生扩展。同时,对多种因素影响下薄膜周期裂纹无量纲能量释放率进行分析,发现薄膜厚度一定时,薄膜相对于基体刚度越大,半无限基体上薄膜裂纹前缘达到稳定状态时对应的基体厚度与裂纹间距越大。      

Analysis of the diffusion processes in Al/Cr, Al/Fe and Cr/Fe multilayers using the MRI model

One of the methods for synthesis of intermetallic films consists of two steps: deposition of a multilayer film containing monometallic layers, and consequential annealing to induce a diffusion process and alloy formation. Though the diffusion coefficients are generally known for couples of common metals, they can considerably differ for films deposited by PVD due to their specific microstructure. Bimetallic multilayers Al/Cr, Al/Fe and Cr/Fe were analysed as the first step for formation of the complex metallic alloy Al₄(Cr,Fe). The films were deposited by triode sputtering with a total thickness of about 250 nm and consisted of 6 layers. Annealing was performed in vacuum at temperatures 240-650 °C.The depth distributions of elements in the films annealed at various temperatures were measured by Auger electron spectroscopy. Detailed analysis of the profile was conducted using the MRI model, which takes into account interface broadening of the measured profile due to three reasons: ion-induced atom mixing, roughness, and information depth of analysed electrons. Thus we reconstructed the true depth profile of the as-deposited samples and profiles of the annealed samples that allowed us to extract the diffusion coefficients.     

Microstructure and optical properties of chromium containing amorphous hydrogenated carbon thin films (a-C:H/Cr)

Chromium containing amorphous hydrogenated carbon thin films was deposited using a dc sputter deposition technique under various mixtures of methane and Ar. The microstructure, composition, and optical properties of the resulting films were investigated. We show that a-C:H/Cr thin films exhibiting absorptance in certain wavelengths are greater than 95% and the average absorptance was 86% in the 0.3 to 2.5 µm wavelength can be obtained by using appropriate methane/Ar ratios and deposition times.     

金刚石表面Cr金属化的界面扩散反应研究

利用直流磁控溅射法在金钢石颗粒表面沉积了厚度为１５０ｎｍ的金属Ｃｒ薄膜。ＳＥＭ研究表明在金刚石表面形成的Ｃｒ膜基本均匀,但有小的金属聚集体存在。俄歇深度剖析研究发现,在镀膜过程中Ｃｒ膜和金刚石基底间发生了显著的界面扩工用作用。相应的俄歇线形分析表明,沉积过程中在界面上发生化学反应形成了部分Ｃｒ２Ｃ３物种。溅射沉积功率对金刚石颗粒与金属Ｃｒ膜的界面反应有较大的影响,提高溅射功率可大大促进Ｃｒ元素的扩