Chromium Thin Films Research Articles

Experimental study of mechanical and tribological behavior of nitrogen ion-implanted chromium thin films

Pure chromium coatings can act as decorative or corrosion-resistant coating, but they present poor tribological properties. Even electroplated hard chrome coatings present some problems, as micro-cracks that reduce their corrosion protection and induce fatigue failure. In addition, Cr plating and its dangerous process with Cr VI baths has been banished in several countries. Physical or chemical post-coating treatments can be applied onto coatings in order to enhance their surface properties, as high temperature oxidation, chemical baths or ion implantation. Plasma immersion ion implantation process was carried on PVD chromium coatings as a post-coating treatment and nitrogen ions were implanted on the surface of deposited chromium thin films, by means of two different plasma sources for ion implantation. Both configurations for plasma sources led to the formation of nitride compounds on the surface of the films. The treated films presented low coefficient of friction, high hardness and better adhesion when compared to the untreated film.

Phase coexistence and pinning of charge density waves by interfaces in chromium

We study the temperature dependence of the charge density wave (CDW) in a chromium thin film using x-ray diffraction. We exploit the interference between the CDW satellite peaks and Laue oscillations to determine the amplitude, the phase, and the period of the CDW. We find discrete half-integer periods of CDW in the film and switching of the number of periods by one upon cooling/heating with a thermal hysteresis of 20 K. The transition between different CDW periods occurs over a temperature range of 30 K, slightly larger than the width of the thermal hysteresis. A comparison with simulations shows that the phase transition occurs as a variation of the volume fraction of two distinct phases with well-defined periodicities. The phase of the CDW is constant for all temperatures, and we attribute it to strong pinning of the CDW by the mismatch-induced strain at the film-substrate interface.

Ultrafast Spin Density Wave Transition in Chromium Governed by Thermalized Electron Gas.

The energy and momentum selectivity of time- and angle-resolved photoemission spectroscopy is exploited to address the ultrafast dynamics of the antiferromagnetic spin density wave (SDW) transition photoexcited in epitaxial thin films of chromium. We are able to quantitatively extract the evolution of the SDW order parameter Δ through the ultrafast phase transition and show that Δ is governed by the transient temperature of the thermalized electron gas, in a mean field description. The complete destruction of SDW order on a sub-100fs time scale is observed, much faster than for conventional charge density wave materials. Our results reveal that equilibrium concepts for phase transitions such as the order parameter may be utilized even in the strongly nonadiabatic regime of ultrafast photoexcitation.

Improved Bond Strength of Cyanoacrylate Adhesives Through Nanostructured Chromium Adhesion Layers.

The performance of many consumer products suffers due to weak and inconsistent bonds formed to low surface energy polymer materials, such as polyolefin-based high-density polyethylene (HDPE), with adhesives, such as cyanoacrylate. In this letter, we present an industrially relevant means of increasing bond shear strength and consistency through vacuum metallization of chromium thin films and nanorods, using HDPE as a prototype material and cyanoacrylate as a prototype adhesive. For the as received HDPE surfaces, unmodified bond shear strength is shown to be only 0.20 MPa with a standard deviation of 14 %. When Cr metallization layers are added onto the HDPE at thicknesses of 50 nm or less, nanorod-structured coatings outperform continuous films and have a maximum bond shear strength of 0.96 MPa with a standard deviation of 7 %. When the metallization layer is greater than 50 nm thick, continuous films demonstrate greater performance than nanorod coatings and have a maximum shear strength of 1.03 MPa with a standard deviation of 6 %. Further, when the combination of surface roughening with P400 grit sandpaper and metallization is used, 100-nm-thick nanorod coatings show a tenfold increase in shear strength over the baseline, reaching a maximum of 2.03 MPa with a standard deviation of only 3 %. The substantial increase in shear strength through metallization, and the combination of roughening with metallization, may have wide-reaching implications in consumer products which utilize low surface energy plastics.

Maintaining strength in supersaturated copper–chromium thin films annealed at 0.5 of the melting temperature of Cu

The thermal stability of evaporated copper–chromium alloy films was studied by correlating hardness trends from nanoindentation to nanostructural–compositional changes from transmission electron microscopy. In particular, the hardness evolution with ageing time at ambient and elevated temperatures of two compositions, dilute (Cu96Cr4) and chromium-rich (Cu67Cr33) solutions, was studied. Due to the negligible mutual miscibility of copper and chromium, the chosen solid solutions are trapped in metastable states as supersaturated solid solutions with face-centred cubic and body-centred cubic phases. Nano-mechanical probing of the nanostructural evolution as a function of temperature provided interesting insights into the phase separation of these systems.

Electrical Properties and Microstructure of Chromium Thin Films Produced by Glancing Angle Deposition

Electrical Properties and Microstructure of Chromium Thin Films Produced by Glancing Angle Deposition

Optical and structural properties of Cr and Ag thin films deposited on glass substrate

Most of the rotating or noting patterns are being developed by using silver plating through chemical coating. Silver layers deteriorate with the passage of time and become less reflective while undergo through cleaning process due to its softness and the results become unpredictable. In this paper an alternate method for development of above mentioned pattern has been demonstrated. Chromium (Cr) and Silver (Ag) thin films of 200nm and 160nm thick respectively have been realized using electron beam evaporation (PVD technique) on quartz substrate. Structural analysis has been carried out by XRD and SEM while optical transmission/reflection has been studied using spectrophotometer. XRD analysis shows that Ag coated thin films exhibit FCC structure while Cr coated thin films reveals a BCC structure. SEM analysis shows almost smooth and uniform surfaces in both cases. After passing through high and low temperature cycles it was found that the results of pattern structures developed by chromium coating were more reliable than obtained through silver platting process.

Critical angles in DC magnetron glad thin films

The objective of this study is to examine the sudden drop in properties of aluminum, titanium and chromium thin films prepared by the glancing angle deposition method. The thin films were deposited by DC magnetron sputtering under identical deposition conditions. A substrate-holder with seven different orientations with respect to the target normal was used. The thickness and the column tilt angles (β) of the thin films were determined by scanning electron microscopy. The residual stress of the thin films was evaluated using the wafer curvature technique and calculated by the Stoney's formula. The thickness variation and column tilt angle versus the orientation of the substrate indicated that the critical point is around 60° for all metallic materials and a critical angle of 60° is also found for the residual stress. Simulations of the particles transport are compared to the experimental data and moderate the critical angles analyses.

X-ray fluorescence determination of the surface density of thin chromium and iron films using reference samples of elements with close atomic numbers

In X-ray fluorescence determinations of the surface density of thin chromium and iron films, we studied the possibility of using an approach based on the application of reference samples of elements with close atomic numbers. It was shown that the proposed diagnostic approach ensures the determination of the surface density of films with rather high precision.

Laser thermochemical writing: pursuing the resolution

Laser thermochemical writing is a powerful technique for direct recording of planar structures performed by a local laser oxidation of thin metal films. It is commonly used for producing diffraction optical elements, and a main challenge in this field is a necessity of a resolution enhancement. The presented article provides a theoretical analysis and the discussion of physical–chemical and processing factors that should be taken into account to raise a resolution. It is shown for example that writing on a thin chromium film by multiple low-power laser beams simultaneously few times subsequently allows to provide a recording with high resolution (up to 4 lines per µm) and productivity.

Experimental investigation by atomic force microscopy on mechanical and tribological properties of thin films

Abstract For this paper, a two part approach was taken to develop a fundamental understanding of the surface properties of four different hard thin films. On one front, atomic force microscopy was used to quantitatively measure both the adhesion and friction forces between the tip and sample surfaces. On the other front, the indentation technique was used to determine the mechanical properties of these materials (Young's modulus and hardness). The main purpose of this study was to investigate different thin films deposited on silicon wafer substrate for improving the wear life and reducing the coefficient of friction. Nanomechanical and nanotribological characterization of thin films of chromium, nickel, platinum and titanium deposited on silicon were performed.

Method for Fabricating Multilevel Interconnection Structures Using Differential Delamination Energies between Metal and Silicon Oxide Thin Films

SUMMARYA method for fabricating multilevel interconnection structures using differential delamination energies (adhesion strength) between metal and silicon oxide thin films has been developed. When the selectivity of the delamination energies between the metal and the silicon oxide thin films sets on the wiring, the silicon oxide thin film can be released on the low delamination energy area and can be held on the high delamination energy area by using ultrasonic waves. The delamination energies are calculated by using a molecular dynamics simulation. The delamination energies between chromium, titanium, and nickel and silicon oxide thin films are larger than those of copper and gold thin films. Chromium, titanium, and nickel are applied as an adhesion layer with silicon oxide, and copper and gold are applied as a release layer from silicon oxide. The results are applied to the process for fabricating the multilevel interconnection structures, and the release and adhesive areas of silicon oxide thin film can be fabricated on the wiring by applying ultrasonic waves. With this method, the lower wiring and the contact areas of multilevel interconnection structures can be easily fabricated.

Packing density/surface morphology relationship in thin sputtered chromium films

Abstract Modifying and engineering the properties of materials can be achieved by coating them with thin films possessing specific characteristics. The final properties of the coating are determined by the deposition conditions and by the associated film's growth mode. To gain a better understanding and eventually control over the growth and properties of very thin films (thickness less than 50 nm), various chromium films were deposited by magnetron sputtering and their electrical and optical properties were measured. This paper presents the relationships between the stress, the material's surface morphology and the properties of such chromium thin films. We observed an increase in electrical conductivity and photopic reflection of the films with the increase of the deposition power. Our analyses further revealed that the surface morphology is directly responsible for the enhancement of these properties, as surfaces presenting the least air fraction ratio (smooth surface with large grains and a Gaussian roughness distribution) were the most conductive and most reflective. We also demonstrated that calculating the residual film stress is an incomplete way of assessing the structure of the film, as films having similar residual stress exhibited different properties. In conclusion, the surface morphology and its roughness distribution represent a convenient way to estimate the packing density of sputtered thin films.

凝縮熱伝達へ及ぼす金属表面の濡れ性の実験的検討

Dropwise condensation (DWC) has high heat transfer coefficient. However, It is difficult to maintain DWC for long time. In order to maintain DWC long enough, it is important to understand the effect of the surface condition. In the present paper, the wettability of the metal-sputtered surfaces was controlled by MEMS technology. The effect of several metal-sputtered surfaces, i.e., Cupper(Cu), Titanium(Ti), Silver(Ag), Chromium(Cr), and Lead(Pb) on the pattern of the condensation, i.e., DWC or FWC, was examined qualitatively. The surface condensation with sputtered thin Silver(Ag) and Lead(Pb) films were DWC. On the other hand, the surface condensation with sputtered thin Cupper(Cu), Titanium(Ti) and Chromium(Cr) films were FWC. For DWC, the surface adsorption force was lower than that of FWC.

Additive process for fabrication of phased optical diffraction elements

We describe a process for fabrication of optical diffraction elements based on localized thermochemical oxidation of a thin chromium film. Once the recording procedure has been completed, the unoxidized chromium is removed, thereby forming a microrelief consisting of transparent chromium oxide.

Dispersion of thin metal films on dielectric substrates under high-power ion-beam irradiation

The effect of high-power ion-beam irradiation on thin metal (Al, Cu, Cr) films of varying (0.08–1.9 µm) thickness deposited onto dielectric sodium silicate glass and glass-ceramic substrates is investigated. The strong effect of the ion current density and film thickness on the surface morphology under irradiation is found. The features of the dispersion of a chromium thin film having high adhesion to the dielectric substrate by a high-power ion beam are examined.

Chromium inhibition and size-selected Au nanocluster catalysis for the solution growth of low-density ZnO nanowires.

The wet chemical synthesis of nanostructures has many crucial advantages over high-temperature methods, including simplicity, low-cost, and deposition on almost arbitrary substrates. Nevertheless, the density-controlled solution growth of nanowires still remains a challenge, especially at the low densities (e.g. 1 to 10 nanowires/100 μm2) required, as an example, for intracellular analyses. Here, we demonstrate the solution-growth of ZnO nanowires using a thin chromium film as a nucleation inhibitor and Au size-selected nanoclusters (SSNCs) as catalytic particles for which the density and, in contrast with previous reports, size can be accurately controlled. Our results also provide evidence that the enhanced ZnO hetero-nucleation is dominated by Au SSNCs catalysis rather than by layer adaptation. The proposed approach only uses low temperatures (≤70 °C) and is therefore suitable for any substrate, including printed circuit boards (PCBs) and the plastic substrates which are routinely used for cell cultures. As a proof-of-concept we report the density-controlled synthesis of ZnO nanowires on flexible PCBs, thus opening the way to assembling compact intracellular-analysis systems, including nanowires, electronics, and microfluidics, on a single substrate.

Influence of Reactive Ion Etching on THz Transmission and Reflection Properties of NiCr Film Deposited on a Dielectric Substrate

Enhanced terahertz (THz) absorption of NiCr film deposited on a dielectric substrate has been proven by applying a reactive ion etching (RIE) treatment to the dielectric film. Nano – scale nickel – chromium (NiCr) thin films are deposited on RIE treated silicon dioxide (SiO 2 ) dielectric substrates to study the transmission and reflection characteristics. Experimental results suggest that both transmission and reflection of NiCr film are weakened by the RIE treatment. The most significant decrease of transmission is observed in 1 ~ 4 THz while that of reflection occurs in 1.7 ~ 2.5 THz band. The decrease of both transmission and reflection is more significant for NiCr film with higher thickness. The RIE treatment, which induces nano – scale surface structures and increases the effective surface area of NiCr film, enhances the absorption and weakens the transmission and reflection of THz radiation. DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6131

Electrical Characterization of Thin Cr/Indium-Tin Oxide Layer by RF Sputtering

To obtain a suitable ohmic contact with the lowest resistivity, chromium (Cr) thin films were deposited on transparent conductive oxide indium tin oxide (ITO) by RF sputtering method in argon atmosphere and its electrical properties were optimized. The deposition of Cr thin film has been performed for the layers with thickness of 150, 300, and 600 nm in constant Ar gas flow of 30 SCCM. Results show that the lowest contact resistivity belongs to the layer with 600 nm thickness. Furthermore Cr/ITO has been studied for different flows of Argon gas 10, 30, 50, and 70 SCCM during the deposition with constant thickness of 600 nm Cr thin films, which result gave us the lowest contact resistivity. Experimental results show that specific contact resistance decreases by reducing the flow of argon gas. Analyze of SEM has been performed on the samples. The SEM micrographs show Cr thin films have smaller grains in 10 SCCM argon gas flows, in comparison with other flows of argon gas. The best specific contact for Cr/ITO has been obtained 4.5 × 10−6 Ωm2 at flow of argon gas 10 SCCM with 600 nm thickness.

Extremely high-power CO2 laser beam correction.

This paper presents the results of high-power CO2 laser-aberration correction and jitter stabilization. A bimorph deformable mirror and two tip-tilt piezo correctors were used as executive elements. Two types of wavefront sensors, one Hartmann to measure higher-order aberrations (defocus, astigmatism etc.) based on an uncooled microbolometer long-wave infrared camera and the other a tip-tilt one based on the technology of obliquely sputtered, thin chromium films on Si substrates, were applied to measure wavefront aberrations. We discuss both positive and negative attributes of suggested wavefront sensors. The adaptive system is allowed to reduce aberrations of incoming laser radiation by seven times peak-to-valley and to stabilize the jitter of incoming beams up to 25 μrad at a speed of 100 Hz. The adaptive system frequency range for high-order aberration correction was 50 Hz.