Ion Sputter Etching Research Articles

Surface pre-treatments of Ti-Nb-Zr-Ta beta titanium alloy: The effect of chemical, electrochemical and ion sputter etching on morphology, residual stress, corrosion stability and the MG-63 cell response

Pre-treatment methods for titanium alloys are of great importance, both as regards the treatment of the surfaces of the implant and as regards the pre-deposition phase of the coating processes and the surface modifications. We have investigated the impact of chemical, electrochemical and ion sputter etching on the surface properties, the corrosion stability and the MG-63 cell response of Ti-35Nb-7Zr-5Ta alloy. In the initial state, the samples have a mechanically polished surface. The pre-treatments that were applied led to significant morphological changes in microscale and also in nanoscale. The wettability of the pre-treated surfaces varied from hydrophilicity to hydrophobicity. Changes in contact angle were controlled by surface chemistry rather than changes in morphology and roughness. Native oxides and suboxides of alloying elements with a predominant amount of Nb2O5 were found to provide high corrosion stability of Ti-35Nb-7Zr-5Ta alloy after mechanical polishing, after chemical etching and after electrochemical etching. Significantly reduced corrosion resistance in a physiological saline solution was observed for the ion sputtered surface. A decreasing trend in the cell spreading area correlated with increasing surface roughness and decreasing polarization resistance. There is discussion of the causes of the changes in surface properties and cell behaviour.

Formation of Fine Protrusions by Sputter Etching of Stainless Steels and Evaluation of Gripping Ability of Fiber Sheets

Argon ion sputter etching of AISI type 420 stainless steels was carried out at a power of 250 W for 14.4 ks to form cone-shaped protrusions with bottom diameters of 10–20 µm by using a radio-frequency magnetron sputter apparatus. The sputter etching was also applied to AISI type 316 stainless steel at 250 W for 10.8 ks, and fine column-shaped protrusions with diameters smaller than 500 nm were formed. In addition, plasma-nitriding was applied to the protrusions of type 420 steel using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50 W for 1.8 ks. The gripping ability of protrusions was measured by friction tests for three types of fiber sheets. For a cotton cloth, the friction coefficients of the as-sputter-etched and plasma-nitrided type 420 steel specimens were 1.3 and 1.7 at a nominal compressive stress of 0.8 kPa, and that of the as-sputter-etched type 316 steel specimen was 1.0. These are much larger than 0.8 and 0.5 of the specimens polished with #100 emery paper and buff-polished with alumina powders. Also for microfiber and polyester fiber sheets, the specimen with protrusions showed a higher gripping ability than those of the mechanically polished specimens. The reason for the large gripping ability of protrusion specimens is due to piercing of the protrusions between and into weaving yarns.

Influence of surface pre-treatment with mechanical polishing, chemical, electrochemical and ion sputter etching on the surface properties, corrosion resistance and MG-63 cell colonization of commercially pure titanium.

The impact of four pre-treatment techniques on the surface morphology and chemistry, residual stress, mechanical properties, corrosion resistance in a physiological saline solution and cell colonization of commercially pure titanium is examined in detail. Mechanical polishing, electrochemical etching, chemical etching in Kroll's reagent, and ion sputter etching with argon ions were applied. Surface morphologies reflect the nature of surface layer removal. Significant roughening of the surface and a characteristic microtopology become apparent as a result of the sensitivity of chemical and ion sputter etching to the grain orientation. The hardness in the near surface region was controlled by the amount of residual stress. Etching of the stressed surface layer led to a reduction in residual stress and surface hardness. A compact passivation layer composed of TiO, TiO2 and Ti2O3 native oxides imparted high corrosion resistance to the surface after mechanical polishing, chemical and electrochemical etching. The ion sputter etched surface showed substantially reduced corrosion resistance, where the corrosion process was controlled by electron transfer. The specific topology affected the adhesion of the cell to the surface rather than the cell area coverage. The cell area coverage increased with the corrosion stability of the surface.

Facile and precise fabrication of 10-nm nanostructures on soft and hard substrates

One of the major challenges in the field of nanotechnology is the facile and inexpensive fabrication of <10-nm nanostructures with a defect-free and precise pattern over a large area. Nanoimprint lithography (NIL) is a nanopatterning method that allows low-cost, fast production, and large-scale fabrication, but it needs improvement with regard to achieving a high resolution over a large area, processing on soft substrates, and nanomaterial patterning. Herein, it is demonstrated 10-nm patterning on soft and hard substrates via an advanced nanoimprint process. With a 100-nm master mold, both soft and hard molds with reduced pattern sizes (50, 20, 10, and 5 nm) are first fabricated using atomic layer deposition (ALD) of Al2O3. After surface functionalization of the mold, nanoscale patterns are imprinted on both hard (Si) and soft polyethylene terephthalate substrates, which result in structures with a pattern size of 10 nm. Using a hybrid supporting layer poly(methyl methacrylate) (PMMA)/poly(vinyl alcohol) (PVA) and ion sputter etching, a well-defined and clean sub-10 nm nanostructure is achieved for the nanomaterial on the substrate after lift-off and thermal annealing processes. Using this method, a graphene nanoribbon 10 nm wide is fabricated. Our approach is suitable for the fabrication of devices and structures with a 10-nm-scale pattern over a large area.

Plasma nitriding of cone-shaped protrusions formed by sputter etching of AISI 420 stainless steel and their application to impression punch to form micro-holes on polymer sheets

Argon ion sputter-etching was applied to disk specimens of AISI type 420 martensitic stainless steel using a radio-frequency magnetron sputter-apparatus, and sharp cone-shaped protrusions with vertex angle of about 40° and base diameters less than 35 μm were formed. In order to increase compressive strength of protrusion tips without loss of sharpness, plasma-nitriding was applied to the as-sputter-etched specimens using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50 W for 1.8 ks. When the plasma-nitrided (PN-) and as-sputter-etched (AS-) specimens were statically impressed on polyethylene (PE) and polyvinylchloride (PVC) sheets by increasing the nominal stress step by step from 0.624 to 12.5 MPa, the protrusion tips of PN-specimen did not show bending deformation even at 12.5 MPa whereas those of AS-specimen revealed bending already at 2.2 MPa. When the PN-protrusions were impressed statically on a polycarbonate (PC) sheet, a part of tall protrusion tips were flattened, but the shape of the holes on the sheet was not distorted. The maximum hole-diameter on the PVC sheet is smaller than that of the PE and PC sheets due to a larger viscoelastic recovery of the PVC sheet. When the PN-protrusions were impressed repeatedly on the PE and PVC sheets one thousand times with nominal impression stress of 0.078 MPa, the tips did not show bending and very dense micro-holes were formed. On the other hand, a large bending of the AS-protrusion tips occurred by the repeated impression on the PVC sheet. Thus, the PN-specimen can be applied to an impression punch to form fine and dense holes on polymer sheets.

ステンレス鋼のスパッタエッチングにより形成した多機能微細突起物の圧縮強度におよぼすプラズマ窒化の影響

Argon ion sputter-etching of SUS420J2 martensitic stainless steel and SUS316 austenitic stainless steel were carried out to form fine protrusions on the specimen surface by using a radio-frequency magnetron sputter-apparatus. Plasma-nitriding was applied to the protrusions by using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50 W for 1.8 ks. Micro-Vickers hardness tests on cone-shaped protrusions with diameter of about 20 μm formed on the SUS420J2 steel showed that the compressive strength of protrusion tip of the plasma-nitrided specimen is almost four times larger than that of the as-sputter-etched specimen. Nanoindentation tests on quasi-columnar protrusions with sizes smaller than 500 nm formed on the SUS316 steel showed not only much scatter of indentation force vs depth curves but also irregular changes of gradient of the curves. This means that an inhomogeneous contact of the indenter on the protrusions with different heights, sizes and spaces as well as a discontinuous deformation of protrusions occur with progress of indentation. Although the true compressive strength of one protrusion is not obtained directly by usual hardness tests, a measure of the deformation resistance of a group of protrusions can be obtained from the hardness that is extrapolated to zero indentation area on the indentation area vs hardness curve. The compressive resistance of the plasma-nitrided protrusions is almost six times as large as that of the as-sputter-etched ones.

Effect of plasma nitriding on the strength of fine protrusions formed by sputter etching of AISI type 420 stainless steel

Argon ion sputter-etching of AISI type 420 martensitic stainless steel was carried out to form conical protrusions with bottom diameter of 10–30μm on the specimen surface by using a radio-frequency magnetron sputter-apparatus. Plasma-nitriding was applied to the protrusions with various mixing rate of nitrogen and argon gas. The shape of the protrusions was examined by using a scanning electron microscope, and the nitrides formed on the protrusions were identified by means of an X-ray diffraction analysis. Micro-Vickers hardness tests and nano-scratch tests were used to evaluate the deformation resistance of the protrusions. By plasma-nitriding at a nitrogen pressure of 130Pa and a nitriding power of 50W, about 1.3 times larger indentation resistance than that of the as-sputter-etched protrusions was obtained after a long nitriding time of 14ks. When plasma-nitriding was carried out at a lower nitrogen pressure of 1.2Pa and a higher nitriding power of 200W for 7.2ks, indentation and scratch resistances of the protrusions largely increased to the values almost three times as large as those of the as-sputter-etched protrusions. However, the protrusions were brittle due to the formation of thick nitride layers and the sharpness of the protrusions was lost. Reduction of the nitriding power to 50W recovered the sharpness with small amount of surface nitride layer, but the indentation resistances were only 1.4 times larger values than those of the as-sputter-etched protrusions. On the other hand, plasma-nitriding using a mixture of nitrogen gas of 0.53Pa and argon gas of 0.67Pa at the power of 50W produced almost twice larger indentation and scratch resistances than those of the as-sputter-etched protrusions within a short nitriding time of 1.8ks, retaining the sharpness of protrusions without forming brittle nitrided layers.

OS1409-285 スパッタエッチングにより形成した多機能微細突起物の強度に及ぼすプラズマ窒化の影響

Argon ion sputter-etching of SUS420J2 martensitic stainless steel and SUS316 austenitic stainless steel were carried out to form fine protrusions on the specimen surface by using a radio-frequency magnetron sputter-apparatus. Plasma-nitriding was applied to the protrusions by using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50W for 1.8ks. Micro-Vickers hardness tests on the top of cone-shaped protrusions with diameter of about 20 μm of SUS420J2 steel showed that the plasma-nitriding produces more than three times larger compressive strength than that of the as-sputter-etched protrusions. Nano indentation tests on ridge-shaped protrusions with sizes smaller than 500 nm of SUS316 steel also showed that the compressive strength of the plasma-nitrided protrusion is about twice as large as that of the as-sputter-etched one.

マルテンサイト系ステンレス鋼のスパッタエッチングによる微細突起物の形成

Argon ion sputter etching was applied to three kinds of martensitic stainless steels (SUS410, SUS420J2 and SUS440C) and a ferritic stainless steel (SUS430) at a radio frequency power of 250 W for 0.6 ks to 21.6 ks. When the sputter etching time is 0.6 or 0.9 ks, the pillar-shaped protrusions with diameters smaller than 1 μm are formed on the surface of the SUS420J2 steel. With increasing sputter etching time, the cone-shaped protrusions are formed around the base of the pillars, and the size of the conical protrusions increases to more than 10 μm with further increase in the sputter etching time. When the sputter etching time is 21.6 ks, the size of the protrusion becomes more than 20 μm and the surface of the protrusions is heavily damaged. According to an EDX analysis, the Cr content of the surface of a cone is larger than that of the inside and the matrix surrounding the cone. Other steels show a similar protrusion formation process to the SUS420J2 steel, but the formation speed and the density of the cones are smaller for the SUS410 or SUS430 steels with smaller carbon content than the SUS420J2 steel, whereas they are a little larger for the SUS440C steel with larger carbon content. For the martensitic stainless steels, the quenching increases the hardness of protrusions, which is convenient for a traction roll and a transcription roll to imprint many holes to sheets.

Superhydrophobicity produced by vapor deposition of a hydrophobic layer onto fine protrusions formed by sputter-etching of steels

Argon ion sputter-etching was applied to W–Mo–Cr–V high speed steel, Cr–Mo–V die steel, and type 304 and 316 austenitic stainless steels. Vapor-deposition of the polyethylene (PE) or 1H, 1H, 2H, 2H, -Perfluorodecyltriethoxysilane (PFDS) was carried out on the sputter-etched surface. The hydrophobicity was evaluated by measuring the contact angle (CA) of a water droplet on the surface. The sputter-etching formed fine and dense pillar- or cone-shaped protrusions with a diameter of 100nm to 1μm on the tool steels and the type 316 steel but cone-shaped protrusions with a diameter of more than 1μm on the type 304 steel. The surfaces of all the steels just after the sputter-etching revealed CAs smaller than 4.5°, or superhydrophilicity. On the other hand, all the steels that were sputter-etched and vapor-deposited with PE or PFDS produced CAs of more than 150°, or superhydrophobicity, except that the CA of the type 304 steel with micron-sized protrusions was 146°. The adhesion of the PFDS layer to the protrusions is much stronger than the PE layer, i.e. it is difficult to remove the PFDS layer by heating at 473K and ultrasonic cleaning in acetone.

Ion sputter etching of ZnO:Ga thin film surfaces

In this article the modification of surface morphology of ZnO:Ga (GZO) thin films by ion sputter etching is presented. GZO thin films were prepared at room temperature on Corning glass substrates by both normal and oblique angle RF diode sputtering from ZnO:2%Ga ceramic target in Ar gas. Ion sputter etching was performed by RF re-sputtering of GZO thin films on substrates. During RF sputter etching, Ar pressure of 1.3Pa and RF power of 250W were kept constant, only the time of sputter etching was changed. Ion sputter etching had remarkable influence on surface morphology of GZO thin films: increase of roughness Rq and the “homogenization” of film surfaces, i.e. skewness (Rsk) and spikiness (Rku) parameters (Rsk≈0/Rku≈3).Surface root-mean-square roughness (Rq) increased from 15.3nm (after sputter deposition) to 29.1nm (after ion sputter etching). For obliquely thin films increased from 16.5nm (after sputter deposition) to 38.2nm. Changes of these parameters Rq, Rsk, Rku influenced optical properties of GZO films, increased Haze parameter up to values 7.7% and width of optical band gap 3.44eV, respectively.

工具鋼のスパッタエッチングによって形成した微細突起物の光反射特性

Argon ion sputter etching was applied to three kinds of tool steels at a radio frequency power of 50 W to 250 W for 0.5 ks to 16.2 ks. Pillar-shaped protrusions with diameters or widths of 100 nm to 1 μm were formed on the surface of SKH51 and SKD5 steel plates, and conical protrusions of similar size were formed on the surface of the SKD61 steel plate. The size of both types of protrusions was typically comparable to the wavelength range of visible light, i.e. 400 nm to 800 nm. The absolute reflectance of the SKH51 steel surface was about 0.3% with a sputter power of 200 W and a sputter etching time of 10.8 ks. The reflectance is nearly constant and is independent of the 400 nm to 800 nm wavelength and incident angle of less than 60°. This indicates that sputter etching of tool steels can produce satisfactory anti-reflection bodies with excellent mechanical properties.

Surface modification of magnetic recording media by filtered cathodic vacuum arc

Surface modification of a magnetic recording medium was accomplished by filtered cathodic vacuum arc (FCVA). The carbon overcoat of thin-film disks was removed by Ar+ ion sputter etching in vacuum to prevent oxidation of the exposed magnetic medium, which was then modified by FCVA carbon plasma under conditions of zero and −100 V pulsed substrate bias. Monte Carlo simulations performed with the T-DYN code, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and surface force microscopy (SFM) provided insight into carbon implantation profiles, surface chemical composition, roughness, and nanomechanical properties of the surface-treated magnetic medium. The dependence of surface modification on the FCVA treatment conditions is discussed in the context of T-DYN, XPS, AFM, and SFM results. The findings of this study demonstrate the potential of FCVA to provide overcoat-free magnetic recording media exhibiting oxidation resistance and enhanced nanomechanical properties.

Preparing arrays of large atomically flat regions on single crystal substrates

We report a simple and general procedure to create arrays of atomically flat terraces onsingle crystal surfaces. Facets of three-dimensional (3D) metal islands formed afterhetero-epitaxial growth are often flat and, through annealing or growth at elevatedtemperature, the formation of rather large (micron-scale) atomically flat-top facets can bepromoted. We find that the step-free nature of top facets on such islands can be transferredto the substrate surface through room-temperature ion-sputter etching, followed by anannealing step. We use low-energy electron microscopy (LEEM) and Auger electronspectroscopy (AES) for in situ monitoring of the process steps while fabricating arrays ofstep-free surface regions on W(110), Ru(0001), Cu(100), and Fe(100) single crystals.

Modification of AZO thin-film properties by annealing and ion etching

Effects of annealing and ion etching on the structural, electrical and optical properties of sputtered ZnO:Al (AZO) thin films were investigated. The post-deposition annealing at temperatures T A = 200–400 °C in the forming gas (80% N 2/20% H 2) for 1 h and ion RF-sputter etching after annealing were used. Ion-sputter etching rate was 7 nm/min. The surface topography changed noticeably after ion-sputter etching: the surface of the sample was rougher ( R a = 33 nm) in comparison with annealed sample only ( R a = 9 nm). After the post-deposition annealing temperature T A = 400 °C and ion-sputter etching thin films have higher integral transmittance (in the range of λ = 400–1000 nm) than non-etched samples. The figure of merit ( F) became higher with increase of annealing temperature and the maximum value was F = 8%/Ω at T A = 400 °C ( R s = 10 Ω, T int = 86%).

Study of fabrication of Cu film on PFA by sputtering

Abstract Currently, chemical pretreatment and electroless plating are used to fabricate Cu films on perfluoroalkoxy vinyl ether (PFA) copolymer. In order to reduce the wastage of water during chemical pretreatment and electroless plating, we have investigated the fabrication of Cu films by a dry process as an alternative. In the present report, we have investigated the fabrication of Cu film on the PFA by using a conventional RF sputter deposition apparatus. An Ar ion sputter-etching pretreatment is performed on the PFA prior to sputter deposition; however, it does not significantly influences the peel strength and grain size. The grain size of Cu influences its resistivity in the present experiments. The resistivity increases with decreasing grain size. This result is explained by considering the scattering of conduction electrons at the grain boundaries. Further, substrate temperatures obviously influence the grain size of Cu and the peel strength between Cu and PFA. In particular, for substrate temperatures above 150 °C, the grain size and peel strength increase drastically. We can use the Cu film fabricated on the PFA substrate above 150 °C as a seed layer for CuSO 4 electroplating.

Optical ridge waveguides in SBN crystal produced by low-dose carbon ion implantation followed by a sputter etching technique

This paper demonstrates, for the first time, a method to fabricate optical ridge waveguides in SBN photorefractive crystal, i.e. by first using high-energy carbon ion implantation (forming planar waveguide substrate) followed by Ar+ ion sputter etching (constructing ridged stripes). A two-dimensional (2D) cross-sectional refractive index profile of ridge waveguide is reconstructed by carefully considering the ridged topography as well as the index distributions of the planar waveguide. Based on this profile, the waveguide modes are calculated, in which shows a reasonable agreement with the experimentally observed modal near-field intensity distributions.

Microscopic observation of transverse swelling of latewood tracheid: effect of macroscopic/mesoscopic structure

In order to study the transverse swelling/shrinkage of wood, the microscopic swelling behavior of latewood tracheid was observed using confocal laser scanning microscopy and the digital image correlation method. A microcrater structure was created on the surface of the specimen by using the ion sputter etching technique to obtain a pattern-rich digital image for image analysis. Douglas fir specimens were conditioned by two methods of absorption: rapid absorption of moisture from hot steam, and slow absorption of moisture from the water vapor of saturated solutions. Latewood tracheid near the surface of the specimen deformed only in the radial direction when the relative humidity of the surrounding air changed rapidly (rapid absorption of moisture from hot steam or absorption/desorption of moisture during the observation). In addition, the diameter of the lumen decreased upon rapid absorption of moisture, whereas it expanded upon slow absorption of moisture. These results indicate that the microscopic swelling behavior of latewood cells is strongly influenced by the macroscopic/mesoscopic structure, for instance, the cell arrangement or the alternation of latewood and earlywood.

Low temperature bonded Cu/LCP materials for FPCs and their characteristics

A new cladding process has been developed using the surface activated bonding (SAB) method. In this process, the surfaces of materials to be bonded are cleaned, activated by Ar ion sputter etching, and immediately rolled together with low distortion at room temperature in a vacuum chamber . This process is applicable not only to cladding metals but also to laminating polymer film on metal without adhesives. We focused on laminating liquid crystal polymer (LCP) on copper (Cu) foil using the SAB method , which is different from other conventional methods . We also investigated the chemical state at the interface between the Cu foil and LCP film before and after heat treatment (up to 300/spl deg/C), by comparing with that on raw LCP film. All laminated materials were etched and cropped out, and the LCP surfaces were analyzed with X-ray photoelectron spectrometer (XPS). After the heat treatment, the ratio of C=O increased with increasing heat treatment temperature. It indicated that, under the high temperature of the heat treatment, the oxidation occurs not only at the Cu foil/sputtered Cu but also the LCP surfaces. We reported previously that the peel strength of laminated material made by the SAB method was improved by using Cu sputtering on the LCP film , . But after a heat-resistance test, the peel strength significantly decreased. This decrease resulted from the oxidation around the interface between the Cu foil/sputtered Cu and the LCP film due to gas permeation through the LCP film, and the softening of the Cu foil by its recrystallization due to high temperature. To prevent this loss of peel strength, we used Cu-0.02%Zr alloy foil with a higher recrystallization temperature and sputter Cu-Ni alloy or Ni-Cr alloy on the LCP film instead of Cu. It is also shown that the Cu/LCP materials produced by the SAB method have excellent electrical properties and etching ability.

Effects of Charging and Crystallinity on Sputter-Etching Rate of Al2O3 Single Crystal

In this study, we examined Ar+ ion sputter etching rate ratio RAl203/RSiO2 under different surface charging conditions and in different incident azimuthal directions of Ar+ ion. When the surface charging of specimen was neutralized by irradiation with low-energy electrons, RAl2O3 became larger than that of specimens without any electron irradiation at same ion current density. When the specimen was bombarded by Ar+ ion from the azimuthal direction parallel to the a-axis on the surface of Al2O3 single crystal, RAl2O3/RSiO2 became higher than that of specimen bombarded from the azimuthal direction vertical to the a-axis. The effects of surface charging and incident azimuthal direction of Ar+ ion on RAl2O3/RSiO2 are discussed respectively on the basis of the experimental results.