Wet Chemical Treatment Research Articles

Atmospheric Plasma surface treatment of Styrene-Butadiene Rubber

Thermoplastic rubbers are widely used in a large number of applications (e.g. footwear, adhesives manufacturing, molded or extruded goods). Due to the non-polar nature of these rubbers, poor adhesion is achieved with polar polyurethane (PU) adhesive thus, a surface treatment is required to chemically modify the rubber surface and produce suitable joints. Surface treatments have been demonstrated to be suitable for the improvement of adhesion and wettability properties of non-polar synthetic rubbers. Over the last two decades progresses in adhesion of rubber were achieved by changing of the ingredients in rubber composition or by modifying surfaces by the use of a chemical agent (halogenation, cyclization, etc.) or using high energy irradiation such as bombarding the surface by electron beam or gamma irradiation. Actually, wet-chemical treatments are not well acceptable because of environmental and safety considerations and question on uniformity and reproducibility. Plasma surface treatment process was been proposed as an environmentally friendly and have gained large acceptance because it can be easily integrated into existing production lines and because their effectiveness in the treatment of several materials with different shapes and sizes. The effectiveness of plasma treatment on enhancement of adhesion depends on the gas used to generate the plasma and also on the formulation of the rubber. Vulcanized rubbers like, styrene-butadiene rubber (SBR), are especially difficult to bond due to low molecular weight ingredients in their formulation that may migrate to the rubber surface limiting its interaction with the adhesive. This study attempts to find an alternative treatment to improve the adhesion of SBR surface and PU adhesive. Plasma treatments were performed in an air plasma system from Acxys and were selected three types of SBR rubbers with different percentages of styrene-butadiene which were provided by Procalcado. The effect of experimental variables such as distance, speed and scan number on the adhesion of PU adhesive was evaluated and compared with halogenated SBR rubbers.

Enhancement of STT-RAM Characteristics by Wet Clean Treatment after MTJ Etch Process

ABSTRACTThe effect of wet chemical treatment on the magnetic tunneling junction (MTJ) was examined. The tunneling magneto-resistance (TMR) increased and the resistance of anti-parallel state and parallel state decreased when a wet cleaning treatment was carried out after a reactive ion etching process. Furthermore, the exfoliation between the capping layer and Inter layer Dielectric (ILD) was prevented. Presumably, these were due to the elimination of the damaged layer and the residues. This investigation showed that the wet treatment after the MTJ patterning using RIE process could improve the MTJ properties without degradation of Hc, such as TMR and Rlow.

Investigation of surface pre-treatments for the structural bonding of titanium

This paper evaluates wet-chemical pre-treatments (alkaline etching, anodising) and a plasma treatment for structural bonding of titanium (Ti6Al4V). The main objective of this study is the comparison of the applicability of the plasma pre-treatment to wet-chemical treatments on titanium for structural bonding. In this context, an atmospheric pressure plasma device was used to deposit thin functional films from hexamethyldisiloxane (HMDSO) precursor on titanium.X-ray photoelectron spectroscopy (XPS) was employed to assess the chemical composition of the surface after different pre-treatments on the titanium substrate, while the morphology and the film thickness were investigated with scanning electron microscopy (SEM). The adhesion properties on titanium were evaluated by means of a wedge test in hot/wet conditions. After bonding tests the fracture surface and the failure loci were analysed.Using a long arc plasma generator and HMDSO precursor almost stoichiometric SiO2 coatings were obtained on the titanium substrate. These coatings exhibit good long-term durability and bond strength compared to an alkaline etching in the wedge test. The investigated anodising process leads to oxide layers revealing a highly porous nanostructure. In contrast to the alkaline etching, the plasma derived coatings and the oxide layer produced by the anodising process exhibit a higher micro, respectively nano roughness, and hence a better long-term durability.

Characterization of Semiconductor Surfaces during Surface Conditioning and Functionalization

Semiconductor surface cleaning, passivation and functionalization are critical steps for applications such as microelectronics, MEMS, sensors, and solar energy harvesting. Progress has relied in part on the development of surface chemical treatments. However, the ability to characterize surfaces at all steps of processing has also been essential and will be emphasized here. This work focuses on the chemical modification of oxide-free, hydrogen-passivated silicon, including wet chemical treatments, atomic layer deposition, and physical deposition. Characterization methods include in-situ infrared absorption spectroscopy, low energy ion scattering, x-ray photoelectron spectroscopy and mass spectrometry, and is complemented by ex-situ spectroscopic ellipsometry and atomic force microscopy.

Structural and Thermal Behaviors of Iron-Filled Align Carbon Nanotubes Formulated by Two-Stage Catalytic Chemical Vapor Deposition

Finding on the one-dimensional purified aligned carbon nanotubes (ACNT) was prepared using botanical hydrocarbon: camphor powder in a two-stage catalytic chemical vapor deposition will be presented. For the first time, the hydrocarbon source and catalyst were patterned in different alumina boats in the system. The growth of ACNT has achieved free standing formation with higher aspect ratio. In contrast, unpurified carbon nanotubes have some drawbacks and require some treatments to fully utilize their capabilities in various applications. The results reveal that the crystallinity and purity of functionalized align carbon nanotubes was increased after wet-chemical technique and heat treatment process. In this paper, the results provide evidence showing that it was in good agreement with the field emission scanning electron microscopy, micro-Raman and thermogravimetric analysis.

Influence of surface activation on the hydrogen permeation properties of PdAg cathode membrane

The influence of surface oxidation and hydrogen upload into the Pd 0.79Ag 0.21 membrane on hydrogen permeation was examined by measuring the permeation of: 1) gas-phase H 2 sent from the electrode back-side and 2) electrolytic H 2 produced on electrolyte side. It was verified that hydrogen upload into PdAg lattice has positive effect i.e. increases hydrogen permeation, while surface oxides formed during and after electrolysis cycles are the main factors acting on decrease of hydrogen permeation. Particularly, silver oxides are identified as permeation-blocking species. Consequently, several treatments were proposed aiming to reduce electrode deactivation; beside wet chemistry treatments applicable after electrolysis, the in situ electrode reactivation by ultrasonic pulses was presented.

Passivation of Germanium Surfaces by a Quinhydrone–Methanol Solution Treatment

The bulk lifetime of minority carriers, τb, in germanium (Ge) is one of the most important material parameters in the design and fabrication of Ge-based solar cells. Surface passivation of Ge substrates is indispensable to the accurate evaluation of τb. We have found that a newly developed wet chemical treatment, quinhydrone–methanol (Q/M) solution treatment, effectively passivates Ge surfaces, achieving a surface recombination velocity (S) of less than 20 cm/s. It has been clarified that oxide layers containing the molecules from the Q/M solution were formed on the Ge surfaces treated with the Q/M solution. Ge dangling bonds (DBs) are thought to be terminated by these oxygen related molecules. Band bending in the Ge substrates induced by the oxide layers adsorbed on the Q/M-treated Ge surface can contribute to the reduction in S. We also briefly discuss the properties of a recombination center found in the bulk of highly resistive Ge substrates.

Splitting and broadening of the emission bands of Y2O3:Eu3+,Nd3+ and its dependence on Nd3+ concentration and annealing temperature

Although Eu3+ ion-doped Y2O3 has been extensively used as red phosphors, their color rendering needs to be improved for high-quality illumination and displaying. Here, we show that the emission spectra of Y2O3:Eu3+ red phosphors can be broadened by the doping of Nd3+ ion so that the color rendering capability of Y2O3:Eu3+ was remarkably enhanced. Y2O3:Eu3+ and Y2O3:Eu3+,Nd3+ colloidal spheres were synthesized by wet chemical procedure and high-temperature treatment. The fluorescence measurement under the 254 and 380 nm ultraviolet excitation indicates that the 612 nm red emission peak of Eu3+ can be splitted into two ones by the doping of Nd3+ ion, of which the full width at half maximum (FWHM) is broadened from 4.2 nm to 9.6 nm. By varying the concentration of Nd3+ ion, it was determined that the optimal doping concentration of Nd3+ ion is of 3 mol% for realizing the strongest emission intensity. The further increase of Nd3+ ion exceeding 3 mol% would lead to a concentration quenching phenomenon. The analysis based on XRD spectra and the simplified energy diagram suggested that the doped Nd3+ ion not only monitored the growth dynamics, but also took an efficient energy transfer and a cross relaxation process to generate intense emission from Eu3+ ion in both of C2 and S6 sites, instead of preferable one type of Eu3+ site (C2 or S6) in the Nd3+ undoped sample.

Epitaxial graphene surface preparation for atomic layer deposition of Al2O3

Atomic layer deposition was employed to deposit relatively thick (∼30 nm) aluminum oxide (Al2O3) using trimethylaluminum and triply-distilled H2O precursors onto epitaxial graphene grown on the Si-face of silicon carbide. Ex situ surface conditioning by a simple wet chemistry treatment was used to render the otherwise chemically inert graphene surface more amenable to dielectric deposition. The obtained films show excellent morphology and uniformity over large (∼64 mm2) areas (i.e., the entire sample area), as determined by atomic force microscopy and scanning electron microscopy. X-ray photoelectron spectroscopy revealed a nearly stoichiometric film with reduced impurity content. Moreover, from capacitance-voltage measurements a dielectric constant of ∼7.6 was extracted and a positive Dirac voltage shift of ∼1.0 V was observed. The graphene mobility, as determined by van der Pauw Hall measurements, was not affected by the sequence of surface pretreatment and dielectric deposition.

Electrical Characterization of $\hbox{Al}_{2} \hbox{O}_{3}$/n-InAs Metal–Oxide–Semiconductor Capacitors With Various Surface Treatments

Ex situ sulfide and HCl wet chemical treatments in conjunction with in situ trimethyl aluminum (TMA) pretreatment were performed before the deposition of Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> on n-InAs surfaces. X-ray photoelectron spectroscopy analyses show a significant reduction of InAs native oxides after different treatments. The capacitance-voltage <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> characterization of Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /n-InAs structures shows that the frequency dispersion in the accumulation regime is small (<; 0.75%/dec) and does not seem to be significantly affected by the different surface treatments, whereas the latter improves depletion and inversion behaviors of the n-channel metal-oxide-semiconductor capacitors. The interface trap density profiles extracted from the simulation mainly show donorlike interface states inside the InAs band gap and in the lower part of the conduction band. The donorlike traps inside the InAs band gap and in the lower part of the conduction band were significantly reduced by using wet-chemical-plus-TMA treatments, in agreement with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> characteristics.

A comparative study of silicon surface passivation using ethanolic iodine and bromine solutions

We report the surface passivation studies made on p-type single-crystalline silicon wafers using ethanolic solution of iodine and bromine. Minority carrier lifetime (τeff) is measured by the microwave photoconductance decay (μ-PCD) method and using a Sinton's lifetime tester. Measurements are carried out at different molar concentrations of iodine–ethanol (I–E) and bromine–ethanol (B–E) solutions to optimize the process parameters. It is found that good passivation (±5% of measured maximum lifetime) could be achieved for certain ranges of concentration, which in the case of I–E and B–E are 0.07–0.12M and 0.05–0.07M, respectively. The effect of pre-conditioning steps on surface passivation (silicon surfaces with and without native oxide) is investigated. It is shown that the quality of surface passivation can be improved by an optimized wet-chemical pre-conditioning treatment. The effect of bias light and passivation time is also studied. I–E solution provides better passivation than B–E solution in terms of τeff whereas B–E solution passivation exhibits better stability in comparison with I–E solution. The τeff measured by the Sinton method (WCT-120) and using a Semilab system (μ-PCD, WT-2000) are comparable if injection levels are matched.

Influence of trapping states at the dielectric–dielectric interface on the stability of organic field-effect transistors with bilayer gate dielectric

Wet-chemical treatment on the gate dielectric, i.e. tuning the chemical properties via the choice of the buffer dielectric, has been widely employed to study the morphology and growth mode of organic semiconductors (OSCs). Through these studies, further understanding of charge transport mechanisms is obtained, and the electrical performances of organic field-effect transistors (OFETs), e.g. charge carrier mobility, on/off current ratio and subthreshold swing, thus have been greatly improved. In order to achieve a useful device, its stability becomes extremely important. In this article, the study on the charge trapping at the dielectric–dielectric interface by using the combination of poly(methyl methacrylate) (PMMA) and silicon dioxide (SiO 2) dual-dielectric was carried out under dark and illuminated conditions. Our results showed that the thickness of the PMMA layer, determining the film uniformity and the magnitude of charge injection barrier, plays a decisive role in the charge trapping process. With the thickness optimized, the device stability is greatly enhanced. Our findings bring about a low-cost, easy-to-realize fabrication method to produce high-performance and stable/reliable OFETs.

Study of hydrophilicity and stability of chemically modified PDMS surface using piranha and KOH solution

AbstractSuccessful realization of various BioMEMS devices demands effective surface modification techniques of PDMS elastomer. This paper presents a detailed report on a simple and cost effective approach for surface modification of PDMS films involving wet chemical treatment in two‐step processes: primarily involving piranha solution followed by KOH dip to improve hydrophilicity and stability of PDMS surface. Chemical composition of the solution and surface treatment condition have been varied and optimized to significantly increase the surface energy. The effect of surface modification of the elastomer after wet chemical treatment is analyzed using contact angle measurement and FTIR‐ATR study. PDMS surface treated in piranha solution with H2O2 and H2SO4 in the ratio of 2:3 followed by a dip in KOH solution for 15 min duration each, demonstrated a maximum reduction of contact angle to ∼27° as compared to untreated sample having a contact angle of ∼110°. The removal of hydrophobic methyl group from elastomer surface and subsequent hydrophilization of surface by wet chemical process was confirmed from FTIR‐ATR spectra. This result is also supported by improved adhesion and electrical continuity of deposited aluminum metal film over the modified PDMS surface. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Optimization of desmear process for high adhesion of insulating film in printed circuit boards (PCBs) via Taguchi method

In order to achieve a high peel strength (above 1.2 kg f cm −1) for the insulating layer in printed circuit boards (PCBs), the conditions of the desmear process (swelling, etching, reduction, and acid dip) and curing time were optimized via the Taguchi method. The desmear parameters governing the adhesion of plated metals to insulating epoxy layers were evaluated by measuring the ultimate peel strength. The signal-to-noise ( S/ N) ratio was maximized under the optimized precuring and desmear conditions. The expected value at the maximum S/ N ratio was correlated well with the actual experimental results. The peel strength under the optimized experimental conditions was between 1.2 and 1.4 kg f cm −1, which is approximately two times greater than that obtained one when using the general wet chemical treatment.

Experimental and Modeling on Atomic Layer Deposition Al2O3/n-InAs Metal-Oxide-Semiconductor Capacitors with Various Surface Treatments

Ex-situ sulfide and HCl wet chemical treatments in conjunction with in-situ trimethyl aluminum (TMA) pretreatment were performed before the deposition of Al2O3 on n-InAs surfaces. X-ray photoelectron spectroscopy analyses show a significant reduction of InAs native oxides after different treatments. Capacitance-voltage (C-V) characterization of Al2O3/n-InAs structures shows that the frequency dispersion in accumulation regime is small (<0.75% per decade) and does not seem to be affected significantly by the different surface treatments, whereas the latter improves depletion and inversion behaviors of the nMOS capacitors. The interface trap density profiles extracted from simulation show mainly donor-like interface states inside the InAs bandgap and in the lower part of the conduction band. The donor-like traps inside the InAs bandgap and in the lower part of the conduction band were significantly reduced by using wet chemical plus TMA treatments, in agreement with C-V characteristics.

Room-Temperature Direct Bonding Using Fluorine Containing Plasma Activation

Room-temperature Si/Si wafer direct bonding has been achieved successfully without wet chemistry treatment as well as no requiring annealing. Very strong bonding strength of Si/Si pairs, close to the bulk-fracture strength of silicon, is demonstrated at room temperature thanks to adding small amount of carbon tetrafluoride (CF4) into oxygen plasma treatment. The surface energies of bonded Si/Si wafer pairs were influenced by plasma treatment parameters. Moreover, the wafer surfaces and the bonding interfaces are analyzed to explore the bonding mechanism. Adding small amount of CF4 into O2 plasma does not etch the Si surface in a short time (∼60 s), but it renders fluorinated oxide grown on the Si surface, which should be less hydrophilic than the surface treated by O2 plasma. Therefore, fewer water molecules at bonding interface may be prone to produce many covalent bonds via polymerization reaction and result in strong bonding at room temperature.

Recycling microcavity optical biosensors.

Optical biosensors have tremendous potential for commercial applications in medical diagnostics, environmental monitoring, and food safety evaluation. In these applications, sensor reuse is desirable to reduce costs. To achieve this, harsh, wet chemistry treatments are required to remove surface chemistry from the sensor, typically resulting in reduced sensor performance and increased noise due to recognition moiety and optical transducer degradation. In the present work, we suggest an alternative, dry-chemistry method, based on O2 plasma treatment. This approach is compatible with typical fabrication of substrate-based optical transducers. This treatment completely removes the recognition moiety, allowing the transducer surface to be refreshed with new recognition elements and thus enabling the sensor to be recycled.

Surface modifications of polypropylene membranes used for blood filtration

The surface of two commercial meltblown polypropylene (PP) membranes, used for the filtration of blood products, were modified by wet chemistry treatments (carbodiimide, tosyl chloride and trihalogeno-triazines) in the case of the oxygen-plasma treated membrane ( O 2 -PP), and by photochemistry using molecular clips in the case of the native PP membrane. The most efficient technique uses trifluoro-triazine reagent for the activation of both hydroxyl- and carboxyl-functions of O 2 -PP. It enables the fixation of amine-terminated molecules with high degrees of derivatization (∼700 pmol/cm 2), without inducing modification of the membrane morphology nor cytotoxicity. Only a weak decrease of surface hydrophilicity was measured after the treatments and steam-sterilization. This method was applied for the grafting of peptides (Gly-Gly-Gly-Gly-Gly, Gly-Arg-Gly-Asp-Ser, home-made modified Leu-Asp-Val) on O 2 -PP membranes incorporated into multi-layer filter devices. These modified filters showed improved properties of leukocyte depletion in blood filtration experiments, principally due to the wetting properties of the membranes.

Toward Intrinsic Graphene Surfaces: A Systematic Study on Thermal Annealing and Wet-Chemical Treatment of SiO2-Supported Graphene Devices

By combining atomic force microscopy and trans-port measurements, we systematically investigated effects of thermal annealing on surface morphologies and electrical properties of single-layer graphene devices fabricated by electron beam lithography on silicon oxide (SiO(2)) substrates. Thermal treatment above 300 °C in vacuum was required to effectively remove resist residues on graphene surfaces. However, annealing at high temperature was found to concomitantly bring graphene in close contact with SiO(2) substrates and induce increased coupling between them, which leads to heavy hole doping and severe degradation of mobilities in graphene devices. To address this problem, a wet-chemical approach employing chloroform was developed in our study, which was shown to enable both intrinsic surfaces and enhanced electrical properties of graphene devices. Upon the recovery of intrinsic surfaces of graphene, the adsorption and assisted fibrillation of amyloid β-peptide (Aβ1-42) on graphene were electrically measured in real time.

Novel Wet Chemical Copper Metallization for Glass Interposers

The focus of the chip and IC substrate manufacturing industry for interposers is currently shifting from organic substrates to inorganic materials. Interposers overcome the dimensional mismatch between a die and an organic PWB substrate and need to buffer the differences in thermal expansion between these two materials. While inorganics like silicon and glass, have a low CTE value compared to organic material, glass has some significant advantages over silicon. These are namely material cost, availability in panel size and a better electrical insulation. In order to further increase the cost advantage, metallization could be done by either electroless or electrolytic copper plating as an alternative route to sputter technology. Both wet chemical processes are well established in PWB manufacturing and need adaptation to glass substrates. Compared to sputtering, 3D-features can be covered with a wet chemical treatment in a comparatively economical process. Filling of TGVs (Through Glass Vias) by electrolytic copper plating requires the presence of a conductive film which is created by applying electroless copper deposition of typically 300–500nm thickness. The general issue is poor adhesion to the smooth glass surfaces. To improve adhesion between glass and metal, various treatments were assessed in this study: Mechanical anchoring was achieved by etching the substrate (subtractive) as well as by depositing nano-sized silica particles (additive). Both treatments are in solution and 3D-features are accessible in contrast to a purely mechanical approach. Surface treatments without inducing additional roughness included the adsorption of functional metal-affine polyelectrolytes and silanization for conditioning which enhanced the adhesion of the copper layer to various degrees. To study the impact of chemical formulation on strain/stress development and relaxation in the film as a key impact factor for blister (adhesion) performance, the electroless copper layer growth was monitored by in-situ XRD methods during and after deposition.