Surface Cleaning Procedure Research Articles

Study of optical and passivation properties of hydrogenated silicon carbide thin films deposited by reactive magnetron sputtering for c-Si solar cell application

In this paper, optical and passivating properties of hydrogenated silicon carbide synthesized by reactive magnetron sputtering for c-Si solar cell application were studied. SiC:H films were synthesized by sputtering a SiC target in an argon-hydrogen ambient at a Radio Frequency (RF) power of 100–250 W. The thickness, density, and roughness of the films were measured by X-ray reflectometry. The optical properties of the films were studied by UV–visible spectroscopy. It is shown that with an increase in RF power, the refractive index increases from 1.53 to 2.32 (at λ = 633 nm), and the extinction coefficient does not exceed 0.009 in most of the visible and near-IR spectrum. Based on the measured optical constants using computer simulation the optimal thicknesses were calculated to maximize antireflection effect. IR spectroscopy showed correlation between the structure and physical properties of the films. It has been established that, at a lower RF power (100–150 W), particles are deposited instead of atoms. This leads to the formation of voids at the particle boundaries, which are subsequently filled with oxygen. Using the non-contact microwave photoconductance decay method, it was shown that the maximum effective lifetime (τeff) is achieved at RF power of 250 W. In addition, influence of preliminary surface cleaning procedure and post-annealing in vacuum on the τeff was considered.

Improved Photoactivity Of NiO/ZnO Nanorods Heterostructured Films Relying On Scaffold Surface Cleaning And NiO Deposition Time Optimization

AbstractHerein, a surface cleaning procedure involving vacuum annealing under oxygen was applied for cleaning the zinc oxide nanorod (ZNR) scaffold film's surface before nickel oxide (NiO) deposition for heterostructure formation. The scaffold properties (surface stoichiometry, defects fluctuation, Fermi level shift, carrier concentration) were studied as a function of the vacuum level and the NiO deposition time and correlated to the NiO/ZNR interface (charge transfer resistance, band bending) and photo‐response properties. The surface cleaning under a higher vacuum enabled the adsorbate and surface oxygen vacancy passivation but also influenced the surface doping. Our best performing NiO/ZNR interface in terms of photocatalytic efficiency was composed of a high‐vacuum‐cleaned (0.5 Pa) ZNR scaffold and 40 s sputter deposited NiO layer which was post‐annealed. The high photocatalytic efficiency could be correlated with a maximized near‐band edge emission, effective band bending, low charge transfer resistance (as proven by photoelectrochemical impedance measurements), and optimum light harvesting (maximized photocurrent density). The optimized NiO/ZNR showed about 1.5 times increase in photo‐response and improved photodegradation efficiency compared to the ZNR scaffold.

Laser-induced deformation and fragmentation of droplets in an array

Droplet–droplet interactions is ubiquitous in various applications ranging from medical diagnostics to enhancing and optimizing liquid jet propulsion. We employ an experimental technique where the laser pulse interacts with a micron-sized droplet and causes optical breakdown. The interaction of a nanosecond laser pulse and an isolated spherical droplet is accurately controlled and manipulated to influence the deformation and fragmentation of an array of droplets. We elucidate how the fluid dynamic response (such as drop–drop and shock–drop interactions) of an arrangement of droplets can be regulated and optimally shaped by laser pulse energy and its interplay with the optical density of liquid target. A new butterfly type breakup is revealed, which is found to result in controlled and efficient fragmentation of the outer droplets in an array. The spatio-temporal characteristics of a laser-induced breakdown dictate how shock wave and central droplet fragments can influence outer droplets. The incident laser energy and pulse width employed in this work are representative of diverse industrial applications such as surface cleaning, nano-lithography, microelectronics, and medical procedures such as intraocular microsurgery.

Scanning tunneling microscopy of strained-α-Sn(0 0 1) surface grown on InSb(0 0 1) substrate

We investigated the surface structure of strained-α-Sn layers grown on InSb(001) surfaces, which have been attracting the attention of the researchers in the field of topological materials, by optimizing the surface cleaning procedures of the InSb substrate surfaces and the growth conditions of the Sn layers. Accordingly, scanning tunneling microscopy observations showed that the (2 × 2) diffraction patterns are due to the double domain (2 × 1) reconstructed surfaces rotated 90° with respect to one another, as previously suggested based on diffraction observations.

Effect of laser cleaning of carbon fiber-reinforced polymer and surface modification on chemical activity and bonding strength

Bonding has been used to repair carbon fiber-reinforced polymer (CFRP) materials. However, research has shown that resin residue on the surface of CFRP can cause adhesion problems. Therefore, a reliable surface cleaning procedure is necessary to remove the resin residue before bonding. In this paper, the surface resin was removed by laser cleaning, while the surface properties of CFRP were improved. A pulsed laser cleaning experiment was designed to study the chemical activity and bonding strength of CFRP treated by laser with different laser power and scanning speed. The results showed that as the contact angle of the material surface decreased, chemical activity and adhesive properties were improved. The surface pretreated with laser power of 16 W (scanning speed of 1500 mm/s) had no resin residue and the best adhesive properties; the bonding strength was 1.6 times higher than that of the untreated surface, and the failure mode was dominated by a cohesive damage mode.

Non-invasive reflection FT-IR spectroscopy for on-site detection of cleaning system residues on polychrome surfaces

The control of surface cleaning procedures of paintings is difficult and residues of cleaning materials can remain on the surface as potential risk factors for the integrity of the original paint layers. Therefore, the development of a suitable analytical strategy for in situ detection of cleaning residues directly on the painting surface is essential.In the present study, we propose reflection FT-IR spectroscopy as non-invasive tool for monitoring cleaning residues from polychrome surfaces. Tests on simplified model paints allowed defining the analytical strengths both in term of selectivity and detection limits towards thickeners, surfactants and chelating agents most commonly used in cleaning formulations. Subsequently, the detection of these components has been assessed on aged paint mock-ups and an easel painting after cleaning with different gel formulations. The obtained results clearly proved the strengths of reflection FT-IR spectroscopy for a real time, non-invasive detection of cleaning residues on polychrome surfaces. Thickeners such as Klucel® G, surfactants including Ethomeen® C/12 and C/25 and chelating agents (citric acid + TEA, tetrasodium EDTA salt) were clearly detected after dry removal of the gels and in some tests also after the clearance step.

Effect of annealing on the surface characteristics of α-Al2O3(0001) probed by XPS

α-Al2O3(0001) is a technologically important metal oxide substrate used in current solid state electronic devices. This report presents the effect of heat treatment on the surface electronic structure characteristics of α-Al2O3(0001) substrates examined by x-ray photoelectron spectroscopy. Survey spectra, O 1s, Al 2p, Al 2s core levels, and valence band spectra are presented for the as received, vacuum annealed, and oxygen annealed substrates. Annealing removes various contaminants such as C, Zn, and OH groups from the surface, and a sharp (1 × 1) low energy electron diffraction pattern confirms the ordered hexagonal periodicity of the surface. No substantial differences in the valence band spectra are observed due to annealing and suggest that the (1 × 1) surface characteristics of α-Al2O3(0001) are preserved during the surface cleaning procedures.

Antimicrobial efficacy of Thymbra capitata (L.) Cav. essential oil loaded in self-assembled zein nanoparticles in combination with heat

This study reports on the chemical composition of Thymbra capitata essential oil (TCEO) and its antimicrobial activity when applied with heat either as a suspension (s-TCEO) or loaded in self-assembled zein nanoparticles (zn-TCEO). Zein, a plant protein isolated from corn and maize, is proposed as natural, and biocompatible carrier. TCEO composition was analysed by GC–MS, and 35 components were identified. Carvacrol, a monoterpenoid, was the major constituent (73.8%). zn-TCEO were prepared under low shear conditions and characterized according to droplet size (<180 nm) and encapsulation efficiency (77.8%). The two TCEO formulations (s-TCEO and zn-TCEO) were compared in terms of antibacterial activity against Escherichia coli O157:H7 Sakai and Listeria monocytogenes EGD-e. The zn-TCEO displayed a greater bacteriostatic activity than s-TCEO, probably due to their improved dispersion in the growth media. However, zn-TCEO exerted a lower bactericidal activity than s-TCEO, probably due to the EO progressive release. The combination of TCEO and heat (53 °C) exerted valuable synergistic lethal effects, causing the death of up to 5 log10 cycles of both microorganisms. The effectiveness of zn-TCEO was especially improved at pH 4.0. Therefore, the application of this new delivery system, designed to encapsulate and protect EOs, and ensure their controlled release, might represent an advantageous alternative for food, cosmetic or pharmaceutical industries to improve the efficacy of higienization processes or surface cleaning and disinfection procedures when combined with mild heat.

Electrical contact uniformity and surface oxidation of ternary chalcogenide alloys

Uniform metal contacts are critical for advanced thermoelectric devices. The uniformity of the contact resistance for gold, tungsten, and SrRuO3 electrodes on polycrystalline ternary Bi2Te3-based alloys for different types of surface cleaning procedures was characterized. The presence of a nanometer-thick native oxide layer on the Bi2Te3 surface leads to large and non-uniform contact resistance. Surface treatments included solvent cleans and chemical and dry etching prior to metallization of the Bi2Te3. Only etching the surface led to a significant improvement in contact resistance uniformity. None of the tested contacts reacted with the underlying Bi2Te3 substrate. Etching resulted in the removal of the native oxide on the Bi2Te3 surface, which was characterized using X-ray photoelectron spectroscopy (XPS). The average thickness, chemistry, and dry etch rate of the native oxide was further characterized using XPS. The non-uniformity in contact resistance suggests that the native oxide grows non-uniformly on polycrystalline bismuth telluride surfaces.

UV-laser cleaning and surface characterization of an aerospace carbon fibre reinforced polymer

In the recent aerospace generations, composite materials have shown that they can fulfil the increasing demand for structural efficiency. In this context adhesive bonding could be used to max out the material properties of carbon fibre reinforced polymers (CFRP). However, investigations have shown that residues of release agents on the CFRP surface can cause adhesion problems. Thus, a reliable surface cleaning procedure for removing residues prior to bonding is necessary.Analytical surface investigations of an Aerospace CFRP material revealed the thickness and morphology of the predominant adhesion-weakening contamination. The optical absorptions of the epoxy material and the release agent characterised by UV–vis measurements were considered to develop a cleaning model based on a ns-pulsed ultra-violet laser with 266nm wavelength. This removal mechanism leads to chipping and peeling of the release agent layer and could be supported with light microscopy, scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) investigations. Single lap shear tests of the CFRP samples in the pristine and contaminated state, pre-treated with UV-laser as well as with the reference process (grinding) show that the laser pre-treated samples lead to the highest joint strength in the study. The failure mode changed from adhesion failure in the pristine state to a failure in the fibre-resin interface after laser treatment. Comparing a laser parameter with the focus on a smooth cleaning process and a laser parameter that lead to a surface with exposed carbon fibres, the surfaces treated with the smooth laser parameter showed the higher joint strength. The measured joint strength was 100% higher than with grinding, which underlines the high potential of laser technology for CFRP surface pre-treatment.

Evaluation of Surface Cleaning Procedures for CTGS Substrates for SAW Technology with XPS.

A highly efficient and reproducible cleaning procedure of piezoelectric substrates is essential in surface acoustic waves (SAW) technology to fabricate high-quality SAW devices, especially for new applications such SAW sensors wherein new materials for piezoelectric substrates and interdigital transducers are used. Therefore, the development and critical evaluation of cleaning procedures for each material system that is under consideration becomes crucial. Contaminants like particles or the presence of organic/inorganic material on the substrate can dramatically influence and alter the properties of the thin film substrate composite, such as wettability, film adhesion, film texture, and so on. In this article, focus is given to different cleaning processes like SC-1 and SC-2, UV-ozone treatment, as well as cleaning by first-contact polymer Opticlean, which are applied for removal of contaminants from the piezoelectric substrate CaTaGaSiO. By means of X-ray photoelectron spectroscopy, the presence of the most critical contaminants such as carbon, sodium, and iron removed through different cleaning procedures were studied and significant differences were observed between the outcomes of these procedures. Based on these results, a two-step cleaning process, combining SC-1 at a reduced temperature at 30 C instead of 80 C and a subsequent UV-ozone cleaning directly prior to deposition of the metallization, is suggested to achieve the lowest residual contamination level.

Study of radiative heat transfer in \xc5ngstr\xf6m- and nanometre-sized gaps

Radiative heat transfer in Ångström- and nanometre-sized gaps is of great interest because of both its technological importance and open questions regarding the physics of energy transfer in this regime. Here we report studies of radiative heat transfer in few Å to 5 nm gap sizes, performed under ultrahigh vacuum conditions between a Au-coated probe featuring embedded nanoscale thermocouples and a heated planar Au substrate that were both subjected to various surface-cleaning procedures. By drawing on the apparent tunnelling barrier height as a signature of cleanliness, we found that upon systematically cleaning via a plasma or locally pushing the tip into the substrate by a few nanometres, the observed radiative conductances decreased from unexpectedly large values to extremely small ones—below the detection limit of our probe—as expected from our computational results. Our results show that it is possible to avoid the confounding effects of surface contamination and systematically study thermal radiation in Ångström- and nanometre-sized gaps.

Electrocatalysis on shape-controlled metal nanoparticles: Progress in surface cleaning methodologies

The use of shape-controlled metal nanoparticles has produced not only a clear enhancement in the electrocatalytic activity of different reactions of interest but also a better understanding of the effect of the surface structure on nanoscaled materials. However, it is well-accepted that a correct understanding of the correlations between shape/surface structure and electrochemical reactivity indispensably requires the use of clean surfaces. In this regard, and considering that most of the synthetic methodologies available in the literature for the preparation of these shaped metal nanoparticles employ capping agents, the development of effective surface cleaning methodologies able to remove such capping agents from the surface of the corresponding nanoparticles, becomes an extremely important prerequisite to subsequently evaluate their electrocatalytic properties for any reaction of interest. Consequently, in this contribution, we summarize the most relevant advances about surface cleaning procedures applied to different shaped metal nanoparticles for electrocatalytic purposes. It is worth mentioning that this work will only include contributions in which the surface cleanness of the samples is specifically evaluated using well-established electrochemical tools.

Evaluation of Surface Cleaning Procedures in Terms of Gas Sensing Properties of Spray-Deposited CNT Film: Thermal- and O₂ Plasma Treatments.

The effect of cleaning the surface of single-walled carbon nanotube (SWNT) networks by thermal and the O2 plasma treatments is presented in terms of NH3 gas sensing characteristics. The goal of this work is to determine the relationship between the physicochemical properties of the cleaned surface (including the chemical composition, crystal structure, hydrophilicity, and impurity content) and the sensitivity of the SWNT network films to NH3 gas. The SWNT networks are spray-deposited on pre-patterned Pt electrodes, and are further functionalized by heating on a programmable hot plate or by O2 plasma treatment in a laboratory-prepared plasma chamber. Cyclic voltammetry was employed to semi-quantitatively evaluate each surface state of various plasma-treated SWNT-based electrodes. The results show that O2 plasma treatment can more effectively modify the SWNT network surface than thermal cleaning, and can provide a better conductive network surface due to the larger number of carbonyl/carboxyl groups, enabling a faster electron transfer rate, even though both the thermal cleaning and the O2 plasma cleaning methods can eliminate the organic solvent residues from the network surface. The NH3 sensors based on the O2 plasma-treated SWNT network exhibit higher sensitivity, shorter response time, and better recovery of the initial resistance than those prepared employing the thermally-cleaned SWNT networks.

Efficiency of micro-nebulized hydrogen peroxide dry mist in improving disinfection of titanium and polypropylene surfaces used in the medical area

Most hard surface cleaning and disinfection procedures adopted in healthcare facilities are not effective in inactivating bacteria where a biofilm is already formed and may be a cause of cross-contamination of clean areas. Airborne disinfection performed with micro-nebulized H2O2 dry particles may be used as additional step capable to inactivate the bacteria and prevent clean areas cross-contamination.

Improvement of epitaxial channel quality on heavily arsenic- and boron-doped Si surfaces and impact on performance of tunnel field-effect transistors

We evaluate the impact of tunnel junction quality on the performance of tunnel field-effect transistors (TFETs). The interface between epitaxially grown channel and source surface was used as tunnel junctions. Performing a sequential surface cleaning procedure prior to epitaxial channel growth for heavily arsenic- and boron-doped Si surfaces improved the interface quality both for p- and n-TFETs. Simultaneously, the subthreshold swing (SS) values of the TFETs improved step-by-step with interface quality.

Effects of different surface cleaning procedures on the superficial morphology and the adhesive strength of epoxy coating on aluminium alloy 1050

Abstract This study reports the effects of different cleaning procedures on the surface characteristics of the aluminium alloy 1050 substrates and on the adhesive strength of the epoxy coating to this alloy's surface. The cleaning procedures used in this study were (1) degreasing by acetone, (2) alkaline etching by 5 w/w% NaOH solution and (3) alkaline etching by 5 w/w% NaOH solution followed by acid cleaning by 50 v/v% HNO 3 solution. The surface morphology, chemical composition and topography of the cleaned substrates were investigated by field-emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS) and atomic force microscope (AFM), respectively. The effectiveness of the cleaning procedures was also studied by polarization test and open circuit potential (OCP) measurements. The surface free energy and work of adhesion were obtained on the cleaned samples using contact angle measuring device. Pull-off test was conducted to evaluate the adhesion strength of the epoxy coating on the aluminium substrates. Results revealed that the surface cleaning of aluminium alloy by alkaline etching followed by acid cleaning method was the most efficient procedure for removing the oxide layer from the surface of aluminium compared to other cleaning procedures. The surface roughness, surface free energy, electrochemical activity and adhesion strength of the epoxy coating to the aluminium surface were significantly increased using this surface cleaning procedure.

Scaled ZrO2 dielectrics for In0.53Ga0.47As gate stacks with low interface trap densities

ZrO2 dielectrics were grown on n-In0.53Ga0.47As channels by atomic layer deposition, after employing an in-situ cyclic nitrogen plasma/trimethylaluminum surface cleaning procedure. By scaling the ZrO2 thickness, accumulation capacitance densities of 3.5 μF/cm2 at 1 MHz are achieved. The midgap interface trap density is estimated to be in the 1012 cm−2 eV−1 range. Using x-ray photoelectron spectroscopy, it was shown that the interface contained the oxides of In, Ga, and Al, but no As-oxides or As-As bonds within the detection limit. The results allow for insights into the effective passivation of these interfaces.

Influence of plasma-based in-situ surface cleaning procedures on HfO2/In0.53Ga0.47As gate stack properties

We report on the influence of variations in the process parameters of an in-situ surface cleaning procedure, consisting of alternating cycles of nitrogen plasma and trimethylaluminum dosing, on the interface trap density of highly scaled HfO2 gate dielectrics deposited on n-In0.53Ga0.47As by atomic layer deposition. We discuss the interface chemistry of stacks resulting from the pre-deposition exposure to nitrogen plasma/trimethylaluminum cycles. Measurements of interface trap densities, interface chemistry, and surface morphology show that variations in the cleaning process have a large effect on nucleation and surface coverage, which in turn are crucial for achieving low interface state densities.

Fluorescent nanodiamonds derived from HPHT with a size of less than 10 nm

The fabrication of fluorescent nanodiamonds by the electron irradiation of a high-pressure high-temperature microdiamond followed by annealing and fragmentation has a number of advantages over other fabrication approaches. High energy electron irradiation of micron-sized diamonds is a safe and convenient method to create vacancies within the lattice, thereby allowing for simple reactor designs. Well-defined annealing conditions facilitate vacancy migration and its subsequent capture by substitutional nitrogen (Ns) atoms, while avoiding the formation of unwanted coke on the surface of the diamond. In addition, microdiamonds offer a long vacancy migration path, which significantly increases the probability of vacancy trapping by nitrogen. In this report, we show that the fragmentation of irradiated and annealed microdiamonds creates round ultrasmall nanodiamonds composed of perfectly crystallized cubic-diamond nanocrystals, with fluorescent centers inside the nanocrystal core. Atomic force microscopy and confocal fluorescence microscopy demonstrate that approximately 30% of diamond nanocrystals with a size of less than 10nm are fluorescent and have a remarkably long spin decoherence time (2.7μs for a 7nm diamond nanocrystal). The presence of a high content of non-fluorescent ultrasmall nanodiamonds can be explained by the limited N concentration and its heterogeneous distribution in the initial raw high-pressure high-temperature diamond. The remarkably long spin decoherence time of the ultrasmall fluorescent nanodiamonds may be due to surface cleaning and nanodiamond fabrication procedures, which result in a low number of spin impurities in and around the nanocrystal.