Increasing Etching Time Research Articles

Sensing behavior of CuO-doped ZnO/PS nanoparticles

In this work, nanograined ZnO films with various CuO contents (between 2at% and 10at%) were synthesized by pulsed-laser deposition method. The films with (2, 4, and 6at%) contain only ZnO peaks with wurtzite structure. The peaks at the CuO (with cubic lattice) become visible in the X-ray diffraction spectra at (8 and 10at%). Also, the X-ray diffraction patterns of porous silicon showed a broadening in the FHWM with increasing etching time. From atomic force microscopy of the prepared samples, a decrease in the average diameter of the particles with increasing etching time was observed. The photoluminescence spectroscopy showed that the blue shift was increased with etching time. We have studied the operation temperature of gas sensors fabricated from the prepared samples at different environment temperatures and found that the maximum sensitivity was about 75.88 for 10min porous silicon time.

Microstructural characterization of aluminum alloys using Weck's reagent, part II: Coloring mechanism

This paper is the second part of the study focusing on the color metallography using Weck's reagent for Al alloys. Following the first part of the study which demonstrated a wide application of Weck's reagent, this paper investigates the coloring mechanism of color etching with Weck's reagent in detail by various characterizations of the specimen surface after etching. The results show that after the Al specimen is etched with Weck's reagent, a thin film consisting of Mn oxide is formed on the surface with different morphologies and thicknesses from location to location, which causes different colors observed by optical microscopy correspondingly. Further investigations show that the film is characterized by a relatively smooth surface but a rough interface with the substrate. Such structure may cause interference of light reflected from different sites. The growth of film is strongly influenced by the solute micro-segregation in the Al phase. Film starts to form first on the area with higher solute (Ti) concentration. As the etching time increases, film also grows on other areas. 12s etching yields to the best color contrast because the difference in the film morphology and thickness is the most obvious at this time.

SF6/Ar plasma textured periodic glass surface morphologies with high transmittance and haze ratio of ITO:Zr films for amorphous silicon thin film solar cells

We report various SF6/Ar plasma textured periodic glass surface morphologies with high transmittance, haze ratio, and root mean square (rms) roughness of ITO:Zr films for amorphous silicon thin film solar cells (a-Si TFSCs). SF6/Ar plasma textured glass surface morphologies contain micro- and nano-textured features that help to scatter the light in visible and near infra-red (NIR) wavelength regions. We designed the textured glass surface morphologies with big square craters to smaller pyramids for various glass etching times from 30 to 75 min. Magnetron sputtered ITO:Zr (∼210 nm) films were deposited on textured glass surface morphologies and showed higher transmittance and haze ratio of 88.48% and 77.61%, respectively, in the visible-NIR (400–1100 nm) wavelength region. The sheet resistance and resistivity of ITO:Zr films decreased with the increase of etching time, due to high rms roughness and better step coverage. A passivation AZO (30 nm) layer was added to the ITO:Zr films, due to its better stability against hydrogen plasma exposure. The ITO:Zr/AZO films were employed as a front TCO layer and the current density–voltage (J–V) characteristics of a-Si TFSCs increased by light scattering effect, without any reduction in either the open circuit voltage (VOC) or the fill factor (FF). Relative to flat glass substrate, JSC and the efficiency of a-Si TFSCs were enhanced by 7.51% and 19.39%, respectively, for textured glass surface morphology.

Effects of high neutron doses and duration of the chemical etching on the optical properties of CR-39

Effects of the duration of chemical etching on the transmittance, absorbance and optical band gap width of the CR-39 (Polyallyl diglycol carbonate) detectors irradiated to high neutron doses (12.7, 22.1, 36.0 and 43.5Sv) were studied. The neutrons were produced by bombardment of a thick Be target with 12MeV protons of different fluences. The unirradiated and neutron-irradiated CR-39 detectors were subjected to a stepwise chemical etching at 1h intervals. After each step, the transmission spectra of the detectors were recorded in the range from 200 to 900nm, and the absorbances and optical band gap widths were determined. The effect of the etching on the light transmittance of unirradiated detectors was insignificant, whereas it was very significant in the case of the irradiated detectors. The dependence of the optical absorbance on the neutron dose is linear at short etching periods, but exponential at longer ones. The optical band gap narrows with increasing etching time. It is more significant for the irradiated dosimeters than for the unirradiated ones. The rate of the narrowing of the optical band gap with increasing neutron dose increases with increasing duration of the etching.

Fabrication of a novel quartz micromachined gyroscope

A novel quartz micromachined gyroscope is proposed in this paper. The novel gyroscope is realized by quartz anisotropic wet etching and 3-dimensional electrodes deposition. In the quartz wet etching process, the quality of Cr/Au mask films affecting the process are studied by experiment. An excellent mask film with 100 Å Cr and 2000 Å Au is achieved by optimization of experimental parameters. Crystal facets after etching seriously affect the following sidewall electrodes deposition process and the structure’s mechanical behaviours. Removal of crystal facets is successfully implemented by increasing etching time based on etching rate ratios between facets and crystal planes. In the electrodes deposition process, an aperture mask evaporation method is employed to prepare electrodes on 3-dimensional surfaces of the gyroscope structure. The alignments among the aperture masks are realized by the ABM™ Mask Aligner System. Based on the processes described above, a z–axis quartz gyroscope is fabricated successfully.

Surface micro-structuring of zirconia dental implants.

Sandblasting with subsequent acid etching is a potential procedure to generate microstructured surfaces on zirconia implants. The aim of the study was to systematically analyze the effect of these process steps on surface morphology and mechanical strength of the implants. Zirconia implant blanks (ceramic.implant, VITA) were sandblasted (105-μm alumina, 6bar), subsequently HF-etched, and finally heat-treated at 1250°C. Surface topographies were documented by SEM. Surface roughness Ra (n=4), monoclinic volume fraction in the surface layer (n=1), and static fracture load (n=4) were measured. Surface roughness Ra reached a maximum of 1.2μm after 4× sandblasting. Scratches and sharp edges dominated the surface aspect. Fracture load increased with the number of sandblasting cycles with a gain of 30% after 20 cycles. HF etching did not change the Ra values, but sharp edges were rounded and small pits created. A minor decrease in fracture load with increasing etching time was observed. Heat treatment of 1h reduced the fracture load by 1/3. Longer heat treatment had no further effect. The roughness Ra was not modified by heat treatment. Fracture load was strongly correlated with the monoclinic fraction except for the results obtained directly after acid etching, where a constant monoclinic fraction was observed. Sandblasting with 105-μm alumina followed by 1h HF etching at room temperature and 1h heat treatment at 1250°C is a reliable and tolerant process to create a surface roughness of about Ra =1.2μm on zirconia implants.

Electroplating Dysprosium from IL-Based Solutions: A Promising Electrochemical Step to Produce Stronger High Performance Nd(Dy)-Fe-B Sintered Magnets

An electrodeposition replacement to the commonly used physical vapor deposition methods used in enhancing the coercivity of Nd-Fe-B sintered magnets has been proposed. Dysprosium was galvanostatically electroplated on Nd-Fe-B sintered magnets that were previously electrochemically coated with copper. Electroplated dysprosium films were characterized by X-ray photoelectron spectroscopy, depth profiling, scanning electron micrographs, and energy dispersive X-ray spectroscopy. XPS analysis after argon ion sputtering indicates that minor impurities are only superficial as their atomic fractions in the sample nearly disappear with increasing etching time. The electrochemistry of synthesized dysprosium bis(trifluromethylsulfonyl)imide dissolved in the air- and water-stable ionic liquid 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsuflonyl)imide was studied by cyclic voltammetry. Electroplating of metallic dysprosium was followed by a heat-treatment above the melting temperature of the Nd-rich phases of the sintered magnet base body whose magnetic characterization was performed in a hysteresis loop tracer for hard magnetic materials.

Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method.

In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films.

Fabrication of Aluminum Superhydrophobic Surface with Facile Chemical Etching Method

Superhydrophobic surfaces have attracted much interest for its potential applications. In this study, the superhydrophobic aluminum surfaces were fabricated by method of chemical etching. Aluminum surfaces were firstly chemically etched by hydrochloric acid, and modified with stearic acid. The relationship between the etching time and the surface hydrophobicity was investigated. The contact angle and the sliding angle were tested, the results showed that with increasing etching time, the contact angle experienced a rise and then decrease, while the sliding angle dropped first and then started to climb. A maximum value of 152 degrees for the contact angle and a minimum value of 3 degrees for the sliding angle were obtained with etching time of 1 minute. The results indicated an ideal superhydrophobic property of the aluminum surfaces.

산부식 시간과 도포 횟수에 따른 불화 카제인포스포펩타이드-아모르포우스칼슘포스페이트의 치아 법랑질 재광화 효과

본 연구는 카제인포스포펩타이드-아모르포우스칼슘포스포페이트(CPP-ACP)에 불소이온을 결합시킨 불화 카제인포스포펩타이드-아모르포우스칼슘포스페이트(CPP-ACFP)제제의 법랑질 재광화 정도를 알아보기 위한 실험으로 법랑질 표면에 산부식 시간을 달리한 후 CPP-ACFP제제를 같은 횟수로 도포했을 때의 재광화 정도와 CPP-ACFP제제의 도포 횟수가 법랑질의 재광화에 미치는 영향을 알아보고자 건전한 치아 64개를 대상으로 미세경도측정, 주사전자현미경 관찰 실험을 하였다. 그 결과 산부식 시간이 길어질수록, CPP-ACFP제제의 도포 횟수를 증가시킬수록 법랑질의 재광화가 더 잘 일어나는 것을 관찰할 수 있었다. 그러므로 CPP-ACP에 불소이온을 결합시켜 치아에 무기질 공급과 불소도포를 한 번에 할 수 있는 CPP-ACFP제제는 법랑질 재광화 물질로 권장할 만하다고 하겠다. 【This study examined the remineralization effect of CPP-ACFP according to the etching time and the frequency of application. A CPP-ACFP paste was formed from a combination of CPP-ACP paste and fluorine. The remineralization effect of CPP-ACFP was measured according to the etching time and the frequency of applications of CPP-ACFP. The microhardness of 64 teeth was measured as the sound sample and observed by scanning electron microscopy. As a result, the effect on remineralization of the enamel increased with increasing etching time and frequency of application. Therefore, a CPP-ACP paste combination to fluorine in the tooth mineral CPP-ACFP paste fluoride application can be supplied with the material-advisable enamel remineralization.】

Damage characteristics of n-GaN thin film surfaces etched by ultraviolet light-assisted helium plasmas

Damage characteristics of n-GaN thin film surfaces etched by ultraviolet (UV) light-assisted He plasmas at various gas pressures have been investigated from the viewpoint of the UV light irradiation effect. During the plasma etching, the surface is additionally irradiated with UV light emitted from a black light lamp. The peak wavelength of the emitted UV light corresponds to that of the GaN band-gap energy. The result is compared with that obtained only by use of He plasma. A morphological change in the surface etched by the UV light-assisted He plasma depends on gas pressure, whereas the He plasma only does not cause the morphological change in the surface regardless of gas pressure. The additional UV light irradiation causes a morphological change in the surface etched for a long time of more than 60min at high gas pressures between 6.7 and 13Pa. The morphology of the surface etched at a low gas pressure of 1.3Pa does not change from that of the as-grown surface even with increasing etching time. The additional UV light irradiation also enhances the etch depth and suppresses a decrease in N/Ga ratio at the surface compared with that obtained only by use of the He plasma.

Effect of etching time and resin bond on the flexural strength of IPS e.max Press glass ceramic

ObjectiveTo evaluate the effect of hydrofluoric acid (HFA) etching time and resin cement bond on the flexural strength of IPS e.max® Press glass ceramic. MethodsTwo hundred and ten bars, 25mm×3mm×2mm, were made from IPS e.max® Press ingots through lost-wax, hot-pressed ceramic fabrication technology and randomly divided into five groups with forty-two per group after polishing. The ceramic surfaces of different groups were etched by 9.5% hydrofluoric acid gel for 0, 20, 40, 60 and 120s respectively. Two specimens of each group were selected randomly to examine the surface roughness and 3-dimensional topography with atomic force microscope (AFM), and microstructure was analyzed by the field emission scanning electron microscope (FE-SEM). Then each group were subdivided into two subgroups (n=20). One subgroup of this material was selected to receive a thin (approximately 0.1mm) layer of resin luting agent (Variolink N) whereas the other subgroup remained unaltered. Half of subgroup's specimens were thermocycled 10,000 times before a 3-point bending test in order to determine the flexural strength. Interface between resin cement and ceramic was examined with field emission scanning electronic microscope. ResultsRoughness values increased with increasing etching time. The mean flexural strength values of group 0s, 20s, 40s, 60s and 120s were 384±33, 347±43, 330±53, 327±67 and 317±41MPa respectively. Increasing HF etching times reduced the mean flexural strength (p<0.05). However, the mean flexural strength of each group, except group 0s, increased significantly to 420±31, 435±50, 400±39 and 412±58MPa after the application of dual-curing resin cement. In the present investigation, no significant differences after thermocycling on the flexural strengths were evident. SignificanceOvertime HF etching could have a wakening effect on IPS e.max® Press glass ceramic, but resin cement bonding to appropriately etched surface would strengthen the dental ceramic.

Large-area nanopatterned graphene for ultrasensitive gas sensing

Chemical vapor deposited (CVD) graphene is nanopatterned using a spherical block copolymer etch mask. The use of spherical rather than cylindrical block copolymers allows homogeneous patterning of cm-scale areas without any substrate surface treatment. Raman spectroscopy was used to study the controlled generation of point defects in the graphene lattice with increasing etching time, confirming that alongside the nanomesh patterning, the nanopatterned CVD graphene presents a high defect density between the mesh holes. The nanopatterned samples showed sensitivities for NO2 of more than one order of magnitude higher than for non-patterned graphene. NO2 concentrations as low as 300 ppt were detected with an ultimate detection limit of tens of ppt. This is the smallest value reported so far for non-UV illuminated graphene chemiresistive NO2 gas sensors. The dramatic improvement in the gas sensitivity is believed to be due to the high adsorption site density, thanks to the combination of edge sites and point defect sites. This work opens the possibility of large area fabrication of nanopatterned graphene with extremely high densities of adsorption sites for sensing applications.

Study on the Surface Morphologies of Nickel-Phosphorus Ultra-Black Films

Ni-P ultra-black films having conical pores with the diameter of ~ 10-30 μm and the depth of ~ 15-30 μm were prepared by chemical etching of electroless plated Ni-P films using 8 mol/L nitric acid at 40 °C for 60 s. The phase composition and microstructure of the film samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the diameter and depth of the etching pores become larger and the flat top regions bounded by etching pores become smaller by the coalescence of adjacent pores with the increase of etching time. The surface morphologies of the etched Ni-P films are characterized by the distribution of conical pores.

Plasma-etched nanoporous TiO2 using Ag nanoparticle masks: application for photoanodes of dye-sensitized solar cells

We investigate dye-sensitized solar cells (DSSCs) with nanoporous TiO2 photoanodes etched by inductively coupled plasmas (ICPs). Thermally Shrunk Ag nanoparticles are used as the etching masks during the ICP etching procedure. The efficiency of the assembled DSSC increases first and then decreases as the ICP etching time increases. The enhancement of light trapping/scattering is observed after ICP etching with Ag nanoparticle masks, however, over-etching may mitigate the effect. Interfacial charge transfer impedance of TiO2/dye/electrolyte also decreases first and then increases as the etching time increases, a trend highly correlated to the variation of the cell efficiency. Our experimental results indicate that the enhancement of light trapping (which leads to the increase of photocurrent), increase of open circuit voltage and reduction of charge transport resistance lead to the improvement of cell efficiency. The optimized etching time is around 30 s to 1 min. In comparison to the counterpart experiment, the DSSC with TiO2 photoanode etched by ICP without Ag nanoparticle shadow masks, the cell reveals monotonic decreases of photocurrent level, open circuit voltage, and efficiency with the ICP etching time.

Comparison of Physicochemical Surface Conditioning Methods for Adhesion of bis-GMA Resin Cement to Particulate Filler Composite and Surface Characterization

This study compared the effect of physicochemical surface conditioning methods on the adhesion of bis-GMA-based resin cement to particulate filler composite (PFC) used for indirect dental restorations. PFC blocks (N block = 54, n block = 9 per group) were polymerized and randomly subjected to one of the following surface conditioning methods: a) No conditioning (Control-C), b) Hydrofluoric acid (HF)etching for 60 s (AE60), c) HF for 90 s (AE90), d) HF for 120 s (AE120), e) HF for 180 s (AE180), and f) air-abrasion with 30 µm silica-coated alumina particles (AB). The conditioned surfaces were silanized with an MPS silane, and an adhesive resin was applied. Resin composite blocks were bonded to PFC using resin cement and photo-polymerized. PFC–cement–resin composite blocks were cut under coolant water to obtain bar specimens (1 mm × 0.8 mm). Microtensile bond strength test (μTBS)was performed in a universal testing machine (1 mm/min). After debonding, failure modes were classified using stereomicroscopy. Surface characterization was performed on a set of separate specimen surfaces using Scanning Electron Microscopy (SEM), X-Ray Dispersive Spectroscopy (XDS), X-Ray Photoelectron Spectroscopy (XPS), and Fourier Transform-Raman Spectroscopy (FT-RS). Mean μTBS (MPa) of C (35.6 ± 4.9) was significantly lower than those of other groups (40.2 ± 5.6–47.4 ± 6.1) (p < 0.05). The highest μTBS was obtained in Group AB (47.4 ± 6.1). Prolonged duration of HF etching increased the results (AE180: 41.9 ± 7), but was not significantly different than that of AB (p > 0.05). Failure types were predominantly cohesive in PFC (34 out of 54) followed by cohesive failure in the cement (16 out of 54). Degree of conversion (DC) of the PFC was 63 ± 10%. SEM analysis showed increased irregularities on PFC surfaces with the increased etching time. Chemical surface analyses with XPS and FT-RS indicated 11–70% silane on the PFC surfaces that contributed to improved bond strength compared to Group C that presented 5% silane, which seemed to be a threshold. Group AB displayed 83% SiO2 and 17% silane on the surfaces.

Evaluation of alkaline pre-treatment of PLLA fibers for biomimetic hydroxyapatite coating

A poly(l-lactic acid) (PLLA) and hydroxyapatite (HA) composite was formed via a biomimetic coating process. Before treatment in a modified-simulated body fluid (m-SBF), the surfaces of the PLLA fibers were etched with alkaline reagents to make the polymer surface easier for apatite to nucleate and grow. Several elements of this etching procedure (including the etching reagent, concentration, and length of pre-treatment) were varied to determine the optimal combination for producing a predictable HA coating with the desired properties of consistent coating distribution and thickness. The alkaline etching reagents used in this study were sodium hydroxide (NaOH), sodium hypochlorite (NaOCl), calcium hydroxide (Ca(OH)2), and calcium hypochlorite (Ca(OCl)2). The weight gained through m-SBF coating, changes in the mechanical properties of the PLLA, and HA coating morphology were observed to determine the effects of different pre-treatment strategies on the biomimetic coating process. It was confirmed that the most effective etching reagents are Ca(OH)2 and Ca(OCl)2. It was also found that decreased etching reagent concentration leads to a decrease in HA coating and increased etching time increases HA deposition.

Evolution of the crystallographic planes of cone-shaped patterned sapphire substrate treated by wet etching

A series of wet etching experiments were performed to investigate the evolution of crystallographic planes of cone-shaped patterned sapphire substrate. During the etching process, three kinds of etching zones were found. Two etching zones appeared first and vanished with increasing etching time. The other one exposed later and expanded gradually. Finally, the cone-shaped pattern with an arcuate slope transformed to a hexagonal pyramid. The calculated orientation of the crystallographic planes in the two etching zones was {1 1¯ 0 3} and {4 3¯1¯ 27}, which were different from the previous reports.

Preparation of antireflective superhydrophobic glass surfaces via etching method

A highly transparent superhydrophobic glass surface was successfully prepared through simple hydrothermal alkaline etching followed by modification with 1H, 1H, 2H, 2H-perfluorooctyl-triethoxysilane(POTS). The effects of etching temperature and etching time were investigated on the wettability and transmittance of etched glass substrates. The results showed that the glass surface hydrophobicity is enhanced as the etching time or etching temperature increases; the transmittance of the samples first increases and then decreases as the etching temperature is elevated or the etching time increases. Besides, the effects of glass surface microstructures on their wettability and transparency were analyzed and discussed. In an optimized case, a glass surface was obtained with a water contact angle of 152°, a sliding angle of less than 4° and the maximum transmission rate of 98.1%(537 nm).

Damage characteristics of n‐GaN thin film surfaces etched by N2 plasmas

AbstractDamage characteristics of n‐GaN surfaces etched by capacitively‐coupled radio frequency N2 plasma, generated with a high applied voltage of 400 V, was studied in terms of synergistic effect between ion bombardment and ultraviolet (UV) light irradiation. The result was compared with that obtained with a low applied voltage of 200 V. Morphology of the surface etched at a low gas pressure of 10 mTorr is similar to that of the as‐grown surface even with increasing etching time, whereas N/Ga ratio at the surface decreases. The result can be explained in terms of the physical etching, though the surface is irradiated with the UV light emitted from the plasma. The result obtained at the low gas pressure is independent of the applied voltage. In contrast, the characteristic at the surface etched at a high gas pressure of 50‐100 mTorr depends on the applied voltage. A morphological change in the surface etched with the high applied voltage occurs, whereas the N/Ga ratio increases The increase in the N/Ga ratio is not reproduced by the simulation, which implies the contribution of the UV light irradiation. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)