Argon Plasma Etching Research Articles

Nanographene charge trapping memory with a large memory window

Nanographene is a promising alternative to metal nanoparticles or semiconductor nanocrystals for charge trapping memory. In general, a high density of nanographene is required in order to achieve high charge trapping capacity. Here, we demonstrate a strategy of fabrication for a high density of nanographene for charge trapping memory with a large memory window. The fabrication includes two steps: (1) direct growth of continuous nanographene film; and (2) isolation of the as-grown film into high-density nanographene by plasma etching. Compared with directly grown isolated nanographene islands, abundant defects and edges are formed in nanographene under argon or oxygen plasma etching, i.e. more isolated nanographene islands are obtained, which provides more charge trapping sites. As-fabricated nanographene charge trapping memory shows outstanding memory properties with a memory window as wide as ∼9 V at a relative low sweep voltage of ±8 V, program/erase speed of ∼1 ms and robust endurance of >1000 cycles. The high-density nanographene charge trapping memory provides an outstanding alternative for downscaling technology beyond the current flash memory.

Anisotropic multi-step etching for large-area fabrication of surface microstructures on stainless steel to control thermal radiation

Controlling the thermal radiation spectra of materials is one of the promising ways to advance energy system efficiency. It is well known that the thermal radiation spectrum can be controlled through the introduction of periodic surface microstructures. Herein, a method for the large-area fabrication of periodic microstructures based on multi-step wet etching is described. The method consists of three main steps, i.e., resist mask fabrication via photolithography, electrochemical wet etching, and side wall protection. Using this method, high-aspect micro-holes (0.82 aspect ratio) arrayed with hexagonal symmetry were fabricated on a stainless steel substrate. The conventional wet etching process method typically provides an aspect ratio of 0.3. The optical absorption peak attributed to the fabricated micro-hole array appeared at 0.8 μm, and the peak absorbance exceeded 0.8 for the micro-holes with a 0.82 aspect ratio. While argon plasma etching in a vacuum chamber was used in the present study for the formation of the protective layer, atmospheric plasma etching should be possible and will expand the applicability of this new method for the large-area fabrication of high-aspect materials.

Improving the sensitivity of a near-infrared nanocomposite photodetector by enhancing trap induced hole injection

We report the enhancement of the photoconductive gain of nanocomposite near-infrared photodetectors by a zinc oxide nanoparticles (ZnO NPs) rich surface at the nanocomposite/cathode interface. An argon plasma etching process was used to remove polymer at the surface of nanocomposite films, which resulted in a ZnO NPs rich surface. The other way is to spin-coat a thin layer of ZnO NPs onto the nanocomposite layer. The ZnO NPs rich surface, which acts as electron traps to induce secondary hole injection under reverse bias, increased hole injection, and thus the external quantum efficiency by 2–3 times. The darkcurrent declined one order of magnitude simultaneously as a result of etching the top nanocomposite layer. The specific detectivity at 800 nm was increased by 7.4 times to 1.11 × 1010 Jones due to the simultaneously suppressed noise and enhanced gain.

Self-formation of lead telluride nanostructures during argon plasma etching of single-crystal wafers

In this work we report a phenomenon of PbTe nano- and microstructure selfformation that takes place during dry etching of lead telluride (111)-oriented single-crystal wafers with 4 at.% excess tellurium in RF high-density low-pressure inductively coupled argon plasma. Using scanning electron microscopy and energy dispersive X-ray spectroscopy investigations it is established that during the plasma treatment high sputtering rates are accompanied by active redeposition processes on crystal surface and on the inner side of the Si etching mask resulting in a nanostructure arrays self-formation via vapour-liquid-solid mechanism.

Tailoring the surface morphology of zinc oxide films for high-performance micromorph solar cells

Self-textured zinc oxide polycrystalline films prepared by metalorganic low-pressure chemical vapor deposition combine excellent transparency, conductivity and light-scattering ability when used as electrodes for high-efficiency thin-film silicon solar cells. However, the growth of silicon layers with low defect density, which are necessary for high-performance solar cells, often requires the rough surface morphology of as-deposited zinc oxide films to be smoothened. This is usually achieved by a post-deposition argon plasma-etching treatment. We investigate here an alternative method to modify the surface morphology by changing the zinc oxide growth conditions over only the last hundreds of nanometers of the total film thickness. We discuss two types of zinc oxide cap layers, one grown with the addition of ethanol and the other with an enhanced diethylzinc (DEZ) precursor flow. We show that the presence of either type of cap layer does not alter the layer׳s electrical properties, but does slightly diminish the layer׳s light-scattering ability. The cap layer grown with ethanol leads to a more pronounced leveling of the film texture, while the high-DEZ-grown layer better preserves the sharp features of the underlying ZnO. Finally, zinc oxide films with cap layer are used as front electrodes for tandem amorphous/microcrystalline silicon solar cells, and are compared to rough films treated with an argon plasma. With rising thickness of the capping layers, the efficiency of tandem cells increases reaching values over 12%, and approaches that of cells on Ar plasma treated ZnO films.

Plasma synthesis of hexagonal-pyramidal graphite hillocks

We report on the synthesis and natural occurrence of hexagonal-pyramidal graphite hillocks on graphite crystal substrates. Synthetic hillocks were obtained from flexible graphite sheets and highly oriented pyrolytic graphite via argon plasma etching in a standard helicon configuration reactor. High-resolution transmission electron microscopy and electron diffraction suggest these hillocks have a high degree of perfection. Their size distribution ranges from 50 to 800nm across and up to 1μm along the c-axis. As a reference, natural crystals from Tanzania exhibiting the same morphology are presented. Also, a formation mechanism of the plasma-synthesized structures by an etching process is detailed. This new type of vertically aligned carbon nano- and microstructures presents a peculiar geometry including nano-arches at the graphite edge planes which induce a strong resistance to the plasma etching.

Effect of bio-mediated route synthesized silver nanoparticles for modification of polyethersulfone membranes

This article reports the modification of polyethersulfone (PES) membrane using silver nanoparticles (n-Ag), their characterizations and protein separation performances. As a bio-mediated synthesis route, gram-positive Bacillus subtilis bacterial supernatants were employed for preparing n-Ag. The resulting n-Ag exhibited uniform and well defined spherical morphology with size less than 50nm. The effect of the incorporation of n-Ag on PES membrane in terms of cross sectional morphology, surface roughness, crystallinity and hydrophilicity were investigated systematically. XPS analysis showed that a significant portion of silver was in silver oxide form. Depth profiling by argon plasma etching and XPS showed the partition of Ag2O and Ag between the membrane surface and the bulk. A minor oxidation on the surface of the silver was observed whereas the internal structure of the membrane retained Ag in its metallic state. The potential of the nano composite membrane for the separation of BSA with varying feed concentration and transmembrane pressure were performed. At 1.5wt% loading of n-Ag in neat PES, enhancement in bovine serum albumin (BSA) flux and decrease in the rejection were observed. The results and performance of the PES/n-Ag nanocomposite membranes indicate that it would be a deserving candidate for future industrial separations. The experimental results confirm that the incorporation of Ag nanoparticles in PES UF membrane can increase hydrophilicity and reduce the fouling.

Influence of plasmochemical modification of Al–Cu–Mg alloys on surface structure and functional properties

The article presents the results of the study of the composition and selected functional properties of Al–Cu–Mg alloys modified by RF CVD technique (Radio-Frequency Chemical Vapor Deposition). The type and composition of the deposited SiNH and carbon doped SiNH layers was altered in the experiments. The samples were pre-treated with argon plasma etching and N+ ion implantation.On the basis of the experimental evidence it is concluded that the deposition of an anti-wear SiCNH coating (using SiH4:CH4:N2 = 1:1:2 gas mixture) improves both the investigated mechanical properties (hardness ca. 10 GPa, Young modulus ca. 95 GPa) and tribological performance of the control (unmodified) alloy sample as well as those of the modified alloy samples whose outer layer is SiNH.

Argon plasma treatment on metal substrates and effects on diamond‐like carbon (DLC) coating properties

The diamond like carbon coatings (DLC) of 400 nm thickness was deposited by filtered cathodic vacuum arc system. The argon plasma etched and non‐etched tungsten carbide‐cobalt (WC‐Co) and stainless steel (SUS) were used as substrates. The chromium was deposited as an interlayer for diamond like carbon coatings on the etched and non‐etched WC‐Co and SUS substrates. The present research is to evaluate the effect of argon plasma etching of the substrates on microstructure, tribology and adhesion strength of DLC coatings. The films were characterized by field emission scanning electron microscopy, Raman spectroscopy, tribology and scratch tests. The Raman studies showed the broad peak ∼1550 cm−1 indicates the formation of amorphous carbon or diamond‐like carbon. It was found that the DLC coatings on the plasma etched substrates of WC‐Co and SUS have shown the low friction coefficient of ∼0.12–0.14. The DLC coatings on plasma etched substrates of WC‐Co have better adhesion strength. The results showed that the argon plasma etching of substrate reduces the surface roughness to ∼2.5 nm, resulting in smooth morphology, good adhesion and wear resistance as compared to DLC coating on non‐etched substrates. The scanning electron microscopic studies showed that the DLC coated specimens with plasma etched substrates have minimum damage as compared to the DLC coated non etched substrates.

Enhanced Electrical Stability of LP-MOCVD-Deposited ZnO:B Layers by Means of Plasma Etching Treatment

Electrical properties of transparent conductive ZnO:B films, obtained by the low-pressure metal organic chemical vapor deposition (LP-MOCVD) technique, were monitored during the given time, and a heavy worsening of these properties was observed. At the same time, other ZnO:B samples subjected to a post-deposition treatment by argon plasma etching showed an appreciable enhancement of the electrical stability in the given time. A degradation mechanism, involving formation of O– adsorbate and its diffusion inside the grain boundary, is proposed as responsible of the carrier mobility worsening. Furthermore, the beneficial effect of the plasma treatment is explained in terms of a rearrangement of the grain boundary with a decrease of positively charged defect density and, consequently, a slowing down of O– formation rate. Finally, argon plasma post-deposition treatment is proposed as an effective process for obtaining ZnO:B films with an appreciable electrical stability in the given time.

AFM and Raman studies of topological insulator materials subject to argon plasma etching

Plasma etching is an important tool in nano-device fabrication. We report a study on argon plasma etching of topological insulator materials Bi2Se3, Bi2Te3, Sb2Te3 and Bi2Te2Se using exfoliated flakes (with starting thicknesses of ∼100 nm) derived from bulk crystals. We present data mainly from atomic force microscopy (AFM) and Raman spectroscopy. Through AFM measurements, plasma exposure is observed to decrease the thickness of our samples and increase surface roughness (with height fluctuations reaching as large as ∼20 nm). We extract an etching rate for each type of material. Plasma exposure also causes a widening (especially ) of the characteristic Raman peaks, with no significant change in peak position. The overall Raman intensity is observed to initially increase then decrease sharply after the samples are etched below ∼20 nm in thickness. Our findings are valuable for understanding the effects of argon plasma etching on topological insulator materials.

Chemical vapor deposition of amorphous silicon carbide thin films on metal surfaces using monomethylsilane gas at low temperatures

The low temperature chemical vapor deposition process of depositing silicon carbide on a metal surface, such as aluminum and stainless steel, was developed using monomethylsilane gas. In order to prepare the reactive substrate surface, two alternative methods were separately used. The first was the formation of a silicon interlayer containing silicon dimers. The other method was the argon plasma etching for producing dangling bonds. After the reactive surface preparation, the silicon carbide thin film was formed at room temperature using monomethylsilane gas. Because the silicon–carbon bond remained after the deposition, the silicon carbide coating technology is expected to be applicable for various metals.

Anti-Reflective Structure of PMMA/Glass Fiber Membrane Produce by Argon Plasma Etching and Variation of Transmitted Intensity

The aim of this research is to increase the membrane’s transmitted intensities; it used Argon plasma etching to process the anti-reflective structure on PMMA/glass fiber membrane surface. The anti-reflective structure could increase the light transmission at the identical specification of membrane’s basic cloth. Membrane’s transmitted intensities can directly affect it products competitiveness. The parameter of experimentation set with distance between sample and RF plate are 19 or 5.5 centimeters, plasma output power is 270, 240, 210 Watt respectively, each process time is 6, 12, 18, 24, 30 seconds. In this stage, the best transmitted intensity of parameter is 19cm, 210W, 30sec; it increased 2.4 % than non-treatment sample. The summary of this study, decreased plasma output power would reduce the impact extent of plasma gas but uniformity of structure should increase. Decreased the distance between sample and RF plate can avoided the degeneration of energy, reinforced the problem of insufficient etching and reduced the turbulence.

Depth Profile Characterization of Spin-Coated Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonic acid) Films for Thin-Film Solar Cells during Argon Plasma Etching by Spectroscopic Ellipsometry

Depth profiles of the optical constants, carrier mobility, and carrier density of spin-coated poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) films were investigated by real-time characterization by spectroscopic ellipsometry (SE) during argon plasma etching at atmospheric pressure. Spectral analysis revealed that homogeneous etching occurred within 10–15 nm of the top surface, followed by the appearance of a conductive PEDOT phase and surface roughening, which originated from the depth profile of the PEDOT-to-PSS molar concentration ratio. The use of the plasma-etched PEDOT:PSS layer relatively improved the performance of the cupper phthalocyanine (CuPc)/C60 organic thin-films solar cells as a hole-transport layer with higher optical transmittance by adjusting the plasma etching condition.

Depth Profile Characterization of Spin-Coated Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonic acid) Films for Thin-Film Solar Cells during Argon Plasma Etching by Spectroscopic Ellipsometry

Depth Profile Characterization of Spin-Coated Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonic acid) Films for Thin-Film Solar Cells during Argon Plasma Etching by Spectroscopic Ellipsometry

Depth profile characterization of spin‐coated poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonic acid) (PEDOT:PSS) films by spectroscopic ellipsometry

AbstractDepth profiles of the optical constants, carrier mobility, and carrier density of spin‐coated poly(3,4‐ethylene‐dioxythiophene):(polystyrene sulfonic acid) (PEDOT:PSS) films were investigated by real‐time spectroscopic ellipsometry (SE) characterization during argon plasma etching at atmospheric pressure. Spectra analysis revealed that homogeneous etching occurred within 10‐20 nm of the top surface, followed by the appearance of conductive PEDOT phase with a surface roughening. These findings originated from the depth profile of the PEDOT‐to‐PSS molar concentration ratio. The use of a 10‐20‐nm etched PEDOT:PSS layer improved relatively the performance of a hole‐transport layer for CuPc/C60 organic thin‐films solar cells with higher optical transmittance (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Atmospheric-pressure argon plasma etching of spin-coated 3,4-polyethylenedioxythiophene:polystyrenesulfonic acid (PEDOT:PSS) films for cupper phtalocyanine (CuPc)/C 60 heterojunction thin-film solar cells

Depth profiles of the optical constants, carrier mobility, and carrier density of spin-coated 3,4-polyethylenedioxythiophene:polystyrenesulfonic acid (PEDOT:PSS) films were investigated by real-time characterization by the spectroscopic ellipsometry (SE) during argon plasma etching at atmospheric pressure. Spectral analysis revealed that homogeneous etching occurred within 10–15 nm of the top surface, followed by the appearance of a conductive PEDOT phase and surface roughning, which originated from the depth profile of the PEDOT-to-PSS molar concentration ratio. The use of the plasma-etched PEDOT:PSS layer improved relatively the performance of the copper phtalocyanine (CuPc)/C 60 organic thin-films solar cells as a hole-transport layer with higher optical transmittance by adjusting the plasma etching condition.

Laser desorption ionization mass spectrometry on silicon nanowell arrays.

This paper describes a new technique for fabrication of nanostructured porous silicon (pSi) for laser desorption ionization mass spectrometry. Porous silicon nanowell arrays were prepared by argon plasma etching through an alumina mask. Porous silicon prepared in this way proved to be an excellent substrate for desorption/ionization on silicon (DIOS) mass spectrometry (MS) using adenosine, Pro-Leu-Gly tripeptide, and [Des-Arg(9)]-bradykinin as the model compounds. It also allows the analyses of complex biological samples such as a tryptic digest of bovine serum albumin and a carnitine standard mixture. Nanowell array surfaces were also used for direct quantification of the illicit drug fentanyl in red blood cell extracts. This method also allows full control of the surface features. MS results suggested that the pore depth has a significant effect on the ion signals. Significant improvement in the ionization was observed by increasing the pore depth from 10 to 50 nm. These substrates are useful for laser desorption ionization in both the atmospheric pressure and vacuum regimes.

Thin film thermocouples for in situ membrane electrode assembly temperature measurements in a polybenzimidazole-based high temperature proton exchange membrane unit cell

This paper presents Type-T thin film thermocouples (TFTCs) fabricated on Kapton (polyimide) substrate for measuring the internal temperature of PBI (polybenzimidazole)-based high temperature proton exchange membrane fuel cell (HT-PEMFC). Magnetron sputtering technique was employed to deposit a 2 μm thick layer of TFTCs on 75 μm thick Kapton foil. The Kapton foil was treated with in situ argon plasma etching to improve the adhesion between TFTCs and the Kapton substrate. The TFTCs were covered with a 7 μm liquid Kapton layer using spin coating technique to protect them from environmental degradation. This Kapton foil with deposited TFTCs was used as sealing inside a PBI (polybenzimidazole)-based single cell test rig, which enabled measurements of in situ temperature variations of the working fuel cell MEA. The performance of the TFTCs was promising with minimal interference to the operation of the fuel cell.

Surface modification of carbon electrodes using an argon plasma

In this work, an activated carbon sheet was modified, to improve capacitance and energy density of electric double layer capacitors (EDLCs). Surfaces were treated with plasma for selected times of 1, 5, 10, 20, and 30 min. The plasma source was a DC glow discharge in argon gas. The pressure was 20 Pa and the distance between positive and negative electrodes was 20 mm. DC power was 70 W. The activated carbon sheets were set up so that the sheets were covered with the DC glow discharge. The results showed that plasma treatment led to roughening of the surface of the activated carbon sheets which became more pronounced for increased time. This was attributed to an increased surface area caused by argon plasma etching. For discharge times greater than 10 min, contamination from sputtered PTEE in the chamber appeared to have a smoothing effect and led to a reduction of the measured surface area. Capacitance of the EDLCs cells with the activated carbon sheets after 1 min plasma surface treatment was increased by 2% compared to EDLCs cells with the original activated carbon sheet. The results have shown that the modification by plasma treatment of activated carbon sheets is a suitable technique for EDLCs used in high current applications.