Do I Glow Discharge More or Less With Continuous Carbon

Volume 1

Zhong Li , Khiam Aik Khor , in Encyclopedia of Biomedical Engineering, 2019

Glow discharge plasma

Glow discharge plasma is formed when the voltage applied on a low-pressure gas exceeds its breakdown voltage and causes its ionization. The workpiece immersed in glow discharge plasma is bombarded by electrons and ions, leading to rearrangement and sputtering of the surface atoms. The two main glow discharge plasma sources are magnetron discharge and radio-frequency (RF) discharge. Glow discharge plasma is frequently used to remove surface contamination and increase surface energy of biomaterials. It has also been used to generate nitride, carbonitride, and oxynitride coatings on Ti alloys ( Sobiecki et al., 2001).

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ATOMIC EMISSION SPECTROMETRY | Principles and Instrumentation

R.M. Twyman , in Encyclopedia of Analytical Science (Second Edition), 2005

Glow Discharge Sources

Glow discharge is based on a phenomenon called sputtering, where atoms ejected from the surface of the analyte by high-energy argon atoms and ions achieve the excited state in the resulting plasma. A copper tube filled with argon is juxtaposed with the sample and a potential difference applied across the gap, with either a direct current or a RF alternating current. Electrons jump from the negatively charged sample toward the positively charged copper electrode and collide with argon atoms, creating positively charged argon ions that are attracted toward the sample surface. En route, they collide with other argon atoms and ions, and then strike the analyte surface with sufficient energy to displace electrons and atoms from the sample (sputtering). These analyte atoms also collide with the electrons and high-energy argon atoms/ions, causing them to be excited to higher energy states. As they deexcite, they emit photons resulting in a 'glow' extending 2–3  mm from the sample (Figure 5).

Figure 5. Principle of glow discharge atomic emission spectrometry. D=diameter of the anode and d=distance from anode to sample.

Glow discharge sources are based on three principal designs. The Grimm source, which consists of a copper cathode block in direct contact with the metal sample, is used with DC voltage. The Renault source is based on the Grimm source, but utilizes a ceramic cathode block that allows the use of RF voltages. The most recent development is the Marcus source, which also operates in RF mode. It has a ceramic cathode block and a very short anode tube to facilitate rapid plasma expansion. Although DC and RF plasmas are similar, RF plasmas are more stable and show a greater sputtering depth. The most important difference is that RF glow discharges can be used to analyze both conducting and nonconducting analytes, while DC glow discharges are restricted to conductors.

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Glow Discharge Mass Spectrometry

C. Derrick QuarlesJr, ... R. Kenneth Marcus , in Encyclopedia of Spectroscopy and Spectrometry (Third Edition), 2017

Introduction

Glow discharge (GD) plasmas have been applied as ionization sources for mass spectrometry (MS) analysis for over 80 years. In fact, during the first two decades of the twentieth century, gas discharges were used as ion sources for first-generation mass spectrographs. In 1971 Coburn and Kay demonstrated the use of GD sources for the first time for the analysis of solids by MS, and in 1974 Harrison and Magee pioneered the development of what is considered modern analytical GDMS (glow discharge mass spectrometry). Approximately 10 years later, the first GDMS became commercially available as the VG 9000 (formerly VG Elemental), and the application of GDMS successfully evolved for the ultratrace elemental analysis of solids. It is estimated that over 100 of these instruments are still in service for this exact application.

GD devices are (mainly) low-pressure plasmas that generate atoms, ions, electrons, and photons when the application of voltage between two electrodes causes molecular breakdown of the gas medium. The ions in the GD maintain the plasma, but also allow for its use as an ionization source for MS analysis. GDs are versatile sources that can be used for sample atomization and ionization. Over the past 40 years, GDMS has been recognized as an analytical technique of choice for ultratrace element analysis in solid metal alloys and semiconductors. More recently, the capacity for the analysis of solution and gaseous phase samples has also been developed.

In MS analysis, the ions present in the discharge plasma are transported from the source area through a small orifice into an adjacent chamber that has a lower pressure that is adequate for the particular mass analyzer (Figure 1). Ions originated in the discharge plasma are sorted according to their mass-to-charge ratio (m/z), resulting in a mass spectrum that represents the composition of the sample of interest, which in all cases is the cathode electrode. The resulting spectrum provides isotopic abundance information, hence allowing the use of techniques such as isotope dilution. In GDMS studies, argon is the most common discharge gas used, and the typical discharge voltage and gas pressure are 1   kV and 1   Torr, respectively.

Figure 1. General schematic diagram of a GD source coupled to a mass spectrometer.

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Three-Dimensional Electron Microscopy

Valentina Baena , ... Mark Terasaki , in Methods in Cell Biology, 2019

3.5 Glow discharge

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Glow discharge system, PELCO easiGlow glow discharge unit (91000, Ted Pella, Inc., Redding, CA).

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Rotary pump for glow discharge unit (92081, RVP 200-7, Ted Pella, Inc., Redding, CA). Although the Glow discharge system has a suggested pump, we found that it was not powerful enough for the custom-built chamber used for glow discharge of tape.

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Dynamic O-Ring Shaft Seal (2) (FMH-25A, ¼″ aluminum, Kurt J. Lesker Co., Jefferson Hills, PA). For rotating the tape reels.

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Plexi Glass (2) 12   ×   6, (2) 3.5   ×   6, (2) 3.5   ×   11. (Chemcast GP Acrylic Sheet, 0.5″ clear, Tap Plastics, San Leandro, CA).

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Plexiglas adhesive (Weld-On 4 Cement, 4oz, Tap Plastics, San Leandro, CA).

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Plexiglas adhesive applicator (SY20-65, Syringe Hypodermic Applicator, 18 gage, Tap Plastics, San Leandro, CA).

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Motor for automatic turning (ROB-09238, Stepper motor with cable, Sparkfun, Niwot, CO).

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Stepper motor driver (ROB-12779, EasiDriver, Sparkfun, Niwot, CO).

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Arduino board for motor (DEV-11021, Arduino Uno—R3, Sparkfun, Niwot, CO).

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Glow Discharge Mass Spectrometry, Methods

Annemie Bogaerts , in Encyclopedia of Spectroscopy and Spectrometry, 1999

Principle of the glow discharge and its use for mass spectrometry

A glow discharge is a kind of plasma, i.e. a partially ionized gas, consisting of positive ions and electrons, and a large number of neutral atoms. It is formed when a cell, consisting of an anode and a cathode, is filled with a gas at low pressure (e.g. 1 torr; 1 TORR = 133.3 Pa). In glow discharges used for mass spectrometry, argon is most frequently used as the filling gas. A potential difference (of the order of 1 kV) is applied between the two electrodes, and creates gas breakdown (i.e. the splitting of the gas into positive ions and electrons). The ions are accelerated towards the cathode and cause the emission of electrons upon bombardment at the cathode. The electrons arrive in the plasma, and give rise to excitation and ionization collisions with the argon gas atoms. The excitation collisions (and the subsequent decay, with emission of light) are responsible for the characteristic name of the 'glow' discharge. The ionization collisions create new ion–electron pairs. The ions are again accelerated towards the cathode, giving rise to new electrons. The electrons can again produce ionization collisions, creating new electron–ion pairs. Hence, the latter processes make the glow discharge a self-sustaining plasma.

The use of the glow discharge as an ion source for mass spectrometry is based on the phenomenon of sputtering. The material to be analysed serves as the cathode of the glow discharge. The argon ions from the plasma (and also fast argon atoms) that bombard the cathode can also release atoms of the cathode material, which is called sputtering. The sputtered atoms arrive in the plasma where they can be ionized. Thus formed ions of the material to be analysed can be detected with a mass spectrometer, giving rise to GDMS. Figure 1 illustrates the basic principles of the glow discharge and its coupling to mass spectrometry.

Figure 1. Schematic of the basic processes in a glow discharge.

Typical discharge conditions used for GDMS are about 1 kV discharge voltage, an argon gas pressure in the order of 1 torr, and a d.c. discharge current in the mA range. The detection limits of this technique are generally in the ppb range.

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EXPERIMENTAL RESULTS ON THE PENETRATION OF SPUTTERED ATOMS INTO A NEUTRAL GAS BLANKET

P. Bogen , A. Elbern , in Proceedings of the International Symposium on Plasma Wall Interaction, 1977

2 EXPERIMENTAL ARRANGEMENT

A glow discharge with an iron cathode of 1 cm or 3 cm diameter mounted in a shaped glass-tube as shown in Fig.1 has been used. The distance between cathode and anode was about 20 cm, the diameter of the cylindrical discharge vessel was 10 cm. A pulsed dye laser with frequency doubling (duration 0.5_/us, bandwidth in the UV about 0.1 Å) was used to excite the λ = 3020 Å resonance transition of Fe. The fluorescence signal which is proportional to the Fe atom density in the ground state was observed at λ = 3820 Å in a direction perpendicular to the drawing plane. An absolute calibration has been performed with an atom beam as described in paper D4 of this conference. The spatial distribution of atoms resolved within 0.2 cm has been obtained over a distance of 2 cm from the cathode by moving the cathode and letting the scattering volume fixed. The change of discharge length showed no detectable influence on the discharge current and voltage.

Fig. 1. Cathode region of the glow discharge. Scattered light is observed perpendicular to the drawing plane. Unit of measures is mm.

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Fe-S Cluster Enzymes Part A

Oleksandr Gakh , ... Grazia Isaya , in Methods in Enzymology, 2017

4.3.1.3 Procedure

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Glow-discharge carbon-coated copper grids for 30   s using a DV-502A vacuum evaporator within a 1–2   h time frame before applying the protein sample.

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Preincubate grid for 1   min by placing it on a 20-μL TN150 buffer drop on Parafilm M®.

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Remove excess buffer with blotting paper, and place a 10-μL drop of protein sample at a concentration between 0.2 and 0.3   mg/mL on the grid for ~   2   min.

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Remove excess protein sample with blotting paper and wash the grid by placing a 7-μL drop of sterile water on the grid for 1   min. Repeat this step once.

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Remove excess water with blotting paper and stain the grid with 5   μL of 1% (w/v) uranyl acetate for 5 and 30   s by successively placing two separate drops of uranyl acetate on the grid, with excess stain drawn off after each application.

6.

Dry the grid on the tweezer for at least 30   min and store grids at room temperature.

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Correlative Light and Electron Microscopy II

Kyle C. Dent , ... Kay Grünewald , in Methods in Cell Biology, 2014

9.2.1.4 Seeding, incubation, and live-cell imaging

Immediately following glow-discharge and application of markers, the grids should be immersed in cell growth media and hydrated with occasional agitation to allow any air bubbles to disperse. At this stage, other support coating protocols can also be applied to increase cell adherence in later cultivation steps (fibronectin, poly-lysine). Following this, grids can be transferred into cell growth chambers. Grids can be placed on coverslips in either 6-well or standard Petri dishes; however, we use microscope slide growth chambers (μ-slide 2   ×   9 well, Ibidi GmbH, Munich, Germany) to facilitate either phase contrast or fluorescence microscopy monitoring of the cell culture prior to cryo-immobilization (Hagen et al., 2012). Use of slide chambers insures that no grid handling is required at this stage. Depending on the cell type, as well as imaging requirements, the appropriate cell confluence (and cell seeding densities) will vary. For most projects, seeding to a confluence of 20% with an incubation time of 24   h will yield an average cell confluence of approximately 40%. Cell confluencies of 50% are typically not exceeded for most projects, although certainly, cryoXM can tolerate higher densities than will cryoET.

Once cells have adhered to the support grid, live-cell fluorescent imaging allows the dynamics of labeled molecules to be observed and, thus, allows cells to be monitored to the point that an event of interest takes place. Specimens can then be rapidly frozen to trap the cell in a state of interest.

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Plasma and Reactive Ion Etching

J.W. Coburn , in Encyclopedia of Materials: Science and Technology, 2001

2.5 Planar Triode Systems

Planar triode glow discharges were used frequently in sputter-deposition processes in the 1960s and 1970s before the introduction of magnetron sources ( Chapman 1980). A large RF power is applied to the target electrode (argon discharge) and this is the source of the sputtered material. A much smaller RF power is applied to the substrates to introduce relatively low-energy ion bombardment during the deposition process. This ion bombardment of the substrates allows beneficial modification of the properties of the sputter-deposited thin films (Thornton 1974). This triode approach was introduced into commercial plasma etching equipment in the mid-1980s and still finds a use in semiconductor manufacturing. A schematic of the triode geometry is shown in Fig. 6.

Figure 6. Capacitively coupled planar triode reactor.

The triode approach solves the problem described in the etching of GaAs above in that the plasma density in the 5   mtorr chlorine plasma can be increased to whatever density is needed by applying a large RF power to the top electrode, while maintaining 100   eV ion bombardment of the wafer with a small RF power applied to the lower electrode. The upper electrode power generates the plasma (i.e., source power) whereas the lower electrode power controls the ion energy (i.e., bias power). The problem is that applying a large RF power capacitively to the top electrode causes very high-energy ion bombardment of the top electrode. What kind of material should be used to fabricate this top electrode? If a material that forms volatile products with the etch gas is used, the electrode will etch rapidly consuming an unacceptable quantity of the etching species. If a material that forms nonvolatile products with the etch gas is used, the electrode will be sputtered by the high-energy ions, a situation similar to, but worse than, the symmetric diode discussed above. Consequently, single-frequency planar triode etching machines are usually operated at pressures that are high enough to avoid significant sputtering of the top electrode.

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A Structure-Function Toolbox for Membrane Transporter and Channels

Joseph A. Lyons , ... Jens Frauenfeld , in Methods in Enzymology, 2017

3.1.1 Equipment

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PELCO EasiGlow Glow Discharge Cleaning System

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Tecnai G2 Spirit electron microscope equipped with an LaB₆ filament and operated at an acceleration voltage of 120   kV and a TVIPS F415 CCD camera with 4k   ×   4k pixels

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Leginon data acquisition software (Suloway et al., 2005)

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Appion data processing suite (Lander et al., 2009)

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EMAN software (Ludtke, Baldwin, & Chiu, 1999)

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RELION version 2.0 (Scheres, 2012)

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Chimera software (Pettersen et al., 2004)

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Computing resources—here we used a GPU cluster (Dell PowerEdge C4130 w/ 2   × Xeon E5-2620v4, 128   GB RAM, 4   × NVIDIA TESLA K80)

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