Electric probes for plasmas: The link between theory and instrument

Demidov, V. I.; Ratynskaia, S.; Rypdal, Kristoffer

doi:10.1063/1.1505099

Cited by 323 publications

(379 citation statements)

References 169 publications

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“…However, other effects such as phase delay errors, ion-sheath expansion and stray capacitance can affect the measurements. 5,8,9 a) Electronic mail: christian.theiler@epfl.ch.…”

Section: Introductionmentioning

confidence: 99%

“…Depending on plasma parameters and probe geometry, different theories exist to interpret the I -V characteristics and deduce plasma parameters. [1][2][3][4][5] Usually, the probe is swept at a frequency much lower than that of typical plasma fluctuations and the I -V curve is used to deduce time average quantities. Time-dependent measurements are often limited to ion-saturation current and floating potential measurements, i.e., to the current drawn from the plasma at a strong negative probe potential and the potential for which the probe draws no current, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Practical solutions for reliable triple probe measurements in magnetized plasmas

Theiler

Furno

Kuenlin

et al. 2011

Review of Scientific Instruments

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The triple probe method to obtain local, time-resolved measurements of density, electron temperature and plasma potential is investigated in detail. The difficulties in obtaining reliable measurements with this technique are discussed and overcome. These include phase delay errors, ion sheath expansion and limited bandwidth due to stray capacitance to ground. In particular, a relatively simple electronic circuit is described to strongly reduce stray capacitance. Measurements with the triple probe are presented in a plasma characterized by interchange-driven turbulence in the TORPEX device. The measured time-averaged and time-dependent, conditionally averaged parameters are cross-checked with other Langmuir probe based techniques, and show good agreement. Triple probe measurements show that electron temperature fluctuations are sufficiently large, such that the identification of plasma potential fluctuations with fluctuations of the floating potential is not a good approximation. Over a large radial region, the time-averaged fluctuation-induced particle flux can, however, be deduced from floating potential only. This is because the phase shift between density and electron temperature is close to zero there and temperature fluctuations do not give rise to a net radial particle transport.

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“…However, other effects such as phase delay errors, ion-sheath expansion and stray capacitance can affect the measurements. 5,8,9 a) Electronic mail: christian.theiler@epfl.ch.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Practical solutions for reliable triple probe measurements in magnetized plasmas

Theiler

Furno

Kuenlin

et al. 2011

Review of Scientific Instruments

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“…26,27 Used in parallel with film deposition, plasma diagnostics ensure process control and reproducibility of the process. Optical emission spectroscopy ͑OES͒, 28,29 quadrupole mass spectrometry ͑QMS͒, 30,31 and diagnostics by means of a retarding field energy analyzer ͑RFEA͒ 32 and a Langmuir probe [33][34][35] are the most common plasma characterization techniques. The last of these provides reliable monitoring of plasma parameters by means of recording I-V characteristics from an electrostatic tip in the glow discharge.…”

Section: Introductionmentioning

confidence: 99%

Plasma parameters of pulsed-dc discharges in methane used to deposit diamondlike carbon films

Corbella

Rubio‐Roy

Bertrán

et al. 2009

Journal of Applied Physics

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Here we approximate the plasma kinetics responsible for diamondlike carbon ͑DLC͒ depositions that result from pulsed-dc discharges. The DLC films were deposited at room temperature by plasma-enhanced chemical vapor deposition ͑PECVD͒ in a methane ͑CH 4 ͒ atmosphere at 10 Pa. We compared the plasma characteristics of asymmetric bipolar pulsed-dc discharges at 100 kHz to those produced by a radio frequency ͑rf͒ source. The electrical discharges were monitored by a computer-controlled Langmuir probe operating in time-resolved mode. The acquisition system provided the intensity-voltage ͑I-V͒ characteristics with a time resolution of 1 s. This facilitated the discussion of the variation in plasma parameters within a pulse cycle as a function of the pulse waveform and the peak voltage. The electron distribution was clearly divided into high-and low-energy Maxwellian populations of electrons ͑a bi-Maxwellian population͒ at the beginning of the negative voltage region of the pulse. We ascribe this to intense stochastic heating due to the rapid advancing of the sheath edge. The hot population had an electron temperature T e hot of over 10 eV and an initial low density n e hot which decreased to zero. Cold electrons of temperature T e cold ϳ 1 eV represented the majority of each discharge. The density of cold electrons n e cold showed a monotonic increase over time within the negative pulse, peaking at almost 7 ϫ 10 10 cm −3 , corresponding to the cooling of the hot electrons. The plasma potential V p of ϳ30 V underwent a smooth increase during the pulse and fell at the end of the negative region. Different rates of CH 4 conversion were calculated from the DLC deposition rate. These were explained in terms of the specific activation energy E a and the conversion factor x dep associated with the plasma processes. The work deepens our understanding of the advantages of using pulsed power supplies for the PECVD of hard metallic and protective coatings for industrial applications ͑optics, biomedicine, and electronics͒.

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“…This because the process pressure, 65-175 Pa, 45 has been too high for Langmuir probes 49 and the collisionless plasma probe theory 50 to work. In an attempt to indirectly measure the plasma density, the discharge current on the substrate holder was measured.…”

Section: Time-resolved Plasma Discharge For Enhanced Plasma Chemistrymentioning

confidence: 99%

Time as the Fourth Dimension: Opening up New Possibilities in Chemical Vapor Deposition

Pedersen

2016

Chem. Mater.

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Thin films of inorganic materials are essential to several technologies we take for granted in our everyday lives. They form the basis of touch screens in smart phones and the electronic components in computers. Dating back more than a century, chemical vapor deposition (CVD) is one of the most common methods to form these films. In CVD, the atoms needed for the thin film are typically supplied by a continuous flow of gaseous precursor molecules and incorporated into the film by gas phase and surface chemical reactions. The continuous demand for more precise thin film fabrication on more complex shapes at lower temperatures sets a demand for more advanced CVD methods. The development of better designed precursor molecules is one important path to evolve CVD, the other path is to evolve the way in which we do CVD. In this perspective I will describe how using time as a fourth dimension in CVD can enable fabrication of new thin film materials and material structures at lower temperatures and on more complex substrate geometries by accessing new types of CVD chemistries available in time-resolved CVD.

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Electric probes for plasmas: The link between theory and instrument

Cited by 323 publications

References 169 publications

Practical solutions for reliable triple probe measurements in magnetized plasmas

Practical solutions for reliable triple probe measurements in magnetized plasmas

Plasma parameters of pulsed-dc discharges in methane used to deposit diamondlike carbon films

Time as the Fourth Dimension: Opening up New Possibilities in Chemical Vapor Deposition

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