Hydrogen Plasma Research Articles

Proton beam energy deposition in fast ignition and production of protons on Shenguang II upgraded device

The proton beam energy deposition and the prodution of proton beams in proton fast ignition are investigated with the fluid program, partice-in-cell program and Fokker-Planck program based on the parameters of Shenguang II upgraded device. Firstly, according to the target parameters of fast ignition, the energy depositions of different energy protons are investigated. It is obtained that the higher the incident proton energy, the higher the surface density that the protons go through, accordingly the longer the proton deposition distance in the same background plasma density. On the assumption that the diameter of the compression core is 20–30 μm, and that the protons deposited in the core give the energy to the background plasma, the energy of the proton required by fast ignition is obtained by Fokker-Planck simulation. Protons with energy of 7–12 MeV are appropriate for ignition when the background plasma density is 300 g/cm<sup>3</sup>, while 8–18 MeV protons for 400 g/cm<sup>3</sup>. The background plasma temperatures are both 5 keV in the two cases. Secondly, we use particle-in-cell program to study the proton acceleration with or without preplasma which is given by fluid program with using the laser intensity <inline-formula><tex-math id="M1">\begin{document}$ I = 5.4 \times {10^{19}}{\text{ }}{\rm{W/c}}{{\rm{m}}^2} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20222005_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20222005_M1.png"/></alternatives></inline-formula> based on the parameters of Shenguang II upgraded device. The laser has 350 J of enegy, 3 ps of Gaussion pluse width and 10 µm of spot radius. The curvature of the target which is 10 µm thick copper coated with 1 µm thick hydrogen plasma, is 500 µm. The maximum proton energy obtained with preplama is 22 MeV, however the maximum proton energy obtained without preplasma is 17.5 MeV. The conversion efficiency from laser to protons is 5.12% with preplasma and 4.15% without preplasma. The conversion efficiency with preplasma is 20% higher than that without preplasma. We also study the mechanisms of the acceleration in the two situations. The freely expanding plasma model is used to explain the acceleration mechanism. The simulated electric field is smaller than that calculated by using the freely expanding plasma model, because some protons are accelerated at the time of plasma expansion, which consumes some electric field. The results of proton energy deposition show that the proton beams that are suitable for fast ignition can be obtained by the Shenguang II upgraded device.

Exergy, techno-economic and environment analysis of food waste plasma gasification and syngas chemical looping processes

To mitigate the problem of food waste, this study investigated two food waste treatment processes: plasma gasification hydrogen production and plasma gasification coupled with chemical looping, for converting food waste into high-quality hydrogen energy. Based on Aspen Plus software simulation results, the exergy, economic, and environmental benefits of the hydrogen production system were analyzed. Food waste hydrogen production using plasma gasification technology exhibits a high production capacity and economic input. Its hydrogen production capacity is 6.47 t/t H2 with a corresponding product cost of 2449.82 USD/t H2. The high economic input is mainly owing to the high power consumption of the plasma torches. Plasma gasification coupled with chemical looping can employ high-temperature gas to generate power, which can partially alleviate electricity consumption. In addition, in terms of thermodynamic benefits, the exergy efficiencies of plasma gasification hydrogen production and plasma gasification coupled with chemical looping are 31.44% and 54.31%, respectively. Plasma gasification coupled with chemical looping is more environmentally friendly based on the acidification and global warming potentials. The proposed novel process promotes food waste resource treatment and energy reuse.

Spatially‐Modulated Silicon Interface Energetics Via Hydrogen Plasma‐Assisted Atomic Layer Deposition of Ultrathin Alumina

AbstractAtomic layer deposition (ALD) is a key technique for the continued scaling of semiconductor devices, which increasingly relies on scalable processes for interface manipulation of structured surfaces on the atomic level. While ALD allows the synthesis of conformal films with utmost control over the thickness, atomically‐defined closed coatings and surface modifications are challenging to achieve because of 3D growth during nucleation. Here, a route is presented toward the sub‐nanometer thin and continuous aluminum oxide (AlOx) coatings on silicon substrates for the spatial control of the surface charge density and interface energetics. Trimethylaluminum in combination with remote hydrogen plasma is used instead of a gas‐phase oxidant for the transformation of silicon dioxide (SiO2) into alumina. Depending on the number of ALD cycles, the SiO2 can be partially or fully transformed, which is exploited to deposit ultrathin AlOx layers in selected regions defined by lithographic patterning. The resulting patterned surfaces are characterized by lateral AlOx/SiO2 interfaces possessing 0.3 nm step heights and surface potential steps exceeding 0.4 V. In addition, the introduction of fixed negative charges of 9 × 1012 cm−2 enables modulation of the surface band bending, which is relevant to the field‐effect passivation of silicon and low‐impedance charge transfer across contact interfaces.

Surface-limited deuterium uptake of Ru films under plasma exposure

Blister formation has been an emerging research topic for extreme ultraviolet (EUV) mirrors exposed to hydrogen plasmas. Similar to plasma-facing materials in nuclear fusion reactors, it has been reported that blister formation in EUV mirrors is initiated by hydrogen uptake due to hydrogen ion or atom bombardment. However, the research so far has focused on Mo/Si multilayers exposed to only hydrogen ions or atoms, while the EUV mirror typically has a Ru capping layer facing hydrogen plasmas. We present experimental work to measure plasma-induced hydrogen uptake of Ru films. We bombarded our designed Ru-capped target with a low-temperature deuterium plasma and measured the deuterium retention using elastic recoil detection. Contrary to ion-driven deuterium uptake, the deuterium uptake rate of the Ru film had no dependence on the deuterium ion flux or energy after a period of plasma exposure. A reaction–diffusion model has been built to calculate the time evolution of deuterium retention, which well fits the experimental data. Based on this model, we conclude that the surface composition of the Ru film is the limiting factor for the deuterium uptake, which is seriously weakened when the surface is covered by Ru oxide. After the Ru oxide is reduced by the plasma, the uptake rate is predominantly driven by the deuterium surface coverage on metallic Ru. Our model also indicates that at the deuterium-populated Ru surface, deuterium has a low absorption barrier to penetrate the surface, which is supported by previously reported computational work.

Synchrotron-Excited Luminescence and Converting of Defects and Quantum Dots in Modified Silica Films

Optically active defects in modified silicon oxide films on a silicon substrate have been studied by low-temperature photoluminescence (PL) spectroscopy using excitation by synchrotron radiation in the vacuum ultraviolet region. Films of dry thermal silicon oxide obtained by treatment of stoichiometric SiO2 in hydrogen plasma, films of wet thermal silicon oxide, and films with low dielectric constant (so called "low-k" dielectrics) have been studied. Investigations of various type SiO2 films detect the PL centers, which can be conditionally divided into two groups. The first group includes intrinsic point defects, the different variants of oxygen-deficient centers (ODCs). The second group contains centers like the spatially confined excitons in silicon quantum dots (SiQDs). It is shown that SiQDs differ in spectral characteristics, are formed in different ways, due to the transformation and clustering of point defects such as E'-centers, ODC(I) and ODC(II). In this case, the size and spectral properties of quantum dots depend on the mechanism of their formation. Schemes for the conversion of these defects are proposed.It was found that for wet films and nonstoichiometric SiOx films treated in hydrogen plasma, "metastable" centers ODC(I) and ODC(II) arise only under the action of synchrotron radiation in the region of interband or exciton absorption and then they decay because of radiative relaxation. The absence of stable ODC centers in these films is due to their clustering and the formation of SiQDs. In "low-k" mesoporous films, on the contrary, silicon quantum dots SiQDs are not formed, but ODC(I) and ODC(II) centers are clearly manifested. A scheme of electronic transitions upon indirect excitation of silicon quantum dots through exciton states of the SiO2 matrix is considered. The presented results demonstrate the possibility of controlling the optical properties of silicon thin-film structures by creating in them both oxygen-deficient point defects and quantum dots of various sizes.

Termination of graphene edges created by hydrogen and deuterium plasmas

Edge engineering is important for both fundamental research and applications as the device size decreases to nanometer scale. This is especially the case for graphene because a graphene edge shows totally different electronic properties depending on the atomic structure and the termination. It has recently been shown that an atomically precise zigzag edge can be obtained by etching graphene and graphite using hydrogen (H) plasma. However, edge termination had not been studied directly. In this study, termination of edges created by H-plasma is studied by high-resolution electron energy loss spectroscopy to show that the edge is sp2 bonded and the edge carbon atom is terminated by only one H atom. This suggests that an ideal zigzag edge, which is not only atomically precise but also sp2 bonding, can be obtained by H-plasma etching. Etching of the graphite surface with plasma of a different isotope, deuterium (D), is also studied by scanning tunneling microscopy to show that D-plasma anisotropically etches graphite less efficiently, although it can make defects more efficiently, than H-plasma.

STABILITY OF THIN QUASI-CRYSTALLINE Ti-Zr-Ni FILMS AND RELATED CRYSTALLINE PHASES UNDER LOW-ENERGY TRANSIENT PLASMA IRRADIATION

The properties of Ti41Zr38.3Ni20.7 thin films under radiation-thermal action of hydrogen plasma with a surface heat load of 0.2 MJ/m2 was studied at the QSPA Kh-50 quasi-stationary plasma accelerator (NSC KIPT).The phase composition, structural state, and surface morphology were studied using X-ray diffraction and scanning electron microscopy. It was found that the quasicrystalline phase and related crystalline phases, the Laves phase, the α-solid solution, and the 2/1 phase of the Ti-Zr-Ni approximant crystal were stable under irradiation with up to 20 hydrogen plasma pulses. The phase composition did not change. It is shown that the changes in the coatings mainly manifest themselves as changes in the substructure of the observed phases. With an increase in the plasma exposure dose, the structure of the quasicrystalline icosahedral phase improves, and the size of the coherence regions increases. In the films consisting of crystalline phases, a partial phase transformation is observed with a redistribution of components between the 2/1 phase of the approximant crystal and the α-solid solution phase. It was found that thin films of the TiZr-Ni system containing a quasicrystalline icosahedral phase, irradiated with radiation-thermal plasma pulses, are less prone to cracking than coatings with crystalline phases of the same system.

Interaction between hydrogen and helium in tungsten successively exposed by helium and hydrogen plasma

The modification of surface, distribution of helium bubbles and the behavior of helium release are reported through a careful investigation on tungsten samples which were exposed to helium plasma and subsequent hydrogen plasma. For the tungsten samples exposed to helium plasma with a fluence of 3.8×1024 He/m2, no obvious change can be seen on the tungsten surface. Then the samples were exposed to subsequent hydrogen plasma for 1 h. Hydrogen blistering was significantly suppressed on the tungsten surface compared to a reference sample which was only irradiated by hydrogen plasma. However, as the exposure time of hydrogen plasma increased to about 16 h, a large number of hydrogen blisters appeared on the surface of tungsten pre-irradiated by helium plasma. Moreover, there was no significant difference in hydrogen blistering between the helium pre-exposure samples and the reference sample. The results indicate that most of the hydrogen atoms can diffuse into tungsten through the nano-helium bubble layer after 16 h of hydrogen plasma exposure. The results of transmission electron microscope show that the size of bubbles was increased with the increase of hydrogen exposure time. In contrast, the helium release peaks obtained through thermal desorption spectra are reduced with the increase of hydrogen exposure time.

Influence of plasma and heat treatments on the properties of ZnO nanorods

Oxide semiconductor nanostructured materials attract considerable attention of researchers due to their efficiency in electronics, optics, photonics, and other applications. One-dimensional semiconductor nanostructures such as nanowires, nanorods, and nanotubes are widely used for both academic research and industrial applications. Such nanostructures are useful materials for investigating of the dependence of electrical, thermal, and mechanical properties on dimensionality and size reduction. Actual study is the effect of postgrowth treatments on the properties of synthesized materials in order to improve their optical and electrical characteristics. In this work, we consider the effect of thermal annealing and treatment in hydrogen plasma on the morphology, optical, structural, and photoluminescent properties of samples consisting of zinc oxide nanorods obtained by chemical solution deposition. It is shown that the passivation of charged oxygen acceptors on the surface of grain boundaries upon short-term treatment in hydrogen plasma followed by thermal treatment in air makes it possible to activate the photoluminescence of ZnO obtained by chemical solution deposition and to obtain conductive transparent layers of ZnO nanorods with intense photoluminescence.

Performance Improvement of InGaN-Based LEDs via a Current-Blocking Region Prepared via Hydrogen Passivation

We report p-GaN passivation via hydrogen plasma used to create current blocking regions (CBRs) in InGaN-based green LEDs with standard dimensions of 280 × 650 μm2. The CBRs are created before mesa etching in two variants: underneath the opaque metal p-pad and both underneath the p-pad and along the device’s mesa perimeter. The peak EQE increased by 13% and 23% in the first and the second cases, respectively, in comparison to the reference LED with no CBR. With a high injection current of 50 A/cm2, the EQE value increased by 2% in the case of CBRs underneath the p-pad as well as by 14% in the case of CBRs both underneath the p-pad and along the mesa perimeter (relative to the reference sample with no CBR).

Improved hydrogenation process for margarine production with no trans fatty acid formation by non-thermal plasma with needle-in-tube configuration

Non-thermal dielectric barrier discharge (DBD) plasma with needle-in-tube configuration was used to improve hydrogenation reaction for trans -fat free margarine production. Refined palm olein was used as raw material with operating conditions at ambient pressure, room temperature (29 °C) and no catalyst. Effects of hydrogen gas (H 2 ) concentration, input power, gas flow rate, discharge gap size and reaction time on fatty acid compositions and properties of hydrogenated refined palm olein after plasma treatment was evaluated. Lowest iodine value (IV) was achieved with reduction from 60.75 to 23.56 with increase in saturated fatty acid composition from 40.82 ± 0.05 to 68.70 ± 0.07% and decrease in unsaturated fatty acid composition from 59.11 ± 0.12 to 31.39 ± 0.01% under the condition of 0.5 L/min gas flow rate with 100% H 2 , 40 W input power, 0.5 cm gap size and 15 h reaction time. In addition, no trans -fat was detected by GC-MS analysis. Slip melting point (SMP) was increased from 9.33 ± 0.5 to 36.33 ± 0.5 °C. Acid value (AV) was reduced from 0.47 ± 0.02 to 0.32 ± 0.03 mg KOH/g oil. Texture of produced margarine was similar to that of commercial one. Generated hydrogen free radicals were hypothesized to perform hydrogenation by reacting with carbon-carbon double bonds (π-bonds), converting poly- and monounsaturated fatty acids into saturated ones. This highly effective catalyst-free plasma hydrogenation system can be used as alternative, environmentally friendly and economically feasible method to produce trans -fat free margarine. • Production of trans -fat free margarine via non-thermal plasma hydrogenation of palm olein. • Highly environmental-friendly, requiring no catalyst under low temperature and pressure. • Reduced acid value provides increased storage time and longer shelf life.

Control of silicon dioxide etching rate in hydrogen microwave plasma by addition of oxygen

Hydrogen plasma treatment of thin films and bulk silica is important process for surface cleaning, smoothing and patterning. We studied etching of SiO2 plates in H2 + O2 microwave plasma at moderate pressures at high temperatures in the range of 790–1300 °C. A low-coherent optical interferometer was used for simultaneous in situ measurement of etch rate (ER) and the SiO2 temperature. We show that even a small addition of O2 (<1%) in microwave H2 plasma can effectively reduce the SiO2 ER due to redox reaction. Using an optical profilometry and atomic force microscopy we observed not only a strong etching inhibition by O2 addition in gas, but a significantly smoother etched surface as well. The activation energies Ea = 128 ± 8 kJ/mol and 276 ± 23 kJ/mol are found for the etching in pure H2 and H2 + 0.4 %O2 plasmas, respectively. An exponential dependence of ER on O2 content in gas is established, particularly, the O2 concentration as small as 2.6 % is sufficient to reduce the ER by 100 times. The effect of oxygen induced etching slow-down is supported by thermodynamic consideration of the surface reactions involved. The experiments were complimented with the plasma diagnostics by optical emission plasma spectroscopy to detect volatile etching products, and other species such as OH, and correlate the Si emission intensity with the measured ER. Our results confirm the efficiency of oxygen to control in a wide range the etch rate and surface topography upon atomic hydrogen etching in a microwave plasma.

Visualization of localized facet Joule heating induced optical degradation on mid-infrared quantum cascade lasers.

Reversible lasing performance degradation is investigated on an uncoated actively- biased GaAs/Al0.45Ga0.55As mid-infrared quantum cascade laser (MIR-QCL) facet. The surface temperature rises (ΔT) on the MIR QCL are characterized before and after the device undergoes an accelerated aging burn-in test, followed by hydrogen plasma treatment. The data is visualized by spatially resolved time-domain thermoreflectance (SR-TDTR) microscopy. On the laser facet, ΔT decreases with a drop in lasing performance and ΔT increases with an increase in lasing performance. Along the laser cavity, the thermal property change is negligible before and after the aging test, independent of the optical performance change. The results verify that thermal-induced facet oxidation is the main reason for the rapid degradation of the lasing performance in the early aging stage.

Reducing the L-H transition power threshold in ITER-similar-shape DIII-D hydrogen plasmas

Recent dedicated DIII-D experiments in low-torque, ITER-similar-shape (ISS) hydrogen plasmas (at a plasma current I p ∼ 1.5 MA and ITER-similar edge safety factor q 95 ∼ 3.6) show that the L-H transition power threshold P LH can be reduced substantially (∼30%) with L-mode helium admixtures n He/n e ⩽ 25%. In the ensuing H-mode, helium ion fractions n He/n H remain below 25%. H-mode normalized pressure and confinement quality are only slightly affected by helium seeding, and Z eff ⩽ 2.15 (including helium and carbon content). The plasmas investigated here are electron-heat dominated, with temperatures T e(0)/T i(0) ⩾ 1 and edge heat flux ratio Q e/Q i(ρ = 0.95) ∼ 1.2–1.5. Without mitigation, P LH is higher by a factor of 2–3 in comparison to similar ISS deuterium plasmas. ISS hydrogen plasmas with lower plasma current I p ∼ 1 MA (increased edge safety factor q 95 ∼ 5.1) exhibit a substantially lower power threshold. This plasma current dependence, also observed previously on ASDEX-U and in JET, is not accounted for by the commonly used 2008 ITPA multi-machine threshold scaling, but could potentially allow H-mode access at marginal heating power during the initial plasma current ramp-up. Attempts to reduce P LH with low-field- and high-field-side hydrogen pellet injection, using 1.7 mm diameter pellets, have not demonstrated a robust threshold reduction, in contrast to successful earlier experiments with larger 2.7 mm pellets. Techniques for reducing P LH are very important for ITER, in particular for accessing H-mode in hydrogen plasmas during the Pre-Fusion Power Operation-1 (PFPO-1) campaign with marginal auxiliary heating power (20–30 MW of ECH).

Real-time VUV radiation monitoring in low-pressure hydrogen plasma based on fluorescence of sodium salicylate

Recently, vacuum ultra-violet (VUV) radiation emitted from plasmas has been of particular interest in semiconductor device fabrication because of the effects of its high-energy photons, such as induced damage or curing on low-k materials. Due to the difficulty of implementing conventional spectroscopic methods to monitor VUV radiation with high accuracy and time resolution in current plasma processing equipment, novel monitoring methods must be investigated. Therefore, in this work, we developed a compact VUV radiation monitoring system based on a scintillator, i.e. sodium salicylate (NaSal), for real-time VUV measurements. Compared to conventional VUV spectrometers, the system shows considerable implementation potential thanks to its compact size, higher detection accuracy and high time resolution. VUV radiation emitted by continuous and pulsed hydrogen plasmas generated at low pressure was investigated using the developed system. Using various filters, we were able to compare the VUV photon intensity in different wavelength ranges. It was found that the VUV photon intensity between 115 and 250 nm was about 2.5 times higher than in the region below 115 nm due to intense Lyman-α and molecular radiation, such as Lyman and Werner bands observed in low-pressure hydrogen plasmas.

Two-color laser scattering for diagnostics of hydrogen plasma

A two-color laser scattering (2CLS) method is proposed to measure electron and neutral densities, as well as electron and ion temperatures in hydrogen plasma. 2CLS uses two probe wavelengths to identify the Rayleigh scattering and Thomson scattering contributions coming from neutrals and electrons, respectively. Laser scattering signals were simulated for various conditions of a hydrogen plasma at thermodynamic equilibrium applying the available and calculated cross-sections for Rayleigh scattering by ground-sate and excited hydrogen atoms at probe wavelengths of 355 nm and 532 nm. The developed 2CLS method was eventually applied to study the laser-induced plasma in hydrogen at near atmospheric pressure. Temporally and spatially resolved electron and ion temperatures and densities of electrons and hydrogen atoms (ground-state and excited) were determined.

Cs Evaporation in a Negative Ion Source and Cs Cleaning Tests by Plasma Sputtering

The compact radio frequency negative ion source negative ion optimization phase 1 (NIO1) has been designed, built, and operated by Consorzio RFX and INFN-LNL in order to study and optimize the production and acceleration of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}^{-}$ </tex-math></inline-formula> ions in continuous operation. In 2020, Cs was evaporated in the source to increase the total extracted ion current. After an initial reduction of extracted electron to ion ratio and subsequently an increase of extracted negative ion current, the source performances progressively worsened, because of the excessive amount of Cs evaporated in the source; the extracted electron to ion ratio increased from below 1 to more than 10, while ion current density reduced from max. 67 A/m2 ion current to not more than 30 A/m2. This article presents the experimental observations collected during Cs evaporation (reduction of plasma light, Cs emission, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{\beta } / H_{\gamma }$ </tex-math></inline-formula> ratio, and so on) that can help stopping the process before an excessive amount of Cs is introduced in the source. This article also reports the cleaning techniques tested to remove the Cs excess by the action of hydrogen or argon plasmas, while argon was predictably more effective in surface sputtering, and a 3-h Ar plasma treatment was not sufficient to recover from overcesiation.

Investigation of a facile plasma-driven method for in situ cleaning of metal-based contamination

Self-cleaning of tin contaminants was realized utilizing a self-driven hydrogen plasma. Cleaning rates of 0.7–6 nm min−1 were achieved for removal of discontinuous tin particles at different powers. The analysis of topography and cross-sectional morphology revealed that the removal of tin particles was achieved through top-down cleaning with hydrogen plasma, where the upper part of spherical tin particles was always more intensely cleaned under the synergistic effect of hydrogen atoms and ions due to the vertical incidence of ions to the substrate during the whole cleaning process. Redeposition of tin atoms caused by physical sputtering and its promotion of the chemical cleaning effect was observed for the first time. Reflectance recovery measurements during cleaning and surface analysis of the substrate after cleaning indicated that nondestructive cleaning with a reflectance loss of less than 1% can be achieved at a relatively low power of 120 W. Plasma-induced substrate damage, such as holes and valleys, reduced the reflectance of the substrate when cleaning was performed at a high power greater than 120 W, so this method should only be considered for application under conditions without substrate exposure. This study provides a comprehensive understanding of the removal of discontinuous tin particles using the in situ self-driven plasma cleaning method, and also provides meaningful guidance for the extension of this method in other potential fields of application.

Advances in Magnum-PSI probe diagnosis in support of plasma–surface interaction studies

Magnum-PSI is a linear plasma generator equipped with a superconducting magnet, assuring fusion devices relevant conditions at plasma–surface interface. The plasma column was diagnosed using 64 probes embedded in the target. The cross-sectional distributions of plasma parameters (floating potential, ion saturation current and electron temperature) were measured for hydrogen and deuterium plasmas under various discharge conditions. The radial profile of the floating potential across the plasma column can be described by a reversed Mexican hat-like wavelet, having the most negative potential at the center of the plasma column. The negativity of the floating potential diminishes when the discharge current increases or the magnetic field decreases. The axial gradient of the floating potential is reduced by increasing the magnetic field. The ion saturation current is maximum at the center of the plasma column, increasing with both the discharge current and magnetic field. The ion flux to the target, estimated from Thomson scattering (TS) data, was confirmed by probe measurements. The electron temperature estimated from the ion branch of the probe current–voltage characteristic is few times larger than that obtained from TS. By increasing the gas pressure in the target chamber, the time-dependent ion saturation current measured by probes changes from a constant average current (when the plasma column is attached to the target) to a fluctuating average current with scattered peaks (in a partially detached regime) which vanishes completely in the fully detached regime. With respect to hydrogen, the plasma column is wider in deuterium and is characterized by less negative floating potential distributions.

Hydrogen Plasma on Graphene Oxide to Produce Gradients of Oxygen-Containing Functional Groups for Self-Powered Devices

Hydrogen Plasma on Graphene Oxide to Produce Gradients of Oxygen-Containing Functional Groups for Self-Powered Devices