High Frequency Glow Discharge Research Articles

In vitro renal calculi destruction by a high-frequency glow discharge plasma

Despite the progress made in the treatment of nephrolithiasis, the existing methods of renal calculi destruction are not ideal and have both advantages and disadvantages. Considering the process of high-frequency glow discharge formation on the surface of an electrode and in an electrolyte solution, we obtained the results on the destruction of renal calculi in vitro. It was shown that the destruction of kidney stones by glow discharge plasma was caused by several processes—the plasma induced effect of hydrated electrons and shock wave effect of the electrolyte stimulated by electrical breakdowns in the plasma. The plasma generation modes were configured by estimating the thickness of the vapor–gas layer in which the plasma burns. Thus, the average rate of contact destruction of renal calculi was measured depending on the plasma generator input power and time of plasma exposure. We conclude that the method of stone fragmentation by high-frequency electrolyte plasma is rather perspective and can be used in endoscopic urology for percutaneous and transurethral lithotripsy.

Increase of Productivity and Neutralization of Pathological Processes in Plants of Grain and Fruit Crops with the Help of Aqueous Solutions Activated by Plasma of High-Frequency Glow Discharge.

In this work, we, for the first time, manufactured a plasma-chemical reactor operating at a frequency of 0.11 MHz. The reactor allows for the activation of large volumes of liquids in a short time. The physicochemical properties of activated liquids (concentration of hydrogen peroxide, nitrate anions, redox potential, electrical conductivity, pH, concentration of dissolved gases) are characterized in detail. Antifungal activity of aqueous solutions activated by a glow discharge has been investigated. It was shown that aqueous solutions activated by a glow discharge significantly reduce the degree of presence of phytopathogens and their effect on the germination of such seeds. Seeds of cereals (sorghum and barley) and fruit (strawberries) crops were studied. The greatest positive effect was found in the treatment of sorghum seeds. Moreover, laboratory tests have shown a significant increase in sorghum drought tolerance. The effectiveness of the use of glow-discharge-activated aqueous solutions was shown during a field experiment, which was set up in the saline semi-desert of the Northern Caspian region. Thus, the technology developed by us makes it possible to carry out the activation of aqueous solutions on an industrial scale. Water activated by a glow discharge exhibits antifungicidal activity and significantly accelerates the development of the grain and fruit crops we studied. In the case of sorghum culture, glow-discharge-activated water significantly increases drought resistance.

An Activated Potassium Phosphate Fertilizer Solution for Stimulating the Growth of Agricultural Plants

This study aimed to develop a sustainable industrial chemical engineering technology to improve the interaction between technology, plants, and soil in agriculture. The signaling crosstalk between H2O2 and NO and that between H2O2 and Ca2+ influence plant developmental and physiological processes. Many promising technologies for crop stimulation and protection are based on a thorough study of the environmental impact of various physical factors. A low-temperature, high-frequency plasma was generated via cathode high-frequency glow discharge and used for the electrolysis of an aqueous solution of a low concentration of the strong electrolyte KH2PO4, with an electrolysis-activated solution named Plasmolite. The Plasmolite solution yielded a Raman (red) scattering spectrum with a maximum at 1,640 cm−1, which was associated with hydrogen atom vibrations, and other bands at 875, 930, 1,050, and 1,123 cm−1, which were associated with the aqueous electrolyte solution plasma treatment. Based on the goal of producing an optimal H2O2 concentration of 100 μM, two types of seeds were exposed to a Plasmolite-based 2 × 10–5 M KH2PO4 solution moisturizing medium for three days. Approximately 92% of the spring spelled seeds (grade “Gremme”) that were exposed to this test solution sprouted, compared with 76% of the seeds exposed to a control solution. The spring rye seeds (grade “Onokhoyskaya”) that were exposed to the test solution sprouted at a rate of 90% compared with 75% in the control. The percentage of seeds that sprouted with a root length of more than 6 mm was approximately 80% for the test solution, compared to 50% for the control. Based on these results, the use of Plasmolite is considered to be promising for the production of activated H2O2 for protecting plants and stimulating growth, particularly for enhancing the functions of K and P2O5 of fertilizers.

A new method of potenciation of aqueous media using high-frequency glow discharge plasma

A method of activation of aqueous solutions of strong electrolytes using high-frequency glow discharge plasma in water vapor at atmospheric pressure is considered. An experimental setup for activation of aqueous solutions of NaCl and KCl salts, sodium sulfate Na2SO4, potassium sulfate K2SO4, etc. is presented. Experimental studies were conducted using an activated solution based on potassium sulfate K2SO4, at a concentration of 5.7×10−2 M. The limit values of acidity, redox potential (Eh) and hydrogen peroxide concentration of the prepared activated solution were: pH ≍ 8.3, Eh ≍ 800, H2O2 concentration ≍ 5×10−4 mol. %. The effectiveness of the K2SO4 - based activated aqueous solution was evaluated at test sites of typical crops, such as soybeans and corn. Based on the results obtained, it is concluded that the method of activation of aqueous solutions using high-frequency glow discharge plasma is quite simple, technological and low-cost.

Activation of aqueous solutions by high-frequency glow discharge plasma in water vapor to stimulate growth and control diseases of agricultural plants

The results of an experimental study of the activation of weak aqueous solutions of a strong electrolyte with a low-temperature glow discharge plasma are presented. A method for producing an activated aqueous solution based on 0.9 % NaCl solution in a glow discharge plasma at atmospheric pressure is presented. The main characteristics of the activated aqueous solution, including the Raman spectrum at a wavelength λ = 514,53 nm, are shown. The results of experiments on the test objects give an assessment of the effectiveness of the effect of the obtained activated aqueous solution on various crops. In particular, experimental confirmation of the possibility of using this activated solution as a plant growth regulator was obtained.

The Radio-Frequency Capacitive Normal Glow Discharge in Axial Magnetic Field

A numerical model of a normal axisymmetric high-frequency capacitive glow discharge in an axial magnetic field is considered. The analysis of previous investigations on α- and γ-forms of high-frequency discharges was performed. Using the author’s created numerical model, a study of the electrodynamic structure of a normal high-frequency axially symmetric glow discharge was performed with the following parameters: distance between electrodes of H = 2 cm, pressure of p = 5 Torr, amplitude voltage drop on the inter-electrode gap of E0 = 460 and 478 V, coefficient of the secondary ion-electron coefficient emissions of γ = 0.33. The two-dimensional electrodynamic structure of the γ-form of the high-frequency glow discharge was studied without and with an axial magnetic field induction of Bx = 0.1 T. A qualitative explanation of the reasons for the radial expansion of the current channel of a high-frequency discharge in a normal mode is given.

Material and solar cell research in high efficiency micromorph tandem solar cell

“Micromorph” tandem solar cells consisting of a microcrystalline silicon bottom cell and an amorphous silicon top cell are considered as one of the most promising new thin-film silicon solar-cell concepts. Their promise lies in the hope of simultaneously achieving high conversion efficiencies at relatively low manufacturing costs. The concept was introduced by IMT Neuchâtel, based on the VHF-GD (very high frequency glow discharge) deposition method. The key element of the micromorph cell is the hydrogenated microcrystalline silicon bottom cell that opens new perspectives for low-temperature thin-film crystalline silicon technology. This paper describes the use, within p–i–n- and n–i–p-type solar cells, of hydrogenated amorphous silicon (a-Si:H) and hydrogenated microcrystalline silicon (_c-Si:H) thin films (layers), both deposited at low temperatures (200_C) by plasma-assisted chemical vapour deposition (PECVD), from a mixture of silane and hydrogen. Optical and electrical properties of the i-layers are described. Finally, present performances and future perspectives for a high efficiency ‘micromorph’ (mc-Si:Hya-Si:H) tandem solar cells are discussed.

Investigation of the Dependence of Argon Metastable State Population on the Conditions of High-Frequency Glow Discharge Excitation

The population of metastable states of argon atoms in high-frequency glow discharge plasma is calculated. Dependences of the population of metastable states of argon atoms in the high-frequency glow discharge plasma on the standard gas flow rate (14–30 sccm) and vibration generator power (10–50 W) in the atmospheres of pure argon and argon-silane (95% Ar + 5% SiH4) mixture are investigated together with the dependence of the population of metastable states of argon atoms in the high-frequency glow discharge plasma on the silane content (0.5–5%) in the argon-silane mixture.

Elemental analysis of coatings by high-frequency glow discharge optical emission spectroscopy

The physical basics of glow discharge optical emission spectroscopy are considered. The scheme of the system used for chemical analysis of coatings by glow discharge optical emission spectroscopy is described by the example of a Profiler 2 instrument (Horiba Jobin Yvon). Various types of coatings and methods for surface treatment are compared. On the basis of these studies, it is established that, under the basic measuring regimes without fine adjustment of sputtering parameters, the maximum analyzed depth of coatings is around 80 μm and the depth resolution is 10–20 nm. Almost any combinations of substrate and coating materials, including ceramics, glasses, and polymers, can be analyzed.

High-Efficiency, Multijunction nc-Si:H-Based Solar Cells at High Deposition Rate

Hydrogenated nanocrystalline silicon (nc-Si:H) is a promising candidate to replace the hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) in multijunction thin-film silicon solar cells due to its superior long-wavelength response and stability against light-induced degradation. Due to its indirect bandgap, the absorbing nc-Si:H layer needs to be much thicker than its amorphous counterpart. For nc-Si:H-based solar cells to be commercially viable, the challenge is to deposit the nc-Si:H layer at a high rate with good quality. In this paper, we report on the development of our proprietary high-frequency glow discharge deposition technology to fabricate high-efficiency, large-area, a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells at a high deposition rate >;1 nm/s. The National Renewable Energy Laboratory (NREL) has confirmed stable efficiency of 12.41% on a 1.05-cm2 solar cell. We have attained initial efficiency of 12.33% on an encapsulated cell of aperture area ~400 cm2 ; the corresponding stable efficiency is projected to be 11.7-11.9%.

The microstructure and optical properties of crystallized hydrogenated silicon films prepared by very high frequency glow discharge

A series of nc-Si:H films with different crystalline volume fractions have been deposited by very high frequency glow discharge in a plasma with a silane concentration [SiH 4]/([SiH 4] + [H 2]) varying from 2% to 10%. The nc-Si:H films have been characterized by Raman spectroscopy, XRD diffraction, and UV–vis–near infrared spectrophotometer. The deposition rate increases nearly linear with increasing the silane concentration while the crystalline volume fraction decrease from 58% to 12%. The refractive index and the absorption of the samples were obtained through a modified four-layer-medium transmission model based on the envelope method. It was found that the refractive indices and absorption coefficient increase with increasing silane concentration. Compared to the films deposited using conventional RF-PECVD with excitation frequency of 13.56 MHz, the samples prepared by very high frequency glow discharge have higher absorption coefficients, which is due to its better compactness and lower defect density.

Ultrasonic attenuation in amorphous silicon at 50 and 100 GHz

We have measured the attenuation of longitudinal acoustic waves in a series of amorphous and nanocrystalline silicon films using picosecond ultrasonics. The films were grown using a modified very high frequency glow discharge method on steel substrates. The deposition conditions were similar to that used in the fabrication of high-efficiency solar cells. The film thicknesses were varied so we could distinguish between interface losses and intrinsic losses within the silicon films. We determine the attenuation of amorphous Si to be 780 \ifmmode\pm\else\textpm\fi{} 160 cm${}^{\ensuremath{-}1}$ at 100 GHz and 340 \ifmmode\pm\else\textpm\fi{} 120 cm${}^{\ensuremath{-}1}$ at 50 GHz, values that are lower than those predicted by theories based on anharmonic interactions of the sound wave with localized phonons or extended resonant modes. We determine the attenuation of nanocrystalline Si at 50 GHz to be nearly an order of magnitude higher than amorphous Si (2600 \ifmmode\pm\else\textpm\fi{} 660 cm${}^{\ensuremath{-}1}$) and compare that value to a simple Rayleigh scattering prediction.

High Efficiency, Large Area, Nanocrystalline Silicon Based, Triple-Junction Solar Cells

ABSTRACTWe have fabricated large-area, thin-film multijunction solar cells based on hydrogenated amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si:H) made in a large area batch reactor. The device structure consisted of an a-Si:H/nc-Si:H/nc-Si:H stack on Ag/ZnO back reflector coated stainless steel substrate, deposited using our proprietary High Frequency (HF) glow discharge technique. For the nc-Si:H films, we investigated two deposition rate regimes: (i) low rate <1 nm/s and (ii) high rate >1 nm/s. We optimized the deposition parameters, such as pressure, gas flow, dilution, and power. We did SIMS analysis on the optimized films, and found the impurity concentrations were one order of magnitude lower than the films made with the conventional RF process. In particular, the oxygen concentration is reduced to ~1018 cm-3. This value is among the lowest oxygen concentration reported in literature. The low impurity content is attributed to proprietary cathode hardware and the optimized deposition process. During the initial optimization and investigative phase, we fabricated small-area (0.25 cm2 and 1.1 cm2) cells. The information obtained from the initial phase was used to fabricate large-area (aperture area 400 cm2) cells, and encapsulated the cells using the same flexible encapsulants that are used in our commercial product. We have light soaked the low-rate and high-rate encapsulated modules. The highest initial efficiency of the low-rate modules is 12.0% as confirmed by NREL. The highest corresponding stable efficiency attained for the low-rate samples cells is 11.35%. For the high-rate small-area (1.1 cm2) cells, the highest initial active-area efficiency and corresponding stable efficiency attained are 13.97% and 12.9%, respectively. We present the details of the research conducted to develop the low- and high-rate cells and modules.

11.0% Stable Efficiency on Large Area, Encapsulated a-Si:H and a-SiGe:H based Multijunction Solar Cells Using HF Technology

ABSTRACTWe report on the investigation of large area a-Si:H/a-SiGe:H double-junction and a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells prepared by our proprietary High Frequency (HF) glow discharge technique. For investigative purposes, we initially used the simpler double-junction structure. We studied the effect of: (1) Ge content, (2) cell thickness, and (3) SiH4 and GeH4 gas flow on the light-induced degradation of the solar cells. Our results show that the double-junction cells with different Ge concentration have open-circuit voltage (Voc) in the range of 1.62-1.75 V. Voc exhibits a flat plateau in the range of 1.65-1.72 V for both initial and stabilized states. The light-induced degradation for cells in this range of Voc is insensitive to the Ge content. In terms of thickness dependence of the intrinsic layers, we found that the initial efficiency increases with cell thickness in the thickness range 2000-4000 Å. However, light-induced degradation increases with increasing thickness. Consequently, the stabilized efficiency is invariant with cell thickness in the thickness range studied. The results of SiH4 and GeH4 gas flow on cell characteristics demonstrate that the deposition rate decreases by only 20% when the active gas flow is reduced to 0.25 times standard flow. The initial and stabilized efficiencies are similar. The information gleaned from the study was used to fabricate high efficiency, large area (~464 cm2) double- and triple-junction solar cells. The highest stable efficiency, as measured by NREL, was 9.8% and 11.0% for the double- and triple-junction structures, respectively.

Wall conditioning towards the utilization in ITER

Wall conditioning provides an effective means for reducing both impurities and recycling from the plasma surrounding surface. A wide variety of techniques have been developed during the last few decades for conditioning the plasma facing surface. With the presence of magnetic fields, electron cyclotron resonant (ECR) and ion cyclotron resonant (ICR) discharge cleaning techniques have been explored, which could be used for next generation superconducting magnetic confined devices, such as ITER. Efforts have been made on the application of ICR conditioning on many devices and significant progress has been made. A new and simple method for future wall conditioning, high frequency glow discharge cleaning (HF-GDC), has been developed. HF-GDC operates in the presence of strong magnetic field (0.5–2T) at frequencies of 20–100kHz stably for a wide range of gas pressures. In this paper, all these techniques are reviewed and their proper application in ITER are discussed.

High efficiency large area a‐SiGe:H based multi‐junction solar cells using MVHF

AbstractWe have developed high efficiency large area a‐Si:H and a‐SiGe:H multi‐junction solar cells using a Modified Very High Frequency (MVHF) glow discharge process. We investigated a‐SiGe:H deposition rate dependence of cell performance, and optimized MVHF a‐SiGe:H process at a deposition rate 2‐4 times that of a typical RF deposition. We conducted a comparative study for different cell structures, and compared the initial and stable performance and light‐induced degradation of solar cells made using MVHF and RF techniques. In additon to high initial efficiency, the MVHF cells also exhibit superior light stability, showing <10% degradation after 1000 hour of one‐sun light soaking at 50 °C. We also studied light‐induced defect level and hydrogen evolution characteristics of MVHF deposited a‐SiGe:H films and compared them with the RF deposited films (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High Efficiency Hydrogenated Nanocrystalline Silicon Solar Cells Deposited at High Rates

AbstractWe report recent progress on hydrogenated nanocrystalline silicon (nc-Si:H) solar cells prepared at different deposition rates. The nc-Si:H intrinsic layer was deposited, using a modified very high frequency (MVHF) glow discharge technique, on Ag/ZnO back reflectors (BRs). The nc-Si:H material quality, especially the evolution of the nanocrystallites, was optimized using hydrogen dilution profiling. First, an initial active-area efficiency of 10.2% was achieved in a nc-Si:H single-junction cell deposited at ~5 Å/s. Using the improved nc-Si:H cell, we obtained 14.5% initial and 13.5% stable active-area efficiencies in an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure. Second, we achieved a stabilized total-area efficiency of 12.5% using the same triple-junction structure but with nc-Si:H deposited at ~10 Å/s; the efficiency was measured at the National Renewable Energy Laboratory (NREL). Third, we developed a recipe using a shorter deposition time and obtained initial 13.0% and stable 12.7% active-area efficiencies for the same triple-junction design.

High Efficiency Large Area a-Si:H and a-SiGe:H Multi-junction Solar Cells Using MVHF at High Deposition Rate

AbstractWe have developed high efficiency large area a-Si:H and a-SiGe:H multi-junction solar cells using a Modified Very High Frequency (MVHF) glow discharge process. We conducted a comparative study for different cell structures, and compared the initial and stable performance and light-induced degradation of solar cells made using MVHF and RF techniques. Besides high efficiency, the MVHF cells also demonstrate superior light stability, showing <10% degradation after 1000 hour of one-sun light soaking at 50 °C. We also studied light-induced defect level and hydrogen evolution characteristics of MVHF deposited a-SiGe:H films and compared them with the RF deposited films.

Correlation of Hydrogen Dilution Profiling to Material Structure and Device Performance of Hydrogenated Nanocrystalline Silicon Solar Cells

ABSTRACTWe present a systematic study on the correlation of hydrogen dilution profiles to structural properties materials and solar cell performance in nc-Si:H solar cells. We deposited nc-Si:H single-junction solar cells using a modified very high frequency (VHF) glow discharge technique on stainless steel substrates with various profiles of hydrogen dilution in the gas mixture during deposition. The material properties were characterized using Raman spectroscopy, X-TEM, AFM, and C-AFM. The solar cell performance correlates well with the material structures. Three major conclusions are made based on the characterization results. First, the optimized nc-Si:H material does not show an incubation layer, indicating that the seeding layer is well optimized and works as per design. Second, the nanocrystalline evolution is well controlled by hydrogen dilution profiling in which the hydrogen dilution ratio is dynamically reduced during the intrinsic layer deposition. Third, the best nc-Si:H single-junction solar cell was made using a proper hydrogen dilution profile, which caused a nanocrystalline distribution close to uniform throughout the thickness, but with a slightly inverse nanocrystalline evolution. We have used the optimized hydrogen dilution profiling and improved the nc-Si:H solar cell performance significantly. As a result, we have achieved an initial active-area cell efficiency of 9.2% with a nc-Si:H single-junction structure, and 15.4% with an a-Si:H/a-SiGe:H/nc-Si:H triple-junction solar cell structure.

Study of Large Area a-Si:H and nc-Si:H Based Multijunction Solar Cells and Materials

ABSTRACTSolar cells based on hydrogenated nanocrystalline silicon (nc-Si:H) have demonstrated significant improvement in the last few years. From the standpoint of commercial viability, good quality nc-Si:H films must be deposited at a high rate. In this paper, we present the results of our investigations on obtaining high quality nc-Si:H and a-Si:H films and solar cells over large areas using high deposition rate. We have employed the modified very high frequency (MVHF) glow discharge technique to realize high-rate deposition. Modeling studies were conducted to attain good spatial uniformity of electric field over a large area (15”×1”) MVHF cathode for nc-Si:H deposition. A comparative study has been carried out between the RF and MVHF plasma deposited a-Si:H and nc-Si:H single-junction and a-Si:H/nc-Si:H double-junction solar cells. By optimizing the nc-Si:H cell and the tunnel/recombination junctions, we have obtained an initial aperture-area (460 cm2) efficiency of 11.9% for a-Si:H/nc-Si:H double-junction cells using conventional RF (13.56 MHz) plasma deposition. The deposition rate was 3 Å/sec. Results on solar cells made with MVHF will also be presented.