Argon-oxygen Plasma Research Articles

Fracture Resistance, Surface Roughness, and Microtensile Bond Strength of Monolithic Zirconia to Resin Cements after Plasma Treatment.

Objectives: This study aimed to assess the effect of surface treatment with plasma on surface roughness (SR) and fracture resistance (FR) of monolithic zirconia, and its microtensile bond strength (MTBS) to resin cements. Materials and Methods: This in vitro, experimental study was conducted on 40 monolithic zirconia crowns for FR test, 100 zirconia rods for MTBS test, and 40 zirconia blocks for profilometry. According to the surface treatment type, the samples were randomly assigned to 4 groups of (I) control (no surface treatment), (II) argon-oxygen plasma (AOP), (III) argon plasma (AP), and (IV) sandblasting (SB). FR of crowns and MTBS of zirconia rods to Allcem Dual and Panavia SA resin cements were measured by a universal testing machine, surface texture was evaluated by atomic force microscopy (AFM), and SR was measured by a profilometer. Data were analyzed by one-way and two-way ANOVA, Tukey's test, and independent t-test (alpha=0.05). Results: There was a significant difference in SR among the groups (P=0.003). The AP group had significantly lower SR than other groups (P=0.01). FR was not significantly different among the four groups. The MTBS in the SB and AOP groups was significantly higher than that in the control and AP groups for both resin cements. MTBS was not significantly different between the two resin cements within each group. Conclusion: None of the surface treatments affected the FR of zirconia crowns. AOP and sandblasting techniques increased the MTBS of zirconia to resin cements with unnoticeable change in SR.

Frequency-dependent electron power absorption mode transitions in capacitively coupled argon-oxygen plasmas

Phase Resolved Optical Emission Spectroscopy (PROES) measurements combined with 1d3v Particle-in-Cell/Monte Carlo Collisions simulations are performed to investigate the excitation dynamics in low-pressure capacitively coupled plasmas (CCPs) in argon-oxygen mixtures. The system used for this study is a geometrically symmetric CCP reactor operated in a 70% Ar-30% O2 mixture at 120 Pa, applying a peak-to-peak voltage of 350 V, with a wide range of driving RF frequencies (2 MHz ⩽f⩽ 15 MHz). The measured and calculated spatio-temporal distributions of the electron impact excitation rates from the Ar ground state to the Ar 2p1 level show good qualitative agreement. The distributions show significant frequency dependence, which is generally considered to be predictive of transitions in the dominant discharge operating mode. Three frequency ranges can be distinguished, showing distinctly different excitation characteristics: (i) in the low frequency range ( f⩽ 3 MHz), excitation is strong at the sheaths and weak in the bulk region; (ii) at intermediate frequencies (3.5 MHz ⩽f⩽ 5 MHz), the excitation rate in the bulk region is enhanced and shows striation formation; (iii) above 6 MHz, excitation in the bulk gradually decreases with increasing frequency. Boltzmann term analysis was performed to quantify the frequency-dependent contributions of the Ohmic and ambipolar terms to the electron power absorption.

Etching of a fluoropolymer coating synthesized by the hot wire chemical vapor deposition method in a low-frequency induction discharge plasma

The process of plasma etching for the formation of a biphilic pattern in a continuous homogeneous fluoropolymer coating on a copper substrate is studied. Argon or oxygen plasma of low frequency ferromagnetic amplified induction discharge is used to etch a fluoropolymer coating. Plasma etching was carried out through a mask with parallel slits. The etching rate in argon plasma was 10 nm/min, the etching rate in oxygen plasma was 60 nm/min. Biphilic surfaces were obtained, consisting of fluoropolymer strips on a copper surface. It has been shown that when using both argon plasma and oxygen plasma, it is possible to create biphilic surfaces by etching a continuous homogeneous fluoropolymer coating through a mask. Moreover, oxygen plasma is better suited for this because it has a higher etching rate and weakly changes the wettability of the surface.

Plasma Anneal As a Stress Control Method in Low Temperature Al2O3 ALD Coatings

The control of mechanical physical stress is an important requirement in a variety of applications, such as flexible electronics or thick optical coatings where film stress can cause delamination. Traditionally, in thermal ALD it has been difficult to control the stress. Al2O3 deposited at low temperature is consistently found to have a tensile stress level in the range of a 300 to 450 MPa ( refs 1-3). It is well established that In magnetron sputtering , film stress can be controlled straightforwardly using the Argon pressure during deposition, as this affects the level of bombardment of the growing film with energetic particles.Paranjpe et al ( ref 1) have demonstrated that the use of a plasma anneal leads to densification and transition of the stress from tensile to compressive. The process consists of a sequence of deposition of a thin layer ( e.g. 5 nm) by thermal ALD, followed by exposure to a low energy plasma. The atomic displacements caused by low energy ions from the plasma tend to lead to filling of nanoscopic voids and point defects, thus releasing tensile stress.In this presentation, we will review an in depth study of the effect of various process parameters on the ability of a capacitively coupled in-situ plasma anneal to control stress. The following parameters will be reviewed: Gas composition: Argon plasmas, Oxygen plasmas and Argon oxygen mixtures are compared. Gas Pressure: The effect of gas pressure on plasma characteristics and the resulting modification of the coating is studied RF Power: RF Power was varied between 0 and 300 W ( 1.32 W/cm2) Plasma duration : The duration of the plasma treatment was varied from 0 to 60 seconds.A process window was identified where the plasma anneal can be used as an effective, controllable tool to reduce stress in the coatings. This is illustrated in fig. 1, which shows the substrate warpage (“bow”) observed in 75 mm thick PET foils with a 50 nm Al2O3 coating deposited at 90 °C. It can be seen that the untreated coating (0 sec plasma) has a bow corresponding to a tensile stress of 370 MPa, in accordance with literature values. As the plasma anneal time increases, the stress value decreases. Applying a 60 sec plasma every 5 nm allows to deposit a virtually stress free coating. Simultaneously with the stress reduction, an increase of the optical index and a slight reduction of the thickness are observed, consistent with a densification of the coating.

Multi-Oxidant Environment as a Suicidal Inhibitor of Myeloperoxidase.

Tissue inflammation drives the infiltration of innate immune cells that generate reactive species to kill bacteria and recruit adaptive immune cells. Neutrophil activation fosters the release of myeloperoxidase (MPO) enzyme, a heme-containing protein generating hypochlorous acid (HOCl) from hydrogen peroxide (H2O2) and chloride ions. MPO-dependent oxidant formation initiates bioactive oxidation and chlorination products and induces oxidative post-translational modifications (oxPTMs) on proteins and lipid oxidation. Besides HOCl and H2O2, further reactive species such as singlet oxygen and nitric oxide are generated in inflammation, leading to modified proteins, potentially resulting in their altered bioactivity. So far, knowledge about multiple free radical-induced modifications of MPO and its effects on HOCl generation is lacking. To mimic this multi-oxidant microenvironment, human MPO was exposed to several reactive species produced simultaneously via argon plasma operated at body temperature. Several molecular gas admixes were used to modify the reactive species type profiles generated. MPO was investigated by studying its oxPTMs, changes in protein structure, and enzymatic activity. MPO activity was significantly reduced after treatment with all five tested plasma gas conditions. Dynamic light scattering and CD-spectroscopy revealed altered MPO protein morphology indicative of oligomerization. Using mass spectrometry, various oxPTMs, such as +1O, +2O, and +3O, were determined on methionine and cysteine (Cys), and -1H-1N+1O was detected in asparagine (Asp). The modification types identified differed between argon-oxygen and argon-nitrogen plasmas. However, all plasma gas conditions led to the deamidation of Asp and oxidation of Cys residues, suggesting an inactivation of MPO due to oxPTM-mediated conformational changes.

Influence of exposure of customized dental implant abutments to different cleaning procedures: an in vitro study using AI-assisted SEM/EDS analysis

PurposeDental implant abutments are defined as medical devices by their intended use. Surfaces of custom-made CAD/CAM two-piece abutments may become contaminated during the manufacturing process in the dental lab. Inadequate reprocessing prior to patient care may contribute to implant-associated complications. Risk-adapted hygiene management is required to meet the requirements for medical devices.MethodsA total of 49 CAD/CAM-manufactured zirconia copings were bonded to prefabricated titanium bases. One group was bonded, polished, and cleaned separately in dental laboratories throughout Germany (LA). Another group was left untreated (NC). Five groups received the following hygiene regimen: three-stage ultrasonic cleaning (CP and FP), steam (SC), argon–oxygen plasma (PL), and simple ultrasonic cleaning (UD). Contaminants were detected using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) and segmented and quantified using interactive machine learning (ML) and thresholding (SW). The data were statistically analysed using non-parametric tests (Kruskal–Wallis test, Dunn’s test).ResultsSignificant differences in contamination levels with the different cleaning procedures were found (p ≤ 0.01). The FP–NC/LA groups showed the most significant difference in contamination levels for both measurement methods (ML, SW), followed by CP–LA/NC and UD–LA/NC for SW and CP–LA/NC and PL–LA/NC for ML (p ≤ 0.05). EDS revealed organic contamination in all specimens; traces of aluminum, silicon, and calcium were detected.ConclusionsChemothermal cleaning methods based on ultrasound and argon–oxygen plasma effectively removed process-related contamination from zirconia surfaces. Machine learning is a promising assessment tool for quantifying and monitoring external contamination on zirconia abutments.Graphical

Low Temperature Wafer Bonding of Silicon Carbide/Aluminum Nitride

Because of the wide energy gap material properties and high compatibility with existing silicon material processing, silicon carbide (SiC) has become the preferred material for power management chips that have been used in electric vehicles. On the other hand, aluminum nitride (AlN) material has become the first choice for carrying wafers due to its high strain-resistant mechanical properties, strong dielectric coefficient, excellent thermal conductivity, and high etching resistance. In this study, the surface chemistry of silicon carbide was changed into an AlN-based material to perform wafer bonding processing to develop low-temperature bonding technology for silicon carbide/aluminum nitride materials. We found through experiments that it is quite difficult for a SiC wafer to bond with an AlN wafer even if the surfaces ofthe SiC wafer and the AlN wafer are subjected to conventional surface activation treatment using oxygen plasma or argon plasma. The possible reason is that although the surface of the SiC wafer is bombarded by oxygen or argon plasmas to generate some dangling bonds, the chemical properties of Si-C and Al-N, such as electronegativity, make it difficult to generate chemical bonds between the matching surfaces of SiC/AlN. Through a material modification technology, a high-temperature sputtering method is used to make highly active AlN clusters sputtered from the target directly bond with SiC and finally form a thin AlN layer that strongly adheres to the surface of the SiC wafer. And then through the bonding of AlN/AlN homogeneous materials, although the surface roughness measurement (RMS) cannot satisfy the condition of being less than 5 angstroms for wafer bonding, the goal of low-temperature bonding can be achieved by capillary bonding. Therefore, the SiC surface is changed into an AlN-based thin layer by high-temperature sputtering, which can further chemically bond with the AlN wafer surface by capillary bonding to achieve the low-temperature bonding of SiC/AlN, as shown in Figure 1.Reference1. Shao-Ming Nien, Jian-Long Ruan, Yang-Kuao Kuo, and Benjamin Tien-Hsi Lee, Low-temperature rough-surface wafer bonding with aluminum nitride ceramics implemented by capillary and oxidation actions, Ceramics International, Volume 48, Issue 6, 2022 Figure 1

Chemical and Electrical Aspects of Homogeneous Discharge in an Argon-Oxygen Mixture for Ozone Generation

In this work, a dielectrics barriers discharge (DBD) in an Ar/O<sub>2</sub> gas mixture excited with sinusoidal applied voltage for ozone generation has been investigated in order to draw attention to the important role of the kinetic scheme of this gas mixture in the plasma discharge. The adopted model was based on argon-oxygen plasma chemistry, the external circuit, and the Boltzmann equations. This approach predicts the optimal operating conditions and can also describes the chemical and electrical aspects of the DBD reactor. The kinetic scheme of an Ar/O<sub>2</sub> gas mixture takes into account 15 species regrouped in 123 reactions. The time evolutions of kinetic and electric characteristics of plasma discharges, and the effect of the main discharge parameters on DBD behavior and ozone efficiency are analyzed and discussed.

Unraveling the Mechanism of the 150-Fold Photocurrent Enhancement in Plasma-Treated 2D TMDs.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are increasingly investigated for applications such as optoelectronic memories, artificial neurons, sensors, and others that require storing photogenerated signals for an extended period. In this work, we report an environment- and gate voltage-dependent photocurrent modulation method of TMD monolayer-based devices (WS2 and MoS2). To achieve this, we introduce structural defects using mild argon–oxygen plasma treatment. The treatment leads to an extraordinary over 150-fold enhancement of the photocurrent in vacuum along with an increase in the relaxation time. A significant environmental and electrostatic dependence of the photocurrent signal is observed. We claim that the effect is a combined result of atomic vacancy introduction and oxide formation, strengthened by optimal wavelength choice for the modified surface. We believe that this work contributes to paving the way for tunable 2D TMD optoelectronic applications.

Influence of Plasma Surface Treatment of Polyimide on the Microstructure of Aluminum Thin Films

The effects of plasma treatment of polyimide substrates on the texture and grain size distribution of aluminum thin films were studied. Oxygen-argon plasma treatment increased the average grain size and enhanced the (111) film texture. For short oxygen-argon plasma treatment times, the deposited Al films showed a (111) texture with a bimodal grain structure and even a {111}<112¯> type in-plane texture. The preferential nucleation and grain growth of (111) grains are discussed in terms of the interface energy anisotropy.

Controlled Deposition of Nanostructured Hierarchical TiO2 Thin Films by Low Pressure Supersonic Plasma Jets.

Plasma-assisted supersonic jet deposition (PA-SJD) is a precise technique for the fabrication of thin films with a desired nanostructured morphology. In this work, we used quadrupole mass spectrometry of the neutral species in the jet and the extensive characterization of TiO2 films to improve our understanding of the relationship between jet chemistry and film properties. To do this, an organo–metallic precursor (titanium tetra–isopropoxide or TTIP) was first dissociated using a reactive argon–oxygen plasma in a vacuum chamber and then delivered into a second, lower pressure chamber through a nozzle. The pressure difference between the two chambers generated a supersonic jet carrying nanoparticles of TiO2 in the second chamber, and these were deposited onto the surface of a substrate located few centimeters away from the nozzle. The nucleation/aggregation of the jet nanoparticles could be accurately tuned by a suitable choice of control parameters in order to produce the required structures. We demonstrate that high-quality films of up to several µm in thickness and covering a surface area of few cm2 can be effectively produced using this PA-SJD technique.

Improving Device Characteristics of Dual-Gate IGZO Thin-Film Transistors with Ar-O2 Mixed Plasma Treatment and Rapid Thermal Annealing.

In this study, high-performance indium–gallium–zinc oxide thin-film transistors (IGZO TFTs) with a dual-gate (DG) structure were manufactured using plasma treatment and rapid thermal annealing (RTA). Atomic force microscopy measurements showed that the surface roughness decreased upon increasing the O2 ratio from 16% to 33% in the argon–oxygen plasma treatment mixture. Hall measurement results showed that both the thin-film resistivity and carrier Hall mobility of the Ar–O2 plasma–treated IGZO thin films increased with the reduction of the carrier concentration caused by the decrease in the oxygen vacancy density; this was also verified using X-ray photoelectron spectroscopy measurements. IGZO thin films treated with Ar–O2 plasma were used as channel layers for fabricating DG TFT devices. These DG IGZO TFT devices were subjected to RTA at 100 °C–300 °C for improving the device characteristics; the field-effect mobility, subthreshold swing, and ION/IOFF current ratio of the 33% O2 plasma–treated DG TFT devices improved to 58.8 cm2/V·s, 0.12 V/decade, and 5.46 × 108, respectively. Long-term device stability reliability tests of the DG IGZO TFTs revealed that the threshold voltage was highly stable.

Strength and flexibility of lithium disilicate bonded to polyetherketoneketone

Statement of problemPolyetherketoneketone (PEKK) is a high-performance polymer gaining popularity in dentistry for the fabrication of crowns, fixed partial dentures, removable partial denture frameworks, and frameworks for implant-supported fixed complete dentures. Despite a lack of performance data, lithium disilicate crowns have been bonded to retentive elements in PEKK frameworks. PurposeThe purpose of this in vitro study was to compare the bond strengths and flexibility of lithium disilicate to PEKK or zirconia. Material and methodsForty-five PEKK, 15 zirconia, and 60 lithium disilicate beam-shaped specimens (12.5×2×2 mm) were fabricated. The ends of the PEKK beams were subjected to 3 different surface treatments before the application and light polymerization of a primer: 50-μm aluminum oxide airborne-particle abrasion, nonthermal air plasma, and argon-oxygen plasma. The zirconia specimen bonding surfaces were prepared with 50-μm aluminum oxide airborne-particle abrasion and the application of primer. Lithium disilicate specimens were etched with 4.5% hydrofluoric acid, and primer was applied. The lithium disilicate specimens were luted with an adhesive resin cement to the PEKK and zirconia specimens by using light-activated and chemically activated polymerization. Fifteen monolithic specimens of PEKK, lithium disilicate, and zirconia (25×2×2 mm) were also fabricated. All specimens were incubated overnight in 100% humidity before testing. Bonded and monolithic specimens were loaded in a universal testing machine, and 4-point bend tests were conducted until failure (n=15). The flexural modulus and strength were calculated and statistically analyzed with 1-way analysis of variance and Student-Newman-Keuls post hoc tests (α=.05). ResultsAll bonded specimens failed at the adhesive interface. The zirconia-lithium disilicate bond strength was approximately twice that of the strongest group of PEKK (airborne-particle abrasion group) bonded to lithium disilicate (42 ±12 MPa and 24 ±13 MPa, respectively) and was approximately 9 times more rigid (71 ±19 GPa and 8 ±2 GPa, respectively). Monolithic PEKK fractured at 238 ±22 MPa, monolithic zirconia at 771 ±128 MPa, and monolithic lithium disilicate at 173 ±26 MPa. Monolithic PEKK was approximately 30 times more flexible than monolithic zirconia (6 ±1 GPa and 178 ±16 GPa, respectively). All values were statistically significantly different (P<.05), except for the bond strength between lithium disilicate and PEKK treated with airborne-particle abrasion and nonthermal air plasma and the flexural moduli of PEKK to lithium disilicate. ConclusionsBond strength between PEKK and lithium disilicate was significantly weaker than that between zirconia and lithium disilicate. Monolithic PEKK was significantly more flexible than monolithic zirconia.

Effect of different types of substrate surface treatments on the graphene device performance

Graphene–substrate interface is very crucial for analyzing graphene device performance. In this article, we have shown how the graphene device performance got affected because of different types of substrate surface treatment techniques used before graphene transfer. For fabrication of graphene devices, monolayer chemical vapor deposition (CVD) graphene was transferred onto SiO2 grown thermally on Si substrate. Forming gas annealed SiO2/Si shows better device performance as compared with as‐grown SiO2 on Si substrate. A further effect of oxygen plasma and argon plasma cleaning of SiO2 surface before graphene transfer was investigated. Forming gas annealing improves the performance and plasma treatment degrade the graphene devices' performance.

Structural, electrical and gas-sensitive properties of Cr2O3 thin films

Abstract Cr2O3 thin films were synthesized by RF magnetron sputtering of a Cr target in an oxygen-argon plasma. The effect of annealing temperature on the structural, electrical, and gas-sensitive properties of the Cr2O3 thin films was studied. According to AFM, SEM, XRD, EDX, XPS, optical spectroscopy and electrical measurements the annealed films were characterized by a polycrystalline structure, high stoichiometry, p-type conductivity and a band gap energy of 3.3 ± 0.2 eV. An increase in the annealing temperature from 350 to 450 °C leads to formation of Cr2O3 grains with a diameter from 30 to 130 nm and to a significant increase in the film electrical resistance. Cr2O3 demonstrated sensitivity to NO2, H2, NH3, vapors of acetone and toluene in the heating temperature range of 25–200 °C. Changing the annealing temperature allows to control the sensitivity of the films to certain gases. Thus, Cr2O3 thin films subjected to annealing at a temperature of 450 °C were characterized by a high response to NH3, while those annealed at a temperature of 400 °C – to toluene vapors and that annealed at 350 °C – to NO2 and acetone vapors. A qualitative model of the sensory effect was proposed.

Argon and Argon-Oxygen Plasma Surface Modification of Gelatin Nanofibers for Tissue Engineering Applications.

In the present study, we developed a novel approach for functionalization of gelatin nanofibers using the plasma method for tissue engineering applications. For this purpose, tannic acid-crosslinked gelatin nanofibers were fabricated with electrospinning, followed by treatment with argon and argon–oxygen plasmas in a vacuum chamber. Samples were evaluated by using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle (CA) and X-ray diffraction (XRD). The biological activity of plasma treated gelatin nanofibers were further investigated by using fibroblasts as cell models. SEM studies showed that the average diameter and the surface morphology of nanofibers did not change after plasma treatment. However, the mean surface roughness (RMS) of samples were increased due to plasma activation. ATR-FTIR spectroscopy demonstrated several new bands on plasma treated fibers related to the plasma ionization of nanofibers. The CA test results stated that the surface of nanofibers became completely hydrophilic after argon–oxygen plasma treatment. Finally, increasing the polarity of crosslinked gelatin after plasma treatment resulted in an increase of the number of fibroblast cells. Overall, results expressed that our developed method could open new insights into the application of the plasma process for functionalization of biomedical scaffolds. Moreover, the cooperative interplay between gelatin biomaterials and argon/argon–oxygen plasmas discovered a key composition showing promising biocompatibility towards biological cells. Therefore, we strongly recommend plasma surface modification of nanofiber scaffolds as a pretreatment process for tissue engineering applications.

Bioactive effects of nonthermal argon-oxygen plasma on inorganic bovine bone surface

As a commonly used bone substitute material in the clinic, inorganic bovine bone has the characteristics of osteoconduction but not osteoinduction. This study aimed to treat inorganic bovine bone using nonthermal argon-oxygen plasma (NTAOP) to obtain greater bioreactivity for enhancing adhesion, proliferation and differentiation of mouse preosteoblast MC3T3-E1 cells. In this study, inorganic bovine bone was activated by NTAOP, and the surface characteristics were analyzed. MC3T3-E1 cells were then seeded onto the surface of inorganic bovine bone. Cell morphology, proliferation and osteogenic differentiation were examined. There was no obvious change in the surface morphology of specimens between the two groups. Regarding the elemental composition of the material, the amount of surface carbon was reduced, whereas oxygen, phosphorus and calcium levels were increased in the NTAOP group. Further studies showed that the NTAOP groups performed better than their untreated counterparts in terms of supporting cell proliferation and differentiation. Inorganic bovine bone treated with NTAOP can promote preosteoblast adhesion, proliferation and differentiation.

Reactively sputtered cobalt oxide coatings for solar selective absorber applications

Using a simple one-step sputtering procedure, we successfully deposited cobalt oxide thin films on glass and copper substrates in argon-oxygen plasmas. The reactive radio-frequency sputter deposition was carried out at a fixed power of 200 W, and in gas mixtures with various oxygen rates from 10% to 50%. Atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and emissivity measurements were used to study morphological, chemical and thermal radiation properties of elaborated Co3O4 coatings. The obtained cobalt oxide layers were found to be stable and highly adherent for 10%, 30% and 40% oxygen rates. The deposited Co3O4 thin films exhibit very promising thermal properties with spectral selectivities between 16.4 and 26.24. The reactive RF sputtering at 200 W in the 40%–O2-gas mixture allowed depositing cobalt oxide layers with optimal surface morphology and enhanced solar absorptivity of about 0.96.

Optical, structural and electrical characterization of pure ZnO films grown on p-type Si substrates by radiofrequency magnetron sputtering in different atmospheres

ZnO films were grown on p-type Si substrates by radio-frequency magnetron sputtering of ZnO target in pure argon or mixed argon-oxygen plasma and were investigated using atomic force microscopy, spectroscopic ellipsometry, Fourier-transformed infrared spectroscopy and electrical methods. It was observed that the films grown in argon plasma had large surface roughness which increases with the rise of deposition time. The lateral size of ZnO columns showed similar dependence on deposition parameters as the roughness. Contrary to this, the films produced in argon-oxygen plasma were found to be smoother and denser having thinner ZnO columns. These films also demonstrated an abrupt absorption band-gap edge that is the evidence of better crystalline quality of these films (the lower number of native point and elongated defects). Plasmon-phonon interaction in ZnO films as well as the effect of the plasmon system of Si substrate on this interaction was considered. The theoretical approach used for the fitting of specular infrared reflection spectra allowed determining concentration and mobility of free carriers as well as conductivity of ZnO films. It was found that the films grown in pure argon plasma demonstrated a higher concentration and a smaller mobility of free carriers in the comparison with the corresponding parameters of the films grown in argon-oxygen mixed plasma. The direct resistivity measurements show the essentially higher values compared with the values estimated from IR reflection spectra. The possible reasons of this difference are discussed. The utility of infrared reflection spectroscopy for the non-destructive analysis of electro-physical properties of polycrystalline films was shown.

The Planar Multipole Resonance Probe: A Minimally Invasive Monitoring Concept for Plasma-Assisted Dielectric Deposition Processes

In this article, a novel minimally invasive approach to plasma monitoring in the challenging environment of dielectric deposition processes based on the planar multipole resonance probe (pMRP) is presented. By placing the sensor on the plasma-remote side of a dielectric substrate to be coated, perturbations of the process due to its presence can be significantly reduced. Since the electric field of the sensor is able to penetrate dielectric layers, a plasma supervision through the substrate is enabled. To investigate the effect of increasing coating thicknesses on the measurement performance for a broad spectrum of materials and plasma conditions, the results of extensive 3-D full-wave simulations performed with CST Microwave Studio are evaluated. Finally, real-time monitoring results of an argon-oxygen plasma during a sputter deposition with aluminum oxide on a polyethylene terephthalate (PET) film substrate together with a comparison to external process parameters are presented. The results demonstrate both the applicability of the proposed concept and its insensitivity to additional dielectric coatings.