Radical Flux Research Articles

Transformer coupled toroidal wave-heated remote plasma sources operating in Ar/NF3 mixtures

Remote plasmas are used in semiconductor device manufacturing as sources of radicals for chamber cleaning and isotropic etching. In these applications, large fluxes of neutral radicals (e.g. F, O, Cl, H) are desired with there being negligible fluxes of potentially damaging ions and photons. One remote plasma source (RPS) design employs toroidal, transformer coupling using ferrite cores to dissociate high flows of moderately high pressure (up to several Torr) electronegative gases. In this paper, results are discussed from a computational investigation of moderate pressure, toroidal transformer coupled RPS sustained in Ar and Ar/NF3 mixtures. Operation of the RPS in 1 Torr (133 Pa) of argon with a power of 1.0 kW at 0.5 MHz and a single core produces a continuous toroidal plasma loop with current continuity being maintained dominantly by conduction current. Operation with dual cores introduces azimuthal asymmetries with local maxima in plasma density. Current continuity is maintained by a mix of conduction and displacement current. Operation in NF3 for the same conditions produces essentially complete NF3 dissociation. Electron depletion as a result of dissociative attachment of NF3 and NF x fragments significantly alters the discharge topology, confining the electron density to the downstream portion of the source where the NF x density has been lowered by this dissociation.

Fabrication of high aspect ratio AlN nanopillars by top-down approach combining plasma etching and wet etching

This study proposes a top-down approach for fabricating high aspect ratio AlN pillars with m-oriented nonpolar sidewalls, which will serve as the first building block for the fabrication of core-shell UV-LEDs. Such structures are achieved through a two-step process, combining a chlorine plasma etching, followed by a wet chemical etching with KOH. In this work, the mechanisms driving the AlN etching in chlorine plasma are discussed. In particular, we highlight the impact of the ratio between ion flux and radical flux on AlN etch rates, pillar profiles, and crystal orientation-dependent etching. We also identify two mechanisms of passivation layer formation on the pillar sidewalls that contribute to the pattern slope: redeposition of the carrier wafer etch by-products and Aluminium line of sight redeposition, both phenomena are also driven by the ionic bombardment. Low ionic bombardment (either low ion over radical flux ratio or low ion energy) has been identified as plasma conditions allowing the patterning of anisotropic AlN pillars but with the formation of a-nonpolar facets. Due to the inability to obtain m-oriented sidewalls using Cl2 plasma etching alone, we show that the use of a KOH wet etching treatment allows verticalizing the pillars and revealing smooth m-facets on the pillars’ sidewalls if suitable m-oriented hard mask is used. In this wet etching step, we highlight the key role played by the hard mask and its initial shape during the wet etching if straight and m-oriented pillars are desired.

Enhanced Mechanistic Understanding Through the Detection of Radical Intermediates in Organic Reactions.

Two applications of a radical trap based on a homolytic substitution reaction (SH2') are presented for the trapping of short-lived radical intermediates in organic reactions. The first example is a photochemical cyanomethylation catalyzed by a Ru complex. Two intermediate radicals in the radical chain propagation have been trapped and detected using mass spectrometry (MS), along with the starting materials, products and catalyst degradation fragments. Although qualitative, these results helped to elucidate the reaction mechanism. In the second example, the trapping method was applied to study the radical initiation catalyzed by a triethylboronoxygen mixture. In this case, the concentration of trapped radicals was sufficiently high to enable their detection by nuclear magnetic resonance (NMR). Quantitative measurements made it possible to characterize the radical flux in the system under different reaction conditions (including variations of solvent, temperature and concentration) where modelling was complicated by chain reactions and heterogeneous mass transfer.

Suppressing substrate oxidation during plasma-enhanced atomic layer deposition on semiconductor surfaces

Plasma-enhanced atomic layer deposition (PE-ALD) is widely employed in microelectronics, energy, and sensing applications. Typically, PE-ALD processes for metal oxides utilize remote inductively coupled plasmas operated at powers of >200 W, ensuring a sufficient flux of oxygen radicals to the growth surface. However, this approach often leads to significant oxidation of chemically sensitive substrates, including most technological semiconductors. Here, we demonstrate that plasma powers as low as 5 W can effectively suppress substrate oxidation while maintaining the structural, optical, and electronic quality of the films. Specifically, we investigate the growth of titanium oxide (TiOx) using two commonly used metalorganic precursors, titanium isopropoxide and tetrakis(dimethylamino)titanium. Films deposited with 5 and 300 W oxygen plasma power are nearly indiscernible from one another, exhibiting significantly lower defect concentrations than those obtained from thermal ALD with H2O. The low plasma power process preserves desired physical characteristics of PE-ALD films, including large optical constants (n > 2.45 at 589 nm), negligible defect-induced sub-bandgap optical absorption (α < 102 cm−1), and high electrical resistivity (>105 Ω cm). Similar behavior, including suppressed interface oxidation and low defect content, is observed on both Si and InP substrates. As an example application of this approach, the assessment of InP/TiOx photocathodes and Si/TiOx photoanodes reveals a significant improvement in the photocurrent onset potential in both cases, enabled by suppressed substrate oxidation during low power PE-ALD. Overall, low power PE-ALD represents a generally applicable strategy for producing high quality metal oxide thin films while minimizing detrimental substrate reactions.

Comparison of distributions of etching rate and calculated plasma parameters in dual-frequency capacitively coupled plasma

Abstract We measured the etching rates of SiO2 and Si in dual-frequency excited CF4 plasma and compared the etching rates with the radical species distribution calculated by plasma simulation. The etching rates of SiO2 and Si at the wafer edge became higher than those at the wafer center, and the etching rate of Si distributed uniformly without bias voltage. In the simulation, the calculation model was calibrated on the basis of the measured (electron density). Assuming that CF3 + contributes to SiO2 and Si etching, and F contributes to Si etching without bias voltage, the radical fluxes flowing into the wafer were calculated by plasma simulation. The fluxes of CF3 + and CF2 became higher at the edge, and the F flux distribution was uniform without the bias voltage. It was shown that the distributions of the etching rate in the experiment and radical flux that contributes to etching in the simulation were in agreement.

OH density, flux and loss probability measurements in a room temperature atmospheric pressure surface discharge by microscopic laser induced fluorescence

Many applications involving atmospheric pressure plasma-substrate interactions are enabled by the large fluxes of short-lived reactive species such as OH radicals to the substrate, nonetheless, the accurate measurement of radical densities and fluxes at substrates at atmospheric pressure has received little attention to date, particularly for surface ionization waves. We report the measurement of the OH density distribution in a surface discharge on a fused silica (quartz) substrate generated by an impinging atmospheric pressure plasma jet in dry and humid helium. The OH density is measured by microscopic laser induced fluorescence with a spatial resolution of 10 µm in the direction perpendicular to the quartz substrate. The measured OH diffusive flux varied for the investigated experimental conditions by almost three orders of magnitude and had a maximum value of 1.7 × 1015 cm−2 s−1. The corresponding surface loss probability of OH on the quartz surface was determined to be ∼0.01. The high spatial resolution was required to accurately resolve the near surface gradient of OH radicals.

Traumatic Brain Injury: Acupuncture Treatment.

Traumatic brain injury (TBI) is a significant cause of morbidity and mortality worldwide. It is estimated that half of the people in the world will experience at least 1 episode of TBI during their lifetimes. While the primary injury to the brain parenchyma is usually irreversible, the secondary effects, which involve cellular dysfunction, derangement of blood flow, and blood-brain barrier changes in ionic flux and elevated levels of free radicals are potentially amenable to treatment. At present, there are no neuroprotective agents in mainstream medicine to interrupt these secondary processes and improve the patient's neurologic outcome. Acupuncture holds promise to fill this gap and scientific evidence to that effect is presented. Sports-related brain injury is discussed in detail.

Molecular dynamics study of SiO2 nanohole etching by fluorocarbon ions

As the sizes of semiconductor devices continue to shrink, the fabrication of nanometer-scale device structures on material surfaces poses unprecedented challenges. In this study, molecular dynamics simulations of CF3+ ion beam etching of SiO2 were performed with carbon masks to form holes with a diameter of 4 nm. It is found that, when the ion energy is sufficiently high and the etching continues, tapered holes are formed by the ion beam etching. This is because the etching under these conditions is essentially due to physical sputtering, so that tapered surfaces having high etching yields appear as the sidewalls and sputtered Si-containing species are redeposited. Furthermore, preferential removal of oxygen from SiO2 surfaces occurs, which leads to the formation of Si-rich sidewall surfaces. It is also found that, with simultaneous irradiation of CF3 radicals, the etching yield of a flat SiO2 surface by energetic CF3+ ion beams can double, but too large a flux of CF3 radicals causes etch stop.

Generation and delivery of free hydroxyl radicals using a remote plasma

We demonstrate a new gas-based generation source using a low power radio frequency driven atmospheric pressure plasma configured to deliver the radical flux into the far effluent region, well away from interference from other plasma factors such as electric fields, currents, and ultraviolet radiation. Using He–H2O gas chemistry isolated from the laboratory air, the plasma generated flux contains and other radicals including, O and HO2 as well as H2O2 which, along with, was found to vary with H2O vapour content and absorbed power density. Peak flux values were 2.3 nmol s−1 and 0.23 nmol s1 for H2O2 and respectively at a distance of 50 mm from the plasma, with 790 ppmv H2O and a power density of ∼108 W m−3. The maximum flux density was 4.5 × 1019 m−2s−1 falling to 1.7 × 1019 m2 s1 at 110 mm, equivalent to generation rates of 74 µM s1 and 28 µM s−1. Despite high recombination rates at the plasma exit, the escaping flux is still significant, indicating a viable delivery capability to downstream targets. Its performance with regard to generation rates compares well with traditional generation techniques such as radiolysis, advanced oxidation processes and enhanced Fenton-chemistry approaches where production rates are sub-µM s−1. Delivering precisely quantifiable fluxes provides new opportunities for scientific studies and technological opportunities in cell biology, atmospheric chemistry, protein unfolding and systematic dose studies for plasma-based and other related potential medical treatments.

Investigation into SiO2 Etching Characteristics Using Fluorocarbon Capacitively Coupled Plasmas: Etching with Radical/Ion Flux-Controlled.

SiO2 etching characteristics were investigated in detail. Patterned SiO2 was etched using radio-frequency capacitively coupled plasma with pulse modulation in a mixture of argon and fluorocarbon gases. Through plasma diagnostic techniques, plasma parameters (radical and electron density, self-bias voltage) were also measured. In this work, we identified an etching process window, where the etching depth is a function of the radical flux. Then, pulse-off time was varied in the two extreme cases: the lowest and the highest radical fluxes. It was observed that increasing pulse-off time resulted in an enhanced etching depth and the reduced etching depth respectively. This opposing trend was attributed to increasing neutral to ion flux ratio by extending pulse-off time within different etching regimes.

Evolution of lithography-to-etch bias in multi-patterning processes

Quantitatively accurate, physics-based, computational modeling of etching and lithography processes is essential for modern semiconductor manufacturing. This paper presents lithography and etch models for a trilayer process in a back end of the line manufacturing vehicle. These models are calibrated and verified against top-down scanning electron microscope (SEM) and cross-sectional SEM measurements. Calibration errors are within 2 nm, while the maximum verification error is less than 3 nm. A fluorocarbon plasma etch of the spin-on-glass (SOG) layer accounts for most of the etch bias present in the process. The tapered profile in the SOG etch step is generated due to the polymerization process by fluorocarbon radicals generated in the plasma. The model predicts a strong correlation between the etch bias in the SOG etch step and the neutral-to-ion flux ratio in the plasma. The second etch step of the flow, which etches the spin-on-carbon (SOC) layer using an H2/N2 plasma, results in a negative etch bias (increase in CDs) for all measured features. The ratio of hydrogen to nitrogen radical fluxes effectively controls the etch bias in this step, with the model predicting an increase in the etch bias from negative to positive values as the H-to-N ratio decreases. The model also indicates an aspect ratio dependent etch rate in the SOG and SOC etch steps, as seen in the etch front evolution in a three-dimensional test feature. The third and final step of the process, SiO2-etch, generates an insignificant etch bias in all the test structures. Finally, the accuracy of the etch simulations is shown to be dependent on the accuracy of the incoming photoresist shapes. Models that consider only the top-down SEM measurement as input and do not account for an accurate photoresist profile, suffered significant errors in the post-etch CD predictions.

Low-Temperature Plasma Diagnostics to Investigate the Process Window Shift in Plasma Etching of SiO2.

As low-temperature plasma plays an important role in semiconductor manufacturing, plasma diagnostics have been widely employed to understand changes in plasma according to external control parameters, which has led to the achievement of appropriate plasma conditions normally termed the process window. During plasma etching, shifts in the plasma conditions both within and outside the process window can be observed; in this work, we utilized various plasma diagnostic tools to investigate the causes of these shifts. Cutoff and emissive probes were used to measure the electron density and plasma potential as indicators of the ion density and energy, respectively, that represent the ion energy flux. Quadrupole mass spectrometry was also used to show real-time changes in plasma chemistry during the etching process, which were in good agreement with the etching trend monitored via in situ ellipsometry. The results show that an increase in the ion energy flux and a decrease in the fluorocarbon radical flux alongside an increase in the input power result in the breaking of the process window, findings that are supported by the reported SiO2 etch model. By extending the SiO2 etch model with rigorous diagnostic measurements (or numerous diagnostic methods), more intricate plasma processing conditions can be characterized, which will be beneficial in applications and industries where different input powers and gas flows can make notable differences to the results.

Molecular dynamics simulation of Si trench etching with SiO2 hard masks

Molecular dynamics simulations were performed to demonstrate nanometer-scale silicon (Si) trench etching with silicon dioxide (SiO2) hard masks by chlorine (Cl+) ion beams possibly with low-energy chlorine (Cl) radicals. Although the sputtering yield of SiO2 is typically much lower than that of Si, the etch rates of SiO2 and Si can be comparable because of the lower Si atomic density of SiO2. This implies that the erosion of the mask can significantly affect etched structures. This study has demonstrated that although the fluxes of incident ions and radicals are uniform in space and constant in time, the individuality of incident ions and radicals causes atomic-scale surface roughness, which cannot be neglected for nanometer-scale etched structures. Furthermore, some transient effects of surface etching, such as initial swelling of the Si surface due to incorporation of Cl atoms and preferential sputtering of oxygen, can affect the profiles of etched structures. The insufficiency of the local mechanical strengths of nanometer-scale materials also enhances their erosion, leading to the formation of nanometer-scale roughness on the sidewalls of masks and etched structures.

Application of a dual-thermopile radical probe to expanding hydrogen plasmas

We compare the performance of a hydrogen radical probe to historic data determined via two-photon absorption laser induced fluorescence using a comparable cascaded arc source under similar operating conditions. This probe has dual heat flux sensors (DHFS) each coated with materials with different catalytic properties for hydrogen atoms. In the ideal situation, the hydrogen radical flux can be deduced based on the difference between the heat loads measured by these two sensors. The influence of DHFS temperature on the performance was also assessed. The experimental results showed measurement errors of <10% could be obtained regardless of the probe temperature during plasma exposures. To convert heat fluxes into atomic fluxes, we calibrated the difference of the recombination coefficients using a vacuum ultraviolet absorption technique, which is more reliable than modeled values based on assumptions or scattered values reported in literature. As a result, we measured the hydrogen plasma and radical parameters at various settings using both a double Langmuir probe and the DHFS. The typical atom flux in the 1022 m−2s−1 range was in good agreement with those obtained using optical techniques. We also observed that the ion and atom fluxes are both sensitive to the background gas pressure. These findings validate application of the DHFS to the cascaded arc source, and could pave the way for optimization of the source performance in the plasma material processing experiments.

Effect of Gas Flow Rate in PECVD of Amorphous Silicon Thin Films for Interface Passivation of Silicon Heterojunction Solar Cells

Precursor gas flow rate variation (30–80 sccm) in the plasma‐enhanced chemical vapor deposition (PECVD) process of intrinsic a‐Si:H layer deposition using SiH4/H2 (equal ratio) plasma is explored and its effect on the i‐a‐Si:H/c‐Si interface passivation is investigated. A window of intermediate gas flow rates is determined for good quality surface passivation of n‐type c‐Si. Maximum effective minority carrier lifetime (τeff) above 1 ms, implied open‐circuit voltage (iVoc) ≈ 710 mV, and low interface defect density (Dit) ≈3.5 × 109 cm−2 eV−1 are obtained at an intermediate gas flow rate. The SiH4:H2 discharge emission characteristics, and the a‐Si:H film characteristics such as hydrogen concentration, film density, optical band gap, and refractive index, are also investigated. To examine the effect of the flow rate variation on the performance of the final device, front‐junction silicon heterojunction solar cells are fabricated on n‐type Si wafers, and ≈17% efficient cells are fabricated with an open‐circuit voltage (Voc) close to 690 mV at an optimized gas flow rate. This study provided information related to the transient plasma instability, SiH4 depletion, secondary reactions in the plasma, and flux of radicals toward the substrate for the film growth with a good level of surface passivation.

Atovaquone: An Inhibitor of Oxidative Phosphorylation as Studied in Gynecologic Cancers.

Simple SummaryThe Warburg effect in cancer cells (high glucose update and lactate release) is an adaptation that is considered a hallmark of most neoplasms. Blocking oxidative phosphorylation is one way to combat carcinogenesis. Atovaquone is a mitochondrial complex III inhibitor. It is currently FDA-approved for the treatment of malaria, and is a well-tolerated, orally available medication. Our laboratory studied the anti-cancer properties of atovaquone in gynecologic cancers. We found that atovaquone slowed ovarian cancer growth in both cell lines and mouse models. Additional anti-cancer effects were seen, such as the reduced proliferation of cancer stem cells and spheroids implanted in mice. Atovaquone inhibited oxygen consumption and ATP production. Metabolic studies showed that atovaquone shifted glycolysis, electronic transport and the citric acid cycle. Our studies provided the mechanistic understanding and preclinical data to support the further investigation of atovaquone’s potential as a cancer therapy for gynecologic cancers.Oxidative phosphorylation is an active metabolic pathway in cancer. Atovaquone is an oral medication that inhibits oxidative phosphorylation and is FDA-approved for the treatment of malaria. We investigated its potential anti-cancer properties by measuring cell proliferation in 2D culture. The clinical formulation of atovaquone, Mepron, was given to mice with ovarian cancers to monitor its effects on tumor and ascites. Patient-derived cancer stem-like cells and spheroids implanted in NSG mice were treated with atovaquone. Atovaquone inhibited the proliferation of cancer cells and ovarian cancer growth in vitro and in vivo. The effect of atovaquone on oxygen radicals was determined using flow and imaging cytometry. The oxygen consumption rate (OCR) in adherent cells was measured using a Seahorse XFe96 Extracellular Flux Analyzer. Oxygen consumption and ATP production were inhibited by atovaquone. Imaging cytometry indicated that the majority of the oxygen radical flux triggered by atovaquone occurred in the mitochondria. Atovaquone decreased the viability of patient-derived cancer stem-like cells and spheroids implanted in NSG mice. NMR metabolomics showed shifts in glycolysis, citric acid cycle, electron transport chain, phosphotransfer, and metabolism following atovaquone treatment. Our studies provide the mechanistic understanding and preclinical data to support the further investigation of atovaquone’s potential as a gynecologic cancer therapeutic.

Iron imbalance in cancer: Intersection of deficiency and overload.

Iron, an essential trace element, plays a complex role in tumour biology. While iron causes cancer clearance through toxic free radical generation, iron‐induced free radical flux also acts as a cancer promoter. These fates majorly guided through cellular response towards pro‐oxidant and antioxidant settings in a tumour microenvironment, designate iron‐induced oxidative stress as a common yet paradoxical factor in pro‐tumorigenesis as well as anti‐tumorigenesis, posing a challenge to laying down iron thresholds favouring tumour clearance. Additionally, complexity of iron's association with carcinogenesis has been extended to iron‐induced ROS's involvement in states of both iron deficiency and overload, conditions identified as comparable, inevitable and significant coexisting contributors as well as outcomes in chronic infections and tumorigenesis. Besides, iron overload may also develop as an unwanted outcome in certain cancer patients, as a result of symptomatic anaemia treatment owed to irrational iron‐restoration therapies without a prior knowledge of body's iron status with both conditions synergistically acting towards tumour aggravation. The co‐play of iron deficiency and overload along with iron's pro‐tumour and antitumour roles with intersecting mechanisms, thus presents an unpredictable regulatory response loop in a state of malignancy. The relevance of iron's thresholds beyond which it proves to be beneficial against tumorigenesis hence becomes questionable. These factors pose a challenge, over establishing if iron chelation or iron flooding acts as a better approach towards antitumour therapies. This review presents a critical picture of multiple contrasting features of iron's behaviour in cancer, leading towards two conditions lying at opposite ends of a spectrum: iron deficiency and overload in chronic disease conditions including cancer, hence, validating the critical significance of diagnosis of patients' iron status prior to opting for subsequent therapies.

Influence of the carrier wafer during GaN etching in Cl2 plasma

In this study, we have performed a thorough characterization of the GaN surface after etching up to 100 nm in Cl2 plasma under various bias voltages and according to the carrier wafer used (Si, SiO2, Si3N4, and photoresist). The objective of this article is to evaluate the etch damage and contamination of the GaN surface when materials with other chemical nature are present during etching. The effects of etching conditions on surface morphology and chemical compositions of etched GaN films are studied in detail using XPS and AFM measurements. To this aim, a universal methodology is proposed to estimate accurately by XPS the stoichiometry of the GaN surface exposed to reactive plasmas when only an Al Kα x-ray source is available. The results indicate that the GaN etching mechanisms are very sensitive to the chlorine radical density present in the plasma, the latter being strongly influenced by the carrier wafer. Substrates that are more chemically reactive with Cl2 plasma such as silicon or photoresist compared to SiO2 or Si3N4 will lead to a greater loading of atomic chlorine, which in turn will lead to lower GaN etch rates. Moreover, the GaN surface contamination will depend on the etch by-products ejected by the carrier wafer. The GaN surface exposed to Cl2 plasma shows a Ga-depleted surface because of the more important reactivity of Cl with Ga rather than N, except in the SiO2 carrier wafer case. In this latter case, the formation of Ga–O bond limits the Ga removal. Regarding the surface roughness, it seems that the contaminants play a little role in the roughness formation except for the oxygen released by the SiO2 carrier wafer. On the other hand, the surface roughness evolution is clearly driven by the chlorine radical flux reaching the GaN surface. At low bias voltage, a preferential crystalline orientation etching driven by the Cl radicals leads to the formation of hexagonal shaped defects that are associated to screw-type threading dislocations already present in the pristine GaN material. At higher bias, the enlargement of the defects is limited, leading to a very low surface roughness value but to amorphized surfaces.

ZnO nanowires for photoelectric converter applications

This work is focused on the creation and study of photosensitive structures based on zinc oxide nanofibers, which are promising for solar energy. Zinc oxide nanowires were obtained on the porous zinc selenide surface. The porous substrate was obtained by electrochemical etching of a low-resistance n-ZnSe plate (110) with a polished surface. Nanowires were deposited by radical-beam epitaxy. The annealing temperature was varied from 400° C to 500° C. The oxygen radical flux was 1.5∙1017 cm-2s-1. The process duration was 50 minutes. According to the scanning electron microscopy results, the nanowires length reaches 10 μm, the nanowires diameter is ~1 μm. The predominant X-ray diffraction reflex at 2θ=34.44° indicates the polycrystalline nature of the manufactured ZnO coatings with a wurtzite-type hexagonal lattice. The study of nanowires ZnO luminescence at room temperature contains an ultraviolet peak around 385 nm. This peak is related to the zinc oxide edge luminescence. Based on the fabricated structure, the design of the photoconverter was developed. The upper contact of the fabricated photoelectric converter was created by vacuum thermal sputtering of aluminum through a mask. The deposition was carried out at a substrate temperature of 200° C. Ohmic contacts were made using conductive silver paste. The reverse ohmic contact was formed by applying Al paste to the entire reverse side of the surface. The upper layer of the structure is an array of ZnO nanowires. The active base layer is ZnSe. The light volt-ampere characteristics of the obtained structure were measured in the AM 1.5 illumination mode. No-load voltage Uxx, short-circuit current Isc and the fill factor of the current-voltage characteristic FF of the solar element were measured. The efficiency of the manufactured photoconverter was 13.7 %.

Surface functionalization of polypropylene nanoparticles in a pulsed low pressure air plasma discharge

One dimensional multi-fluid model is combined with a surface model to study the functionalization of polypropylene nanoparticles immersed in a repetitively pulsed low pressure air plasma. It is found that, the number densities of the charged and metastable species show periodic variations with time, whereas the concentrations of radicals increase in successive pulses. O2+ is the most important positive ion and O, OH, O3, and HO2 are the most important radicals in the functionalization of the polypropylene nanoparticle. The surface coverages of all functional groups are increased with increase in the pulse number, while the coverage of alkyl sites decreases after 200 pulses. At high pressures, the most important functional group with highest surface coverage is peroxy, followed by carbonyl, alcohol, alkoxy, and hydroperoxy. The electron number density and the incident fluxes of O2+ ions and O, OH, O3, and HO2 radicals, as well as the surface coverages of all functional groups are increased with increase in the gas pressure. Completely reverse effects were observed with increase in the gas temperature such that the incident ion and radical fluxes and all surface coverages decrease with increase in the gas temperature.