Remote Plasma Treatment Research Articles

Performance enhancement of Ge/Si avalanche photodetector by specific sidewall passivation using remote oxygen plasma treatment

We report an obvious improvement in the performance of a separated absorption charger-layer multiplication Ge/Si avalanche photodetector, achieved by passivating the sidewalls with a low-temperature remote oxygen plasma (ROP) treatment. The dangling bonds on the Ge surface can be efficiently passivated by the formation of an ideal Ge/GeO2 interface. With ROP passivation, the leakage current of the device shows a three- to fourfold decrease at 300 K, resulting in a dark current (I dark) of 3.5 × 10−6 A at 90% avalanche voltage (V br) and 3.4 × 10−7 A at punch-through voltage (V puhch-through) for the 26 μm-diameter device. A reduction of over tenfold is demonstrated at 200 K and the passivation mechanism is revealed. In addition, a multiplication gain of 94 is obtained under 1550 nm illumination. The device with ROP passivation shows an improved gain bandwidth product of 190 GHz. The enhanced high-frequency response of the device with ROP passivation can be attributed to the alleviation of the retarding effect caused by the interface state on the sidewalls. Without using a trans-impedance amplifier, an opening eye diagram at 28 Gbps is demonstrated, indicating reliable device transmission performance.

Analysis of the Impact of Remote Oxygen Plasma Treatment on the Surface Chemistry and Electrochemical Properties of Graphite Felt Electrodes for Redox Flow Batteries

The effects of a remote oxygen plasma (ROP) treatment on the surface of commercial graphite felts were investigated and compared against a conventional thermal treatment. In contrast to methodologies where...

High responsivity and stability of MSM structured MoS2 photodetectors by remote hydrogen plasma treatment and alternating growth of Al2O3/HfO2 passivation layers

Molybdenum disulfide (MoS2) is a representative material of transition metal dichalcogenides with a wide range of potential practical applications. However, the low responsivity and relatively short lifespan of MoS2 photodetectors...

Structural and Functional Changes in Soybean Protein via Remote Plasma Treatments.

To the best of our knowledge, few studies have utilized cold plasma to improve soybean protein extraction yield and the functional properties of soybean protein. In this study, we aimed to assess the benefits of remote plasma treatments on soybean with respect to the utilization of soybean protein. This study involved two different sample forms (whole and crushed beans), two different plasma chemistry modes (ozone and nitrogen oxides [NOx = NO + NO2]), and a novel pressure-swing reactor. Crushed soybeans were significantly affected by NOx-mode plasma treatment. Crushed soybeans treated with NOx-mode plasma had the best outcomes, wherein the protein extraction yield increased from 31.64% in the control to 37.90% after plasma treatment. The water binding capacity (205.50%) and oil absorption capacity (267.67%) of plasma-treated soybeans increased to 190.88% and 246.23 % of the control, respectively. The emulsifying activity and emulsion stability slightly increased compared to those of the control. The secondary structure and surface hydrophobicity were altered. The remote plasma treatment of crushed soybeans increased soybean protein extraction yield compared to plasma-treated whole beans as well as untreated beans and altered the structural and physicochemical properties of soybean proteins.

Damage-free remote SF6 plasma-treated CNTs for facile fabrication of electrochemical enzyme biosensors

Remote SF6 plasma treatment of CNTs is performed to graft hydrophobic fluorine on the surface of CNTs. Fluorinated CNTs (F-CNTs) allow for the facile adsorption of enzyme molecules via hydrophobic interaction between F-CNTs and the hydrophobic patches of enzyme molecules. The loading of glucose oxidase (GOx) on F-CNTs correlates well with plasma treatment time. Interestingly, the Rct value of GOx/F-CNTs decreases when CNTs are treated with plasma for a short time such as 1 and 5 min, which is due to weakly-bound chemisorbed fluorine molecules on F-CNTs (semi-ionic C-F). As an example, the Rct value of GOx/F-CNT electrode with 1 min plasma treatment is 0.57 times lower than that of GOx/CNTs, while increasing its sensitivity by 2.5 times. Upon extending the treatment time such as 30, 45 and 60 min, the XPS results reveal the dominance of covalently-attached fluorine, leading to marginally-increased resistance and sensitivity. It is worthy of noting this work is the first report of simple enzyme adsorption on remote-plasma treated CNT surfaces together with its detailed mechanism studies, especially for the binding of enzyme molecules semi-ionic fluorine.

Inversion-Mode In0.53Ga0.47 As MOSFET with f T = 275 GHz and high V eff

In this work, we present an inversion-mode In0.53Ga0.47As planar MOSFETs with current gain cutoff frequency (f T) = 275 GHz and maximum oscillation frequency (f max) = 75 GHz. To the best of our knowledge, this is the highest f T value among all the reported inversion-mode InGaAs MOSFETs. Meanwhile, peak transconductance (g m) shows 1035 (μS/μm). These extraordinary properties are attributed to the N2 remote plasma treatment which results in excellent high-k/III-V interface quality. With the assistance of delay-time analysis, effective electron velocity (V eff) of 2.88 × 107(cm s–1) is extracted for a possible explanation of the observed record f T performance.

SiO2 etching and surface evolution using combined exposure to CF4/O2 remote plasma and electron beam

Electron-based surface activation of surfaces functionalized by remote plasma appears like a flexible and novel approach to atomic scale etching and deposition. Relative to plasma-based dry etching that uses ion bombardment of a substrate to achieve controlled material removal, electron beam-induced etching (EBIE) is expected to reduce surface damage, including atom displacement, surface roughness, and undesired material removal. One of the issues with EBIE is the limited number of chemical precursors that can be used to functionalize material surfaces. In this work, we demonstrate a new configuration that was designed to leverage flexible surface functionalization using a remote plasma source, and, by combining with electron beam bombardment to remove the chemically reacted surface layer through plasma-assisted electron beam-induced etching, achieve highly controlled etching. This article describes the experimental configuration used for this demonstration that consists of a remote plasma source and an electron flood gun for enabling electron beam-induced etching of SiO2 with Ar/CF4/O2 precursors. We evaluated the parametric dependence of SiO2 etching rate on processing parameters of the flood gun, including electron energy and emission current, and of the remote plasma source, including radiofrequency source power and flow rate of CF4/O2, respectively. Additionally, two prototypical processing cases were demonstrated by temporally combining or separating remote plasma treatment and electron beam irradiation. The results validate the performance of this approach for etching applications, including photomask repair and atomic layer etching of SiO2. Surface characterization results that provide mechanistic insights into these processes are also presented and discussed.

Electrical characteristics investigation of ferroelectric memories using stacked and mixed hafnium zirconium oxides

• Ferroelectric characteristics of mixed and stacked HfZrO devices were investigated. • Stacked HfZrO device showed a much stronger ferroelectricity than mixed one. • A surface nitrogen plasma treatment can alleviate ferroelectric domain pinning. • Nitrogen incorporation into stacked HfZrO further improved the endurance cycling. In this work, we investigate ferroelectric characteristics of hafnium zirconium oxide (HfZrO) metal-ferroelectric-metal (MFM) devices with mixed and stacked film structure. The experimental results reveal that the stacked HfZrO MFM device has a lower dynamic leakage and stronger ferroelectric polarization value of approximately 27.3 μC/cm 2 , which is much higher than 17.5 μC/cm 2 measured from mixed HfZrO MFM device. From endurance cycling test, we also confirm that the stacked HfZrO MFM capacitor with a remote nitrogen plasma treatment featuring a large initial hysteresis window can achieve a stable operation up to 10 8 cycles at an operating voltage of 2.5 V, which is even longer than that of mixed HfZrO MFM capacitor by one order of magnitude. Therefore, the stacked MFM structure with proper interface engineering provides a promising approach for the process integration of ferroelectric memory under the comprehensive consideration of device performance and endurance.

Performance investigation of hafnium-oxide negative capacitance transistor with remote nitrogen plasma treatment

In this study, we demonstrated the hafnium-oxide negative capacitance transistors using different nitrogen plasma treatments. According to our experimental results, the electrical performance and negative capacitance switch characteristics were also affected by process temperature and ferroelectric/non-ferroelectric crystalline phases in addition to nitrogen species. The transistor device using optimal nitrogen plasma treatment exhibited the excellent performances, including a low off-state current (IOFF) of ∼10−13 A/μm, a large on/off-state current ratio (ION/IOFF) of 107 and a steep subthreshold swing (SS) of sub-60 mV/decade with tight switching uniformity under a gate overdrive voltage of 2 V. These experimental results confirm that the negative capacitance transistor adopting hafnium oxide can be further improved by nitrogen species incorporation, which give a promising guidance for the next-generation low-power electronics.

Oxygen diffusion barrier on interfacial layer formed with remote NH3 plasma treatment

An oxidation or nitridation treatment was performed on the interfacial layer (IL) with optimal oxidation state in order to form an oxygen diffusion barrier for Ge nMOSFET . Through the analysis of X-ray photoelectron spectroscopy and electrical characterization of Ge nMOSFET, the reaction mechanism and physical model were studied in details. The fewer interface traps and lower subthreshold swing can be achieved by forming oxygen diffusion barrier in an optimal IL with remote NH 3 plasma. As compared to devices with oxidation treatments , that improvement can be attributed to the nitrogen passivation and alloy-like interface formation. The proposed oxygen diffusion barrier with remote NH 3 plasma treatment on IL is a promising technique to improve the interface properties effectively without influencing equivalent oxide thickness for high performance Ge nMOSFET. • An interfacial layer buffer formation method is proposed. • An oxygen diffusion barrier can be formed by remote plasma treatment. • A n-channel Ge transistor can be enhanced by NH 3 plasma. • Reaction mechanism about oxygen diffusion is explained by material analysis.

Non-contact and non-invasive monitoring of plant growth combining atmospheric pressure remote plasma treatment and detection of plant-derived biophotons

The present study demonstrated non-contact and non-invasive monitoring of plant growth by combining atmospheric pressure remote plasma treatment with measurement of the ultra-weak luminescence of biophotons emitted from plants. Biophotons were more likely to be emitted from plasma-irradiated seeds than from unirradiated seeds. Furthermore, these results could characterize the germination state of seeds in a non-contact and non-invasive manner and will help elucidate the potential mechanisms underlying the growth-promoting effects of plasma irradiation as well as the development of “plasma agriculture”.

Impact of O2 plasma treatment on novel amorphous oxide InWZnO on conductive bridge random access memory

The impact of O2 plasma treatment on novel amorphous oxide InWZnO (IWZO) as conductive bridge random access memory (CBRAM) was investigated. A high-quality film on the surface of IWZO can be obtained by using remote O2 plasma treatment. The uniformity of O2 plasma sample is better than control sample, and also the set and reset voltage are more uniform and smaller to suitable for memory operation. Moreover, the O2 plasma sample shows excellent memory performance, such as high switching endurance cycles (up to 3 × 103), long retention time for 104 s at 85 °C. These results show that the surface modification with O2 plasma on IWZO CBRAM device is a critical technique for next generation memory applications.

Tuning the wicking and wettability properties of PET textiles by DBD or a remote atmospheric RF torch: A comparison

AbstractTextile industry is constantly searching for easy and rapid ways to improve the properties of textiles. In this matter, plasma treatments have already proven to be an efficient and green solution, as they proceed in a dry environment and require minimal use of chemicals. To date, most of the work on the subject has been performed with low‐pressure plasmas. Recently, atmospheric plasmas have received increasing interest, especially for industrial applications. Indeed, the possibility to avoid the use of pumping systems makes this technology easily implementable in continuous in‐line processes. For many applications, the treatment aims at modifying the textile surface to increase the overall hydrophilicity. The latter is often probed by the water contact angle, but this does not always reflect the global hydrophilic behavior of the textile as a three‐dimensional material. A complementary study of the wicking properties is important to better reflect the penetration of liquids into the textile, but it is poorly reported in the literature. The present work aims at increasing the water uptake of polyethylene terephthalate (PET) textile by direct or remote plasma treatment, which are the two main trends in this field. For this purpose, a dielectric barrier discharge (DBD) and a radiofrequency plasma torch at atmospheric pressure are used, respectively. Different plasma parameters are varied and their respective effect on the wicking properties of the fabric, assessed by an absorbency test developed ad hoc, are correlated to their surface chemical composition determined by X‐ray photoelectron spectroscopy. These results are compared with the possible changes in wetting of the fiber surface witnessed by water contact angles measured on PET foil samples submitted to the same plasma treatments. Complete wicking of water in PET textile can be obtained after 20 or 10 s of torch treatment with pure Ar plasma or Ar/O2 mixture, respectively. However, a comparable effect is detected, after 30 s of DBD Ar plasma treatment, under the used experimental conditions. Besides, the addition of O2 to the discharge has an opposite effect on the fabric wicking. These results are discussed in terms of the peculiar processes in surface activation and modification of the fabric surface triggered by the two different plasma technologies.

Investigation of device transport characteristics enhancement of In0.53Ga0.47As MOSFET through in situ NH3/N2 remote-plasma treatment

In this work, we demonstrated considerable enhancement of the transport characteristics of n-type Al2O3/In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors (n-MOSFETs) with the assistance of in situ NH3/N2 remote-plasma (RP) treatment. According to the measurement and simulation results, the RP treated sample shows superior device performances as compared to the control sample without plasma treatment including (a) improved on-current (Ion) from 8.5 mA/mm to 17 mA/mm, (b) improved transconductance (Gm) from 16.05 mS/mm to 28.52 mS/mm, (c) suppressed subthreshold swing from 189 mV/dec to 170 mV/dec, (d) suppressed drain induced barrier lowering from 36 mV/V to 28 mV/V, (e) intensified peak effective mobility (μeff) from 1896 cm2 V−1 s−1 to 2956 cm2 V−1 s−1, and (f) reduced acceptor-type density of interface trap state (Dit,A) to 44%. By using TCAD simulation, device output performance is found to be dramatically impacted by the trap state (especially acceptor-type) at the Al2O3/InGaAs interface.

Anti-oxidant copper layer by remote mode N2 plasma for low temperature copper\u2013copper bonding

An anti-oxidant Cu layer was achieved by remote mode N2 plasma. Remote mode plasma treatment offers the advantages of having no defect formation, such as pinholes, by energetic ions. In this study, an activated Cu surface by Ar plasma chemically reacted with N free radicals to evenly form Cu nitride passivation over the entire Cu surface. According to chemical state analysis using XPS, Cu oxidation was effectively prevented in air, and the thickness of the Cu nitride passivation was within 3 nm. Based on statistical analysis using the DOE technique with N2 plasma variables, namely, RF power, working pressure, and plasma treatment time, we experimentally demonstrated that a lower RF power is the most effective for forming uniform Cu nitride passivation because of a lower plasma density. When the N2 plasma density reached approximately 109 cm−3 in which the remote mode was generated, high energy electrons in the plasma were significantly reduced and the amount of oxygen detected on the Cu surface was minimized. Finally, low temperature (300 °C) Cu–Cu bonding was performed with a pair of the anti-oxidant Cu layers formed by the remote mode N2 plasma. Cu atomic diffusion with new grains was observed across the bonded interface indicating significantly improved bonding quality over bare Cu–Cu bonding.

Inactivation of virus and bacteria using cold atmospheric pressure air plasmas and the role of reactive nitrogen species

Cold atmospheric pressure plasma has potential as a non-thermal processing technology to decontaminate food and food contact surfaces due to its ability to generate an abundance of reactive oxygen and nitrogen species with antimicrobial attributes at ambient conditions. In this study, we present a comparison on the effectiveness of surface decontamination against feline calicivirus (FCV) and Salmonella spp using four different plasma sources, a dielectric barrier discharge (DBD) in direct contact with the substrate and three remote plasma treatment sources: a 2D DBD, a volumetric DBD and a gliding arc discharge. The plasma sources were all operated in air at atmospheric pressure. The decontamination efficacy was enhanced by the presence of humidity on the sample surface and only direct contact between plasma and samples allowed the inactivation of pathogens on dry substrates. Across all sources, FCV was seen to be more susceptible to the plasma-generated species than Salmonella spp. The diminished effectiveness of the gliding arc discharge compared to the DBDs operating at the same power is most likely due to the low Henry’s law constant of NO, the dominant reactive species generated by the gliding arc. Control experiments illustrate that the co-existence of O3 and NO2, as in the afterglow of the remote DBDs enhances the inactivation compared to the inactivation by O3 or NO2 only. A chemical kinetics model of the plasma effluent and the plasma treatments show a strong correlation between the gas-phase concentration of N2O5 and inactivation of the virus. We experimentally show that the production of N2O5 coincides with the enhanced generation of reactive nitrogen species in the liquid phase.

Toward Bioluminescent Materials by Plasma Treatment of Microfibrous Nonwovens, Followed by Immobilization of One or Both Enzyme(s) (Luciferase and FMN Reductase) Involved in Luminescent Bacteria.

Bioluminescent living organisms emit light through a specific biocatalyzed reaction involving a luciferin substrate and a luciferase enzyme. The present work investigated the possibility of creating optimal luminescence by immobilization of one or both the enzymes Luciferase (Luc) and FMN reductase (Red) involved in a bioluminescent bacterial system onto a plasma-activated microfibrous PET nonwoven. Parameters affecting the catalytic activity and efficiency of the bacterial system in aqueous medium were determined by luminescence intensity measurements using a luminometer. Two types of plasma, air atmospheric plasma (ATMP) and cold remote plasma (CRPNO) treatment, were used to activate the PET nonwoven. Further, one or both enzyme(s) were immobilized using a physical adsorption technique, without or with the use of natural biopolymers (gelatin and starch) and bovine serum albumin-BSA protein, to improve enzyme stability and activity. Coimmobilization of both Red and Luc enzymes on the CRPNO plasma-activated nonwoven in the presence of BSA led to the maximum luminescence. As high as 60,000 RLU equivalent to that of an LED light used for calibration was observed and showed stable intensity up to 6 min. Fiber surface analysis was tested using wettability tests (water contact angle and capillary uptake), while scanning electron microscopy, atomic force microscopy, and electron spectroscopy for chemical analysis showed changes in fiber surface morphology and chemical functional groups. A considerable increase in "N" atom content after coimmobilization of enzymes in the presence of BSA was detected. This study is the first successful attempt to use a biomimetic strategy for immobilization of enzymes involved in bacterial luminescence on a plasma-activated microfibrous nonwoven in an attempt to attain bioluminescent materials.

Effects of Low-Damage Plasma Treatment on the Channel 2DEG and Device Characteristics of AlGaN/GaN HEMTs**Supported by the National Natural Science Foundation of China under Grant Nos. 61634005, 61704124, and 11690042.

We investigate the effects of remote nitride-based plasma treatment on the channel carrier and device characteristics of AlGaN/GaN high electron mobility transistors (HEMTs). A 200 W NH3/N2 remote plasma causes little degeneration of carrier mobility and an increase in electron density due to surface alteration, which results in a decrease in sheet resistance and an increase in output current by 20–30%. Improved current slump, suppressed gate leakage current, and improved Schottky contact properties are also achieved by using low-damage nitride-based plasma treatment. It is found that NH3/N2 remote plasma treatment is a promising technique for GaN-based HEMTs to modulate the surface conditions and channel properties.

Comparative evaluation of the virucidal effect of remote and direct cold air plasmas with UV‐C

AbstractCold atmospheric pressure plasma is an emerging nonthermal processing technology for the decontamination of foodborne pathogens. This study presents a comparative evaluation of the energy efficiency of the decontamination by three different dielectric barrier discharge (DBD) setups operating in air against Feline calicivirus with a UV‐C lamp. Significant enhancement of the energy efficiency was achieved with a lab‐scale batch reactor prototype, which employed surface DBD, leading to similar energy per unit area requirements as that for UV‐C. A key advantage of plasma over UV‐based disinfection systems is that plasmas are not limited by shadowing effects. Nonetheless, unlike UV‐C, the virucidal efficacy of plasma is significantly reduced for dry samples and remote plasma treatment is only effective against wet samples.

Influence of remote plasma on PEDOT:PSS‐coated carbon felt for improved activity of glucose oxidase

ABSTRACTIncreasing wettability of carbon felts is an important strategy to improve their efficiency in bio‐electrochemical applications. Herein, influence of cold remote plasma (N2 + O2) treatment on surface properties of carbon felts with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coating was tested, aiming to improve immobilizing of glucose oxidase enzyme (GOx). Spectra of N 1s and O 1s confirmed the integration of carbonyl and ether as well as amide and amine groups on bare carbon fiber surface, while on coated fibers, carbonyl groups were pre‐dominant. S 2p spectra confirmed oxidation of PEDOT:PSS coating with reduction of (S−) compared to (SO3−) group. GOx immobilized on different samples showed highest activity for PEDOT:PSS coating subjected to plasma with 2% O2, maintaining up to 60% after immobilization, and 37% of its activity after six cycles for some samples. Enzymes immobilized on samples without plasma treatment lost their activity after four cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48521.