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The present study reports on the systematic analysis of the friction and the wear behaviors of carbon nitride (CNx) thin films deposited by direct current unbalanced magnetron sputtering. We focus on the normal load dependence on the friction coefficient and wear rate for the sliding friction of the SUJ2 ball with the CNx thin film. The friction coefficient was monitored using a ball-on-disc apparatus with various loads in ambient air. The friction coefficient (μ) increases linearly from ∼0.05 to 0.28 with increasing normal load, while the specific wear rate decreases with an increase in load. The wear rates of the SUJ2 ball ∼1.5 × 10−7 mm3/Nm for μ = 0.05 and ∼5.5 × 10−8 mm3/Nm for μ = 0.28 were observed in the deposited CNx films with the minimum and maximum normal load. The friction and wear mechanisms are discussed in relation to the surface morphology and microstructure of the CNx coatings.

A large area magnetron source with the strongly confined magnetic field from all direction is applied for the deposition of flexible ultrathin ITO (UT-ITO) films of thickness 30 nm at room temperature for their applications as transparent electrodes. The films show a minimum resistivity of ∼5.0 x 10-4 Ωcm and high transmittance >80% at wavelengths of 400-700 nm. Measurements and data reveal that a high plasma density, high energy flux, and a relatively low concentration of negative oxygen ions (NOIs) to the flux of positive ions (PIs) induce lower mechanical stress to the growing films, which enables a lower resistivity and superior crystallinity with the smooth surface. The capability of the magnetron source and the characteristic plasma properties are studied in light of the resulting film properties. The considerably lower resistivity with higher carrier concentration and mobility of the UT-ITO films prepared at a high power density of 3 W/cm2 and a low O2 gas flow can be attributed to the growth of crystallized UT-ITO films, resulting in the combination of the oxygen vacancy and substitution of Sn4+ to In3+ site through the deposition of a high energy flux and a low flux ratio of NOIs to PIs.

The temporal behavior of the electron energy distribution function and plasma parameters in the vicinity of the substrate have been investigated in detail by performing time-resolved probe measurements in a pulsed and unbalanced magnetron argon discharge. A 20-kHz midfrequency unipolar dc pulse with an on-time average power of 160 W and a duty cycle of 50% was applied to the metallic cathode target. It was found that the high-energy electrons with energies higher than the sheath potential energy are generated within a few microseconds after the dc pulse is turned on and the electron energy distribution functions during the pulse-on period show a bi-Maxwellian distribution with the high-energy electron group. In the afterglow after the dc pulse is turned off, the initial fast decay of the high-energy electrons and the subsequent diffusive slower decay of the low-energy electrons were observed. This temporal behavior of the electron energy distribution function reflected two-fold decay characteristics of electron density and electron temperature when approximated by a biexponential function with two characteristic decay times and an initial fast decay time of less than a few microseconds and a subsequent slower decay time of few tens of microseconds were observed. The temporal behavior of the other plasma parameters were presented and these results were explained in view of electron heating by deeply penetrating the high-voltage cathode sheath and electron transport. [ABSTRACT FROM AUTHOR]

In this study, an inductively coupled plasma (ICP)-enhanced reactive sputter deposition system with a rectangular target was developed as a linear plasma source for roll-to-roll deposition processes. The longitudinal distribution of the film thickness indicated the feasibility of uniformity control via the control of the power deposition profile of the assisted ICPs. The characteristics of Si films were investigated in terms of the film thickness uniformity and film crystallinity. The results of Raman and X-ray diffraction measurements indicated the crystallization of the Si film with a crystallinity as high as 73%-78% in all the samples of the longitudinal position. [ABSTRACT FROM AUTHOR]

Simultaneously achieving higher carriers concentration and mobility is a technical challenge against up-scaling the transparent-conductive performances of transparent-conductive oxides. Utilizing one order higher dense (~1 × 1011 cm-3) plasmas (in comparison to the conventional direct current plasmas), highly c-axis oriented Al-doped ZnO films have been prepared with precise control over relative composition and chemical states of constituting elements. Tailoring of intrinsic (O vacancies) and extrinsic (ionic Al and zero-valent Al) dopants provide simultaneous enhancement in mobility and concentration of charge carriers. Room-temperature resistivity as low as 4.89 × 10-4 Ω cm along the carrier concentration 5.6 × 1020 cm-3 is obtained in 200 nm thick transparent films. Here, the control of atomic Al reduces the charge trapping at grain boundaries and subdues the effects of grain boundary scattering. A mechanism based on the correlation between electron-hole interaction and carrier mobility is proposed for degenerately doped wide band-gap semiconductors. [ABSTRACT FROM AUTHOR]

In the downstream region of an unbalanced magnetron argon discharge, the influences of substrate bias (i.e., the condition of plasma boundary) on electron energy distribution function and plasma characteristics were investigated through the experiments using a single Langmuir probe. In a steady state with the grounded substrate, it could be found that the electron current flowing to the substrate compensates for the ion current flowing to the cathode due to the axial magnetic field such that the substrate plays the role of the actual anode. The potential of the anode sheath could be controlled by applying a dc voltage to the substrate, and the nonlinear behavior of the plasma potential with respect to the dc substrate voltage caused the distinctive evolution of the potential of the anode sheath. It was found that a transition of the electron energy distribution function from a bi-Maxwellian distribution at small dc voltages to a Maxwellian distribution at highly negative dc voltages occurs with decreasing the substrate bias voltage. This phenomenon was discussed in view of the role of the substrate as an electron loss boundary and the cooling mechanism of electrons in bulk plasmas. [ABSTRACT FROM AUTHOR]

The time-resolved probe measurements of the plasma parameters and the electron energy distribution function are carried out in a unipolar pulsed dc magnetron argon discharge. The cathode target is driven by the 20 kHz midfrequency unipolar dc pulses at three operating modes, such as constant voltage, constant power, and constant current with the duty cycles ranging from 10% to 90%. It is observed that as the duty cycle is reduced, the electron temperature averaged during the pulse-on period rapidly increases irrespective of the operating mode although the average electron density strongly depends on the operating mode. The comparison of the measured electron energy distribution functions shows that the electron heating during the pulse-on period becomes efficient in the pulse operation with short duty cycle, which is closely related to the deep penetration of the high-voltage sheath into the bulk during the pulse-on period. [ABSTRACT FROM AUTHOR]

Control of the bonding structure in carbon materials is achieved by a post-treatment of atmospheric pressure plasma (APP) for magnetron-sputtered carbon films. The APP post-treatment changes the films morphologically owing to the removal and modification of sp2 bonds on the basis of the near edge X-ray absorption fine structure analysis of sp2 contents. By APP post-treatment, the resulting changes in surface and bulk properties modify the optical and electrical properties of the carbon films. The control of the film properties can be utilized for various applications, such as gas sensors and solar cells. [ABSTRACT FROM AUTHOR]

Low-bandgap transparent conductive oxides will be of interest to researchers who wish to address the health hazards of blue radiation emission from electronic displays. Here, we present a single-step, low-temperature fast enough (throughput  >  60 nm min−1) process to grow highly c-axis-oriented crystalline Al-doped ZnO thin films via advanced plasma processing. Dual-power DC-magnetron sputtering plasma was employed for the synthesis of thin films. The addition of top power to a pre-existing rectangular power pushed additional ions to a confined plasma and increased the plasma density and electron temperature. The effect of this additional-ion pushing was systematically studied using the microstructure, surface properties, and electronic properties. As a result, bandgap reduction from 3.35 eV to 3.10 eV and tailoring of electrical resistivity (4.89  ×  10−4–8.32  ×  10−3 Ω cm) and Seebeck coefficients (21–48 µV K−1) were achieved in addition to excellent transparency. Given their properties, the obtained films show promise for multifunctional applications, such as in UV and near-blue radiation shielding, transparent conductive electrodes and low-temperature thermoelectrics. [ABSTRACT FROM AUTHOR]

We show results of the patterning of graphene layers on poly(ethylene terephthalate) (PET) films through remote atmospheric-pressure dielectric barrier discharge plasma. The size of plasma discharge electrodes was adjusted for large-area and role-to-role-type substrates. Optical emission spectroscopy (OES) was used to analyze the characteristics of charge species in atmospheric-pressure plasma. The OES emission intensity of the O2* peaks (248.8 and 259.3 nm) shows the highest value at the ratio of due to the highest plasma discharge. The PET surface roughness and hydrophilic behavior were controlled with CDA flow rate during the process. Although the atmospheric-pressure plasma treatment of the PET film led to an increase in the FT-IR intensity of C–O bonding at 1240 cm−1, the peak intensity at 1710 cm−1 (C=O bonding) decreased. The patterning of graphene layers was confirmed by scanning electron microscopy and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Carbon thin films, having a combination of unique physical and chemical properties, exhibit an interesting biocompatibility and biological response to living entities. Here, the carbon films are developed in the morphology form of nano-domains with nanoscale inter-domain separations, tuned by plasma conditions in the facing target magnetron sputtering process. The wettability and surface energy are found to have a close relation to the inter-domain separations. The chemical structure of carbon films exhibited the relative enhancement of sp3 in comparison to sp2 with the increase of domain separations. The cell-viability of these films shows promising results for L929 mouse fibroblast and Saos-2 bone cells, when inter-domain separation is increased. Electrical conductivity and surface energy are identified to play the key role in different time-scales during the cell-proliferation process. The contribution from electrical conductivity is dominant in the beginning of the cultivation, whereas with the passage of time (~3–5 d) the surface energy takes control over conductivity to enhance the cell proliferation. [ABSTRACT FROM AUTHOR]

Nonthermal atmospheric-pressure plasma discharge is designed with low-temperature cofired ceramic (LTCC) electrodes to achieve dielectric barrier surface discharge (DBSD). The environmental requirement (below 0.05 ppm) of the amount of byproducts (ozone and NOx) produced during the process was met by optimizing the electrode design to produce a high dielectric barrier discharge for low-voltage (∼700 V) operation and minimizing the distance between electrodes to improve the plasma discharging efficiency. The concentrations of volatile organic compounds (VOCs) within interior cabins of commercial vehicles were significantly reduced after 1-h treatment to improve air quality cost-effectively. This atmospheric-pressure plasma process was demonstrated for the sterilization of Escherichia coli to prevent food poisoning during the preservation of food in refrigerators. [ABSTRACT FROM AUTHOR]

Utilizing plasma-assisted deposition by combining an RF magnetron and an inductively coupled plasma (ICP) source it is possible to fabricate highly crystallized nc-Si:H films at a relatively low substrate temperature (300 °C). Microstructural analysis reveals enhancement in crystallinity along with (2 2 0) preferential orientation throughout the depth of the film. The possible mechanism of crystallinity enhancement and preferential orientation is presented on the basis of plasma diagnostics using optical emission spectroscopy and various film analysis tools. This work also reports the effectiveness of the ICP source and elevated temperature for the control of film microstructure and crystallinity. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis of flexible indium tin oxide (ITO) films in a dual pulse magnetron sputtering (DPMS) system at low temperature (<100 °C) deposition condition. This study also presents experimental demonstration of the ITO films for their possible use in the fabrication of organic light emitting diode (OLED) device, and the device performance on the super polycarbonate substrates. The presented data reveals the feasibility of ITO films, with a very low sheet resistance of ∼30 Ω/□ and high transmittance of ∼88% at 550 nm, simply by the magnetron pulse mode operations with increasing pulse frequency from 0 to 50 kHz. [ABSTRACT FROM AUTHOR]

Looking into the aspect of material processing, this work evaluates alternative plasma concepts in SiH4/H2 plasmas to investigate the radical and plasma generation in the plasma enhanced chemical vapor deposition (PECVD) synthesis of nanocrystalline Si (nc-Si:H). Simultaneous measurements by vacuum ultraviolet absorption spectroscopy (VUVAS), optical emission spectroscopy (OES), and radio frequency (RF) compensated Langmuir probe (LP) reveal that RF/ultrahigh frequency (UHF) hybrid source can efficiently produce H radicals and plasmas that are accountable for nc-Si:H film synthesis. The efficacy of hybrid plasmas is also discussed. [ABSTRACT FROM AUTHOR]

Careful analysis and investigations of the formation mechanism of the microstructure of the hydrogenated nanocrystalline silicon (nc-Si:H) film is presented. A systematic approach is made to understand the transition from amorphous (a-Si:H) to crystalline (nc-Si:H) by incorporating hydrogen dilution using inductively coupled plasma (ICP) assisted magnetron sputtering. Film analysis and plasma diagnostics results reveal that one can design desired microstructure simply by controlling H2 dilution and energy control in the plasmas. [ABSTRACT FROM AUTHOR]

Porous conductive carbon films are useful for application in fuel cells and biomedical sensors. Controllability of the porosity in conductive carbon films was investigated by using unbalanced magnetron sputtering (UBMS). Here, we show through porosity analysis and plasma diagnostics that carbon films can be tuned to have porosity ranging from amorphous to porous by varying the working pressures from 3 to 140 mTorr in UBMS. The porosity control is attributed to the carbon adatom energy change by control of the working pressures. This approach enabled us to obtain porous carbon films of 44–68% with a high conductivity of 20–0.001 S/cm, implying the feasibility of porous conductive carbon films for advanced applications. [ABSTRACT FROM AUTHOR]

The recent bio-applications (i.e. bio-sensing, tissue engineering and cell proliferation etc.) are driving the fundamental research in carbon based materials with functional perspectives. High stability in carbon based coatings usually demands the high density deposition. However, the standard techniques, used for the large area and high throughput deposition of crystalline carbon films, often require very high temperature processing (typically >800 °C in inert atmosphere). Here, we present a low temperature (<150 °C) pulsed-DC plasma sputtering process, which enables sufficient ion flux to deposit dense unhydrogenated carbon thin films without any need of substrate-bias or post-deposition thermal treatments. It is found that the control over plasma power density and pulsed frequency governs the density and kinetic energy of carbon ions participating during the film growth. Subsequently, it controls the contents of sp³ and sp² hybridizations via conversion of sp² to sp³ hybridization by ion's energy relaxation. The role of plasma parameters on the chemical and surface properties are presented and correlated to the bio-activity. Bioactivity tests, carried out in mouse fibroblast L-929 and Sarcoma osteogenic (Saos-2) bone cell lines, demonstrate promising cell-proliferation in these films. [ABSTRACT FROM AUTHOR]