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Measurements of ion flux-energy distribution functions at the high sheath potential of the driven electrode in a classical low-pressure asymmetric capacitively coupled plasma are technically difficult as the diagnostic device needs to float with the applied radio frequency voltage. Otherwise, the ion sampling is disturbed by the varying electric field between the grounded device and the driven electrode. To circumvent such distortions, a low-pressure plasma chamber with inverted electrode geometry, where the larger electrode is driven and the smaller electrode is grounded, has been constructed and characterized. Measurements of the ion flux-energy distribution functions with an energy-selective mass spectrometer at the high sheath potential of the grounded electrode are presented for a variety of conditions and ions. The potential for suppressing low-energy ions from resonant charge transfer collisions in the sheath by the dilution of the working gas is demonstrated. Additionally, the setup is supplemented by an inductively coupled plasma that controls the plasma density and consequently the ion flux to the substrate while the radio frequency bias controls the ion energy. At high ion energies, metal ions are detected as a consequence of the ionization of sputtered electrode material. The proposed setup opens a way to study precisely the effects of ion treatment for a variety of substrates such as catalysts, polymers, or thin films.

One challenge for microcrystalline silicon (μc-Si:H) deposition is to achieve high deposition rates while maintaining high quality films. In this work, an inductively-coupled plasma (ICP) is used to deposit μc-Si:H on glass substrates by means of a novel planar resonant antenna at 13.56 MHz. No particle formation occurs in the low pressure (5 Pa) plasma, but the films suffer post-oxidation. By embedding a 5 MHz RF-biased substrate, films deposited simultaneously with and without RF bias are compared. It is shown that large area, low pressure (5 Pa), particle-free ICP deposition at 1 nm/s of μc-Si:H films can be obtained without post-oxidation by means of a planar resonant antenna, provided that RF substrate bias is included for independent control of the ion energy. [ABSTRACT FROM AUTHOR]

In this work, we present the deposition of Ni x Ti 1 − x shape memory alloy (SMA) thin films at a substrate temperature of 350 °C. Deposition at 350 °C preserves the mechanical properties of the polymer and widens the scope for potential applications such as electrically excitable soft bodied robots, in flexible deformable devices and for miniaturized biomedical active probes. Essential for this result is the application of an ion-bombardment to the growing film. For the ion bombardment on the growing film, RF bias plasma was generated at the sample stage. The films were deposited through magnetron sputtering from NiTi and Ti targets onto polyimide spin coated silicon wafers. The crystal structure, surface morphology and microstructure were studied using X-ray diffraction, atomic force microscopy and transmission electron microscopy. As deposited films on spin coated polyimide were crystalline. The presence of solid state transformation responsible for shape memory effect has been demonstrated through electrical resistance vs temperature measurements and temperature dependent X-ray diffraction for approximately stoichiometric films. Transmission electron microscopy observations revealed that all films have an amorphous base and a columnar poly-crystalline top and the formation of nuclei is dependent on chemical composition and thickness. [ABSTRACT FROM AUTHOR]

Abstract: Samples are usually placed on an RF bias electrode for an inductively coupled plasma device. The RF current and voltage waveforms at the bias electrode were measured. The current through the stray capacitance was cancelled by an LC cancel circuit. Only the sheath impedance at the bias electrode was considered as the equivalent circuit. The RF voltage greatly depended on the RF power, but the RF current slightly depended on the RF power. The conduction current could be related to the plasma density. The incident ion current to the bias electrode was given by the half value of the amplitude of the conduction current. The obtained incident ion current agreed with those obtained from different methods. [Copyright &y& Elsevier]

Abstract: A novel designed microwave PECVD system with large-area microwave plasma source is employed for the feasibility study to grow thin silicon films at low temperature. With the total area being 25 cm×30 cm, three sets of array antenna composed by many copper rods with adjustable length are employed to couple the microwave power into the deposition chamber. A RF power source is employed to induce a negative bias on the substrates. High purity (99.99%) SiH4, H2, and Ar are introduced as reaction gases, and ultrasonically cleaned glasses are used as substrates. Silicon films with grain sizes about 80∼100 nm are successfully deposited at temperatures below 82 °C. Further studies will focus on the modification of the system design so as to reach the goals to deposit silicon films with improved crystallinity, larger grain sizes, and more uniformity over the large area. [Copyright &y& Elsevier]

Abstract: TiO2 films with thicknesses of 400–460 nm were deposited on the unheated non-alkali glass by radio frequency (rf) reactive magnetron sputtering using a Ti metal target. Depositions were carried out using a 3-in. 1000 G magnetron cathode with various rf substrate bias voltages (V sb, dc component of self bias) of 10–80 V under total gas pressure of 1.0 or 3.0 Pa. The oxygen flow ratio [O2/(O2 +Ar)] and rf sputtering power were kept constant at 60% and 200 W, respectively. Photocatalytic activity on photoinduced oxidative decomposition of acetaldehyde (CH3CHO) of the TiO2 films showed a clear tendency to decrease with the increase in the V sb during the deposition. Most of the films consisted of the mixture of anatase and rutile polycrystalline portions. It was confirmed that the rutile phase content increased and anatase phase content decreased markedly with increasing V sb, where the crystallinity of anatase phase was much higher than that of rutile phase. [Copyright &y& Elsevier]

The structure of TiO2 prepared by arc ion plating was changed by RF substrate bias from anatase (0 V) through amorphous (−50 V) to rutile (or rutile+anatase) (>−100 V). This tendency was almost independent of arc current (50–80 A). As insulating TiO2 deposited on the chamber wall, irregular discharge occurred in the chamber. This irregular discharge was enhanced by the substrate bias so that the growth rate was decreased from 1 to 0.6 nm/s and the substrate temperature was decreased from 350°C to 150°C.The oxygen content was increased with decreasing arc current, but the crystallinity at a low arc current of 50 A was low. The decomposition efficiency of NO2 gas by TiO2 photocatalyst prepared at arc current of 60 A was high, which was due to the low oxygen deficiency. In particular, anatase structure showed the highest efficiency. Therefore, it is said that structure, composition and crystallinity of the TiO2 films affect the photocatalytic efficiency. [Copyright &y& Elsevier]

A novel direct current (DC) magnetron sputtering system via radio frequency (RF) bias with hexamethyldisiloxane (HMDSO) plasma polymerization was developed for the deposition of SiOx-doped diamond-like carbon (DLC) films on a glass substrate. As the RF bias increased, the ratio of intensity of D peak and G peak (I(D)/I(G)) decreased and the G peak shifted to a low position, leading to high hardness and a large portion of sp3 bonds. Additionally, weak sp2 graphite bonds were broken and sp3 diamond bonds formed because the RF bias attracted hydrogen ion bombarding the DLC films. Increasing DC power was helpful to improve the hardness of the DLC films because the proportion of sp3 bonds and the I(D)/I(G) ration was increased. HMDSO was introduced into this process to form SiOx:DLC films with enhanced optical performance. The average transmittance in the visible region of these very thin SiOx:DLC films with a thickness of 37.5 nm was 80.3% and the hardness of the SiOx:DLC films was increased to 7.4 GPa, which was 23.3% higher than that of B270 substrates. [ABSTRACT FROM AUTHOR]

Abstract: In order to investigate the mechanism of etching in low pressure radio-frequency (rf) plasmas, we adopt a two-dimensional Monte-Carlo (MC) cellular method to simulate the profile evolution, in which the ion reflection, the ion angular distribution (IAD) etc. are considered. It is found that the phenomenon of microtrenching results from the reflection of particles on the sidewall and the IAD is responsible for round corners at the bottom of the trench. The deeper the trench is, the more easily microtrenching or notching appear. In addition, the neutral particles can destroy the anisotropic etching of the trench and lead to bowling. On the other hand, by means of solving the Laplace equation near and in the trench with an iterative procedure, we obtain a stable or periodic stable electric field biased by a dc or rf source, in which the charging effect on the photoresist sidewall of the trench is considered. It is observed that both the dc and rf biases applied to the substrate can influence the profiles of etching, and the better etching profiles on the sidewall of the trench can be obtained with the rf bias than those with the dc bias. [Copyright &y& Elsevier]

Abstract: Silicon oxide thin films are transparent protective coatings with anti-scratch, chemical resistant, barrier properties that have recently emerged as one of the prime coating technologies for depositing a range of functional optical coatings on polymer substrates in mobile electronics, digital cameras and other digital applications. Many optically transparent and protective coating materials as well as low temperature plasma processes have been developed for these applications. In this study, amorphous silicon oxide (a-SiO2) thin films were deposited on polycarbonate (PC) substrates by plasma enhanced chemical vapor deposition (PE-CVD) for applications as protective coatings. The coating layer deposited by low temperature plasma processes was electronically meta-stable because the process temperature was too low and the substrate temperature was always<100°C for the formation of a thermodynamically stable structure with a stoichiometric electronic bonding that can prevent the deterioration of the polymer substrate. This paper reports a coating technique for producing a denser structure with high hardness by controlling the rf bias (ion current density). The ion current density on the substrate was controlled by the rf power and an additional bias through the rf power. [ABSTRACT FROM AUTHOR]