Gas permeation study of Ti-coated, track-etched polymeric membranes

The track-etched polymeric membranes have higher permeability for hydrogen as well as carbon dioxide. In present work, we have deposited thin film of Ti having thickness 100-150 nm on polymer membrane surface using vacuum evaporation method under 10⁻⁶ Torr for filling the tracks by the Ti metal. The gas permeability of Ti-deposited membrane is modified because Ti has close affinity for hydrogen. The samples are characterized by UV-vis spectroscopy and optical microscopy. The Ti-coated, track-etched membranes are applicable for relatively higher permeation for hydrogen as well as higher selectivity and also these are technologically important for purification of hydrogen.     

Sputter deposition of semicrystalline tin dioxide films

Tin dioxide is emerging as an important material for use in copper indium gallium diselenide based solar cells. Amorphous tin dioxide may be used as a glass overlayer for covering the entire device and protecting it against water permeation. Tin dioxide is also a viable semiconductor candidate to replace the wide band gap zinc oxide window layer to improve the long-term device reliability. The film properties required by these two applications are different. Amorphous films have superior water permeation resistance while polycrystalline films generally have better charge carrier transport properties. Thus, it is important to understand how to tune the structure of tin dioxide films between amorphous and polycrystalline. Using X-ray diffraction (XRD) and Hall-effect measurements, we have studied the structure and electrical properties of tin dioxide films deposited by magnetron sputtering as a function of deposition temperature, sputtering power, feed gas composition and film thickness. Films deposited at room temperature are semicrystalline with nanometer size SnO₂ crystals embedded in an amorphous matrix. Film crystallinity increases with deposition temperature. When the films are crystalline, the X-ray diffraction intensity pattern is different than that of the powder diffraction pattern indicating that the films are textured with (101) and (211) directions oriented parallel to the surface normal. This texturing is observed on a variety of substrates including soda-lime glass (SLG), Mo-coated soda-lime glass and (100) silicon. Addition of oxygen to the sputtering gas, argon, increases the crystallinity and changes the orientation of the tin dioxide grains: (110) XRD intensity increases relative to the (101) and (211) diffraction peaks and this effect is observed both on Mo-coated SLG and (100) silicon wafers. Films with resistivities ranging between 8 mΩ cm and 800 mΩ cm could be deposited. The films are n-type with carrier concentrations in the 3 × 10¹⁸ cm^− 3 to 3 × 10²⁰ cm^− 3 range. Carrier concentration decreases when the oxygen concentration in the feed gas is above 5%. Electron mobilities range from 1 to 7 cm²/V s and increase with increasing film thickness, oxygen addition to the feed gas and film crystallinity. Electron mobilities in the 1-3 cm²/V s range can be obtained even in semicrystalline films. Initial deposition rates range from 4 nm/min at low sputtering power to 11 nm/min at higher powers. However, deposition rate decreases with deposition time by as much as 30%.     

Pulsed CO2 laser-induced gas plasma spectroscopy based on single beam splitting for trace metal analysis on a material surface

Laser-induced gas plasma spectroscopy based on pulsed CO₂ laser beam splitting has been applied to the problem of trace film analysis on the silicon surface. In this study, 2.1?J of laser energy (70% of the laser beam) was focused at a 10-degree incidence on a metal mesh attached to a sample surface containing trace metal elements in order to produce a gas plasma. The remaining part of the laser beam (approximately 30% or 0.9?J) was employed to vaporize a film which had been deposited on the material by focusing the laser beam 3?cm under the surface. In this scheme, the vaporized metal film moves into the gas plasma region, in which the dissociation and excitation takes place. Our measurements show that the detection of Cr on the silicon surface can be made with high sensitivity. The limit of detection of Cr in the silicon material was approximately 7.5?×?10¹²?atom/cm².     

Semi-automated,three-dimensional measurement of etched tracks in solid-state nuclear track detectors

We describe a new method for measuring the shapes and sizes of etched tracks in plastic or glass detectors, using a commercial digital image processing system. The method exploits the fact that in transmitted light any portion of the microscopic image of the track is in best focus when it is darkest. A minimization algorithm is used to produce a two-dimensional projected image of the three-dimensional etched track. The locus of points of maximum gradients in the image leads to a closed contour of the projected image. From this gradient image the profile, length and width of the conical etched track are automatically determined. The method is also applicable (a) to a track that penetrates a detector and has been etched until the cones from opposite surfaces are connected and (b) to a track with a curved profile due to a strongly slowing particle. The method is illustrated with measurements of tracks of 1 A GeV uranium ions in Tuffak polycarbonate and in CR-73 polycarbonate and of cosmic ray tracks in a CR-39 detector.     

Plastic substrate with gas barrier layer and transparent conductive oxide thin film for flexible displays

A novel plastic substrate for flexible displays was developed. The substrate consisted of a polycarbonate (PC) base film coated with a gas barrier layer and a transparent conductive thin film. PC with ultra-low intrinsic birefringence and high temperature dimensional stability was developed for the base film. The retardation of the PC base film was less than 1 nm at a wavelength of 550 nm (film thickness, 120 µm). Even at 180 °C, the elastic modulus was 2 GPa, and thermal shrinkage was less than 0.01%. The surface roughness of the PC base film was less than 0.5 nm. A silicon oxide (SiO_x) gas barrier layer was deposited on the PC base film by a roll-to-roll DC magnetron reactive sputtering method. The water vapor transmission rate of the SiO_x film was less than 0.05 g/m²/day at 40 °C and 100% relative humidity (RH), and the permeation of oxygen was less than 0.5 cc/m² day atm at 40 °C and 90% RH. As the transparent conductive thin film, amorphous indium zinc oxide was deposited on the SiO_x by sputtering. The transmittance was 87% and the resistivity was 3.5 × 10^− 4 ohm cm.     

气调性包装材料的制备及其性能研究

采用单体六甲基二硅氮烷(HMDS)和氧气作为反应气体,采用等离子体增强化学沉积的方法在壳聚糖、PET等基材上沉积薄膜。在薄膜的制备工艺中,改变各种工艺参数制备了阻隔薄膜,通过分析沉积薄膜厚度、傅里叶红外光谱、水蒸气和氧气的透过率,探讨了薄膜性能的变化。实验证明:等离子体输入功率以及单体的比例对薄膜的选择透过性有很大的影响,利用这种工艺可以很好地改善薄膜的气体透过性。最后对薄膜的选择透过性的机理进行了初步的探讨。     

Estimation of moisture barrier ability of thin SiNx single layer on polymer substrates prepared by Cat-CVD method

The SiNx films with the thickness of 50 nm were prepared by Cat-CVD method on the cyclic olefin copolymer (COC) and the polyethylene terephthalate (PET) substrates, and their moisture barrier abilities were evaluated. MOCON measurement method and Ca degradation test showed the moisture permeation results of 0.02 g/(m² day) for PET substrate and 0.006 g/(m² day) for COC substrate after SiNx deposition. Applying the simple model of gas barrier property, it was estimated that the Cat-CVD method achieves the high coverage ratio of over 99% for SiNx film on these substrates, and the moisture permeation rate of single SiNx film with the thickness of 50 nm was estimated to be 0.0045 g/(m² day).     

Friction and frictional tracks on thick silica films prepared by vacuum deposition

Friction and frictional tracks on 2 µm thick SiO₂ films evaporated on polymethylmethacrylate (PMMA) substrate were investigated. Diamond spherical sliders of radius 30 and 100 µm, respectively, were slid on these coatings under a load of 50 to 200g at a sliding speed of 15 cm min^–1. The static and dynamic friction coefficients for SiO₂ films were found to be 0.1 and 0.06, respectively, depending on the load and radius of the slider. For lower load and small slider radius the tracks on SiO₂ film were groove-like, and whisker-like cracks regularly grew from the edges of the tracks. For higher loads and larger slider radius, semicircular cracks in the film were regularly found behind the slider, but in thicker film (6 µm thick), circular cracks occurred. The origin of these cracks is discussed in terms of a tension zone produced around the contact area between the slider and the substrate under frictional force.     

Comparative study on dry etching of polycrystalline diamond thin films

The reactive ion etching (RIE) technique was used to etch polycrystalline diamond thin films. In this study we investigate the influence of process parameters (total pressure, rf power, gas composition) of standard capacitively coupled plasma RIE system on the etching rate of diamond films. The surface morphology of etched diamond films was characterized by Scanning Electron Microscopy and the chemical composition of the etched film part was investigated by Raman Spectroscopy.We found that the gas composition had a crucial effect on the diamond film morphology. The use of CF₄ gas resulted in flatter surfaces and lateral-like etching, while the use of pure O₂ gas resulted in needle-like structures. Addition of argon to the reactant precursors increased the ion bombardment, which in turn increased the formation of non-diamond phases. Next, increasing the rf power from 100 to 500 W increased the etching rate from 5.4 to 8.6 μm/h. In contrast to this observation, the rise of process pressure from 80 to 150 mTorr lowered the etching rate from 5.6 down to 3.6 μm/h.     

Permeation of volatile organic compounds across polymer films—Part I: Development of a sensitive test method suitable for high-barrier packaging films at very low permeant vapour pressures

The development of a permeation measurement cell based on the classical principle of permanent gas permeation testing, according to Barrer, and application of a practical procedure for permeant adsorption and subsequent gas chromatographic determination is described. For validation of the method, the permeation of d-limonene across a biaxially oriented polypropylene film (BOPP) was measured and the results were compared with those obtained according to the pouch method and with permeation data from the literature. The applicability and high sensitivity of the test method was demonstrated by measuring limonene permeation through an acrylic-coated BOPP film and a polyethylene terephthalate (PET) film and using permeants of different polarity and volatility, i.e. menthol and citronellol. From the results obtained from the uncoated and from the acrylic-coated OPP films, the permeation and diffusion coefficients of the acrylic barrier layer were calculated and shown to be three to four logarithmic orders of magnitude smaller than those of BOPP.     

Electrical characterization of CVD diamond thin films grown on silicon substrates

Diamond thin films grown on high resistivity, 100 oriented silicon substrates by the hot filament chemical vapor deposition (HFCVD) method have been characterized by four-point probe and current-voltage (through film) techniques. The resistivities of the as-grown, chemically etched and annealed samples lie in the range of 10² Ω cm to 10⁸ Ω cm. The Raman measurements on these samples indicate sp³ bonding with a sharp peak at 1332 cm⁻¹. The surface morphology as determined by scanning electron microscope shows polycrystalline films with (100) or (111) faceted structures with average grain size of ≈2.5 μm. The through film current-voltage characteristics obtained via indium contacts on these diamond films showed either rectifying or ohmic behavior. The difference in Schottky and ohmic behavior is explained on the basis of the high or low sheet resistivities measured by four-point probe technique. 5% methane to hydrogen concentration during film growth resulted in poor surface morphology, absence of sp³ bonds, and low resistivity.     

2.5 Behaviour of amorphous Ge contacts to monocrystalline silicon

The performance of evaporated amorphous Ge films (thickness $\text{～-500}\text{A}\text{?}$) contacts to etched n-and p-type silicon crystals of different resistivities are discussed. The Ge was 3 Ωcm n-type was also used but gave no difference), and as external contact to the Ge film an Au layer was evaporated. The behaviour of the aGeSi junction seems to be largely governed by interface effects (and thus depends on surface preparation), as is often the case with metal-Si junctions, but Ge gives more reproducible and less time-varying results.In the process of clarifying the function of the contact the following structures were investigated (1) aGe_pⁿSiIn (Hg), where the latter is an ohmic contact, (2) amSi_pⁿSi-metal where amSi is a surface region of the crystal which has been rendered amorphous by ion bombardment, (3) aGe_pⁿSi-metal. I-V and C-V measurements were performed. From the results we conclude that aGeSi junctions act as low-resistance contacts when fed by electron or hole currents from the crystal. The currents (holes and electrons) that are injected into the crystal from the film are limited by barriers to small current densities, usually in the range 10^?6 A cm^?2. It is suggested that the small hole currents are explained by an increase in the hole barrier, effected by positive charges at the interface or in the Ge film, which are built up when positive carriers (holes) are injected by the contact.     

聚乙烯醇水凝胶与聚乙烯薄膜的表面粘接

用铬酸氧化方法处理聚乙烯(PE)薄膜,得到了表面刻蚀均匀的化学改性薄膜;利用XPS、IR表征了薄膜表面的化学变化,采用SEM、AFM、接触角表征了薄膜表面微观结构和物理性能。制备可化学交联及物理交联成水凝胶的聚乙烯醇(PVA)溶液,与表面刻蚀的PE薄膜复合,得到了PVA水凝胶与PE薄膜的表面复合材料。通过剥离强度测定、SEM观察,表明PVA水凝胶与PE薄膜很好地粘接在一起。     

Synthesis of a polytitanocarbosilane and its conversion into inorganic compounds

The novel polytitanocarbosilane, formed by the cross-linking of polycarbosilane with titanium tetra-alkoxide, was synthesized to examine the process of converting a multielement organometallic polymer into an inorganic compound. The chemical structure of this polymer was investigated by the techniques of infra-red spectroscopy (IR), gel permeation chromatography (GPC), number average molecular weight measurements and²⁹Si nuclear magnetic resonance (NMR) measurements. The pyrolysis products in N₂ gas at 1400° C and 1700° C were the microcrystalline and crystalline states of silicon carbide and titanium carbide, respectively.     

Criteria for the occurrence of fission-fragment tracks in crystalline substances

The tracks left in minerals by fission fragments arising from the spontaneous decay of uranium impurities serve as an important method for geological dating. If it is assumed that fission tracks in crystalline substances have a structure similar to that of an amorphous phase, then four criteria concerning whether such substances will be useful for dating can be made. These are the existence of amorphization following heavy-ion impact, the identification of an etchant, a high enough crystallization temperature, and the position of the substance on a scale of amorphizability. The criteria are illustrated by applying them to apatite, cobalt titanate, and columbite. Amorphization occurred with all three following bombardment with 10 to 35 keV Kr⁺ ions. Amorphous apatite was more successfully etched with aqueous KOH than with the commonly used HNO₃, while amorphous columbite could be etched with an HF-HNO₃ mixture. The crystallization temperatures, which lay in the interval 810 to 905 K for experiments of short duration, were judged to be sufficiently high to insure track retention at the temperature of the surface of the earth over a geological time scale. The positions on a scale of amorphizability were established by noting the bombardment doses at which there was sufficient amorphization to cause the loss of one-half of an inert-gas marker when specimens were heated or etched. Considering all four criteria, it is concluded that apatite and columbite but not cobalt titanate should be useful for dating, with a similar conclusion holding for other substances which are structurally or chemically similar.This paper is dedicated to Professor C.A. Winkler of McGill University on the occasion of his sixty-fifth birthday by one of his former students (R.K.).     

A Review and Evaluation of Prediction Models of Gas Permeation for a Blended Flexible Packaging Film

Barrier properties of blended film, such as oxygen permeability, are a collective behaviour contributed by different resins. This study reviews 10 most widely used prediction models of gas permeation for two‐phase blended film along with their assumptions and the interconnection and similarities between these models. Two blended blown films, LDPE/EVOH and PET/PEN, were produced representing two different permeability ratios of matrix‐to‐disperse phase. Effective oxygen permeability of the blended films was predicted by the models and compared with measured values. Scanning electron microscopy (SEM) micrographs of both films were obtained to understand the morphology in relation to gas permeation. The Fricke model and the effective medium theory model are recommended in this study to predict effective permeability of a blended flexible packaging film. Copyright © 2016 John Wiley & Sons, Ltd.     

Aufgedampfte SiOx Barriereschichten unter monoaxialem Stress

SiO_x barrier layers under uniaxial stress For the study of the impact of defined mechanical uniaxial load on the gas barrier effect of a PET (Polyethylenterephthalate) film coated with silicon oxide SiO_x a measurement device was designed. The developed system is modular and can be combined to measure both water vapour and oxygen transmission rate. The gas permeation was measured after a given strain and after unloading the strain on relaxed films.The results show that strain above 1 % can be critical for the increase of gas permeation of coated films under constant stress and 4 % for relaxed film.     

Recording performance of discrete track patterned media fabricated by focused ion beam

We report on the recording performance of discrete track patterned media fabricated by focused ion beam (FIB). We investigated performance over a small area by spinstand read/write testing. Discrete track patterned regions show smaller magnetic track width and better signal separation between adjacent tracks and therefore higher track density than that of nonpatterned continuous media as a result of reduced side fringe effect and edge noise. We found that, at a designed groove depth of 4-8 nm, the shallow FIB etched grooves already provide good isolation between adjacent tracks, indicating the superiority of ion beam induced modification of magnetic properties in film media over physical modification of disk surface topography. This has implications for discrete track recording and media fabrication.     

Structural and electrical properties of sputtered indium-zinc oxide thin films

In this study, indium-zinc oxide (IZO) thin films have been prepared at a room temperature, 200 and 300 °C by radio frequency magnetron sputtering from a In₂O₃-12 wt.% ZnO sintered ceramic target, and their dependence of electrical and structural properties on the oxygen content in sputter gas, the substrate temperature and the post-heat treatment was investigated. X-ray diffraction measurements showed that amorphous IZO films were formed at room temperature (RT) regardless of oxygen content in sputter gas, and micro-crystalline and In₂O₃-oriented crystalline films were obtained at 200 and 300 °C, respectively. From the analysis on the electrical and the structural properties of annealed IZO films under Ar atmosphere at 200, 300, 400 and 500 °C, it was shown that oxygen content in sputter gas is a critical parameter that determines the local structure of amorphous IZO film, stability of amorphous phase as well as its eventual crystalline structure, which again decide the electrical properties of the IZO films. As-prepared amorphous IZO film deposited at RT gave specific resistivity as low as 4.48 × 10^− 4 Ω cm, and the highest mobility value amounting to 47 cm²/V s was obtained from amorphous IZO film which was deposited in 0.5% oxygen content in sputter gas and subsequently annealed at 400 °C in Ar atmosphere.     

Texturization of ZnO:Al surface by reactive ion etching in SF<Subscript>6</Subscript>/Ar,CHF<Subscript>3</Subscript>/Ar plasma for application in thin film silicon solar cells

As-deposited sputtered ZnO:Al (AZO) thin films having high transparency (T?≥?85% at 550 nm of wavelength) and good electrical properties (ρ?=?2.59?×?10^?04 Ω cm) are etched to get suitable light trapping in thin film solar cells, using reactive ion etching method in sulfur hexafluoride–argon (SF₆/Ar) plasma and trifluoromethane–argon (CHF₃/Ar) plasma to texture their surface. Though the electrical properties of the films are not affected much by the etching process but significant increment in the average haze values in the wave length range of 350–1100 nm in the etched AZO films (19.21% for SF₆/Ar and 22.07% for CHF₃/Ar plasma etched) are found compared to as-deposited AZO films (5.61%). Increment in haze value is due to more scattering of light from the textured surface. These textured substrates are used as front transparent conducting oxide electrode for the fabrication of amorphous silicon solar cells. Solar cells fabricated on etched AZO substrates show 7.76% increase in conversion efficiency compared to as-deposited AZO substrates.