Lin Li; Shibing Tian; Ruhao Pan; Chao Wang; Chi Sun; Junjie Li; Changzhi Gu
Abstract
The uniformity in temperature-field of the hot filament chemical vapor deposition (HFCVD) system is of great importance since it is a critical parameter that determines the quality of the deposited films. In fact, the temperature-field is mainly filament distribution dependent. In conventional analysis ...
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The uniformity in temperature-field of the hot filament chemical vapor deposition (HFCVD) system is of great importance since it is a critical parameter that determines the quality of the deposited films. In fact, the temperature-field is mainly filament distribution dependent. In conventional analysis method, the filament array usually has an equal-space distribution, which leads to a remarkable edge effect and consequently unable to obtain large area uniformity in temperature-field in HFCVD for high-quality thin film deposition. Here, we proposed theoretically an asymmetrical filament distribution to reduce the edge-effect of temperature field. The adjacent filament distance was optimized by using numerical simulation based on heat-transfer theory. Based the optimized condition, temperature difference as low as 13 K between the center and edge region of the filament arrays can be achieved in 100-mm substrate, which is only one tenth of the temperature difference of that in the case that the filaments were evenly distributed. Thus unequal-space distribution can be employed to enhance the uniformity in temperature field of the HFVCD system in favor of the growth of high quality thin films in large area.
Anna Maria Coclite
Abstract
Functional organic thin films (< 100 nm) are typical components of current devices in a variety of fields, including microelectronics, biotechnology and microfluidics. The need for miniaturization and structuration has boosted the development of advanced thin film growth techniques that can be easily ...
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Functional organic thin films (< 100 nm) are typical components of current devices in a variety of fields, including microelectronics, biotechnology and microfluidics. The need for miniaturization and structuration has boosted the development of advanced thin film growth techniques that can be easily implemented in the manufacturing steps of current device production. This review aims at presenting the latest progresses made in the field of chemical vapor deposition (CVD) methods of organic thin films. In CVD processes, the chemicals are delivered through the vapor-phase to the substrate, without the use of solvents, with the advantage of enlarging the applicability of polymer thin films to fields where the presence of solvent is detrimental. Among other methods, the initiated Chemical Vapor Deposition (iCVD) will be reviewed. High control over chemical composition, structure and film functionality has been largely demonstrated by iCVD. This technique allows coating virtually any substrate with conformal polymers at very low energy consumption. The specific chemical composition and the nanoengineered thickness control are desirable parameters for driving application-specific properties into the material. Further development of this field will certainly lead to progresses on the use of polymers in functional devices, as electrolytes, stimuli-responsive materials, encapsulants for drug-delivery and as membranes or barriers for permeation.
Abhishek Kumar Arya; Bhanu Pratap Singh; Jeevan Jyoti; Santwana Pati; S.R. Dhakate
Abstract
Vertically aligned carbon nanotube (VACNT) arrays are widely studied because of their immense potential in a wide range of applications. In order to tailor the properties of carbon nanotubes (CNTs) for a particular application, vertical alignment in the form of sheet is a major breakthrough. Herein ...
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Vertically aligned carbon nanotube (VACNT) arrays are widely studied because of their immense potential in a wide range of applications. In order to tailor the properties of carbon nanotubes (CNTs) for a particular application, vertical alignment in the form of sheet is a major breakthrough. Herein we report an economic and effective strategy developed to synthesise aligned multiwalled carbon nanotube sheets using Al powder as buffer layer. We achieved easy growth of VACNTs sheets using toluene/ferrocene solution in a two-zone furnace by chemical vapor deposition method. First zone was set at temperature 200 ° C and other zone was set at temperature 750 ° C for the synthesis of VACNTs. Almost 500 µm long VACNT sheet was grown. We observed the significant growth of VACNT sheet on Al powdered quartz substrate in nitrogen medium. Uniform length of CNTs was maintained all over the sheet and additionally nitrogen is an economical alternative rather than other inert gases.
Vaishali S. Waman; Azam H. Mayabadi; Mahesh M. Kamble; Bharat B. Gabhale; Adinath M. Funde; Vasant G. Sathe; Habib M. Pathan; Sandesh R. Jadkar
Abstract
We investigated the effect of Xe dilution of silane on structural, optical and electrical properties of nanocrystalline Si films deposited by HW-CVD. With increase in Xe dilution of silane nanocrystalline-to-amorphous transition or amorphization has been observed in nanocrystalline Si films. The amorphization ...
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We investigated the effect of Xe dilution of silane on structural, optical and electrical properties of nanocrystalline Si films deposited by HW-CVD. With increase in Xe dilution of silane nanocrystalline-to-amorphous transition or amorphization has been observed in nanocrystalline Si films. The amorphization has been confirmed from dark and photoconductivity measurement, Raman spectroscopy, low angle XRD and atomic force microscopy analysis. The FTIR spectroscopy analysis showed that with increase in Xe dilution of silane, in addition to di-hydrogen [Si-H2] and poly-hydrogen [(Si-H2)n] complexes, hydrogen incorporated in these films in mono-hydrogen [Si-H] bonded species. The hydrogen content was found < 5 at. % over the entire range of Xe dilution of silane studied and it increases with increase in Xe dilution of silane. On the other hand, ETauc and E04 show decreasing trend with increasing Xe dilution of silane. The ETauc decreases from 2.4eV to 1.9eV whereas E04 decreases from 2.9eV to 2.3eV. The optical band gap values estimated from E04 method are found higher than ETauc values calculated from Tauc’s method. Finally, it has been concluded that Xe dilution of silane in HW-CVD enhances the deposition rate but has adverse effect on the crystallinity of nanocrystalline Si films.
Visittapong Yordsri; Winadda Wongwiriyapan; Chanchana Thanachayanont
Abstract
A facile growth of carbon nanotubes (CNTs) was facilitated by the use of direct-current plating technique for catalyst preparation. Ni nanoparticles (NPs) were deposited on Cu foil at different applied voltages of 1.0, 1.5 and 2.0 V. The Ni-deposited foil was subsequently used as catalyst for CNTs synthesis ...
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A facile growth of carbon nanotubes (CNTs) was facilitated by the use of direct-current plating technique for catalyst preparation. Ni nanoparticles (NPs) were deposited on Cu foil at different applied voltages of 1.0, 1.5 and 2.0 V. The Ni-deposited foil was subsequently used as catalyst for CNTs synthesis by chemical vapour deposition (CVD) method. CVD was carried out at 800 ºC using ethanol as carbon source. A voltage of 1.5 V was the optimum condition to deposit uniform Ni NPs that had a narrow size distribution of 55±3 nm, which in turn, yielded synthesized CNTs with a uniform diameter of approximately 60±5 nm with graphitic layers parallel to the CNTs axis. On the other hand, electroplated Ni at 1.0 V produced CNTs with graphitic layers at an angle to the CNTs axis, while electroplated Ni at 2.0 V produced curly CNTs with a wide distribution of diameters. These results show that Ni NPs size distribution could be controlled by electroplated voltage. Our observation was that Ni NPs with a narrow distribution of sizes and a uniform diameter is a key to uniform CNT synthesis. Furthermore, the synthesized CNTs electrode shows a faradic pseudo capacitance property, which can be attributed to the existence of oxidized Ni NPs. These results propose that the synthesized CNTs are promising materials for future super capacitor application. The optimization of ratio of Ni NPs and CNTs may improve the supercapacitors performance.
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