Papers by Keyword: APCVD

Abstract: Electronics and energy storage industry demand production of high-quality graphene which currently still a challenge. Chemical vapor deposition (CVD) has shown promises for high-quality graphene production. However, it involves control of many parameters from different aspects such as thermal fluid, mass transport, and chemical reaction. Thermal fluid aspect plays a significant role in CVD production of graphene but yet to be explored extensively. For a tubular hot-wall CVD with the heating reactor, issue of flow instability that will prolong the existence of vortices and spiral flow until the substrate required attention. Therefore current study aims to find the optimum substrate position inside the furnace. For that purpose the gas flow streamline will be observed, and minimum axial distance of the substrate will be determined. The tubular CVD is modeled using ANSYS Fluent^®. The current model will not consider the chemical reaction involves and only single gas is used. This should be enough to seek the influence of thermal fluid aspects involves in CVD. The CVD tube will be divided into 3 sections where the middle part (furnace) was heated up to 1273K and the other two sections were kept at 300K. Gas was supplied to the tube and the distance from the furnace inlet to the point where the flow is fully developed is measured. Streamlines for the flow is also observed. The streamline shows that there is an induced secondary flow starting at the inlet which lasted until a certain axial distance. For flow with 50 sccm of flowrate needs an axial distance of 5 cm while flow with 250 sccm of flowrate needs 7 cm in order to become a smooth flow. Our results show that the placement of the substrate in the tubular hot-wall CVD required attention in CVD design. For flow with higher flowrate, it requires longer distance for the flow to become smooth and laminar and vice versa.

Abstract: Abstract: The amelioration of the efficiency of photovoltaic conversion in organic solar cells can be obtained by minimizing losses in reflection and absorption in the transparent electrode/active layer interface involving increased absorption efficiency in the active layer which can be achieved by the use of TCOs with special optical and electrical properties. Tin oxide SnO2 thin films have been prepared by APCVD method using the SnCl2 as a starting material. The surface morphology of the films deposited on glass substrates were investigated by scanning electron microscopy (SEM).The ellipsometry was used to determinate the refractive index for the films deposited at 480°C and the -sheet resistance was measured using the Four-Point probe. Transmittance of SnO2 films deposited on ITO was measured by UV-visible spectroscopy. SnO2 films prepared during 11 minutes present a sheet resistance of 19.57 Ωcm-2, transmittance higher than 80% and refractive index of 1.75 can be used as interfacial layer in organic solar cells application to minimize the reflectivity. The total reflectivity of SnO2/P3HT: PCBM obtained by using these films is less than 3%. SnO2 films can also be used as interfacial layers in inverted solar cells application.

Abstract: We have investigated the deposition of silicon films on SiO₂ patterned Si(111) substrates by atmospheric pressure chemical vapor deposition (APCVD) under standard condition. Oxidized silicon wafers with different sizes of circular and striated patterns were used as substrates for deposition of 35 μm silicon films. The influence of surface morphologies of substrates on epitaxial Si films has been discussed. The crystalline structures of the epitaxial Si films rely on the prepatterned substrates. Triangular prism-shaped grains have been obtained after depositing silicon film on substrates with circular patterns. While different size polycrystalline silicon grains appear on surfaces of Si films grown on SiO₂ regions of substrates along the axis of striated patterns. Twins defects were observed in epitaxial Si films grown on SiO₂ layers of the pretreated substrates.

Abstract: We adopted HMDS(Hexamethyledisilane) as a SiC(Silicon carbide) source material for epitaxial growth of 3C-SiC on Si substrate. Various growth profiles were investigated to optimize hetero-epitaxial growth of 3C-SiC layers. We also focused on the homogeneous film deposition of 3C-SiC on Si by employing two susceptor shapes, flat and tilted susceptors, to control a thickness of the boundary layer formed on the Si substrate. Fringe color patterns were observed on 3C-SiC layer on Si and hence it was easy to characterize the film uniformity by analyzing this color. 3C-SiC epitaxial layers were systematically analyzed by an optical microscope, a Raman spectroscopy, a SEM and an XRD.

Abstract: The effect of Fe and Ni catalysts on the synthesis of carbon nanotubes (CNTs) using atmospheric pressure chemical vapor deposition (APCVD) was investigated. Distribution of the catalyst particles over the Si substrate was analyzed by atomic force microscopy (AFM). Characterization by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopic measurements over the grown species is reported. The study clearly shows that the catalyst strongly influences morphology and microstructure of the grown CNTs.

Abstract: This paper describes the characteristics of poly (Polycrystalline) 3C-SiC grown on SiO2 and AlN buffers, respectively. The crystallinity and the bonding structure of poly 3C-SiC grown on each buffer layer were investigated according to various growth temperatures. The crystalline quality of poly 3C-SiC was improved from resulting in decrease of FWHM (Full width half maximum) of XRD and FT-IR by increasing the growth temperature. The minimum growth temperature of poly 3C-SiC was 1100 °C. The surface chemical composition and the electron mobility of poly 3C-SiC grown on each buffer layer were investigated by XPS and Hall Effect. The chemical compositions of surface of poly 3C-SiC grown on SiO2 and AlN were not different. However, their electron mobilities were 7.65 ㎝2/V.s and 14.8 ㎝2/V.s, respectively. Therefore, since the electron mobility of 3C-SiC/AlN was two times higher than that of 3C-SiC/SiO2, AlN is a suitable material, as buffer layer, for SiC growth with excellent crystalline quality.

Abstract: In this work a comparison between atmospheric pressure (AP) and low pressure (LP) carbonization as the first step in the growth process of 3C-SiC on Si substrates is presented. Three different Si substrate orientations have been studied and compared. Characterization analysis has been performed by Atomic Force Microscopy (AFM), X-ray Diffraction Spectroscopy (XRD) and Transmission Electron Microscopy (TEM). XRD and AFM analysis show a lower roughness and a better quality for LPCVD carbonized samples. Substrate orientation plays an important role both in the generation as well as in the effect of such defects in the subsequent growth process, leading to a rougher SiC surface for growth on (110) Si while micro-twin effects are limited for growth on (111) Si, resulting in an extremely flat film.

Abstract: Thin film coatings of fluorine doped tin oxide on glass were first produced in the 1940’s as part of the World War II effort. Generically known as TCO (Transparent Conductive Oxide) Coatings, the primary use was for antifogging coatings for aircraft transparencies using an electrical current to heat the glass assembly. Nearly 60 years later, these coatings are still used in cockpit glazings. Although the first generation coatings were applied using spray pyrolysis on heated glass panes, by 1990 these coatings were being applied directly on the float glass ribbon during the primary glass manufacturing operation, using Atmospheric Pressure Chemical Vapor Deposition (APCVD). As part of a color suppressed multi-layer structure, these coatings met the aesthetic and performance criteria for architectural low E glazings, and spawned new applications in electrochromic devices, heated freezer doors, radiant glass heaters, EMI/RFI Shielding, and the largest growing segment in glass – thin film photovoltaic panels. In this paper we discuss the characteristics of the on-line production, the performance characteristics of the coatings, the end use requirements, and the massive infrastructure in place worldwide to support the volume requirements. We compare the properties of SnO2:F to other emerging TCO materials such as zinc oxide.

Abstract: A selective atmospheric pressure chemical vapor deposition (APCVD) process has been developed to deposit porous polycrystalline silicon carbide (poly-SiC) thin films containing a high density of through-pores measuring 50 to 70 nm in diameter. The selective deposition process involves the formation of poly-SiC films on patterned SiO2/polysilicon thin film multilayers using a carbonization-based 3C-SiC growth process. This technique capitalizes on significant differences in the nucleation of poly-SiC on SiO2 and polysilicon surfaces in order to form mechanically-durable, chemically-stable, and well anchored porous structures, thus offering a simple and potentially more versatile alternative to direct electrochemical etching.

Abstract: SnO2 films were prepared by atmosphere pressure chemical vapor deposition (APCVD) method. The preparation, structure and photoluminescence (PL) properties of the SnO2 films were investigated. All the obtained films were polycrystalline with the rutile structure. A violet (396 nm) and a blue (446 nm) photoluminescence peaks were observed at room temperatures. The intensity of the PL peaks located at 3.13 eV decreased with increasing the annealing temperature. The emission mechanism of the SnO2 films has been investigated.