Papers by Keyword: Thermal CVD

Abstract: A hot filament thermal chemical vapor deposition (CVD) reactor was used to deposit solid thin films on stainless steel 316 (SS 316) and stainless steel 201 (SS 201) substrates at different flow rates of acetylene (C₂H₂) gas. The variation of thin film deposition rate with the variation of gas flow rate has been investigated experimentally. During experiments are conducted under gas flow rate (1-5) lit/min gas flow rate, duration of deposition (10-60 min), pressure (0.2-1 bar), average surface roughness (0.3-1.05) µm and temperature 800 °C considered. Experimental results show that deposition rate on SS 316 and SS 201 increases with the increase in gas flow rate. The deposition rate also shows increasing trend with pressure and duration of deposition. Under the above mentioned experimental conditions deposition is found to be maximum of SS-316 compared to SS-201. In relation to roughness the maximum deposition is found at 0.5 microns but comparing the both materials -316 and-201 highest of deposition rate is obtained from SS-316.

Abstract: ZnO in various nanostructures forms have been widely studied for the application such as in solar cells, light emitting diodes, UV sensors and so on. In this paper, we have successfully deposited ZnO nanotetrapods using thermal chemical vapour deposition (TCVD) technique on layer-by-layer ZnO seeded catalyst, with Zn powder and O₂ gas as source materials. We demonstrate that by using double furnace TCVD system, ZnO nanotetrapods can be deposited at lower temperature than the vapour temperature of the Zn powder. In this paper we report the effect of different deposition temperature (450 °C to 600 °C) on the surface morphologies, crystalline structure and optical properties of the ZnO nanotetrapods. FE-SEM micrographs show that the length of the nanotetrapods arms decreases with the increase of the deposition temperature. PL spectra show that the visible emission are very low compared to the UV emission which indicates that the ZnO tetrapod have very low intrinsic defect. The highest UV emission intensity is given by the sample deposited at 500 °C.

Abstract: Amorphous carbon (a:C) were successfully deposited on the silicon surfaces via bias assisted pyrolysis-CVD in the range between 350oC to 500oC with constant of negative bias -50V in 1 hour deposition. The heated of palm oil at about 150oC was vaporized then used for deposited onto p-type silicon substrates. The deposited thin films were characterized by using field emission scanning electron microscopic (FESEM), energy dispersive analyser x-ray (EDAX). We have found carbon element at about 0.15 keV from EDAX with surface morphology formed a nano-ball like structure at 450oC of palm oil precursor. These results indicated deformation of physical and structural thin films caused by applied negative bias and the temperature.

Abstract: In this paper we address sensitivity of SnO2 thin film deposited by thermal chemical vapor deposition in terms of its behavior towards humidity variations. The structural, optical and electrical properties of SnO2 thin film deposit at different substrate temperature grown by thermal chemical vapor deposition (CVD) are also reviewed. FESEM image reveal smallest particle size of SnO2 at substrate temperature 500°C. Pl measurement shows red shift of SnO2 at substrate temperature 500°C. All thin film performing slightly linear sensitivities towards relative humidity (RH%).

Abstract: ZnO heterostructures have been successfully synthesized using thermal chemical vapor deposition method. Zinc powder and oxygen were used as the starting materials, while argon gas was supplied as the carrier gas. Different types of nanostructures were deposited on layer-by-layer ZnO seeded catalyst; which its structures depended on the position of the substrates during the deposition process. Substrates at position C which is located 3 cm from the source shows uniformly distributed ZnO nanorods. XRD pattern also shows that sample C shows (0 0 2) diffraction peak. PL spectra indicates that the ZnO have two peaks, which is UV peak centered at 380 nm and visible peak centered at about 550 nm.

Abstract: Iodine doped amorphous carbon (a-C: I) thin films were prepared by using Thermal Chemical Vapor Deposition (CVD) with deposition temperature ranging from 5000C to 7000C. The physical and electrical properties of deposited a-C:I thin films were characterized by Raman spectroscope and Solar Simulator system. The presence of 2 peaks known as Raman D peaks and Raman G peaks ensure the amorphous structure of carbon (C). As deposition temperature increase, the ID/IG ratio shows difference value, which indicates the effects of the temperature towards the a-C: I structures. An ohmic graph was obtained for the IV measurement, and the conductivity varies from 10-4 to 101 Scm-1. The photoresponse was also determined for all samples. As a reference, an undoped a-C thin film was prepared to differentiate the characteristic between a-C and a-C: I.

Abstract: The as deposited amorphous carbon (a-C) thin films were successfully deposited by using ethanol and palm oil precursors via a novel bias assisted pyrolysis-CVD ranging from 300oC to 550oC with constant of negative bias -40V and -50V in 3h and 1h deposition. The thin films were characterized by atomic force microscopic (AFM), field emission scanning electron microscopic (FESEM), and I-V measurement. The resistivity of as deposited a-C thin films using ethanol precursor at 300oC, 350oC, 400oC and 500oC were 9.57 x106Ω/cm, 9.44 x106Ω/cm, 9.81 x105Ω/cm and 337738.124 Ω/cm respectively and conductivity were 1.00445 x10-7 cm/Ω, 1.0593 x10-7,cm/Ω, 1.01963x10-6 cm/Ω, and 2.67825 x10-6 cm/Ω. For palm oil precursor (400oC-550oC), the resistivity were calculated, 3.83x104Ω/cm, 1.32x104Ω/cm, 3.77x104Ω/cm, and 4.19x105Ω/cm respectively while conductivity were 2.61 x 10- 5 cm/Ω, 7.60 x 10- 5 cm/Ω, 2.65 x 10- 5 cm/Ω, and 2.39 x 10- 6 cm/Ω. The samples showed all the resistivity values were in the range of semiconductor. The results showed that increasing temperature decreased resistivity of thin films for ethanol precursor. The resistivity thin films obtained from palm oil precursor were smaller as compared with ethanol precursor.

Abstract: Carbon nanotubes have many applications and therefore widely produced. However, it is limited due to the high production cost. In this paper, by preparing the CNTs using the Thermal Chemical Vapor Deposition method, CNTs were synthesized with a low cost method since palm oil is used as the precursor which is a biodegradable and cheap source. The aerosol or spray pyrolysis method is used for single stage and double stage TCVD method. Then, the samples were both collected at deposition temperature of 750°C and were characterized using Brunauer, Emmett and Teller (BET) method. Since CNTs are said to have high surface area therefore BET method is used to prove this fact. Results showed that by using double stage TCVD method, more CNTs were synthesized compared to single stage TCVD method which produced more impurities namely amorphous carbon. CNTs also have higher surface area compared to amorphous carbon. To support this result, the images of the CNTs produced by same method but different parameters were characterized with field emission scanning electron microscope (FE-SEM) and the raman spectra was determined by the raman spectroscopy characterization.

Abstract: A hot filament thermal chemical vapor deposition (CVD) reactor was used to deposit solid thin films on stainless steel 316 (SS 316) substrates at different flow rates of natural gas. The variation of thin film deposition rate with the variation of gas flow rate has been investigated experimentally. During experiment, the effect of gap between activation heater and substrate on the deposition rate has also been observed. Results show that deposition rate on SS 316 increases with the increase in gas flow rate. It is also observed that deposition rate increases with the decrease in gap between activation heater and substrate within the observed range. In addition, friction coefficient and wear rate of SS 316 sliding against SS 304 under different normal loads are also investigated before and after deposition. The experimental results reveal that improved friction coefficient and wear rate are obtained after deposition as compared to that of before deposition.

Abstract: Carbon nanotube (CNT) gas sensors for NOx gas detection were prepared. CNTs were grown on an Al2O3 substrate with interdigital Pt-electrodes (Al2O3 ceramic substrate) using both pulsed laser deposition (PLD) and thermal chemical vapor deposition (CVD) method. In this method, Al buffer layer and Fe catalytic thin film were prepared on the substrate by PLD method and then CNTs were grown by thermal CVD method. Surface images of CNTs on the substrates were observed by SEM, and the gas sensing property specific to NO gas was measured. Resistance of the prepared CNTs gas sensor decreased with increase of sensor temperature, and it decreased with increase of NO gas concentration at room temperature.