共查询到20条相似文献,搜索用时 21 毫秒
1.
A hot filament chemical vapor deposition (HFCVD) method was used to prepare Fe-Cr thin film on Si substrate. The produced layers were used as catalysts for growing carbon nanotubes (CNTs) from liquid petroleum gas (LPG) at 825 °C by thermal CVD (TCVD) method. To characterize the obtained catalysts or CNTs, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman spectroscopy were used. CNTs were grown on HFCVD derived Fe-Cr catalyst with the LPG as carbon source successfully. It was found that an annealing process on catalysts enhances the surface concentration of Cr atoms and reduces the sizes of catalyst particles. The grown CNTs on annealed sample were morphologically denser with smaller diameters compared to the as deposited one. In addition, the effect of filament temperature on CNTs was investigated. By increasing the filament temperature from 850 to 1050 °C the surface density and diameters of CNTs were improved. 相似文献
2.
Electron emission studies of CNTs grown on Ti and Ni containing amorphous carbon nanocomposite films
Carbon nanotubes (CNTs) were grown successfully on the as-deposited dual metal (Ti and Ni) embedded films using a radio frequency plasma-enhanced chemical vapor deposition system. The microstructure of CNTs grown on the dual metal films proved to be heavily dependent on the percentages of metals included, varying both in size and in density. Electron emission tests carried out on the films with CNTs grown showed that the threshold field was dependent on the surface morphology of the CNTs, with the lowest threshold field at 3.5 V/μm from 2.5% Ti/Ni film with CNTs. The field enhancement factor, β, of the emitting tips was also calculated from the Fowler–Nordheim plots, where CNTs from the 2.5% Ti/Ni film gave the highest field enhancement factor. However, it was observed that films with a single metal of either Ti or Ni did not manage to grow CNTs, possibly due to a lack of catalyst centres at the surface of the films. It was believed that the Ni nanoclusters acted as catalysts centres giving a rather uniform but randomly orientated type of CNTs. Results obtained pointed that the fabricated nanocomposite material could be a possible choice for cold cathode emitters and the Ti/Ni mixture could be an effective composite for controlling the CNT density. 相似文献
3.
S. Pisana M. Cantoro A. Parvez S. Hofmann A.C. Ferrari J. Robertson 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):1
Catalyst films undergo considerable surface morphology restructuring prior to carbon nanotube nucleation, deeply influencing the nanostructures obtained. Here we study the influence of different gaseous atmospheres on the structure of thin Fe films. The morphology is influenced by process temperature and substrate interactions and varying the gas type and pressure can control the average catalyst island height. 相似文献
4.
C.Y. Chu C.H. Huang L.M. Kao C.P. Chou C.Y. Hsu C.W. Chen D.Y. Chen 《Superlattices and Microstructures》2011
Thin gallium-doped zinc oxide (in GZO the Ga2O3 contents are approximately 3 wt%) films having different ZnO buffer layers were deposited using radio frequency (rf) magnetron sputtering. The use of a grey-based Taguchi method to determine the processing parameters of ZnO buffer layer deposition has been studied by considering multiple performance characteristics. A Taguchi method with an L9 orthogonal array, signal-to-noise (S/N) ratio, and analysis of variance (ANOVA) is employed to investigate the performance characteristics in the deposition operations. The effect and optimization of ZnO buffer deposition parameters (rf power, sputtering pressure, thickness, and annealing) on the structure, morphology, electrical resistivity, and optical transmittance of the GZO films are studied. Annealing treatment and reduction in thickness resulted in a decrease in root-mean-square (RMS) surface roughness of the ZnO buffer layer. Using the optimal ZnO buffer layer obtained by the application of the grey-based Taguchi method, the electrical resistivity of GZO films was decreased from 2.94×10−3 to 9.44×10−4 Ω cm and the optical transmittance in the visible region was slightly increased from 84.81% to 85.82%. 相似文献
5.
C.K. Lee 《Applied Surface Science》2008,254(13):4111-4117
A diamond film was deposited on silicon substrate using hot filament chemical vapor deposition (HFCVD), and H2 and O2 gases were added to the deposition process for comparison. This work evaluates how adding H2 and O2 affects the corrosion and wear-corrosion resistance characteristics of diamond films deposited on silicon substrate. The type of atomic bonding, structure, and surface morphologies of various diamond films were analyzed by Raman spectrometry, X-ray diffraction (XRD) and atomic force microscopy (AFM). Additionally, the mechanical characteristics of diamond films were studied using a precision nano-indentation test instrument. The corrosion and wear-corrosion resistance of diamond films were studied in 1 M H2SO4 + 1 M NaCl solution by electrochemical polarization. The experimental results show that the diamond film with added H2 had a denser surface and a more obvious diamond phase with sp3 bonding than the as-deposited HFCVD diamond film, effectively increasing the hardness, improving the surface structure and thereby improving corrosion and wear-corrosion resistance properties. However, the diamond film with added O2 had more sp2 and fewer sp3 bonds than the as-deposited HFCVD diamond film, corresponding to reduced corrosion and wear-corrosion resistance. 相似文献
6.
A. Policicchio G. Chiarello V. Formoso R.G. Agostino D. Gournis 《Surface science》2007,601(13):2823-2827
The electronic and chemical structure of carbon nanotubes synthesized by decomposition of acetylene over Fe-Co bimetallic catalysts in different growth conditions, were analyzed by valence band photoelectron spectroscopy and scanning electron microscopy. A clear relationship between the bonding features and the growth condition allowed us to determine the key parameters in terms of temperature, growth time and catalyst content. Furthermore, the analysis allowed a determination of the byproducts. 相似文献
7.
Aihua ZhongJin Tan Huali HuangShengchang Chen Man WangSai Xu 《Applied Surface Science》2011,257(9):4051-4055
N-Al co-doped ZnO films with various thicknesses were deposited on glass substrates by ultrasonic spray pyrolysis (USP). The crystalline microstructure, morphology, distribution of elements and photoluminescence properties of ZnO films were characterized by X-ray diffraction (XRD), field emission scanning microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and photoluminescence (PL) spectroscopy. The XRD and FESEM results show that with the increase of film thickness the grain size increases and the grain shape changes from regular hexagonal sheet-like to wedge-shaped, even pyramidal. The PL spectra illustrate that there is an obvious red-shift for the emission center from ultraviolet to blue region, and the intensities of defects emissions increase with the increase of thickness. In addition, the electrical properties are proved to be strongly affected by film thickness. 相似文献
8.
《Physics letters. A》2020,384(4):126097
In order to develop high efficiency solar cell device by replacing conventional hazardous CdS window layer by environmental friendly Zn-based buffer layer, ZnSe thin films of thickness 100 nm were grown on glass and ITO substrates employing electron beam evaporation technique followed by air and vacuum annealing at temperature 100 °C, 200 °C and 300 °C. As-grown and annealed films were subjected to characterization tools like XRD, UV-Vis spectrophotometer, SEM, EDS and source meter. Structural results reveal the amorphous phase, SEM images indicate uniform deposition without pin holes and EDS patterns confirm the deposition. Transmittance is observed to be high in visible region and band gap is found to change with temperature of the treatment and I-V measurements demonstrate ohmic nature. On the basis of optimized results, the films annealed at 200 °C in vacuum may be used as buffer layer to develop high efficiency Cd-based and CIGS thin film solar cells. 相似文献
9.
A.P. Alekhin A.M. Markeev A.S. Mitiaev A.A. Sigarev V.F. Toknova 《Applied Surface Science》2010,257(1):186-191
A dependence of structural properties of TiO2 films grown on both Si- and Ti-substrates by atomic layer deposition (ALD) at the temperature range of 250-300 °C from titanium ethoxide and water on the number of reaction cycles N was investigated using Fourier-transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD). TiO2 films grown on both Si- and Ti-substrates revealed amorphous structure at low values of N < 400. However, an increase of N up to values 400-3600 resulted in the growth of polycrystalline TiO2 with structure of anatase on both types of substrates and according to XRD-measurements the sizes of crystallites rose with the increase of N. The maximum anatase crystallite size for TiO2 grown on Ti-substrate was found to be on ∼35% lower in comparing with that for TiO2 grown on Si-substrate. A use of titanium methoxide as a Ti precursor with the ligand size smaller than in case of titanium ethoxide allowed to observe an influence of the ligand size on both the growth per cycle and structural properties of TiO2. The average growth per cycle of TiO2 deposited from titanium methoxide and water (0.052 ± 0.01 nm/cycle) was essentially higher than that for TiO2 grown from titanium ethoxide and water (0.043 ± 0.01 nm/cycle). Ligands of smaller sizes were found to promote the higher crystallinity of TiO2 in comparison with the case of using the titanium precursor with ligands of bigger sizes. 相似文献
10.
HfO2 films were grown by atomic layer deposition from HfCl4 and H2O on Si(1 0 0), Si(1 1 1) and amorphous SiO2 substrates at 180-750 °C and the effect of deposition temperature and film thickness on the growth rate and optical properties of the film material was studied. Crystallization, texture development and surface roughening were demonstrated to result in a noticeable growth rate increase with increasing film thickness. Highest surface roughness values were determined for the films deposited at 350-450 °C on all substrates used. The density of the film material increased with the concentration of crystalline phase but, within experimental uncertainty, was independent of orientation and sizes of crystallites in polycrystalline films. Refractive index increased with the material density. In addition, the refractive index values that were calculated from the transmission spectra depended on the surface roughness and crystallite sizes because the light scattering, which directly influenced the extinction coefficient, caused also a decrease of the refractive index determined in this way. 相似文献
11.
Surface morphology, growth rate and quality of diamond films synthesized in hot filament CVD system under various methane concentrations 总被引:1,自引:0,他引:1
Hot filament chemical vapor deposition (CVD) technique has been used to deposit diamond films on silicon substrate. In the present study, diamond films were grown at various vol.% CH4 in H2 from 0.5% to 3.5%, at substrate temperature and pressure of 850 °C and 80 torr, respectively. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were employed to analyze the properties of deposited films. The formation of methyl radicals as a function of vol.% CH4 not only changes film morphology but also increase film growth rate. At low, intermediate and high vol.% CH4, cluster, faceted cubes and pyramidal features growth, were dominant. By increasing vol.% CH4 from 0.5% to 3.5%, as the growth rate improved from ∼0.25 μm/h to ∼2.0 μm/h. Raman studies features revealed high purity diamond films at intermediate range of vol.% CH4 and grain density increased by increasing CH4 concentration. The present study represents experimentally surface morphology, growth rate and quality of diamond films grown in hot filament CVD system at various CH4 concentrations. 相似文献
12.
Duy-Thach PhanGwiy-Sang Chung 《Applied Surface Science》2011,257(8):3285-3290
Zinc oxide (ZnO) thin films were deposited on a polycrystalline (poly) 3C-SiC buffer layer using RF magnetron sputtering and a sol-gel method. The post-deposition annealing was performed on ZnO thin films prepared using both methods. The formation of ZnO piezoelectric thin films with less residual stress was due to a close lattice mismatch of the ZnO and SiC layers as obtained by the sputtering method. Nanocrystalline, porous ZnO film prepared using the sol-gel method showed strong ultraviolet UV emission at a wavelength of 380 nm. The 3C-SiC buffer layer improved the optical and piezoelectric properties of the ZnO film produced by the two deposition methods. Moreover, the different structures of the ZnO films on the 3C-SiC intermediate layer caused by the different deposition techniques were also considered and discussed. 相似文献
13.
Influences of annealing on structural and compositional properties of Al_2O_3 thin films grown on 4H–SiC by atomic layer deposition
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Annealing effects on structural and compositional performances of Al_2O_3 thin films on 4H–Si C substrates are studied comprehensively. The Al_2O_3 films are grown by atomic layer deposition through using trimethylaluminum and H_2 O as precursors at 300?C, and annealed at various temperatures in ambient N_2 for 1 min. The Al_2O_3 film transits from amorphous phase to crystalline phase as annealing temperature increases from 750?C to 768?C. The refractive index increases with annealing temperature rising, which indicates that densification occurs during annealing. The densification and grain formation of the film upon annealing are due to crystallization which is relative with second-nearest-neighbor coordination variation according to the x-ray photoelectron spectroscopy(XPS). Although the binding energies of Al 2p and O 1s increase together during crystallization, separations between Al 2p and O 1s are identical between as-deposited and annealed sample, which suggests that the nearest-neighbour coordination is similar. 相似文献
14.
Yuan-Li HuangHsi-Wen Tien Chen-Chi M. Ma Chih-Chun TengYi-Hsiuan Yu Shin-Yi YangMing-Hsiung Wei Sheng-Yen Wu 《Applied Surface Science》2011,258(1):136-142
In this study, we fabricated optically transparent and electrically conductive multi-walled carbon nanotube (MWCNT) thin films using a spray-coating technique. The transparency and the electrical resistance of thin film are dependent on the nanotube content deposited on the polyethylene terephthalate (PET) substrate. Poly(acrylic acid) (PAA) and poly(N-vinyl pyrrolidone) (PVP) were used as adhesion promoters to improve MWCNT coating more significantly. The cross-linked polymer resulted in a superior bond between the MWCNTs and the substrates. The surface electrical resistance was significantly lower than the original sheet after nitric acid (HNO3) treatment because of the removed surfactant and the increased interconnecting networks of MWCNT bundles, thus improving the electrical and optical properties of the films. Stronger interaction between the MWCNTs and the substrates resulted in lower decomposition of the polymer chain and less amounts of MWCNTs separated into the HNO3 solution. The lower sheet electrical resistance of PVP/PAA-g-MWCNT conductive films on the PET substrate was because of a more complete conductive path with the cross-linked polymer than that without. Such an improved sheet of electrical resistance varied from 8.83 × 104 Ω/□ to 2.65 × 103 Ω/□ with 5.0 wt.% PVP/PAA-g-MWCNT sprayed on the PET after acid treatment. 相似文献
15.
Duy-Thach PhanGwiy-Sang Chung 《Current Applied Physics》2012,12(2):521-524
Zinc oxide (ZnO) thin films were deposited onto a polycrystalline (poly) 3C-SiC buffer layer for surface acoustic wave (SAW) ultraviolet (UV) sensing using a magnetron sputtering system. X-ray diffraction (XRD) and photoluminescence (PL) spectra showed that the ZnO film grown on 3C-SiC/Si had a dominant c-axis orientation, a lower residual stress, and higher intensity of luminescence at 380 nm of ZnO thin film. The SAW resonator UV detector were fabricated on ZnO/Si structures with a 3C-SiC buffer layer. The SAW resonator exposed under UV illumination had a linear response with sensitivity of 85 Hz/(μW/cm2) in ZnO/3C-SiC/Si structures, as compared to 25 Hz/(μW/cm2) in ZnO/Si structures with UV intensity varied until 600 μW/cm2. 相似文献
16.
T. Somanathan 《Applied Surface Science》2008,254(17):5643-5647
Iron, cobalt and a mixture of iron and cobalt incorporated mesoporous MCM-41 molecular sieves were synthesised by hydrothermal method and used to investigate the rules governing their nanotube producing activity. The catalysts were characterised by XRD and N2 sorption studies. The effect of the catalysts has been investigated for the production of carbon nanotubes at an optimised temperature 750 °C with flow rate of N2 and C2H2 is 140 and 60 ml/min, respectively for a reaction time 10 min. Fe-Co-MCM-41 catalyst was selective for carbon nanotubes with low amount of amorphous carbon with increase in single-walled carbon nanotubes (SWNTs) yield at 750 °C. Formation of nanotubes was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Transmission electron microscope and Raman spectrum was used to follow the quality and nature of carbon nanotubes formed and the graphitic layers and disordered band, which shows the clear evidence for the formation of SWNTs, respectively. The result propose that the diameter of the nanotubes in the range of 0.78-1.35 nm. Using our optimised conditions for this system, Fe-Co-MCM-41 showed the best results for selective SWNTs with high yield when compared with Fe-MCM-41 and Co-MCM-41. 相似文献
17.
Nickel films of different thickness ranging from 15 nm to 350 nm were deposited on glass substrates, at different substrate temperatures (313-600 K) under UHV condition. The nano-structure of the films was obtained, using X-ray diffraction (XRD) and atomic force microscopy (AFM). The nano-strain in these films was obtained using the Warren-Averbach method. Their optical properties were measured by spectrophotometry in the spectral range of 190-2500 nm. Kramers-Kronig method was used for the analysis of the reflectivity curves. The absorption peaks of Ni thin films at ∼1.4 eV (transition between the bands near W and K symmetry points) and ∼5.0 eV (transition from L2′ to L1 upper) are observed, with an additional bump at about 2 eV. The over-layer thickness was calculated to be less than 3.0 nm, using the Transfer Matrix method. The changes in optical data are related to different phenomena, such as different crystallographic orientations of the grains in these polycrystalline films (film texture), nano-strain, and film surface roughness. 相似文献
18.
C.M. Shin J.H. Heo C.R. Kim J.H. Chang W.J. Lee J.L. Zhao 《Applied Surface Science》2009,255(20):8501-8505
In this study, the effects of the annealing duration of a zinc oxide (ZnO) buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process are discussed. A ZnO buffer layer was deposited on p-type Si (1 1 1) substrates by the metal organic chemical vapor deposition (MOCVD) method. After that, ZnO rods were grown on the ZnO-buffer/Si (1 1 1) substrate by a hydrothermal process. In order to determine the optimum annealing duration of the buffer layer for the growth of ZnO rods, durations ranging from 0.5 to 30 min were tried. The morphology and crystal structure of the ZnO/ZnO-buffer/Si (1 1 1) were measured by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The optical properties were investigated by photoluminescence (PL) measurement. 相似文献
19.
Marcelo Motta Ian Kinloch Anna Moisala Venugoplan Premnath Martin Pick Alan Windle 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):40
We have recently introduced a method for the continuous spinning of carbon nanotube fibres and films directly from the gas phase of a chemical vapour deposition furnace [Y. Li, et al., Science 304 (2004) 276]. In this work the effect of the process parameters on the ability to spin continuously is studied, with particular focus on the carrier gas and feedstock flow rates. Catalyst dilution by high carrier gas flow rates led to smaller diameter nanotubes but these conditions are found the hardest to spin. 相似文献