共查询到11条相似文献,搜索用时 0 毫秒
1.
Yongsheng Liu Litong Zhang Qingfeng Zeng Wenbin Yang Siwei Li 《Applied Surface Science》2009,255(11):5729-5735
Boron carbide was prepared by low pressure chemical vapor deposition (LPCVD) from BCl3-CH4-H2 system. The deposition process conditions were optimized through using a uniform design method and regression analysis. The regression model of the deposition rate was established. The influences of deposition temperature (T), deposition time (t), inlet BCl3/CH4 gas ratio (δ), and inlet H2/CH4 gas ratio (θ) on deposition rate and microstructure of the coatings were investigated. The optimized deposition parameters were obtained theoretically. The morphologies, phases, microstructure and composition of deposits were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman micro-spectroscopy, transmission electron microscopy (TEM), energy dispersive spectra (EDS), and Auger electron spectra (AES), the results showed that different boron carbides were produced by three kinds of deposition mechanisms. 相似文献
2.
Tawfik A. Saleh 《Applied Surface Science》2011,257(17):7746-7751
The nature of multi-walled carbon nanotubes (MWCNTs) varies with the change in oxidation conditions. In this work, the effect of treatment temperatures on the acidity of MWCNTs was studied. Oxidation was performed by refluxing the MWCNTs in nitric acid or mixtures of sulfuric acid and nitric acid at different temperatures. After oxidative treatment, a quantitative characterization of o-MWCNTs has been performed using acid-base titrations which show that the number of surface acidic functional groups increased by increasing the treatment temperatures. Energy dispersive X-ray (EDX) measurements show that the oxygen content increased with increasing treatment temperatures. Fourier transform infrared absorption spectroscopy (FTIR) was used for qualitative characterization. It has been demonstrated that the acidity is a function of the type of oxidizing agent used and the treatment temperatures. Due to the importance in attachment strategies and functionalization, this study adds to the global discussion of the possibility of controlling the MWCNTs’ surface chemistry which plays a crucial role in determining its reactivity. 相似文献
3.
C2H4 mediations were used to modify the Stranski-Krastanow growth mode of Ge dots on Si(0 0 1) at 550 °C by ultra-high vacuum chemical vapor deposition. With appropriate C2H4-mediation to modify the Si surface, the elongated Ge hut clusters can be transformed to highly uniform Ge domes with a high Ge composition at the core. These C2H4-mediated Ge dots, almost bounded by {1 1 3} facets, have an average diameter and height of 55 and 9 nm, respectively. We propose two major mechanisms to depict the formation of these C2H4-mediated Ge dots: (i) an almost hydrogen-passivated Si surface to limit the nucleation sites for dot formation, and (ii) the incorporation of Ge atoms, repelled by the C-rich areas, into the existing Ge dots. This work provides a useful scheme to tune the topography of Ge dots in an UHV/CVD condition for possible optoelectronic applications. 相似文献
4.
Hydrogenated amorphous carbon nitride (a-CN:H) thin films were deposited by hot-wire chemical vapor deposition (HWCVD) using the gas mixture of CH4, NH3 and H2 precursor gases. The structural and electronic environments studies of H2 diluted a-CN:H films were carried out by Raman spectroscopy and X-ray photoelectron spectroscopy. The nitrogen content increases while the total carbon contents decreases with increase in H2 flow rate from 0 sccm to 20 sccm in the a-CN:H films. Moreover, the detail analysis of the carbon core orbital, valence band and hole states of a-CN:H were discussed with different H2 flow rate. 相似文献
5.
Xingwang Zhang 《Applied Surface Science》2008,254(8):2406-2412
There are two major difficulties in the TiO2 liquid-solid photocatalytic system: effective immobilization of the TiO2 particles; and improving the catalytic activity under visible light. To simultaneously solve these two problems, Fe2O3-TiO2 coatings supported on activated carbon fiber (ACF), have been prepared in one step by a convenient and efficient method—metal organic chemical vapor deposition (MOCVD). XRD results revealed that Fe2O3-TiO2 coatings mainly composed of anatase TiO2, α-Fe2O3 phases and little Fe2Ti3O9. The pore structure of ACF was preserved well after loading with Fe2O3-TiO2 coatings. UV-vis diffuse reflectance spectra showed a slight shift to longer wavelengths and an enhancement of the absorption in the visible region for Fe2O3-TiO2 coatings, compared to the pure TiO2 sample. A moderate Fe2O3-TiO2 loading (13.7 wt%) was beneficial to mineralizing wastewater because the intermediates could be adsorbed onto the surface of photocatalyst following decomposition. The stable performance revealed that the Fe2O3-TiO2 coatings were strongly adhered to the ACF surface, and the as prepared catalysts could be reused showing potential application for wastewater treatment. 相似文献
6.
Md. Nizam Uddin Osama A. Fouad Masaaki Yamazato Masamitsu Nagano 《Applied Surface Science》2005,240(1-4):120-130
Carbon nitride thin films were deposited on Si(1 0 0) substrate by microwave plasma-enhanced chemical vapor deposition (PECVD). Hexamethylenetetramine (HMTA) was used as carbon and nitrogen source while N2 gas was used as both nitrogen source and carrier gas. The sp3-bonded C---N structure in HMTA was considered significantly in the precursor selection. X-ray diffraction analysis indicated that the film was a mixture of crystalline - and β-C3N4 as well as graphitic-C3N4 and β-Si3N4 which were not easily distinguished. Raman spectroscopy also suggested the existence of - and β-C3N4 in the films. X-ray photoelectron spectroscopy study indicated the presence of sp2- and sp3-bonded C---N structures in the films while sp3C---N bonding structure predominated to the sp2 C---N bonding structure in the bulk composition of the films. N was also found to be bound to Si atoms in the films. The product was, therefore, described as CNx:Si, where x depends on the film depth, with some evidences of crystalline C3N4 formation. 相似文献
7.
M.I. Pech-Canul J.L. de la Pe?a A.L. Leal-Cruz 《Applied Physics A: Materials Science & Processing》2007,89(3):729-735
Silicon nitride (Si3N4) and oxynitride (Si2N2O) were deposited by chemical vapor infiltration (CVI) through a novel route involving the in-situ thermal decomposition of
Na2SiF6 in commercial nitrogen precursors containing impurity oxygen. In addition, the quantitative effect of processing time (30,
60, 90, 120 min), temperature (1000, 1100, 1200 and 1300 °C), nitrogen precursor (N2 or N2-5%NH3) and gas flow rate (46.5, 93, 120 and 240 cm3/min) on phase percentage and deposition rate of Si3N4 and Si2N2O was investigated. Analysis of variance shows that the parameter that most significantly impacts the total amount of deposited
phase is the processing temperature, followed by processing time and nitrogen precursor. Regardless of the nitrogen precursor,
at 1300 °C, Si3N4 and Si2N2O depositions follow an S-like and parabolic behavior, respectively. The incubation period shown by Si3N4 in N2-5%NH3 is associated to a decrease in the O2 partial pressure during Si2N2O formation while the rapid increase at long processing times is attributed to the enhanced effect of hydrogen.
PACS 81.15.Gh; 81.05.Je; 81.15.-z; 81.05.Rm; 47.85.L- 相似文献
8.
Yttrium oxide thin films are deposited by microwave electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapour deposition process using an indegeneously developed Y(thd)3 {(2,2,6,6-tetramethyl-3,5-heptanedionate)yttrium} precursor. Depositions were carried out at two different argon gas flow rates keeping precursor and oxygen gas flow rate constant. The deposited coatings are characterized by X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GIXRD) and infrared spectroscopy. Optical properties of the films are studied by spectroscopic ellipsometry. Hardness and elastic modulus of the films are measured by load depth sensing nanoindentation technique. Stability of the film and its adhesion with the substrate is inferred from the nanoscratch test.It is shown here that, the change in the argon gas flow rates changes the ionization of the gas in the microwave ECR plasma and imposes a drastic change in the characteristics like composition, structure as well as mechanical properties of the deposited film. 相似文献
9.
Anchuan Wang John A. Belot Tobin J. Marks Paul R. Markworth Robert P. H. Chang Michael P. Chudzik Carl R. Kannewurf 《Physica C: Superconductivity and its Applications》1999,320(3-4):154-160
Smooth, epitaxial cerium dioxide thin films have been grown in-situ in the 450–650°C temperature range on (001) yttria-stabilized zirconia (YSZ) substrates by metal–organic chemical vapor deposition (MOCVD) using a new fluorine-free liquid Ce precursor. As assessed by X-ray diffraction, transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM), the epitaxial films exhibit a columnar microstructure with atomically abrupt film-substrate interfaces and with only minor bending of the crystal plane parallel to the substrate surface near the interface and at the column boundaries. With fixed precursor temperature and gas flow rate, the CeO2 growth rate decreases from 10 Å/min at 450°C to 6.5 Å/min at 540°C. The root-mean-square roughness of the films also decreases from 15.5 Å at 450°C to 4.3 Å at 540°C. High-quality, epitaxial YBa2C3O7−x films have been successfully deposited on these MOCVD-derived CeO2 films grown at temperatures as low as 540°C. They exhibit Tc=86.5 K and Jc=1.08×106 A/cm2 at 77.4 K. 相似文献
10.
The Eu2+and Dy3+ activated Sr3Al2O6 (S3A2O-ED) nanophosphors were synthesized by a new microwave method. The S3A2O-ED sample calcined in microwave oven at around 650 °C for 20 min possesses a cubic Sr3Al2O6 single phase. The sample showed small size (80–100 nm) and spherical shape. The excitation and emission spectra indicated that excitation broad band chiefly sited in visible range and the nanophosphors emitted strong light at 611 nm under around 473 nm excitation. Comparing with conventional method, the microwave synthesis of S3A2O-ED greatly decreased the calcining temperature and time. However, the brightness of S3A2O-ED nanophosphors was reduced. The change of luminescent intensity in S3A2O-ED nanophosphors could be attributed to the effect of surface energy. 相似文献
11.
Hui Lin Shengming Zhou Hao Teng Xiaorui Hou Tingting Jia Shulin Gu Shunming Zhu Zili Xie Ping Han Rong Zhang Ke Xu 《Applied Surface Science》2009,255(22):9146-9148
m-plane ZnO film was epitaxially deposited on (1 0 0) γ-LiAlO2 by metal-organic chemical vapor deposition at 600 °C with a GaN buffer layer. The epitaxial relationships between ZnO and GaN, GaN and (1 0 0) γ-LiAlO2 were determined by X-ray diffraction Φ-scans. There exhibits very small decrease for the E2 mode shift (0.3 cm−1) of ZnO in the Raman spectrum, which indicates the epitaxial ZnO film was under a slight tensile stress (5.77 × 107 Pa). Unlike the highly strained a-plane ZnO, temperature dependent photoluminescence spectra show that the free A exiton emission was observed with the temperature ≤138 K. 相似文献