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1.
《Diamond and Related Materials》2003,12(10-11):1675-1680
A new multi-layered structure of heteroepitaxial (1 0 0) and (1 1 1) Ir grown on CaF2-buffered (0 0 1) and (1 1 1) Si wafers by UHV electron-beam evaporation was prepared for the deposition of diamond films. A two-step process of bias-enhanced nucleation and a subsequent growth by controlling the α growth parameter was performed to deposit (0 0 1) and (1 1 1) diamond films by chemical vapor deposition, respectively. Scratching or seeding by fine diamond powders was also attempted on the (1 1 1) substrates to enhance the diamond nucleation density. Raman spectroscopy, X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy were used to characterize the Ir/CaF2/Si substrates as well as the diamond films grown on top of iridium layer. Heteroepitaxial relationship between the deposited diamond grains and (0 0 1) substrates has been observed.  相似文献   

2.
The present study provides a multi-scale investigation of the crystalline quality and the structural defects present in heteroepitaxial diamond films grown on iridium/SrTiO3 (001) substrates by microwave plasma assisted chemical vapor deposition. X-ray diffraction, Raman spectroscopy and low temperature cathodoluminescence are combined to accurately characterize the mosaicity, the density of dislocations and the residual strain within the films. X-ray diffraction and Raman results confirm a structural quality at the state-of-the-art according to the epitaxial relationship 〈100〉diamond(001) // 〈100〉iridium(001) // 〈100〉SrTiO3 (001). In addition, Raman and cathodoluminescence observations on cross-sections reveal the presence of local strain.  相似文献   

3.
A novel nucleation technique based on electron cyclotron resonance microwave plasma was developed to enhance the nucleation of diamond. By choosing a suitable experimental condition, a nucleation density higher than 108 nuclei cm−2 was achieved on an untreated, mirror-polished silicon substrate. Uniform diamond films were obtained by combining this nucleation method with subsequent growth by the common microwave plasma chemical vapor deposition. Furthermore, the possibility of this new nucleation method to generate heteroepitaxial diamond nuclei on (001) silicon substrates was explored.  相似文献   

4.
Diamond/Ir/YSZ/Si(001) is currently the most promising multilayer structure for the future realisation of large-area diamond single crystals. A decisive key is the preparation of the iridium layers on silicon. It is shown in this work that high quality iridium films with mosaic spread below 0.2° can be grown on oxide buffer layers with a mosaic spread higher than 1°. An averaging process during the coalescence of the iridium islands provides a plausible mechanism for this phenomenon. The oxide buffer and the iridium overlayers can be grown homogeneously on 4-inch wafers in a similar quality as for 1 × 1 cm2 samples. Bias enhanced nucleation followed by 40 h growth on the large-area Ir/YSZ/Si(001) wafers yields diamond films with a mosaicity of 0.16° (tilt) and 0.34° (twist). For a further increase of the area of heteroepitaxial diamond nucleation the homogeneity of the plasma discharge has to be improved.  相似文献   

5.
Initial growth of heteroepitaxial diamond on Ir (0 0 1)/MgO (0 0 1) was investigated by scanning electron microscopy, reflection high-energy electron diffraction (RHEED) and atomic force microscopy. Bias-enhanced nucleation (BEN) was performed by antenna-edge-type microwave plasma assisted chemical vapor deposition. In BEN, diamond crystallites nucleated and grew along the [−1 1 0] and [1 1 0] directions of iridium. Diamond was likely to nucleate on protruded iridium areas. After BEN, in addition to the diamond diffraction spots, iridium bulk diffraction spots, which were not observed before BEN, were observed by RHEED. The iridium surface appeared to be protruded and changed by the high ion current density in BEN. Under [0 0 1] selective growth conditions, diamond crystallites, which were less than 10 nm in diameter, were etched by H2 plasma. Diamond nucleated areas corresponded to the surface ridges of iridium along the [−1 1 0] and [1 1 0] directions at 10–40 nm intervals before BEN.  相似文献   

6.
《Ceramics International》2016,42(8):9981-9987
Epitaxial (100) and (111) SrTiO3 films were prepared on (100) and (111) MgO single-crystal substrates, respectively, using laser chemical vapor deposition. The effect of deposition temperature (Tdep) on the orientation and microstructure of the SrTiO3 films was investigated. On the (100) MgO substrates, SrTiO3 films showed a (111) orientation at a low Tdep of 1023 K. (100) SrTiO3 films, which were epitaxially grown at Tdep=1123–1203 K, had dense cross sections and flat surfaces with rectangular-shaped terraces. On the (111) MgO substrates, (111) SrTiO3 films were epitaxially grown at Tdep=983–1063 K; however, these films' orientations became random at high Tdep of 1063–1113 K. The (111) SrTiO3 films consisted of columnar grains with triangular pyramidal caps. The deposition rates of the epitaxial (100) and (111) SrTiO3 films were 13–25 and 18–32 μm h−1, respectively, which is 5–530 times higher than those obtained by MOCVD.  相似文献   

7.
The oxygen incorporation at the interface between the silicon substrate and chemical vapour deposited (CVD) diamond films nucleated by the bias-enhanced nucleation (BEN) procedure has been studied by heavy-ion elastic recoil detection (ERD). Using standard process conditions for the realisation of heteroepitaxial films, oxygen with a concentration equivalent to about 1 nm SiO2 has been found, which was mainly incorporated during textured growth with a certain CO2 admixture to the process gas. By completely omitting CO2 during nucleation and growth, the oxygen at the interface can be reduced by nearly one order of magnitude to 6.3×1015 at cm−2, corresponding to 0.14 nm SiO2. Intentional addition of highly enriched C18O2 to the gas phase shows that the oxygen incorporation is strongly enhanced during BEN with hydrocarbon in the gas phase. The results indicate that roughening of the surface, the deposition of SixOyCz phases and strong lateral inhomogeneities at the silicon interface may explain the coexistence of epitaxial crystallites and amorphous phases. It is suggested that a further reduction of the oxygen concentration at the interface may have consequences for an improved heteroepitaxy of diamond on silicon.  相似文献   

8.
Diamond films have been grown on carbon steel substrates by hot-filament chemical vapour deposition methods. A Co-containing tungsten-carbide (WC–Co) coating prepared by high velocity oxy-fuel spraying was used as an intermediate layer on the steel substrates to minimize the early formation of graphite (and thus growth of low quality diamond films) and to enhance the diamond film adhesion. The effects of the WC–Co interlayer on nucleation, quality, adhesion, tribological behaviour and electrochemical corrosion of the diamond film were investigated. The diamond films exhibit excellent adhesion under Rockwell indentation testing (1500 N load) and when subjected to high-speed, high-load, long-time reciprocating dry sliding ball-on-flat wear tests against a Si3N4 counterface in ambient air (500 rpm, 200 N, 300,000 cycles). A WC–Co interlayer with appropriate chemical pretreatment is shown to play an important role in improving the nucleation, quality and adhesion of the diamond film, relative to that shown by substrates without such pretreatment.  相似文献   

9.
Growth of Bi2Ti2O7 films on the substrates having cubic-structure was investigated by metal organic chemical vapor deposition (MOCVD). (1 0 0), (1 1 0) and (1 1 1)SrTiO3 single crystals, (1 1 1)-oriented Pt- and SrRuO3-coated (1 1 1)SrTiO3 were used as substrates together with (1 1 1)Pt/TiO2/SiO2/Si. Peaks originated to Bi2Ti2O7 phase were not detected on (1 0 0), (1 1 0) and (1 1 1)SrTiO3 substrates. On the other hand, (1 1 1)-oriented Bi2Ti2O7 phase was ascertained to be prepared on (1 1 1)Pt//(1 1 1)SrTiO3 and (1 1 1)Pt/TiO2/SiO2/Si substrates in spite of the almost the same lattice parameters of SrRuO3 and SrTiO3 with Pt. From the pole figure measurement, Bi2Ti2O7 films prepared on the (1 1 1)Pt//(1 1 1)SrTiO3 substrates were ascertained epitaxial grown, (1 1 1)Bi2Ti2O7//(1 1 1)Pt//(1 1 1)SrTiO3, while that on the (1 1 1)Pt/TiO2/SiO2/Si were (1 1 1)-one-axis-oriented Bi2Ti2O7 with in-plain random. The easy growth of (1 1 1)-oriented Bi2Ti2O7 film on (1 1 1)Pt layer can be explain by the existence of the sub-unit in (1 1 1)Pt plane consist of three Pt atoms.  相似文献   

10.
A modified nucleation and growth process was adopted so as to improve the electron field emission (EFE) properties of diamonds films. In this process, a thin layer of ultra-nanocrystalline diamonds (UNCD), instead of bias-enhanced-nuclei, were used as nucleation layer for growing diamond films in H2-plasma. The morphology of the grains changes profoundly due to such a modified CVD process. The geometry of the grains transform from faceted to roundish and the surface of grains changes from clear to spotty. The Raman spectroscopies and SEM micrographs imply that such a modified diamond films consist of UNCD clusters (~ 10–20 nm in size) on top of sp3-bonded diamond grains (~ 100 nm in size). Increasing the total pressure in CVD chamber deteriorated the Raman structure and hence degraded the EFE properties of the films, whereas either increasing the methane content in the H2-based plasma or prolonged the growth time improved markedly the Raman structure and thereafter enhanced the EFE properties of diamond films. The EFE properties for the modified diamond films can be turned on at E0 = 11.1 V/μm, achieving EFE current density as large as (Je) = 0.7 mA/cm2 at 25 V/μm applied field.  相似文献   

11.
It is generally accepted that SiC layers are often involved in the adhesion efficiency of chemical vapour deposition (CVD) diamond films on Si-containing substrates. Si3N4–SiC composite substrates with different amounts of SiC particles (0–50 wt%) were then used for diamond deposition. Samples were produced by pressureless sintering (1750°C, N2 atmosphere, 2–4 h). The diamond films were grown on a commercial MPCVD reactor using H2/CH4 mixtures. Despite there being no special substrate pre-treatment, the films were densely nucleated when SiC was added (Nd≈1×1010 cm−2) with primary nanosized (∼100 nm) particles, followed by a less dense (Nd≈1×106 cm−2) secondary nucleation. Indentation experiments with a Brale tip of up to 588 N applied load corroborated the benefit of SiC inclusion for a strong adhesion. The low thermal expansion coefficient mismatch between Si3N4 and diamond resulted in very low compressive stresses in the film, as proved by micro-Raman spectroscopy.  相似文献   

12.
Silicon has been the most widely studied substrate for the nucleation and growth of CVD diamond films. However, other substrates are of interest, and in this paper, we present the results of a study of the biased nucleation and growth of diamond films on bulk single and polycrystalline tungsten. Diamond films were nucleated and grown, using a range of bias and reactor conditions, and characterized by Raman spectroscopy and scanning electron microscopy (SEM). High-quality (100) textured films (Raman FWHM<4 cm−1) could be grown on both single and polycrystalline forms of the tungsten substrate. On carefully prepared substrates, by varying the bias treatment, it was possible to determine the nucleation density over a 4–5 order range, up to ∼109 cm−2. Raman measurements indicated that the diamond films grown on bulk tungsten exhibited considerable thermal stress (∼1.1 GPa), which, together with a thin carbide layer, resulted in film delamination on cooling. The results of the study show that nucleation and growth conditions can be used to control the grain size, nucleation density, morphology and quality of CVD diamond films grown on tungsten.  相似文献   

13.
Some novel aspects of nanocrystalline diamond (NCD) film nucleation and growth by DC-PACVD were investigated, which focused on the effect of methane injection timing at ramp stage (see discussion in the text) and cathode temperature as well. NCD films were deposited for 4 h on a 4 in. Si wafer which was ultrasonically seeded in a methanol slurry of diamond powder with a 5 nm average diameter. The H2/CH4/N2 gas mixture with a composition of 96.7%/3%/0.3% was used as precursor gas. The total gas flow rate and chamber pressure were 150 sccm and 150 Torr, respectively. Discharge voltage and current of 500 V and 45 A were used respectively at a substrate temperature of 800 °C. The nucleation density, microstructure, growth rate and crystallinity of the obtained NCD films were characterized by SEM, XRD, NEXAFS and Raman spectroscopy. The nucleation density was found to be sensitive to methane injection timing in the ramp stage. In addition, the cathode temperature greatly affected the nucleation density, grain size and growth rate.  相似文献   

14.
Diamond film on titanium substrate has become extremely attractive because of the combined properties of these two unique materials. Diamond film can effectively improve the properties of Ti for applications as aerospace and biomedical materials, as well as electrodes. This study focuses on the effects of process parameters, including gas composition, substrate temperature, gas flow rate and reactor pressure on diamond growth on Ti substrates using the hot-filament chemical vapor deposition (HFCVD) method. The nucleation density, nuclei size as well as the diamond purity and growth tendency indices were used to quantify these effects. The crystal morphology of the material was examined with scanning electron microscopy (SEM). Micro-Raman spectroscopy provided information on the quality of the diamond films. The growth tendency of TiC and diamond film was determined by X-ray diffraction analysis. The optimal conditions were found to be: CH4:H2 = 1%, gas flow rate = 300 sccm, substrate temperature Tsub = 750 °C, reaction pressure = 40 mbar. Under these conditions, high-quality diamond film was deposited on Ti with a growth rate of 0.4 μm/h and sp2 carbon impurity content of 1.6%.  相似文献   

15.
High-quality polycrystalline diamond film has been extremely attractive to many researchers, since the maximum transition frequency (fT) and the maximum frequency of oscillation (fmax) of polycrystalline diamond electronic devices are comparable to those of single crystalline diamond devices. Besides large deposition area, DC arc jet CVD diamond films with high deposition rate and high quality are one choice for electronic device industrialization. Four inch free-standing diamond films were obtained by DC arc jet CVD using gas recycling mode with deposition rate of 14 μm/h. After treatment in hydrogen plasma under the same conditions for both the nucleation and growth sides, the conductivity difference between them was analyzed and clarified by characterizing the grain size, surface profile, crystalline quality and impurity content. The roughness of growth surface with the grain size about 400 nm increased from 0.869 nm to 8.406 nm after hydrogen plasma etching. As for the nucleation surface, the grain size was about 100 nm and the roughness increased from 0.31 nm to 3.739 nm. The XPS results showed that H-termination had been formed and energy band bent upwards. The nucleation and growth surfaces displayed the same magnitude of square resistance (Rs). The mobility and the sheet carrier concentration of the nucleation surface were 0.898 cm/V s and 1013/cm2 order of magnitude, respectively; while for growth surface, they were 20.2 cm/V s and 9.97 × 1011/cm2, respectively. The small grain size and much non-diamond carbon at grain boundary resulted in lower carrier mobility on the nucleation surface. The high concentration of impurity nitrogen may explain the low sheet carrier concentration on the growth surface. The maximum drain current density and the maximum transconductance (gm) for MESFET with gate length LG of 2 μm on H-terminated diamond growth surface was 22.5 mA/mm and 4 mS/mm, respectively. The device performance can be further improved by using diamond films with larger grains and optimizing device fabrication techniques.  相似文献   

16.
Results are presented concerning different mechanical pretreatments performed on silicon nitride substrates and their influence on the nucleation and growth of nanocrystalline diamond (NCD). All substrates were equally sintered and finished, but differently pretreated. Then, they were diamond coated in a microwave chemical vapor deposition system (MPCVD) for relatively short periods, using Ar/H2/CH4 gas mixtures. The main objective was to identify the best pretreatment among those proposed, while verifying how it correlates with film uniformity and surface roughness after post-growth. The effect of a molybdenum mask during growth is investigated.The top surface analysis revealed major differences in the nucleation morphology of diamond nuclei on the pretreated samples, two different nucleation types having been identified. For all pretreatments, samples exhibited a very smooth and uniform underlayer of very fine grain particles before the formation of larger aggregates, suggesting a bi-phase nucleation mechanism. When no mask is used considerable changes in the nucleation concentration are found, the resulting films showing grain enlargement near the edges, where the morphology assumes microcrystalline nature. This effect is suppressed by the use of a mask that allowed obtaining very uniform smooth films (Rrms 30 nm, thickness ∼ 1.3 μm, MUS pretreatment), indicating a strong edge effect for the unmasked case. This fact can be attributed both to increased local temperature, plasma density and gas turbulence.  相似文献   

17.
Ordered graphene films have been fabricated on Fe-treated SiC and diamond surfaces using the catalytic conversion of sp3 to sp2 carbon. In comparison with the bare SiC (0 0 0 1) surface, the graphitization temperature is reduced from over 1000 °C to 600 °C and for diamond (1 1 1), this new approach enables epitaxial graphene to be grown on this surface for the first time. For both substrates, a key development is the in situ monitoring of the entire fabrication process using real-time electron spectroscopy that provides the necessary precision for the production of films of controlled thickness. The quality of the graphene/graphite layers has been verified using angle-resolved photoelectron spectroscopy, scanning tunneling microscopy and low energy electron diffraction. Graphene is only formed on treated regions of the surface and so this offers a method for fabricating and patterning graphene structures on SiC and diamond in the solid-state at industrially realistic temperatures.  相似文献   

18.
Multiferroic BiFeO3 films have been deposited on a number of substrates by RF magnetron sputtering. Two routes were adopted in order to obtain the films of high phase purity and accurate stoichiometry. The first was to sputter films at room temperature and then the BiFeO3 phase was formed after sintering at various temperatures under controlled ambient atmosphere. The second was to grow BiFeO3 in-situ at high temperature during sputtering. Although the sintered films grown on SrTiO3 substrates were epitaxial and showed better texture than the in-situ films, they had much poorer ferroelectric properties, due to the residual traces of intermediate phases formed during heating. Under right growth parameters, the in-situ films grown on the LaNiO3?x buffered SrTiO3 showed fully saturated ferroelectric hysteresis loops with large remanent polarisation of 64 μC/cm2. Piezoresponse force microscopy (PFM) was used to examine the ferroelectric domain structures. When scanned without DC bias, fine spontaneous domains were observed. Under ±10 V DC bias, PFM confirmed that the domains could be poled and switched.  相似文献   

19.
The thermal diffusivity of heteroepitaxial CVD diamond films grown on iridium buffer layers has been measured using a combined laser flash and converging thermal wave setup. Absolute values and anisotropy for a fiber-textured reference sample were in the range of former reports in the literature. The in-plane thermal conductivity for three heteroepitaxial samples grown on Ir/YSZ/Si(001) as deduced from the diffusivity measurements was around 20 W/cm K, similar to high purity large grain polycrystalline films. Laser flash measurements of the perpendicular diffusivity suggest that the defect rich first microns of the heteroepitaxial films represent a thermal series resistance which limits the perpendicular heat transport especially for thin films. For the parallel component of the diffusivity the contribution of this shunt resistance is negligible. The absolute values for the parallel component in the heteroepitaxial films with in-plane angular spread of the crystal lattice below 0.5° were discussed in the framework of the model proposed by Klemens for phonon scattering by grain boundaries. The present data indicate that the remaining defects in heteroepitaxial diamond films with low mosaic spread are significantly less detrimental for the heat transport than large angle grain boundaries. In addition we speculate that the exclusive deposition on the {100} growth sector may also reduce the influence of nitrogen in the gas phase on the heat transport properties.  相似文献   

20.
Iridium films on SrTiO3(001) have recently proven to be a superior substrate material for the heteroepitaxy of diamond thin films by chemical vapour deposition in the effort towards the realization of single crystal diamond films. In this paper we report on the growth and structural properties of iridium (Ir) films deposited by electron-beam evaporation on SrTiO3(001) surfaces varying the deposition temperature between 280 and 950°C. The films were studied by scanning electron microscopy, atomic force microscopy and X-ray diffraction. At the highest temperature film growth proceeds via three-dimensional nucleation, coalescence and subsequent layer-by-layer growth. The resulting films show a cube-on-cube orientation relationship with the substrate and a minimum mosaic spread of 0.15°. Towards lower deposition temperatures the orientation spread increases only slightly down to ∼500°C while the surface roughness, after passing through a maximum at ∼860°C, decreases significantly. For the lowest temperatures (below 500°C) the mosaic spread rises accompanied by the occurrence of twins until the epitaxial order is lost. Plasma treatment in the diamond deposition reactor at high temperature (920°C) yields low nucleation densities and modifies the Ir surface. At the same time {111} facets show a significantly higher structural stability as compared with {001} facets. Nucleation at 700°C results in highly aligned diamond grains with low mosaic spread and a vanishing fraction of randomly oriented grains, proving the superior properties of Ir films on SrTiO3 for diamond nucleation as compared with pure silicon substrates.  相似文献   

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