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The optimization of the doping level of boron, silicon and nitrogen doped diamond film on Co-cemented tungsten carbide inserts
Accepted Manuscript The optimization of the doping level of boron, silicon and nitrogen doped diamond film on Co-cemented tungsten carbide inserts
Liang Wang, Jinfei Liu, Tang Tang, Nan Xie, Fanghong Sun PII:
S0921-4526(18)30591-X
DOI:
10.1016/j.physb.2018.09.018
Reference:
PHYSB 311058
To appear in:
Physica B: Physics of Condensed Matter
Received Date:
24 July 2018
Accepted Date:
10 September 2018
Please cite this article as: Liang Wang, Jinfei Liu, Tang Tang, Nan Xie, Fanghong Sun, The optimization of the doping level of boron, silicon and nitrogen doped diamond film on Co-cemented tungsten carbide inserts, Physica B: Physics of Condensed Matter (2018), doi: 10.1016/j.physb. 2018.09.018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT The optimization of the doping level of boron, silicon and nitrogen doped diamond film on Co-cemented tungsten carbide inserts Liang Wang1*, Jinfei Liu1, Tang Tang1, Nan Xie1, Fanghong Sun2 1School
2School
of Mechanical Engineering, Tongji University, Shanghai, 201804, P.R. China
of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P.R. China
Abstract Boron doped, silicon doped and nitrogen doped diamond films with different doping level in gas phase are deposited on Co-cemented tungsten carbide (WC-Co) inserts using hot filament chemical vapor deposition (HFCVD) method. Trimethyl borate ((CH3O)3B), tetraethoxysilane (Si(OC2H5)4) and urea (CO(NH2)2) are dissolved in acetone to server as boron, silicon and nitrogen precursors, respectively. The as-deposited diamond films are characterized by field emission scanning electron microscope (FESEM), Raman spectroscopy and indentation tests. The results suggested that doping source and doping level will affect the surface morphology, growth rate, quality and adhesion of diamond film. The optimized doping level to obtain diamond films deposited on WC-Co substrate for mechanical applications with well faceted crystal, low defect, low cluster structure and high adhesive strength is 5000 ppm, 10000 ppm and 10000 ppm for boron, silicon and nitrogen doping, respectively. Keywords: boron; silicon; nitrogen; doping level; doped diamond film; WC-Co. 1. Introduction The performances of the diamond films prepared by chemical vapor deposition (CVD) is attractive as ideal tool, die, mechanical bearing and seal coatings for its excellent characteristic, such as high hardness and wear resistance, good thermal conductivity and low friction and thermal coefficient[1, 2]. In order to broaden the application filed of diamond film, the performance of diamond films can be tailored by adjusting the growth condition. Doping is an important way to apply diamond film to the field of semiconductor. Doping level is one of the important parameters of doped diamond film, it has significant influence on the electrical properties of diamond films[3]. But at present, in order to apply the doped diamond to the field of electrics or electrochemistry, researches are mainly focus on the properties of doped diamond films deposited on the substrates like silicon, niobium or tantalum[4, 5]. In addition, it is reported that doping also has certain effects on the growth behavior, tribological behavior of diamond films [6-8]. To our knowledge, the properties of the doped diamond films on the Co-cemented carbide (WC-Co) have still not been studied systematically so far. It is well known that WC1 / 18
ACCEPTED MANUSCRIPT Co is comparative stable under CVD processing conditions and is widely used as the cutting tool, riveting tool or die materials[9-12]. The surface morphology, structure and quality of the diamond film will affect the tribological or cutting performance of diamond coated dies or tools. Thus, doping will affects the application properties of diamond film in mechanical fields. In this study, we focus on the effects of doping level on the morphology, quality, growth rate, quality and adhesion rather than the electricity of diamond films on WC-Co substrates. In order to meet the need of different mechanical application, three different types of doped diamond films, namely boron, silicon and nitrogen doped diamond films with different doping level are systematically studied. 2. Experiments details The boron doped (B-doped), silicon doped (Si-doped) and nitrogen doped (N-doped) diamond films are deposited using a bias-enhanced hot filament CVD (HFCVD) apparatus. Flat square shaped WC-6%Co inserts are used as substrate. For comparison, undoped diamond films are also deposited using the same deposition parameters. To coarse the surface and remove the surface Co element, as-received inserts are firstly submitted to react with Murakami’s reagent and Caro’s acid, and then abraded with diamond powder[13]. Acetone and hydrogen are adopted as reactive gases. Trimethyl borate (CH3(3)BO3), tetraethoxysilane (C8H20O4Si) and urea (NH2CONH2) is dissolved in acetone with preset B/C, Si/C and N/C atomic ratio (1000 ppm, 5000 ppm, 10000ppm and 20000 ppm) to serve as boron, silicon and nitrogen precursors. The mixed solution in the liquid container is introduced in the reactor by part of H2 and the flow rate of mixed solution is controlled by the flow rate of carrier gas and the vapor pressure of mixed solution. The vapor pressure of mixed solution is associated with its temperature which is maintained at 0 °C by immersed the container in glacial-aqueous mix solution. The gas phase is activated by 6 electrical heated carburized tantalum wires at intervals of 38 mm, which are 10 mm above the substrate surface. The detailed deposition parameters of the diamond films are listed in table 1. Table 1 The detailed deposition parameters of doped CVD diamond films.
nuclear
growth
100/200
80/200
Chamber Pressure (kPa)
1.6
4
filament temperature (°C)
2200~2300
2200~2300
Substrate temperature (°C)
800~900
800~900
Bias current (A)
4
3
Duration (h)
0.5
5.5
Carrier gas (mL/min)/H2 (mL/min)
For characterization, filed emission scanning electron microscopy (FESEM) is used to 2 / 18
ACCEPTED MANUSCRIPT observe the morphology, microstructure, grain size and film thickness of as-deposited diamond films. As well, Raman spectroscopy is employed to identify the quality and purity of diamond films. Rockwell indentation tests are carried out to qualitatively evaluate the adhesion of the diamond films. 3. Results and discussion 3.1 The effect of doping level on the morphology and growth rate of diamond films
The surface and section morphology of as-deposited diamond films is observed by FESEM, the working voltage is 5 kV, working distance is about 10 to 15 mm and the detector is SE2. The surface morphology and cross-section morphology of undoped diamond films are shown in Fig.1. The conventional undoped diamond films show well faceted polycrystalline morphology, the grain size is about 2-3 μm, the columnar growth structure and film thickness of 3.7 μm can be detected from the cross section morphology.
Fig.1. The surface and cross-section morphology of undoped diamond films.
The surface morphology of B-doped diamond films with different doping level are shown in Fig.2. When the doping level in the gas phases is 1000 and 5000 ppm, B-doped diamond films exhibit a similar morphology with that of undoped ones, except the grain size has little increased to 3-4 μm. However, when the doping level increases to 10000 ppm, the morphology begin to change extensively. Although the diamond can maintain its crystallinity, there are many small diamond grains between the larger grains, and also some disordered materials can be observed. When the doping level further increased to 20000 ppm, the diamond grains seem be etched seriously and pores can be detected on the surface. The reason may be that boron atoms have limit solubility in the diamond lattice, too much boron atoms may cause the distortion of diamond lattice. We can see that B-doped diamond films also present a columnar growth structure from Fig.3 which shows the cross section morphology of B-doped diamond film. However, incontinuity cross section can be detected due to the present of pores as shown in the surface
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ACCEPTED MANUSCRIPT
(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.2. The surface morphology of B-doped diamond films deposited at different doping level.
(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.3. The cross-section morphology of B-doped diamond films deposited at different doping level.
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ACCEPTED MANUSCRIPT morphology under the doping level of 20000 ppm. The film thickness first increases then decreases with the boron doping level. The film thickness is about 4 μm when the doping level is 1000 ppm and increases to 4.7 μm when the doping level increases to 5000 ppm. However, the thickness decreases to 3.5 μm when the doping level increases to 10000 and 20000 ppm. As shown in Fig.4, the surface morphology and grain size of Si-doped diamond films with relative low doping level of 1000 and 5000 ppm is still similar to that of undoped ones. When the doping level increases to 10000 ppm, the surface presents fine grained diamond with the grain size at about 200 nm. When the doping level increases to 20000 ppm, nano-crystalline diamond (NCD) film with typical cauliflower morphology is obtained, the grain size further decreases to less than 100 nm. However, the aggregation of the diamond is quiet obvious, it seems possessing a large fluctuating morphology and showing a rough surface.
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.4. The surface morphology of Si-doped diamond films deposited at different doping level.
The cross-sectional morphology of Si-doped diamond films (Fig.5) shows that the growth structure of Si-doped diamond films is also columnar structure, the film gradually becomes compact and the thickness of the film gradually decreases with the increase of doping level. The film thickness is 3.6, 3.3, 2.6 and 2 μm for the doping level of 1000, 5000, 10000 and 20000 ppm, respectively.
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ACCEPTED MANUSCRIPT
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.5. The cross-section morphology of Si-doped diamond films deposited at different doping level.
Figure 6 shows that well faceted diamond can be obtained when nitrogen doping level is 1000 ppm. As indicated by the dash circle in Fig.6 (a), pentagon pits on the grain indicate the twining of {111} face. It also shows that the diamond growth rate parameter α is greater than 3 under the nitrogen doping level of 1000 ppm, thus {111} is the predominant apparent plane of diamond crystal[14]. The average grain size is smaller than that of undoped ones, it will be further reduced by the increasing of the doping level. The fine grained diamond with cuboctahedron structure appears at the doping level of 20000 ppm, the exposure plane is mainly (111) and (100), the <100> direction of the cuboctahedron is perpendicular to the substrate surface. The cross section morphology of N-doped diamond films is shown in Fig.7. The thickness of the diamond films with nitrogen doping level of 1000 ppm and 5000 ppm is similar to that of undoped diamond films, the values are about 3.8 and 3.6 μm, respectively. The thickness of diamond films decreases with the increase of nitrogen doping level. At the doping level of 10000 ppm, the thickness reduces to about 3 μm. When nitrogen doping level is 20000 ppm, the growth of the film is very slow, and its thickness is only 1μm during the deposition of 6 hours. 3.2 The effect of doping level on the quality of diamond films
The Raman spectra of as-deposited diamond films are excited by He–Ne laser with a
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ACCEPTED MANUSCRIPT
(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C=20000 ppm
Fig.6. The surface morphology of N-doped diamond films deposited at different doping level.
(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C= 20000 ppm
Fig.7. The cross-section morphology of N-doped diamond films deposited at different doping level.
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ACCEPTED MANUSCRIPT
Fig.8. The Raman spectrum of the undoped diamond films.
(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.9. The Raman spectra of B-doped diamond films at different doping level.
wavelength of 632.8 nm at room temperature. The Raman spectrum of undoped diamond film is illustrated in Fig.8. The sharp peak near 1332 cm−1 corresponding to the first order Raman peak of diamond, indicating the great quality of diamond film. The broad peak at about 1070 and 1580 cm−1 can be attributed to the disorder carbon and graphite at the grain boundary of the diamond[12]. Compared with undoped diamond films, the Raman spectra of B-doped diamond film shown in Fig.9 changed obviously when the doping level is only 1000 ppm. The peak at 1332 cm−1 become asymmetric and an obvious broad peak at about 1200 cm−1 can be 8 / 18
ACCEPTED MANUSCRIPT detected. These two features reveal the metallic of the diamond that is to say the diamond can conduct electric after boron doping [15]. The results also indicate that the boron atom may enter the diamond lattice and have a relative high doping efficiency. The intensity of the peak at 1332 cm−1 decreases as the increase of the doping level. When the doping level increases to 20000 ppm, the diamond peak totally disappears, and shows a more broaden Raman peak. Moreover, the graphite peak at 1580 cm−1 can be obviously detected. The results indicate that the diamond begin to graphitization and the quality has obviously decreased as excessive boron atoms are introduced in the gas phases. As noticed in Fig.10, the Raman spectra are similar to that of undoped ones when the silicon doping level is 1000 ppm and 5000 ppm. The sharp peak near 1332 cm−1 indicated that the film is mainly composed of diamond phases. When the atom ratio Si/C in the gas phases is 20000 ppm, the peak at about 1332 cm−1 becomes broaden, it indicated the decreasing of the quality of diamond film[16].
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.10. The Raman spectra of Si-doped diamond films at different doping level.
As shown in Fig.11, the Raman spectra of N-doped diamond films with the doping level of 1000 ppm are similar to that of undoped diamond films. The results reveal that the nitrogen dopant have little influence on the diamond quality under relative low doping level. It also shows that the nitrogen doping efficiency may lower than that of boron doping. However, the 9 / 18
ACCEPTED MANUSCRIPT non-diamond phases decrease when the doping level increase to 5000 ppm, the broad peak at approximately 1220 cm−1 could be attributed the disordered sp3 carbon structure in the diamond film. When the doping level comes to 10000 ppm，the Raman spectra of N-doped diamond films only show distinct diamond peak near 1332 cm−1, indicating a relative high diamond quality. However, the content of graphite phases increases when the doping level increases to 20000 ppm. The graphite phases can be characterized by the broad peak at about 1580 cm−1. The results may be attributed to that the large doping level in the gas phases will produces more CN or HCN radicals, these radical will induce severe H abstract, and thus cause more dangling bonds on the diamond surface. Consequently, the surface can be reconstructed to form graphite phases.
(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C=20000 ppm
Fig.11. The Raman spectra of N-doped diamond films at different doping level.
3.3 The effect of doping level on the adhesion of diamond films
The adhesion between diamond films and WC-Co substrates is qualitatively measured by Rockwell hardness tester with a diamond indenter (angle =120°, radius =0.2 mm). The indentation FESEM morphology of the undoped diamond film under the load of 100 kgf is shown in Fig.12. A large area of the diamond film peels off on one side of the force point. The maximum radius of the indentation imprint is about 264 μm. 10 / 18
ACCEPTED MANUSCRIPT
Fig.12. The indentation imprint of undoped diamond films.
The indentation morphology of B-doped diamond films at different doping level is shown in Fig.13. It can be seen that when relatively low content of boron atom is introduced in the gas phases, the peeling off of the diamond film also occurs on one side of the force point while the maximum radius of the imprint decreases slightly to 211 μm. When the doping level is 5000 ppm, the shape of the indentation imprint is round. The peeling and cracking of the diamond film are not found except the fracture of a small amount of diamond film on the edge of the imprint. The maximum radius of the indentation imprint is 161 μm. It indicated that the adhesive strength is relatively high at the doping level of 5000 ppm. When the boron doping level further increased to 10000 ppm, the film peeling off on the side of the force point occurs again, the maximum radius of indentation imprint is 207 μm. When boron doping level increases to 20000 ppm, a large area of the film peels off and exposes the WC substrate, the maximum radius of the indentation imprint reaches to 307 μm. This is due to the increasing of the non-diamond phase in the film when the boron in the gas phases is too high. The incorporation of the excessive boron atom will induces a larger lattice distortion and defects, resulting in a larger internal stress of the film, thus lower the adhesion strength between the film and substrate. The adhesion of the diamond film is poor at the low silicon doping level as indicated in Fig.14. It shows large area of diamond film peels off near the force point. The diamond films show round indentation imprint when the doping level increases to 10000 ppm, only short radiated cracking rather than peeling off of the diamond film can be seen. When the doping level further increases to 20000 ppm, the adhesive strength between diamond film and the substrate will be further enhanced as there are no cracks near the indentation. However, it can be seen that the surface of the diamond film has a large number of small particles and the surface is not smooth, which is due to the diamond clusters mentioned above. The maximum indentation imprint radius of Si-doped diamond films at 1000 ppm, 5000 ppm, 10000 ppm and 20000 ppm is 357, 325, 164 and 193 μm, respectively.
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ACCEPTED MANUSCRIPT
(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.13. The indentation imprint of B-doped diamond films at different doping level.
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.14. The indentation imprint of Si-doped diamond films at different doping level.
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ACCEPTED MANUSCRIPT It can be seen from the indentation morphology of the N-doped diamond film in Fig.15 that the expansion range of the peeling off of the diamond film is far away from the indentation center at the low nitrogen doping level. The result indicates that the adhesion of the film and substrate is not high. With the increasing of nitrogen doping level, the adhesion has been improved. At the doping level of 10000 ppm and 20000 ppm, there are no large area of crack and film peeling off after the indentation test. Only a small amount of the delamination of film appears. It is possible that the growth rate of diamond is slow with the increasing of the nitrogen doping level, which relieves the competitive growth between diamond grains and reduces the internal stress, and thus help to improve the adhesion. Even though, the adhesion is weaker compared with that of diamond films under the condition of B/C=5000 ppm, Si/C=10000 and Si/C=20000 ppm. The maximum indentation imprint radius of N-doped diamond films at 1000 ppm, 5000 ppm, 10000 ppm and 20000 ppm is 296, 311, 225 and 193 μm, respectively.
(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C=20000 ppm
Fig.15. The indentation imprint of N-doped diamond films at different doping level.
From the indentation results, we found that diamond films with high adhesion can be obtained by using suitable doping level of boron or silicon. To reveal the mechanism of the adhesion improving, the composition of the interface of the diamond and the substrate is first evaluated by using energy dispersive spectroscopy (EDS). As shown in Fig.16, one silicon peak can be detected in the spectrum of Si-doped diamond film. The doped elements cannot be detected in other type of doped diamond films. Si-doped diamond films may formed a silicon containing compound in the interface which may beneficial to obstruct the diffusion of cobalt 13 / 18
ACCEPTED MANUSCRIPT elements into the diamond film during the deposition, thus improving the adhesion of the diamond films.
Undoped
B-doped
Si-doped
N-doped
Fig.16. EDS analysis on the interface of the diamond films and WC-Co substrate.
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ACCEPTED MANUSCRIPT The indentation results also reveal that B-doped diamond films present high adhesion while we cannot detect boron peaks from the EDS analysis. This may be due to the fact that boron is a light element, so the boron peak will overlaps with the carbon peak. Thus, the X-ray diffraction (XRD) is used to further reveal the mechanism of the adhesion improvement by boron doping. Fig.17 presents the XRD patterns of the WC-Co sample after nucleation for 15 min under the condition of undoped and boron doping of 5000 ppm in the gas phases. The results indicate that a weak diffraction peak at about 2θ of 44° can be detected in the boron doped diamond film. The peak can be corresponded to the diffraction peak of CoWB, which indicates that CoWB is formed during the deposition of the diamond films after boron doping. The stable B-Co compound formed in the process of CVD will reduce the catalytic action of cobalt element in the substrate, thus improving the adhesion of the film[17].
(a) undoped diamond films
(b) B-doped diamond films Fig.17. The XRD pattens of undoped diamond films and B-doped diamond films deposited at the doping level of 5000 ppm after nuclear of 15 min.
4. Conclusions In this study, undoped diamond film and boron, silicon and nitrogen doped diamond films with different doping level are deposited on WC-6%Co inserts using HFCVD method. The characterization results of the as deposited diamond film are summarized in table 2. From the results, we can find that doping with boron, silicon or nitrogen will affect the morphology, 15 / 18
ACCEPTED MANUSCRIPT growth rate, quality and adhesion of the HFCVD diamond film on WC-Co substrate. To obtain CVD diamond films with well faceted crystal, better surface quality, moderate growth rate and high adhesion, the relative optimal doping level for different types of doped diamond films is as follows: 5000 ppm for boron doping, 10000 ppm for silicon doping and 10000 ppm for nitrogen doping. Furthermore, we also can get the conclusion that: a) We can using boron doping to improve the growth rate of micro crystalline diamond (MCD) films. b) The silicon doping can be used to refine the diamond grain. c) The diamond quality can be improved by nitrogen doping. d) To improve the adhesion of diamond films on WC-Co substrate, we can utilize boron doping or silicon doping. Table 2 The characterization results of doped HFCVD diamond films on WC-Co substrate. Doping level Undoped
B-doped
Morphology
Grain
Growth
size
rate
Quality
ISmprint radius
0
Well faceted MCD
→
0.62→
→
264→
1000
Well faceted MCD
↑
0.67↑
→
211↓
5000
Well faceted MCD
↑
0.78↑
↓
161↓↓
→
0.58↓
↓↓
207↓
→
0.58↓
↓↓↓
307↑
10000
20000
MCD+non-diamond phases Polycrystalline with etched faces
1000
Well faceted MCD
→
0.6→
↓
357↑
5000
Well faceted MCD
→
0.55↓
↓
325 ↑
10000
Fine grained MCD
↓↓
0.43↓
↓↓
164↓↓
20000
Ballas NCD
↓↓
0.33↓↓
↓↓↓
193↓
1000
Well faceted MCD
→
0.63→
→
296 ↑
5000
Well faceted MCD
→
0.6→
↑
311↑
10000
Well faceted MCD
↓
0.5↓
↑↑
225 ↓
20000
Well faceted MCD
↓
0.17↓↓↓
↑
193↓
Si-doped
N-doped
annotation：→、↓、↑ indicated the trend of change is constant, declining and rising compared with undoped diamond films. The more quantity of the arrow, the more obvious of the change.
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ACCEPTED MANUSCRIPT Acknowledgments This research is sponsored by the Program for Young Excellent Talents in Tongji University (2015KJ011) and the National Natural Science Foundation of China (No.71601144). Reference [1] Najar K A, Sheikh N A, Shah M A. Enhancement in Tribological and Mechanical Properties of Cemented Tungsten Carbide Substrates using CVD-diamond Coatings [J]. Tribology in Industry, 2017, 39 (1): 20-30. [2] Radhika R, Ramachandra Rao M S. Growth and tribological properties of diamond films on silicon and tungsten carbide substrates [J]. Appl Phys A 2016, 122 (11): 937. [3] Srikanth V V S S, Sampath Kumar P, Kumar V B. A Brief Review on the In Situ Synthesis of Boron-Doped Diamond Thin Films [J]. International Journal of Electrochemistry, 2012, 2012: 1-7. [4] Kuntumalla M K, Elfimchev S, Chandran M, Hoffman A. Raman scattering of nitrogen incorporated diamond thin films grown by hot filament chemical vapor deposition [J]. Thin Solid Films 2018, 653: 284-292. [5] Rakha S A, Xintai Z, Zhu D, Guojun Y. Effects of N2 addition on nanocrystalline diamond films by HFCVD in Ar/CH4 gas mixture [J]. Curr Appl Phys 2010, 10 (1): 171-175. [6] Ullah M, Rana A M, Ahmed E, Malik A S, Shah Z A, Ahmad N, Mehtab U, Raza R. Tribological performance of polycrystalline tantalum-carbide-incorporated diamond films on silicon substrates [J]. Physica B-Condensed Matter, 2018, 537: 277-282. [7] Liu X J, Lu P F, Wang H C, Ren Y, Tan X, Sun S Y, Jia H L. Morphology and structure of Ti-doped diamond films prepared by microwave plasma chemical vapor deposition [J]. Appl Surf Sci 2018, 442: 529-536. [8] Din S H, Shah M A, Sheikh N A, Najar K A, Ramasubramanian K, Balaji S, Ramachandra Rao M S. Influence of boron doping on mechanical and tribological properties in multilayer CVD-diamond coating systems [J]. Bull Mater Sci 2016, 39 (7): 1753-1761. [9] Wei Q, Ashfold M N R, Mankelevich Y A, Yu Z M, Liu P Z, Ma L. Diamond growth on WC-Co substrates by hot filament chemical vapor deposition: Effect of filament–substrate separation [J]. Diam Relat Mater, 2011, 20 (5-6): 641-650. [10]Srinivasan B, Ramachandra Rao M S, Rao B C. On the development of a dual-layered diamond-coated tool for the effective machining of titanium Ti-6Al-4V alloy [J]. J Phys D: Appl Phys 2017, 50 (1): 015302. [11]Chandran M, Kumaran C R, Gowthama S, Shanmugam P, Natarajan R, Bhattacharya S S, Ramachandra Rao M S. Chemical vapor deposition of diamond coatings on tungsten carbide (WC–Co) riveting inserts [J]. Int J Refract Met Hard Mater 2013, 37: 117-120. [12]Fraga M A, Contin A, Rodríguez L A A, Vieira J, Campos R A, Corat E J, Airoldi V J T. Nano- and microcrystalline diamond deposition on pretreated WC–Co substrates: structural properties and adhesion [J]. Materials Research Express, 2016, 3 (2): 025601. [13]Wang L, Shen B, Sun F, Zhang Z. Effect of pressure on the growth of boron and nitrogen 17 / 18
ACCEPTED MANUSCRIPT doped HFCVD diamond films on WC–Co substrate [J]. Surf Interface Anal 2015, 47 (5): 572586. [14]Tang C J, Neves A J, Pereira S, Fernandes A J S, Grácio J, Carmo M C. Effect of nitrogen and oxygen addition on morphology and texture of diamond films (from polycrystalline to nanocrystalline) [J]. Diam Relat Mater, 2008, 17 (1): 72-78. [15]Souza F A, Azevedo A F, Giles C, Saito E, Baldan M R, Ferreira N G. The Effect of Boron Doping Level on The Morphology and Structure of Ultra/Nanocrystalline Diamond Films [J]. Chem Vap Deposition 2012, 18 (4-6): 159-165. [16]Musale D V, Sainkar S R, Kshirsagar S T. Raman, photoluminescence and morphological studies of Si- and N-doped diamond films grown on Si(100) substrate by hot-filament chemical vapor deposition technique [J]. Diam Relat Mater, 2002, 11 (1): 75-86. [17]Wei Q-p, Yu Z M, Ashfold M N R, Ye J, Ma L. Synthesis of micro- or nano-crystalline diamond films on WC-Co substrates with various pretreatments by hot filament chemical vapor deposition [J]. Appl Surf Sci 2010, 256 (13): 4357-4364.
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Liang Wang, Jinfei Liu, Tang Tang, Nan Xie, Fanghong Sun PII:
S0921-4526(18)30591-X
DOI:
10.1016/j.physb.2018.09.018
Reference:
PHYSB 311058
To appear in:
Physica B: Physics of Condensed Matter
Received Date:
24 July 2018
Accepted Date:
10 September 2018
Please cite this article as: Liang Wang, Jinfei Liu, Tang Tang, Nan Xie, Fanghong Sun, The optimization of the doping level of boron, silicon and nitrogen doped diamond film on Co-cemented tungsten carbide inserts, Physica B: Physics of Condensed Matter (2018), doi: 10.1016/j.physb. 2018.09.018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT The optimization of the doping level of boron, silicon and nitrogen doped diamond film on Co-cemented tungsten carbide inserts Liang Wang1*, Jinfei Liu1, Tang Tang1, Nan Xie1, Fanghong Sun2 1School
2School
of Mechanical Engineering, Tongji University, Shanghai, 201804, P.R. China
of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P.R. China
Abstract Boron doped, silicon doped and nitrogen doped diamond films with different doping level in gas phase are deposited on Co-cemented tungsten carbide (WC-Co) inserts using hot filament chemical vapor deposition (HFCVD) method. Trimethyl borate ((CH3O)3B), tetraethoxysilane (Si(OC2H5)4) and urea (CO(NH2)2) are dissolved in acetone to server as boron, silicon and nitrogen precursors, respectively. The as-deposited diamond films are characterized by field emission scanning electron microscope (FESEM), Raman spectroscopy and indentation tests. The results suggested that doping source and doping level will affect the surface morphology, growth rate, quality and adhesion of diamond film. The optimized doping level to obtain diamond films deposited on WC-Co substrate for mechanical applications with well faceted crystal, low defect, low cluster structure and high adhesive strength is 5000 ppm, 10000 ppm and 10000 ppm for boron, silicon and nitrogen doping, respectively. Keywords: boron; silicon; nitrogen; doping level; doped diamond film; WC-Co. 1. Introduction The performances of the diamond films prepared by chemical vapor deposition (CVD) is attractive as ideal tool, die, mechanical bearing and seal coatings for its excellent characteristic, such as high hardness and wear resistance, good thermal conductivity and low friction and thermal coefficient[1, 2]. In order to broaden the application filed of diamond film, the performance of diamond films can be tailored by adjusting the growth condition. Doping is an important way to apply diamond film to the field of semiconductor. Doping level is one of the important parameters of doped diamond film, it has significant influence on the electrical properties of diamond films[3]. But at present, in order to apply the doped diamond to the field of electrics or electrochemistry, researches are mainly focus on the properties of doped diamond films deposited on the substrates like silicon, niobium or tantalum[4, 5]. In addition, it is reported that doping also has certain effects on the growth behavior, tribological behavior of diamond films [6-8]. To our knowledge, the properties of the doped diamond films on the Co-cemented carbide (WC-Co) have still not been studied systematically so far. It is well known that WC1 / 18
ACCEPTED MANUSCRIPT Co is comparative stable under CVD processing conditions and is widely used as the cutting tool, riveting tool or die materials[9-12]. The surface morphology, structure and quality of the diamond film will affect the tribological or cutting performance of diamond coated dies or tools. Thus, doping will affects the application properties of diamond film in mechanical fields. In this study, we focus on the effects of doping level on the morphology, quality, growth rate, quality and adhesion rather than the electricity of diamond films on WC-Co substrates. In order to meet the need of different mechanical application, three different types of doped diamond films, namely boron, silicon and nitrogen doped diamond films with different doping level are systematically studied. 2. Experiments details The boron doped (B-doped), silicon doped (Si-doped) and nitrogen doped (N-doped) diamond films are deposited using a bias-enhanced hot filament CVD (HFCVD) apparatus. Flat square shaped WC-6%Co inserts are used as substrate. For comparison, undoped diamond films are also deposited using the same deposition parameters. To coarse the surface and remove the surface Co element, as-received inserts are firstly submitted to react with Murakami’s reagent and Caro’s acid, and then abraded with diamond powder[13]. Acetone and hydrogen are adopted as reactive gases. Trimethyl borate (CH3(3)BO3), tetraethoxysilane (C8H20O4Si) and urea (NH2CONH2) is dissolved in acetone with preset B/C, Si/C and N/C atomic ratio (1000 ppm, 5000 ppm, 10000ppm and 20000 ppm) to serve as boron, silicon and nitrogen precursors. The mixed solution in the liquid container is introduced in the reactor by part of H2 and the flow rate of mixed solution is controlled by the flow rate of carrier gas and the vapor pressure of mixed solution. The vapor pressure of mixed solution is associated with its temperature which is maintained at 0 °C by immersed the container in glacial-aqueous mix solution. The gas phase is activated by 6 electrical heated carburized tantalum wires at intervals of 38 mm, which are 10 mm above the substrate surface. The detailed deposition parameters of the diamond films are listed in table 1. Table 1 The detailed deposition parameters of doped CVD diamond films.
nuclear
growth
100/200
80/200
Chamber Pressure (kPa)
1.6
4
filament temperature (°C)
2200~2300
2200~2300
Substrate temperature (°C)
800~900
800~900
Bias current (A)
4
3
Duration (h)
0.5
5.5
Carrier gas (mL/min)/H2 (mL/min)
For characterization, filed emission scanning electron microscopy (FESEM) is used to 2 / 18
ACCEPTED MANUSCRIPT observe the morphology, microstructure, grain size and film thickness of as-deposited diamond films. As well, Raman spectroscopy is employed to identify the quality and purity of diamond films. Rockwell indentation tests are carried out to qualitatively evaluate the adhesion of the diamond films. 3. Results and discussion 3.1 The effect of doping level on the morphology and growth rate of diamond films
The surface and section morphology of as-deposited diamond films is observed by FESEM, the working voltage is 5 kV, working distance is about 10 to 15 mm and the detector is SE2. The surface morphology and cross-section morphology of undoped diamond films are shown in Fig.1. The conventional undoped diamond films show well faceted polycrystalline morphology, the grain size is about 2-3 μm, the columnar growth structure and film thickness of 3.7 μm can be detected from the cross section morphology.
Fig.1. The surface and cross-section morphology of undoped diamond films.
The surface morphology of B-doped diamond films with different doping level are shown in Fig.2. When the doping level in the gas phases is 1000 and 5000 ppm, B-doped diamond films exhibit a similar morphology with that of undoped ones, except the grain size has little increased to 3-4 μm. However, when the doping level increases to 10000 ppm, the morphology begin to change extensively. Although the diamond can maintain its crystallinity, there are many small diamond grains between the larger grains, and also some disordered materials can be observed. When the doping level further increased to 20000 ppm, the diamond grains seem be etched seriously and pores can be detected on the surface. The reason may be that boron atoms have limit solubility in the diamond lattice, too much boron atoms may cause the distortion of diamond lattice. We can see that B-doped diamond films also present a columnar growth structure from Fig.3 which shows the cross section morphology of B-doped diamond film. However, incontinuity cross section can be detected due to the present of pores as shown in the surface
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(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.2. The surface morphology of B-doped diamond films deposited at different doping level.
(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.3. The cross-section morphology of B-doped diamond films deposited at different doping level.
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ACCEPTED MANUSCRIPT morphology under the doping level of 20000 ppm. The film thickness first increases then decreases with the boron doping level. The film thickness is about 4 μm when the doping level is 1000 ppm and increases to 4.7 μm when the doping level increases to 5000 ppm. However, the thickness decreases to 3.5 μm when the doping level increases to 10000 and 20000 ppm. As shown in Fig.4, the surface morphology and grain size of Si-doped diamond films with relative low doping level of 1000 and 5000 ppm is still similar to that of undoped ones. When the doping level increases to 10000 ppm, the surface presents fine grained diamond with the grain size at about 200 nm. When the doping level increases to 20000 ppm, nano-crystalline diamond (NCD) film with typical cauliflower morphology is obtained, the grain size further decreases to less than 100 nm. However, the aggregation of the diamond is quiet obvious, it seems possessing a large fluctuating morphology and showing a rough surface.
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.4. The surface morphology of Si-doped diamond films deposited at different doping level.
The cross-sectional morphology of Si-doped diamond films (Fig.5) shows that the growth structure of Si-doped diamond films is also columnar structure, the film gradually becomes compact and the thickness of the film gradually decreases with the increase of doping level. The film thickness is 3.6, 3.3, 2.6 and 2 μm for the doping level of 1000, 5000, 10000 and 20000 ppm, respectively.
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ACCEPTED MANUSCRIPT
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.5. The cross-section morphology of Si-doped diamond films deposited at different doping level.
Figure 6 shows that well faceted diamond can be obtained when nitrogen doping level is 1000 ppm. As indicated by the dash circle in Fig.6 (a), pentagon pits on the grain indicate the twining of {111} face. It also shows that the diamond growth rate parameter α is greater than 3 under the nitrogen doping level of 1000 ppm, thus {111} is the predominant apparent plane of diamond crystal[14]. The average grain size is smaller than that of undoped ones, it will be further reduced by the increasing of the doping level. The fine grained diamond with cuboctahedron structure appears at the doping level of 20000 ppm, the exposure plane is mainly (111) and (100), the <100> direction of the cuboctahedron is perpendicular to the substrate surface. The cross section morphology of N-doped diamond films is shown in Fig.7. The thickness of the diamond films with nitrogen doping level of 1000 ppm and 5000 ppm is similar to that of undoped diamond films, the values are about 3.8 and 3.6 μm, respectively. The thickness of diamond films decreases with the increase of nitrogen doping level. At the doping level of 10000 ppm, the thickness reduces to about 3 μm. When nitrogen doping level is 20000 ppm, the growth of the film is very slow, and its thickness is only 1μm during the deposition of 6 hours. 3.2 The effect of doping level on the quality of diamond films
The Raman spectra of as-deposited diamond films are excited by He–Ne laser with a
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(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C=20000 ppm
Fig.6. The surface morphology of N-doped diamond films deposited at different doping level.
(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C= 20000 ppm
Fig.7. The cross-section morphology of N-doped diamond films deposited at different doping level.
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Fig.8. The Raman spectrum of the undoped diamond films.
(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.9. The Raman spectra of B-doped diamond films at different doping level.
wavelength of 632.8 nm at room temperature. The Raman spectrum of undoped diamond film is illustrated in Fig.8. The sharp peak near 1332 cm−1 corresponding to the first order Raman peak of diamond, indicating the great quality of diamond film. The broad peak at about 1070 and 1580 cm−1 can be attributed to the disorder carbon and graphite at the grain boundary of the diamond[12]. Compared with undoped diamond films, the Raman spectra of B-doped diamond film shown in Fig.9 changed obviously when the doping level is only 1000 ppm. The peak at 1332 cm−1 become asymmetric and an obvious broad peak at about 1200 cm−1 can be 8 / 18
ACCEPTED MANUSCRIPT detected. These two features reveal the metallic of the diamond that is to say the diamond can conduct electric after boron doping [15]. The results also indicate that the boron atom may enter the diamond lattice and have a relative high doping efficiency. The intensity of the peak at 1332 cm−1 decreases as the increase of the doping level. When the doping level increases to 20000 ppm, the diamond peak totally disappears, and shows a more broaden Raman peak. Moreover, the graphite peak at 1580 cm−1 can be obviously detected. The results indicate that the diamond begin to graphitization and the quality has obviously decreased as excessive boron atoms are introduced in the gas phases. As noticed in Fig.10, the Raman spectra are similar to that of undoped ones when the silicon doping level is 1000 ppm and 5000 ppm. The sharp peak near 1332 cm−1 indicated that the film is mainly composed of diamond phases. When the atom ratio Si/C in the gas phases is 20000 ppm, the peak at about 1332 cm−1 becomes broaden, it indicated the decreasing of the quality of diamond film[16].
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.10. The Raman spectra of Si-doped diamond films at different doping level.
As shown in Fig.11, the Raman spectra of N-doped diamond films with the doping level of 1000 ppm are similar to that of undoped diamond films. The results reveal that the nitrogen dopant have little influence on the diamond quality under relative low doping level. It also shows that the nitrogen doping efficiency may lower than that of boron doping. However, the 9 / 18
ACCEPTED MANUSCRIPT non-diamond phases decrease when the doping level increase to 5000 ppm, the broad peak at approximately 1220 cm−1 could be attributed the disordered sp3 carbon structure in the diamond film. When the doping level comes to 10000 ppm，the Raman spectra of N-doped diamond films only show distinct diamond peak near 1332 cm−1, indicating a relative high diamond quality. However, the content of graphite phases increases when the doping level increases to 20000 ppm. The graphite phases can be characterized by the broad peak at about 1580 cm−1. The results may be attributed to that the large doping level in the gas phases will produces more CN or HCN radicals, these radical will induce severe H abstract, and thus cause more dangling bonds on the diamond surface. Consequently, the surface can be reconstructed to form graphite phases.
(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C=20000 ppm
Fig.11. The Raman spectra of N-doped diamond films at different doping level.
3.3 The effect of doping level on the adhesion of diamond films
The adhesion between diamond films and WC-Co substrates is qualitatively measured by Rockwell hardness tester with a diamond indenter (angle =120°, radius =0.2 mm). The indentation FESEM morphology of the undoped diamond film under the load of 100 kgf is shown in Fig.12. A large area of the diamond film peels off on one side of the force point. The maximum radius of the indentation imprint is about 264 μm. 10 / 18
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Fig.12. The indentation imprint of undoped diamond films.
The indentation morphology of B-doped diamond films at different doping level is shown in Fig.13. It can be seen that when relatively low content of boron atom is introduced in the gas phases, the peeling off of the diamond film also occurs on one side of the force point while the maximum radius of the imprint decreases slightly to 211 μm. When the doping level is 5000 ppm, the shape of the indentation imprint is round. The peeling and cracking of the diamond film are not found except the fracture of a small amount of diamond film on the edge of the imprint. The maximum radius of the indentation imprint is 161 μm. It indicated that the adhesive strength is relatively high at the doping level of 5000 ppm. When the boron doping level further increased to 10000 ppm, the film peeling off on the side of the force point occurs again, the maximum radius of indentation imprint is 207 μm. When boron doping level increases to 20000 ppm, a large area of the film peels off and exposes the WC substrate, the maximum radius of the indentation imprint reaches to 307 μm. This is due to the increasing of the non-diamond phase in the film when the boron in the gas phases is too high. The incorporation of the excessive boron atom will induces a larger lattice distortion and defects, resulting in a larger internal stress of the film, thus lower the adhesion strength between the film and substrate. The adhesion of the diamond film is poor at the low silicon doping level as indicated in Fig.14. It shows large area of diamond film peels off near the force point. The diamond films show round indentation imprint when the doping level increases to 10000 ppm, only short radiated cracking rather than peeling off of the diamond film can be seen. When the doping level further increases to 20000 ppm, the adhesive strength between diamond film and the substrate will be further enhanced as there are no cracks near the indentation. However, it can be seen that the surface of the diamond film has a large number of small particles and the surface is not smooth, which is due to the diamond clusters mentioned above. The maximum indentation imprint radius of Si-doped diamond films at 1000 ppm, 5000 ppm, 10000 ppm and 20000 ppm is 357, 325, 164 and 193 μm, respectively.
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ACCEPTED MANUSCRIPT
(a) B/C=1000 ppm
(b) B/C=5000 ppm
(c) B/C=10000 ppm
(d) B/C=20000 ppm
Fig.13. The indentation imprint of B-doped diamond films at different doping level.
(a) Si/C=1000 ppm
(b) Si/C=5000 ppm
(c) Si/C=10000 ppm
(d) Si/C=20000 ppm
Fig.14. The indentation imprint of Si-doped diamond films at different doping level.
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ACCEPTED MANUSCRIPT It can be seen from the indentation morphology of the N-doped diamond film in Fig.15 that the expansion range of the peeling off of the diamond film is far away from the indentation center at the low nitrogen doping level. The result indicates that the adhesion of the film and substrate is not high. With the increasing of nitrogen doping level, the adhesion has been improved. At the doping level of 10000 ppm and 20000 ppm, there are no large area of crack and film peeling off after the indentation test. Only a small amount of the delamination of film appears. It is possible that the growth rate of diamond is slow with the increasing of the nitrogen doping level, which relieves the competitive growth between diamond grains and reduces the internal stress, and thus help to improve the adhesion. Even though, the adhesion is weaker compared with that of diamond films under the condition of B/C=5000 ppm, Si/C=10000 and Si/C=20000 ppm. The maximum indentation imprint radius of N-doped diamond films at 1000 ppm, 5000 ppm, 10000 ppm and 20000 ppm is 296, 311, 225 and 193 μm, respectively.
(a) N/C=1000 ppm
(b) N/C=5000 ppm
(c) N/C=10000 ppm
(d) N/C=20000 ppm
Fig.15. The indentation imprint of N-doped diamond films at different doping level.
From the indentation results, we found that diamond films with high adhesion can be obtained by using suitable doping level of boron or silicon. To reveal the mechanism of the adhesion improving, the composition of the interface of the diamond and the substrate is first evaluated by using energy dispersive spectroscopy (EDS). As shown in Fig.16, one silicon peak can be detected in the spectrum of Si-doped diamond film. The doped elements cannot be detected in other type of doped diamond films. Si-doped diamond films may formed a silicon containing compound in the interface which may beneficial to obstruct the diffusion of cobalt 13 / 18
ACCEPTED MANUSCRIPT elements into the diamond film during the deposition, thus improving the adhesion of the diamond films.
Undoped
B-doped
Si-doped
N-doped
Fig.16. EDS analysis on the interface of the diamond films and WC-Co substrate.
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ACCEPTED MANUSCRIPT The indentation results also reveal that B-doped diamond films present high adhesion while we cannot detect boron peaks from the EDS analysis. This may be due to the fact that boron is a light element, so the boron peak will overlaps with the carbon peak. Thus, the X-ray diffraction (XRD) is used to further reveal the mechanism of the adhesion improvement by boron doping. Fig.17 presents the XRD patterns of the WC-Co sample after nucleation for 15 min under the condition of undoped and boron doping of 5000 ppm in the gas phases. The results indicate that a weak diffraction peak at about 2θ of 44° can be detected in the boron doped diamond film. The peak can be corresponded to the diffraction peak of CoWB, which indicates that CoWB is formed during the deposition of the diamond films after boron doping. The stable B-Co compound formed in the process of CVD will reduce the catalytic action of cobalt element in the substrate, thus improving the adhesion of the film[17].
(a) undoped diamond films
(b) B-doped diamond films Fig.17. The XRD pattens of undoped diamond films and B-doped diamond films deposited at the doping level of 5000 ppm after nuclear of 15 min.
4. Conclusions In this study, undoped diamond film and boron, silicon and nitrogen doped diamond films with different doping level are deposited on WC-6%Co inserts using HFCVD method. The characterization results of the as deposited diamond film are summarized in table 2. From the results, we can find that doping with boron, silicon or nitrogen will affect the morphology, 15 / 18
ACCEPTED MANUSCRIPT growth rate, quality and adhesion of the HFCVD diamond film on WC-Co substrate. To obtain CVD diamond films with well faceted crystal, better surface quality, moderate growth rate and high adhesion, the relative optimal doping level for different types of doped diamond films is as follows: 5000 ppm for boron doping, 10000 ppm for silicon doping and 10000 ppm for nitrogen doping. Furthermore, we also can get the conclusion that: a) We can using boron doping to improve the growth rate of micro crystalline diamond (MCD) films. b) The silicon doping can be used to refine the diamond grain. c) The diamond quality can be improved by nitrogen doping. d) To improve the adhesion of diamond films on WC-Co substrate, we can utilize boron doping or silicon doping. Table 2 The characterization results of doped HFCVD diamond films on WC-Co substrate. Doping level Undoped
B-doped
Morphology
Grain
Growth
size
rate
Quality
ISmprint radius
0
Well faceted MCD
→
0.62→
→
264→
1000
Well faceted MCD
↑
0.67↑
→
211↓
5000
Well faceted MCD
↑
0.78↑
↓
161↓↓
→
0.58↓
↓↓
207↓
→
0.58↓
↓↓↓
307↑
10000
20000
MCD+non-diamond phases Polycrystalline with etched faces
1000
Well faceted MCD
→
0.6→
↓
357↑
5000
Well faceted MCD
→
0.55↓
↓
325 ↑
10000
Fine grained MCD
↓↓
0.43↓
↓↓
164↓↓
20000
Ballas NCD
↓↓
0.33↓↓
↓↓↓
193↓
1000
Well faceted MCD
→
0.63→
→
296 ↑
5000
Well faceted MCD
→
0.6→
↑
311↑
10000
Well faceted MCD
↓
0.5↓
↑↑
225 ↓
20000
Well faceted MCD
↓
0.17↓↓↓
↑
193↓
Si-doped
N-doped
annotation：→、↓、↑ indicated the trend of change is constant, declining and rising compared with undoped diamond films. The more quantity of the arrow, the more obvious of the change.
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ACCEPTED MANUSCRIPT Acknowledgments This research is sponsored by the Program for Young Excellent Talents in Tongji University (2015KJ011) and the National Natural Science Foundation of China (No.71601144). Reference [1] Najar K A, Sheikh N A, Shah M A. Enhancement in Tribological and Mechanical Properties of Cemented Tungsten Carbide Substrates using CVD-diamond Coatings [J]. Tribology in Industry, 2017, 39 (1): 20-30. [2] Radhika R, Ramachandra Rao M S. Growth and tribological properties of diamond films on silicon and tungsten carbide substrates [J]. Appl Phys A 2016, 122 (11): 937. [3] Srikanth V V S S, Sampath Kumar P, Kumar V B. A Brief Review on the In Situ Synthesis of Boron-Doped Diamond Thin Films [J]. International Journal of Electrochemistry, 2012, 2012: 1-7. [4] Kuntumalla M K, Elfimchev S, Chandran M, Hoffman A. Raman scattering of nitrogen incorporated diamond thin films grown by hot filament chemical vapor deposition [J]. Thin Solid Films 2018, 653: 284-292. [5] Rakha S A, Xintai Z, Zhu D, Guojun Y. Effects of N2 addition on nanocrystalline diamond films by HFCVD in Ar/CH4 gas mixture [J]. Curr Appl Phys 2010, 10 (1): 171-175. [6] Ullah M, Rana A M, Ahmed E, Malik A S, Shah Z A, Ahmad N, Mehtab U, Raza R. Tribological performance of polycrystalline tantalum-carbide-incorporated diamond films on silicon substrates [J]. Physica B-Condensed Matter, 2018, 537: 277-282. [7] Liu X J, Lu P F, Wang H C, Ren Y, Tan X, Sun S Y, Jia H L. Morphology and structure of Ti-doped diamond films prepared by microwave plasma chemical vapor deposition [J]. Appl Surf Sci 2018, 442: 529-536. [8] Din S H, Shah M A, Sheikh N A, Najar K A, Ramasubramanian K, Balaji S, Ramachandra Rao M S. Influence of boron doping on mechanical and tribological properties in multilayer CVD-diamond coating systems [J]. Bull Mater Sci 2016, 39 (7): 1753-1761. [9] Wei Q, Ashfold M N R, Mankelevich Y A, Yu Z M, Liu P Z, Ma L. Diamond growth on WC-Co substrates by hot filament chemical vapor deposition: Effect of filament–substrate separation [J]. Diam Relat Mater, 2011, 20 (5-6): 641-650. [10]Srinivasan B, Ramachandra Rao M S, Rao B C. On the development of a dual-layered diamond-coated tool for the effective machining of titanium Ti-6Al-4V alloy [J]. J Phys D: Appl Phys 2017, 50 (1): 015302. [11]Chandran M, Kumaran C R, Gowthama S, Shanmugam P, Natarajan R, Bhattacharya S S, Ramachandra Rao M S. Chemical vapor deposition of diamond coatings on tungsten carbide (WC–Co) riveting inserts [J]. Int J Refract Met Hard Mater 2013, 37: 117-120. [12]Fraga M A, Contin A, Rodríguez L A A, Vieira J, Campos R A, Corat E J, Airoldi V J T. Nano- and microcrystalline diamond deposition on pretreated WC–Co substrates: structural properties and adhesion [J]. Materials Research Express, 2016, 3 (2): 025601. [13]Wang L, Shen B, Sun F, Zhang Z. Effect of pressure on the growth of boron and nitrogen 17 / 18
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