Auger electron spectroscopy was used to study the

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The bonding state of cr/diamond interface was studied by Auger electron spectroscopy

diamond has many excellent properties [1,2], and is mostly used in cutting tools. However, due to the high surface energy and chemical inertia of diamond, the combination between diamond and metal matrix is weak, which affects the performance and service life of diamond cutting tools. Surface metallization is an effective method to solve this problem. Among them, the metallized diamond obtained by magnetron sputtering has good bonding strength, but the interface physical and chemical processes in the sputtering deposition process are not well understood at present [3,4]. In this study, a 150nm thick Cr layer was deposited on the surface of diamond particles by magnetron sputtering, and the bonding state of cr/diamond interface was studied by Auger electron spectroscopy

1 experimental method

the synthetic diamond particles with particle size of 40 ~ 50 mesh were placed in a rotating device, and a uniform Cr metal film was plated on the surface of the diamond particles by Ar atmosphere DC magnetron sputtering. The thickness of the Cr layer was controlled to 150nm. The vacuum degree of the preparation chamber is better than 2 × PA, AR partial pressure during sputtering is 0.15pa. The deposition rate is 0.4 nm/s, and the purity of Cr target and Ar gas is 99.999%

Auger electron spectroscopy analysis is carried out on the hi-610/sam scanning Auger electron spectrometer when the experimental opportunity with good quality is more and more durable. A single channel CMA energy analyzer is adopted, with an energy resolution of 0.3%. The analysis voltage of the coaxial electron gun is 3.0kv, the electron beam incidence angle is 60 °, and the vacuum degree of the analysis chamber is better than 2 × Pa。 The sputtering rate of Ar ion gun is calibrated to 30nm/min by thermal oxidation of SiO2. SEM experiments were carried out on csm950 scanning electron microscope. The resolution of the secondary electron image is better than 5 nm

2 experimental results and discussion

2.1 apparent morphology of cr/diamond samples prepared by magnetron sputtering

SEM results of diamond particles before and after Cr coating show that there is a significant difference between them. Many small white spots are uniformly distributed on the surface of diamond particles plated with Cr film. The energy spectrum analysis of SEM shows that the Cr content of foam granulator here is significantly higher than that of the black area, indicating that some metals gather and form island structure during the deposition of Cr film

2.2 interface diffusion during cr/diamond sample preparation

Fig. 1 is the auger depth profile of cr/diamond sample. It can be seen that the thickness of the metal Cr film is about 150nm, and the width of the interface layer between the metal Cr film and diamond is about 65nm, which is much wider than the interface layer produced by evaporation coating, indicating that the interface diffusion between cr/diamond has taken place. This is because during sputter deposition, high-energy CR atoms bombard the diamond surface and produce a partial "injection" effect, resulting in the diffusion of metal Cr to the diamond substrate

Fig. 1 auger depth analysis results of cr/diamond original samples

fig.1 the AES depth profile spectrum of

un annealed cr/diamond particle

the oxygen in the surface layer mainly comes from the surface adsorption and the natural oxidation layer of Cr, so the content is high. Because the Cr layer prepared on the surface of diamond particles is thin and has many structural defects, part of the adsorbed oxygen on the surface can diffuse into the film. At the same time, during the deposition of metal Cr film, there is residual oxygen or water vapor in the vacuum, so a small amount of residual oxygen can be generated in the film. The oxygen content is low and does not change with the depth of the film. In the depth profile, although interface diffusion occurred and a wide interface diffusion layer was formed, no stoichiometric carbide layer was formed

2.3 study on the interface reaction products of cr/diamond original samples

auger linear analysis can study the chemical state of each element in the film layer, so as to infer the interface chemical reaction and determine the species generated by the interface reaction [5 ~ 7]

Figure 2 shows the C KLL auger linear spectrum of the original sample, in which the peak of diamond standard is at 269.1ev, and there are three auger peaks of carbide, which are at 249.6ev, 257.9ev and 267.0ev respectively. The auger peak of C on the sample surface is located at 260.0ev, the shape is very similar to that of the diamond standard sample, and there is no sign of peak superposition. The carbon peak on the surface is mainly caused by the adsorbed C pollution (because the sputtering of Ar + will graphitize the diamond, the diamond standard sample shown is actually graphitized diamond)

Figure 2 the line shape of C KLL in variety

fig.2 the line shape of C KLL in variety

depth of cr/diamond deposited sample

at the cr/diamond interface near the Cr layer (sputtering for 3.5min), there is a significant difference between the auger shape of C and the surface. There are two weak peaks at 249.6ev and 257.9ev, and the shape and position of the peaks are very consistent with those of carbides; The peak at 267.0ev shows the characteristics of superposition of carbides and simple carbon, and the relative content of carbides is higher. After sputtering for 4.2min, the auger line of carbon is close to the diamond standard, but there are small bulges at 249.6ev and 257.9ev, and the position of the peak greater than 260 EV is slightly higher than the kinetic energy, reflecting the characteristics of carbide. This shows that the peak is still a composite peak of carbide and simple carbon, but the relative proportion of simple carbon is much higher than that of carbide. After 5.2min sputtering, the auger peak of carbon is closer to diamond in position and shape than that after 4.2min sputtering, which proves that the proportion of simple carbon is absolutely dominant. Although the diamond body has not been reached at this time, there is no carbide. In the interface layer, the carbides mainly come from the interface chemical reaction, while the simple carbon is produced by the diffusion of the diamond substrate

it can be seen that obvious interfacial diffusion occurred during the preparation of cr/diamond original samples, but the degree of chemical reaction was small. In the interface region, when the content of Cr is high, carbon mainly exists in the form of metal carbide; when the content of Cr is low, C mainly exists in the form of simple substance

Figure 3 shows the auger linear spectrum of Cr lm23m4, and the auger peak positions of each standard are shown in the figure. The auger peak shape of CR at the surface is wide, and its auger line shape is different from any standard. The specific species of this peak can not be inferred, but can only be considered as a mixture of multiple substances. However, its peak shape is quite different from that of oxide, indicating that Cr on the surface does not mainly exist in the state of oxide, and a large amount of oxygen on the surface mainly comes from adsorption pollution. After sputtering for 3.5min, the auger peak shape of the sample is very similar to that of Cr, that is, Cr mostly exists in the form of simple substance. After sputtering for 4.2min, the peak shape of the sample is obviously different from that of the simple substance cr. the peak position is low and there is a small bulge at 480ev, indicating that the peak is the superposition peak of metal and carbide. After sputtering for 5.5min, the small peak at 480ev is more obvious, and the peak near 485ev continues to move to the low kinetic energy of auger and the peak shape becomes wider, indicating that the content of carbide is greatly increased. At this time, the depth is close to the diamond body, the content of C is very high, but CR has not completely transformed into metal carbides, which indicates that although the sample has undergone significant interfacial diffusion, the degree of interfacial reaction is relatively light

Fig. 3 the line shape of Cr lm23m4 in

variety depth of cr/diamond deposited sample

Fig. 4 is the lm1m4 auger linear spectrum of CR. In this energy range, the auger lines of metal and carbide are very close. It can be seen that the auger line shape of the sample is different from that of the oxide, so the oxide content of Cr in the sample is very small. Figure 5 shows the MVV auger linear spectrum of CR. In this energy range, the auger transition of oxides is much stronger than that of carbides and metals, so the peak shape and intensity of samples can not reflect the amount of species. It can be seen from the figure that the auger peaks of the samples are between oxides and carbides, and the peak shape is wide, indicating that the two compounds exist at the same time. From this figure, it can be concluded that there is always a small amount of metal oxide in the metal coating and the interface area

Figure 4 linear spectrum of Cr lm1m4 at different depths

fig.4 the line shape of Cr lm1m4 in variety

depth of cr/diamond deposited sample

Figure 5 linear spectrum of Cr MVV at different depths of the original sample

fig.5 the line shape of Cr MVV in variety

depth of cr/d the industry specification is more difficult, and the diamond deposited sample

, The magnetron sputtering coating causes obvious interfacial diffusion and weak interfacial chemical reaction of cr/diamond. The driving force of the interfacial diffusion reaction is mainly the kinetic energy of the deposited atom CR

2.4 effect of sputtering power on interface diffusion reaction

in the depth profile of samples coated with different sputtering power, the relationship between the depth and interface width of 1:1 mixture layer and sputtering power is shown in the table below. It can be seen that the interface width of cr/diamond increases with the increase of sputtering power, which indicates that increasing sputtering power can promote the interface diffusion between cr/diamond; The isobaric point becomes deeper, indicating that the diffusion of Cr is strengthened

table the influence of sputtering power

on the interface diffusion and reaction

from the Cr film surface to the diamond body, the 1:1 point and the termination depth of the interface layer gradually deepen with the increase of power, and the former deepens faster than the latter with the increase of power, indicating that power has a greater impact on Cr diffusion. This is because increasing sputtering power can produce two effects. Firstly, the substrate temperature is increased to accelerate the diffusion rate between cr/diamond, but this effect is not significant, so the diffusion effect between solid molecules caused by it is very small; Secondly, the "injection" effect is enhanced, which is the main reason for the widening of the interface layer caused by the increase of power. With the increase of sputtering power, the kinetic energy of the particles emitted from the target is increased, so that the particles can overcome more intermolecular forces in the substrate and travel a longer distance. Macroscopically, the interface width increases, and the interface advances into the substrate. Because this phenomenon depends on the kinetic energy of sputtered deposited atoms, it has little effect on the diffusion of C atoms. At the same time, Cr with high energy can react with carbon atoms in diamond to form metal carbides at the interface

sample: 10 cement mortar blocks (110x110x10mm) were smeared between the two cement mortar blocks with standard slurry paint

3 conclusion

a 150nm thick Cr metal film was deposited on the surface of diamond particles by magnetron sputtering. In the coating process, the sample had a significant interfacial diffusion reaction, and cr2c3 metal carbides were formed at the interface. The source power of interfacial diffusion reaction is the high kinetic energy of sputter deposited atoms. Increasing the sputtering power can greatly promote the diffusion of Cr, thus enhancing the interfacial diffusion reaction. Wear resistant electrode

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