Method for evaluating diamond-like carbon film

Abstract

Provided is a method for evaluating a DLC film in which: the Raman spectrum of a DLC film is separated into five bands including an N-band, a D-band, a G−-band, a G+ band, and a D' band by curve fitting using a pseudo-forked function of a formula; and characteristics of the DLC film are evaluated on the basis of at least one of the peak position, the area, and the intensity of each of the separated bands.

Description

Evaluation method for diamond-like carbon films

[0001] The present disclosure relates to a method for evaluating a diamond-like carbon film, and in particular to a method for evaluating a carbon material using Raman spectroscopy.

[0002] As a method for evaluating a diamond-like carbon film (hereinafter referred to as "DLC film") as a carbon material using a Raman spectrum, Japanese Patent Application Laid-Open No. 2018-132483 discloses a method for evaluating the properties of the carbon material based on at least one of the peak position, area, and intensity of each of the separated bands, by curve fitting the Raman spectrum of the carbon material using a Voigt function obtained by integrating the sum of a Lorentz function superimposed on a Gaussian function and a BWF (Breit-Wigner-Fano) function superimposed on a Gaussian function.

[0003] Specifically, the plurality of bands are N band, D band, G band, － Band, G ＋ There are five bands: N band, D band, G band, and D' band. ＋ The D′ band and the D′ band were curve-fitted by a Lorentzian function superimposed with a Gaussian function, and G － The bands are curve-fitted using a BWF function that is a convolution of the Gaussian function.

[0004] The Voigt function used in the technology described in JP 2018-132483 A requires the convolution of a Lorentz function with a Gaussian function, and the convolution of a BWF function with a Gaussian function, making the calculation highly difficult. Furthermore, the parameters in the analysis are the peak position of each band (in other words, wave number, unit: cm －１ ) are five, the peak intensity of each band is five, G － There are 13 parameters in total: one for the half-width of the band (the width of the wavenumber at which the intensity is half the peak intensity), one for the half-width of another band, and one for the asymmetry parameter.

[0005] During analysis, the Raman spectrum curve obtained by measuring an actual carbon material is fitted to software programmed with a Voigt function by adjusting these parameters. When the analyst determines that the curve fits as a result of this fitting, the parameters become the attribute values ​​of each band, and the properties of the carbon material are evaluated based on these values. This fitting requires time-consuming manual work, involving changing and inputting the values ​​of 12 or 13 parameters through trial and error. This type of work relies heavily on the experience and intuition of the analyst, making it extremely difficult to obtain an optimal solution.

[0006] An embodiment of the present disclosure aims to provide an evaluation method that, when analyzing the Raman spectrum of a DLC film by separating it into the above-mentioned five band peaks, can obtain highly accurate results that are independent of the analyst and are more accurate and faster than when using a Voigt function.

[0007] The method for evaluating a DLC film according to an embodiment of the present disclosure is to curve-fit the Raman spectrum of the DLC film using the pseudo-Voigt function of Equation 1 to obtain the N band, D band, G band, and － Band, G ＋ The characteristics of the diamond-like carbon film are evaluated based on at least one of the peak position, area and intensity of each of the separated bands.

[0008]

[0009]

[0010]

[0011]

[0012] In the above formulas 1 to 4, j=1, j=2, j=3, j=4, and j=5 are the N band, the D band, and the G band, respectively. － Band, G ＋ are subscripts indicating parameters for the D band and the D′ band. ｊ(x) is a Gaussian function expressed by Equation 2, and L ｊ (x) is the Lorentz function expressed by Equation 3, and B ３ (x) is the BWF function expressed by Equation 4. ３ (x) is G － This formula is applicable only to the case of band (j=3). In the above formula 1, α is a function ratio (0≦α≦1) representing the weighting between the Gaussian function and the Lorentzian function in the first term on the right side, and β is a function ratio (0≦β≦1) representing the weighting between the Gaussian function and the BWF function in the second term on the right side.

[0013] In the above formulas 1 to 4, μ ｊ is the peak position of each band, and A ｊ is the peak intensity of each band, and σ ｊ is the half-width of the peak. ｋ is the asymmetry parameter. This asymmetry parameter q ｋ is the G band of the metallic nanotube. ＋ Bunt and G － The band split into two, G － This is due to the asymmetric shape of the bands alone, and is related to the interaction between the phonons and the electron continuum. Since many DLC films exhibit insulating properties, the asymmetry parameter q ｋ becomes infinity, and 1 / q ｋ = 0, in this case the BWF function of the above formula 4 is reduced to the Lorentz function of the above formula 3.

[0014] In the evaluation method of the DLC film, the peak position of the curve obtained by fourth-order differentiation of the Raman spectrum is determined as the peak position μ of each band. ｊ It is desirable to do so.

[0015] According to the DLC film evaluation method of the present disclosure, when the Raman spectrum of a DLC film is separated into the above-described five bands of peaks and analyzed, highly accurate results that are independent of the analyst can be obtained more accurately and quickly than when using a Voigt function.

[0016] 1 is a graph showing raw data of the Raman spectrum of a DLC film, five-band peaks separated from this Raman spectrum, and a fitting curve obtained by combining these five-band peaks. 2 is a graph showing the Raman spectrum of a DLC film and the peak positions obtained by fourth-order differentiation of this Raman spectrum. 3 is a graph showing the process of optimizing the function ratio in a pseudo-Voigt function. 4 is a graph showing the process of optimizing the function ratio in a pseudo-Voigt function. 5 is a flowchart showing the fitting procedure in the DLC film evaluation method of an embodiment. 6 is a time chart showing HF pulses in high-frequency high-power pulse sputtering in the film formation process of a hydrogen-free DLC film of an example. 7 is a graph showing five-band peaks identified by applying a Voigt function to the Raman spectrum of a hydrogen-free DLC film of an example and a fitting curve obtained by combining these peaks (top row), and the degree of deviation of the values ​​indicated by the fitting curve from the raw data of the Raman spectrum at each point of the Raman shift (bottom row). Graph showing five-band peaks identified by fitting a pseudo-Voigt function to the Raman spectrum of an example hydrogen-free DLC film and a fitting curve (top row) obtained by combining these peaks, and the degree of deviation (bottom row) of the values ​​indicated by the fitting curve from the raw data of the Raman spectrum at each point of the Raman shift. Graph showing five-band peaks identified by fitting a Voigt function to the Raman spectrum of an example hydrogen-containing DLC ​​film and a fitting curve (top row) obtained by combining these peaks, and the degree of deviation (bottom row) of the values ​​indicated by the fitting curve from the raw data of the Raman spectrum at each point of the Raman shift. Graph showing five-band peaks identified by fitting a pseudo-Voigt function to the Raman spectrum of an example hydrogen-containing DLC ​​film and a fitting curve (top row) obtained by combining these peaks, and the degree of deviation (bottom row) of the values ​​indicated by the fitting curve from the raw data of the Raman spectrum at each point of the Raman shift.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0018] (1) Significance of each band obtained from the Raman spectrum of the DLC film In the evaluation method of the diamond-like carbon film (hereinafter referred to as "DLC film") of this embodiment, the Raman spectrum of the DLC film is curve-fitted using a pseudo-Voigt function to obtain the N band, D band, G band, － Band, G ＋ The characteristics of the diamond-like carbon film are evaluated based on at least one of the peak position, area and intensity of each of the separated bands.

[0019] In this embodiment, a two-dimensional graphene sheet is used as the basic structure for Raman scattering of the DLC film. The two-dimensional graphene sheet has a six-membered ring (benzene), which is one of the most stable structures of carbon, as its basic component. The symmetry of the two-dimensional graphene sheet is D ６ｈ It belongs to the point group. ６ｈ The point cloud has four Raman active modes, each of which exhibits a unique corresponding second-rank tensor. １ｇ Two modes, E １ｇ Mode and E ２ｇ There is one for each mode. １ｇ Mode and E ２ｇ Modes A and B are Raman active for two-dimensional graphene sheets. １ｇ The vibration coordinate of the mode is x ２ +y ２ and E ２ｇ The vibration coordinate of the mode is x ２ -y ２ and xy. In the case of graphene sheets, A １ｇ The mode is assigned to the D band, and the E ２ｇ The G-band vibration is sp ３ It is also active towards bonds containing carbon.

[0020] In the evaluation method of the DLC film of this embodiment, the Raman spectrum is obtained by dividing the N (Network) band, the D band, and the G band in order of decreasing wave number as shown in FIG. － Band, G ＋The spectrum is divided into five active bands: the A band, the D′ band, and the D′ band. These five bands are divided by curve fitting using a pseudo-Voigt function, which is the sum of a Gaussian function and a Lorentzian function weighted at a predetermined ratio, and a Gaussian function and a BWF function weighted at a predetermined ratio. In FIG. 1 , each point represents the spectral intensity at each wavenumber, and the solid line is a fitting curve obtained by adding up the above five active bands.

[0021] N band is E １ｇ It comes from the mode. １ｇ The modes have xz and yz coordinates, and are not observed in two-dimensional graphene sheets because both modes have a z-axis component. １ｇ The mode is sp ３ Diamond crystals made of only carbon belong to O ｈ Point cloud T ２ｇ The N band corresponds to the three-dimensional inhomogeneous stretching vibration when the triple degeneracy of the mode (|xy| = |yz| = |zx|) is broken. ２ It not only represents the three-dimensional vibration of carbon, but also the sp ３ It is also active against three-dimensional vibrations of carbon. Therefore, the position and intensity of the N band can be used as an index for evaluating the diamond nature of the DLC film.

[0022] D band is A １ｇ It comes from the mode. １ｇ The mode is x ２ +y ２ Coordinates and z ２ The coordinates are two-dimensional x and ２ +y ２ The coordinates represent a circle, and the vibration is called the breathing vibration. This is unique to aromatic rings composed of equal bonds. However, when the rings are equivalent and crystalline, the vibrations of adjacent rings can be canceled out, so this band is called the D (Disorder) band, which is an indicator of the number of aromatic ring clusters and the size of each defect.

[0023] A １ｇ The mode is another tensor z ２This is attributed to the D' band. The D' band represents the stretching vibration between opposing aromatic ring clusters, and is therefore an indicator of their density. The pair of D and D' bands appears when the graphene sheet is damaged in some way.

[0024] G band is E ２ｇ It comes from the mode. ２ｇ Mode is x ２ -y ２ It has x and y coordinates. ２ -y ２ =r ２ is a hyperbola, but the variation of r represents the stretching and contraction of the bond. ２ -y ２ The coordinates are sp ２ Carbon and sp ３ The G band corresponds to the stretching vibration of both carbon-carbon bonds. The coordinates of the G band coincide with another x- and y-coordinates by rotating π / 4 around the coordinate origin. Therefore, these coordinates are generally indistinguishable.

[0025] sp ２ A perfect graphene sheet or undistorted graphite composed only of carbon exhibits a single sharp G-band peak. On the other hand, in metallic carbon nanotubes, the G-band is ＋ Band and low wavenumber G － It is known that the G band splits into two bands. The former shows vibration in the tube axis direction, and the latter shows vibration in the circumferential direction where the strain is large. Also, by forcibly applying strain to the graphene sheet, the G band also splits into G ＋ Band and G － The band splits into two, and as the strain increases, the band splitting increases. － Band and G ＋ The ratio to the band is sp ２ This is an index that indicates the magnitude of distortion in the carbon, and therefore the magnitude of distortion in the entire DLC film.

[0026] (2) Pseudo Voigt Function The pseudo Voigt function used in this embodiment is as shown in the following formula 5. ｊ(x) is a Gaussian function shown in the following formula 6, and L ｊ (x) is the Lorentz function shown in the following formula 7. Also, B in the following formula 5 ３ (x) is the BWF function expressed by the following formula 8, and G － Applies to bands only.

[0027]

[0028]

[0029]

[0030]

[0031] In addition, μ in the above formulas 5 to 8 ｊ is the peak position of each band, and A ｊ is the peak intensity of each band, and σ ｊ is the half-width of the peak, α is a function ratio representing the weighting between the Gaussian function and the Lorentzian function, and β is a function ratio representing the weighting between the Gaussian function and the BWF function. The subscript j attached to each parameter takes an integer value from 1 to 5, and when j=1 it indicates a parameter for the N band, when j=2 it indicates a parameter for the D band, and when j=3 it indicates a parameter for the G － indicates the band parameters, and for j=4, G ＋ In addition, the BWF function shown in Equation 8 has an asymmetry parameter q ｋ and G － This applies only to the band case (j = 3). Note that since many DLC films exhibit insulating properties, the asymmetry parameter q ｋ becomes infinity, and 1 / q ｋ = 0, in this case the BWF function of the above formula 8 is reduced to the Lorentz function of the above formula 7.

[0032] peak position μ ｊ is the wave number (unit: cm) at the peak of each band. －１ ) represents the peak intensity A ｊ The peak intensity A is the intensity of the peak of each measured band. ｊIt is desirable to use a relative value normalized to the maximum intensity value of the measured data group, but the value measured by the measuring device may be used as is.

[0033] In this embodiment, the peak position μ ｊ is obtained as follows. That is, each point of the Raman spectrum shown in FIG. 2 is smoothed using a moving average, a boxcar integrator, or the Savitzky-Golay or Hites-Biemann algorithm. Then, by fourth-order differentiation of this smoothed curve, a curve with five peaks as shown in FIG. 2 is obtained. Each of these five peaks has a peak at 1200 cm －１ N band with a peak around 1330 cm －１ D band with a peak around 1420 cm －１ G with a peak near － Band, 1540cm －１ G with a peak near ＋ Band, and 1640 cm －１ That is, in this embodiment, the peak positions μ are determined based on the wave numbers at which these peaks are located. ｊ will be allocated to.

[0034] Half width σ ｊ is the width of the wavenumber at which the intensity is half of the peak intensity (unit: cm －１ For example, the peak position μ ｘ The peak intensity at A ｘ And the half width is σ ｘ When this is the case, μ ｘ ±σ ｘ At the position, the peak intensity is A ｘ / 2. That is, the half-width σ ｊ is a value indicating the degree of broadening from the peak of each band. When the DLC film does not contain hydrogen, the half-width σ of each band is ｊ In addition, when the DLC film contains hydrogen, the half-width σ of the bands other than the D band can be set to a common value. ｊ can be set as a common value, but the half width of the D band is a different value (σ Ｄ ) should be used.

[0035] The function ratio α is a value that contributes to the weighting of the Gaussian function component and the Lorentz function component in the first term on the right side of the pseudo-Voigt function, and is a value in the range of 0≦α≦1. This function ratio α can be determined, for example, as the value of α that gives the pseudo-Voigt function the highest degree of fit to a known approximation curve obtained by curve fitting using the Voigt function, which will be described later. For example, in FIG. 3, the curve obtained by the pseudo-Voigt function when α=0.9 is shown by a dashed line. The coefficient of determination (R ２ ) is 0.971513. On the other hand, FIG. 4 shows the curve obtained by the pseudo-Voigt function when α=0.1 as a dashed line. The coefficient of determination (R ２ ) is 0.99994. The coefficient of determination (R ２ ) are shown in Table 1 below. When the value of α is approximately 0.1, the coefficient of determination (R ２ ) is close to 1, and it is predicted that the compatibility with the Voigt function will be high. Furthermore, the value of α was examined in the vicinity of α = 0.1, and the coefficient of determination (R ２ ) was found to be the highest, and the optimal value of α was found to be 0.12. The function ratio β is a value that contributes to the weighting of the Gaussian function component and the BWF function component in the second term on the right side of the pseudo-Voigt function, and is a value in the range of 0≦β≦1. The optimal value of β can be found in the same way as α.

[0036]

[0037] From the above, among the parameters of the pseudo-Voigt function of this embodiment, the peak position μ ｊ is determined as described above, the parameters that need to be optimized are the peak intensity of each band (A ｊ ) for the hydrogen-free DLC film, and one half-width (σ ｊ ) or two half-widths (σ ｊ and σ Ｄ ) for a total of six or seven.

[0038] Here, the Voigt function that has conventionally been used for curve fitting is expressed by the following Equation 9 for the Raman spectrum of an insulating DLC ​​film.

[0039]

[0040] Of the two functions in Equation 9 above that are multiplied, the first function is a Lorentz function shown in Equation 10 below, and the second function is a Gaussian function shown in Equation 11 below.

[0041]

[0042]

[0043] The parameters involved in the calculation of the above formula 9 are the peak position of each band (ν ｊ ) and the peak intensity of each band (I Ｌｊ ) and half-width (Γ Ｌｊ and Γ Ｇ ) for a total of 12.

[0044] As described above, the Voigt function shown in Equation 9 requires the convolution integral of a Lorentz function and a Gaussian function, whereas the pseudo-Voigt function of this embodiment shown in Equation 5 is simply the sum of a Gaussian function and a Lorentz function, and the sum of a Gaussian function and a BWF function, and therefore is much easier to calculate.

[0045] Furthermore, while the calculation of the Voigt function shown in Equation 9 requires 12 parameters, the calculation of the pseudo-Voigt function of this embodiment shown in Equation 5 requires only 6 or 7 parameters, which means that the number of parameters to be adjusted is approximately half.

[0046] As described above, curve fitting of a Raman spectrum using the pseudo-Voigt function of this embodiment is much easier to calculate than when using the Voigt function shown in Equation 9, and the time required to obtain an optimal curve can be dramatically reduced.

[0047] (3) Curve Fitting Procedure Next, an example of the curve fitting procedure in the DLC film evaluation method of this embodiment will be described with reference to the flowchart of Fig. 5. In reality, each procedure in the flowchart of Fig. 5 is automated by storing a program incorporating the pseudo-Voigt function shown in Equation 4 in a storage device such as a computer's ROM (Read-Only Memory) or external storage, and having the computer's central processing unit (CPU) execute the program while expanding data into RAM (Random Access Memory).

[0048] First, in the step shown in S10, Raman spectrum data of the DLC film that has already been measured is read, and then in the step shown in S20, the range to be fitted and the initial conditions for fitting (for example, A ｊ and σ ｊ Then, the Raman spectrum data is fourth-order differentiated (see FIG. 2) to obtain five peak positions (μ ｊ ) is determined

[0049] Next, in the step shown in S30, the Raman spectrum data at each wave number is corrected using the linear method, and each data item is normalized using the maximum intensity value of the measurement data group.

[0050] Then, in the step shown in S40, the five peak positions (μ ｊ ) and then the six or seven parameters are appropriately substituted to perform fitting. This fitting is automated by a program that repeats calculations while changing the parameter values ​​until the degree of discrepancy between the value (f(x)) at each wavenumber obtained by the pseudo-Voigt function and the actual Raman spectrum data becomes equal to or less than a predetermined threshold.

[0051] Next, in step S50, it is determined whether the fitting curve obtained by fitting has converged within a certain range with respect to the original Raman spectrum data. If it is determined that the fitting curve has converged, in step S60, the values ​​of the parameters substituted into the pseudo-Voigt function during the final fitting are saved, and the obtained fitting curve is saved as an image and / or displayed on a screen.

[0052] When the curve fitting is completed, a determination is made in step S70 as to whether there is any Raman spectrum data to be curve fitted next. If there is, steps S10 and onward are repeated using new Raman spectrum data; if there is no new Raman spectrum data, the process ends.

[0053] On the other hand, if it is determined in step S50 that the fitting results have not converged, in other words, have diverged, it is assumed that the original Raman spectral data contains some kind of error (for example, an incorrect sample preparation or an incorrect measurement method), and therefore a decision is made in step S80 as to whether or not to replace the Raman spectral data. If replacement is to be made, steps S10 and thereafter are repeated using new Raman spectral data; if replacement is not to be made, the process ends.

[0054] (1) Preparation of Samples As samples to be used for Raman spectrum measurement, a hydrogen-free DLC film and a hydrogen-containing DLC ​​film were formed on a substrate using a graphite target with a diameter of 3 inches as described below.

[0055] (1-1) Hydrogen-free DLC film The hydrogen-free DLC film was formed using high-frequency inclusion high-power impulse magnetron sputtering (HF-HiPIMS). The film formation conditions were a distance between the graphite target and the substrate of 100 mm, a substrate rotation speed of 5 rpm, and an ultimate vacuum of 5×10 －４The sputtering gas was argon at a flow rate of 5 sccm, with a negative applied voltage of 810 V and a frequency of 200 Hz. The HF pulse shown in FIG. 6 had T1 of 20 μsec, T2 of 5 μsec, T3 of 50 μsec, T4 of 36 μsec, T5 of 3 μsec, and T6 of 3 μsec.

[0056] (1-2) Hydrogen-containing DLC ​​film The hydrogen-containing DLC ​​film was formed using alternating current high voltage burst plasma chemical vapor deposition (AC-HV-CVD). The film formation conditions were an AC voltage of 5 kV, an offset voltage of 2 kV, a frequency of 10 kHz, and methane gas flowing at a flow rate of 5 sccm as the film formation gas. The pulse conditions were 10 pulses per second, a film formation time of 1 hour, and an operating pressure of 39 Pa.

[0057] (2) Measurement of Raman Spectrum Raman spectra were measured using a laser Raman microscope (Raman-11, Nanophoton Corporation) at an excitation wavelength of 532 nm, a laser output of 0.5 mW, and a laser spot diameter of 2.55 μm. The exposure time was 90 seconds for the hydrogen-free DLC film and 30 seconds for the hydrogen-containing DLC ​​film.

[0058] (3) Curve Fitting An example of curve fitting using a pseudo-Voigt function based on the Raman spectra obtained by measuring the above-mentioned hydrogen-free DLC film and hydrogen-containing DLC ​​film is shown below in comparison with an example using a Voigt function.

[0059] (3-1) Hydrogen-free DLC film Figure 7 shows an example of curve fitting using a Voigt function for the Raman spectrum of a hydrogen-free DLC film. In this curve fitting, the 12 parameters mentioned above are manually adjusted and input to increase the degree of fit, and the fitting curve at the point where the degree of fit is highest is shown in the upper part of Figure 7. The lower part of Figure 7 shows the deviation ((r-f) / r x 100(%)), which is defined as the ratio of the difference between the value (f) indicated by the fitting curve and the raw data value (r), relative to the raw data value (r) of the Raman spectrum, which is indicated by a black dot in the graph in the upper part. The work to obtain this fitting curve took several hours. The chi-square value (χ ２ ) is 3.12, and the coefficient of determination (r ２ ) was 0.98874.

[0060] Figure 8 shows an example of curve fitting using a pseudo-Voigt function for the same Raman spectrum as in Figure 7. In this curve fitting, the six parameters mentioned above are automatically adjusted using the automated program shown in the flowchart of Figure 5, and the fitting curve at the point where the degree of fit is highest is shown in the upper part of Figure 8. The deviation shown in the lower part of Figure 8 is the same as that shown in the lower part of Figure 7. It took 2 to 3 seconds to obtain this fitting curve. In addition, the chi-square value (χ ２ ) is 1.974, and the coefficient of determination (r ２ ) was 0.99486. Here, the chi-squared value (χ ２ ) is smaller, the better the fit, and the closer the coefficient of determination is to 1, the better the fit. Therefore, both indicators show that curve fitting using the pseudo-Voigt function can obtain a fitting curve with higher accuracy in an extremely short time.

[0061] (3-2) Hydrogen-containing DLC ​​film Figure 9 shows an example of curve fitting using a Voigt function for the Raman spectrum of a hydrogen-containing DLC ​​film. The fitting curve shown in the upper part of Figure 9 and the deviation shown in the lower part of Figure 9 are the same as those in the upper and lower parts of Figure 7, respectively. The work to obtain this fitting curve took several hours. The chi-square value (χ ２ ) is 3.925, and the coefficient of determination (r ２ ) was 0.97583.

[0062] FIG. 10 shows an example of curve fitting using a pseudo-Voigt function for the same Raman spectrum as in FIG. 9. The fitting curve shown in the upper part of FIG. 10 and the deviation shown in the lower part of FIG. 10 are the same as those in the upper and lower parts of FIG. 8, respectively. The time required to obtain this fitting curve was 2 to 3 seconds. The chi-squared value (χ ２ ) is 3.458, and the coefficient of determination (r ２ ) was 0.97624. Both of these indices show that, similar to the case of the non-hydrogen-containing DLC ​​film, curve fitting using the pseudo-Voigt function can also be used for the hydrogen-containing DLC ​​film to obtain a fitting curve with higher accuracy in an extremely short time.

[0063] In addition, when comparing the fitting curve shown in the upper part of FIG. 8 with the fitting curve shown in the upper part of FIG. 10, it is found that in the hydrogen-containing DLC ​​film, G － Because the band is lower, it is 1420 cm －１ It can be seen that the surrounding area is flattened.

[0064] (3-3) Summary In all cases, by using the pseudo-Voigt function, fitting with a higher degree of fit than the results obtained with the Voigt function could be achieved in a significantly shorter time.

[0065] The embodiments of the present disclosure can be used as a method for evaluating a DLC film.

Claims

1. The Raman spectrum of the diamond-like carbon film is curve-fitted using the pseudo-Voigt function of Equation 1 to obtain the N band, D band, and G band. － Band, G ＋ and evaluating the characteristics of the diamond-like carbon film based on at least one of the peak position, area and intensity of each of the separated bands. (In Formulas 1 to 4, j=1, j=2, j=3, j=4, and j=5 represent the N band, the D band, and the G band, respectively.) － Band, G ＋ are subscripts indicating parameters for the G band and the D′ band, and in Equation 1, G ｊ (x) is a Gaussian function expressed by Equation 2, and L ｊ (x) is the Lorentz function expressed by Equation 3, and B ３ (x) is the BWF function expressed by Equation 4, α is a function ratio (0≦α≦1) representing the weighting of the Gaussian function and the Lorentz function in the first term on the right side, and β is a function ratio (0≦β≦1) representing the weighting of the Gaussian function and the BWF function in the second term on the right side. In Equations 1 to 4, μ ｊ is the peak position of each band, and A ｊ is the peak intensity of each band, and σ ｊ is the half-width of the peak, and in Equation 4, q ｋ is the asymmetry parameter.) 2. Peak position μ of each band ｊ The method for evaluating a diamond-like carbon film according to claim 1 , wherein ρ is a peak position of a curve obtained by fourth-order differentiation of the Raman spectrum.

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