Raman spectra were measured for diamonds in an inclusion of the Canyon Diablo iron meteorite. The wavenumber position of a Raman peak was found in the range between 1333 and 1318cm^, and the full width at half maximum (FWHM) of the Raman peak ranges from 25 to 117cm^. These results are similar to those of Raman spectra of diamonds synthesized by shock-induced high pressure and are consistent with the consensus that diamond in Canyon Diablo formed by impact shock. No diamond grains showing a relatively narrow FWHM (7cm^) were found in the inclusion

Masamichi Miyamoto

P(論文)Raman spectra were measured for diamonds in an inclusion of the Canyon Diablo iron meteorite. The wavenumber position of a Raman peak was found in the range between 1333 and 1318cm^, and the full width at half maximum (FWHM) of the Raman peak ranges from 25 to 117cm^. These results are similar to those of Raman spectra of diamonds synthesized by shock-induced high pressure and are consistent with the consensus that diamond in Canyon Diablo formed by impact shock. No diamond grains showing a relatively narrow FWHM (7cm^) were found in the inclusion.departmental bulletin pape

Miyamoto, Masamichi

National Institute of Polar Research Repository

Antarct. Meteorite Res., 11, 171-177, 1998 MICRO RAMAN SPECTROSCOPY OF DIAMONDS IN THE CANYON DIABLO IRON METEORITE: IMPLICATION FOR THE SHOCK ORIGIN Masamichi MIYAMOTO Mineralogical Institute, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 Abstract: Raman spectra were measured for diamonds in an inclusion of the Can­yon Diablo iron meteorite. The wavenumber position of a Raman peak was found in the range between 1333 and 1318 cm-1, and the full width at half maximum (FWHM) of the Raman peak ranges from 25 to 117 cm-1• These results are similar to those of Raman spectra of diamonds synthesized by shock-induced high pressure and are con­sistent with the consensus that diamond in Canyon Diablo formed by impact shock. No diamond grains showing a relatively narrow FWHM (7 cm-1) were found in the inclusion. 1. Introduction Diamond shows a strong Raman peak (F2g) near 1332 cm-1 (e.g., SouN and RAMDAS, 1970) which is usually used for the identification of the micro-structure of diamond. MIYAMOTO et al. (1988) measured the Raman spectrum of a diamond in the ALHA 77257 ureilite and suggested that ureilite diamond has formed from vapor in the primitive solar nebula because the FWHM (full width at half maximum) of the 1332 cm- 1 Raman peak of a ureilite diamond is as much broad as about 10 cm-1• SATO (1984) had pointed out that the FWHM varies with the mode of the diamond synthesis. In fact, the FWHM of the 1332 cm- 1 Raman peak of shock-produced diamonds (e.g., DECARLI and JAMIESON, 1961) is enhanced from 10 to 120 cm-1, that of diamonds synthesized by chemical vapor deposition (CVD) (e.g., DERJAGUIN et al., 1968) is from 3 to 25 cm-1, and that by static high pressure (e.g., BUNDY, 1963) is from 2 to 3 cm-1 (MIYAMOTO et al., 1993; SATO, 1984). On the other hand, HEYMANN (1989) measured the Raman spectrum of a diamond in the Canyon Diablo iron meteorite and showed that the FWHM was 7±2 cm-1, which is within the range for CVD diamonds. Since the majority of meteorite researchers have concluded that diamonds in Canyon Diablo formed by impact shock when the meteorite struck the Earth (e.g., HEYMANN et al., 1966), then HEYMANN (1989) cautioned that the Raman evidence for the CVD origin of ureilite diamond may be much less firm than stated by MIYAMOTO et al. (1988). Therefore, in the present study Raman spectra of diamonds in Canyon Diablo were remeasured to confirm the result reported by HEYMANN (1989). In addition, Raman measurements on meteoritic diamonds may distinguish be­tween CVD and shock-produced diamonds and further the Raman signature can be used as an additional quantitative indicator of shock pressure in iron meteorite fragments. 171 172 M. MIYAMOTO 2. Sample and Experiments Raman spectra were measured for diamonds in an inclusion of the Canyon Diablo sample, which was kindly supplied by Robert A. HAAG - Meteorites. The inclusion of about 0.5 cm in diameter, which consists mainly of graphite and diamond, lies within a rough slice (3.5 cmx2.5 cmx0.3 cm in size) of the Canyon Diab lo iron meteorite. Dia­monds, which are from about 1 µm to a few tens of µm in size, are found among graphite grains in the inclusion. Raman spectra were measured with a JASCO micro Raman spectrometer with a triple monochromator (3x60 cm). The 488 nm line of an argon laser was focused to an area of about 1 µm across on the sample surface through a microscope (backscattering (180°) geometry). The laser power was about 3 mW on the surface of the sample. The spectra were accumulated for 10 min to enhance the signal-to-noise ratio by using a multichannel detector composed of photodiode array. The wavenumber position and the full width at half maximum (FWHM) of the Raman peak were determined by carrying out a Lorentzian fitting of the spectrum. The wavenumber position of the Raman peak was calibrated by using both the 1293. 952 cm- 1 and 1343.517 cm- 1 emission lines in Raman shift of a Ne lamp. Spectral slit width was about 2 cm- 1 and the variation in room temperature was within ±5 °C. Besides the Raman spectroscopic investigation, the inclusion and some diamonds were observed also by using a scanning electron microscope (SEM, JEOL 840A) equipped with an energy dispersive spectrometer (EDS) combined with a wavelength dispersive spectrometer (WDS) using the utilities of the Kevex Super 8000 system. Carbon was detected by using the WDS system. 3. Results and Discussion Raman spectra were measured on the cores of diamond grains in the inclusion of the Canyon Diablo sample. Figure 1 shows the Raman spectrum of a diamond in Can-Canyon Diablo 1600 1500 1 400 1300 Raman Shift, cm-1 1200 Fig. 1. The Raman spectrum of a diamond in the Canyon Diablo iron meteorite. The peak position is 1329 cm- 1 and the FWHM (full width at half maximum) is 50 cm- 1• 10 A 8 � 6 4 2 Raman Spectroscopy of Diamond in Canyon Diablo 10 Canyon Diablo B Av.= 1326 cm-1 8 o =3cm·1 gs �4 u.. 2 Canyon Diablo Av.= 66cm-1 o=22 cm-1 173 0 1334 1330 1326 1322 1318 0 20 40 60 80 100 120 Raman Shift, cm ·1 FWHM, cm-1 Fig. 2. Distributions of the wavenumber position ( a) and FWHM (b) of a Raman peak near 1332 cm- 1 of diamonds in the Canyon Diablo iron meteorite. An arrow indicates the wavenumber position of a diamond from South Africa ( 1332.13 cm-1, MIYAMOTO and 0HSUMI, 1995). yon Diablo. Figure 2a shows the distribution of the wavenumber position of a Raman peak near 1332 cm- 1 of diamond (SouN and RAMDAS, 1970). The peak positions are widely distributed from 1333 to 1318 cm-1 (The average is 1326±3 cm- 1). The FWHM of the Raman peak of the Canyon Diab lo diamonds (Fig. 2b) is also very large, ranging from 25 to 117 cm- 1 with an average of 66±2 cm- 1• The FWHM of the Raman peak against the wavenumber position shows no correla­tion between the FWHM and wavenumber position (Fig. 3a). Each solid circle in Fig. 120 • 120 • Canyon Diablo Canyon Diablo 100 100 • • • '7E 80 • • • ';'E 80 • ,.. u ':i ... : • :i •• • • ::r: 60 • i 60 • 3: • • • • • u.. • ' • • 0 40 • 40 • • A A • • +� • 0 20 20 A B 0 0 1335 1330 1325 1320 1315 1335 1330 1325 1320 Raman Shift, cm-1 Raman Shift, cm-1 Fig. 3. Plot of the wavenumber position versus FWHM of the Raman peak near 1332 cm- 1 in the Canyon Diablo iron meteorite. (a) Diamonds shown in Fig. 2. Each solid circle stands for the value of the core of an individual diamond grain (b) Some relatively large diamond grains. Each symbol stands for the values within the same grain. 1315 174 120 100 '7E 80 () � ::i::: 60 :s: LL 40 20 0 1335 M. MIYAMOTO 120 • • Du Pont Y790981 • 100 • • •• • '7E 80 () • • • • :ii: • • • J: 60 • :s: • LL • • • • • • 40 • - • .: . • • •• • ., • • • • •• 20 • •• • • • • ..,, 0 1330 1325 1320 1315 1335 1330 1325 1320 Raman Shift, cm-1 Raman Shift, cm-1 Fig. 4. Plot of the wavenumber position versus FWHM of a Raman peak near 1332 cm- 1• Data are from MIYAMOTO et al. (1993). (a) Diamonds synthesized by shock-induced high pressure (made by Du Pont de Nemours, E. I. & Co.). (b) Diamonds in the Yamato-790981 ureilite. B 1315 3a corresponds to one spot in one individual grain of diamond. Figure 3b shows the variation in the wavenumber position and FWHM of the Raman peak within each grain. Several measurements were performed for some large grains at various locations, be­cause the laser beam for the Raman measurement is about 1 µm across which is smaller compared with the sizes of the measured grains. The wavenumber position and FWHM are varied in different locations within each grain. This result implies that the diamond grains may be polycrystalline. The ranges of both the wavenumber position and FWHM of the Raman peak (Fig. 3a) are similar to those of diamonds synthesized by shock­induced high pressure (Fig. 4a) (MIYAMOTO et al., 1993). Consequently the present Raman measurements suggest that the Canyon Diablo diamonds formed by impact shock. HEYMANN (1989) reported that a Canyon Diablo diamond shows a Raman peak at 1332 cm- 1 having a narrow FWHM (7±2 cm- 1). However, no diamond grains in the inclusion studied showed as narrow FWHM as reported by HEYMANN (1989) (Fig. 2b). This is probably caused by sample heterogeneity. Crystallinity of diamond may be dif­ferent in individual inclusions in Canyon Diablo, because the degree and duration of shock pressure depend on the location of Canyon Diablo. Further Raman measurements will be needed for different inclusions. The SEM/EDS/WDS study of typical diamond grains in Canyon Diablo confirmed that the major element is carbon, although further study is needed for the detection of minor elements. Some diamond grains showed weak fluorescence under electron beam irradiation. The FWHM and wavenumber position of a Raman peak are dependent on some factors such as the crystallite size, lattice stress, crystal-structural disorder, the presence of impurities, and sample temperature (e.g., MIYAMOTO et al., 1993). It has been re-Raman Spectroscopy of Diamond in Canyon Diablo 175 ported that both the FWHM and wavenumber position of a Raman peak vary with the crystallite size (e.g., loBAL et al., 1981; YOSHIKAWA et al., 1993). For example, the Raman peak of diamond powders was found to become broader, weaker, and more asymmetric with decreasing particle size (YosHIKAWA et al., 1993). The calculations based on the phonon confinement model (e.g., RICHTER et al., 1981) also predict that the wavenumber position shifts toward a smaller wavenumber ( downshift) and the FWHM becomes wider with decreasing particle size. The calculated Raman spectrum of diamond of about 5 nm in size shows a broad peak with the downshift of 13 cm- 1 and FWHM of about 38 cm-1 (YosHIKAWA et al., 1993). Similar downshift and broadening due to small crystallite are observed for Si (loBAL et al., 1981). The threshold of the particle size for this effect is apparently in the range of 10-100 nm, although it varies with different materials (W. B. WHITE, personal communication, 1997). There is, however, no clear correlation between the FWHM and wavenumber posi­tion of the Raman peak of Canyon Diablo diamonds (Fig. 3a). A similar result was obtained for shock-produced diamonds (Fig. 4a) (MIYAMOTO et al., 1993). If the down­shift and broadening are caused by the small crystallite size, the downshift should show a positive correlation with the broadening. In addition, no clear asymmetry of the Raman peak of Canyon Diablo diamond was observed (Fig. 1). These results imply that the changes in the FWHM and wavenumber position found in Canyon Diablo diamond can­not solely depend on the crystallite size. The shift of a Raman peak caused by lattice stress can go to both higher and lower wavenumbers depending of whether the sample is under tension or under compression. This is well documented in KNIGHT and WHITE (1989). Crystal-structure disorder usually produces a line broadening rather than the peak shift, although "disorder" is one of the glib terms which is rarely defined precisely in terms of the defect structure of the "disordered" crystal (W. B. WHITE, personal commu­nication, 1997). The downshift of the Raman peak of Canyon Diablo diamond may be due to the presence of lonsdaleite (hexagonal diamond) (e.g., KNIGHT and WHITE, 1989; MIYAMOTO et al., 1993), because it has been reported that Canyon Diablo diamond and shock-pro­duced diamond contain lonsdaleite by X-ray powder diffraction study (e.g., FRONDEL and M ARVIN, 1967; HANNEMAN et al., 1967; BUNDY and KASPER, 1967). In fact, KNIGHT et al. (1991) reported that the original lonsdaleite was mixed with a lot of graphitic mate­rial, while one grain gave a sharp Raman band at 1318 cm- 1 • Nitrogen- or boron-doped diamonds show the peak shift of no more than 1-2 cm-1 (ANDREYEV et al., 1992). The downshift and broadening of a Raman peak are also caused by elevating sample temperature under a laser beam. Although diamond in Canyon Diablo is embedded in graphitic materials and is not an isolated grain, a rise in sample temperature is unavoid­able. ANDREYEV et al. (1992) and ZHAO et al. (1997) reported that the observed down­shifts of 2-10 cm- 1 for diamond powders were caused by heating from 200 to S00°C by a laser beam. Although the Raman spectra of several diamonds in Canyon Diablo were measured by reducing the laser power to 1.5 mW, no significant peak shift was detected. Asymmetry of a Raman peak due to heating as was reported by ANDREYEV et al. (1992) 176 M. MIYAMOTO could not be found (Fig. 1). The FWHM of the Raman peak of diamonds in the ALHA 77257, Yamato (Y-)-790981, and Y-791538 ureilites is significantly narrower than that of diamonds in this inclusion of Canyon Diablo (Fig. 3a) (MIYAMOTO et al., 1988, 1993). For example, Fig. 4b shows the ranges of both the wavenumber position and FWHM of the Raman peak of the Y-790981 ureilite (MIYAMOTO et al., 1993). Although the range of the FWHM of ureilite diamonds is closer to that of CVD diamonds than to that of shock-produced diamonds (MIYAMOTO et al., 1993), the CVD origin of ureilite diamond cannot be made solely by the Raman data. Coincidence of the FWHM of the Raman peak does not necessarily mean coincidence of their occurrence (HEYMANN, 1989) because the FWHM of the Raman peak depends on many complex factors as was discussed. The CVD origin of ureilite diamond should be further explored. Acknowledgments The author thanks Robert A. HAAG - Meteorites for the Canyon Diablo sample, Mr. 0. TAcHIKAWA for help in microanalyses by SEM/EDS/WDS, and Drs. D. HEYMANN and J. D. PASTERIS for critical reading of the manuscript. He also thanks Prof. W. B. WHITE for helpful suggestions that greatly improved the manuscript. References ANDREYEV, V.D., NACHALNAYA, T.A. and GABRUSENOK, E.V. (1992): The peculiarities of Raman scattering of diamond micron powders. J. Superhard Mater., 15, 9-16. BUNDY, F.P. (1963): Direct conversion of graphite to diamond in static pressure apparatus. J. Chem. Phys., 38, 631-643. BUNDY, F.P. and KASPER, J.S. (1967): Hexagonal diamond - A new form of carbon. J. Chem Phys., 46, 3437-3446. DECARLI, P.S. and JAMIESON, J.C. (1961): The formation of diamond by explosive shock. Science, 133, 1821-1822. DERJAGUIN, B.V., FEDOSEEV, D.V., LuKYANOVICH, V.M., SPITSYN, B.V., RYABOV, V.A. and LAVREUTYEV, A.V. (1968): Filamentary diamond crystals. J. Cryst. Growth, 2, 380-384. FRONDEL, C. and MARVIN, U.B. (1967): Lonsdaleite, a hexagonal polymorph of diamond. Nature, 214, 587-589. HANNEMAN, R.E., STRONG, H.M. and BUNDY, F.P. (1967): Hexagonal diamonds in meteorites: Implications. Science, 155, 995-997. HEYMANN, D. (1989): ls the width of the Raman line of diamond diagnostic for the origin of diamonds in meteorites? Comment on "Raman spectra of ureilite diamonds" by M. MIYAMOTO, Y. NISHIMURA, J. MATSUDA and K. lTo. Geochim. Cosmochim. Acta, 53, 3059-3060. HEYMANN, D., LIPSCHUTZ, M.E., NIELSON, B. and ANDERS, E. (1966): Canyon Diablo meteorite: metallographic and mass-spectrometric study of 56 fragments. J. Geophys. Res., 71, 619-641. IQBAL, Z., VEPREK, S., WEBB, A.P. and CAPPEZUTO, P. (1981): Raman scattering from small particle size poly­crystalline silicon. Solid State Commun., 37, 993-996. KNIGHT, D.S. and WHITE, W.B. (1989): Characterization of diamond films by Raman spectroscopy. Mater. Res., 4, 385-393. KNIGHT, D.S., PILIONE, L. and WHITE, W.B. (1991): Surface enhanced Raman spectroscopy of diamond and related carbon materials. Proc. 2nd International Conf. on New Diamond Science and Technology, ed. by R. MESSIER et al. P ittsburgh, Materials Research Soc., 753-758, MIYAMOTO, M. and 0HSUMI, K. (1995): Micro Raman spectroscopy of olivines in L6 chondrites: Evaluation of Raman Spectroscopy of Diamond in Canyon Diablo 177 the degree of shock. Geophys. Res. Lett., 22, 437-440. MIYAMOTO, M., MATSUDA, J. and ITO, K. (1988): Raman spectroscopy of diamond in ureilite and implication for the origin of diamond. Geophys. Res. Lett., 15, 1445-1448. MIYAMOTO, M., TAKASE, T. and MITSUDA, Y. (1993): Raman spectra of various diamonds. Mineral. J., 16, 246-257. RICHTER, H., WANG, Z.P. and LEY, L. (1981): The one phonon Raman spectrum in microcrystalline silicon. Solid State Commun., 39, 625-629. SATO, Y. (1984): Characterization of diamond by Raman spectroscopy. Research on Diamond. Res. Rep. Natl Inst. Res. Inorg. Mater., 39, 50-56. SouN, S.A. and RAMDAS, A.K. (1970): Raman spectrum of diamond. Phys. Rev., Bl, 1687-1698. YosHIKAWA, M., MoRI, Y., MAEGAWA, M., KATAGIRI, G., ISHIDA, H. and lsHITANI, A. (1993): Raman scattering from diamond particles. Appl. Phys. Lett., 62, 3114-3116. ZHAO, X.-N., CHERIAN, K.A., RoY, R. and WHITE, W.B. (1997): Significant shifts of 1332 cm- 1 diamond Raman line caused by laser power and particle size. J. Mater. Res. (in press). (Received August 6, 1997; Revised manuscript accepted October 24, 1997) 

Micro raman spectroscopy of diamonds in the Canyon Diablo iron meteorite: Implication for shock origin

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Micro raman spectroscopy of diamonds in the Canyon Diablo iron meteorite: Implication for shock origin

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