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Infrared-laser induced production of silicon coating via reaction of silane with trifluoroacetic acid
Infiored fhys. Vol. 30. No. 4. pp. 355-357.1990 Printal in GreatBritain.All @IS reserved
0020-0891/9053.00+ 0.00 Copyright0 1990PergamonPresspk
INFRARED-LASER INDUCED PRODUCTION OF SILICON COATING VIA REACTION OF SILANE WITH TRIFLUOROACETIC ACID J. POLA,’ Z. BASTL~ and J. TL~SKAL) ‘Institute of Chemical Process Fundamentals, Czechoslovak Academy of Sciences, CS 165 02 Prague bSuchdo1, Czechoslovakia, ‘The HeyrovskL Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, CS 182 23 Prague 8, Czechoslovakia and ‘Institute of Inorganic Chemistry, Czechoslovak Academy of Sciences, CS 250 68 Rei near Prague, Czechoslovakia (Received 20 October
1989)
Abstract-Irradition of gaseous mixtures of silane and trifluoroacetic acid by TEA CO, laser results in the formation of gaseous products and solid deposits that are inferred, on the basis of IR and ESCA analysis, to consist of Si, C, 0 and F atoms.
INTRODUCTION
Interaction of the IR laser radiation with gaseous mixtures of silane currently attracts attentionud) due to the possibilities of induction of novel chemical reactions and preparation of new solid materials. This paper is concerned with the interaction of TEA CO2 laser radiation with a gaseous mixture of silane, SiH, and trifluoroacetic acid, CF3COzH and is a continuation of our previous work@*@ to produce novel silicon-containing solid substances.
EXPERIMENTAL
The grating-tuned TEA CO2 laser (P. Hilendarski Plovdiv University, 1300 M model) used in the experiments was operated on the P(20) line of the 10.6 pm band at 944.19 cm-’ at the repetition rate of 1 Hz. The beam wavelength was verified with a model 16-A spectrum analyser (Optical Eng. Co.) and its energy (2 J) was measured with a laser-energy pyroceramic sensor (Charles University, ml-l JU model). The beam was square, w 1.3 cm on each side and was focused by a NaCl lens (focal length 5 cm) located close to the entrance window of a cylindrical (3 cm inner diameter, 10 cm long) glass cell, equipped with NaCl windows and a valve. The cell contained a mixture of silane and trifluoroacetic acid that were admitted from a standard vacuum-line. A typical temporal profile of the pulse, as measured with a Roffin photon-drag detector, consisted of a 150 ns (FWHM) peak followed by a tail of about 1 ps when the laser was operated with 4 : 8 : 12 CO1 : N, : He atmospheric gas mixture. Infrared spectra before and after irradiation were recorded with a Specord IR 75 model (Zeiss) IR spectrometer. The X-ray photoelectron spectra of the deposit were measured on a VG ESCA 3 MK II spectrometer, whilst scanning-electron-microscopy measurements were performed on a Tesla BS microscope as reported previously. (6)Silane (Lachema) and trifluoroacetic acid (Fluka), both >99.5% pure, were commercial samples, the latter distilled prior to use.
RESULTS
AND
DISCUSSION
Irradiation of silane-trifluoroacetic acid (both 10-20 torr) mixtures is accompanied by a violet luminiscence observed after each pulse and results in the depletion of both initial compounds, the formation of gaseous HSiF,, SiF,, COF,, CO, CH, and CIH, compounds, and the deposition of a white solid on both windows and the surface of the cell (Fig. 1). It is conceivable that the P(20) line of the 10.6 pm band of the laser coinciding with the vq mode of silane induces dissociation of 355
356
J. Pot.4 ef al.
1
‘ki-C
*i
I 1000
I 3000
2000
4
$,Cli?
Fig. I. Typical IR spectra of the initial CF,COIW-SiH, (both 15 torr) mixture (a), after the irradiation with 100 pulses (b), and of the solid deposit in vacuum (c).
silane into molecular hydrogen and reactive silylene SiH2 [see e.g. Refs (7, g)], which can insert into the 0-H bond of trifhtoroacetic acid. The product of this reaction, CF,CQSiH, is known to be unstabIe’9’ and cannot be a final product, since its characteristic IR absorptions [I 167, 1193, 2214 and 2226 cm-‘--Ref. (lo)] are not observed in irradiated mixtures. This compound can decompose
Fig. 2. SEM of the deposit.
IR-laser induced production of silicon coating
351
in a way similar to that of trifluoroacetic acid(“) resulting in H$iF and ‘CF, CO; species, the latter decomposing into COF, and CO. The presence of these compounds supports this assumption. There should be other radical processes involved as well. Infrared spectra of the deposit show absorption in the region of Asia, vM, v&H and vc_r vibrations and the occurrence of methane and acetylene together with tetrafluorosilane are compatible with scrambling and radical reactions resulting in a complex product containing Si, C, 0 and F atoms. The X-ray photoelectron spectrum of the deposit revealed its stoichiometry to be Si,,CO ,,4F ,,.,. The IR spectral data are consistent with a siloxane structure with C=O groupings and hydrogens attached to the only silicon. The absorption bands belonging to vc_Fand vG+,vibrations deplete when the deposit is exposed to air and evacuated thereafter. This observation shows that CF moiety is apparently a part of an acyloxy group bonded to silicon. Scanning electron microscopy of the solid shows that it consists of agglomerates (Fig. 2). There is vital interest in the synthesis and applications of fluorosilicones mainly because of their applications in high performance coatings.(“) The production of highly fluorinated silicones causes a lot of difficulties and the fact that the solid reported here shows excellent adhesion to glass and NaCl surfaces indicates that the laser-induced process might serve as a potential technique for the production of coatings for a number of polar surfaces. REFERENCES 1. J. Blazejowski and F. W. Lampe, J. Photochem. 20, 9 (1982). 2. P. Zhu, M. Piserchio and F. W. Lampe, J. Phys. Chem. 89, 5344 (1985). 3. Y. Koga, R. M. Serino, R. Chen and P. M. Keehn, J. Phys. Chem. 91, 298 (1987). 4. R. Alexandrescu, J. Morjan, C. Grigoriu, N. N. Michailescu, Z. Bastl, J. Tliiskal, R. Mayer and J. Pola, Appl. Phys. A46, 768 (1988). 5. S. Simeonov and J. Pola, Spectrochim. Acta In Press. 6. Z. PapouSkova, J. Pola, Z. Bastl and J. Tlaskal, J. macromof. Sci. Chem. In press. 7. T. F. Deutsch, J. Chem. Phys. 70, 1187 (1979). 8. P. A. Longeway and F. W. Lampe, J. Am. them. Sot. 103, 6813 (1981). 9. E. A. V. Ebsworth and J. C. Thompson, J. them Sot. inorg. Chem. (A), 69 (1967). 10. A. G. Robiette and J. C. Thompson, Spectrochim. ACM 21, 2023 (1965). 11. J. Pola, CON. Czech. Chem. Commua. 46, 2854 (1981). 12. B. Boutevin and Y. Pietrasanta, Prog. Org. Coatings 13, 297 (1985).
0020-0891/9053.00+ 0.00 Copyright0 1990PergamonPresspk
INFRARED-LASER INDUCED PRODUCTION OF SILICON COATING VIA REACTION OF SILANE WITH TRIFLUOROACETIC ACID J. POLA,’ Z. BASTL~ and J. TL~SKAL) ‘Institute of Chemical Process Fundamentals, Czechoslovak Academy of Sciences, CS 165 02 Prague bSuchdo1, Czechoslovakia, ‘The HeyrovskL Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, CS 182 23 Prague 8, Czechoslovakia and ‘Institute of Inorganic Chemistry, Czechoslovak Academy of Sciences, CS 250 68 Rei near Prague, Czechoslovakia (Received 20 October
1989)
Abstract-Irradition of gaseous mixtures of silane and trifluoroacetic acid by TEA CO, laser results in the formation of gaseous products and solid deposits that are inferred, on the basis of IR and ESCA analysis, to consist of Si, C, 0 and F atoms.
INTRODUCTION
Interaction of the IR laser radiation with gaseous mixtures of silane currently attracts attentionud) due to the possibilities of induction of novel chemical reactions and preparation of new solid materials. This paper is concerned with the interaction of TEA CO2 laser radiation with a gaseous mixture of silane, SiH, and trifluoroacetic acid, CF3COzH and is a continuation of our previous work@*@ to produce novel silicon-containing solid substances.
EXPERIMENTAL
The grating-tuned TEA CO2 laser (P. Hilendarski Plovdiv University, 1300 M model) used in the experiments was operated on the P(20) line of the 10.6 pm band at 944.19 cm-’ at the repetition rate of 1 Hz. The beam wavelength was verified with a model 16-A spectrum analyser (Optical Eng. Co.) and its energy (2 J) was measured with a laser-energy pyroceramic sensor (Charles University, ml-l JU model). The beam was square, w 1.3 cm on each side and was focused by a NaCl lens (focal length 5 cm) located close to the entrance window of a cylindrical (3 cm inner diameter, 10 cm long) glass cell, equipped with NaCl windows and a valve. The cell contained a mixture of silane and trifluoroacetic acid that were admitted from a standard vacuum-line. A typical temporal profile of the pulse, as measured with a Roffin photon-drag detector, consisted of a 150 ns (FWHM) peak followed by a tail of about 1 ps when the laser was operated with 4 : 8 : 12 CO1 : N, : He atmospheric gas mixture. Infrared spectra before and after irradiation were recorded with a Specord IR 75 model (Zeiss) IR spectrometer. The X-ray photoelectron spectra of the deposit were measured on a VG ESCA 3 MK II spectrometer, whilst scanning-electron-microscopy measurements were performed on a Tesla BS microscope as reported previously. (6)Silane (Lachema) and trifluoroacetic acid (Fluka), both >99.5% pure, were commercial samples, the latter distilled prior to use.
RESULTS
AND
DISCUSSION
Irradiation of silane-trifluoroacetic acid (both 10-20 torr) mixtures is accompanied by a violet luminiscence observed after each pulse and results in the depletion of both initial compounds, the formation of gaseous HSiF,, SiF,, COF,, CO, CH, and CIH, compounds, and the deposition of a white solid on both windows and the surface of the cell (Fig. 1). It is conceivable that the P(20) line of the 10.6 pm band of the laser coinciding with the vq mode of silane induces dissociation of 355
356
J. Pot.4 ef al.
1
‘ki-C
*i
I 1000
I 3000
2000
4
$,Cli?
Fig. I. Typical IR spectra of the initial CF,COIW-SiH, (both 15 torr) mixture (a), after the irradiation with 100 pulses (b), and of the solid deposit in vacuum (c).
silane into molecular hydrogen and reactive silylene SiH2 [see e.g. Refs (7, g)], which can insert into the 0-H bond of trifhtoroacetic acid. The product of this reaction, CF,CQSiH, is known to be unstabIe’9’ and cannot be a final product, since its characteristic IR absorptions [I 167, 1193, 2214 and 2226 cm-‘--Ref. (lo)] are not observed in irradiated mixtures. This compound can decompose
Fig. 2. SEM of the deposit.
IR-laser induced production of silicon coating
351
in a way similar to that of trifluoroacetic acid(“) resulting in H$iF and ‘CF, CO; species, the latter decomposing into COF, and CO. The presence of these compounds supports this assumption. There should be other radical processes involved as well. Infrared spectra of the deposit show absorption in the region of Asia, vM, v&H and vc_r vibrations and the occurrence of methane and acetylene together with tetrafluorosilane are compatible with scrambling and radical reactions resulting in a complex product containing Si, C, 0 and F atoms. The X-ray photoelectron spectrum of the deposit revealed its stoichiometry to be Si,,CO ,,4F ,,.,. The IR spectral data are consistent with a siloxane structure with C=O groupings and hydrogens attached to the only silicon. The absorption bands belonging to vc_Fand vG+,vibrations deplete when the deposit is exposed to air and evacuated thereafter. This observation shows that CF moiety is apparently a part of an acyloxy group bonded to silicon. Scanning electron microscopy of the solid shows that it consists of agglomerates (Fig. 2). There is vital interest in the synthesis and applications of fluorosilicones mainly because of their applications in high performance coatings.(“) The production of highly fluorinated silicones causes a lot of difficulties and the fact that the solid reported here shows excellent adhesion to glass and NaCl surfaces indicates that the laser-induced process might serve as a potential technique for the production of coatings for a number of polar surfaces. REFERENCES 1. J. Blazejowski and F. W. Lampe, J. Photochem. 20, 9 (1982). 2. P. Zhu, M. Piserchio and F. W. Lampe, J. Phys. Chem. 89, 5344 (1985). 3. Y. Koga, R. M. Serino, R. Chen and P. M. Keehn, J. Phys. Chem. 91, 298 (1987). 4. R. Alexandrescu, J. Morjan, C. Grigoriu, N. N. Michailescu, Z. Bastl, J. Tliiskal, R. Mayer and J. Pola, Appl. Phys. A46, 768 (1988). 5. S. Simeonov and J. Pola, Spectrochim. Acta In Press. 6. Z. PapouSkova, J. Pola, Z. Bastl and J. Tlaskal, J. macromof. Sci. Chem. In press. 7. T. F. Deutsch, J. Chem. Phys. 70, 1187 (1979). 8. P. A. Longeway and F. W. Lampe, J. Am. them. Sot. 103, 6813 (1981). 9. E. A. V. Ebsworth and J. C. Thompson, J. them Sot. inorg. Chem. (A), 69 (1967). 10. A. G. Robiette and J. C. Thompson, Spectrochim. ACM 21, 2023 (1965). 11. J. Pola, CON. Czech. Chem. Commua. 46, 2854 (1981). 12. B. Boutevin and Y. Pietrasanta, Prog. Org. Coatings 13, 297 (1985).