- Email: [email protected]
Cold remote nitrogen plasma effects on pulsed laser deposited CNX films characteristics
Carbon Vol. 36, No. 5-6, pp. 785-789, 1998 8 1998ElsevierScienceLtd Printed in Great Britain.All rights reserved 0008-6223/98 519.00+ 0.00
PII: !3000%6223(98)00005-0
COLD REMOTE NITROGEN PLASMA EFFECTS ON PULSED LASER DEPOSITED CNx FILMS CHARACTERISTICS C. JAMA and P. GOUDMAND* Laboratoire de Physicochimie de I’Energktique et des Plasmas (LPCEP) EA MENESR 1761, Universitk des Sciences et Technologies de Lille, 59655 Villeneuve d’Ascq, cedex, France (Received 30 October 1997; accepted in revised form 9 December
1997)
Abstract-Carbon nitride films were deposited by ablation of carbon molecular fragments from a graphite targets on a silicon substrate after few pulses of a localized transversely excited atmospheric pressure CO2 laser. Deposition media were either a non excited nitrogen flow or cold remote plasma of nitrogen. Fourier transform infrared spectra of the deposited films show a very efficient nitrogen fixation with C-N bands characteristic of tetrahedral carbon. The effect of the distance of deposition zone from the discharge is also discussed. 0 1998 Elsevier Science Ltd. All rights reserved. Key Word-A.
Carbon nitride, B. Laser ablation, B. Plasma deposition, D. Surface properties, C. XPS.
on the target at an incidence angle of 45”. The substrates were placed at a distance of 3 cm from the graphite target. CN, films were deposited during 5 minutes on a silicon substrate by laser ablation from a graphite target under (NENF) or (CRNP) conditions. Nitrogen flow was excited in an electrodeless discharge by means of a microwave Sairem generator 2450 MHz. The transmitted power was ca 800 W. The discharge was produced in a quartz tube, and, by a continuous pumping, the plasma was led to the reaction chamber located at a fixed distance from the discharge equal to 0.9 m.
1. INTRODUCTION
The possible existence of a class of carbon nitrides isomorphic to /I-S&N, was suggested some years ago by Liu and Cohen [l]. The experimental quest to realize this novel compound has resulted in several publications mainly in the few last years [2-41. Most of these report the deposition of amorphous or partly crystalline CN, (~~0.5). However, the mechanical properties of these films have proven to be very interesting for surface engineering [5]. CN, films deposited on Si substrate held at temperatures T, between 150 and 600°C are extremely elastic and hard [6]. In this work CN, films were deposited a by laser ablation of carbon atoms from a graphite target under non-excited nitrogen flow (NENF) or under cold remote nitrogen plasma (CRNP) conditions. Sputtered carbon fragments combined with nitrogen reactive species lead to the formation of a film on the substrate. The aim of this study is to establish if there is a relationship between the CRNP reactive species, such as nitrogen atoms N(4S), and films composition and structure. Characterization of carbon nitride films by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy are also presented.
2.2 Film characterization The films, deposited at a pressure of 500 Pa, were characterized by FTIR (Perkin-Elmer 1600 spectrometer) spectroscopy. The thickness measurements were measured with a profilometer Alpha-step instrument. The surface composition of the deposited films was characterized by XPS (LHS 10 spectrometer). The Al Ka X-ray source was operated at 13 kV and 20 mA current emission. The pressure during analysis was < 1.3 x 10m6Pa. The peaks were curve-resolved assuming Gaussian profiles. The relative atomic stoichiometry N/C and O/C, denoted X, and X0 respectively, were determined according to the ratio [7]:
2. EXPERIMENTAL
2.1 Film preparation A schematic diagram of the experimental set up is presented in Fig. 1. The pulsed transversely excited atmospheric (TEA) CO* laser (203 Lumonics) parameters used were the wavelength 1= 10.56 pm and the pulse duration of 50 nseconds and repetition rate of 1 Hz. The energy per laser irradiation pulse was 10 J, and the laser beam was properly focused
nA -nB
_-
IAi&j
IBjKAi
where IAitBjj is the i(j) photopeak intensity of the element A(B) and KAitBj) is the result term between the cross section of the i(j) core level orbital, the inelastic mean free path and the transmission factor of the analyzer, both of latter being kinetic energydependent. The efficiency of the electron detector was considered to be constant.
*Corresponding author. Tel: 33(O) 320 43 4455; Fax: 33(O) 320 43 4158; e-mail: [email protected] 785
786
C. JAMA and P. GOUIIMANI~
To pump
Fig.
I. Experimental
3. RESULTS
3.1 Deposition rule Figure 2 presents results for films obtained under NENF. It shows for two nitrogen pressures 100 and 500 Pa, the film thickness as a function of the number of the laser irradiation repetition, denoted IV,,. For the two pressures, film thickness increases with Ni,. The deposition rate (film thickness) decreases when nitrogen pressure increased for a given Ni, value. By increasing nitrogen pressure, the gas velocity increases, therefore the energetic particles are evacuated more efficiently giving a low deposition rate.
3.2 Infruredspecfroscopq The infrared spectra of amorphous carbon are typically featureless. However, nitrogenated carbon films spectra present numerous bands such as C-N, C=N, C=C, CN, C-C, CH, or NH, [8- II]. The major lines of carbon nitrides films deposited by plasma decomposition of hydrocarbons and N, were attributed by Han and Feldman [8] as follows: 2190cm-’ as a C=N stretching mode, 1630cm-’ as C=C stretching mode, CH2 and NH, vibrational
1200
800
400
o0
100
200
Nir 300
Fig. 2. Film thickness of the deposit versus the laser irradiation number (A’,,) in NENF.
setup for CN, depositicn.
modes were also detected. Bands at 1370 and 1570 cm I detected for nitrogen-doped amorphous carbon were attributed to the sp2 graphitic bonds by Kaufman et ul. [9] and Kumar and Tansley [ 1I]. For CN, films deposited by pulsed laser, the bands at: 1500&1750 and 1200~1450cm~’ were identified as C-N and C-N, respectively, by Zhao et al. [IO]. Figure 3 presents FTIR spectra. For NENF films, a broad band in the region of lOOOG1600 cm ’ is observed, with an apparent maximum at 1570 cm- ‘, which could be due to C=N vibrational mode [lo]. A peak at 2100&2300 cm- ‘, due to C=N stretching mode, is also observed. When a CRNP plasma is used, the band at 1570 cm-’ shifts by 30 cm-’ towards higher wave numbers. The band in the region of 1000~1600 cm-’ shows a broader feature with no apparent maximum, which may be related to the diamondlike carbon films structure [ 121. The 1250- 1400 cm-i band could correspond to the sp” carbon single bonded to nitrogen C-N in tetrahedral environment. A complete disappearance of the band 2lOOG2300 cm- * is observed. 3.3 XPS spectroscopy
3.3.1 E&et of pressure_ Fig. 4 shows the evolution of films composition as a function of the pressure for films obtained under NENF or under CRNP plasma. It shows that nitrogen composition ratio relative to carbon N/C (X,) incorporated in the films increases with increasing nitrogen pressure for the two cases. The film with the lowest X, value (X, =0.02) is obtained under a pressure of 5 Pa which corresponds to our limit vacuum pressure. XPS analyses show that nitrogen incorporation in the films varied with the deposition conditions. Nitrogen film composition values shown in Fig. 4 give evidence that higher X, values are obtained for films deposited under CRNP conditions. At a pressure of 1000 Pa, nitrogen atomic ratio X,=0.31 is obtained with the NENF whereas, XN increased to 0.39 with CRNP plasma. Nitrogen fixation is then enhanced when CRNP is used. Figure 5 shows the
Cold remote nitrogen plasma effects on CN, films
4000
I .3500
I 3000
r 2500
, 2000
787
I
500 I
I
1000
1500
Fig. 3. FTIR transmission spectra of deposited CNx films at 500 Pa: (a) NENF and (b) in CRNP.
Pressure (Pa) 0
500
1000
Fig. 4. X, atomic ratio as a function of the pressure: (a) NENF; (b) in CRNP. 2.90
C 1s photoelectron peak of the films deposited under CRNP or NENF. When films are deposited under CRNP, important changes are noticed in the spectra. The C Is feature shows an increase of the high binding energy components intensity. This is consistent with the fact that a higher nitrogen composition is obtained for films deposited under CRNP and could also be due to the presence of new nitrogenated chemical environment. The increase of nitrogen composition for films obtained under CRNP can be explain by the fact that nitrogen incorporation into the film takes place during and after the ablation plume, while when films are deposited under NENF, the nitrogen incorporation takes place only in the ablation plume created by the breakdown. 3.4 Efect of the distance from the discharge In order to study the effect of the distance (d) between discharge and the deposition zone, carbon
2a2
2.94 Binding
286
28.3
290
292
Energy (ev)
Fig. 5. C Is spectra of deposited CN, films at 500 Pa under: (a) CRNP and (b) NENF.
nitrides films were deposited, under a pressure of 1000 Pa, in two distinct zones at (d=0.4 and d= 0.9 m). For d= 0.4 m, the substrate is subjected to the short-lived afterglow, while for d=0.9 m it is subjected to the far afterglow. For films deposited at d=0.4 m, X, value was 0.47, whereas for d=0.9 m, it decreased to 0.39. This result can be explained both by the presence of higher energetic species in the short-lived afterglow atom concentration.
and by a higher
nitrogen
3.4.1 Films structure. Spectra from the films deposited under CRNP or NENF reveal, in addition to the dominant C 1s and N 1s related peaks, a very small 0 1s peak. C 1s spectrum (Fig. 6(a)) can be
C. JAMAand P.
788
Fig. 6. Spectra
from CN0.39 film deposited
into four peaks centered at different curve-resolved binding energies. The N 1s spectrum (Fig. 6(b)) can be decomposed into three peaks. The binding energy values for the different N 1s contributions were 399.4 and 400.8 eV. A low intensity peak at 402.3 eV is attributed to N-0 or N-N or N=N groups [6,13]. Based on the present structural analyses, two major N configurations were demonstrated, one with a sp’ configuration and one with a tetrahedral type of binding configuration (resembling that in /K,N,). By comparison with binding energy values in carbon nitrides films [14], the low N 1s binding energy at 399.4 eV is assigned to N bonded to sp3 hybridized C (C-N) and that at 400.8 eV to N bonded to sp’ hybridized C (C=N). 4. CONCLUSION The films were synthesized on a non-heated substrate with nitrogen composition relative to carbon XN ranging from 0.28 to 0.47. The deposits obtained under CRNP conditions, for which nitrogen atom concentration is high, give evidence of a higher nitrogen film composition in comparison with deposition under NENF. Spectroscopic analysis of CN, films deposited under CRNP demonstrate the exis-
under
GWDMAND
1000 Pa of CRNP:
(a) C 1s and (b) N Is.
tence of two major environments for nitrogen, one in which N is incorporated in the form of nitrogen single bonded to sp3 carbon in tetrahedral environment, and the other in which nitrogen is double bonded to carbon.
REFERENCES 1. Liu, A. Y. and Cohen, M. L., Phys. Rev. B, 1990, 41, 10727. 2. Niu, C., Lu, Y. 2. and Lieber, C. M., Science, 1993, 261, 334. 3. Matsumoto, O., Kotaki, T., Shikano, H., Takemura, K. and Tanaka, S., J. Electrochem. Sot., 1994, L16, 141. 4. Marton, D., Boyd, K. J., Al-Bayati, A. H., Todorov, S. S. and Rabalais, J., Phys. Rev. Left., 1994, 73, 118. 5. Sjbstriim, H., Stafstrom, S., Boman, M. and Sundgren, J. E., Phys. Rev. Letf., 1995, 75, 1336. 6. Sjbstrbm, H., Hultman, L., Sundgren, J. E., Hainsworth, S. V., Page, T. F. and Theunissen, G. S.A. M., J. Vat. Sci. Technol. A, 1996, 14, 56. 7. Powell, C. J. and Larson, P. E., Appl. Surf, Sci., 1978, 1, 186. 8. Han, H. X. and Feldman, B.J., Solid State Commun., 1988, 65, 921. 9. Kaufman, J. h., Metin, S. and Saperstein, D. D., Phys. Rev. B, 1989, 39, 13053. 10. Zhao, X. A., Ong, C. W., Tsang, Y. C., Wong, Y. W.,
Cold remote nitrogen plasma effects on CN, films Chang, P. W. and Choy, C. L., Appl. Phys. Lett., 1995, 66,2652.
11. Kumar, S. and Tansley, T. L., Thin Solid films, 256,44. 12. Nagarkar, P. V. and Sichel, K. E., J. Electrochem., 136, 2979.
1995, 1982,
189
13. Gouzman, I., Brener, R. and Hoffman, A., Surf. Sci., 1995, 331,283. 14. Narayan, J., Reddy, J., Biunno, N., Kanetkar, S. M., Tiwari, P. and Patikh, N., Mater. Sci. Eng. B, 1994, 26, 49.
PII: !3000%6223(98)00005-0
COLD REMOTE NITROGEN PLASMA EFFECTS ON PULSED LASER DEPOSITED CNx FILMS CHARACTERISTICS C. JAMA and P. GOUDMAND* Laboratoire de Physicochimie de I’Energktique et des Plasmas (LPCEP) EA MENESR 1761, Universitk des Sciences et Technologies de Lille, 59655 Villeneuve d’Ascq, cedex, France (Received 30 October 1997; accepted in revised form 9 December
1997)
Abstract-Carbon nitride films were deposited by ablation of carbon molecular fragments from a graphite targets on a silicon substrate after few pulses of a localized transversely excited atmospheric pressure CO2 laser. Deposition media were either a non excited nitrogen flow or cold remote plasma of nitrogen. Fourier transform infrared spectra of the deposited films show a very efficient nitrogen fixation with C-N bands characteristic of tetrahedral carbon. The effect of the distance of deposition zone from the discharge is also discussed. 0 1998 Elsevier Science Ltd. All rights reserved. Key Word-A.
Carbon nitride, B. Laser ablation, B. Plasma deposition, D. Surface properties, C. XPS.
on the target at an incidence angle of 45”. The substrates were placed at a distance of 3 cm from the graphite target. CN, films were deposited during 5 minutes on a silicon substrate by laser ablation from a graphite target under (NENF) or (CRNP) conditions. Nitrogen flow was excited in an electrodeless discharge by means of a microwave Sairem generator 2450 MHz. The transmitted power was ca 800 W. The discharge was produced in a quartz tube, and, by a continuous pumping, the plasma was led to the reaction chamber located at a fixed distance from the discharge equal to 0.9 m.
1. INTRODUCTION
The possible existence of a class of carbon nitrides isomorphic to /I-S&N, was suggested some years ago by Liu and Cohen [l]. The experimental quest to realize this novel compound has resulted in several publications mainly in the few last years [2-41. Most of these report the deposition of amorphous or partly crystalline CN, (~~0.5). However, the mechanical properties of these films have proven to be very interesting for surface engineering [5]. CN, films deposited on Si substrate held at temperatures T, between 150 and 600°C are extremely elastic and hard [6]. In this work CN, films were deposited a by laser ablation of carbon atoms from a graphite target under non-excited nitrogen flow (NENF) or under cold remote nitrogen plasma (CRNP) conditions. Sputtered carbon fragments combined with nitrogen reactive species lead to the formation of a film on the substrate. The aim of this study is to establish if there is a relationship between the CRNP reactive species, such as nitrogen atoms N(4S), and films composition and structure. Characterization of carbon nitride films by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy are also presented.
2.2 Film characterization The films, deposited at a pressure of 500 Pa, were characterized by FTIR (Perkin-Elmer 1600 spectrometer) spectroscopy. The thickness measurements were measured with a profilometer Alpha-step instrument. The surface composition of the deposited films was characterized by XPS (LHS 10 spectrometer). The Al Ka X-ray source was operated at 13 kV and 20 mA current emission. The pressure during analysis was < 1.3 x 10m6Pa. The peaks were curve-resolved assuming Gaussian profiles. The relative atomic stoichiometry N/C and O/C, denoted X, and X0 respectively, were determined according to the ratio [7]:
2. EXPERIMENTAL
2.1 Film preparation A schematic diagram of the experimental set up is presented in Fig. 1. The pulsed transversely excited atmospheric (TEA) CO* laser (203 Lumonics) parameters used were the wavelength 1= 10.56 pm and the pulse duration of 50 nseconds and repetition rate of 1 Hz. The energy per laser irradiation pulse was 10 J, and the laser beam was properly focused
nA -nB
_-
IAi&j
IBjKAi
where IAitBjj is the i(j) photopeak intensity of the element A(B) and KAitBj) is the result term between the cross section of the i(j) core level orbital, the inelastic mean free path and the transmission factor of the analyzer, both of latter being kinetic energydependent. The efficiency of the electron detector was considered to be constant.
*Corresponding author. Tel: 33(O) 320 43 4455; Fax: 33(O) 320 43 4158; e-mail: [email protected] 785
786
C. JAMA and P. GOUIIMANI~
To pump
Fig.
I. Experimental
3. RESULTS
3.1 Deposition rule Figure 2 presents results for films obtained under NENF. It shows for two nitrogen pressures 100 and 500 Pa, the film thickness as a function of the number of the laser irradiation repetition, denoted IV,,. For the two pressures, film thickness increases with Ni,. The deposition rate (film thickness) decreases when nitrogen pressure increased for a given Ni, value. By increasing nitrogen pressure, the gas velocity increases, therefore the energetic particles are evacuated more efficiently giving a low deposition rate.
3.2 Infruredspecfroscopq The infrared spectra of amorphous carbon are typically featureless. However, nitrogenated carbon films spectra present numerous bands such as C-N, C=N, C=C, CN, C-C, CH, or NH, [8- II]. The major lines of carbon nitrides films deposited by plasma decomposition of hydrocarbons and N, were attributed by Han and Feldman [8] as follows: 2190cm-’ as a C=N stretching mode, 1630cm-’ as C=C stretching mode, CH2 and NH, vibrational
1200
800
400
o0
100
200
Nir 300
Fig. 2. Film thickness of the deposit versus the laser irradiation number (A’,,) in NENF.
setup for CN, depositicn.
modes were also detected. Bands at 1370 and 1570 cm I detected for nitrogen-doped amorphous carbon were attributed to the sp2 graphitic bonds by Kaufman et ul. [9] and Kumar and Tansley [ 1I]. For CN, films deposited by pulsed laser, the bands at: 1500&1750 and 1200~1450cm~’ were identified as C-N and C-N, respectively, by Zhao et al. [IO]. Figure 3 presents FTIR spectra. For NENF films, a broad band in the region of lOOOG1600 cm ’ is observed, with an apparent maximum at 1570 cm- ‘, which could be due to C=N vibrational mode [lo]. A peak at 2100&2300 cm- ‘, due to C=N stretching mode, is also observed. When a CRNP plasma is used, the band at 1570 cm-’ shifts by 30 cm-’ towards higher wave numbers. The band in the region of 1000~1600 cm-’ shows a broader feature with no apparent maximum, which may be related to the diamondlike carbon films structure [ 121. The 1250- 1400 cm-i band could correspond to the sp” carbon single bonded to nitrogen C-N in tetrahedral environment. A complete disappearance of the band 2lOOG2300 cm- * is observed. 3.3 XPS spectroscopy
3.3.1 E&et of pressure_ Fig. 4 shows the evolution of films composition as a function of the pressure for films obtained under NENF or under CRNP plasma. It shows that nitrogen composition ratio relative to carbon N/C (X,) incorporated in the films increases with increasing nitrogen pressure for the two cases. The film with the lowest X, value (X, =0.02) is obtained under a pressure of 5 Pa which corresponds to our limit vacuum pressure. XPS analyses show that nitrogen incorporation in the films varied with the deposition conditions. Nitrogen film composition values shown in Fig. 4 give evidence that higher X, values are obtained for films deposited under CRNP conditions. At a pressure of 1000 Pa, nitrogen atomic ratio X,=0.31 is obtained with the NENF whereas, XN increased to 0.39 with CRNP plasma. Nitrogen fixation is then enhanced when CRNP is used. Figure 5 shows the
Cold remote nitrogen plasma effects on CN, films
4000
I .3500
I 3000
r 2500
, 2000
787
I
500 I
I
1000
1500
Fig. 3. FTIR transmission spectra of deposited CNx films at 500 Pa: (a) NENF and (b) in CRNP.
Pressure (Pa) 0
500
1000
Fig. 4. X, atomic ratio as a function of the pressure: (a) NENF; (b) in CRNP. 2.90
C 1s photoelectron peak of the films deposited under CRNP or NENF. When films are deposited under CRNP, important changes are noticed in the spectra. The C Is feature shows an increase of the high binding energy components intensity. This is consistent with the fact that a higher nitrogen composition is obtained for films deposited under CRNP and could also be due to the presence of new nitrogenated chemical environment. The increase of nitrogen composition for films obtained under CRNP can be explain by the fact that nitrogen incorporation into the film takes place during and after the ablation plume, while when films are deposited under NENF, the nitrogen incorporation takes place only in the ablation plume created by the breakdown. 3.4 Efect of the distance from the discharge In order to study the effect of the distance (d) between discharge and the deposition zone, carbon
2a2
2.94 Binding
286
28.3
290
292
Energy (ev)
Fig. 5. C Is spectra of deposited CN, films at 500 Pa under: (a) CRNP and (b) NENF.
nitrides films were deposited, under a pressure of 1000 Pa, in two distinct zones at (d=0.4 and d= 0.9 m). For d= 0.4 m, the substrate is subjected to the short-lived afterglow, while for d=0.9 m it is subjected to the far afterglow. For films deposited at d=0.4 m, X, value was 0.47, whereas for d=0.9 m, it decreased to 0.39. This result can be explained both by the presence of higher energetic species in the short-lived afterglow atom concentration.
and by a higher
nitrogen
3.4.1 Films structure. Spectra from the films deposited under CRNP or NENF reveal, in addition to the dominant C 1s and N 1s related peaks, a very small 0 1s peak. C 1s spectrum (Fig. 6(a)) can be
C. JAMAand P.
788
Fig. 6. Spectra
from CN0.39 film deposited
into four peaks centered at different curve-resolved binding energies. The N 1s spectrum (Fig. 6(b)) can be decomposed into three peaks. The binding energy values for the different N 1s contributions were 399.4 and 400.8 eV. A low intensity peak at 402.3 eV is attributed to N-0 or N-N or N=N groups [6,13]. Based on the present structural analyses, two major N configurations were demonstrated, one with a sp’ configuration and one with a tetrahedral type of binding configuration (resembling that in /K,N,). By comparison with binding energy values in carbon nitrides films [14], the low N 1s binding energy at 399.4 eV is assigned to N bonded to sp3 hybridized C (C-N) and that at 400.8 eV to N bonded to sp’ hybridized C (C=N). 4. CONCLUSION The films were synthesized on a non-heated substrate with nitrogen composition relative to carbon XN ranging from 0.28 to 0.47. The deposits obtained under CRNP conditions, for which nitrogen atom concentration is high, give evidence of a higher nitrogen film composition in comparison with deposition under NENF. Spectroscopic analysis of CN, films deposited under CRNP demonstrate the exis-
under
GWDMAND
1000 Pa of CRNP:
(a) C 1s and (b) N Is.
tence of two major environments for nitrogen, one in which N is incorporated in the form of nitrogen single bonded to sp3 carbon in tetrahedral environment, and the other in which nitrogen is double bonded to carbon.
REFERENCES 1. Liu, A. Y. and Cohen, M. L., Phys. Rev. B, 1990, 41, 10727. 2. Niu, C., Lu, Y. 2. and Lieber, C. M., Science, 1993, 261, 334. 3. Matsumoto, O., Kotaki, T., Shikano, H., Takemura, K. and Tanaka, S., J. Electrochem. Sot., 1994, L16, 141. 4. Marton, D., Boyd, K. J., Al-Bayati, A. H., Todorov, S. S. and Rabalais, J., Phys. Rev. Left., 1994, 73, 118. 5. Sjbstriim, H., Stafstrom, S., Boman, M. and Sundgren, J. E., Phys. Rev. Letf., 1995, 75, 1336. 6. Sjbstrbm, H., Hultman, L., Sundgren, J. E., Hainsworth, S. V., Page, T. F. and Theunissen, G. S.A. M., J. Vat. Sci. Technol. A, 1996, 14, 56. 7. Powell, C. J. and Larson, P. E., Appl. Surf, Sci., 1978, 1, 186. 8. Han, H. X. and Feldman, B.J., Solid State Commun., 1988, 65, 921. 9. Kaufman, J. h., Metin, S. and Saperstein, D. D., Phys. Rev. B, 1989, 39, 13053. 10. Zhao, X. A., Ong, C. W., Tsang, Y. C., Wong, Y. W.,
Cold remote nitrogen plasma effects on CN, films Chang, P. W. and Choy, C. L., Appl. Phys. Lett., 1995, 66,2652.
11. Kumar, S. and Tansley, T. L., Thin Solid films, 256,44. 12. Nagarkar, P. V. and Sichel, K. E., J. Electrochem., 136, 2979.
1995, 1982,
189
13. Gouzman, I., Brener, R. and Hoffman, A., Surf. Sci., 1995, 331,283. 14. Narayan, J., Reddy, J., Biunno, N., Kanetkar, S. M., Tiwari, P. and Patikh, N., Mater. Sci. Eng. B, 1994, 26, 49.