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Evaporation loss and diffusion of antimony in silicon under pulsed laser irradiation
N U C L E A R I N S T R U M E N T S AND METHODS 168 (1980) 4 7 3 - 4 7 7 ;
(~
NORTH-HOLLAND
P U B L I S H I N G CO.
EVAPORATION LOSS AND DIFFUSION OF ANTIMONY IN SILICON UNDER PULSED LASER IRRADIATION ANIMESH K. JAIN, V. N. KULKARNI*, D. K. SOOD, M. SUNDARARAMAN** and R. D. S. YADAV***
Nuclear Physics Division, Bhabha Atomic Research Centre, Bombay 400 085, India
We have studied the loss and diffusion of Sb in Si from a 750 A thick Sb layer evaporated on (I 11) Si wafers under pulsed laser irradiation. A 7 ns (fwhm) duration pulse from a Nd:glass laser (2 = 1.06/lm) was used. RBS analysis with a 1.8 MeV He + beam was done to obtain depth profiles of Sb in Si. The loss of Sb increases with laser energy density upto 1.7 J/cm 2 without appreciable diffusion. At higher energy densities, the evaporation loss of Sb saturates as diffusion sets in. Large diffusion tails up to depths >~1.2 ~m are observed at 8.9 J/cm 2. Surface topography of laser-treated region was studied with a Scanning Electron Microscope. The surface topography varies dramatically with the incident laser energy density. A novel feature is the appearance of a curious ' criss-cross' line pattern with spacings close to wavelength of laser light at lower energy densities. At high energy densities, considerable damage to the Si surface is observed. Our results indicate that a careful choice of the laser energy density and pulse duration has to be made for a practical application of the technique of doping in semiconductors by laser treating an evaporated dopant layer.
1. Introduction High power lasers have recently been employed for annealing ion implantation damage in semiconductors~-3), for causing amorphous to polycrystalline 4-6) to single-crystal 7) transitions. Almost complete removal of the implantation damage by laser annealing g'9) has been observed, which has made this technique very promising. The mechanism of laser annealing has been identified as the resolidification of a surface meltS°'11). Doping in Si by lasertreating a surface film of the dopant has recently been reported ~2'13). Laser induced reactions of metallic films ~4) on Si have also been observed. The simplicity of this technique employing deposited films makes it attractive for use in semiconductor technology. The evaporation loss and the extent of diffusion from the dopant film during laser treatment are important aspects governing the viability of this technique. In this paper, we report our measurements on the evaporation loss and diffusion of Sb films on Si during pulsed laser irradiation. Rutherford backscattering of 1.8 MeV He + ions was used to obtain the depth distribution of Sb in Si after laser treatment at various energy densities. The surface features produced by the laser pulse were studied with a Scanning Electron Microscope. * Visiting Research Fellow (C.S.I.R.) from Marathwada University, Aurangabad-431 004, India. ~* Metallurgy Division, B.A.R.C. *** Visiting Research Fellow (C.S.I.R.) from Banaras Hindu University, Varanasi-221 005, India.
2. Experimental About 0.5 mm thick, 25 mm diam. wafers of ptype (1000.C2cm), ( l i d Si were used. Antimony (five nines pure) was evaporated under vacuum (< 10-5 torr) on the specimens at room temperature to produce 750 A thick Sb layers. The Nd:glass laser (2 = 1.06/~m) at the laser section, B.A.R.C., Bombay was employed in a (TEM)~ mode for laser irradiation in air. The laser parameters were a fixed pulse duration of 7 ns fwhm, focal spot on target with 1/e diameter from 3.5 mm to 5.6 mm and pulse energy from 0.69 J to 0.89 J (measured with a sensitive calorimeter). Each specimen was irradiated with a single laser pulse. The RBS measurements were done with the 2 MeV Van de Graaff accelerator at the Indian Institute of Technology, Kanpur. A well collimated beam (about 1 mm diam.) of He + ions at 1.8 MeV could be accurately positioned on the laser treated region of the specimen mounted on a translation stage. The backscattered He + particles were detected at 170° using an ORTEC surface barrier detector, 142 A preamp, and an ORTEC 571 amplifier. A relatively large solid angle of 20 msr was used yielding an overall system resolution of 28 keV fwhm, corresponding to a depth resolution of 580 A in Si. Several RBS measurements were made across the laser-treated region of a specimen with incident beam spot spacing of 1 ram. Thus each RBS spectrum corresponds to a well defined laser energy density up to 8.9 J/cm 2. The ETEC Scanning Electron Microscope at the Metallurgy VII.
NEW A P P L I C A T I O N S
474
A.K. JAIN et al.
Division, B.A.R.C., Bombay, was used for studying the surface topography of laser treated regions. 3. Results The laser treated region could be readily identified with naked eye on all specimens, by marked changes in colour and appearance. The laser energy density for each RBS beam spot is determined accurately from its known position and a trace of the SEM micrographl5), assuming a Gaussian spatial distribution of laser intensity. Figure 1 shows some RBS spectra obtained at indicated laser energy densities. As laser energy density increases, the area under the Sb peak reduces accompanied by narrowing of the peak up to 1.7 J/cm 2. This indicates evaporation of Sb from film surface. At 1.7 J/cm 2, the diffusion of Sb is small, whereas evaporation loss is dominant (78% of the initial Sb content). At 5.4J/cm 2, a pronounced diffusion tail extending up to the Si edge is observed and the fraction of Sb lost also reduces.
The loss of Sb as a function of laser energy density is shown in fig. 2. The topography of the laser treated surface changes dramatically with laser energy density. Figure 3 shows a secondary electron SEM micrograph of the region irradiated with a laser pulse of 0.89J over 1/e beam diam. of - 3 . S m m . The boundary of the laser treated region can be readily identified above arrow ' b ' . SEM micrographs taken at higher magnifications at positions indicated by labelled arrows are shown in fig. 4. The as-evaporated film surface is quite featureless (fig. 4(a)). It develops a 'criss-cross' pattern of lines (fig. 4(b)) becoming pronounced at 2.76J/cm 2 in fig. 4(c). These lines appear to be rich in Sb since Sb-rich regions would appear lighter in contrast to Si in secondary electron micrograph due to increased secondary electron yield. When viewed at 800 × these lines reveal the presence of Sb globules. The maximum globule size observed is about 0.3 ~m. At higher energy densities, a bright region
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Fig. 1. 1.8 M e V H e + R B S s p e c t r a at i n d i c a t e d l a s e r e n e r g y d e n s i t i e s s h o w i n g
loss a n d d i f f u s i o n f r o m a 750 A. Sb f i l m o n Si.
ANTIMONY
IN S I L I C O N
475
80
60
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100
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Fig. 2. The percentage Joss o f Sb vs incident laser energy density.
is observed which is identified to be due to considerable damage to the surface as is seen in fig. 4(d) for 8.9 J/cm 2. The dark regions on the laser spot (e.g. region ' e ' in fig. 3) are quite smooth (fig. 4(e)) and show ripples at a few sites, clearly seen at higher magnification. 4. Discussion We have performed a single phase heating calculation 16) for estimating the surface melting and evaporation thresholds for Sb. For our laser pulse (7 ns fwhm) we get 0.26 J/cm 2 and 0.6 J/cm 2 as the melting and evaporation thresholds respectively. Since evaporation of Sb (boiling point 1440°C) would start earlier than melting of Si (melting point 1430°C) surface which is buried in the Sb film, a multiphase calculation of the thermal diffusion equation is required for determining the melt depth and duration. However, an estimate based on energy balance considerations 15) gives a melt depth of - 4 / a m in Si for 8.9 J/cm: laser energy density. It is interesting to note from fig. 2 that the observed threshold for loss of Sb is in good agreement with the calculated value of 0.6 J/cm 2 for Sb film. The evaporation loss from Sb film peaks around 1.5 J/cm 2 which is probably close to the melt threshold of underlying Si. As Si starts melting, appreciable Sb diffusion sets in causing saturation of Sb loss at higher energy densities. A similar evaporation loss behaviour is also observed for laser-treated Sb films on AIIS). The observed diffusion tail, which extends up to the Si edge, corresponding to diffusion up to depths < 1.2/am, indi-
Fig. 3. Secondary electron - SEM micrograph showing general view o f a laser-treated region. The laser pulse energy was 0.89 J over a 3.5 m m 1/e beam diameter. The arrows show regions with representative surface features.
cates appreciable intermixing of Sb and Si during laser treatment. The curious 'criss-cross' patterns in figs. 4(b) and 4(c) have a line spacing of ~ 1 / a m close to the wavelength of laser light (1.06/am). This suggests a situation similar to 'ripples' reported earlier in Si]7). The interference of the primary laser beam with a wave scattered from a surface disturbance, gives rise to intensity variations at the surface, causing periodic melting, if the power density is near melt threshold. From fig. 4 we see that the pattern starts showing up at laser energy density of 0.36 J/cm 2 which is close to the melt threshold of 0.26 J/cm 2 for Sb. The pattern is very pronounced at 2.76 J/ cm 2 (fig. 4(c)). At higher magnification, Sb globules of size up to 0.3/am are seen along the lines of the pattern. These globules are possibly formed when the solidification front at the solid-liquid Si interface travels upwards to meet unreacted molten Sb. If we assume that liquid Sb does not wet the solid Si surface, the globules will be formed. At higher energy densities, considerable damage is observed on the surface (fig. 4(d)). This topography does not resemble frozen liquid meniscus and may be a consequence of excessive Si surface evaporation. The presence of smooth (dark) regions (fig. 3, region ~e') within the excessive damage zone is intriguing and at present we are unable to give any explanation for their occurrence. However, it may be noted that the ripples appearing at a few sites on VII.
NEW APPLICATIONS
476
A . K . J A I N et al.
Fig. 4. Higher magnification SEM micrographs of the arrowed regions shown in fig. 3 (a) at 0 J/cm 2 (away from laser spot); (b) at 0.36 J/cm 2 where the 'criss-cross' pattern is just showing up: (c) at 2.76 J/crn 2 showing pronounced 'criss-cross' pattern and globules of Sb at higher magnification ; (d) at 8.9 J/cm 2 showing significant surface damage; and (e) the dark smooth region showing ' ripples'.
Considerable evaporation loss of Sb takes place during laser treatment and has been studied in detail. Evaporation loss is particularly dominant at lower energy densities; whereas surface damage occurs at high energy densities rendering the surface unsuitable for device purposes. A careful choice of laser energy density has therefore to be made in a practical application of this technique. Perhaps use of longer pulse durations can extend the range of useful energy densities. We thank H.C. Pant and L.M. Kukreja for laser treatment. We thank G.K. Mehta, S. Sen, K.M. Varier, S.C.L. Sharma, A.K. Sinha, K.M.L. Jha, M.M. Gupta and K. Masood for their assistance during RBS experiments. The assistance rendered by C.V. Fernandes in the preparation of the manuscript is thankfully acknowledged. We thank P.K. Iyengar, M.K. Mehta and D.D. Bhawalkar for their interest in the present work. VNK and RDSY wish to acknowledge financial support from the Council of Scientific and Industrial Research, New Delhi, India. References vii
these smooth regions (fig. 4(e)) have a spacing close to the wavelength of laser light (1.06 ~m). 5. Conclusions
The present work has shown that the laser treatment of Sb film evaporated on Si can lead to diffusion of Sb to depths suitable for device fabrication.
1) E. I. Shtyrkov, 1. B. Khaibullin, M. M. Zaripov, M. F. Galyatudinov and R.M. Bayazitov, Fiz. Tekh, Poluprovodn. 9 (1975) 2000 (Sov. Phys. - Semicond. 9 (1976) 1309). 2) R.T. Young, C.W. White, G. J, Clark, J. Narayan, W.H. Christie, M. Murakami, P. W. King and S. D. Kramer, Appl. Phys. Lett. 32 (1978) 139. 3) G.K. CeUer, J.M. Poate and L.C. Kimerling, Appl. Phys. Lett. 32 (1978) 464. 4) G. Foti, E. Rimini, G. Vitali and M. Bertolotti, Appl. Phys. 14 (1977) 189. 5) j.C. Bean, H.J. Leamy, J.M. Poate, G. A. Rozgonyi, T. T.
ANTIMONY 1N SILICON
6) 7) 8) 9) 0)
Sheng, J. S. Williams and G. K. Celler, Appl. Phys. Lett. 33 (1978) 227. p. R6vesz, G. Farkas, G. Mezey and J. Gyulai, Appl. Phys. Lett. 33 (1978) 431. G. Vitali, M. Bertolotti, G. Foti and E. Rimini, Appl. Phys. 17 (1978) 111. G. Foti, S. U. Campisano and E. Rimini, J. Appl. Phys. 49 (1978) 2569. C.W. White, P.P. Pronko, S.R. Wilson, B.R. Appleton, J. Narayan and R.T. Young, J. Appl. Phys., to be published. D.H. Auston, C.M. Surko, T.N.C. Venkatesan, R.E. Slusher and J. A. Golovchenko, Appl. Phys. Lett. 33 (1978) 437.
477
1l) p. Baeri, S. U. Campisano, G. Foti and E. Rimini, J. Appl. Phys. 50 (1979) 788. ~2) K. Affolter, W. Ltithy and M. von Allmen, Appl. Phys. Lett. 33 (1978) 185. 13) j. Narayan, R.T. Young, R.F. Wood and W.H. Christie, Appl. Phys. Lett. 33 (1978) 338. 14) j.M. Poate, H.J. Leamy, T.T. Sheng and G.K. Celler, Appl. Phys. Lett. 33 (1978) 918. 15) A.K. Jain, V.N. Kulkarni, D.K. Sood, M. Sunderaraman and R. D. S. Yadav, these Proceedings, p. 275. 16) j . F . Ready, in Effects of high power laser radiation (Academic Press, New York, 1971) p. 76. 17) H.J. Leamy, G. A. Razgonyi, T.T. Sheng and G. K. Celler, Appl. Phys. Lett. 32 (1978) 535.
VII. NEW A P P L I C A T I O N S
(~
NORTH-HOLLAND
P U B L I S H I N G CO.
EVAPORATION LOSS AND DIFFUSION OF ANTIMONY IN SILICON UNDER PULSED LASER IRRADIATION ANIMESH K. JAIN, V. N. KULKARNI*, D. K. SOOD, M. SUNDARARAMAN** and R. D. S. YADAV***
Nuclear Physics Division, Bhabha Atomic Research Centre, Bombay 400 085, India
We have studied the loss and diffusion of Sb in Si from a 750 A thick Sb layer evaporated on (I 11) Si wafers under pulsed laser irradiation. A 7 ns (fwhm) duration pulse from a Nd:glass laser (2 = 1.06/lm) was used. RBS analysis with a 1.8 MeV He + beam was done to obtain depth profiles of Sb in Si. The loss of Sb increases with laser energy density upto 1.7 J/cm 2 without appreciable diffusion. At higher energy densities, the evaporation loss of Sb saturates as diffusion sets in. Large diffusion tails up to depths >~1.2 ~m are observed at 8.9 J/cm 2. Surface topography of laser-treated region was studied with a Scanning Electron Microscope. The surface topography varies dramatically with the incident laser energy density. A novel feature is the appearance of a curious ' criss-cross' line pattern with spacings close to wavelength of laser light at lower energy densities. At high energy densities, considerable damage to the Si surface is observed. Our results indicate that a careful choice of the laser energy density and pulse duration has to be made for a practical application of the technique of doping in semiconductors by laser treating an evaporated dopant layer.
1. Introduction High power lasers have recently been employed for annealing ion implantation damage in semiconductors~-3), for causing amorphous to polycrystalline 4-6) to single-crystal 7) transitions. Almost complete removal of the implantation damage by laser annealing g'9) has been observed, which has made this technique very promising. The mechanism of laser annealing has been identified as the resolidification of a surface meltS°'11). Doping in Si by lasertreating a surface film of the dopant has recently been reported ~2'13). Laser induced reactions of metallic films ~4) on Si have also been observed. The simplicity of this technique employing deposited films makes it attractive for use in semiconductor technology. The evaporation loss and the extent of diffusion from the dopant film during laser treatment are important aspects governing the viability of this technique. In this paper, we report our measurements on the evaporation loss and diffusion of Sb films on Si during pulsed laser irradiation. Rutherford backscattering of 1.8 MeV He + ions was used to obtain the depth distribution of Sb in Si after laser treatment at various energy densities. The surface features produced by the laser pulse were studied with a Scanning Electron Microscope. * Visiting Research Fellow (C.S.I.R.) from Marathwada University, Aurangabad-431 004, India. ~* Metallurgy Division, B.A.R.C. *** Visiting Research Fellow (C.S.I.R.) from Banaras Hindu University, Varanasi-221 005, India.
2. Experimental About 0.5 mm thick, 25 mm diam. wafers of ptype (1000.C2cm), ( l i d Si were used. Antimony (five nines pure) was evaporated under vacuum (< 10-5 torr) on the specimens at room temperature to produce 750 A thick Sb layers. The Nd:glass laser (2 = 1.06/~m) at the laser section, B.A.R.C., Bombay was employed in a (TEM)~ mode for laser irradiation in air. The laser parameters were a fixed pulse duration of 7 ns fwhm, focal spot on target with 1/e diameter from 3.5 mm to 5.6 mm and pulse energy from 0.69 J to 0.89 J (measured with a sensitive calorimeter). Each specimen was irradiated with a single laser pulse. The RBS measurements were done with the 2 MeV Van de Graaff accelerator at the Indian Institute of Technology, Kanpur. A well collimated beam (about 1 mm diam.) of He + ions at 1.8 MeV could be accurately positioned on the laser treated region of the specimen mounted on a translation stage. The backscattered He + particles were detected at 170° using an ORTEC surface barrier detector, 142 A preamp, and an ORTEC 571 amplifier. A relatively large solid angle of 20 msr was used yielding an overall system resolution of 28 keV fwhm, corresponding to a depth resolution of 580 A in Si. Several RBS measurements were made across the laser-treated region of a specimen with incident beam spot spacing of 1 ram. Thus each RBS spectrum corresponds to a well defined laser energy density up to 8.9 J/cm 2. The ETEC Scanning Electron Microscope at the Metallurgy VII.
NEW A P P L I C A T I O N S
474
A.K. JAIN et al.
Division, B.A.R.C., Bombay, was used for studying the surface topography of laser treated regions. 3. Results The laser treated region could be readily identified with naked eye on all specimens, by marked changes in colour and appearance. The laser energy density for each RBS beam spot is determined accurately from its known position and a trace of the SEM micrographl5), assuming a Gaussian spatial distribution of laser intensity. Figure 1 shows some RBS spectra obtained at indicated laser energy densities. As laser energy density increases, the area under the Sb peak reduces accompanied by narrowing of the peak up to 1.7 J/cm 2. This indicates evaporation of Sb from film surface. At 1.7 J/cm 2, the diffusion of Sb is small, whereas evaporation loss is dominant (78% of the initial Sb content). At 5.4J/cm 2, a pronounced diffusion tail extending up to the Si edge is observed and the fraction of Sb lost also reduces.
The loss of Sb as a function of laser energy density is shown in fig. 2. The topography of the laser treated surface changes dramatically with laser energy density. Figure 3 shows a secondary electron SEM micrograph of the region irradiated with a laser pulse of 0.89J over 1/e beam diam. of - 3 . S m m . The boundary of the laser treated region can be readily identified above arrow ' b ' . SEM micrographs taken at higher magnifications at positions indicated by labelled arrows are shown in fig. 4. The as-evaporated film surface is quite featureless (fig. 4(a)). It develops a 'criss-cross' pattern of lines (fig. 4(b)) becoming pronounced at 2.76J/cm 2 in fig. 4(c). These lines appear to be rich in Sb since Sb-rich regions would appear lighter in contrast to Si in secondary electron micrograph due to increased secondary electron yield. When viewed at 800 × these lines reveal the presence of Sb globules. The maximum globule size observed is about 0.3 ~m. At higher energy densities, a bright region
,,s EV.,.,:'O,:,ATFD 7t 15001
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Fig. 1. 1.8 M e V H e + R B S s p e c t r a at i n d i c a t e d l a s e r e n e r g y d e n s i t i e s s h o w i n g
loss a n d d i f f u s i o n f r o m a 750 A. Sb f i l m o n Si.
ANTIMONY
IN S I L I C O N
475
80
60
pq
o
0
~ 3o 0 _1
20 -
5 b EVAPORATED ON Si ( 7 5 0 A THICK)
100
I
I
2
I
I
I
I
I
3 4 5 6 7 LASER ENERGY (.//crn ~)
I
8
I
9
10
Fig. 2. The percentage Joss o f Sb vs incident laser energy density.
is observed which is identified to be due to considerable damage to the surface as is seen in fig. 4(d) for 8.9 J/cm 2. The dark regions on the laser spot (e.g. region ' e ' in fig. 3) are quite smooth (fig. 4(e)) and show ripples at a few sites, clearly seen at higher magnification. 4. Discussion We have performed a single phase heating calculation 16) for estimating the surface melting and evaporation thresholds for Sb. For our laser pulse (7 ns fwhm) we get 0.26 J/cm 2 and 0.6 J/cm 2 as the melting and evaporation thresholds respectively. Since evaporation of Sb (boiling point 1440°C) would start earlier than melting of Si (melting point 1430°C) surface which is buried in the Sb film, a multiphase calculation of the thermal diffusion equation is required for determining the melt depth and duration. However, an estimate based on energy balance considerations 15) gives a melt depth of - 4 / a m in Si for 8.9 J/cm: laser energy density. It is interesting to note from fig. 2 that the observed threshold for loss of Sb is in good agreement with the calculated value of 0.6 J/cm 2 for Sb film. The evaporation loss from Sb film peaks around 1.5 J/cm 2 which is probably close to the melt threshold of underlying Si. As Si starts melting, appreciable Sb diffusion sets in causing saturation of Sb loss at higher energy densities. A similar evaporation loss behaviour is also observed for laser-treated Sb films on AIIS). The observed diffusion tail, which extends up to the Si edge, corresponding to diffusion up to depths < 1.2/am, indi-
Fig. 3. Secondary electron - SEM micrograph showing general view o f a laser-treated region. The laser pulse energy was 0.89 J over a 3.5 m m 1/e beam diameter. The arrows show regions with representative surface features.
cates appreciable intermixing of Sb and Si during laser treatment. The curious 'criss-cross' patterns in figs. 4(b) and 4(c) have a line spacing of ~ 1 / a m close to the wavelength of laser light (1.06/am). This suggests a situation similar to 'ripples' reported earlier in Si]7). The interference of the primary laser beam with a wave scattered from a surface disturbance, gives rise to intensity variations at the surface, causing periodic melting, if the power density is near melt threshold. From fig. 4 we see that the pattern starts showing up at laser energy density of 0.36 J/cm 2 which is close to the melt threshold of 0.26 J/cm 2 for Sb. The pattern is very pronounced at 2.76 J/ cm 2 (fig. 4(c)). At higher magnification, Sb globules of size up to 0.3/am are seen along the lines of the pattern. These globules are possibly formed when the solidification front at the solid-liquid Si interface travels upwards to meet unreacted molten Sb. If we assume that liquid Sb does not wet the solid Si surface, the globules will be formed. At higher energy densities, considerable damage is observed on the surface (fig. 4(d)). This topography does not resemble frozen liquid meniscus and may be a consequence of excessive Si surface evaporation. The presence of smooth (dark) regions (fig. 3, region ~e') within the excessive damage zone is intriguing and at present we are unable to give any explanation for their occurrence. However, it may be noted that the ripples appearing at a few sites on VII.
NEW APPLICATIONS
476
A . K . J A I N et al.
Fig. 4. Higher magnification SEM micrographs of the arrowed regions shown in fig. 3 (a) at 0 J/cm 2 (away from laser spot); (b) at 0.36 J/cm 2 where the 'criss-cross' pattern is just showing up: (c) at 2.76 J/crn 2 showing pronounced 'criss-cross' pattern and globules of Sb at higher magnification ; (d) at 8.9 J/cm 2 showing significant surface damage; and (e) the dark smooth region showing ' ripples'.
Considerable evaporation loss of Sb takes place during laser treatment and has been studied in detail. Evaporation loss is particularly dominant at lower energy densities; whereas surface damage occurs at high energy densities rendering the surface unsuitable for device purposes. A careful choice of laser energy density has therefore to be made in a practical application of this technique. Perhaps use of longer pulse durations can extend the range of useful energy densities. We thank H.C. Pant and L.M. Kukreja for laser treatment. We thank G.K. Mehta, S. Sen, K.M. Varier, S.C.L. Sharma, A.K. Sinha, K.M.L. Jha, M.M. Gupta and K. Masood for their assistance during RBS experiments. The assistance rendered by C.V. Fernandes in the preparation of the manuscript is thankfully acknowledged. We thank P.K. Iyengar, M.K. Mehta and D.D. Bhawalkar for their interest in the present work. VNK and RDSY wish to acknowledge financial support from the Council of Scientific and Industrial Research, New Delhi, India. References vii
these smooth regions (fig. 4(e)) have a spacing close to the wavelength of laser light (1.06 ~m). 5. Conclusions
The present work has shown that the laser treatment of Sb film evaporated on Si can lead to diffusion of Sb to depths suitable for device fabrication.
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VII. NEW A P P L I C A T I O N S