G. Lulli - Academia.edu (original) (raw)
Papers by G. Lulli
Reference CIME-ARTICLE-1997-003View record in Web of Science Record created on 2007-02-15, modifi... more Reference CIME-ARTICLE-1997-003View record in Web of Science Record created on 2007-02-15, modified on 2017-05-12
MRS Proceedings, 1985
ABSTRACTSome renarks about the mechanism for dynamic annealing during high dose rate P implantati... more ABSTRACTSome renarks about the mechanism for dynamic annealing during high dose rate P implantation of Si are reported. TEM observations and RBS channeling measurements show that the ion bombardment enhances the amorphous to crystalline transformation in the temperature range 200 ≤ T ≤ 600°C. It is found that the ratio between the observed recrystalli-zation velocity and the thermal SPE velocity decreases with increasing temperature. This indicates that a transition temperature must exist between the ion-assisted recrystallization regime and the ?lermal SPE regime. For the energy (100 keV) and the dose rate (60,uA/cm2) used in our experiments the transition temperature is about 700°C.
MRS Proceedings, 1988
ABSTRACTSolid-phase epitaxy of implanted Si is observed at room temperature during in situ electr... more ABSTRACTSolid-phase epitaxy of implanted Si is observed at room temperature during in situ electron irradiation in a Transmission Electron Microscope. Results obtained from irradiation of cross sections of samples containing different doping species show that: i) the basic mechanism of the process is the migration and recombination at the amorphous-crystalline interface of radiation defects coming both from the amorphous and crystalline side; ii) the diffusion length of such defects is of the order of 40 nm; iii) the regrowth rate is impurity dependent: a factor two exists between the faste
Fourth E.C. Photovoltaic Solar Energy Conference, 1982
Experiments were performed to examine two techniques for annealing solar cells. P(+) ions were im... more Experiments were performed to examine two techniques for annealing solar cells. P(+) ions were implanted, followed by e-beam annealing using a new electron gun with a beam width that can be varied, thereby eliminating the necessity for scanning. Other trials were run using a 50 W/sq cm ion beam for the implantation, thereby reaching a cell temperature of 1300 C,
physica status solidi (a), 1986
physica status solidi (a), 1986
BY M. BERTI (a), A. V. DRIGO (a), G. LULLI (b), P. G. MERLI (b), and M. VITTORI ANTISARI (c) TEM ... more BY M. BERTI (a), A. V. DRIGO (a), G. LULLI (b), P. G. MERLI (b), and M. VITTORI ANTISARI (c) TEM and RBS analysis are made of (100) Si specimens implanted with 100 keV P+ ions at a dose rate of 60 pA/cmz, in order to investigate the mechanism for dynamic annealing. The activation energy for regrowth during ion irradiation is found t o be 0.31 eV, much lower than the value for thermal epitaxy of (1OO)Si. The comparison with samples implanted a t room temperature and annealed with an e-beam of the same power density shows that in the temperature range 230 t o 620 "C and for the irradiation times used in the experiments (t 5 7.6 s), the pure contribution o beam heating to the regrowth process is negligible. This result supports the hypothesis that the mechanism responsible for dynamic annealing during high flux ion implantation is the recombination a t t,he a/c interface of point defects produced by the elastic collision of energetic ions with the target atoms. From the regrowth data it can be deduced that, in this kind of annealing regime, the recrystallization rates in <loo) and (111> directions are of the same order of magnitude. Um den Mechanismus der dynamischen Ausheilung zu untersuchen, werden TEM und RBS-Analyse von (lOO)-Si-Proben durchgefuhrt, die mit 100 keV P+-Ionen und einer Dosisrate von 60 pA/cmz implantiert werden. Die Aktivierungsenergie fur Rekristallisation wahrend Ionenbestrahlung wird z u 0,31 eV, vie1 niedriger als der Wert fur thermische Epitaxis von (100)-Si, bestimmt. Der Vergleich mit bei Zimmertemperatur implantierten und mit einem Elektronenstrahl ausgeheilten Proben rnit derselben Leistungsdichte zeigt, daB im Temperaturbereich 230 bis 620 "C und fur Bestrahlungszeiten in den Experimenten (t 5 7,6 s) der reine Beitrag der Strahlheizung zum RekristallisationsprozeB vernachliissigbar ist. Dieses Ergebnis bestatigt die Hypothese, daS der fur die dynamische Ausheilung wahrend dieser HochflnB-Ionen-Implantation verantwortliche Mechanismus die Rekombination von Punktdefekten an der m/c-Grenzflache ist, die durch elastische StoBe der energiereichen Ionen rnit den Targetatomen hervorgerufen werden. Aus den Rekristallisationswerten kann gefolgert werden, daB bei dieser Art des Ausheilungsregimes dieRekristallisationsraten in (100)-und (11 1)-Richtungen von gleicher GroBenordnung sind.
Philosophical Magazine Letters, 1998
The characterization of defects produced during self-annealing implantation of P + ions in silico... more The characterization of defects produced during self-annealing implantation of P + ions in silicon is of great interest for the realization of good quality p± n junctions in silicon and to understand the peculiarity of beam± solid interactions occurring during implantation performed under the conditions of rather high current and power density. High-resolution electron holography is employed here to study the three-dimensional con® guration of nanometre-size voids obtained by P + ion bombardment of a silicon wafer. Reconstructed phase di erence information has been used to obtain maps in which the phase distribution gives a qualitative topography of the cavity shape as well as quantitative measurements of the depth variations.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
The Rutherford backscattering spectroscopy (RBS) surface height of a pure bulk material can be us... more The Rutherford backscattering spectroscopy (RBS) surface height of a pure bulk material can be used as an absolute standard value to calibrate the detector solid angle. This work presents the results of an international collaboration started at the beginning of 1998 to define the surface height of the RBS spectrum (H0) of Si, amorphized by ion implantation to avoid channeling.
Materials Science Forum, 1998
Materials Science Forum Vols. 264-268 (1998) pp 733-736 Online available since 1998/Feb/01 at www... more Materials Science Forum Vols. 264-268 (1998) pp 733-736 Online available since 1998/Feb/01 at www.scientific.net © (1998) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/MSF.264-268.733 ... All rights reserved. No part of ...
Materials Science Forum, 1996
Physical Review B, 2004
We investigate the application of atomistic models of self-interstitial defects to the simulation... more We investigate the application of atomistic models of self-interstitial defects to the simulation of Rutherford backscattering-channeling ͑RBS-C͒ spectra in ion irradiated Si. By the comparison of simulated and experimental measurements, we verify the ability of different models, either of elementary interstitials or of small clusters, to reproduce experimental spectra measured under different alignment conditions in Si lightly damaged by Si ϩ ion implantation. A model system for RBS-C simulation is built by inserting a distribution of defects in a supercell with size of ϳ10 6 atoms. The system is then structurally relaxed by the application of the classical environment-dependent interatomic potential ͑EDIP͒. After adjusting the defect distribution in order to fit the ͗100͘ RBS-C spectrum, simulations are performed under the other alignment conditions investigated. The scattering factors of defects are then extracted from both experimental and simulated RBS-C spectra and compared. It is shown that the anisotropy of experimental damage is not compatible with a significant presence of random ͑incoherent͒ disorder, but can be reproduced by some of the defect models under consideration: the split-͗110͘ interstitial, the diinterstitial formed by the addition of an interstitial to the split-͗110͘ interstitial, and two different configurations of the four-interstitial aggregate; one formed by two close diinterstitials and the other by the aggregation of four split-͗100͘ interstitials. Due to the different ͗100͘ scattering factors of the four defect configurations which are found to reproduce experimental spectra, there is an inherent uncertainty of a factor of 2 in the estimate of the amount of interstitials by ͗100͘ RBS-C analysis. The agreement between simulations and experiments is remarkable, considering that the method makes use of physical, although empirical, models of defects, where the only adjustable parameter is the absolute concentration of interstitials.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1995
Electron paramagnetic resonance and double crystal X-ray diffraction were used to analyse damage ... more Electron paramagnetic resonance and double crystal X-ray diffraction were used to analyse damage accumulation with dose in silicon implanted at room temperature with B and Si ions at 50 keV and MeV energies. Electron paramagnetic resonance reveals the presence of SCP3 (neutral tetravacancy), D centers (indicative of amorphous Si), and I: centers, which are probably vacancy complexes. The total number of (ZZ + D) centers and the depth integral of the lattice strain determined by X-rays increase sublinearly with increasing dose. The sublinearity is interpreted in terms of dynamic annealing of the defects during implantation. Suggestions are mr,d-to explain the differences observed in the results of Si and B implants.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
Spectra of He ions backscattered from thin (001) Si membranes and bulk Si/SiO2 wafers are analyze... more Spectra of He ions backscattered from thin (001) Si membranes and bulk Si/SiO2 wafers are analyzed with the aid of simulation based on the binary collision approximation. Due to precise control of experimental parameters and detailed fitting of random spectra in thin specimens, the curve of random electronic energy loss per unit length in the energy interval 1.5–3 MeV can
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
Nuclear Instruments and Methods in Physics Research B 112 (I 996) 148-15 I IiYlUM B EISEVIER Beam... more Nuclear Instruments and Methods in Physics Research B 112 (I 996) 148-15 I IiYlUM B EISEVIER Beam Interactions with Materials 8 Atoms
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Atomistic simulation of ion channeling in Si shows that the lattice deformation around point defe... more Atomistic simulation of ion channeling in Si shows that the lattice deformation around point defects, calculated by empirical potentials, gives a significant contribution to the backscattering yield of He ions channeled along major axial or planar directions. This effect, whose amount depends on defect type, beam-alignment condition and model potential used to relax the system, is expected to have consequences on the interpretation of Rutherford backscattering-channeling analysis. A model of structurally relaxed point defects, including split-h1 1 0i interstitials and vacancies, has been applied to the interpretation of multiaxial channeling analysis in the slightly damaged surface region of Si implanted with MeV ions. Despite the simple microscopic structure of damage assumed in the model, the method leads to a significantly better agreement with experiments then the standard models which treat defects as individually displaced atoms in an unperturbed lattice.
Materials Letters, 1986
... 4, number 4 MATERIALS LETTERS June 1986 e-BEAM-INDUCED LATERAL SEEDED EPITAXY OF SILICON ON I... more ... 4, number 4 MATERIALS LETTERS June 1986 e-BEAM-INDUCED LATERAL SEEDED EPITAXY OF SILICON ON INSULATOR R. ANGELUCCI, G. LULLI ... film depends on the energy absorption into the target, proceeding from seed openings to the islands, if the maximum of the ...
Journal of The Electrochemical Society, 1987
Thermally induced defects in CZ silicon are studied, with the aim of identifying the mechanisms r... more Thermally induced defects in CZ silicon are studied, with the aim of identifying the mechanisms responsible for lifetime changes and the role of oxygen in them. For low temperature heatings lifetime can either decrease or increase: a gettering activity of neutral oxygen clusters which participate in the dissociation equilibria of Fe-B pairs is postulated. The effects of pretreatments performed by
Journal of Applied Physics, 1990
ABSTRACT Several electron microscopy techniques were used to investigate in detail the structure ... more ABSTRACT Several electron microscopy techniques were used to investigate in detail the structure of the defects produced by implantation of Si with high current density As+ ion beam under self‐annealing conditions (i.e., with simultaneous damage recovery activated by the transient beam heating). The defects, which display a basic octahedral shape, appear if the irradiation is prolonged after the time for which the transient beam heating has produced the complete crystallization of the previously amorphized surface layer. With increasing irradiation time and temperature they grow up to a maximum diameter of about 20 nm, and concentrate in a band located around the position of the maximum of nuclear energy loss of As+ ions, where a segregation peak of electrically inactive As is developed simultaneously. The results of different microstructural and microanalytical techniques used to investigate the defects (conventional and high resolution electron microscopy, electron holography, and energy dispersion x‐ray microanalysis) give information which leads us to identify them as large vacancy aggregates, or voids, with As atoms segregated in proximity of the inner surfaces. The role of As atoms is likely to reduce the strain energy which a vacancy aggregate is expected to produce in the surrounding lattice.
Journal of Applied Physics, 1989
ABSTRACT Anomalous distribution of As implanted in silicon under self‐annealing conditions (i.e.,... more ABSTRACT Anomalous distribution of As implanted in silicon under self‐annealing conditions (i.e., with simultaneous damage recovery activated by beam heating) has been investigated and discussed. Rutherford backscattering/channeling, transmission electron microscopy, and carrier profiling techniques have been used to analyze the dopant profiles and the microstructure of samples irradiated with 150‐keV As+ ions at a current density of ≂207 μA/cm2, for times of 2, 3, 4, 5, and 6 s. Two relevant effects are observed. The first one consists in the formation of two dopant peaks, electrically inactive, separated by a depletion region at the position of the ion projected range. While the deeper peak disappears with increasing irradiation time, the one located at the maximum of nuclear energy loss grows. Microstructural analysis suggests that both peaks occur as a result of As segregation at lattice defects; in particular, the one located the position of the maximum of nuclear energy loss is the consequence of segregation of As atoms at voids, which are formed during irradiation at elevated temperature. The second relevant effect is the formation of a deep penetrating tail in the As profile, which cannot be explained by a simple thermal diffusion mechanism. Although the contribution of channeling effects cannot be ruled out, the effect seems to be mainly related to a diffusivity enhancement, weakly temperature dependent, due to the interaction of the dopant with radiation‐induced defects.
Reference CIME-ARTICLE-1997-003View record in Web of Science Record created on 2007-02-15, modifi... more Reference CIME-ARTICLE-1997-003View record in Web of Science Record created on 2007-02-15, modified on 2017-05-12
MRS Proceedings, 1985
ABSTRACTSome renarks about the mechanism for dynamic annealing during high dose rate P implantati... more ABSTRACTSome renarks about the mechanism for dynamic annealing during high dose rate P implantation of Si are reported. TEM observations and RBS channeling measurements show that the ion bombardment enhances the amorphous to crystalline transformation in the temperature range 200 ≤ T ≤ 600°C. It is found that the ratio between the observed recrystalli-zation velocity and the thermal SPE velocity decreases with increasing temperature. This indicates that a transition temperature must exist between the ion-assisted recrystallization regime and the ?lermal SPE regime. For the energy (100 keV) and the dose rate (60,uA/cm2) used in our experiments the transition temperature is about 700°C.
MRS Proceedings, 1988
ABSTRACTSolid-phase epitaxy of implanted Si is observed at room temperature during in situ electr... more ABSTRACTSolid-phase epitaxy of implanted Si is observed at room temperature during in situ electron irradiation in a Transmission Electron Microscope. Results obtained from irradiation of cross sections of samples containing different doping species show that: i) the basic mechanism of the process is the migration and recombination at the amorphous-crystalline interface of radiation defects coming both from the amorphous and crystalline side; ii) the diffusion length of such defects is of the order of 40 nm; iii) the regrowth rate is impurity dependent: a factor two exists between the faste
Fourth E.C. Photovoltaic Solar Energy Conference, 1982
Experiments were performed to examine two techniques for annealing solar cells. P(+) ions were im... more Experiments were performed to examine two techniques for annealing solar cells. P(+) ions were implanted, followed by e-beam annealing using a new electron gun with a beam width that can be varied, thereby eliminating the necessity for scanning. Other trials were run using a 50 W/sq cm ion beam for the implantation, thereby reaching a cell temperature of 1300 C,
physica status solidi (a), 1986
physica status solidi (a), 1986
BY M. BERTI (a), A. V. DRIGO (a), G. LULLI (b), P. G. MERLI (b), and M. VITTORI ANTISARI (c) TEM ... more BY M. BERTI (a), A. V. DRIGO (a), G. LULLI (b), P. G. MERLI (b), and M. VITTORI ANTISARI (c) TEM and RBS analysis are made of (100) Si specimens implanted with 100 keV P+ ions at a dose rate of 60 pA/cmz, in order to investigate the mechanism for dynamic annealing. The activation energy for regrowth during ion irradiation is found t o be 0.31 eV, much lower than the value for thermal epitaxy of (1OO)Si. The comparison with samples implanted a t room temperature and annealed with an e-beam of the same power density shows that in the temperature range 230 t o 620 "C and for the irradiation times used in the experiments (t 5 7.6 s), the pure contribution o beam heating to the regrowth process is negligible. This result supports the hypothesis that the mechanism responsible for dynamic annealing during high flux ion implantation is the recombination a t t,he a/c interface of point defects produced by the elastic collision of energetic ions with the target atoms. From the regrowth data it can be deduced that, in this kind of annealing regime, the recrystallization rates in <loo) and (111> directions are of the same order of magnitude. Um den Mechanismus der dynamischen Ausheilung zu untersuchen, werden TEM und RBS-Analyse von (lOO)-Si-Proben durchgefuhrt, die mit 100 keV P+-Ionen und einer Dosisrate von 60 pA/cmz implantiert werden. Die Aktivierungsenergie fur Rekristallisation wahrend Ionenbestrahlung wird z u 0,31 eV, vie1 niedriger als der Wert fur thermische Epitaxis von (100)-Si, bestimmt. Der Vergleich mit bei Zimmertemperatur implantierten und mit einem Elektronenstrahl ausgeheilten Proben rnit derselben Leistungsdichte zeigt, daB im Temperaturbereich 230 bis 620 "C und fur Bestrahlungszeiten in den Experimenten (t 5 7,6 s) der reine Beitrag der Strahlheizung zum RekristallisationsprozeB vernachliissigbar ist. Dieses Ergebnis bestatigt die Hypothese, daS der fur die dynamische Ausheilung wahrend dieser HochflnB-Ionen-Implantation verantwortliche Mechanismus die Rekombination von Punktdefekten an der m/c-Grenzflache ist, die durch elastische StoBe der energiereichen Ionen rnit den Targetatomen hervorgerufen werden. Aus den Rekristallisationswerten kann gefolgert werden, daB bei dieser Art des Ausheilungsregimes dieRekristallisationsraten in (100)-und (11 1)-Richtungen von gleicher GroBenordnung sind.
Philosophical Magazine Letters, 1998
The characterization of defects produced during self-annealing implantation of P + ions in silico... more The characterization of defects produced during self-annealing implantation of P + ions in silicon is of great interest for the realization of good quality p± n junctions in silicon and to understand the peculiarity of beam± solid interactions occurring during implantation performed under the conditions of rather high current and power density. High-resolution electron holography is employed here to study the three-dimensional con® guration of nanometre-size voids obtained by P + ion bombardment of a silicon wafer. Reconstructed phase di erence information has been used to obtain maps in which the phase distribution gives a qualitative topography of the cavity shape as well as quantitative measurements of the depth variations.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
The Rutherford backscattering spectroscopy (RBS) surface height of a pure bulk material can be us... more The Rutherford backscattering spectroscopy (RBS) surface height of a pure bulk material can be used as an absolute standard value to calibrate the detector solid angle. This work presents the results of an international collaboration started at the beginning of 1998 to define the surface height of the RBS spectrum (H0) of Si, amorphized by ion implantation to avoid channeling.
Materials Science Forum, 1998
Materials Science Forum Vols. 264-268 (1998) pp 733-736 Online available since 1998/Feb/01 at www... more Materials Science Forum Vols. 264-268 (1998) pp 733-736 Online available since 1998/Feb/01 at www.scientific.net © (1998) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/MSF.264-268.733 ... All rights reserved. No part of ...
Materials Science Forum, 1996
Physical Review B, 2004
We investigate the application of atomistic models of self-interstitial defects to the simulation... more We investigate the application of atomistic models of self-interstitial defects to the simulation of Rutherford backscattering-channeling ͑RBS-C͒ spectra in ion irradiated Si. By the comparison of simulated and experimental measurements, we verify the ability of different models, either of elementary interstitials or of small clusters, to reproduce experimental spectra measured under different alignment conditions in Si lightly damaged by Si ϩ ion implantation. A model system for RBS-C simulation is built by inserting a distribution of defects in a supercell with size of ϳ10 6 atoms. The system is then structurally relaxed by the application of the classical environment-dependent interatomic potential ͑EDIP͒. After adjusting the defect distribution in order to fit the ͗100͘ RBS-C spectrum, simulations are performed under the other alignment conditions investigated. The scattering factors of defects are then extracted from both experimental and simulated RBS-C spectra and compared. It is shown that the anisotropy of experimental damage is not compatible with a significant presence of random ͑incoherent͒ disorder, but can be reproduced by some of the defect models under consideration: the split-͗110͘ interstitial, the diinterstitial formed by the addition of an interstitial to the split-͗110͘ interstitial, and two different configurations of the four-interstitial aggregate; one formed by two close diinterstitials and the other by the aggregation of four split-͗100͘ interstitials. Due to the different ͗100͘ scattering factors of the four defect configurations which are found to reproduce experimental spectra, there is an inherent uncertainty of a factor of 2 in the estimate of the amount of interstitials by ͗100͘ RBS-C analysis. The agreement between simulations and experiments is remarkable, considering that the method makes use of physical, although empirical, models of defects, where the only adjustable parameter is the absolute concentration of interstitials.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1995
Electron paramagnetic resonance and double crystal X-ray diffraction were used to analyse damage ... more Electron paramagnetic resonance and double crystal X-ray diffraction were used to analyse damage accumulation with dose in silicon implanted at room temperature with B and Si ions at 50 keV and MeV energies. Electron paramagnetic resonance reveals the presence of SCP3 (neutral tetravacancy), D centers (indicative of amorphous Si), and I: centers, which are probably vacancy complexes. The total number of (ZZ + D) centers and the depth integral of the lattice strain determined by X-rays increase sublinearly with increasing dose. The sublinearity is interpreted in terms of dynamic annealing of the defects during implantation. Suggestions are mr,d-to explain the differences observed in the results of Si and B implants.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
Spectra of He ions backscattered from thin (001) Si membranes and bulk Si/SiO2 wafers are analyze... more Spectra of He ions backscattered from thin (001) Si membranes and bulk Si/SiO2 wafers are analyzed with the aid of simulation based on the binary collision approximation. Due to precise control of experimental parameters and detailed fitting of random spectra in thin specimens, the curve of random electronic energy loss per unit length in the energy interval 1.5–3 MeV can
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
Nuclear Instruments and Methods in Physics Research B 112 (I 996) 148-15 I IiYlUM B EISEVIER Beam... more Nuclear Instruments and Methods in Physics Research B 112 (I 996) 148-15 I IiYlUM B EISEVIER Beam Interactions with Materials 8 Atoms
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Atomistic simulation of ion channeling in Si shows that the lattice deformation around point defe... more Atomistic simulation of ion channeling in Si shows that the lattice deformation around point defects, calculated by empirical potentials, gives a significant contribution to the backscattering yield of He ions channeled along major axial or planar directions. This effect, whose amount depends on defect type, beam-alignment condition and model potential used to relax the system, is expected to have consequences on the interpretation of Rutherford backscattering-channeling analysis. A model of structurally relaxed point defects, including split-h1 1 0i interstitials and vacancies, has been applied to the interpretation of multiaxial channeling analysis in the slightly damaged surface region of Si implanted with MeV ions. Despite the simple microscopic structure of damage assumed in the model, the method leads to a significantly better agreement with experiments then the standard models which treat defects as individually displaced atoms in an unperturbed lattice.
Materials Letters, 1986
... 4, number 4 MATERIALS LETTERS June 1986 e-BEAM-INDUCED LATERAL SEEDED EPITAXY OF SILICON ON I... more ... 4, number 4 MATERIALS LETTERS June 1986 e-BEAM-INDUCED LATERAL SEEDED EPITAXY OF SILICON ON INSULATOR R. ANGELUCCI, G. LULLI ... film depends on the energy absorption into the target, proceeding from seed openings to the islands, if the maximum of the ...
Journal of The Electrochemical Society, 1987
Thermally induced defects in CZ silicon are studied, with the aim of identifying the mechanisms r... more Thermally induced defects in CZ silicon are studied, with the aim of identifying the mechanisms responsible for lifetime changes and the role of oxygen in them. For low temperature heatings lifetime can either decrease or increase: a gettering activity of neutral oxygen clusters which participate in the dissociation equilibria of Fe-B pairs is postulated. The effects of pretreatments performed by
Journal of Applied Physics, 1990
ABSTRACT Several electron microscopy techniques were used to investigate in detail the structure ... more ABSTRACT Several electron microscopy techniques were used to investigate in detail the structure of the defects produced by implantation of Si with high current density As+ ion beam under self‐annealing conditions (i.e., with simultaneous damage recovery activated by the transient beam heating). The defects, which display a basic octahedral shape, appear if the irradiation is prolonged after the time for which the transient beam heating has produced the complete crystallization of the previously amorphized surface layer. With increasing irradiation time and temperature they grow up to a maximum diameter of about 20 nm, and concentrate in a band located around the position of the maximum of nuclear energy loss of As+ ions, where a segregation peak of electrically inactive As is developed simultaneously. The results of different microstructural and microanalytical techniques used to investigate the defects (conventional and high resolution electron microscopy, electron holography, and energy dispersion x‐ray microanalysis) give information which leads us to identify them as large vacancy aggregates, or voids, with As atoms segregated in proximity of the inner surfaces. The role of As atoms is likely to reduce the strain energy which a vacancy aggregate is expected to produce in the surrounding lattice.
Journal of Applied Physics, 1989
ABSTRACT Anomalous distribution of As implanted in silicon under self‐annealing conditions (i.e.,... more ABSTRACT Anomalous distribution of As implanted in silicon under self‐annealing conditions (i.e., with simultaneous damage recovery activated by beam heating) has been investigated and discussed. Rutherford backscattering/channeling, transmission electron microscopy, and carrier profiling techniques have been used to analyze the dopant profiles and the microstructure of samples irradiated with 150‐keV As+ ions at a current density of ≂207 μA/cm2, for times of 2, 3, 4, 5, and 6 s. Two relevant effects are observed. The first one consists in the formation of two dopant peaks, electrically inactive, separated by a depletion region at the position of the ion projected range. While the deeper peak disappears with increasing irradiation time, the one located at the maximum of nuclear energy loss grows. Microstructural analysis suggests that both peaks occur as a result of As segregation at lattice defects; in particular, the one located the position of the maximum of nuclear energy loss is the consequence of segregation of As atoms at voids, which are formed during irradiation at elevated temperature. The second relevant effect is the formation of a deep penetrating tail in the As profile, which cannot be explained by a simple thermal diffusion mechanism. Although the contribution of channeling effects cannot be ruled out, the effect seems to be mainly related to a diffusivity enhancement, weakly temperature dependent, due to the interaction of the dopant with radiation‐induced defects.