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Ion beam mixing effects in Ag precipitates embedded in MgO crystals
Classified abstracts 6662-6670 mismatch. The majority of dislocations observed are of the 60* type with Lomer edge type dislocations observed in a much lower concentration. The density of misfit dislocations increases with increasing epilayer thickness. Above about 1/lm the films exhibit biaxial tension which we believe is due to thermal expansion differences of ZnSe and GaAs. Good agreement is observed between microscopic and diffraction measurements of the relaxation phenomena. J Petruzzello et al, J appl Phys, 63, 1988, 229%2303. 33 6662. Growth and luminescence spectroscopy of a CuCI quantum well structure A structure of the type CaF2/CuCI/CaF2 in which the confined layer is 150 A. thick, has been grown on a S i ( l l l ) surface by molecular beam epitaxy in ultrahigh vacuum. The optical properties of the CuC1 film have been characterized by low-temperature photoluminescence as a function of excitation density. Striking differences in the excitonic emissions are observed between the q u a n t u m well structure and a bulk single crystal of CuCI, and are discussed in terms of film purity and thickness. R Stanley Williams et al, J Vac Sci Technol, A6, 1988, 1950 1952.
34. ION BEAM M I X I N G , I N T E R F A C E S A N D SOLID P H A S E REACTIONS 34 6663. Study of the rapid thermal nitridation and silicidation of Ti using elastic recoil detection. I. Ti on Si This paper describes a study of the rapid thermal processing of Ti thin films on Si in Ar and N2 in the temperature range 40~1100°C. The resulting layer structures were analyzed by means of Rutherford backscattering spectrometry and elastic recoil detection. The latter technique yields quantitative information with a low detection limit about the depth distribution of O and N. Rapid thermal annealing in both Ar and N2 results in the uptake of nitrogen in the Ti surface region. Very little oxygen, if any, is incorporated. This nitridation leads to a shift of the originally present oxygen from the surface region into deeper layers, notably at the higher temperatures. For rapid thermal processing (RTP) in both Ar and Nz the evolution of the layer structures is governed by a competition between silicide (TiSi2) formation at the interface and nitridation at the outer surface. For the case o f R T P in N2, the nitride to silicide thickness ratio is considerably larger than for R T P in Ar. The originally present oxygen is found between the silicide and the Ti nitride. In the case of R T P in At, Si appears at the surface at temperatures above 600:~C via diffusion through a thin titanium (oxy) nitride layer. This results in a buried titanium nitride layer via lateral overgrowth of Si on a nanoscale. This silicon surface layer effectively stops further nitridation. G J P Krooshof et al, Jappl Phys, 63, 1988, 5104-5109. 34 6664. Thermal behavior and range distribution of 2°9Bi implanted into the AI/V bilayer structure 350-keV 2°9Bi+ was implanted into an AI (1000 A,)/V bilayer system. The Bi depth distribution measured by Rutherford backscattering agrees well with predictions obtained via the Monte-Carlo simulation method (TRtM code). Diffusion coefficients for Bi in both the V substrate of the A1/V system and the pure V foil are extracted after thermal annealings in a temperature range between 200 and 700°C. The results show that the Bi ions follow a hindered diffusion at the AI film of the AI/V bilayer and for temperatures higher than 580°C diffuse regularly in the V bulk. C A Olivieri et al, Jappl Phys, 63, 1988, 4431-4434. 34 6665. Pt4Si 9 formation by hot substrate ion beam mixing Direct, ion induced formation of metastable c o m p o u n d s in the Pt Si system has been investigated by implantation with Xe ions through the PtSi-Si interface in the temperature range of 3 5 325°C. The mixing increased parabolically with dose and exhibited an exponential dependence on reciprocal temperature with an apparent activation energy of about 0.11 eV. The mixed layer became progressively uniform in composition with increasing temperatures and a well-defined surface layer with a composition of Pt4Si9 was obtained at relatively high temperatures. The Pt4Si9 phase was indexed as a hexagonal crystal structure and transformed back into PtSi and Si at temperatures above 550°C by thermal steady-state annealing. L S Hung et al, Jappl Phys, 63, 1988, 46514654. 514
34 6666. Structural eharacterizatun of GaAs/ZnSe interfaces We have studied, using reflection high energy electron diffraction (RHEED), the initial growth stages of ZnSe layers grown by molecular beam epitaxy (MBE) on G a A s exhibiting various surface terminations. The structural quality o f the ZnSe layers was assessed by transmission electron microscopy (TEM). We have observed a preference for twodimensional nucleation on As-terminated GaAs substrates, whether epitaxial or bulk. On Ga-terminated surfaces a transitional region of threedimensional growth forms initially. The different behaviors m a y reflect the electronic imbalance present in the growing G a A s / Z n S e interface. While defect free, thin layers of ZnSe are best obtained on As-terminated GaAs, the initial three-dimensional growth region on the Ga-rich surfaces appears to reduce the density of extended faults formed in thick ZnSe layers due to the lattice mismatch with GaAs. M C Tamargo et al, J Vac Sci Technol, B6, 1988, 784-787. 34 6667. Studies of Co/Gal_xAIxAs interfaces fabricated in ultrahigh vacuum The reactions of in situ U H V fabricated and annealed Co/Gat ~AlxAs structures for x - 0 1 have been studied using a number of elemental and structural techniques. Cobalt starts to react with Ga~_xAlxAs at 370°C and forms a quarternary phase of approximate composition Co2Ga~_xAlxAs. The variation in Schottky barrier heights for reacted Co/Ga~ xAlxAS is not consistent with the Fermi-level pinning position predicted from Tersoff's model for metal induced gap states. However, it is consistent with the effective work function model after consideration of the interface composition and Fermi-level pinning by defects at the reacted layer/Ga~ ,.AlxAs interface. C J Palmstrq~m et al, J Vac Sci Technol, A6, 1988, 1456-1461. 34 6668. Ion beam mixing of metal-sapphire interfaces Thin films of Au, Ag have been evaporated on (0001) surface of sapphire and then the interfaces were irradiated with xenon ions. Ion energy of 1.5 MeV, fluences of 3 × l0 ts to 2.2 × 1016 ions cm 2 and irradiation temperatures at 77 and 300 K were used. The evolutions of the interfaces were studied by different techniques such as Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM), optical absorption, X-ray diffraction at glancing incidence and electrical resistivity measurements. Blistering is observed for all specimens bombarded with fluences as low as 3 x 1015 ions cm ~. The RBS analysis seems to show a ballistic mixing at Ag or Au A120 3 interfaces but X-ray diffraction at glancing incidence does not reveal any new c o m p o u n d formation at the interfaces. Nevertheless optical absorption shows the formation of silver or gold metallic precipitates embedded into A1203. L Romana et al, Nucl Instrum Meth Phys Res, B32, 1988, 96-99. 34 6669. Ion beam mixing effects in Ag precipitates embedded in M g O crystals M g O single crystals have been implanted at room temperature with 8 x 10 ~6Ag cm 2 of 180 keV energy. After 973 K thermal annealing, Ag atoms precipitate in the M g O matrix. The M g O Ag samples were then irradiated at 77 K with 800 keV xenon up to 1.7 × 10 ~6 ions cm -2. The modification of the metallic precipitated phase induced by such ionic bombardment, has been characterized by optical absorption spectroscopy (OAS) and transmission electron microscopy (TEM). The evolution of the optical spectra with xenon b o m b a r d m e n t has been interpreted in terms of silver precipitate dispersion induced by ion beam mixing effects. The inhibition of atomic diffusion or radiation induced diffusion, due the low sample temperature during irradiation, increases the efficiency of atomic mixing effects. T E M observations confirm this assumption. G Fuchs et al, Nucl lnstrum Meth Phys Res, B32, 1988, 100 103. 34 6670. Rapid thermal annealing of InP using GaAs and lnP proximity caps Rapid thermal annealing of lnP in an inert atmosphere is demonstrated using face-to-face G a A s and InP proximity caps to protect the active surface from decomposition. No surface damage of any kind is detected by optical microscopy, photoluminescence spectroscopy, or R a m a n scattering on samples annealed for 4 s at temperatures up to 850°C. As application, the rapid thermal annealing o f Si-implanted InP samples is carried out. Full activation of the implanted species is obtained at annealing temperatures of 850c'C. Rapid thermal annealing of InP using a G a A s proximity cap promises to be a practical technology for the fabrication of semiconductor devices based on lnP.
34. ION BEAM M I X I N G , I N T E R F A C E S A N D SOLID P H A S E REACTIONS 34 6663. Study of the rapid thermal nitridation and silicidation of Ti using elastic recoil detection. I. Ti on Si This paper describes a study of the rapid thermal processing of Ti thin films on Si in Ar and N2 in the temperature range 40~1100°C. The resulting layer structures were analyzed by means of Rutherford backscattering spectrometry and elastic recoil detection. The latter technique yields quantitative information with a low detection limit about the depth distribution of O and N. Rapid thermal annealing in both Ar and N2 results in the uptake of nitrogen in the Ti surface region. Very little oxygen, if any, is incorporated. This nitridation leads to a shift of the originally present oxygen from the surface region into deeper layers, notably at the higher temperatures. For rapid thermal processing (RTP) in both Ar and Nz the evolution of the layer structures is governed by a competition between silicide (TiSi2) formation at the interface and nitridation at the outer surface. For the case o f R T P in N2, the nitride to silicide thickness ratio is considerably larger than for R T P in Ar. The originally present oxygen is found between the silicide and the Ti nitride. In the case of R T P in At, Si appears at the surface at temperatures above 600:~C via diffusion through a thin titanium (oxy) nitride layer. This results in a buried titanium nitride layer via lateral overgrowth of Si on a nanoscale. This silicon surface layer effectively stops further nitridation. G J P Krooshof et al, Jappl Phys, 63, 1988, 5104-5109. 34 6664. Thermal behavior and range distribution of 2°9Bi implanted into the AI/V bilayer structure 350-keV 2°9Bi+ was implanted into an AI (1000 A,)/V bilayer system. The Bi depth distribution measured by Rutherford backscattering agrees well with predictions obtained via the Monte-Carlo simulation method (TRtM code). Diffusion coefficients for Bi in both the V substrate of the A1/V system and the pure V foil are extracted after thermal annealings in a temperature range between 200 and 700°C. The results show that the Bi ions follow a hindered diffusion at the AI film of the AI/V bilayer and for temperatures higher than 580°C diffuse regularly in the V bulk. C A Olivieri et al, Jappl Phys, 63, 1988, 4431-4434. 34 6665. Pt4Si 9 formation by hot substrate ion beam mixing Direct, ion induced formation of metastable c o m p o u n d s in the Pt Si system has been investigated by implantation with Xe ions through the PtSi-Si interface in the temperature range of 3 5 325°C. The mixing increased parabolically with dose and exhibited an exponential dependence on reciprocal temperature with an apparent activation energy of about 0.11 eV. The mixed layer became progressively uniform in composition with increasing temperatures and a well-defined surface layer with a composition of Pt4Si9 was obtained at relatively high temperatures. The Pt4Si9 phase was indexed as a hexagonal crystal structure and transformed back into PtSi and Si at temperatures above 550°C by thermal steady-state annealing. L S Hung et al, Jappl Phys, 63, 1988, 46514654. 514
34 6666. Structural eharacterizatun of GaAs/ZnSe interfaces We have studied, using reflection high energy electron diffraction (RHEED), the initial growth stages of ZnSe layers grown by molecular beam epitaxy (MBE) on G a A s exhibiting various surface terminations. The structural quality o f the ZnSe layers was assessed by transmission electron microscopy (TEM). We have observed a preference for twodimensional nucleation on As-terminated GaAs substrates, whether epitaxial or bulk. On Ga-terminated surfaces a transitional region of threedimensional growth forms initially. The different behaviors m a y reflect the electronic imbalance present in the growing G a A s / Z n S e interface. While defect free, thin layers of ZnSe are best obtained on As-terminated GaAs, the initial three-dimensional growth region on the Ga-rich surfaces appears to reduce the density of extended faults formed in thick ZnSe layers due to the lattice mismatch with GaAs. M C Tamargo et al, J Vac Sci Technol, B6, 1988, 784-787. 34 6667. Studies of Co/Gal_xAIxAs interfaces fabricated in ultrahigh vacuum The reactions of in situ U H V fabricated and annealed Co/Gat ~AlxAs structures for x - 0 1 have been studied using a number of elemental and structural techniques. Cobalt starts to react with Ga~_xAlxAs at 370°C and forms a quarternary phase of approximate composition Co2Ga~_xAlxAs. The variation in Schottky barrier heights for reacted Co/Ga~ xAlxAS is not consistent with the Fermi-level pinning position predicted from Tersoff's model for metal induced gap states. However, it is consistent with the effective work function model after consideration of the interface composition and Fermi-level pinning by defects at the reacted layer/Ga~ ,.AlxAs interface. C J Palmstrq~m et al, J Vac Sci Technol, A6, 1988, 1456-1461. 34 6668. Ion beam mixing of metal-sapphire interfaces Thin films of Au, Ag have been evaporated on (0001) surface of sapphire and then the interfaces were irradiated with xenon ions. Ion energy of 1.5 MeV, fluences of 3 × l0 ts to 2.2 × 1016 ions cm 2 and irradiation temperatures at 77 and 300 K were used. The evolutions of the interfaces were studied by different techniques such as Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM), optical absorption, X-ray diffraction at glancing incidence and electrical resistivity measurements. Blistering is observed for all specimens bombarded with fluences as low as 3 x 1015 ions cm ~. The RBS analysis seems to show a ballistic mixing at Ag or Au A120 3 interfaces but X-ray diffraction at glancing incidence does not reveal any new c o m p o u n d formation at the interfaces. Nevertheless optical absorption shows the formation of silver or gold metallic precipitates embedded into A1203. L Romana et al, Nucl Instrum Meth Phys Res, B32, 1988, 96-99. 34 6669. Ion beam mixing effects in Ag precipitates embedded in M g O crystals M g O single crystals have been implanted at room temperature with 8 x 10 ~6Ag cm 2 of 180 keV energy. After 973 K thermal annealing, Ag atoms precipitate in the M g O matrix. The M g O Ag samples were then irradiated at 77 K with 800 keV xenon up to 1.7 × 10 ~6 ions cm -2. The modification of the metallic precipitated phase induced by such ionic bombardment, has been characterized by optical absorption spectroscopy (OAS) and transmission electron microscopy (TEM). The evolution of the optical spectra with xenon b o m b a r d m e n t has been interpreted in terms of silver precipitate dispersion induced by ion beam mixing effects. The inhibition of atomic diffusion or radiation induced diffusion, due the low sample temperature during irradiation, increases the efficiency of atomic mixing effects. T E M observations confirm this assumption. G Fuchs et al, Nucl lnstrum Meth Phys Res, B32, 1988, 100 103. 34 6670. Rapid thermal annealing of InP using GaAs and lnP proximity caps Rapid thermal annealing of lnP in an inert atmosphere is demonstrated using face-to-face G a A s and InP proximity caps to protect the active surface from decomposition. No surface damage of any kind is detected by optical microscopy, photoluminescence spectroscopy, or R a m a n scattering on samples annealed for 4 s at temperatures up to 850°C. As application, the rapid thermal annealing o f Si-implanted InP samples is carried out. Full activation of the implanted species is obtained at annealing temperatures of 850c'C. Rapid thermal annealing of InP using a G a A s proximity cap promises to be a practical technology for the fabrication of semiconductor devices based on lnP.