Interstitial Agglomerates Research Articles

Unusual strain relaxation in SiGe/Si heterostructures

Si 1−x Ge x films (x=0.22) epitaxially grown by ion beam-sputter deposition on (001) Si substrates were subjected to rapid and conventional thermal annealings at different temperatures. Strain measurements carried out by means of high-resolution x-ray diffraction exhibited strongly nonmonotonous strain dependencies on the annealing time. We observed short-time and long-time relaxation modes with activation energies of 4.6 and 1.3 eV, respectively, and unexpectedly, an additional mode of strain recovery at intermediate time durations with an activation energy of 1.6 eV. This behavior was attributed to processes that involve {113} two-dimensional defects, i.e., agglomerates of interstitials, which were identified by means of transmission electron microscopy.

Dynamic crowdions, interstitials and vacancies in copper

Abstract We determined the increase of the electrical resistivity in copper, Be doped copper, and in gold during irradiation with 1.85 MeV electrons below the temperature corresponding to the stage III recovery region. From the analysis of these data by means of rate equations we are able to determine the variations of the concentrations of interstitials, vacancies and agglomerates of interstitials as a function of the irradiation time and of the irradiation temperature. The number of replacement collision sequences of dynamic crowdions is about N = 4.104 before they convert into stable interstitials in well annealed pure copper, in commercial copper, and in pure gold. This number decreases with beryllium additions and is about N = 15 in copper doped with 763 ppm beryllium. The rate of spontaneous annihilation of vacancies with dynamic crowdions during irradiation depends on the number of replacement collisions sequences. Thus the production rate of vacancies and interstitials decreases in pure materials with increasing irradiation time considerably. However, the production rate of dynamic crowdions does not decrease with increasing irradiation time, i.e. with increasing concentrations of vacancies and interstitials and is equal to the initial production rate of interstitials. The initial production rate of point defects is the production rate determined for zero defect concentrations. The recovery of the stages III and IV were investigated for copper containing 763 ppm beryllium. After small irradiation doses mainly recovery stage III and after high irradiation doses mainly recovery stage IV is observed. For these two recovery stages activation energies of (0.72 ± 0.05) eV and (1.07 ± 0.05) eV are determined and attributed to the migration activation energies of interstitials and vacancies, respectively. These values are only very slightly larger than the ones determined for pure copper. Thus the migration activation energy of copper and beryllium in the dumbbell configuration is very similar to that of self-interstitials in pure copper and the binding energy of beryllium to vacancies must be very small.

Diffusion Process Of Interstitial Atoms In Inp Studied By Transmission Electron Microscopy

AbstractIt is found that interstitial agglomerates are formed uniformly in an irradiated area of InP by annealing at the temperature above 700 K after 200 keV-electron irradiation. TEM observation shows that the number density of interstitial atoms in the agglomerates reached a maximum value when the growth of all the agglomerates stopped. The final density did not depend on annealing temperature but on electron dose, and it increased quadratically with electron dose up to 2×1022 cm−2. In order to explain the experimental results, we have proposed a new model that the agglomerates are formed by thermal diffusion and agglomeration of interstitial-pairs, i.e. Ini-Pi interstitial-pairs. From the analysis, the migration energies for the pairs are estimated to be 1.52 eV. The onset temperature for the diffusion of the pairs is estimated as 550 K.

Implant damage and transient enhanced diffusion in Si

Transmission electron microscopy is used to address two key questions for ion-implant technology in Si. First, how does ion damage influence the diffusion of implanted dopants: and, second, when and how does damage evolve into extended dislocations seen after prolonged anneals. The answer to both questions turns out to involve “{311} defects”, the interstitial agglomerates also known as “rod-like defects”. At low doses, {311} defects evaporate during annealing, and emit interstitials. The characteristic time for the decay of {311}s, and its activation energy of 3.6 ± 0.1 eV, relate precisely with the observed duration of the burst of interstitials seen in accurate diffusion measurements. We also use {311} counting to assess the accuracy of the “plus one” approximation for the excess interstitials seen after implantation. At higher doses, the {311} defects can also undergo a series of unfaulting reactions. In contrast to earlier reports on {311}s formed during electron irradiation, we observe that {311}s initially “unfault” to yield Frank loops, followed by unfaulting of Frank loops to give a 2〈110〉 s . We relate our observations for a “phase diagram” for {311} behaviour to earlier studies of dislocation loop formation.

High resolution electron microscopy of semiconductor interfaces

Results are presented of high resolution electron microscope (HREM) investigations of atomic structure of semiconductor epitaxial systems. For the GaAs/AlAs epitaxial systems the different atomic scale roughness is detected. This may result in morphological instability of a growing surface for the given system. For InGasAs/InP and InSb/GaAs systems the data on structure and origin of threading dislocations are presented. Examples of laterally defined semiconductor microstructure fabrication on the basis of III-V epitaxial structures to study their quantum properties are presented. The structure transformation of a Frank partial dislocation core in Si during electron irradiation in HREM is investigated and the atomic model of irradiation induced interstitial agglomerates is discussed. [Russian Text Ignored].

Dislocation formation in silicon implanted at different temperatures

The formation of pre-amorphization damage, i.e. dislocations formed by the agglomeration of silicon interstitials, requires a minimum amount of implant damage. The amount of damage can be altered by changing the implant temperature or current density, which can influence dislocation formation. We studied this using cross-sectional transmission electron microscopy for boron and indium implants at kiloelectronvolt and megaelectronvolt energies respectively. Dislocation formation for boron implants, where only simple cascade densities are generated, does not depend on implant temperature or current density. For 1 MeV indium implants, where the implant damage consists mainly of amorphous zones, an increase in critical dose for dislocation formation by a factor of approximately 3 is observed if the implant temperature is raised. This is attributed to the interaction of point defects with the amorphous zones during the elevated temperature implant. Implants of 150 keV indium at room temperature result in complete amorphization before the critical amount of crystal damage is reached. Here, end-of-range loops (EOR-loops) from after annealing. Increasing the implant temperature suppresses amorphization, and pre-amorphization damage is observed if a critical amount of crystal damage has been generated. EOR-loop formation results from the agglomeration of silicon interstitials from the amorphous-crystalline transition region. If the number of interstitials in this region is lowered by carrying out the implant at low temperature, EOR-loop formation can be suppressed. This is shown by comparing amorphizing germanium implants done at room and liquid nitrogen temperatures.

Correlation of interstitials within defect cascades in Al(Zn) and Cu observed by diffuse X-Ray scattering

The correlation of interstitials in displacement cascades in Al-1000 ppm Zn and Cu after low temperature fast neutron irradiation was studied by Huang diffuse scattering of X-rays. The Fourier transform of the defect correlation was analyzed in terms of a cascade size distribution taking into account the energy spectrum of the primary knocked on atoms. In Al(Zn) very dilute cascades with a mean radius of 〈 A c 〉 = 9.3 nm, and a mean interstitial concentration of 〈 c i 〉 = 360 ppm are found. No evidence for appreciable agglomeration of interstitials within a single cascade was observed. In Cu dense cascades with 〈 R c 〉 = 2.2 nm and 〈 c i 〉 ≈ 4000 ppm are found. Here large agglomerates of interstitials are formed spontaneously.

Octahedral defects in a b.c.c. lattice examined by lattice theory

Displacements of atoms, induced by single or multiple interstitials located at octahedral sites in a b.c.c. lattice, were examined using an eigenstrain method in lattice theory with the harmonic approximation. It is shown that the assignment of proper eigenstrains yields the correct magnitude of the potential energy for hydrogen, carbon and nitrogen in α-iron. It is also shown that the precipitate structure of Fe 16N 2 proposed by Jack takes a minimum potential energy among various kinds of plausible interstitial agglomerates.

Diffuse X-Ray Scattering Studies of n and e<sup>-</sup>-Irradiated Ni and Dilute Ni Alloys

Pure Ni and dilute NiSi and NiGe alloys were irradiated at 6 K with either fast neutrons or 3 MeV electrons. The resulting defect structures were studied using diffuse x-ray scattering methods after different annealing treatments. For both types of irradiation of pure Ni, large interstitial and vacancy dislocation loops developed on annealing. In contrast, interstitial agglomerates in a NiSi/sub .01/ alloy contained no more than approx. =10 interstitials, and few vacancy loops were observed. Complete recovery was observed at lower temperatures in the alloy. Similar results were found for NiGe/sub .01/, although larger interstitial clusters were observed. The results are discussed within the model for the trapping reactions developed previously to explain the results of e/sup -/ irradiation of these same alloys.

Recent Advances in Huang Diffuse Scattering

AbstractMeasurements of the diffuse X-ray (or neutron) scattering allow the detailed investigation of point defects in crystalline solids. The method can be applied for defect sizes ranging from isolated point defects up to large dislocation loops. The diffuse scattering intensity close to the Bragg reflections, Huang Diffuse Scattering and Asymptotic Diffuse Scattering, is of special interest as the intensities from lattice distorting defects are high and the scattering theory is most straightforward for this region of the reciprocal lattice. After a short introduction to the theoretical background and to the experimental techniques the capabilities and limitations of the method will be demonstrated with examples of experimental results. i) The structure of interstitial atoms has been investigated for low temperature irradiated crystals and for metals with interstitially dissolved solute atoms. ii) The mobility and growth of interstitial agglomerates during annealing stage II of irradiated metals is discussed. The influence of impurities on the cluster growth is demonstrated for the example of Nibase alloys. iii) Defect clusters and defect distributions within cascades as observed after different types of irradiations are discussed.

Carbon in silicon: Properties and impact on devices

The properties, origin and analysis of carbon in silicon and its influence on the electrical characteristics of devices are investigated and reviewed. The typical carbon concentrations in electronic-grade silicon are still some 10 16 cm −3. The small distribution coefficient ( k 0 = 0.058) causes an inhomogeneous incorporation of carbon along the crystal axis and across the crystal diameter during crystal growth. Carbon concentrations exceeding about 5 × 10 16 cm −3 in float-zoned silicon can lead to the formation of process-induced defects in the fabrication of power rectifiers and thyristors. These defects which are frequently arranged in a swirl-like pattern strongly deteriorate the electrical characteristics of these devices. It is shown that carbon is involved primarily in the generation of the defect nuclei whereas the defects finally observed form via precipitation of oxygen and agglomeration of silicon interstitials. Reasons for the benign behavior of high carbon concentrations in the processing of integrated circuits are discussed. In powder device processing the formation of carbon-induced defects is safely avoided by application of silicon containing carbon less than 5 × 10 16 cm −3.

Investigation of neutron-irradiated silicon by diffuse X-ray scattering

Single crystals of silicon were irradiated with neutron doses from 2.5 × 10 18 n cm −2 up to 2.5 × 10 19 n cm −2 (E > 0.1 MeV). X-ray diffuse scattering from the irradiated samples was measured near the (440) reflection. A combination of the lattice parameter change, Huang scattering and Stokes-Wilson scattering yields the relative volume change per interstitial (Δυ/Ω) I = + 0.55 and per vacancy (Δυ/Ω) V = −0.50 . The average degree of agglomeration of the vacancies is Z v = 3 and is nearly dose independent in the above dose range. The size of the interstitial agglomerates Z I depends strongly on the irradiation dose and varies from 6 to 18 in the same dose range as above.

Investigation of electron-irradiated cadmium by diffuse X-ray scattering

Abstract The change of the diffuse scattering intensity near (OO.h) and (hO.O) Bragg reflections and the electrical resistivity change were investigated at single crystals of cadmium after electron-irradiations (3 MeV) at 4.5 K. Even for the lowest irradiation dose no isolated interstitials but interstitial agglomerates were found at 6K. Their size grew with increasing irradiation dose from 6 (Δρ = 14 nΩm) to 9 (Δρ = 25 nΩm) interstitials per agglomerate. During recovery stage II (to ∼ 100 K.) their size further increased by a factor of about 1.5. These clusters seemed to approach the form of dislocation loops on the basal plane. At the end of stage HI (∼ 145 K) there were indications for the formation of vacancy agglomerates.

Investigation of frenkel defects in low-temperature e −-irradiated mg by diffuse x-ray scattering

Abstract Mg single crystals were irradiated with 3 MeV electrons at 4.5 K producing electrical resistivity changes varying between 83 and 232 nΩcm. Diffuse X-ray scattering measured at (00.h) and (h0.0) or (hh.0) Bragg reflections showed defects with a large relaxation volume of ΔV rel ≈ 5 atomic volumes and a very anisotropic long range displacement field. Contrary to hcp Zn and Cd, these displacements were larger within the basal plane than along the c-direction. Although it cannot be definitely excluded that these parameters describe the self-interstitial atom in the crowdion configuration, a more consistent explanation of all results is obtained with the assumption that agglomerates of 2–3 interstitials are formed by interstitial migration during the 4.5 K irradiation. In contrast to stage II irradiations of other metals no dose dependence of the agglomerate size was found. This unique behaviour is explained by a nucleation barrier for the interstitial agglomerates at the irradiation temperature. Duri...

Elektronenmikroskopischer kontrast kleiner fehlstellenagglomerate in ionenbestrahltem kupfer

Abstract ELECTROS MICROSCOPY CONTRAST OF SMALL DEFECT CLUSTERS IN ION–IRRADIATED COPPER Systematic investigations were performed on the dependence of the contrast of small vacancy agglomerates, interstitial agglomerates and gas bubbles on TEM imaging conditions. The studies were made on copper foils bombarded with 5 keV argon ions. Agglomerates with diameters of 1–2 nm were most easily visible under dynamical dark–field conditions. Exceptions to the regular contrast behaviour were detected in very thin regions of the specimen (i.e. a reversal of the direction of tho black-white contrasts). The different experimental observations arc discussed critically and hints are given on the practical imaging of small defect agglomerates.

The configuration of atomic defects as determined from scattering studies

Atomic defects such as vacancies and interstitials in crystalline solids produce elastic diffuse scattering of X-rays or neutrons. The distribution in reciprocal space of the diffuse scattering intensity contains very direct information about the atomic structure of point defects, and it sensitively shows the formation of defect clusters. Three domains of the scattering are distinguished: (a) scattering in the forward direction (small-angle scattering); (b) scattering between the Bragg reflections; and (c) scattering close to the Bragg reflections (Huang scattering). The specific features of the information obtained from measurements in the different domains are discussed. Experimental results on the structure of interstitials in metals have been obtained after low temperature electron irradiation of the fcc metals Al and Cu, bcc Mo, and hcp Zn. In other metals (Au, Nb, Cd, Mg) the agglomeration of interstitials was observed during electron irradiation at 5 K.

Quantitative transmission electron microscopy of small agglomerates in HF-O

High amounts of gases or carbon are soluble on interstitial sites of the hexagonal lattice of hafnium. The gas atoms influence nearly all physical properties; e.g., the critical resolved shear stress τ (CRSS) is drastically increased with an increasing content of gas atoms. Different authors measured the temperature dependence of τ for different 0 concentrations (cO ≲ 1.5 at%). The CRSS increases strongly with decreasing measuring temperature T. Ruano and Elssner concluded intuitively from the non continious shape of the τ-T curve, that besides the interstitially solved single gas atoms also agglomerates of gas atoms should be present in the specimens. These agglomerates act as strong barriers against plastic deformation. - A superposition of the 2 types of barriers (single interstitial gas atoms and agglomerates) could explain the shape of the τ-T curve. TEM studies were performed to prove this assumption of the existence of agglomerates. Hafnium specimens with different 0 content (0.13, 0.65 and 1.17 at%0) were electrolytically thinned and investigated with a Siemens ELMISKOP 102 operated at 125 kV.

The creation of F centers in lithium fluoride between 77° and 600°K and their interpretation by a recombination model of interstitial-vacancies

In pure LiF crystals, the number of F centers generated by X-ray irradiation between 200° and 600°K is proportional to the square root of the irradiation time. At room temperature, for the same irradiation time, the number of F centers increases proportionately to the square root of the radiation intensity. At irradiation temperatures higher than 400°K a fraction of F centers clusters to form large agglomerates observable by small angle X-ray scattering. One assumes that the radiation creates KI Frenkel pairs per unit time ( I being the radiation intensity) and that interstitials thus created diffuse towards F centers or towards traps which are assumed to be agglomerates of interstitials: the calculation leads to a generation law of F centers proportional to (It) 1 2 in good agreement with experimental results. One thus verifies this model by studying the disappearance of M centers by X-ray irradiation below 250°K: such a bleaching occurs through trapping of free interstitials by these centers.

The penetration of lattice defects in copper and gold foils bombarded with 1–5 keV argon ions

Single crystalline copper and gold foils are bombarded with 1–5 keV argon ions. Transmission electron micrographs of the bombarded foils show black spots, which are caused by small interstitial agglomerates. Measurements of the spatial distribution of these agglomerates, carried out by means of a special stereo technique, indicate that the average distance of the agglomerates from the bombarded surface is much higher than the calculated range of the Ar ions. From the variation of the depth distribution of the agglomerates with the orientation of the foil and with the ion energy, it is concluded that the interstitial atoms, which form the agglomerates, penetrate into the lattice by means of focusing collisions. Tentative conclusions on the ranges of the focusing collision chains which transport matter (dynamic crowdions) are discussed.

Study of Agglomerated Defects in Irradiated Pure Nickel by Electron Microscopy

AbstractPure nickel foils are neutron and electron irradiated. In both cases black dots are observed by electron microscopy. After neutron irradiation at 77 °K and subsequent annealing at room temperature the larger dots are found to be interstitial Frank dislocation loops. The smaller ones (<15 Å) are vacancy agglomerates in the form of tetrahedral voids. Investigation of dose dependence and further annealing is also presented. After electron irradiation at 10 °C only interstitial Frank dislocation loops are visible for doses larger than 4 × 1019 electrons/cm2 at 2 MeV. Discussion of nucleation and agglomeration of free interstitials is presented, showing that the elastic interaction between loops plays an important role.