The atomic structure of ion-sputtered Fe/Ti multilayers with an average composition FeTi2 is studied by high resolution electron microscopy. A systematic use of diffractometry is made to measure the local parameter change as well as to recognise the crystalline phase. Local lattice parameter changes are attributed to compositional changes indicating interdiffusion at a scale of 1.8 nm. The phases are very dependent on the multilayer period, Λ. For small periods, Λ < 4 nm, the layers are amorphous. For intermediate periods 4 nm < Λ < 8 nm the Ti-rich layer is crystalline. And for larger periods both the Fe-rich and the Ti-rich layers are crystalline. These observations are explained in terms of a growth model, assuming a constant depth of mixing during sputtering.

The coupling of HRTEM with atomistic calculations is described for the study of grain boundaries and dislocations in aluminum. HRTEM images of the Σ9 (221) [110] grain boundary are compared with molecular statics calculations using both the Embedded Atom Method (EAM) and two pair potentials. Comparison between observed and simulated images are shown to serve as a stringent test of the theoretical methods. Atomistic calculations can in turn provide threedimensional information about the defect structure. Using the EAM, it is also possible to account for the effects of thin foil geometries on the minimim energy configuration of defects. While these effects are found to be minimal for grain boundary structures, the influence of the thin-foil geometries on the core structure of the 60° dislocation in aluminum is discussed. These comparisons indicate that the EAM function provides a good description of grain boundary structures, but fails to reproduce the observed dislocation core structure due to a low predicted value of the intrinsic stacking fault energy (SFE) on the (111). In contrast, the pair potentials used in this study provide reasonable SFE values, but appear to be less accurate for the prediction of the Σ9 (221) [110] grain boundary structures.

Recent results are presented which indicate that the core structure of anti-phase boundaries is sensitive to changes in temperature and alloy composition. Isolated anti-phase boundaries in CoPt3 are found to undergo a structural change when the order-disorder transition temperature is approached from below. Periodic anti-phase boundaries of the long period structures in Cu3Pd, Au3Zn and Au3Cu exhibit similar phenomena. Detailed results on the core structure of periodic boundaries in alloys annealed close to the order-disorder transition are compared to the results of a Monte Carlo analysis for finite temperatures of (100) anti-phase boundaries in L12 alloys.

While in heterophase systems of small lattice parameter differences, misfit dislocations are often formed at the interface, it is not known, whether and in which form, misfit localization occurs when the misfit is very large. The atomic structure of Ag/Ni interfaces (misfit 14%) was studied by high-resolution electron microscopy (HREM). A special technique was developed to prepare interface specimens suitable for HREM observations.

Lattice statics calculations, using embedded-atom potentials, were performed to determine the structure and energies of Ag/Ni interfaces. The lowest interfacial energy was found for the cube-on-cube orientation and (111) interfaces. This is in agreement with the experimental observation, that all interfaces are strongly faceted with (111)Ag/(111)Ni facets.

Misfit localization was found by HREM and computer simulation. The HREM observations will be compared to images derived from image simulations, based on model structures obtained from embedded atom calculations.

An experimental high resolution image of a grain boundary has been compared with images simulated from atomic structures calculated by two theoretical methods. Some of the techniques used in the analysis of the images are presented. A good agreement is found between each theory and the experiment, confirming the validity of calculations of such a boundary.

The structure of the Cu/MnO interface has been studied using high resolution electron microscopy (HRTEM). Interfaces were formed by internal oxidation of a CuMn alloy. In the course of the reaction, MnO particles precipitate in several special orientations relative to the Cu lattice: “parallel” topotaxy, “twin” topotaxy, and a 55°[110] rotation yielding (111)Cu∥(002)MnO. Each of the three Cu/MnO orientation relationships has a characteristic particle morphology reflecting thermodynamically favourable interface structures. In parallel topotaxy MnO particles preferentially form flat {111}Cu/{111} MnO interfaces with a lattice mismatch of 21%. Although this mismatch is large, the existence of coherence strains in the Cu cannot be excluded. MnO particles in the 55°[110] orientation form regions of semi-coherent Interface where {200}MnO planes face a set of parallel {111} Cu planes with a mismatch of only 6%. This interface variant exhibits equally spaced steps, every 16 to 18 Cu {111} planes. Parallel to every step there is a misfit dislocation in the Cu at a stand-off distance of about 2 Cu {111} spacings. The relationship between structure and energy of the Cu/MnO interface is discussed.

Nb/Al2O3 interfaces were produced by (i) diffusion bonding of single crystalline Nb and Al2O3 at 1973 K, (ii) internal oxidation of a Nb-3at.% Al alloy at 1773 K, and (iii) molecular beam epitaxy (MBE) growth of 500 nm thick Nb overlayers on sapphire substrates at 1123 K. Cross-sectional specimens were prepared and studied by conventional (CTEM) and high resolution transmission electron microscopy (HREM). The orientation relationships between Nb and Al2O3 were identified by diffraction studies. HREM investigations revealed the structures of the different interfaces including the presence of misfit dislocations at or near the interface. The results for the different interfaces are compared.

Image processing techniques applied to HREM images of decagonal quasicrystalline phases are carried out. A comparison between these processed images, simulated images based on the multislice method and density wave techniques and also experimental STM images of the decagonal phase [9] suggest some insights on their structure.

Several examples of defect characterization which are of topical inter-est to Si device technology are presented. The results obtained by high-reso-lution electron microscopy (HREM) are discussed in context with the actual defect problem. - Reinvestigation of platelike defects in Si produced by reactive ion etching in hydrogen containing plasmas (CHF3) shows that some of the {111} platelets are of extrinsic nature. The defects contain probably both constituents from the plasma and Si-interstitials created by the impin-ging ions. - A high dose As-implantation forms an amorphous Si surface layer which has a sharply curved amorphous/crystalline (a/c)-interface below the implantation mask edge. Annealing at 900°C leads to formation of vacancy-type defects under the mask edge. This is due to the different regrowth rates on the various lattice planes of the curved a/c-interface. - Metal-silicide pre-cipitation at the SiO2/Si interface reduces the breakdown field strength of thin oxides. The main failure mechanism observed in model experiments is the thinning of the oxide layer thickness. - Additional x-ray peaks which are frequently observed in low-pressure chemical vapour deposited (625 7deg;C) po-lycrystalline Si layers arise from a diamond hexagonal Si phase. Small inclu-sions and bands of this phase were for the first time directly observed by HREM.

Motion of ordered twin/matrix interfaces in films of silicon on sapphire occurs during high temperature annealing. This process is shown to be thermally activated and is analogous to grain boundary motion. Motion of amorphous/crystalline interfaces occurs during recrystallization of CoSi2 and NiSi2 from the amorphous phase. In-situ transmission electron microscopy has revealed details of the growth kinetics and interfacial roughness.

We report observations of interfacial structure and consequences for layer synthesis modes in mesotaxial Si/CoSi2/Si structures, as deduced from high resolution transmission electron microscopy (HRTEM). It is argued that relative crystal misalignments arising from the lattice parameter mismatch between the Si and CoSi2 may render classic rigid shift measurements of interfacial structure inaccurate. An alternative method for determining interfacial structure at threedimensional precipitates by analyzing crystal stacking sequences is demonstrated.

The atomic structure of A- and B-type CoSi2/Si (111) interfaces has been investigated by observations of samples in cross-section using a 400 kV high-resolution electron microscope. The samples were prepared by UHV e–beam evaporation of Co layers followed by annealing at temperatures between 300°C and 500°C. Based upon image simulations for various interface bonding models we have found evidence for 7–fold Co coordination at the A–type CoSi2/Si interfaces and for 7– and 8–fold coordination at the B-type interfaces.

The interfacial reaction of titanium with single crystal silicon has been characterized using high-resolution electron microscopy(HREM) combined with nano-scale microanalysis. HREM shows that there is an amorphous interdiffused alloy formation at titanium-silicon interfaces. The reacted layer is about 1.7nm thick for single crystal silicon, but is 2.5nm thick for sputter-amorphized silicon. Annealing increases the thickness of the amorphous alloy. We have used high-spatial-resolution microanalysis to obtain energy dispersive spectrometry (EDS) using a 2nm probe size. The results clearly show that reliable composition analysis can be obtained at this level since some of the layers are only about 2nm thick. It was found that the amorphous alloy composition was Ti55Si45 for the sputter-amorphized silicon. Futhermore we ascertained no induced reaction by 2nm probe electron beam irradiation.

High resolution transmission electron microscopy has been applied to study the formation of amorphous interlayers by solid-state diffusion in ultrahigh vacuum deposited Ti thin films on (001), (111) and (011)Si

The interface structures of as deposited and annealed samples were examined. The disordered regions at the a-interlayer/c-Si interfaces were found to be most and least extensive in (011) and (111) samples, respectively. Growth behaviors of a-interlayers are described. The amorphization appeared to be initiated at the grain boundaries of Ti thin films. Ti5 Si3 was identified to be the phase formed at the initial stage of the interfacial reactions by HREM in conjunction with the optical diffraction.

Defects found in and around intersections of deformation twins have been examined by high resolution electron microscopy. Experimental difficulties, especially local buckling of the crystal and radiation damage under the electron beam, lead to a need to interpret images of lattices tilted by almost a degree from the zone axis. This paper demonstrates the ability of image simulation programs to model successfully the scattering from a tilted crystal. It is shown how the generation of moir6 patterns between a lattice image and a reference array of dots offers a convenient method for extracting information about distortions of the lattice around defects.

High resolution electron microscopy (HREM) has been used to study the atomic arrangement of defects formed during high-dose oxygen implantation of silicon-on-insulator material. The effect of implantation parameters of wafer temperature, dose, and current density were investigated. Wafer temperature had the largest effect on the type and character of the defects. Above the buried oxide layer in the top silicon layer, HREM revealed that microtwins and stacking faults were created during implantation from 350–450°C. From 450–550°C, stacking faults were longer and microtwinning was reduced. From 550–700°C, a new type of defect was observed which had lengths of 40 to 140 nm and consisted of several discontinuous stacking faults which were randomly spaced and separated by two to eight atomic layers. We have referred to them as “multiply faulted defects” (MFDs). Beneath the buried oxide layer in the substrate region, the defects observed included stacking faults and ( 113 ) defects. The results indicated that some parts of the ( 1131 defects can assume a cubic diamond structure created through a twin operation across (115) planes. Details of the structure and formation mechanisms of MFDs and other defects will be discussed.

The morphology of SiO2/Si interfaces in a semiconductor LOCOS active area grown by several oxidation conditions has been studied, to compare the roughness of the interfaces observed by STM and HRTEM in particular. Samples consisted of typical MOS structures with a polysilicon gate/SiO2/Si(100). Hydrogen terminated Si surfaces were prepared by means of HF dipping for STM observations. The interface roughness of a “dry” oxide observed by HRTEM was slightly larger than that of a “wet” oxide. Good agreement could be found between STM and HRTEM for the wet oxide interfaces. As for the dry oxide interface, it was more difficult to obtain a reproducible STM image than for the wet oxide interface, but the reverse was true for HRTEM. During the HRTEM, high energy electrons damage the sample and reduce the oxide thickness, especially in the wet oxide samples.

Nitrogen and also sequential nitrogen/oxygen implantations at an energy of 330 keV result in the formation of α-Si3N4 precipitates below the buried layer. A particular orientation relation between the α-Si3N4 and the Si lattice was established: the basal (00.1) α-Si3N4 plane is parallel to one of the Si {111} planes. Planar defects with (00.1) habit planes have been identified by HREM as stacking faults with a displacement vector of 1/3<10.0>.

Arsenic doped polysilicon was deposited on a <001> oriented Si wafer. Cross-section TEM specimen preparation was performed, giving the vertical structure of the stack. The observation was done with a <110> zone axis to ensure that the interface is strictly oriented under the electron beam. High resolution imaging on the very interfacial region proved the existence of an ultrathin regular amorphous layer running along the interface (thickness 1 rim). Complementary analytical investigations showed that the layer was really amorphous (EELS) and that the dopant was overconcentrated in this layer (EDXS linescan and SIMS profile). Therefore, a slight amorphization of the interface added to an abnormal migration of the dopant gives a well detectable layer separating both crystalline phases.

High quality Si/Ge strained-layer superlattices composed of a sequence of alternating 3 monolayers pure Si and 9 monolayers pure Ge have been grown by molecular beam epitaxy at 310°C on Ge(001) substrates. In order to investigate the transition from coherent to incoherent growth in these tensily strained structures a set of samples with varying number of superlattice periods has been studied by transmission electron microscopy. It is found that superlattices as thick as 33 nm at least show perfect and defect-free layer growth whereas for thicker superlattices strain accommodation occurs. For this strained heteroepitaxial system we observed, to our knowledge, for the first time the formation of microtwins as the only relaxation mechanism. High-resolution lattice imaging reveals that the twin lamellae result from successive glide of 90° (a/6)<112> Shockley partial dislocations on adjacent {111} planes from the surface towards the bulk. The activation barrier which has to be overcome in the case of 90° partial dislocations is compared with the energies required for the nucleation of 60° perfect and 30° partial misfit dislocation half-loops.