Transmission Electron Microscopy Lamella Research Articles

Structural characterisation of BaTiO3 thin films deposited on SrRuO3/YSZ buffered silicon substrates and silicon microcantilevers

We report on the progress towards an all epitaxial oxide layer technology on silicon substrates for epitaxial piezoelectric microelectromechanical systems. (101)-oriented epitaxial tetragonal BaTiO3 (BTO) thin films were deposited at two different oxygen pressures, 5.10−2 mbar and 5.10−3 mbar, on SrRuO3/Yttria-stabilized zirconia (YSZ) buffered silicon substrates by pulsed laser deposition. The YSZ layer full (001) orientation allowed the further growth of a fully (110)-oriented conductive SrRuO3 electrode as shown by X-ray diffraction. The tetragonal structure of the BTO films, which is a prerequisite for the piezoelectric effect, was identified by Raman spectroscopy. In the BTO film deposited at 5.10−2 mbar strain was mostly localized inside the BTO grains whereas at 5.10−3 mbar, it was localized at the grain boundaries. The BTO/SRO/YSZ layers were finally deposited on Si microcantilevers at an O2 pressure of 5.10−3 mbar. The strain level was low enough to evaluate the BTO Young modulus. Transmission electron microscopy (TEM) was used to investigate the epitaxial quality of the layers and their epitaxial relationship on plain silicon wafers as well as on released microcantilevers, thanks to Focused-Ion-Beam TEM lamella preparation.

Cross-sectional TEM preparation of hybrid inorganic/organic materials systems by ultramicrotomy

Preparation of hybrid inorganic-organic systems (HIOS) for transmission electron microscopy (TEM) in cross sectional view is the key for understanding the interfacial structure. Strikingly different materials properties like hardness, cleavability and heat sensitivity limit the number of applicable preparation strategies. Successful preparation of a HIOS system combining ZnO and para-sexiphenyl (6P) is realized by ultramicrotomy. It is shown that the alignment of the cutting plane with respect to the (0001) cleavage plane of ZnO plays a decisive role for successful preparation of extended TEM lamellae and the preservation of the HIOS structure. In particular, for (0001) oriented ZnO substrates the optimum cut direction is parallel to the HIOS interface. In cross-sectional high-resolution TEM images (100) lattice planes of 6P are observed proving the appropriate preparation strategy.

In situ TEM study of stability of TaRhx diffusion barriers using a novel sample preparation method

The atomic diffusion mechanisms associated with metallurgical failure of TaRhx diffusion barriers for Cu metallizations were studied by in situ transmission electron microscopy (TEM). The issues related to in situ heating of focused ion beam (FIB) prepared cross-sectional TEM samples that contain Cu thin films are discussed. The Cu layer in Si/(13nm)TaRhx/Cu stacks showed grain growth and formation of voids at temperatures exceeding 550°C. For Si/(43nm)TaRhx/Cu stacks, grain growth of Cu was delayed to higher temperatures, i.e., 700°C, and void formation was not observed. Extensive surface diffusion of Cu, however, preceded bulk diffusion. Therefore, a 10nm film of electron beam evaporated C was deposited on both sides of the TEM lamellae to limit surface diffusion. This processing technique allowed for direct observation of atomic diffusion and reaction mechanisms across the TaRhx interface. Failure occurred by nucleation of orthorhombic RhSi particles at the Si/TaRhx interface. Subsequently, the barrier at areas adjacent to RhSi particles was depleted in Rh. This created lower density areas in the barrier, which facilitated diffusion of Cu to the Si substrate to form Cu3Si. The morphology of an in situ annealed lamella was compared with an ex situ bulk annealed sample, which showed similar reaction morphology. The sample preparation method developed in this study successfully prevented surface diffusion/delamination of the Cu layer and can be employed to understand the metallurgical failure of other potential diffusion barriers.

Influence of microstructure on the erosion and erosion–corrosion characteristics of 316 stainless steel

The economic impact of surface damage and component failure arising from solid particle impact in the UK has been estimated in 1997 at around £20 million [1]. The additional complexity associated with erosion in a corrosive environment such as that encountered in the chemical and hydro-carbon extraction industries can significantly accelerate surface wear and material loss. In this study, surface material response of a stainless 316 alloy subject to erosion and erosion–corrosion was investigated by focused ion beam (FIB) and transmission electron microscopy (TEM) techniques. Samples tested in a slurry pot apparatus using 1% uncrushed silica at 7m/s for 60min, both in water and 3.5% NaCl solution. Site specific FIB–TEM lamellas showed that solid particle impact resulted in extensive crater and lip formations and a martensitic phase transformation at the surface. The presence of a corrosive fluid resulted in preferential dissolution of the martensitic phase, reducing the work hardening behaviour and promoting greater elongation to failure and thus higher erosion–corrosion rates. These results are discussed in light of the extensive literature on solid particle impact and corrosion by considering the influence of nano-scale phase changes which can often only be observed using transmission electron microscopy.

Improved Focused Ion Beam Target Preparation of (S)TEM Specimen—A Method for Obtaining Ultrathin Lamellae

Specimen quality is vital to (scanning) transmission electron microscopy (TEM) investigations. In particular, thin specimens are required to obtain excellent high-resolution TEM images. Conventional focused ion beam (FIB) preparation methods cannot be employed to reliably create high quality specimens much thinner than 20 nm. We have developed a method for in situ target preparation of ultrathin TEM lamellae by FIB milling. With this method we are able to routinely obtain large area lamellae with coplanar faces, thinner than 10 nm. The resulting specimens are suitable for low kV TEM as well as scanning TEM. We have demonstrated atomic resolution by Cs-corrected high-resolution TEM at 20 kV on a FIB milled Si specimen only 4 nm thick; its amorphous layer measuring less than 1 nm in total.

Time evolution of morphology in mechanically alloyed Fe–Cu

Being widely accessible as well as already utilised in many applications, Fe-Cu acts as an ideal binary model alloy to elaborate the enforced nonequilibrium enhanced solubility in such a solution system that shows a limited regime of miscibility and characterised by a large positive heat of mixing. In addition to the detailed analysis of ball milled Fe-Cu powders by means of Atom Probe Tomography (APT), site specific structural analysis has been performed in this study using Transmission Electron Microscopy (TEM). In this contribution results on powders with low Cu concentrations (2.5-10 at%) are presented. Combining a ductile element (Cu, fcc) and a brittle one (Fe, bcc), striking differences in morphology were expected and found on all length-scales, depending on the mixing ratio of the two elements. However, not only could the atomic mixing of Fe and Cu be evaluated, but also the distribution of impurities, mostly stemming from the fabrication procedure. The combination of APT and TEM enables a correlation between the structural evolution and the chemical mixing during the milling process. For the first time, a clear distinction can be drawn between the morphological evolution at the surface and in the interior of the powder particles. This became possible owing to the site specific sample preparation of TEM lamellae by Focussed Ion Beam (FIB). Surprisingly, the texture arising from the ball milling process can directly be related to the classical rolling texture of cold rolled Fe. In addition, full homogeneity can be achieved even on the nano-scale for this material as shown by APT, resulting in an extended miscibility region in comparison to the equilibrium phase diagram. Grain sizes were determined by means of XRD and TEM. The strain corrected XRD results are in very good agreement with the values derived by TEM, both confirming a truly nanocrystalline structure.

Localization and preparation of recombination-active extended defects for transmission electron microscopy analysis

Recombination-active extended defects in semiconductors frequently occur at a low density which makes their structural and chemical analysis by transmission electron microscopy (TEM) techniques virtually impossible. Here an approach is described that uses in situ electron beam induced current (EBIC) in a focused ion beam machine to localize such defects for TEM lamella preparation. As an example, a defect complex occurring in block-cast multicrystalline silicon with a density of less than 10(4) cm(-3) has been prepared and analyzed by TEM. The chemical sensitivity of the technique is estimated to be about 10(13) atoms cm(-2) which is comparable to synchrotron-based x-ray techniques. The localization accuracy of the TEM lamella is shown to be better than 50 nm when low-energy EBIC is used.

Correlating Raman peak shifts with phase transformation and defect densities: a comprehensive TEM and Raman study on silicon

AbstractSilicon is the most often used material in micro electromechanical systems (MEMS). Detailed understanding of its mechanical properties as well as the microstructure is crucial for the reliability of MEMS devices. In this paper, we investigate the microstructure changes upon indentation of single crystalline (100) oriented silicon by transmission electron microscopy (TEM) and Raman microscopy. TEM cross sections were prepared by focused ion beam (FIB) at the location of the indent. Raman microscopy and TEM revealed the occurrence of phase transformations and residual stresses upon deformation. Raman microscopy was also used directly on the cross‐sectional TEM lamella and thus microstructural details could be correlated to peak shape and peak position. The results show, however, that due to the implanted Ga+ ions in the lamella the silicon Raman peak is shifted significantly to lower wavenumbers. This hinders a quantitative analysis of residual stresses in the lamella. Furthermore, Raman microscopy also possesses the ability to map deformation structures with a lateral resolution in the submicron range. Copyright © 2009 John Wiley & Sons, Ltd.

Focused ion beam preparation techniques dedicated for the fabrication of TEM lamellae of fibre-reinforced composites

Two Focused Ion Beam based transmission electron microscopy (TEM) thin film preparation techniques are introduced. One is dedicated to the preparation of single fibres, the other to fibre/matrix interfaces of fibre reinforced composites. Due to their thin film quality, reliability and predictable processing times both techniques are suited for routine applications in material science like TEM studies of fibre microtextures and fibre/matrix interfaces. Exemplarily they are applied to Carbon Fibres and Carbon Fibre reinforced Carbon Matrix Composites (C/C). The achieved preparation standard in both cases is substantiated by TEM investigations.

Combining Ar ion milling with FIB lift-out techniques to prepare high quality site-specific TEM samples.

Focused ion beam (FIB) techniques can prepare site-specific transmission electron microscopy (TEM) cross-section samples very quickly but they suffer from beam damage by the high energy Ga+ ion beam. An amorphous layer about 20-30 nm thick on each side of the TEM lamella and the supporting carbon film makes FIB-prepared samples inferior to the traditional Ar+ thinned samples for some investigations such as high resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). We have developed techniques to combine broad argon ion milling with focused ion beam lift-out methods to prepare high-quality site-specific TEM cross-section samples. Site-specific TEM cross-sections were prepared by FIB and lifted out using a Narishige micromanipulator onto a half copper-grid coated with carbon film. Pt deposition by FIB was used to bond the lamellae to the Cu grid, then the coating carbon film was removed and the sample on the bare Cu grid was polished by the usual broad beam Ar+ milling. By doing so, the thickness of the surface amorphous layers is reduced substantially and the sample quality for TEM observation is as good as the traditional Ar+ milled samples.

Charakterisierung tribologischer Kontakte mit FIB und TEM / A Characterization of Tribological Contacts with FIB and TEM

The article presents examples of examinations on tribologically loaded surfaces and superficial zones by means of the Focused Ion Beam (FIB) method and transmission electron microscopy (TEM). The FIB is employed both as a scanning ion microscope (SIM) to identify tribologically loaded contact surfaces and a processing instrument to purposively produce micro cross-sections and TEM lamellae. The systems under examination are: a ceramic-based composite material for use at high temperatures, the brake lining-against-brake disk system at abt. 200 °C and room temperature, and a diamond layer on SSiC when under a load by rolling. The article shows that oxidation processes, in most cases, play an important role in forming the so-called third body and that the resultant surface layers are nanocrystalline. A friction induced material modification on the surface cannot be proved to exist merely in a single case, i.e. for the diamond layer.

In-situ lift-out von TEM - Proben durch Mikromanipulation in einem Rasterelektronenmikroskop / In-Situ Lift-Out of TEM - Samples by Micro Manipulation in a Scanning Electron Microscope

A new method for in-situ lift-out of samples for transmission electron microscopy (TEM) using a compact and precise micro manipulator inside a scanning electron microscope is presented. A fine needle is positioned with high precision at the TEM lamella and fixed to it by electron beam induced deposition of material at the contact point. The needle itself is connected to a TEM grid, which can afterwards be removed securely from the vacuum chamber. After description of the set up and discussion of opportunities and limitations of this method we report on first results.

Zielpräparation von Proben für 3D-TEM mittels Mikromanipulator / Target Preparation of Samples for 3D-TEM Using Micromanipulators

Transmission electron microscopy (TEM) is increasingly used for characterizing structures that are shrunk continuously, especially microelectronic devices. Conventional focused ion beam technique (FIB technique) is used routinely in the semiconductor industry for time-efficient and reliable target preparation of TEM lamellas. The combination of FIB and lift-out technology using needle manipulators represents a new technical solution for sample preparation for 3-dimensional (3D-) TEM. The process steps for this are described in this article, requirements to optimal sample carriers are discussed and the suitability of the procedure is demonstrated by means of TEM images.

Applied surface analysis in magnetic storage technology

This paper gives a synopsis of today’s challenges and requirements for a surface analysis and materials science laboratory with a special focus on magnetic recording technology. The critical magnetic recording components, i.e. the protective carbon overcoat (COC), the disk layer structure, the read/write head including the giant-magnetoresistive (GMR) sensor, are described and options for their characterization with specific surface and structure analysis techniques are given. For COC investigations, applications of Raman spectroscopy to the structural analysis and determination of thickness, hydrogen and nitrogen content are discussed. Hardness measurements by atomic force microscopy (AFM) scratching techniques are presented. Surface adsorption phenomena on disk substrates or finished disks are characterized by contact angle analysis or so-called piezo-electric mass adsorption systems (PEMAS), also known as quartz crystal microbalance (QCM). A quickly growing field of applications is listed for various X-ray analysis techniques, such as disk magnetic layer texture analysis for X-ray diffraction, compositional characterization via X-ray fluorescence, compositional analysis with high lateral resolution via electron microprobe analysis. X-ray reflectometry (XRR) has become a standard method for the absolute measurement of individual layer thicknesses contained in multi-layer stacks and thus, is the successor of ellipsometry for this application. Due to the ongoing reduction of critical feature sizes, the analytical challenges in terms of lateral resolution, sensitivity limits and dedicated nano-preparation have been consistently growing and can only be met by state-of-the-art Auger electron spectrometers (AES), transmission electron microscopy (TEM) analysis, time-of-flight–secondary ion mass spectroscopy (ToF–SIMS) characterization, focused ion beam (FIB) sectioning and TEM lamella preparation via FIB. The depth profiling of GMR sensor full stacks was significantly improved by the ToF–SIMS Cs method.