Carbon fiber composite targets for nuclear fusion technology: a focused ion beam/scanning electron microscope investigation

Carbon fiber composite (CFC) targets are investigated by a focused ion beam/scanning electron microscope (FIB/SEM) in a joint project aiming at the development of robust divertors in the International Thermonuclear Experimental Reactor (ITER). These mockups are exposed to a plasma that simulates the off-normal thermal loads foreseen for ITER and display a rich, puzzling impact scenario. Morphological elements are identified at the exposed surface and beneath it, and are examined in order to point out the relevant processes involved. Each technique adopted is discussed and evaluated.     

Focused ion beam scanning electron microscopy in biology

Since the end of the last millennium, the focused ion beam scanning electron microscopy (FIB‐SEM) has progressively found use in biological research. This instrument is a scanning electron microscope (SEM) with an attached gallium ion column and the 2 beams, electrons and ions (FIB) are focused on one coincident point. The main application is the acquisition of three‐dimensional data, FIB‐SEM tomography. With the ion beam, some nanometres of the surface are removed and the remaining block‐face is imaged with the electron beam in a repetitive manner. The instrument can also be used to cut open biological structures to get access to internal structures or to prepare thin lamella for imaging by (cryo‐) transmission electron microscopy. Here, we will present an overview of the development of FIB‐SEM and discuss a few points about sample preparation and imaging.     

Focused ion beam/scanning electron microscopy studies of Porcellio scaber (Isopoda, Crustacea) digestive gland epithelium cells

The focused ion beam (FIB) was used to prepare cross sections of precisely selected regions of the digestive gland epithelium of a terrestrial isopod P. scaber (Isopoda, Crustacea) for scanning electron microscopy (SEM). The FIB/SEM system allows ad libitum selection of a region for gross morphologic to ultrastructural investigation, as the repetition of FIB/SEM operations is unrestricted. The milling parameters used in our work proved to be satisfactory to produce serial two-dimensional (2-D) cuts and/or three-dimensional (3-D) shapes on a submicrometer scale. A final, cleaning mill at lower ion currents was employed to minimize the milling artifacts. After cleaning, the milled surface was free of filament- and ridge-like milling artifacts. No other effects of the cleaning mill were observed.     

Observation of human dentine by focused ion beam and energy-filtering transmission electron microscopy

Molar dentine was sliced into 100 nm ultrathin sections, by means of a focused ion beam, for observation by energy-filtering transmission electron microscopy (EFTEM). Within the matrix, crystals approximately 10 nm wide and 50–100 nm long were clearly observed. When carbon and calcium were mapped in electron spectroscopic images by EFTEM, carbon failed to localize in crystals. However, it was found in other regions, especially those adjacent to crystals. Because carbon localizations were thought to reflect the presence of organic components, carbon concentration in regions near crystals suggested the interaction of crystals and organics, leading to organic control of apatite formation and growth. Ca was present in almost all regions. The majority of Ca localizing in regions other than crystals may be bound to organic substances present in dentine matrix. These substances are thought to both accumulate Ca and act as reservoirs for crystallization of apatite in dentine.     

Particle‐induced x‐ray analysis using focused ion beams

In addition to the production of secondary electrons and secondary ions, characteristic x‐ray emission may also result from ion/solid interactions and is the basis for the well‐known analysis technique referred to as particle‐induced x‐ray emission. Characteristic x‐rays may be emitted by either bombardment by MeV protons or heavy ions of a few keV. The advantage to heavy ions is that the x‐ray yield is confined to the region near the surface defined by the collision cascade. An advantage of heavy ion‐induced x‐ray emission over electron‐induced x‐ray emission is that the Bremsstrahlung is potentially orders of magnitude lower. Thus, ion‐induced x‐ray spectra may provide for superior peak‐to‐noise ratios, and there‐fore, offers trace element sensitivity compared with elec‐tron‐induced x‐ray emission. In addition, the near surface ion/solid interactions also allow for the possibility of surface analysis or depth profiling. A Dual Beam instrument was used to collect focused ion beam‐induced x‐ray (FIBIX) spectra. The acquisition of characteristic x‐rays from targets via FIBIX is demonstrated and compared with scanning electron microscopy‐induced x‐ray energy dispersive spectroscopy spectra and is consistent with the theory described above.     

Nano-slit probes for near-field optical microscopy fabricated by focused ion beams

The near-field probes described in this paper are based on metallized non-contact atomic force microscope cantilevers made of silicon. For application in high-resolution near-field optical/infrared microscopy, we use aperture probes with the aperture being fabricated by focused ion beams. This technique allows us to create apertures of sub-wavelength dimensions with different geometries. In this paper we present the use of slit-shaped apertures which show a polarization-dependent transmission efficiency and a lateral resolution of < 100 nm at a wavelength of 1064 nm. As a test sample to characterize the near-field probes we investigated gold/palladium structures, deposited on an ultrathin chromium sublayer on a silicon wafer, in constant-height mode.     

Post‐thinning using Ar ion‐milling system for transmission electron microscopy specimens prepared by focused ion beam system

We investigate Ar ion‐milling rates and Ga‐ion induced damage on sample surfaces of Si and GaAs single crystals prepared by focused ion beam (FIB) method for transmission electron microscopy observation. The convergent beam electron diffraction technique with Bloch simulation is used to measure the thickness of the Ar‐ion milled samples to calculate the milling rates of Si and GaAs single crystals. The measurement shows that an amorphous layer is formed on the sample surface and can be removed by further Ar‐ion milling. In addition, the local symmetry breaking induced by FIB is investigated using quantitative symmetry measurement. The FIBed‐GaAs sample shows local symmetry breaking after FIB milling, although the FIBed‐Si sample has no considerable symmetry breaking.     

Objective comparison of scanning ion and scanning electron microscope images

Common and different aspects of scanning electron microscope (SEM) and scanning ion microscope (SIM) images are discussed from a viewpoint of interaction between ion or electron beams and specimens. The SIM images [mostly using 30 keV Ga focused ion beam (FIB)] are sensitive to the sample surface as well as to low-voltage SEM images. Reasons for the SIM images as follows: (1) no backscattered-electron excitation; (2) low yields of backscattered ions; and (3) short ion ranges of 20–40nm, being of the same order of escape depth of secondary electrons (SE) [=(3–5) times the SE mean free path]. Beam charging, channeling, contamination, and surface sputtering are also commented upon.     

Subsurface nanoindentation deformation of Cu-Al multilayers mapped in 3D by focused ion beam microscopy

A new technique for the three-dimensional analysis of subsurface damage of nanocomposites is presented. Cu–Al multilayers, grown epitaxially on (0001)Al₂O₃ single crystals by ultra high vacuum molecular beam epitaxy, have been deformed by nanoindentation. Systematic slicing and imaging of the deformed region by focused ion beam microscopy enables a 3D data set of the damaged region to be collected. From this 3D data set, profiles of the deformed sub-surface interfaces can be extracted. This enables the deformation of the individual layers, substrate and overall film thickness to be determined around the damage site. These 3D deformation maps have exciting implications for the analysis of mechanical deformation of nanocomposites on a sub-micrometre scale.     

Preparation of transmission electron microscopy cross-section specimens of crack tips using focused ion beam milling

The preparation of transmission electron microscope (TEM) thin foil specimens from metal alloys containing cracks is usually thwarted by the difficulty in preventing preferential erosion of material along the flanks and at the tips of cracks. Recent developments in focused ion beam (FIB) micromachining methods have the potential to overcome this inherent problem. In this article we describe the development of new procedures, one using FIB alone and the other using a combination of FIB with more conventional ion milling to generate TEM specimens that largely retain the microstructural information at stress corrosion cracks in austentic alloys. Examples of corrosion product phase identification and interfacial segregation are included to verify that detailed information is not destroyed by ion bombardment during specimen preparation.     

Focused ion beam manipulation and ultramicroscopy of unprepared cells

The focused ion beam (FIB) technique of nanomachining combined with simultaneous scanning electron microscopy (SEM) was used for submicron manipulation and imaging of unprepared (fresh) cells to demonstrate the potentiality of the FIB/SEM technique for ultramicroscopic studies. Sectioning at the nanoscale level was successfully performed by means of ion beam-driven milling operations that reveal the ultrastructure of fresh yeast cells. The FIB/SEM has many advantages over other ultramicroscopy techniques already applied for unprepared/fresh biological samples.     

Preparation of site-specific cross-sections of heterogeneous catalysts prepared by focused ion beam milling

Focused ion beam (FIB) milling offers a novel approach to preparation of site‐specific cross‐sections of heterogeneous catalysts for examination in the transmission electron microscope (TEM). Electron‐transparent sections can be obtained without the need to embed or grind the original sample. Because the specimen can be imaged in the FIB with submicrometre resolution before, during and after milling it is possible to select precisely the region from which the section is removed and to control the thickness of the section to within tens of nanometres. The ability to produce sections in this way opens the possibility of studying a range of catalyst systems that have previously been impossible to examine with the TEM.     

Transmission electron microscopy of fluorapatite–gelatine composite particles prepared using focused ion beam milling

In this paper, synthetic fluorapatite–gelatine composite particles are prepared for transmission electron microscopy (TEM) studies using two methods based on focused ion beam (FIB) milling. TEM studies on the FIB‐prepared specimens are compared with TEM observations on samples prepared using an ultramicrotome. The results show that ultramicrotome slicing causes significant cracking of the apatite, whereas the ion beam can be used to make high‐quality, crack‐free specimens with no apparent ion beam‐induced damage. The TEM observations on the FIB‐prepared samples confirm that the fluorapatite composite particles are composed of elongated, preferentially orientated grains and reveal that the grain boundaries contain many small interstices filled with an amorphous phase.     

Quantitative off-axis electron holography of GaAs p-n junctions prepared by focused ion beam milling

Focused Ion beam (FIB) prepared GaAs p-n junctions have been examined using off-axis electron holography. Initial analysis of the holograms reveals an experimentally determined built-in potential in the junctions that is significantly smaller than predicted from theory. In this paper we show that through combinations of in situ annealing and in situ biasing of the specimens, by varying the intensity of the incident electron beam, and by modifying the FIB operating parameters, we can develop an improved understanding of phenomena such as the electrically 'inactive' thickness and subsequently recover the predicted value of the built-in potential of the junctions.
PACS numbers: 85.30.De     

Focused ion beam characterization of plasma-assisted deposition on polymer films at the nanoscale

In this paper, a novel technique is presented for the characterization at the nanoscale of plasma-assisted deposit on polyethylene-terephthalate (PET) polymer films. In previous studies, some microcharacterization and morphology analyses of plasma-assisted deposition were performed by atomic force microscopy (AFM). In the work presented here, we analysed the thickness and homogeneity of plasma-assisted deposits by focused ion beam (FIB). This technique with 5-7 nm resolution requires no sample preparation and relies on a sequence of operations on a relatively fast time scale, so that it is easy to make thorough investigations of the sample. We performed electron and ion imaging of the surface of the material, and a subsequent ionic cutting allowed the study of the morphology of the same sample. We developed a novel approach to the edge detection techniques (EDT) in images for a fast evaluation and monitoring of the deposited layer.     

Localized grounding, excavation, and dissection using in-situ probe techniques for focused ion beam and scanning electron microscopy: experiments with rock varnish

While investigating rock varnish, we explored novel uses for an in‐situ micromanipulator, including charge collection, sample manipulation, as well as digging and dissection at the micron level. Dual‐beam focused ion beam microscopes (DB‐FIB or FIBSEM) equipped with micromanipulators have proven to be valuable tools for material science, semiconductor research, and product failure analysis. Researchers in many other disciplines utilize the DB‐FIB and micromanipulator for site‐specific transmission electron microscope (TEM) foil preparation. We have demonstrated additional applications for in‐situ micromanipulators. SCANNING 34: 279–283, 2012. © 2012 Wiley Periodicals, Inc.     

高反射率13nmMo/Si多层膜

采用离子束溅射在不同的工艺参数下制备一系列单层 Mo膜、Si膜及多层膜 ,并用原子力显微镜分析单层膜表面粗糙度及两种材料间的界面扩散。当束流电压超过一定数值时 ,可避免单层膜的柱状生长 ;在 Mo- on- Si和 Si- on- Mo界面中 ,Mo- on- Si界面扩散对反射率的影响更大。采用 X射线衍射仪分析多层膜中 Mo、Si材料的晶体结构 ,均为多晶结构 ,其中 Mo为 ( 1 1 0 )晶向 ,Si为 ( 4 0 0 )晶向。根据上述分析优化工艺参数 ,获得的 1 3nm Mo/Si多层膜反射率达到 60 %。     

An experimental model of beam broadening in the variable pressure scanning electron microscope

In the variable pressure scanning electron microscope (VP-SEM) the incident electrons pass through a gaseous environment and the beam is scattered by these interactions. We show here that the experimental intensity profile of the scattered beam can be described as Gaussian in form to a high level of accuracy. This provides a rapid means of accounting for the effects of beam scatter in imaging and microanalysis because the standard deviation of the Gaussian is a simple function of parameters such as working distance, beam energy, gas type and pressure.     

The assessment of microscopic charging effects induced by focused electron and ion beam irradiation of dielectrics

Energetic beams of electrons and ions are widely used to probe the microscopic properties of materials. Irradiation with charged beams in scanning electron microscopes (SEM) and focused ion beam (FIB) systems may result in the trapping of charge at irradiation induced or pre-existing defects within the implanted microvolume of the dielectric material. The significant perturbing influence on dielectric materials of both electron and (Ga(+)) ion beam irradiation is assessed using scanning probe microscopy (SPM) techniques. Kelvin Probe Microscopy (KPM) is an advanced SPM technique in which long-range Coulomb forces between a conductive atomic force probe and the silicon dioxide specimen enable the potential at the specimen surface to be characterized with high spatial resolution. KPM reveals characteristic significant localized potentials in both electron and ion implanted dielectrics. The potentials are observed despite charge mitigation strategies including prior coating of the dielectric specimen with a layer of thin grounded conductive material. Both electron- and ion-induced charging effects are influenced by a delicate balance of a number of different dynamic processes including charge-trapping and secondary electron emission. In the case of ion beam induced charging, the additional influence of ion implantation and nonstoichiometric sputtering from compounds is also important. The presence of a localized potential will result in the electromigration of mobile charged defect species within the irradiated volume of the dielectric specimen. This electromigration may result in local modification of the chemical composition of the irradiated dielectric. The implications of charging induced effects must be considered during the microanalysis and processing of dielectric materials using electron and ion beam techniques.