Film preparation, electron microscopy

Thin films of metals, alloys and compounds of a few micrometres diickness, which play an important part in microelectronics, can be prepared by die condensation of atomic species on an inert substrate from a gaseous phase. The source of die atoms is, in die simplest circumstances, a sample of die collision-free evaporated beam originating from an elemental substance, or a number of elementary substances, which is formed in vacuum. The condensing surface is selected and held at a pre-determined temperature, so as to affect die crystallographic form of die condensate. If diis surface is at room teiiiperamre, a polycrystalline film is usually formed. As die temperature of die surface is increased die deposit crystal size increases, and can be made practically monocrystalline at elevated temperatures. The degree of crystallinity which has been achieved can be determined by electron diffraction, while odier properties such as surface morphology and dislocation sttiicmre can be established by electron microscopy. 

Glad [37] studied the micro deformations of thin films prepared from DGE-BA/MDA by electron microscopy. His results are also shown in Fig. 7.5. The deformation of the sample with high strand density was small and consequently its image in the EM rather blurred. Therefore, the result on Mc = 0.5 kg/mol should perhaps have been omitted. 

The decomposition of formic acid over evaporated Pd-Au alloy films has been studied by Clarke and Rafter (69) the same reaction on Pd-Au alloy wires was studied by Eley and Luetic (128). The alloy films were prepared in a conventional high vacuum system by simultaneous evaporation of the component metals from tungsten hairpins. The alloy films were characterized by X-ray diffraction and electron microscopy. The X-ray diffractometer peaks were analyzed by a method first used by Moss and Thomas (SO). It was found that alloys deposited at a substrate temperature of 450°C followed by annealing for one hour at the same temperature were substantially homogeneous. Electron microscopy revealed that all compositions were subject to preferred orientation (Section III). 

Titania films prepared by the methods described above are, however, just partially crystalline. Although WAXS patterns indicate formation of anatase crystals of ca. 10-12nm in size (Fig. 9.3a), the electron microscopy study demonstrates that the elongated crystals are actually embedded into an amorphous mesoporous matrix (Fig. 9.3c). The degree of crystallinity for such films usually does not exceed 60% attempts to increase it by calcination at higher temperatures cause uncontrolled crystal growth, which leads to collapse of mesoporos-ity and a drastic decrease in the surface area (Fig. 9.3d). 

Figure 9.5. Mesoporous Ti02 films templated by the KLE block copolymer, (a) Scanning electron microscopy (T = 600 °C, i.e., above the crystallization temperature) and (b) Krypton physisorption of films heat-treated at 570 °C (filled circles) and 650 °C (triangles). It is seen that the porosity of films, prepared by the advanced block copolymer template, is still intact even after treatment at temperatures that convert the amorphous Ti02 matrix into the crystalline (anatase) one. The films were prepared based on the recipe in Ref. 80.

Core-shell colloidal crystal films were prepared in three steps as outlined in Table 4.2. First, spherical submicron polystyrene particles were prepared by known methods38 39. The size of isolated polystyrene beads was 326 5 nm as determined by analysis of scanning electron microscopy (SEM) images using standard techniques. 

Electron microscopy easily yields structural images of cast bilayer films. Figure 6 shows a scanning electron microscope (SEM) image of the cross section of the bilayer film of CgAzoCioN+Br prepared by the simple casting of water solution. From the presence of well developed layers parallel to die film plane, it can be assumed that the cast film was composed from multiple highly oriented bilayers. 

Atomic force microscopy (AFM) is a commonly employed imaging technique for the characterization of the topography of material surfaces. In contrast to other microscopy techniques (e.g., scanning electron microscopy), AFM provides additional quantitative surface depth information and therefore yields a 3D profile of the material surface. AFM is routinely applied for the nanoscale surface characterization of materials and has been previously applied to determine surface heterogeneity of alkylsilane thin films prepared on planar surfaces [74,75,138]. 

Roskov KE, Epps TH, Berry BC, Hudson SD, Tureau MS, Fasolka MJ (2008) Preparation of combinatorial arrays of polymer thin films for transmission electron microscopy analysis. J Comb Chem 10 966-973... 

In transmission electron microscopy (TEM), a beam of highly focused and highly energetic electrons is directed toward a thin sample (< 200 nm) which might be prepared from solution as thin film (often cast on water) or by cryocutting of a solid sample. The incident electrons interact with the atoms in the sample, producing characteristic radiation. Information is obtained from both deflected and nondeflected transmitted electrons, backscattered and secondary electrons, and emitted photons. 

Mass spectrometers Molecular beam apparatus Ion sources Particle accelerators Electron microscopes Electron diffraction apparatus Vacuum spectographs Low-temperature research Production of thin films Surface physics Plasma research Nuclear fusion apparatus Space simulation Material research Preparations for electron microscopy... 

Cryoelectron microscopy makes it possible to have a direct view into the frozen sample without additional preparation [100]. With the aid of a cryogen (e.g., liquid nitrogen-cooled liquid ethane), the sample is plunge frozen as a very thin aqueous film prepared on a microscopic grid. Subsequently, the vitrified specimen is directly transferred into a precooled electron microscope. Because the specimens are usually ) 2005 by CRC Press LLC... 

Non-porous amorphous alumina films (several hundred Angstroms thick) can be prepared by the anodic oxidation of clean, high-purity Al. The oxide film is separated by dissolving any unoxidized metal in a mercury chloride solution. The oxide films are then washed in distilled water and collected on suitable electron microscopy grids. They are dried and heated to 800 "C to obtain amorphous AI2O3. High-purity wires of the desired metals can then be vacuum evaporated on to the films in an evaporator. These films can also be prepared using Al-nitrate,... 

Tubules prepared from diacetylenic phospholipids (21) Copper and nickel films Electron microscopy and X-ray fluorescence measurements indicated 20- to 30-nm metallic coatings on the interiors and exteriors of the tubules 356... 

LB films prepared from hexadecyl-TCNQ TMTTF and (heptadecyl-dimethyltetrathia-fulvalene)2 TCNQ and from their mixtures Electron microscopy and electron diffraction Molecular packing determined conductivities best lateral d.c. conductivity was 0.5 S cm -1 765... 

LB films prepared from mixtures of donors (heptadecyldimethyltetrathiafulvalene, hexadecylbis(ethylenedithio)-tetrathiafulvalene, and hexadecylethylene-dithiopropylenedithiotetra-thiafulvalene) and acceptors (hexadecyl-TCNQ and heptadecyloxycarbonyl-TCNQ) Electron microscopy, electron diffraction, and conductivity measurements Molecular packing and conductivities were examined 766... 

LB films prepared from ironfUI) stearate, transferred to solid substrates, dried, exposed to hydrochloric add in a desiccator, and subsequently exposed to pyrrole vapor Absorption spectroscopy, scanning electron microscopy, and conductivity measurements Lateral conductivity as high as t.25 S cm" was measured 123... 

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