Etching microscopic samples

Etching was performed by dipping the samples into the 4% aqueous solution of hydrofluoric acid at room temperature. After etching the samples were washed in distilled water and then probed by scanning electron microscope Hitachi S-806 and atomic force microscope NTEGRA Prima operating in a contact mode. 

Optical microscopic examinations of the reactant at room temperature can provide information on the shapes and sizes of the crystallites and structural information from features of observed symmetry. The degree of perfection of the crystallites can be assessed and damage, major defects and inclusions may be identified. Surface defects, such as the points of emergence of dislocations, may be revealed by etching the sample surface with a suitable solvent. Cleaving of a crystal gives two closely related faces and one section may be etched to reveal the location of defects while the other section is partially decomposed and then re-examined [30,31 ] to enable the distributions of the different surface features (usually dislocations and nuclei) to be compared. Such techniques have been used to investigate the role of defects in the initiation of decomposition [32,33]. 

Etched samples were removed, the etching solution was diluted with deionized water to a very low concentration, and electron microscope grids were prepared by platinum shadowing. Similarly, a less dilute solution (from the etching of sample E-5) was placed on a clean microscope slide, allowed to dry, and examined under the SEM. 

Figure 6. Plan of the target preparation facilities consisting of UHV preparation chamber (a), (reactive) ion etching chamber (b), ion etching gun (c), laser (d), photon detector (e), transfer arms (f), Auger system for surface analysis (g), sample manipulator and annealing facility (h), load lock and optical microscope for viewing sample (i), evaporator (j), transmission diffractometer (k), and vacuum tank for main spectrometer (1).

Etch times were investigated for aluminum and SU8 sacrificial cores patterned on silicon. Samples were periodically removed from the acid etch solution, and the amount of sacrificial core that was removed was measured using an optical microscope. We found that the etch length as a function of time follows the equation... 

Fig. 6 (a) Schematic illustration of a flow cytometer used in a suspension array. The sample microspheres are hydrodynamically focused in a fluidic system and read-out by two laser beams. Laser 1 excites the encoding dyes and the fluorescence is detected at two wavelengths. Laser 2 is used to quantify the analyte, (b) Scheme of randomly ordered bead array concept. Beads are pooled and adsorbed into the etched wells of an optical fiber, (c) Scheme of randomly-ordered sedimentation array. A set of encoded microspheres is added to the analyte solution. Subsequent to binding of the analyte, microparticles sediment and assemble at the transparent bottom of a sample tube generating a randomly ordered array. This array is evaluated by microscope optics and a CCD-camera. Reproduced with permission from Refs. [85] and [101]. Copyright 1999, 2008 American Chemical Society... 

Figure 2.41. Microscopic examination of Mg-Cu alloys. The micrographs of the same two alloys considered in Fig. 2.40 are shown. Small pieces of the alloys were polished by using finer and finer abrasive powders (A1203, diamond) in order to obtain a shiny surface. This appears as a continuous white surface under a metallographic reflection microscope. When the sample, however, is gently etched by using a convenient reactant (in this specific case a dilute water-alcohohc solution of HN03) phases of different chemical composition (here Mg and the compound CuMg2) are differentiated. The more reactive phase (in this case Mg) is more deeply etched, losing its brilliance, and it appears dark under the microscope.

For freeze-fracture, a drop of the formulation containing 30% glycerol was deposited on a thin copper planchet and rapidly frozen in liquid propane. Fracturing and shadowing using Pt-C were performed in a Balzers BAF 310 freeze-etch unit. Other samples were simply deposited on a freshly cleaved mica plate and air-dried before shadowing as above. Replicas were examined with a Philips 410 electron microscope. 

After quick freezing in liquid nitrogen and fracture, another etching method was used at — 90 °C for less than 1 min in a 1.33 x 10-4 Pa chamber. The etched sample was cooled to — 130°C and coated with platinum and carbon in the same vacuum chamber and transferred to the scanning electron microscope at — 130 °C. The observed structure was closer to reality than that obtained by the method previously described. This is called the cryo-SEM technique [32]. CryoSEM images are shown in Fig. 4 which presents the structural change by stretching [16]. 

To etch away silica, carbonization product samples were treated with a mixture of concentrated sulfuric and hydrofluoric acids (5 drops of H2S04 and 1 mL of HF), boiled dry and washed with water. From the precipitate obtained were prepared dispersions in acetone, which were used to determine the size and shape of particles on a JEM100CX-II transmission electron microscope by a commonly used procedure[10]. 

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