Signal generation mechanisms in scanning-electron acoustic microscopy of ionic crystals

MgO crystals have been studied by scanning‐electron acoustic microscopy under different experimental conditions. Contrast mechanisms in imaging are discussed and compared. The experimental results obtained by earthing or nonearthing the specimen‐transducer interface suggest the existence of a signal generation mechanism that is related to the ionic nature of these kind of crystals. Electron‐acoustic microscopy appears then to be a useful tool for the characterization of ionic materials

Evidence for surface uplift of the Atlas Mountains and the surrounding peripheral plateaux: Combining apatite fission-track results and geomorphic indicators in the Western Moroccan Meseta (coastal Variscan Paleozoic basement)

This work represents an initial attempt to link the evolution of the topography in relation to the general tectonic framework of western Morocco. For this purpose, in a section of the Western Moroccan Meseta different tools are combined in order to attain the general objective. Apatite fission-track (AFT) data of granitic rocks of the Rabat–Khenifra area give ages around 200 Ma with track length distributions which are compatible with the thermal models already established for the area. An inverse correlation between AFT ages and elevation is observed which is compatible with previous models indicating northward tilting of the whole Western Moroccan Meseta which is younger than 20–25 Ma. In order to test this possibility a detailed analysis of the topography at different scales in the Western Moroccan Meseta has been performed. Results indicate that two open folds with different amplitudes are recognized and that the one with wider wavelength could correspond to a lithospheric fold as previously stated by other authors on the basis of independent geological arguments. The northward tilting proposed based on the AFT data agrees with the results obtained in the analysis of the topography which reinforces the presence of a very open fold with a wavelength of 200–300 km in the north-western limb of the Western Moroccan Meseta

Scanning electron‐acoustic microscopy of MgO crystals

The capability of scanning electron‐acoustic microscopy in the characterization of MgO crystals has been studied. The conditions for the observation of different surface and subsurface features in as‐grown and deformed crystals are described and the results are discussed on the basis of thermal and nonthermal mechanisms of acoustic signalgeneration

Study of magnetic domains in amorphous ribbons by scanning electron acoustic microscopy

Scanning electron acoustic microscopy (SEAM) has been used in the observation of domain walls in iron- and cobalt-based amorphous alloys ribbons. Controlled magnetic annealing experiments enabled the direct identification of domain walls in SEAM micrographs. Walls in perpendicular anisotropy regions of the high magnetostriction samples show a particular high contrast, probably related to the wall stress field

Temperature-dependence of scanning electron acoustic microscopy signal in MgO and SIC

The variation of the electron acoustic signal as a function of temperature in ceramic materials has been studied. Scanning electron acoustic microscopy (SEAM) contrast in MgO single crystals and in reaction bonded SiC, between 100 and 273 K, is discussed and compared. SEAM signal and contrast have been found to be temperature dependent in both materials as a consequence of the temperature dependence of several material parameters

Application of scanning electron acoustic microscopy to the characterization of n-type and semiinsulating GaAs

A series of GaAs wafers with different doping levels and electrical resistivity has been used to investigate the scanning electron acoustic microscopy (SEAM) application to the characterization of this material. It has been found that SEAM is particularly useful to characterize semi-insulating GaAs as compared with n-type material. The SEAM signal generation mechanisms in GaAs are discussed