Non-Destructive Observations of Internal Micro-Defects Using Scanning Electron-Induced Acoustic Microscope

Abstract

Scanning electron-induced acoustic microscope (SEAM) has been developed as a new tool for non-destructive observations of the internal microstructures of materials. It consists of the electric chopper to pulse the high current electron beam and the detector of the longitudinal acoustic waves, both being attached to the commercial scanning electron microscope (SEM). The cyclic chopping of electron beam with extremely high frequency of a few hundred kilohertz makes the thermal wave due to the cyclic temperature rise with the short period. The wavelength of thermal wave may determine the essential SEAM resolution, because it's much smaller than the thermal stress wave (that is, the acoustic wave), which has just the role of conveying the information of thermal wave disturbance due to unexpected change as defects. Our own-built SEAM gives the best performance for observing the internal defects like the micro-voids, because it susceptibly senses the local difference of thermal properties in the sample. The paper indicates that some non-destructive observations for the micro-voids with a few microns order existing in the sintered materials are exhibited in conjunction with their destructive observations using focused-ion beam (FIB) technique to make certain of those as the proof.

Non-destructive observations of small crack using scanning laser-induced acoustic microscope

“…The radiographic inspection equipment, in fact, is the non-destructive way, while it has lower resolution compared with TEM or SEM. Then, we have developed the scanning electron-induced acoustic microscope (SEAM) (Shibutani et al, 2006;Koyama and Shibutani, 2012). SEAM has been originally proposed by Cargill (Cargill, 1980), Brandis & Rosencwaig (Brandis and Rosencwaig, 1980) and Rosencwaig (Rosencwaig, 1982) as one of the methods of non-destructive detection of internal micro-defects and structures.…”

“…SEAM is the observational equipment which has high resolution and can be used easily. SEAM has been successfully applied to the non-destructive observations of the delamination of an integrated circuit (Rosencwaig, 1982), interface defects of multi-layered electric chips (Takenoshita, 2000), micro-voids of sintered material (Koyama and Shibutani, 2012), and so on. However, SEAM can only observe conductive materials.…”