Diffraction analysis of elastic strains in micro- and nanostructures

摘要

Very high stresses arise in thin films and in nanosized structures (lines, dots) because of the constraint of the substrate to which they are attached. The mechanical behavior of these small structures can deviate significantly from scaling laws developed for bulk materials. Moreover, the origins and magnitudes of these stresses are of great interest in technology as many fabrication and reliability problems are stress related. X-ray diffraction has at least three distinct advantages with respect to strain measurements: 1) it is very sensitive to atomic displacements; 2) it is non-destructive; 3) it can yield the six elements of the strain tensor. In objects with small dimensions stress gradients can arise from the proximity of surfaces or interfaces. The knowledge of strain distributions in such objects is necessary in order to understand their properties. The need to characterize displacement fields in nanostructures together with the advent of third generation synchrotron radiation sources has generated new and powerful methods (coherent diffraction, micro-diffraction, ...). This paper reviews some of the recent and promising results in the field of strain measurements in small dimensions via X-ray diffraction.