Abstract

High purity alumina sample has been characterized via terahertz reconstructive lattice imaging technique. The camera-less technique uses a nanoscanner to create a digital three-dimensional representation of the sample via modified Beer-Lambert’s law, where, the reflected terahertz intensity is captured as a function of real coordinates on the sample of nanometer step size. This non-contact technique replaces the focusing lens and the focal plane array (e.g. a CCD) of a traditional camera which is limited by the Abbe diffraction limit. It was found that over a bigger area/volume, the generated images exhibit the amorphous nature of the alumina sample. However, when zoomed to a cubic micron volume, the nanograins are visible. The nanograins are more clarified in both the two-dimensional and threedimensional images upon further zooming, from which lattice parameters were quantified. Though the sample is comprised of nanograins, all grains are different in size and orientations, compared to each other. As such, while alumina is an amorphous material, it is composed of different kind of nanograins as revealed herein. A single nanograin was measured to be ~5.5nm. The lattice patterns within a nanograin are not identical either; indicating non-uniformity of lattice within a nanograin. In addition, nanovoids are also observed via layer-by-layer analysis. Two nanovoids were measured to be 2.78nm and 0.72nm, respectively. The technique is universal and may be applied to any material.