Three-dimensional characterization of near-field transducers by electron tomography

Transmission electron microscopy (TEM) was employed to study the structure of near-field transducers (NFT) for applications in heat-assisted magnetic recording (HAMR) heads. The overall shape of NFTs that had passed or failed an optical test was similar, as determined by scanning transmission electron microscopy tomography. However, the absence of a well-defined peg and the presence of a flat top on the ‘FAIL’ NFT disk induced poor thermal heat transfer from the NFT to the phase change medium and resulted in the optical test failure. The thermal heating around the NFT led to Ta diffusion from the adjacent tantala core and to the presence of Ta-rich particles in the alumina matrix in the plane of the NFT.