Electron beam induced local crystallization of HfO₂ nanopores for biosensing applications

We report the development of single, locally crystallized nanopores in HfO₂ membranes for biosensing applications. HfO₂ is chosen for its isoelectric point of 7.0, mechanical and chemical stability in solution, and for its potential as a high-k material for nanopore ionic field effect transistor applications. The HfO₂ membrane is deposited on a graphene layer suspended over a 300 nm FIB hole, where graphene is used as the mechanical support. Exposure of the membrane to a focused electron beam causes crystallization in the vicinity of the nanopore during pore formation. We investigate the effects of crystallization on the electrical and surface properties of HfO₂ films. Our surface analysis of HfO₂ reveals improved hydrophilicity of crystallized HfO₂, a notable advantage over the hydrophobicity of as-deposited HfO₂. We also demonstrate detection of dsDNA translocation through HfO₂ nanopores under various applied bias levels. In addition, our device architecture also presents a promising first step toward the realization of high-k HfO₂ nanopore transistors.