Orthorhombic HfO₂ with embedded Ge nanoparticles in nonvolatile memories used for the detection of ionizing radiation

Abstract

Trilayer memory capacitors of control HfO₂/floating gate of Ge nanoparticles in HfO₂/tunnel HfO₂/Si substrate deposited by magnetron sputtering and subsequently annealed are investigated for the first time for applications in radiation dosimetry. In the floating gate (FG), amorphous Ge nanoparticles (NPs) are arranged in two rows inside the HfO₂ matrix. The HfO₂ matrix is formed of orthorhombic/tetragonal nanocrystals (NCs). The adjacent thin films to the FG are also formed of orthorhombic/tetragonal HfO₂ NCs. This phase is formed during annealing, in samples with thick control HfO₂, in the presence of Ge, being induced by the stress. In the rest of the control oxide, HfO₂ NCs are monoclinic. Orthorhombic HfO₂ has ferroelectric properties and therefore enhances the memory window produced by charge storage in Ge NPs to above 6 V. The high sensitivity of 0.8 mV Gy^-1 to α particle irradiation from a ²⁴¹Am source was measured by monitoring the flatband potential during radiation exposure after electrical writing of the memory.