Study of the electrical and structural homogeneity of ultrathin HfO2 films grown by reactive sputtering

HfO2 is often used in the development of various microelectronic devices requiring high-quality ultrathin insulating layers. In this work, we used conductive Tunneling Atomic Force Microscopy (TUNA) to study the insulating properties of ultra-thin HfO₂ films grown at room temperature on superconducting molybdenum nitride electrodes by reactive sputtering, deposited on (100) silicon wafers. The results indicate that the HfO₂ layers are homogeneous and exhibit excellent insulating properties, with no pinholes even at a thickness of 0.5 nm. TUNA-based current-voltage measurements at room temperature indicate a charge carrier attenuation length of 0.13 nm and an estimated energy gap of 2.8 eV. The thickness distribution width of the layers is very low (∼0.06 nm), consistent with a low surface roughness (<0.2 nm). These results confirm the robust insulating properties of room-temperature-deposited HfO₂, making it a highly suitable material for the development of microelectronics devices.