Short-range order in amorphous oxygen-deficient TaOx thin films and its relation to electrical conductivity

Thin films of tantalum oxide hold promising functional properties for electronic applications such as resistive random-access memory. For this aim, correlating the structure and charge transport oxygen-deficient derivatives is crucial. Here, using electron scattering measurements from nanoscale volumes in a transmission microscope (TEM), we report how oxygen content affects short-range order amorphous TaOx thin films, where 1.34 ≤ x 2.50. By extracting bond lengths, observe that dominant type Ta–Ta distances change with decreasing next-nearest-neighbor, ∼3.8 Å, to nearest-neighbor, ∼3 Å. We relate decrease Ta–O polyhedral network within film, namely increases presence TaO5 at expense TaO6 polyhedra. The reduction accompanied by significant electrical resistivity over 4.3 × 103 (4 ± 0.05)×10−3 Ω cm. In particular, sharp percolative three orders magnitude, ∼ 1.9. Ta oxidation states, measured x-ray photoelectron spectroscopy, suggest main building block TaO2.5 film TaO6, while relative fractions polyhedra metallic increase. At even lower content, 1.34, TEM diffraction detect crystallites cubic metastable tetragonal structures. propose increase conductivity due direct bonding atoms, manifested nearest-neighbor length, thus enabling conductive paths transport.