Metallic Bi-Rh-O thin films with p-type conduction

Transition metal oxides with partially filled 4d and 5d orbitals have recently been viewed as promising target materials for the discovery of novel properties, due to their strong spin-orbit coupling that can generate exotic electronic states. Here, we report the fabrication of three kinds of Bi-Rh-O compounds. They are synthesized by the deposition of amorphous films at room temperature by pulsed laser deposition and subsequent annealing in a tube furnace under O₂ atmosphere. On Y-ZrO₂ (111) substrates, two novel compounds with supercell structures [Bi_nO_n]-[RhO₂] (n = 3, 2) are synthesized at annealing temperatures (T_anneal) of 700 °C and 900 °C, respectively. When a buffer layer of pyrochlore oxides is deposited on Y-ZrO₂, single crystalline pyrochlore Bi₂Rh₂O₇ is stabilized at T_anneal of 1,000 °C. These results demonstrate the critical role of the interface-engineering in stabilizing certain crystal structures, which will pave the way for further exploration of Rh oxides and materials design of transition metal oxides. Hall resistivity at 2 K is merely linear to an applied magnetic field with a positive slope for all the compounds, and the estimated carrier densities are p = 3×10²¹ cm^-3 ([Bi₂O₂]-[RhO₂]), 6×10²¹ cm^-3 ([Bi₃O₃]-[RhO₂]), and 1×10²³ cm^-3 (Bi₂Rh₂O₇). The magnetoresistance at 2 K shows quadratic ([Bi₂O₂]-[RhO₂]) and linear ([Bi₃O₃]-[RhO₂], Bi₂Rh₂O₇) field dependence, suggesting strong spin-orbit coupling.