Hole-Dominated Altermagnetic RuO₂ Thin Films Prepared by Reactive Sputtering

Ruthenium dioxide (RuO2) is one of the novel altermagnetic materials. The interleaved antiferromagnetic ordering and the high conductivity provide a potential application for the development of spintronic devices. However, controversies remain regarding its canted magnetism. Therefore, high-quality RuO2 thin films are crucial for investigating electric and magnetic properties. In this work, RuO2 thin films were deposited on Si(100) substrates by reactive magnetron sputtering. Physical properties were tuned by optimizing the argon/oxygen ratio and growth temperature. The oxygen partial pressure could modify the carrier type from electron-dominated to hole-dominated. This result challenged the conventional understanding that N-type carriers dominate in bulk RuO2. X-ray photoelectron and Raman spectroscopy analyses suggested this transition might stem from variations in oxygen vacancy concentration, which could have induced either band structure distortion or changes in defect energy levels. X-ray diffraction and atomic force microscopy revealed temperature-dependent crystal orientation transitions and surface morphology evolution. Additionally, weak antilocalization effects were observed at 2 K, highlighting quantum interference dominated by spin–orbit coupling. As RuO2 was identified as a rare p-type metal oxide, this work may help to resolve controversies about its magnetism and offer a novel p-type magnetic material for spintronic applications.