Plasma-Treated Thickness-Controlled Two-Dimensional Black Phosphorus and Its Electronic Transport Properties

We report the preparation of thickness-controlled few-layer black phosphorus (BP) films through the modulated plasma treatment of BP flakes. Not only does the plasma treatment control the thickness of the BP film, it also removes the chemical degradation of the exposed oxidized BP surface, which results in enhanced field-effect transistor (FET) performance. Our fabricated BP FETs were passivated with poly(methyl methacrylate) (PMMA) immediately after the plasma etching process. With these techniques, a high field-effect mobility was achieved, 1150 cm²/(V s), with an <i>I</i>_on/<i>I</i>_off ratio of ∼10⁵ at room temperature. Furthermore, a fabricated FET with plasma-treated few-layer BP that was passivated with PMMA was found to retain its <i>I</i>–<i>V</i> characteristics and thus to exhibit excellent environmental stability over several weeks