posted on 2018-05-17, 00:00authored byMin-Hye Jeong, Do-Hyun Kwak, Hyun-Soo Ra, A-Young Lee, Jong-Soo Lee
Few-layer
black phosphorus (BP) has shown great potential for next-generation
electronics with tunable band gap and high carrier mobility. For the
electronic applications, the thickness modulation of a BP flake is
essential due to its thickness-dependent electronic properties. However,
controlling the precise thickness of few-layer BP is a challenge for
the high-performance device applications. In this study, we demonstrate
that thermal treatment under ambient condition precisely controls
the thickness of BP flake. The thermal etching method utilizes the
chemical reactivity of BP surface with oxygen and water molecules
by the repeated formation and evaporation of phosphoric acid during
thermal annealing. Field-effect transistor of the thickness-modulated
BP sheet by thermal etching method shows a high hole mobility of ∼576
cm2 V–1 s–1 and a high
on–off ratio of ∼105. The stability of the
BP devices remained for 1 month under ambient condition without an
additional protecting layer, resulting from the preservation of active
BP layers below native surface phosphorus oxide.