Nanoscale inhomogeneity of the Schottky barrier and resistivity inMoS2multilayers

Abstract

Conductive atomic force microscopy (CAFM) is employed to investigate the current injection from a nanometric contact (a Pt coated tip) to the surface of ${\text{MoS}}_{2}$ thin films. The analysis of local current-voltage characteristics on a large array of tip positions provides high spatial resolution information on the lateral homogeneity of the $\mathrm{tip}/{\text{MoS}}_{2}$ Schottky barrier ${\mathrm{\ensuremath{\Phi}}}_{B}$ and ideality factor $n$, and on the local resistivity ${\ensuremath{\rho}}_{\text{loc}}$ of the ${\text{MoS}}_{2}$ region under the tip. Here, ${\mathrm{\ensuremath{\Phi}}}_{B}=300\ifmmode\pm\else\textpm\fi{}24\phantom{\rule{0.28em}{0ex}}\text{meV}, n=1.60\ifmmode\pm\else\textpm\fi{}0.23$, and ${\ensuremath{\rho}}_{\text{loc}}=2.99\ifmmode\pm\else\textpm\fi{}0.68\phantom{\rule{0.28em}{0ex}}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\text{cm}$ are calculated from the distributions of locally measured values. A linear correlation is found between the ${\ensuremath{\rho}}_{\text{loc}}$ and ${\mathrm{\ensuremath{\Phi}}}_{B}$ values at each tip position, indicating a similar origin of the ${\ensuremath{\rho}}_{\text{loc}}$ and ${\mathrm{\ensuremath{\Phi}}}_{B}$ inhomogeneities. These findings are compared with recent literature results on the role of sulfur vacancy clusters on the ${\text{MoS}}_{2}$ surface as preferential paths for current injection from metal contacts. Furthermore, their implications on the behavior of ${\text{MoS}}_{2}$ based transistors are discussed.