  A method for assessing the quality of electronic material properties of
thin-film metal oxide semiconductor field-effect transistors (MOSFETs) is
presented. By investigating samples with MOCVD-grown MoS${_2}$ channels exposed
to atmospheric conditions, the existence of electron traps in MoS${_2}$ and at
the interface between the gate insulator and the thin-film MoS${_2}$ are
revealed. Differential conductance and capacitance data of the transistor
channels are plotted as 3D surfaces on a base plane spanned by the measurement
frequency versus the gate voltage. The existence of defects is confirmed by
comparison with ideal results from a theoretical model.
