Figure 5
Origins of the responsivity variation.
(a) Reflectance and (b) responsivity as functions of vacuum gap depth d2 for 1L to 50L MoS2 devices. Curves for selected thicknesses are color highlighted (indicated in legends). (c) 3D plots of reflectance R and (d) responsivity ℜ as functions of device thickness (d1) and vacuum gap depth (d2) for 1L to 200L MoS2 devices. (e,f) are 2D color plots of (c,d), respectively, except that |ℜ| is plotted instead of ℜ, thus both positive and negative peaks both appear in the same direction on the color scale (dark purple: no responsivity; dark red: high |ℜ|). Dotted curves represent the positive (grey) and negative (black) responsivity peaks. Locations with d1 = mλ/(4nMoS2) and d2 = nλ/2 are shown as gridlines. A common device geometry (d2 = 300 nm) is indicated by the vertical dash-dot line. (g) Example interferometry condition when d1 = (1/2 + m)λ/(2nMoS2) and d2 = nλ/2 (“x” symbol in (e)). (h) Example interferometry condition when d1 = mλ/(2nMoS2) and d2 = nλ/2 (“+” symbol in (e)).
