Fig. 3: Electronic structure and transport properties of 111-junction in the presence of gas molecules.
From: Electronic fingerprint mechanism of NOx sensor based on single-material SnP3 logical junction
PDOS of 1L SnP3 with adsorbed gas molecules of a type A and b type B. Black, red, green, blue, and magenta colours indicate CH4, CO2, NH3, NO, and NO2, respectively. PDOS for each molecule are marked with colour-filled peaks and were scaled up ten times for visibility. Dashed lines represent the PDOS of the SnP3 substrate for each adsorption model, as indicated by SnP3(molecule) in the legend. Note that the states of CH4 lie outside the energy range plotted here. The red downwards arrow indicates the electronic state of CO2 near EF. c Top view (top) and side view (bottom) of the device (111-junction) used to calculate the transmission. Blue and orange shaded regions indicate the left and right leads, respectively. Transmission functions for 111-junction with each adsorbed gas molecule with d type A and e type B molecules, indicated by solid lines with the colour corresponding to those used in PDOS. The T(E, V = 0) of the pristine 111-junction is marked in grey. Note that this model is designed to observe the effect of molecular adsorption on electron transport, so that the dimension of this model is different from what is used in Fig. 1g (Supplementary Fig. 1) with which we compare pristine 111-, 222-, and 333-junctions without molecular adsorption. Furthermore, the model is designed to be also comparable to 3L SnP3 (metal)—1L SnP3 (semiconductor)—3L SnP3 (metal) junction which we will denote as 313-junction in the later part of this paper. In order to accommodate molecules in the scattering region and avoid the possible effects of edge states comes from the 1L-3L SnP3 interfaces, the scattering region in this model is longer by almost two times than what is used in Fig. 1g (Supplementary Fig. 1). The red downward triangles indicate the first transmission peaks above EF of the 111-junction with NO and NO2 adsorptions. Note that the slight difference between this T(E, V = 0) of pristine 111-junction and Fig. 1g comes from above-mentioned difference in the dimension of atomistic models.
