Charge transfer enabled by the p-doping of WSe₂ for 2D material-based printable electronics

Figures & data

Figure 1. (a) UV-visible spectrum of the as-prepared WSe₂ solution. The inset shows the photograph of each dispersion in isopropanol. (b) Raman spectra of WSe₂. The inset shows the atomic displacement of the E_2g¹ and A_1g Raman-active modes. (c) AFM image of the exfoliated WSe₂ nanoflakes and the corresponding height profile (scale bar: 500 nm). (d) High-resolution TEM image of the exfoliated WSe₂ nanoflakes. The inset shows the selected-area electron diffraction image (scale bar: 2 nm).

Figure 2. (a) Schematic of transistor fabrication by drop-casting with the 2D ink. (b) Optical micrograph of the as-fabricated WSe₂ transistor (scale bar: 100 µm). (c) Cross-sectional TEM image of the WSe₂ thin film on the Si/SiO₂ substrate (scale bar: 20 nm).

Figure 3. (a) I_DS–V_GS transfer curves at V_DS = −1 V for the pristine and FeCl₃-doped WSe₂ (60 µg/mL) TFTs on a SiO₂/Si substrate with a 100 nm-thick SiO₂ layer. V_DS is −1 V. The width and length of the channel are 725 and 50 µm, respectively. (b) Output curve of the corresponding FeCl₃-doped WSe₂ TFT. (c) UPS spectra showing the secondary electron cut-off and (d) valence band of pristine and FeCl₃-doped WSe₂ thin films (60 µg/mL). (e) Schematic energy diagram of the Ni/Au and WSe₂ contacts before and after doping. (f) Schematic energy diagram at the interface between the nanoflakes in the channel with a bias voltage applied after doping.

Figure 4. Solution-processed complementary metal-oxide-semiconductor (CMOS) inverter. (a) Circuit diagram of the CMOS inverter. (b) Schematic of a CMOS inverter with p-WSe₂ and n-MoS₂ channels. (c) Voltage transfer characteristics of the CMOS inverter as a function of the input voltage with different V_DD values from 1 to 8 V. The FeCl₃-doping concentration for p-WSe₂ is 60 µg/mL. (d) Corresponding gains of the inverter from c at V_DD = 8 V.