Science Advances

Supplementary Materials

This PDF file includes:

  • section S1. Electrical characterization of MoS2 samples
  • section S2. Surface analysis and optical contrast change
  • section S3. Spectroscopy
  • section S4. Scanning/transmission electron microscopy
  • section S5. Simulation of conductive networks
  • fig. S1. Cross section of the plasma cleaner (61).
  • fig. S2. Optical micrographs of various MoS2 devices after EBL processing.
  • fig. S3. Sketch of the experimental geometry.
  • fig. S4. VTH consistency check: The electrical measurement has negligible effects on the transfer curve of the sample without plasma treatment, with the threshold voltage not affected by hysteresis at the used sweep rate of ~2 V/s.
  • fig. S5. Full data set of electrical measurements for samples of all thicknesses.
  • fig. S6. Full data set of mobilities derived for samples of all thicknesses over plasma exposure time.
  • fig. S7. Full data set of subthreshold swings derived for samples of all thicknesses over plasma exposure time.
  • fig. S8. The effect of keeping a plasma-tuned sample in SEM vacuum chamber overnight.
  • fig. S9. Optical micrographs of a few-layer flake exposed to pure Ar plasma for several minutes.
  • fig. S10.
  • fig. S11. AFM height maps of the flake discussed in the main manuscript after 0, 2, 6, and 8 s of plasma exposure (from top to bottom), with line profiles extracted from the marked edges.
  • fig. S12. Visible drop in optical contrast of a 4L MoS2 flake after 28 s of plasma treatment visualized in the intensity drop of each individual RGB channel relative to the substrate.
  • fig. S13. SEM images of the sample treated for 28 s, showing small pit-like visible regions of dark contrast, as well as significant change to the material on the bottom edge of the flake.
  • fig. S14. Fits of the MoS2 Raman peaks used to extract peak shifts in the 4L sample in the main manuscript.
  • fig. S15.
  • fig. S16.
  • fig. S17. Thin area of MoS2 contained in a polymethyl methacrylate stamp after transfer from substrate onto the TEM grid.
  • fig. S18.
  • fig. S19.
  • fig. S20.
  • fig. S21.
  • fig. S22.
  • fig. S23. HRTEM images (beam energy = 300 keV) of monolayer MoS2 after plasma exposure for (from left) 0, 2, 5, 10, and 20 s.
  • fig. S24. HRTEM images (beam energy = 300 keV) of few-layer MoS2 after plasma exposures for (from upper left reading to the right) 0, 4, 16, and 31 s.
  • fig. S25. STEM images (beam energy = 20 keV) of few-layer MoS2 flakes taken in a SEM using a transmission detector.
  • fig. S26. High-angle annular dark-field (HAADF) STEM images (beam energy = 300 keV in FEI TITAN) of same samples as in fig. S21; plasma-treated for 16 s.
  • fig. S27. Medium-angle annular dark-field AC-STEM image (beam energy = 60 keV in Nion UltraSTEM 200) of pristine bilayer MoS2 before any plasma treatment.
  • fig. S28. HAADF AC-STEM images (beam energy = 60 keV in Nion UltraSTEM 200) of few-layer MoS2 plasma-treated for 6 s.
  • fig. S29. HAADF AC-STEM images (beam energy = 60 keV in Nion UltraSTEM 200) of few-layer MoS2 plasma-treated for 8 s.
  • fig. S30. Simulation of bilayer MoS2 with a peeled monolayer area and a perforated void carried out in QSTEM software.
  • fig. S31.
  • fig. S32. Close-to-normal distributions of residuals from data fits seen in Fig. 4B of the main manuscript, confirming goodness of linear fit.
  • fig. S33. Histograms summarizing distribution of areas of etched pits after 6 and 8 s of plasma treatment.
  • fig. S34. Distribution of lateral sizes of voids after 8 s of etching.
  • fig. S35. Mapping regions scanned in the Nion UltraSTEM 200 at 60 keV for locally resolved spectroscopies of few-layer MoS2.
  • fig. S36. Plot of concentration of the three phases in the simulation as they change with iteration number.
  • fig. S37. Trial-and-error plots for different combinations of conductances between the three phases C1, C2, and C3.
  • fig. S38.
  • scheme S1. Cartoon of multilayer MoS2 sample being oxidized by Ar/O2 plasma from both sides when the sample is suspended on a TEM grid.
  • table S1. Peak shifts with exposure time for the Mo4+ 5/2 and Si 2s peaks relative to the C 1s core line, indicating that shifts are due to doping and not substrate charging.
  • References (60, 61)

Download PDF

Files in this Data Supplement: