Long-term stability and tree-ring oxidation of WSe₂ using phase-contrast AFM

Abstract

Phase contrast atomic force microscopy shows how tungsten diselenide oxidation evolves into complex patterns over 75 months, following season-dependent changes in the laboratory environment, in analogy with tree-rings in nature.

High-Temperature Annealing Effects on Atomically Thin Tungsten Diselenide Field-Effect Transistor

“…The increased surface roughness in AFM measurement also corresponds to the formation of new traps. The observations such as quenching in the Raman spectrum, increased overall conductivity of WSe 2 , an increase in p-type behavior and an increase in surface roughness can be attributed to partial oxidation of WSe 2 to WO x as reported in previous studies [43][44][45][46][47][48]. Based on these observations, it can be assumed that in our WSe 2 device, the WSe 2 became oxidized during high-temperature annealing.…”

WSe2 as Transparent Top Gate for Infrared Near-Field Microscopy

“…In addition, the bottom gate provides a reference for determining the plasmon wavelength λ p as a function of the induced carrier density n . Over the course of 2 months, we did not observe any signs of degradation of the WSe 2 , despite carrying out the experiments in ambient conditions …”

“…9 In addition, the bottom gate provides a reference for determining the plasmon wavelength λ p as a function of the induced carrier density n. Over the course of 2 months, we did not observe any signs of degradation of the WSe 2 , despite carrying out the experiments in ambient conditions. 35 Figure 3a shows a near-field image of BLG with doping n ∼ 10 13 cm −2 induced by the bottom gate at V B = 80 V along with photodoping, but with V T = 0. Photodoping involves photoexciting defect states at the SiO 2 /hBN interface, 8,36 which effectively sets the charge-neutrality point V D at −65 V, as extracted from the maximum of the measured source-drain resistance.…”

$WSe_2$ as transparent top gate for near-field experiments

“…The Si/SiO 2 bottom gate serves as a backgate to bring BLG into a highly doped state where plasmons do not suffer from Landau damping 9 . In addition, the bottom gate provides a reference for determining the plasmon wavelength λ p as function of the induced carrier density n. Over the course of two months, we did not observe any signs of degradation of the WSe 2 , despite performing the experiments in ambient conditions 35 .…”