How the dynamic of photo-induced gate screening complicates the investigation of valley physics in 2D materials

Abstract

An in-depth analysis of valley physics in 2D materials like transition metal dichalcogenides requires the measurement of many material properties as a function of Fermi level position within the electronic band structure. This is normally done by changing the charge carrier density of the 2D material via the gate electric field effect. Here, we show that a comparison of gate-dependent measurements, which were acquired under different measurement conditions can encounter significant problems due to the temporal evolution of the charging of trap states inside the dielectric layer or at its interfaces. The impact of, e.g., the gate sweep direction and the sweep rate on the overall gate dependence gets especially prominent in optical measurements due to photo-excitation of donor and acceptor states. Under such conditions the same nominal gate-voltage may lead to different gate-induced charge carrier densities and, hence, Fermi level positions. We demonstrate that a current flow from or even through the dielectric layer via leakage currents can significantly diminish the gate tunability in optical measurements of 2D materials.

arXiv comment7 pages, 3 figures

References in corpus (18)

• Double-slit photoelectron interference in strong-field ionization of the neon dimer
• Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides
• Excitons in atomically thin transition metal dichalcogenides
• Optical Generation of Excitonic Valley Coherence in Monolayer WSe2
• Mechanisms of photoconductivity in atomically thin MoS2
• Photo-induced Doping in Graphene/Boron Nitride Heterostructures
• Long-lived nanosecond spin relaxation and spin coherence of electrons in monolayer MoS_2 and WS_2
• Charge-tuneable biexciton complexes in monolayer WSe${}_2$
• Valley-spin polarized Landau levels in a monolayer semiconductor
• Microsecond Valley Lifetime of Defect-Bound Excitons in Monolayer WSe${}_2$
• Probing the spin-polarized electronic band structure in monolayer transition metal dichalcogenides by optical spectroscopy
• Role of Charge Traps in the Performance of Atomically-Thin Transistors
• Band filling and cross quantum capacitance in ion gated semiconducting transition metal dichalcogenide monolayers
• Inter-valley dark trion states with spin lifetimes of 150 ns in WSe${}_2$
• Unveiling valley lifetimes of free charge carriers in monolayer WSe${}_2$
• Spin States Protected from Intrinsic Electron-Phonon-Coupling Reaching 100 ns Lifetime at Room Temperature in MoSe${}_2$
• Spatial control of laser-induced doping profiles in graphene on hexagonal boron nitride
• Semiconductor channel mediated photodoping in h-BN encapsulated monolayer MoSe2 phototransistors