Anomalous Hysteresis in Graphite/Boron Nitride Transistors

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Van der Waals (vdW) heterostructures with hexagonal boron nitride (hBN) dielectrics typically show minimal hysteresis.
• Sporadic observation of a significant hysteresis, termed
• electron ratchet
• effect, has been reported in vdW devices.
• Previous hypotheses linked this hysteresis to specific vdW material combinations like bilayer graphene and moiré patterns in hBN.

Purpose of the Study:

• To investigate the origin of the anomalous hysteresis effect in vdW devices.
• To identify the material and structural conditions that lead to the observed hysteresis.
• To explore the characteristics and potential applications of this phenomenon.

Main Methods:

• Fabrication of field-effect devices using thicker graphite channels.
• Characterization of device behavior at room temperature.
• Inclusion of a WSe₂ monolayer to probe the effect's dependence on material interfaces.

Main Results:

• The anomalous hysteresis effect was observed in devices with thicker graphite channels, linked to a single graphite surface.
• The hysteresis was found to persist at room temperature, independent of intentional hBN alignment.
• The effect remained even with a WSe₂ monolayer inserted, and exhibited continuous relaxation over extended time scales.

Conclusions:

• The study provides new constraints on the origin of the
• electron ratchet
• effect, suggesting it is not solely dependent on bilayer graphene or moiré patterns.
• The persistence of hysteresis at room temperature and its relaxation dynamics offer insights into charge trapping or transport mechanisms.
• Mastering this hysteresis could unlock novel applications in electronic devices.