Formation scheme of quantum point contacts based on nanogaps using field-emission-induced electromigration

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Quantum point contacts (QPCs) are crucial for quantum electronics.
• Fabricating stable QPCs, especially at room temperature, remains a challenge.
• Existing methods often require cryogenic conditions or complex lithography.

Purpose of the Study:

• To introduce a novel room-temperature fabrication scheme for quantum point contacts (QPCs).
• To demonstrate the formation of few-atom nickel contacts using a specific electromigration technique.
• To investigate the electrical properties and magnetoresistance of the fabricated Ni QPCs.

Main Methods:

• Utilizing electromigration induced by field emission current (activation) on ferromagnetic Ni nanogaps with sub-10 nm separation.
• Precisely controlling the preset current (Is) during activation to tune the nanogap formation.
• Measuring the conductance and magnetoresistance (MR) of the resulting QPC devices.

Main Results:

• Successfully fabricated QPCs from Ni nanogaps at room temperature via activation.
• Observed quantized conductance steps of 0.5G0 (G0 = 2e2/h) at the final stage of activation.
• Demonstrated tunable conductance from 2G0 to 9.5G0 by varying the preset current from 0.5 mA to 1.5 mA.
• Achieved a magnetoresistance (MR) ratio of approximately 1.5% in the activated QPC devices.

Conclusions:

• The proposed activation scheme provides an effective route for room-temperature fabrication of few-atom Ni contacts.
• Precise control over preset current allows for tuning of conductance and formation of stable QPCs.
• The resulting Ni QPCs exhibit promising magnetoresistance properties for potential applications.