Sub-Nanometer Thick Wafer-Size NiO Films with Room-Temperature Ferromagnetic Behavior

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Integrating ferromagnetism into semiconductors is crucial for spintronic devices like spin field-effect transistors.
• A significant challenge is achieving stable ferromagnetism in these materials above room temperature.

Purpose of the Study:

• To develop a method for growing wafer-size NiO thin films with controllable sub-nanometer thickness.
• To investigate the origin of ferromagnetism in these thin films and their potential for novel devices.

Main Methods:

• An atomic chemical-solution strategy was employed to grow wafer-size NiO thin films.
• Film thickness was controlled down to 0.92 nm.
• Surface lattice defects were analyzed as a source of magnetic symmetry breaking.

Main Results:

• The study successfully produced wafer-size NiO thin films with controllable sub-nanometer thickness.
• Surface defects were identified as the cause of surface ferromagnetic behaviors.
• The sub-nanometric NiO thin film demonstrated the highest reported room-temperature ferromagnetism (157 emu/cc saturation magnetization, 418 Oe coercivity).
• The films were successfully integrated into a magnetoresistance device, demonstrating their practical applicability.

Conclusions:

• This work presents a novel sub-nanometric platform for producing wafer-size ferromagnetic NiO thin films.
• These films can serve as atomic layer magnetic units for future transparent magnetoelectric devices.
• The findings overcome the challenge of room-temperature ferromagnetism in semiconductor-based spintronic applications.