Technical. This project addresses new understanding and progress in fabricating novel nanodot and nanowire arrays of semiconductors and ferromagnets. The approach involves a multi-step process using porous alumina templates, and is being studied for precise control of nanopatterns and its use in fabrication of novel nanoarrays. Synthesis and processing phenomena associated with the fabrication of vertically heterostructured, ferromagnet/semiconductor nanodevices based on MBE-grown III-V semiconductors and Heusler alloys will be pursued. Nanowires of GaAs have been achieved via MBE using Au-catalyzed vapor-liquid-solid (VLS) growth and will be further studied on this project for growing arrays of hybrid nanowires composed of ferromagnetic (e.g., MnAs) and semiconducting materials. A wide range of experimental tools and expertise will be utilized for systematic investigations aimed at gaining greater fundamental understanding of electrical, magnetic, and optical properties of nanostructured materials and devices. Non-Technical. The project addresses fundamental research issues in a topical area of electronic/photonic materials science having technological relevance. There is potential that the research could substantially impact the development of novel electronic devices such as nonvolatile memories and nanowire electronic circuits. Development of novel nanostructures could even open doors to new device designs never before contemplated. Educating and training young people in the areas of electronic, magnetic and optical nanostructures--areas which are crucial for future applications in information technology is of primary importance to this project. In addition to training students in diverse aspects of science and engineering, this project couples with existing educational outreach to K-12 students, women, and underrepresented groups through activities in programs already established at Northeastern University with active participation by these PIs. Four to eight undergraduates will contribute to the research through Northeastern's unique Co-op program, and high school students will be involved in summer research programs.
The research provided benefits to society at large through education and scientific advances, by expanding our understanding of the fundamental physics of new materials and devices. This is necessary for producing faster/smaller/cheaper devices for information technology. This "green" miniaturization will also have a significant impact on reducing energy consumption. Technological advances in the information age are greatly enabled by our ability to reduce the dimensions and operating power of devices by inventing and improving relevant materials. A major goal of the funded project was the investigation of ferromagnet/semiconductor nanostructures and nanocomposites that are aimed at future electronic devices. Thirty archival papers were published that included approximately 70 coauthors. Graduate, undergraduate and high school students worked on research projects, and many published papers as first authors. A number of important discoveries were enabled by this grant: developed giant coercivity in rare-earth-free MnxGa magnets rivaling that in rare-earth magnets; discovered a universal explanation of linear magnetoresistance; induced ferromagnetism in nonmagnetic Bi2Se3 Topological Insulator by proximity to EuS; created a method to determine size distribution of magnetic nanoparticle using only thermomagnetic measurements; and the US patent application 0067403.00274US2, "Large magnetic coercivity in nanostructured rare-earth-free MnxGa films." On these projects, many students received training in state-of-the-art science and technology. The training involved a wide range of disciplines – fundamental physics to materials science to device engineering. The scope of technologies and scientific specialties encompassed many areas, including semiconductors, magnetism, and nanoscale physics.
