The Role of Chemical and Structural Disorder at Buried Interfaces in Hexaferrite Heterostructures: Implications to Microwave Integrated Electronics
Abstract
Northeastern University, in collaboration with KRI at Northeastern University, LLC proposes to investigate and establish fundamental interrelationships between local structural and chemical properties of ferrite/BL/semiconductor heterostructures (BL: strain mitigating buffer layers) and electrodynamics and gyromagnetic behavior. These interrelationships will elucidate the origins of magnetocrystalline anisotropy, magnetic spin waves, breaking of time reversal symmetry, and relaxation and damping behavior. Findings will provide a viable path to the development of next generation, magnetic microwave/mm-wave devices that are planar, self-biased, low-loss and monolithically integrated with active semiconductor device platforms, i.e. practical active-passive device integration. Practical active-passive device integration has yet to be realized due largely to technical challenges resulting from a lack of a fundamental knowledge base relating the structure, chemistry, and defects of interfacial regions with ferrite gyromagnetic properties and the mobility of charge carriers in the semiconductor and across key metallurgical junctions. For example, despite having a similar hexagonal crystal structure, select semiconductor substrates still experience large atomic lattice mismatches giving rise to strain and copious defects. Additionally, interdiffusion at the interface further worsens the quality and performance of the ferrite - semiconductor heterostructure by injecting charge carriers and creating disorder in the arrangement of ions in the proximity of the ferrite-semiconductor interfaces. Further degradation may result from residual strain and related defects originating from dissimilar thermal expansion coefficients. The objectives of this proposed research program are: 1) Explore the interrelationships between thin film growth dynamics (i.e., pulsed laser energy and density, substrate temperature, background pressure, component geometries) and fundamental (i.e., atomic and electronic structure and defects) and functional properties (i.e., magnetization, coercivity, retention, permeability, permittivity and related losses) as they pertain to the performance of materials and rf passive devices operating at microwave/mm-wavelengths (i.e., insertion loss, isolation, return loss, bandwidth). Principle characterization techniques comprise of x-ray diffraction and electron microscopy including high-resolution SEM and TEM. 2) Explore the interrelationships between film growth dynamics upon the properties of interfaces formed at the boundaries of substrate and nucleation layers and nucleation layers and the magnetodielectric film (i.e., hexaferrite). Such techniques as cross-sectional HR-TEM will be employed to quantitatively measure the structural, chemical and defect properties of interfacial regions and correlate these with functional properties.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 09, 2020
- Source ID
- W911NF2010069
Entities
People
- Vincent G. Harris
Organizations
- Army Contracting Command
- Northeastern University
- United States Army