Frontiers in Materials Science, Engineering, and Technology: An FMD Symposium in Honor of Sungho Jin: Process-Property-Performance Correlations: Ferrites, Alloys, Devices & Systems
Sponsored by: TMS Functional Materials Division, TMS: Biomaterials Committee, TMS: Electronic Packaging and Interconnection Materials Committee, TMS: Nanomaterials Committee, TMS: Thin Films and Interfaces Committee
Program Organizers: Fay Hua, Intel Corporation; Tae-Kyu Lee, Portland State University; Young-Ho Kim, Hanyang University; Roger Narayan, University of North Carolina; Choong-un Kim, University of Texas at Arlington; Nuggehalli Ravindra, New Jersey Institute of Technology
Wednesday 8:30 AM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Fay Hua, Intel; Seong Koh, University of Texas - Arlington
8:30 AM Introductory Comments
8:40 AM Invited
Enhanced Magnetic Properties and Spin-Seebeck Effect in Epitaxial Spinel Ferrite Thin Films Grown on Lattice-Matched Substrates: Arunava Gupta1; 1University of Alabama
Ferrite films are important for a number of technological applications. However, thin films of ferrites suffer from a number of drawbacks, e.g. formation of antiphase boundaries. We show that by using substrates having similar crystal structure and low lattice mismatch one can avoid formation of antiphase boundaries in spinel ferrite films and thereby obtain magnetic properties comparable to bulk single crystal. As an example, we have used spinel MgGa2O4 (MGO) and CoGa2O4 (CGO) substrates, which have 0.8% and 0.2% lattice mismatch, respectively, with NiFe2O4 to grow films that are free of antiphase boundaries and show sharp magnetic hysteresis characteristics. Moreover, low Ferromagnetic Resonance (FMR) linewidths are obtained. We have also investigated spin transport properties in the films via the longitudinal spin Seebeck effect (LSSE). We observe an increase in the spin voltage signal with reduction in lattice mismatch, which is in correspondence with similar improvements in structural and magnetic properties.
Domain Mechanisms for Magnetization and Deformation Behaviors of Fe-Ga Alloys: Matt Tianen1; Yongmei Jin1; 1Michigan Tech
Fe-Ga alloys exhibit significant magnetostriction under low magnetic field, show very small hysteresis, and perform under both compression and tension, making them very promising for actuator and sensor applications. To understand domain mechanisms underlying their magnetization and deformation behaviors, coupled magnetic and elastic domain evolutions under external magnetic and mechanical conditions are investigated. In-situ domain observation experiments using interference-contrast-colloid technique and computer simulations using phase field micromagnetic microelastic modeling are employed. Various domain patterns and complex domain evolutions are observed in Fe-Ga single crystals. The experimental results are explained using the computer simulations, revealing the important roles of competing long-range elastostatic and magnetostatic interactions in the domain phenomena. The domain mechanisms for magnetization and deformation in Fe-Ga alloys and their distinctive features from other magnetoelastic materials are discussed.
9:30 AM Invited
Spintronic Integrated Circuits:
Scalable Magnetic Nano Devices for Energy-Efficient and Secure Systems: Seung Kang1; 1Qualcomm Technologies, Inc.
Spintronic integrated circuits (ICs) are made of semiconductor ICs coupled with a dense array of magnetic tunnel junctions (MTJs). This emerging field is of growing interest owing to its potential to bring disruptive device innovation to advanced electronic systems. Most recognized is spin-transfer-torque magnetoresistive random access memory (STT-MRAM). Utilizing CoFeB-based perpendicular MTJ (pMTJ), STT-MRAM has reached a level of maturity to enable early products. Persistent innovations are desired, however, to serve deeply scaled semiconductor nodes. The success of STT-MRAM largely hinges on the pMTJ scaling path. Any sustainable innovation in materials or process must account for these requirements simultaneously. Beyond memory applications, MTJs may be applied for a variety of Spin-Logic and security devices. We highlight key discoveries and breakthroughs in light of the broader perspective of their applications for energy-efficient and secure information processing and storage.
10:00 AM Break
10:20 AM Invited
Ohmic Contacts for High-efficiency GaN-based Light-emitting Diodes: How to Enhance Current Injection Efficiency: Tae-Yeon Seong1; 1Korea University
GaN-based LEDs are technologically important because of their applications, such as display, signage, solid-state lighting and automotive headlight. To realize such applications, the enhancement of output power and low turn-on voltage of LEDs is essential. In this talk, we present ways of enhancing current injection efficiency through the formation of transparent and reflective ohmic electrodes. Various design rules are suggested to enhance current injection efficiency, such as the control of surface Fermi-level through surface etching, barrier tunneling, the modification of Schottky barrier heights (SBHs) by introducing nano-structures at the contact/GaN interface, control of native defects in GaN surface regions. On the basis of X-ray photoemission spectroscopy (XPS), Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM), and X-ray diffraction results, the ohmic formation and electrical degradation mechanisms are described and discussed. In addition, works on non-polar/semi-polar GaN are also presented.