Henry Chen (Committee Member), Robert C. Fitch (Committee Member), Robert E. W. Fyffe (Other), Ramana V. Grandhi (Other), Marian Kazimierczuk (Committee Member), Guru Subramanyam (Committee Member), Yan Zhuang (Advisor)
Doctor of Philosophy (PhD)
Integrated r-f passive components such as inductors, transmission lines, transformers etc, form the basic building blocks in r-f integrated circuits (RFICs) such as matching networks, low noise amplifiers (LNAs), synthesizers and r-f mixers. One main challenge faced by current technology developers in integrating r-f components on integrated chip (IC) are related to operation and size. Tremendous efforts were made for overcoming challenges of r-f integrated circuits to meet growing technology demands.
In general, r-f devices utilize magnetic materials such as ferrites for their operation for improving device performance and scaling. However, due to material properties and size ferrite materials are poor choices when attempting to scale r-f components. The main focus of this work has been to explore new material properties and investigate applications of ferromagnetic (FM) films as potential solution for device scaling. One attractive property of ferromagnetic materials is low processing temperature and high magnetic saturation which eliminates the need for continuous application of magnetic (d-c) field and are compatible with CMOS technology. The disadvantage of ferromagnetic films is high conductivity which induces ohmic losses and affects r-f device performance. In this work a novel concept of low-loss conductor has been introduced whose conductivity can be modeled by utilizing multilayered superlattice structure. The low-loss conductor is made of artificial layered metamaterial (ARLYM) consisting Ni80Fe20/Cu superlattice. By modeling thickness ratio between superlattice layers the skin effect has been suppressed by increasing skin depth at r-f frequencies. The experimental results presented in this work indicates significant improvement in r-f device characteristics such as inductance, quality factor (85%), loss reduction ratio (70%) etc, operating at r-f frequencies. In addition, application of continuous magnetic field was not required in this work due to magnetic anisotropy property in ferromagnetic materials. Further, a new approach for studying magneto-dynamics in thin ferromagnetic films has been investigated in this work by modeling r-f solenoid single-turn inductor fabricated using thin ferromagnetic core. The effect of magnetic resonances in thin ferromagnetic films has been calculated using magneto-static thin film approximation and Greens function. Therefore, these newly developed concepts of artificial low-loss conductor and magneto-dynamics in thin ferromagnetic structures can be applied for improving speed, clock frequency, power dissipation etc in r-f integrated circuits, microprocessor applications etc, and are fully compatible with CMOS technology.
Department or Program
Ph.D. in Engineering
Year Degree Awarded
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