研究目的
To fabricate and characterize metal-insulator-metal (MIM) diodes on flexible substrates for RF and microwave circuit applications, investigating diodes with TiO2 and NiO insulators using different oxidation techniques and asymmetric metal contacts to achieve nonlinear I-V characteristics and high-frequency performance.
研究成果
MIM diodes on flexible substrates demonstrate strong nonlinearity, high current densities, and good RF performance. NiO-based diodes outperform TiO2-based ones due to thinner oxide and lower dielectric constant, showing higher rectification sensitivity and frequency multiplication range. The results indicate that MIM diodes are a viable non-semiconductor solution for flexible microwave circuits, with potential for further scaling to millimeter-wave frequencies.
研究不足
The study is limited to specific dielectric materials (TiO2 and NiO) and metal contacts on flexible PEEK substrates. Challenges include achieving uniform oxide layers and minimizing parasitic resistances. Optimization could involve exploring other dielectrics or metals, improving oxidation techniques, and scaling diode areas for higher frequency applications.
1：Experimental Design and Method Selection:
The study involves designing MIM diodes with asymmetric metal contacts (Ti-TiO2-Pd and Ni-NiO-Mo) on flexible PEEK substrates. Theoretical models include Simmons' equation for tunneling current and equivalent small signal models for high-frequency analysis. Methods include in-situ oxidation for TiO2 and plasma oxidation for NiO.
2：Sample Selection and Data Sources:
Diodes are fabricated with different areas (e.g., 48 μm2 and 9 μm2) on Polyether Ether Ketone (PEEK) substrates. Data is acquired through electrical measurements (J-V characteristics) and RF measurements (S-parameters, rectification, harmonic generation).
3：List of Experimental Equipment and Materials:
Equipment includes e-beam evaporator, reactive ion etching (RIE) chamber, Agilent N5227A Network Analyzer, spectrum analyzer, nano-voltmeter, directional coupler, RF probes. Materials include Ti, Pd, Ni, Mo, TiO2, NiO, PEEK substrate, photoresist, acetone, isopropanol, DI-water, FeCl3 etchant.
4：Experimental Procedures and Operational Workflow:
Substrate cleaning, metal deposition via e-beam evaporation and sputtering, oxidation processes (in-situ for TiO2, plasma for NiO), lithography for patterning, lift-off processes, electrical and RF measurements using probes and analyzers.
5：Data Analysis Methods:
Data analysis involves curve-fitting J-V data to Simmons' equation to extract barrier parameters, fitting S-parameters to equivalent models to derive component values, and calculating rectification sensitivity and harmonic output power.
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