Todd Schumann

Graphite based Schottky diodes formed on Si, GaAs, and 4H-SiC substrates

We demonstrate the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon (Si), gallium arsenide (GaAs), or 4H-silicon carbide (4H-SiC). Near room temperature, the forward-bias diode characteristics are well described by thermionic emission, and the extracted barrier heights, which are confirmed by capacitance voltage measurements, roughly follow the Schottky–Mott relation. Since the outermost layer of the graphite electrode is a single graphene sheet, we expect that graphene/semiconductor barriers will manifest similar behavior.

Improved memristive switching of graphite/Nb:SrTiO 3 interfaces by tuning Fermi levels and dielectric constants

Layered electrodes based on graphene or transition metal dichalcogenides have enriched the development of nanoelectronics due to their uniqueness in flexibility, transparency, thermal stability, and electronic structure. Here, we report on resistive switching behavior observed in graphite/Nb:SrTiO 3 (Gr/NbSTO) junctions. Straightforward in situ bromine intercalation of graphite modulates the transport properties of Gr/NbSTO devices, an effect which cannot be achieved using traditional metal electrodes. At low temperatures, the strong electric field dependence of the dielectric constant of NbSTO also plays an important role in further enhancing the resistive switching performance. Our findings here suggest that to optimize the performance and to perform more complex functions, tunability of the Fermi level of the layered graphite electrode in combination with the nonlinear dielectric constant of the NbSTO substrate is critically important for interface-type resistive switching devices.Layered electrodes based on graphene or transition metal dichalcogenides have enriched the development of nanoelectronics due to their uniqueness in flexibility, transparency, thermal stability, and electronic structure. Here, we report on resistive switching behavior observed in graphite/Nb:SrTiO 3 (Gr/NbSTO) junctions. Straightforward in situ bromine intercalation of graphite modulates the transport properties of Gr/NbSTO devices, an effect which cannot be achieved using traditional metal electrodes. At low temperatures, the strong electric field dependence of the dielectric constant of NbSTO also plays an important role in further enhancing the resistive switching performance. Our findings here suggest that to optimize the performance and to perform more complex functions, tunability of the Fermi level of the layered graphite electrode in combination with the nonlinear dielectric constant of the NbSTO substrate is critically important for interface-type resistive switching devices.

Fabrication of high-aspect-ratio nanoporous high-k MTiO 3 (M= Ba, Sr, or Ba x Sr 1−x ) using anodization and hydrothermal processes

Fabrication of a nanoporous high-k material is demonstrated using anodization and hydrothermal processes. The fabrication process offers advantages of the formation of a high-aspect-ratio large surface area nanoporous structure, low temperature conformal surface conversion, and the creation of high dielectric constant perovskite ferroelectrics. The hydrothermal process is exploited to form various MTiO3 materials such as BaTiO3, SrTiO3, and BaxSr1−xTiO3 with different Ba and Sr ratios. The crystalline phase, morphology, and element composition of the nanostructured material are investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscope (EDX), to prove the formation of ordered polycrystalline MTiO3 arrays. The three dimensional high density capacitor would be realized by this fabrication method.

Glass interposer integrated millimeter wave antennas for inter-/intra chip communications

Millimeter wave antennas are integrated in the glass interposer layer for wireless inter-/intra chip/board communications. For in-plane communication, a disc loaded monopole antenna with an omni-directional radiation pattern is designed while for out-of plane communication, a similar architecture with patch mode radiation is configured. These antennas are useful for wireless interconnects in three dimensional integrated systems in package.