Deterministic assembly of functional nanodevices onto silicon circuit

Bottom-up integration of nanostructures offers a promising method to achieve material diversity for chemical and biological applications, often considered unattainable by conventional top-down fabrication. Thus, deterministic integration of nanostructures such as nanowires and nanoshell spheres on silicon CMOS circuitry represents a significant step toward cross-reactive silicon CMOS chip where different types of off-chip synthesized sensory materials are merged. Applying this deterministic bottom-up integration to substrate or circuit eliminates the constraints of thermal budget, chemical compatibility, lattice mismatch between nanostructures to be assembled and substrate. This thesis discusses a deterministic assembly strategy for nanowires and spheres and their integrations onto silicon CMOS circuitry for electronic microsystem applications.;The nanowire assembly structure was designed to create a dielectrophoretic attractive force toward the electrode gap, resulting in uniformly-spaced rhodium nanowire array due to mutual electrostatic interaction between assembled nanowires. Systematic investigation reagarding nanowire array formation reveals that stronger long-range dielectrophoretic forces attract more nanowires at the electrode gap, forming less-spaced array while stronger electrostatic nanowire interaction results in the larger spacing within the array. Thus, their interplay tends to determine the average spacing between the assembled nanowires.;Based on understanding the electrostatistic interaction between assembled nanowires, lithographically defined wells with a localized electric field determines the final alignment position of assembled rhodium nanowires on a substrate. Post-assembly process using electrodeposition and subsequent lift-off process completes monolithic integration of rhodium nanowires while preserving nanowires assembled only within the recessed region. Individual rhodium nanowire assembly yields exceeding 95% were obtained at nanowire densities >105 /cm2 with a submicron registration accuracy. PEDOT/ClO4 nanowire chemical sensors are also fabricated to demonstrate functional nanowire integration for on-chip sensing.;This thesis also describes a bottom-up strategy for fabricating ultra-high-density cross-point sensor arrays (>107 elements/cm2) that uses fluidic assembly to position the functional nanoshell microspheres between lithographically-defined electrodes on-chip. Cross-point array structure is designed to accommodate single spherical particles at each cross-point and make them electrically connected to upper and lower access electrodes. As proof-of-concept, PEDOT nanoshell microspheres are assembled to fabricate chemical sensor devices for on-chip application. Individually addressing each PEDOT nanoshell sphere enables monitoring of an array of sphere for conductance change by chemical gas, solvent, humidity.;Due to upper and lower electrodes format and intrinsic form factor of spheres, it is advantageous to achieve high integration density compared to nanowires with a high aspect ratio. Additionally, this architectural framework combines the advantages of large surface-to-volume ratio particle-based sensor elements with high sensor redundancy to enhance performance metrics such as detection sensitivity and signal-to-noise ratio.