III-nitride materials (GaN, AlN, InN and their alloys) are wide band-gap semiconductors with important applications in the fabrication of UV and blue emitters, detectors, high-speed field-effect transistors (FETs), and high-power/high-temperature devices. Future enhanced electronic and photonic devices will demand the utilization of low-dimensional structures. There are two different philosophies to produce functional semiconductor nanostructures. The top-down approaches rely on patterning techniques (lithography, nano-imprinting, or ion-beam) to literally sculpt thin films into nano-structures. Bottom-up synthesis techniques, however, make use of the natural self-assembly tendency of atoms and molecules to form the desired nanostructures. These techniques have a resolution control that is currently inaccessible to top-down approaches and offer an advantage for the monolithic integration of different materials since the nanostructures are not greatly affected by the lattice and thermal expansion mismatches with the substrate.
Intellectual Merit. Among the bottom-up techniques for producing nanostructures, chemical vapor deposition (CVD) techniques have been successfully utilized to synthesize multiple kinds of nanomaterials. The synthesis process using standard thermal CVD techniques is mainly controlled by the temperature and mass transport conditions at the substrate surface where the heterogeneous chemical reaction takes place. Controlling the arrangement, nucleation, and growth of the resulting low dimensional structures remain as major challenges associated with CVD nanofabrication strategies. This research will be concerned with the development of novel synthesis strategies for III-nitride nanostructures using UV-radiation assisted CVD. By means of localized, selective excitation of chemical species and substrate surfaces using UV photons, the possibility for direct-writing and morphological control of III-nitride nanostructures will be determined. The synthesis experiments will be carried out utilizing a tunable UV beam-light (3.5-9eV) generated at the Brookhaven National Laboratory (BNL) National Synchrotron Light Source (NSLS). The chemical and structural characterization of the produced nanostructures will be carried out using SEM, EDAX, and HRTEM at both Stony Brook University and the BNLs Center for Functional Nanomaterials. Optical characterization of the synthesized III-nitride nanostructures will be carried out in collaboration with scientist at the City University of New York.
Broader Impacts. Beyond the scientific objectives, the research will serve as a valuable program to introduce K-12, undergraduate, and graduate students to the technological importance of wide bandgap semiconductors and the need for developing novel synthesis technologies for nanomaterials. The envisioned research program will involve a Fulbright postdoctoral fellow, one graduate student, and four undergraduate students. Dissemination of the research results via outreach to K-12 students will be achieved by fostering visits of Long Island high school students to Stony Brook University. The PI will also strive to promote involvement of financially challenged and underrepresented students in the proposed research. This mission will be propelled through a close collaboration with Stony Brooks NSF-funded CSEMS and AGEP programs, and the local chapter of the Society for Hispanic Professional Engineers. The proposed research will enable access to research experiences for four underrepresented undergraduate students and be used to promote interest for engineering and science among high-school students from predominantly Hispanic Long Island communities. The outcome of this research could also have an important societal impact by generating seminal results for the development of direct-writing technologies to fabricate nanoscale functional devices in a cost-efficient manner by combining the capabilities of modern UV lithography with in situ UV-assisted CVD synthesis of semiconductor nanostructures for sensors, light emitters, and electronic transistors.
