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 Assistant Professor B.S. 1997, Peking (Beijing) University, China Ph.D. 2002, Cornell University Room: 3363aPhone: 608-262-1562 Email: jin@chem.wisc.edu Position: Assistant Professor Selected Publications
| Research DescriptionResearch in the Jin group is centered on the chemistry and physics of nanoscale materials. We develop rational strategies for chemical synthesis, assembly and integration of nanomaterials, and investigate fundamental synthesis-structure-property relationships, especially through device fabrication and characterization. We apply vapor-phase, solution-phase and solid-state nanomaterials synthesis, as well as "traditional" inorganic synthesis of single source precursors. We are interested in nanomaterials for renewable energy conversion, such as photovoltaic and thermoelectric energy conversion, magnetic semiconducting nanomaterials for spintronics, and the applications of nanomaterials in biotechnology. Summarized below are our on-going research areas: Nanomaterials formation mechanism driven by screw dislocations. We have discovered a nanowire (NW) growth mechanism driven by axial screw dislocations that is fundamentally different from the traditional vapor-liquid-solid (VLS) or analogous mechanisms using metal catalysts. The self-perpetuating steps of a screw dislocation spiral provide the fast crystal growth front under low supersaturation during crystal growth (Fig. B) to enable the anisotropic crystal growth of one-dimensional (1-D) NWs. The fast growing NWs driven by dislocation, when combined with epitaxial overgrowth of NW branches formed via the slower VLS mechanism, result in unprecedented "Christmas tree" nanostructures of PbS (Fig. A). These fascinating trees with rotating branches are the clearest demonstration of "Eshelby twist" - the rotation of a crystal lattice around a screw dislocation as the consequence of its associated stress.Dislocation-driven NW growth is a general mechanism that has been greatly under appreciated. This discovery and our continuing study will create a new dimension in the rational design and synthesis of nanomaterials.
General chemical synthesis of metal silicide nanowires. Nanomaterials extensively studied so far are usually made of elements or prototypical compound semiconductors with simple stoichiometries. In contrast, intermetallic compounds such as metal silicides have multiple and unpredictable stoichiometries and complex phase behavior, making them challenging to synthesize and rarely explored so far. However, novel NW materials of silicides have significant applications in nanoelectronics, nanospintronics, and thermoelectrics. To overcome such previously unaddressed complexity, we developed general synthetic approaches to silicide NWs using chemical vapor deposition (CVD) of single source organometallic precursors (SSPs) and a complementary chemical vapor transport (CVT) method to reproducibly deliver both silicon and metals with stoichiometric control. We are systematically investigating families of SSPs and working on elucidating the detailed NW growth mechanism and the chemical rules governing the formation of the nanoscale intermetallic phases, towards the goal of rational synthesis of nanomaterials of any pure or alloyed metal silicides.
Nanomaterials for renewable energy applications. Nanomaterials will play important roles in increasing the performance of various renewable energy generation technologies, such as photovoltaics and thermoelectric energy generations. In order to realize highly efficient photovoltaic solar cells beyond the Shockley-Queisser limit, multi-exciton generating nanocrystals (quantum dots) and nanowires of PbSe and PbS and their nanoscale heterostructures are investigated in a collaboration project. We also study nanoscale semiconducting silicide materials for their enhanced thermoelectric conversion due to reduced dimensions. Unconventional synthetic pathways to bulk quantity nanostructured silicide and silicon materials are being developed to enable the practical applications of these nanomaterials in high performance thermoelectrics.
Nanoscale magnetic semiconductor materials for spintronics. Spintronics seeks to exploit electron spin properties instead of (or in addition to) charge degrees of freedom in solid-state electronic devices and promises to revolutionize computing. The realization of spintronic vision critically depends on the advances in magnetic semiconducting materials. We synthesized previously unavailable nanomaterials of concentrated magnetic semiconducting europium Bioinspired assembly of functional nanoscale materials. We apply the biomimetic principles derived from biomineralization processes to the assembly of nanoscale functional materials into nanoscale systems. In biomineralization, "matrix" macromolecules can efficiently induce nucleation of inorganic species into crystals at specific locations with controlled size, morphology, and growth orientation. By carefully controlling surface organic molecules, we demonstrated the nucleation and assembly of semiconductor arrays on flexible polymer substrates directly from solution and exploited them for large-area macroelectronic applications. Truly nanoscale bottom-up assembly is realized by using self-assembled nanostructured block copolymers and sequenced biopolymers, such as synthetic collagen and b-peptide nanofibers, as templates. Awards
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chalcogenides and Fe1-xCoxSi alloys and use them as model systems for fundamental studies and nanodevice implementations in spintronics. Particularly, we are exploiting the half-metallic Fe1-xCoxSi NWs we have synthesized and their nanoscale heterostructures with silicon to tackle the grand challenges of injecting and detecting polarized electrons in silicon to realize silicon-based spintronic devices.