Summer Research Experience for Undergraduates
2016 Summer REU Student Information & Research Abstracts
Name: Ryan Bailey-Crandell Undergraduate Institution: Oregon State University Major: Physics REU Advisor: Roland Kawakami Project Title: Characterizing charge and spin transport in graphene: From instrumentation to measurement Abstract: Spintronics aims to se the spin degree of freedom of electrons for logic operation and information storage. Recently, it has been proposed that high speed, low power consumption logic operations, as well as reconfigurable logic devices can be achieved with spintronics. To achieve the goals, it is required to develop a device that can reliably generate, transport, and detect spin. Graphene, a single atomic layer of graphite carbon atoms, is one of the most promising materials for spintronic devices. Graphene has shown promising qualifications for spin transport due to its gate-tunable electronic properties, long spin lifetime and spin diffusion length at room temperature. However, the lack of spin orbit coupling makes it hard to generate and detect spin within graphene, which is a hindrance for certain avenues of application. To achieve spin logic with graphene, it is necessary to develop a method to overcome this issue. We focus on generating spin orbit coupling in graphene, as this would allow control of spin signals in a graphene transport. Name: Forrest Elliot
One of the topics examined this summer was quantum spin liquids. In low temperature systems, there are two competing effects that influence magnetic order: classical ordering and quantum fluctuations. In antiferromagnetic materials, this “battle” between quantum and classical effects is usually won by antiferromagnetic interactions, resulting in a Néel ordered state at low temperatures. However, in certain materials, the quantum paramagnetic phase persists all the way to zero temperature, forming an exotic state of matter called a quantum spin liquid (QSL).Electronic structure of in-plane functionalized graphane analog interface Abstract: As research on 2D materials and functionalization of 2D crystals continues, we focus on the effects full functionalization of -H and -CH3 ligands have on a buckled germanene backbone. The crystal structures of hydrogen-terminated germanene and methyl-terminated germanene are simulated using crystal modeling software to observe the properties of both materials and determine whether forming a junction in an interface is practical. The work function and density of states of each 2D structure are analyzed to confirm if the ligands can work well in an interface. By simulating the crystal structure of 2D graphane analog interface and performing electronic calculations using Density Functional Theory methods, we can understand more about ligand chemistry on interfaces. Computational modeling of the structures provides novel insights into the properties and electronic structures of the materials. Successful theoretical results yield for potential synthesis of the materials to be used in the future for devices. Name: Erin Snyder Undergraduate Institution: Rollins College Major: Chemistry REU Advisor: Joshua Goldberger Project Title: Materials with anisotropic Seebeck behavior for transverse thermoelectrics Abstract: Alternative energy sources are becoming more desirable to replace other sources that have significant environmental effects or lose a large fraction of the generated energy as waste heat. One solution to this problem is a thermoelectric device, which creates a current from a change in voltage produced by a heat gradient. Typical thermoelectric devices require two separate materials containing different majority carrier types, both p-type and n-type. This allows holes and electrons to travel from the hot end to the cold end, respectively, thereby creating a difference in electrical potential. If one material were able to possess both p-type and n-type behavior in perpendicular axes, as seen through an anisotropic Seebeck coefficient, these devices would offer more practical device engineering as well as geometric adaptability. Several possible candidates were identified by their band structure indicating both p-type and n-type character, including CaAgBi, CaAgSb, CaCuBi, and CaCuSb, and formed using inorganic chemistry crystal synthesis. Phase-pure samples were synthesized by reacting stoichiometric amounts at high temperatures followed by slow cooling and were characterized by X-Ray Diffraction and Raman Spectroscopy. The next step towards transverse thermoelectric devices is creating large, single crystals to find axis dependence in Seebeck coefficients.