Bulletin of the American Physical Society
Joint Spring 2013 Meeting of the Texas Sections of the APS and AAPT and Zone 13 of the SPS
Volume 58, Number 3
Thursday–Saturday, April 4–6, 2013; Stephenville, Texas
Session N3: Solid State Physics II |
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Chair: Daniel Vrinceanu, Texas Southern University Room: Nursing Building 108 |
Saturday, April 6, 2013 10:30AM - 10:42AM |
N3.00001: Engineering the band gap of $\alpha $-Fe$_{2}$O$_{3}$ by isovalent surfur doping Qiming Zhang, Congxin Xia Hematite $\alpha $-Fe$_{2}$O$_{3}$ is one of the potential materials for solar energy conversion due to its nontoxic, abundant, low-cost and environment-friendly characters. But its indirect band gap of the value of $\sim$2.1 eV causes the low efficiency in the optical absorption and hence the solar energy conversion. We study the isovalent substitutional doping of sulfur on oxygen sites in $\alpha $-Fe$_{2}$O$_{3}$ by means of the first-principles calculations based on DFT. Our results show that the band gap of $\alpha $-Fe$_{2}$O$_{3-x}$S$_{x}$ decreases monotonically with increasing the sulfur concentration $x$, resulting in an obvious increase of the optical absorption edge in the visible range. Most intriguingly, unlike the pure $\alpha $-Fe$_{2}$O$_{3}$ material, the $\alpha $-Fe$_{2}$O$_{3-x}$S$_{x}$ with $x\approx $0.17 exhibits a direct band gap of an ideal value ($\sim$ 1.45 eV), together with high optical absorption ($\sim$ 10$^{5}$ cm$^{-1}$) and lower carriers effective masses. These results indicate that $\alpha $-Fe$_{2}$O$_{3-x}$S$_{x}$, with a proper concentration of sulfur, may serve as a promising candidate for low-cost solar-cell materials. [Preview Abstract] |
Saturday, April 6, 2013 10:42AM - 10:54AM |
N3.00002: Using Resonant Microwave Cavities for Material Properties James Roberts, Jai Dahiya, S Ghosh The resonant microwave cavity is a very sensitive device operating very much like a high Q parallel RLC resonant network. In this paper we discuss some of the results obtained on plasmas, phase change in liquids and in gas-substrate interactions using microwave cavities. Results on the nature of the hydrogen bond will be discussed in the light of phase transition studies made on hydrogen and deuterium during phase transition from liquid to solid and solid to liquid. The macroscopic quantities frequency shift and width change at half-power-maxima of the resonance profile will be related to the microscopic quantities real and imaginary dielectric response of the material loading the resonant cavity. Slater's perturbation equations for perturbed resonant cavities will be used for analysis of the data. The apparatus used in this investigation is briefly discussed. [Preview Abstract] |
Saturday, April 6, 2013 10:54AM - 11:06AM |
N3.00003: New Sensitivity Regimes in Nuclear Magnetic Resonance Daniel Tennant, Isaac Manzanera, Jeremy Paster, John Markert Conventional NMR experiments using inductive techniques require a sample size of approximately 10$^{\mathrm{12}}$ nuclear spins. This limitation can be overcome by utilizing cantilevers, traditionally used for Atomic Force Microscopy, as the measuring tool. This technique has the potential to image individual nuclear spins and has already shown itself to be successful in capturing single electron spins. In this talk, I will outline the details of this procedure, present preliminary data from a trial sample of Ammonia Sulfate, and discuss future experiments. [Preview Abstract] |
Saturday, April 6, 2013 11:06AM - 11:18AM |
N3.00004: Experimental search for Bremsstrahlung radiation predicted by the hole theory of superconductivity Hamilton Carter The theory of hole superconductivity modifies BCS theory to propose that the paired charge carriers are ``undressed'' holes instead of electrons. As a consequence of this modification, the theory further states that electrons are expelled from the interior of the superconductor and exist as an excess charge density contained within the London penetration depth at the surface of the material. The theory predicts several experimentally testable consequences. Of these, arguably the most interesting, and the most easily tested prediction is the emission of Bremsstrahlung radiation by the expelled electrons as they redistribute in the superconductor when the superconducting state is quenched. An experimental design to detect the predicted ionizing radiation will be presented. The experiment will utilize a Pb sample cooled to its superconducting state in a liquid helium cryostat. The sample will be quenched using a superconducting magnet contained in the same cryostat. A NaI(Tl) scintillator will be used as the radiation detector. The maximum energy of the Bremsstrahlung spectrum predicted by the theory is 308.22 keV using a Pb sample with a radius of 3.8 cm. [Preview Abstract] |
Saturday, April 6, 2013 11:18AM - 11:30AM |
N3.00005: DNA in Nanoscale Electronics Jason Slinker, Chris Wohlgamuth, Marc McWilliams, Alon Gorodetsky DNA, the quintessential molecule of life, possesses a number of attractive properties for use in nanoscale circuits. Charge transport (CT) through DNA itself is of both fundamental and practical interest. Fundamentally, DNA has a unique configuration of $\pi $-stacked bases in a well ordered, double helical structure. Given its unparalleled importance to life processes and its arrangement of conjugated subunits, DNA has been a compelling target of conductivity studies. In addition, further understanding of DNA CT will elucidate the biological implications of this process and advance its use in sensing technologies. We have investigated the fundamentals of DNA CT by measuring the electrochemistry of DNA monolayers under biologically-relevant conditions. We have uncovered both fundamental kinetic parameters to distinguish between competing models of operation as well as the practical implications of DNA CT for sensing. Furthermore, we are leveraging our studies of DNA conductivity for the manufacture of nanoscale circuits. We are investigating the electrical properties and self-assembly of DNA nanowires containing artificial base pair surrogates, which can be prepared through low cost and high throughput automated DNA synthesis. This unique and economically viable approach will establish a new paradigm for the scalable manufacture of nanoscale semiconductor devices. [Preview Abstract] |
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