Physics

Low energy electron diffraction shows a (√3×√3)R30° reconstruction on O-polar ZnO surfaces after a tube furnace annealing process commonly used to create atomic-height steps. This reconstruction is also produced in situ under conditions having an extremely low hydrogen background. X-ray photoelectron spectroscopy suggests H stabilizes the (1×1) termination that has been extensively reported. The (√3×√3)R30° reconstruction is stable against H2,

Low energy electron diffraction shows a (√3×√3)R30° reconstruction on O-polar ZnO surfaces after a tube furnace annealing process commonly used to create atomic-height steps. This reconstruction is also produced in situ under conditions having an extremely low hydrogen background. X-ray photoelectron spectroscopy suggests H stabilizes the (1×1) termination that has been extensively reported. The (√3×√3)R30° reconstruction is stable against H2,

Zinc oxide (ZnO) is a semiconductor material exhibiting a wide bandgap in the ultraviolet (UV) region. ZnO is a promising material for use in short-wave optoelectronic devices such as all-optical switches (AOSs). Our switch is composed of a polycrystalline ZnO thin film grown by DC sputter deposition and uses a 120ps control pulse tuned to the band edge of the film to modify the transmission of a weaker signal pulse. The signal light is heavily absorbed in the absence of the control pulse, representing an off state of the switch. The control pulse, when incident on the film, resonantly excites electrons to create excitons. This decreases the material’s absorption by filling energy states and screening the built-in electric field of the ZnO. Consequently, more signal light is transmitted by the film, representing an on state.

We report amorphous rubrene thin film transistors with a polystyrene intermediate layer on the SiO 2 gate dielectric that have hole mobilities up to 0.01 cm 2 / V s. This improvement by two orders of magnitude over devices formed on SiO 2 alone occurs without the crystallization of rubrene. The enhanced charge transport is a result of the more planar growth and subsequent better geometrical connection of the first molecular layers of rubrene. Ambipolar conduction in the rubrene suggests that polystyrene minimizes the concentration of interfacial electron trap states.

Submitted for the MAR14 Meeting of The American Physical Society Spray Pyrolysis of Non-stoichiometric Zinc Tungstate Thin Films1 SETH KING, BRANDON ZINK, ETHAN DINAUER, JOSEPH KRUEGER, University of Wisconsin La Crosse, UNIVERSITY OF WISCONSIN LA CROSSE TEAM — Zinc tungstate (ZnWO4) has recently shown promise as a photon harvesting material for possible applications in photovoltaic and photocatalytic devices. While substantial work has focused on understanding the properties of stoichiometric ZnWO4, little work has investigated the non-stoichiometric material where the Zn to W ratio is varied from ideal. In the present study, we report on the fabrication of non-stoichiometric zinc tungstate thin films by spray pyrolysis. Results suggest that this technique may be utilized to deposit material with any desired Zn to W ratio. Therefore, the structural, electrical, and optical properties of non-stoichiometric zinc tungstate materials may be characterized and engineered for specific app...

We report a study of the Mn local structure, magnetism, and Ga moments in molecular beam epitaxy grown Mn-doped GaN films. Using x-ray absorption spectroscopy and magnetic circular dichroism, we find two distinct Mn sites and a Ga moment antiparallel to Mn. First-principles calculations reproduce this phenomenology and indicate that Mn preferentially populates Ga sites neighboring N split interstitial defects. These results show that defects may strongly affect the Mn ordering and magnetism, and that the GaN valence band is polarized, providing a long-range ferromagnetic ordering mechanism for Ga 1ÿx Mn x N.

A technique that combines the high speed and the high security of optical encryption with the advantages of electronic transmission, storage, and decryption is introduced. Digital phase-shifting interferometry is used for efficient recording of phase and amplitude information with an intensity recording device. The encryption is performed by use of two random phase codes, one in the object plane and another in the Fresnel domain, providing high security in the encrypted image and a key with many degrees of freedom. We describe how our technique can be adapted to encrypt either the Fraunhofer or the Fresnel diffraction pattern of the input. Electronic decryption can be performed with a one-step fast Fourier transform reconstruction procedure. Experimental results for both systems including a lensless setup are shown.

Disk harmonics are defined, and an explanation is given as to why they can be interpreted as the natural generalization of the Fourier basis set onto the unit disk. An existing statistical theory is used to show that a particular set of disk-harmonic coefficients is more suitable for describing images on the unit disk than Zernike or pseudo-Zernike moments are. Zernike moments have been applied to a wide range of problems. However, we concentrate on the problem of invariant pattern recognition and briefly indicate other problems where disk-harmonic coefficients are possibly useful. The effects that different pixel resolutions and discrete white noise have on the three moment or coefficient sets compared in this paper are briefly investigated experimentally.

Disk harmonics are defined, and an explanation is given as to why they can be interpreted as the natural generalization of the Fourier basis set onto the unit disk. An existing statistical theory is used to show that a particular set of disk-harmonic coefficients is more suitable for describing images on the unit disk than Zernike or pseudo-Zernike moments are. Zernike moments have been applied to a wide range of problems. However, we concentrate on the problem of invariant pattern recognition and briefly indicate other problems where disk-harmonic coefficients are possibly useful. The effects that different pixel resolutions and discrete white noise have on the three moment or coefficient sets compared in this paper are briefly investigated experimentally.

A novel photon-based proton model is developed. A proton's ground state is assumed to be coherent to the degree that all of its mass-energy precipitates into a single uncharged spherical structure. A quantum vortex, initiated by the strong nuclear force, but sustained in the proton's ground state by the circular Unruh effect and a spherical Rindler horizon, is proposed to confine the proton's massenergy in its ground state. A direct connection between the circular Unruh effect, the zitterbewegung effect, spin, and general relativity is proposed. Such a structure acts as an uncharged zitterbewegung fermion, and may explain neutrino mass. A ground-state proton's central zitterbewegung fermion is assumed to be surrounded by a halo of charge shells of both signs. Virtual photon standing waves are assumed to synchronize the inner shell with the central zitterbewegung fermion. The charge shells are proposed to be associated with isospin and proton g-factor. There are only two model inputs-proton mass and quantized electronic charge-and just one adjustable parameter. The adjustable parameter, reduced only by about 0.4% from an initial estimate, provides the proton's experimentally determined magnetic moment to arbitrary precision. The resulting modeled proton charge radius agrees very well with the 2018 CODATA value. Magnetic moment and charge radius are calculated algebraically in a manner easily understood by undergraduate physics students. This proposed ground-state proton model could be falsified by future experimental proton charge radius estimates, and could be considered a low-energy approximation to a full quantum chromodynamical proton model.

Disk harmonics are defined, and an explanation is given as to why they can be interpreted as the natural generalization of the Fourier basis set onto the unit disk. An existing statistical theory is used to show that a particular set of disk-harmonic coefficients is more suitable for describing images on the unit disk than Zernike or pseudo-Zernike moments are. Zernike moments have been applied to a wide range of problems. However, we concentrate on the problem of invariant pattern recognition and briefly indicate other problems where disk-harmonic coefficients are possibly useful. The effects that different pixel resolutions and discrete white noise have on the three moment or coefficient sets compared in this paper are briefly investigated experimentally.

A novel photon-based proton model is developed. A proton's ground state is assumed to be coherent to the degree that all of its mass-energy precipitates into a single uncharged spherical structure. A quantum vortex, initiated by the strong force, but sustained in the proton's ground state by the circular Unruh effect and a spherical Rindler horizon, is proposed to confine the proton's mass-energy in its ground state. A direct connection between the circular Unruh effect, the zitterbewegung effect, spin, and general relativity is proposed. Such a structure acts as an uncharged zitterbewegung fermion, and may explain neutrino mass. A ground-state proton's central zitterbewegung fermion is assumed to be surrounded by a halo of charge shells of both signs. Virtual photon standing waves are assumed to synchronize the inner shell with the central zitterbewegung fermion. The charge shells are proposed to be associated with isospin and proton g-factor. There are only two model inputsproton mass and quantized electronic charge-and just one adjustable parameter. The adjustable parameter, reduced only by about 0.4% from an initial estimate, provides the proton's experimentally determined magnetic moment to arbitrary precision. The resulting modeled proton charge radius agrees very well with the 2018 CODATA value. Magnetic moment and charge radius are calculated algebraically in a manner easily understood by undergraduate physics students. This proposed ground-state proton model could be considered a low-energy approximation to a full quantum chromodynamical proton model.