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Journal of Applied Physics

Jedidiah J McCoy, Santosh K Swain, John R Sieber, David R Diercks, Brian P Gorman, Kelvin G Lynn
Cadmium telluride (CdTe) high purity, bulk, crystal ingots doped with phosphorus were grown by the vertical Bridgman melt growth technique to understand and improve dopant solubility and activation. Large net carrier densities have been reproducibly obtained from as-grown ingots, indicating successful incorporation of dopants into the lattice. However, net carrier density values are orders of magnitude lower than the solubility of P in CdTe as reported in literature, 1018 /cm3 to 1019 /cm3 [J. H. Greenberg, J...
April 2018: Journal of Applied Physics
N S Susan Mousavi, Sunil Kumar
A structural model to predict in-field thermal conductivity of ferrofluids is proposed in this study and is validated by the experimental data from the literature. The model is able to capture the aggregation development of the magnetic particles with increasing magnetic field strength. Introducing a compression function that can be found empirically, the model can accurately predict the thermal conductivity, especially the plateauing at low and high magnetic fields.
January 28, 2018: Journal of Applied Physics
Stephen M Durbin, Tharun Nagulu, Anthony D DiChiara
Absorption of hard x-rays in GaAs creates excitations that can dramatically alter the propagation of optical laser pulses with photon energies near the bandgap. Measurements of optical transmission through a thin crystalline wafer of GaAs after absorption of an intense x-ray synchrotron pulse demonstrate how x-ray induced optical transparency depends on the recombination of excited conduction band electrons and valence band holes via Auger, spontaneous emission, and especially stimulated emission processes...
December 28, 2017: Journal of Applied Physics
Cecile S Bonifacio, Gautom Das, Ian M Kennedy, Klaus van Benthem
The reduction reactions and densification of nanochains assembled from γ -Fe2 O3 nanoparticles were investigated using in situ transmission electron microscopy (TEM). Morphological changes and reduction of the metal oxide nanochains were observed during in situ TEM annealing through simultaneous imaging and quantitative analysis of the near-edge fine structures of Fe L2,3 absorption edges acquired by spatially resolved electron energy loss spectroscopy. A change in the oxidation states during annealing of the iron oxide nanochains was observed with phase transformations due to continuous reduction from Fe2 O3 over Fe3 O4 , FeO to metallic Fe...
December 21, 2017: Journal of Applied Physics
Christopher E Sunday, Dmitry Veksler, Kin C Cheung, Yaw S Obeng
Traditional metrology has been unable to adequately address the needs of the emerging integrated circuits (ICs) at the nano scale; thus, new metrology and techniques are needed. For example, the reliability challenges in fabrication need to be well understood and controlled to facilitate mass production of through-substrate-via (TSV) enabled three-dimensional integrated circuits (3D-ICs). This requires new approaches to the metrology. In this paper, we use the microwave propagation characteristics to study the reliability issues that precede the physical damage caused by electromigration in the Cu-filled TSVs...
November 7, 2017: Journal of Applied Physics
Z S Barcikowski, J M Pomeroy
Metal-insulator-metal (MIM) tunnel junctions with the aluminum oxide tunnel barriers confined between cobalt electrodes exhibit less resistance drift over time than junctions that utilize a thick, unconfined aluminum electrode. The improved long time stability is attributed to better initial oxide quality achieved through confinement (use of a potential energy well for the oxygen) and plasma oxidation. In this work, Co/AlOx/Co and Co/Al/AlOx/Co tunnel junction aging is compared over a period of approximately 9 months using transport measurements and Wentzel-Kramers-Brillouin (WKB) based modelling...
November 2017: Journal of Applied Physics
C Flower, M S Freeman, M Plue, B Driehuys
High-volume production of hyperpolarized (129)Xe by spin-exchange optical pumping (SEOP) has historically fallen short of theoretical predictions. Recently, this shortfall was proposed to be caused by the formation of alkali metal clusters during optical pumping. However, this hypothesis has yet to be verified experimentally. Here, we seek to detect the presence of alkali particles using a combination of both transmission (TEM) and scanning (SEM) electron microscopy. From TEM studies, we observe the presence of particles exhibiting sizes ranging from approximately 0...
July 14, 2017: Journal of Applied Physics
V Mikhelashvili, G Ankonina, Y Kauffmann, G Atiya, W D Kaplan, R Padmanabhan, G Eisenstein
This paper describes a metal-insulator-semiconductor (MIS) capacitor with flat capacitance voltage characteristics and a small quadratic voltage capacitance coefficient. The device characteristics resemble a metal-insulator-metal diode except that here the capacitance depends on illumination and exhibits a strong frequency dispersion. The device incorporates Fe nanoparticles (NPs), mixed with SrF2, which are embedded in an insulator stack of SiO2 and HfO2. Positively charged Fe ions induce dipole type traps with an electronic polarization that is enhanced by photogenerated carriers injected from the substrate and/or by inter nanoparticle exchange of carriers...
June 7, 2017: Journal of Applied Physics
C McKeever, F Y Ogrin, M M Aziz
The high frequency dynamic behaviour of concentric permalloy nanorings with vortex domain structures with a thickness of 20 nm, a width in the range of 100 nm-250 nm, and a separation in the range of 10 nm-600 nm is investigated by micromagnetic simulations. The aim is to explore the ferromagnetic resonance of the concentric ring structure as a function of geometric parameters of the system. The dynamic susceptibility spectrum and spatial localization of the ferromagnetic resonance mode are investigated for varying ring widths and separations...
May 28, 2017: Journal of Applied Physics
J Gruber, X W Zhou, R E Jones, S R Lee, G J Tucker
We investigate the formation of extended defects during molecular-dynamics (MD) simulations of GaN and InGaN growth on (0001) and ([Formula: see text]) wurtzite-GaN surfaces. The simulated growths are conducted on an atypically large scale by sequentially injecting nearly a million individual vapor-phase atoms towards a fixed GaN surface; we apply time-and-position-dependent boundary constraints that vary the ensemble treatments of the vapor-phase, the near-surface solid-phase, and the bulk-like regions of the growing layer...
May 21, 2017: Journal of Applied Physics
Zhaojiang Chen, Shiyang Li, Yang Zhang, Wenwu Cao
Bipolar electric field induced degradation in [001]c poled Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-0.29PT) single crystals was investigated at megahertz frequencies. The electromechanical coupling factor kt , dielectric constant εr , dielectric loss D, and piezoelectric constant d33 were measured as a function of amplitude, frequency, and number of cycles of the applied electric field. Our results showed that samples degrade rapidly when the field amplitude is larger than a critical value due to the onset of domain switching...
May 7, 2017: Journal of Applied Physics
Dorian Ziss, Javier Martín-Sánchez, Thomas Lettner, Alma Halilovic, Giovanna Trevisi, Rinaldo Trotta, Armando Rastelli, Julian Stangl
In this paper, strain transfer efficiencies from a single crystalline piezoelectric lead magnesium niobate-lead titanate substrate to a GaAs semiconductor membrane bonded on top are investigated using state-of-the-art x-ray diffraction (XRD) techniques and finite-element-method (FEM) simulations. Two different bonding techniques are studied, namely, gold-thermo-compression and polymer-based SU8 bonding. Our results show a much higher strain-transfer for the "soft" SU8 bonding in comparison to the "hard" bonding via gold-thermo-compression...
April 2017: Journal of Applied Physics
Alborz Amirsadeghi, Lance Brumfield, Junseo Choi, Emily Brown, Jae Jong Lee, Sunggook Park
Hydrophobic silane coatings have been successfully applied to the surface of Si stamps to improve demolding in nanoimprint lithography (NIL). However, the role of the silane coating has only been studied either indirectly, by measuring adhesion or friction coefficients for Si and substrate surfaces without patterns, or collectively, by measuring the overall demolding force that does not differentiate contributions of friction dissipation, stored elastic energy, and adhesion. Here, for the first time, we present experimental evidence on the role of the silane coating in improving demolding in UV-NIL by using different silane coatings...
January 28, 2017: Journal of Applied Physics
Benoit Gaury, Paul M Haney
Analytic expressions are presented for the dark current-voltage relation J ( V ) of a pn + junction with positively charged columnar grain boundaries with high defect density. These expressions apply to non-depleted grains with sufficiently high bulk hole mobilities. The accuracy of the formulas is verified by direct comparison to numerical simulations. Numerical simulations further show that the dark J ( V ) can be used to determine the open-circuit potential V oc of an illuminated junction for a given short-circuit current density J sc ...
December 21, 2016: Journal of Applied Physics
Jeong Hoon Ryou, Jason J Gorman
An analytical comparison between the fundamental mode and higher modes of vibration for an electrostatic beam resonator is presented. Multiple mode numbers can be matched to a desired resonance frequency through appropriate scaling. Therefore, it is important to determine which mode yields the best performance. A dynamic model of the resonator is derived and then used to determine the motional resistance for each mode. The resulting equation provides the basis for comparing performance between modes using motional resistance and quality factor...
December 7, 2016: Journal of Applied Physics
John F Roller, Yu-Tai Li, Mario Dagenais, Behrang H Hamadani
Charge carrier lifetimes in photovoltaic-grade silicon wafers were measured by a spectral-dependent, quasi-steady-state photoconductance technique. Narrow bandwidth light emitting diodes (LEDs) were used to excite excess charge carriers within the material, and the effective lifetimes of these carriers were measured as a function of wavelength and intensity. The dependence of the effective lifetime on the excitation wavelength was then analyzed within the context of an analytical model relating effective lifetime to the bulk lifetime and surface recombination velocity of the material...
December 2016: Journal of Applied Physics
B P Burton, A K Singh
A first principles phase diagram calculation, that included van der Waals interactions, was performed for the 3D bulk system (1 - X ) · MoS 2 - ( X ) · MoTe 2 . Surprisingly, the predicted phase diagram has at least two ordered phases, at X ≈ 0:46, even though all calculated formation energies are positive; in a ground-state analysis that examined all configurations with 16 or fewer anion sites. The lower-temperature I -phase is predicted to transform to a higher-temperature I' -phase at T ≈ 500 K, and I' disorders at T ≈ 730 K...
October 2016: Journal of Applied Physics
Paul M Haney, Heayoung P Yoon, Benoit Gaury, Nikolai B Zhitenev
Electron beam induced current (EBIC) is a powerful characterization technique which offers the high spatial resolution needed to study polycrystalline solar cells. Current models of EBIC assume that excitations in the p - n junction depletion region result in perfect charge collection efficiency. However we find that in CdTe and Si samples prepared by focused ion beam (FIB) milling, there is a reduced and nonuniform EBIC lineshape for excitations in the depletion region. Motivated by this, we present a model of the EBIC response for excitations in the depletion region which includes the effects of surface recombination from both charge-neutral and charged surfaces...
September 7, 2016: Journal of Applied Physics
N M Bruno, Y J Huang, C L Dennis, J G Li, R D Shull, J H Ross, Y I Chumlyakov, I Karaman
The influence of grain constraint on the magnetic field levels required to complete the isothermal martensitic transformation in magnetic shape memory alloys has been demonstrated for a NiCoMnSn alloy, and the magnetocaloric performance of an optimally heat treated alloy was quantified. Ni45 Cox Mn45-x Sn10 melt spun ribbons with x = 2, 4, 5, and 6 were characterized. The x = 5 sample was determined to exhibit the lowest transformation thermal hysteresis (7 K) and transformation temperature range during transformation from paramagnetic austenite to nonmagnetic martensite, as well as a large latent heat of transformation (45 J kg-1 K-1 )...
August 2016: Journal of Applied Physics
Angela N Fioretti, Craig P Schwartz, John Vinson, Dennis Nordlund, David Prendergast, Adele C Tamboli, Christopher M Caskey, Filip Tuomisto, Florence Linez, Steven T Christensen, Eric S Toberer, Stephan Lany, Andriy Zakutayev
Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3 N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3 N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3 N thin films...
May 14, 2016: Journal of Applied Physics
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