Volume One (Birgit Krohn Albums)

The first of Birgit Krohn\u27s three albums containing printed and manuscrip] music, much of which was likely collected during her time at Nikka Vonen\u27s school for girls in Dale, Norway.https://scholarexchange.furman.edu/krohn-album1/1000/thumbnail.jp

Magnetotransport in Nanostructured Ni Films Electrodeposited on Si Substrate

The study of electrical resistivity  and magnetoresistance MR in nanogranular Ni films was performed over the temperature range 2 - 300 K and at the magnetic field induction B up to 8 T. The Ni layers having a thickness of about 500 nm were prepared by electrodeposition on n-Si wafers. According to an X-ray diffraction study, a strongly textured face-centered cubic structure was formed in the as-deposited films with an average grain sizes of about 10 - 70 nm. Experiments have demonstrated that the magnetic field and temperature dependences of the MR effect in Ni films shown two main peculiarities: (1) dependencies on the mutual orientations of vectors B, current and the film plane; (2) two contributions to the MR - negative anisotropic magnetoresistance and positive Lorentz-like MR

Gigantic Magnetoresistive Effect in n-SiSiO2Ni Nanostructures Fabricated by the Template-Assisted Electrochemical Deposition

The study of the carrier transport and magnetotransport in n-Si/SiO2/Ni nanostructures with granular Ni nanorods embedded into the pores in SiO2 was performed over the temperature range 2 – 300 K and at the magnetic field induction up to 8 T. In n-Si/SiO2/Ni nanostructures at temperatures of about 25 K a huge positive MR effect is observed. Possible mechanisms of the effect is discussed

Percolation phenomena in Cux(SiOy)100-x nanocomposite films produced by ion beam-sputtering

In this paper the results of examinations of nanocomposites Cux(SiOy)100x produced by ion beam sputtering using argon ions were presented. The examinations were performed by the use of ac devices for measuring frequency in the range 50 Hz - 1 MHz and temperatures from 81 K to 273 K. The measurements were performed for the samples directly after production. Based on temperature dependences of conductivity , which were determined at the frequency 100 Hz, the Arrhenius graphs were prepared. From these graphs conductivity activation energies E were calculated. Dependences of conductivity and activation energy of electrons on the metallic phase content x at the frequency 100 Hz were determined. Analysis of the obtained dependences shows that conductivity is a parabolic function of the metallic phase content x in nanocomposites. Changes of activation energies of nanocomposites, in which metallic phase contents are in the ranges x < 12 at.% and x > 68 at.%, demonstrate negative values and metallic type of conductivity. In the range 12 at:% < x < 68 at:% activation energies have positive values and the dielectric type of conductivity. It was established that for the metallic phase content of about 68 at.% the real percolation threshold occurs, and the conduction changes from dielectric to metallic type

Electrical Properties of the Layered Single Crystals TlGaSe2 and TlInS2

In the doped crystals TlGaSe2 and TlInS2, using method of temperature dependencies of DC resistance in the temperature range of 100 – 300 K, the phase transitions at the temperatures of 240 – 245 K and 105 – 120 K were observed. The AC conductance measurements at room temperature indicated the hopping mechanism of carrier transport in the studied samples

Low Temperature Conductivity in n

We investigate the transport properties of n-type noncompensated silicon below the insulator-metal transition by measuring the electrical and magnetoresistances as a function of temperature T for the interval 2–300 K. Experimental data are analyzed taking into account possible simple activation and hopping mechanisms of the conductivity in the presence of two impurity bands, the upper and lower Hubbard bands (UHB and LHB, resp.). We demonstrate that the charge transport develops with decreasing temperature from the band edge activation (110–300 K) to the simple activation with much less energy associated with the activation motion in the UHB (28–90 K). Then, the Mott-type variable range hopping (VRH) with spin dependent hops occurs (5–20 K). Finally, the VRH in the presence of the hard gap (HG) between LHB and UHB (2–4 K) takes place. We propose the empiric expression for the low T density of states which involves both the UHB and LHB and takes into account the crossover from the HG regime to the Mott-type VRH with increasing temperature. This allows us to fit the low T experimental data with high accuracy

Low temperature conductivity of silicon doped with antimony

A detailed analysis of the experimental temperature dependences of the resistivity of silicon doped with arsenic with a concentration of 10*18 cm–3 is performed for the region 1.8 K < T < 25 K. It is shown that, as a result of cooling to a temperature lower than 4.5 K, a transition from the Mott mode with variable hopping length to the mode of hopping conduction via nearest neighbors is observed, while, at T < 2.5 K, a transition to the Shklovskii–Efros mechanism is possible. A model for such a temperature crossover is suggested; the model is based on simplified solution of the percolation problem with the use of an interpolation expression for the density of states. Performed estimates show that the model is in satisfactory agreement with experimental data when the minimum number of adjustable parameters are used

Методика проектирования импульсных устройств фазовой синхронизации

The paper considers pulse phase-locked loops (PPLL) in which switching of structure and pa­rameters is used for improvement of dynamic and spectral characteristics Classification of existing switching algorithms is given in the paper. The paper proposes designing methodology that takes into account discrete and non-linear characteristics of the considered devices, and also requirements to synchronism, stability, speed, spectral characteristics, peculiarities of various switching algorithms. Practical approbation of the methodology has been carried out.В статье рассматриваются импульсные устройства фазовой синхронизации, в которых для улучшения динамических и спектральных характеристик используется переключение структуры и параметров. Приведена классификация существующих алгоритмов переключения. Предложена методика проектирования, учитывающая дискретные и нелинейные свойства рассматриваемых устройств, а также требования к синхронизму, устойчивости, быстродействию, спектральным характеристикам, особенности различных алгоритмов переключения. Произведена практическая апробация методики

Dielectric properties of nanocomposite (Cu)x(SiO2)(100-x) produced by ion-beam sputtering

It has been established that in the nanocomposite Cux(SiO2)(100 x) with the metallic phase content x = 27.27 at.% the following phenomena occur: hopping conductivity, additional polarity and coilless-like inductance. Coilless-like inductance phenomenon consists in the occurrence of positive values of phase shift in the high frequency area. Activation energy of the dielectric relaxation time for copper nanoparticles of unoxidized surface is of approx. 0.0003 eV, whereas surface oxidation causes a potential barrier occurrence and activation energy increase up to approx. 0.3360 eV. Comparative analysis of results obtained for the Cux(SiO2)(100 x) material and the measurements results obtained for the nanocomposites (FeCoZr)x(Al2O3)(100 x), (FeCoZr)x(CaF2)(100 x) and (FeCoZr)x(PZT)(100 x), which containing nanoparticles of ferromagnetic alloy, has been performed. It has shown that the type of magnetic properties of metallic phase, which is ferromagnetic ones for FeCoZr and diamagnetic ones for Cu, does not affect capacitive and inductive phenomena of the nanocomposites. The phenomena are related only to the nanogranular structure of the materials and the hopping mechanism of the charge transport between the metallic phase nanoparticles

Direct Patterning of Nitrogen-Doped CVD Graphene Based Microstructures for Charge Carrier Measurements Employing Femtosecond Laser Ablation

Chemical vapor deposited nitrogen-doped graphene, transferred on SiO2/Si substrate, was selectively patterned by femtosecond laser ablation for the formation of the topology dedicated to charge carrier measurements. Ultrashort 1030 nm wavelength Yb:KGW fs-laser pulses of 22 μJ energy,14 mJ cm−2 fluence, 96% pulse overlap, and a scanning speed of 100 mm s−1, were found to be the optimum regime for the high throughput microstructure ablation in graphene, without surface damage of the substrate in the employed fs-laser micromachining workstation. Optical scanning electron, atomic force microscopy, as well as Raman spectroscopy, were applied to clarify the intensive fs-laser light irradiation effects on graphene and the substrate, and to also verify the quality of the graphene removal. Measurements of magnetotransport properties of the fs-laser ablated nitrogen-doped graphene microstructure in the Hall configuration enabled the determination of the type, as well as concentration of charge carriers in a wide range of temperatures