The effects of post-deposition annealing conditions on structure and created defects in Zn0.90Co0.10O thin films deposited on Si(100) substrate

We analyze the effect of post-deposition annealing conditions on both the structure and the created defects in Zn0.90Co0.10O thin films deposited on the Si (100) substrates by RF magnetron sputtering technique using home-made targets. We concentrated on understanding the homogeneity of substituted Co+2 ions and the annealing effects on the amount of defects in the ZnO lattice. Orientations of thin films are found to be in the [0002] direction with a surface roughness changing from 67±2 nm to 25.8±0.6 nm by annealing. The Co+2 ion substitutions, changing from 7.5±0.3 % to 8.8±0.3 %, cause to form Zn–O–Co bonds instead of Zn–O–Zn and split the Co2p energy level to Co2p1/2 and Co2p3/2 with 15.67±0.06 eV energy difference. In addition, the defects in the lattice were revealed from the correlations between Zn–O–Co bonds and intensity of Raman peak at around 691 cm-1. Furthermore, the asymmetry changes of O1s peak positions in X-ray Photoelectron Spectra (XPS) were also found to be in accordance with the Raman results

Photocurrent analysis of AgIn5S8 crystal

The photocurrent (PC) spectrum of AgIn5S8 crystal consists of a single peak, which provides to determine the bandgap energy by applying the Moss rule. The temperature dependence of the bandgap energy was also calculated. The PC dramatically increased by pre-illumination with light having wavelength corresponding to the bandgap of AgIn5S8. The temperature-dependent PC of the sample was measured at different temperatures from 80 to 300 K and the PC spectrum consisted a single broad peak. Thermal quenching of the PC was observed to start at similar to 105 K and the PC completely quenched at similar to 180 K. The quenching mechanism was discussed in terms of the two-centre model. The height of the PC peak rised linearly with applied voltage up to 5.0 V under constant intensity of light. Similarly, the dark current-voltage characteristics consisted of a single region dominating an ohmic behaviour, and no space charge limited region was apparent at various temperatures up to 20 V

Morphometry of the Corpus Callosum

Corpus callosum (CC) is the largest fiber pathway linking the two cerebral hemispheres of the brain. These connections through the CC are either homotopic that connect the same or similar areas on each hemisphere or heterotopic that connect functionally similar, but anatomically different areas in two hemispheres. That means it plays an important role in integration and communication of hemispheres. As having morphological differences among people, being a structure that completes its myelinization later and because of its functional importance, it appeal to researchers. The aim of this review was to evaluate the functional anatomy of the CC. By the use of tractographies and functional MRIs, topographic organization of CC and the effect of neurodevelopmental and neurodegenerative processes may be well understood.</p

Characteristics of traps in AgIn5S8 single crystals

Characteristics of charge traps in AgIn5S8 single crystals are investigated by the use of Thermally Stimulated Current (TSC) technique. The TSC spectra of the unintentionally doped sample recorded at a constant heating rate from 80 K to 300 K reveals a single broad peak at similar to 90 K. The shift of the TSC peak continuously due to post-illumination preheating process confirmed the continuous trap distribution, which is Gaussian in shape. The trap density distribution changes from similar to 40 meV on the shallow side to similar to 120 meV on the deep side with the appearance of a maximum at similar to 72 meV

A comparative study of nanosized iron oxide particles; magnetite (Fe3O4), maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3), using ferromagnetic resonance

We investigated intra/inter particle interactions in single domain size magnetite (Fe3O4), maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3) iron oxide particles. The magnetic analyses were done using vibrating sample magnetometer and magnetic resonance measurements that were taken from 5 to 300 K and from 120 to 300 K, respectively. The magnetic resonance analyses were done for the iron oxides, frozen under 5000 G fields in glycerol matrix. By changing the temperature, a change in resonance field lines was observed at each Fe3O4, gamma-Fe2O3 and alpha-Fe2O3 nanoparticles. However, the fits in resonant lines showed that Lande g values (spectroscopic splitting factor) stayed stable with temperature decrease. The thermal sensitivities that were determined from Lande g factors, revealed three dominant interactions on resonant lines namely; the exchange coupling in between Fe2+, Fe3+ and O (g(1) = 3.01 +/- 0.08), Fe3+ centers (1.88 +/- 0.03 <= g(2) <= 2.02 +/- 0.03, depending on iron oxide states) and flip flop of O ions in between ionic states of Fe2+-O (1) and Fe3+-O (2) (2.35 +/- 0.06 <= g(3) <= 2.44 +/- 0.06, depending on iron oxide states)

A comparative study of nanosized iron oxide particles; magnetite (Fe3O4), maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3), using ferromagnetic resonance

We investigated intra/inter particle interactions in single domain size magnetite (Fe3O4), maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3) iron oxide particles. The magnetic analyses were done using vibrating sample magnetometer and magnetic resonance measurements that were taken from 5 to 300 K and from 120 to 300 K, respectively. The magnetic resonance analyses were done for the iron oxides, frozen under 5000 G fields in glycerol matrix. By changing the temperature, a change in resonance field lines was observed at each Fe3O4, gamma-Fe2O3 and alpha-Fe2O3 nanoparticles. However, the fits in resonant lines showed that Lande g values (spectroscopic splitting factor) stayed stable with temperature decrease. The thermal sensitivities that were determined from Lande g factors, revealed three dominant interactions on resonant lines namely; the exchange coupling in between Fe2+, Fe3+ and O (g(1) = 3.01 +/- 0.08), Fe3+ centers (1.88 +/- 0.03 <= g(2) <= 2.02 +/- 0.03, depending on iron oxide states) and flip flop of O ions in between ionic states of Fe2+-O (1) and Fe3+-O (2) (2.35 +/- 0.06 <= g(3) <= 2.44 +/- 0.06, depending on iron oxide states). (C) 2012 Elsevier B.V. All rights reserved

Size dependent heating ability of CoFe2O4 nanoparticles in AC magnetic field for magnetic nanofluid hyperthermia

We investigated the size dependent magnetic properties and heating mechanism of spinel CoFe2O4 nanoparticles, which synthesized using the nonhydrolytic thermal decomposition method. The size of CoFe2O4 nanoparticles was arranged with the variation of solvent type, reflux time, and reflux temperature. The optimum size range was determined for magnetic fluid hyperthermia. The particles with 9.9 +/- 0.3 nm average diameter have the highest heating ability in the AC magnetic field having 3.2 kA/m amplitude and 571 kHz frequency. The maximum specific absorption rate of 22 W/g was obtained for 9.9 +/- 0.3 nm sized CoFe2O4 nanoparticles. The calculations and experimental results showed the dominancy of Brownian relaxation at the heat production of synthesized 9.9 +/- 0.3 nm nanoparticles. In contrary, the magneto-heating in 5.4 +/- 0.2 nm particles mainly originated from Neel relaxation

Domain state-dependent magnetic formation of Fe3O4 nanoparticles analyzed via magnetic resonance

Magnetic properties, arising from surface exchange and interparticle interactions of the Fe3O4 (magnetite) nanoparticles, were investigated in the temperature range of 5-300 and 120-300 K using vibrating sample magnetometer technique and electron spin resonance spectroscopy, respectively. The research was based on to figure out the origin of intraparticle interactions and the change of interparticle interactions in wide size range Fe3O4 nanoparticles. The analyses were done for samples having almost same particle size distributions. The average particle sizes were changed in between 30 +/- A 2 and 34 +/- A 2 nm. The observed magnetization values were demonstrated the mixture of single-domain size particles, exhibiting both single-domain (SD) and superparamagnetic (SPM) states. The symmetry of resonance curves changed according to the ratio of SD and SPM-stated particles in mixture under located temperature. The changes of anisotropy up to domain state were understood by freezing magnetic moment in glycerol matrix from room temperature to 120 K under 5-kG field. The shift of H (R) values to higher magnetic fields and the more symmetric resonance spectrum proved the effect of anisotropy and interparticle interactions fields on magnetic behave. In addition, the origin of intra-interaction was exposed from Fe3+ centers and exchange coupling in between Fe2+, Fe3+, and O-, and Fe3+ centers found from g factor (g)

Magnetic behaviour of iron nanoparticles passivated by oxidation

This study is to understand the effect of oxidation, especially magnetically, on iron nanoparticles. According to generation of the oxidated iron nanoparticles, mechanical alloying technique was used and nanosized magnetite (Fe3O4) maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3) particles were obtained as the resultant samples. The reactance to the thermal treatment was determined by differential thermal analysis and thermogravimetric (DTA-TG) measurements. X-ray powder diffractions (XRD) helped to exhibit the structure of the sample by ICDD cards and to determine the size of nanoparticles by using the Scherrer formula. On the other hand, VSM (vibrating sample magnetometer) measurements were determined to understand the magnetic behaviour. Through the transformation of Fe3O4 to other iron-oxides, two exothermic peaks were observed at around 169.11 degrees C and 562.61 degrees C by DTA analysis. Beside of this, the experimental results demonstrate the effects of mechanical milling parameters, atmosphere and lubricant, to the structure and to the size of the resultant particles and the change of magnetic behavior of the iron-oxide and iron nanoparticles when they approach to superparamagnetic region, especially in single domain region

Interparticle interaction effects on magnetic behaviors of hematite (alpha-Fe2O3) nanoparticles

The interparticle magnetic interactions of hematite (alpha-Fe2O3) nanoparticles were investigated by temperature and magnetic field dependent magnetization curves. The synthesis were done in two steps; milling metallic iron (Fe) powders in pure water (H2O), known as mechanical milling technique, and annealing at 600 degrees C. The crystal and molecular structure of prepared samples were determined by X-ray powder diffraction (XRD) spectra and Fourier transform infrared (FTIR) spectra results. The average particle sizes and the size distributions were figured out using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The magnetic behaviors of alpha-Fe2O3 nanoparticles were analyzed with a vibrating sample magnetometer (VSM). As a result of the analysis, it was observed that the prepared alpha-Fe2O3 nanoparticles did not perform a sharp Morin transition (the characteristic transition of alpha-Fe2O3) due to lack of unique particle size distribution. However, the transition can be observed in the wide temperature range as "a continuously transition". Additionally, the effect of interparticle interaction on magnetic behavior was determined from the magnetization versus applied field (sigma(M)) curves for 26 +/- 2 nm particles, dispersed in sodium oxalate matrix under ratios of 200:1, 300:1, 500:1 and 1000:1. The interparticle interaction fields, recorded at 5K to avoid the thermal interactions, were found as similar to 1082 Oe for 26 +/- 2 nm particles. (C) 2011 Elsevier B.V. All rights reserved