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Two series of samples of single-layer IrMn and IrMn/FePd bilayer films, deposited on a single-crystal MgO substrate at different IrMn deposition temperatures (Ts=300-700 °C), were investigated using magnetron sputtering. L12 ordering was revealed for the 30nm-thick IrMn epitaxial (001) films with Ts⩾400 °C, determined by synchrotron radiation x-ray diffractometry (XRD). XRD results also provide evidence of the epitaxial growth of the IrMn films on MgO substrate. Increasing Ts from 400 to 700 °C monotonically increases the ordering parameter of L12 phases from 0.17 to 0.81. An in-plane exchange bias field (Heb) of 22Oe is obtained in a 10nm-thick FePd film that is deposited on the disordered IrMn films. As the L12 ordering of the IrMn layers increases, the Heb gradually decreases to 0Oe, meaning that the exchange bias behavior vanishes. The increased surface roughness, revealed by atomic force microscopy, of the epitaxial IrMn layers with increasing Ts cannot be the main cause of the decrease in Heb due to the compensated surface spins regardless of the disordered and ordered (001) IrMn layers. The change of antiferromagnetic structure from the A1 to the L1H2 phase was correlated with the evolution of Heb. [ABSTRACT FROM AUTHOR]

Shot noise, which accompanies the emergence of the quantization nature (discreteness) of electrons, indicates dynamic fluctuations in electrical current and further reveals underlying operations in mesoscopic applications. This work presents a multichannel junction device with which to study the shot noise of coupled-channel transports as in normal nanocircuits, and it describes the theoretical algorithms. The numerical results show that, in contrast to the indistinguishable results of average current on direct-current measurements, the shot noise related to a dynamic current definitely exhibits significant differences among devices with diverse multichannel set-ups and presents super-Poissonian behaviors associated with the splitting of tunneling states. [ABSTRACT FROM AUTHOR]

The use of a differential capacitance technique for analyzing the effect of strain relaxation on the electronic energy band structure in relaxed InAs self-assembled quantum dots (QDs) is presented. Strain relaxation is shown to induce a deep defect state and compensate the ionized impurity in the bottom GaAs layer, leading to a double depletion width and a long emission time. An expression of capacitance at different frequency and voltage is derived for analyzing the experimental data. It has been shown that the relationship between the low-frequency and high-frequency capacitances can be well explained by a Schottky depletion model with a compensated concentration in the bottom GaAs layer. A simple expression is presented to account for the modulation of the free electrons in the top GaAs layer. This capacitance analysis shows a long low-energy tail for the electron ground state, suggesting not very uniform strain relaxation. The results of this study illustrate a carrier compensation effect of the defect state on the electronic energy band structure near the QDs. [ABSTRACT FROM AUTHOR]

This work utilizes low-energy sputtering to incorporate the generated nitrogen plasma into an epitaxial 1.4 nm Co film on the surface of a ZnO(002) substrate. In this method, ultrathin Co–N amorphous films were formed. Interestingly, Co is key to the formation of Co–N films. Without the deposition of Co on the ZnO(002), nitride films cannot be formed. Observations of the surface composition of the Co–N films after the firing of a N+ ion beam onto it demonstrated that the surface concentration of Co reduced at the same rate as the reduction in the concentration of N upon successive sputtering. Theoretical calculations based on the Auger peak-to-peak amplitudes established that the composition of the amorphous Co–N thin films may be Co3N2. [ABSTRACT FROM AUTHOR]

In this study, the viscous flow behavior and thermomechanical properties of Mg65Cu25-xBxGd10 (x=0 and 3 at. %) bulk metallic glasses (BMGs) in the supercooled liquid region have been investigated by using differential scanning calorimetry and thermomechanical analyzer. It has been found that the fragility of the supercooled liquid is reduced by the boron addition, thus, degrading the deformability. This conclusion is supported by the many other extracted parameters. Thus, even with much higher hardness, the B-additive Mg based BMG will be more difficult to be formed, which appears to be a negative factor in applying in the microforming or nanoimprinting industry. [ABSTRACT FROM AUTHOR]

Atomically smooth Ga2O3(Gd2O3)/GaAs interface with low interfacial density of states and low electrical leakage currents have been achieved after the heterostructures were air exposed and tailor annealed to ∼750 °C. The heat treatments, with annealing at an intermediate temperature of ∼300 °C as a necessary step, were carried out under ultrahigh vacuum (UHV) and via standard rapid thermal annealing with flow of pure nitrogen gas. Furthermore, the oxide remains amorphous and minimal interfacial reaction occurred between the oxide and substrate, critical aspects for device performance. Studies using x-ray reflectivity and high-resolution transmission electron microscopy show that the interfacial roughness is <0.2 and <0.4 nm for annealing under UHV and non-UHV, respectively. Electrical measurements on the metal-oxide-semiconductor diodes have exhibited low leakage currents (10-8–10-9 A/cm2), a dielectric constant of >=14, and a low interfacial density of states (Dit) of <1012 cm-2 eV-1. [ABSTRACT FROM AUTHOR]

CoFeB films were deposited on glass substrate by the sputtering method. From x-ray-diffraction and electron-diffraction-ring patterns, the major phase in the as-deposited CoFeB film is amorphous (or nanocrystalline). However, we could also identify a minor CoFe(110) crystalline phase in the film. We have tried to suppress this crystalline phase by changing the Ar partial pressure (PAr) during deposition and found that the optimal condition is PAr=5×10-3 Torr. Because the electrical resistivity value (ρ) of the film is in general larger than 100 μΩ cm, it also indicates that the amorphous phase is dominant. From the temperature coefficient of resistance measurement, we learn that the amorphous phase in the CoFeB film crystallizes in succession at two higher temperatures (Tcr1 and Tcr2) than the room temperature (RT). Besides the electrical properties, the film thickness (tf) dependence of saturation magnetization (Ms), saturation magnetostriction (λs), and coercivity (Hc) has also been discussed. From the Auger-depth profile analysis, it is found that there is one CoOx (with 0.4<=x<1) oxide layer, about 15 Å in thickness, lying on the top surface of the CoFeB film, and another CoOx oxide layer, about 20 Å, lying near the CoFeB/glass interface. At RT CoOx is supposed to be paramagnetic. However, due to the proximity effect between CoOx and CoFeB, the CoOx layers may become ferromagnetic with the average magnetization Mox. By fitting the Ms data as a function of (1/tf), we can show that the last conjecture is correct, and Mox is not zero. The CoOx layer plays an important role on Ms,λs, and Hc of the CoFeB films with tf ranging from 50 to 503 Å. [ABSTRACT FROM AUTHOR]

Presents a study which focused on electronic structures of indium[sub1-x]gallium[subx]arsenide-indium phosphide strained-layer quantum wells. Theoretical approach; Results and discussion; Conclusion.

Presents a study that investigated the effects of valence-band mixing on the gain and on the refractive index change of the quantum-well laser and the effect of an applied electric field perpendicular to the quantum wells for gain switching. Electronic properties of quantum wells; Gain and refractive index change of the quantum-well laser structure; Conclusion.

Presents a study which investigated the absorption of infrared radiation at normal incidence from intervalence-subband transitions. Method to enhance absorption; Description of the infrared absorption from intervalence-subband transitions; Features of the absorption.

To investigate the crystallographic structure and the magnetic properties as a function of chemical composition (40-62 at. %) and substrate temperature (Ts=300-550 °C), we fabricated epitaxial FePd films of thickness 20±2 nm by sputtering on MgO (100) single-crystal substrates. The ordering parameter, measured by x-ray diffraction with synchrotron radiation, and the perpendicular anisotropy of the Fe54Pt46 films increased with increasing substrate temperature. For FePd films (Ts=550 °C) with varied Fe content, a direct correlation between the ordering parameter and the magnetocrystalline anisotropy field is found. The greatest ordering parameter, 0.84, and magnetocrystalline anisotropy field, °20 kOe, were obtained for FePd films of Fe concentration 54 at. %, indicating that an off-stoichiometric L10 FePd might be preferable for engineering and applications. [ABSTRACT FROM AUTHOR]

Magnetic properties of microstructured Permalloy thin film cross have been studied using magnetic force microscopy and magnetoresistance measurement. Three types of magnetization configurations formed within the junction area were observed, including two kinds of magnetic pattern having two inward and two outward magnetizations and one with three outward and one inward magnetizations. The presence of those variant magnetic configurations gives rise to an irreversible magnetoresistance behavior originated from the distinct magnetization history. Asynchronous magnetization reversal of each arm provides a chance to manipulate the magnetic pattern of the cross. [ABSTRACT FROM AUTHOR]

The magnetic structures and hysteresis loops of permalloy thin film arrays are investigated here using magnetic force microscopy and vibrating sample magnetometer. The strength of interparticle dipole interaction can be revealed by the number of single-domain pairs with antiparallel magnetizations when the array is relaxed from a strong hard-axis field. Besides, hysteresis loops obtained by vibrating sample magnetometer measurements show that arrays with narrower interparticle spacings have lower coercivities and remanences. The results obtained from vibrating sample magnetometer are in very good agreement with magnetic force microscopy imaging. [ABSTRACT FROM AUTHOR]

We study the structure and perpendicular magnetism of molecular beam epitaxy grown (FePt)[SUB1-x]Mn[SUBx] films with doping concentration x = 0, 1%, 2%, 3%, 4%, and 5%. The (FePt)[SUB1-x]Mn[SUBx] films were made by multilayers growth of [Fe/Pt/Mn]×N at 100 °C and annealed at 600 °C. X-ray diffraction scans indicate that relatively better L1[SUB0] ordered structure for low Mn doping (x < 2%). The (001) and (003) superstructure peaks decrease with the increase of the Mn doping for x&ges;2%, and a significant (111) peak appears for x > 3%. The perpendicular magnetic anisotropy effect of the (FePt)[SUB1-x]Mn[SUBx] films tends to decrease with the increase of Mn doping for x > 1% However, the x = 1% doped films possess slightly better perpendicular magnetic anisotropy effect than the zero doped film. The perpendicular magnetic anisotropy constant are of about 1.3 × 10[SUP7] and 1.6 × 10[SUP7]erg/cm[SUP3] for x = 0% and x = 1%, respectively. [ABSTRACT FROM AUTHOR]