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detailed study is presented on magnetic, electrical and optical properties of GaMnN: Si film grown by metal organic chemical vapor deposition (MOCVD) with high-purity SiH as the Si dopant source. The room-temperature field dependence magnetization and zero-field-cooled (ZFC)/field-cooled (FC) measurements indicate that the film remains room-temperature ferromagnetism and it declines slightly after Si co-doping. However, room-temperature Hall measurements indicate that the electrical property of the film improves distinctly compared with GaMnN. Cathode luminescence (CL) measurements show an obvious enhancement in luminous property and different peak strength changes at three different positions. Therefore, we demonstrate that Fermi level and the electron structure of Mn atoms will change with variation of the impurities co-doped and the intrinsic defects and this may be related with room-temperature ferromagnetism and the other corresponding properties of the film. [ABSTRACT FROM AUTHOR]

Room-temperature ferromagnetism with a Curie temperature higher than 380 K was studied in GaN: Mn thin films grown by metal-organic chemical vapor deposition. By etching artificial microstructures on the GaN: Mn layer, strong magnetic responses were observed in the magnetic force microscopy (MFM) measurement, which revealed that the films were independent of dopant particles and clusters. Numerical simulation on the data of atomic force microscope (AFM) and MFM measurements covering the whole microstructure validated the formation of long range magnetic order. This result excluded a variety of controversial origins of room-temperature ferromagnetism in the GaN: Mn and gave a strong evidence of our GaN: Mn as the intrinsic diluted magnetic semiconductor (DMS). The forwarded method for accurate characterization of long range magnetic order could be applied to a wide range of DMS and diluted magnetic oxide (DMO) systems. [ABSTRACT FROM AUTHOR]

Focuses on the application of multilayer X-ray mirrors in soft X-ray multilayer mirrors, while highlighting their application in determining the effects of carbon dioxide and carbon multilayers. Findings of studies conducted; Discussion of results attained.

The structural stability of heat-treated CoN/CN soft X-ray multilayers fabricated by dual-facing-target sputtering has been investigated by using complementary measurement techniques. The high temperature annealing results imply that the destructive threshold of the Co/C multilayers is improved by 100–200 degrees centigrade through doping with N. The low-angle X-ray diffraction of CoN/CN soft X-ray multilayers indicates that the period expansion of the multilayers is only 4 % at 400°C, and the interface pattern still exists even if they were annealed at 700°C. The Raman spectra analyses give the evidence that the formation of the sp3 bonding in the CN sublayers can be suppressed effectively by doping N with atoms, and thus the period expansion resulting from the changes in the density of CN layers can be decreased considerably. The X-ray photoelectron spectra analyses present the information of the existence of the strong covalent bonding between C and N atoms, and the ionic bonding between Co and N atoms, which can slow down the tendency of the structural relaxation. The interstitial N atoms decrease the mobility of Co atoms, and thus the fcc-Co and hcp-Co coexist even though the annealing temperature is much higher than the phase transformation temperature of 420°C, leading to the suppression of the grain growth. [ABSTRACT FROM AUTHOR]

The structures of the carbon sublayers in the annealed Co/C soft X-ray multilayers fabricated by using a dual-facing-target sputtering system have been characterized by transmission electron microscopy (TEM) and Raman spectroscopy (RS). The results suggest that the structural variations in the carbon layers can be roughly divided into three stages, i.e. ordering, crystalline and grain growth stages. At the ordering stage with annealing temperatures below 400°C, the amorphous carbon layers change from ones of bond-angle disorder and fourfold-bonding only to ones of threefold-bonding. At the crystalline stage, the amorphous carbon layers in the as-deposited multilayers crystallize to graphite crystallites in the annealing temperature range of 500–600°C. At the grain growth stage, the specimens are annealed at temperatures higher than 700°C. A growth in the graphite crystallite dimensions is observed, which is consistent with the TEM results. [ABSTRACT FROM AUTHOR]

The opposite and abrupt change trends of the electrical behavior between narrow and wide bang-gap multi-quantum-well (MQW) laser diodes (LDs) in the ‘threshold region’, which corresponds to the current region between two kinks in the IdV/dI-I curves, were confirmed from the apparent properties measured directly and junction properties extracted by our ac-IV method, as well as simulation calculations. In the threshold region, negative capacitance and series resistance curves in narrow bandgap LDs (wavelengths are 780 and 650 nm) drop down, while in wide-bandgap LDs (wavelengths are 450 and 405 nm), they jump up; the junction voltage curves in narrow bandgap LDs jump up, while in wide-bandgap LDs, they drop down. We qualitatively interpreted the opposite change trend of these electrical parameters, and concluded that different stimulated emission mechanisms caused this opposite change trend of LDs with these two types of materials. [ABSTRACT FROM AUTHOR]