One-dimensional, diluted magnetic semiconductor nanofibers have attracted increasing attention for their unique magnetic properties, large specific surface area, and high porosity. These qualities lead to excellent performance in magneto-optical devices, magnetic resonance imaging, ferrofluids and magnetic separation. The purpose of this study is to fabricate P-type one dimensional CuAlO2-based diluted magnetic semiconductor nanofibers. First, we fabricated Cu Al0.95Co0.05O2 nanofibers with an average diameter of 1 μm with the electrospinning method. The annealed nanofibers were thermally treated at a temperature of 1 100 ℃ and then shrunk to a diameter of about 650 nm. We used X-ray diffraction measurements and Raman spectra to confirm that the Cu Al0.95Co0.05O2 nanofibers had a single impurity free delafossite phase. The X-ray photoelectron spectroscopy analysis indicates that Co was present in the +2 oxidation state, resulting in an room temperature ferromagnetism in the Cu Al0.95Co0.05O2 fiber. This contrasts with nonmagnetism in pristine CuAlO2 fiber. The coercivity(Hc) value of 65.26 Oe and approximate saturation magnetization(Ms) of 0.012 emu/g demonstrate good evidence of ferromagnetism at room temperature for Cu Al0.95Co0.05O2 nanofibers.
Structure and design are proposed for a kind of novel polymer Mach-Zehnder electro-optic(EO)switch using side-coupled M series-cascaded EO microrings.Formulations are proposed to analyze its switching characteristics.The dependences of the device’s performances on M are thoroughly analyzed and concluded.As the increase of M from 2 to 10,the switching voltages for the 9 devices are as low as 0.84 V,0.82 V,0.52 V,0.5 V,0.37 V,0.36 V,0.29 V,0.28 V and 0.24 V,respectively;whereas the crosstalks under bar state are within-20.79--6.53 d B and those under cross state are within-20.36--5.29 d B.The analysis results indicate that a smaller M is preferred for dropping the insertion loss and crosstalk,and a larger M should be selected to increase the optical bandwidth and minimize the switching energy.Generally,due to low switching voltage,the proposed device shows potential applications in optical networks-on-chip.
Based on wide-band infrared(IR) light source and dual-channel pyroelectric detector with detection channel of 4.66 μm and reference channel of 3.95 μm,a differential mid-infrared(MIR) carbon monoxide(CO) detector is designed and implemented.In order to reduce the detection limit and improve the detection sensitivity,an open spherical mirror chamber is designed and fabricated according to the divergence angle of the light source.The CO detection system is established using the welded and debugged detection circuits,a series of CO gases with different concentrations are prepared,and gas concentration calibration experiment is carried out.Experimental results indicate that after the amplifying circuit,the signal-to-noise ratios(SNRs) of the two channels are 17.58 dB and 18.46 dB,respectively,and the detection error of this system is less than 9% in 0%-4% measuring range.The detection sensitivity in the low concentration range is approximately 0.05%.6 h measurement on the 0 ppm sample gas shows that the fluctuation range is about ±0.02%,and the measurement standard deviation is about 0.89%.
Ternary In-rich Alx In1-xN films were successfully grown on Si(111) and(0001) sapphire substrates by radio-frequency magnetron sputtering on a relatively Al-rich Alx In1-x N layer after AlN buffer.X-ray diffraction(XRD) patterns of the films indicate highly c axis-oriented wurtzite structure and the indium content of about 0.76 has been evaluated according to the Vegard's law.An Al-rich Alx In1-xN transition layer was formed between the ultimate In-rich Alx In1-xN film and the AlN buffer,which served as a further buffer to alleviate mismatch.X-ray photoelectron spectroscopy(XPS) depth profiling analyses confirm the alternative of indium and aluminum composition and the unavoidable oxygen impurities from surface to bulk.Owing to high indium content,obvious E 2 Hand InN-like A 1(LO) phonon model accompanying with slight AlN-like A 1(LO) phonon model are observed.Hall effect measurements demonstrate n-type electrical conductivity in these alloys with carrier concentrations n=1019cm-3.The strain in In-rich Alx In1-xN films can be significantly reduced by introducing an Al-rich interlayer,facilitating the improvement of film quality for diverse device applications.
