Browsing by Author "Ku, HC"

Now showing 1 - 6 of 6

Anisotropic impurity scattering effects on T-c and H-c2 in YBa2Cu3Ox
(1999-03-01)
Lin, JY
;
Chen, SJ
;
Chen, SY
;
Chang, CF
;
Yang, HD
We have studied the impurity effects on the superconducting transition temperature T-c and the upper critical field H-c2 in electron irradiated YBa2Cu3Oy with in-plane oxygen defects and YBa2(Cu1-xZnx)(3)O-y. It is found that the effects of the same type of defects or impurities on T-c are the same regardless of the oxygen contents of the samples. Furthermore, T-c decreases slower in irradiated YBa2Cu3Oy than in YBa2(Cu1-xZnx)(3)O-y. This may be well explained by the model that the scattering due to in-plane oxygen defects is more anisotropic than that due to Zn impurities. The different behavior of the reduced slopes (dH(c2)/dT)(Tc)/(dH(c2)/dT)(Tc0) these two types of samples can also be understood in this context. [S0163-1829(99)08309-5].
Effects of annealing on magnetic properties of new ferromagnetic semiconductor (In, Al, Mn) As
(2005-10-01)
Chen, YF
;
Lee, WN
;
Huang, JH
;
Chin, TS
;
Guo, XJ
The effects of low-temperature (210 degrees C-290 degrees C) annealing on the microstructure, lattice constant, and magnetic properties of (In0.52Al0.48)(0.91)Mn0.09As grown by low-temperature molecular-beam epitaxy were studied. The results show that low-temperature annealing has little influence on the crystalline structure and interface quality Of (In0.52Al0.48)(0.91)Mn0.09As epilayer. In contrast, both the lattice constant and Curie temperature of (In0.52Al0.48)(0.91)Mn0.09As are found to be strongly dependent on the annealing temperature. The lattice constant linearly decreases with increasing annealing temperature; while the Curie temperature increases with increasing annealing temperature up to 250 degrees C, and then abruptly decreases upon further annealed at 270 degrees C and 290 degrees C.
(In0.52Al0.48)(1-x)MnxAs muted magnetic semiconductor grown on InP substrates
(2006-01-11)
Lee, WN
;
Chen, YF
;
Huang, JH
;
Guo, XJ
;
Kuo, CT
A series of diluted magnetic semiconductors, (In0.52Al0.48)(1-x)MnxAs (0 < x <= 0. 11), was successfully grown on InP substrate by low-temperature molecular beam epitaxy. Our results indicate that (In0.52Al0.48)(1-x)MnxAs exhibits interesting magnetic behaviours at 5 K: it shows paramagnetic-like behaviour when x <= 0.05 and ferromagnetic behaviour when x >= 0.06.
MBE growth and structural and magnetic properties of (In1-gamma Al gamma)(1-x)MnxAs-diluted magnetic semiconductors
(2006-04-01)
Lee, WN
;
Chen, YF
;
Huang, JH
;
Guo, XJ
;
Kuo, CT
A series of quaternary-diluted magnetic semiconductors, (In1-y,Al-y)(1-x)MnxAs, have been successfully grown on InP substrates by low-temperature molecular beam epitaxy. The (ln(0.52)Al(0.48))(1-x)MnxAs with x <= 0.11 were grown on a nearly lattice-matched In0.52Al0.48As buffer, while the (In1-y,Al-y)(1-x)MnxAs with a higher Mn content of 0.11 < x <= 0.18 were grown on a graded 3-layer In,-,,Al-y 'As buffer structure. The results of transmission electron microscopy and double-crystal X-ray diffraction reveal that all (In1-yAly)(1-x),Mn,As epilayers are single crystal with zincblende structure, and the lattice constant increases with increasing the Mn content. The magnetic measurements show that the (In1-y,Al-y)(1-x)MnxAs semiconductors exhibit a paramagnetic-like state for x <= 0.05 while a ferromagnetic state for x >= 0.05, and the Curie temperature of ferromagnetic (In1-yAly)(1-x) MnxAs increases with increasing Mn content. (c) 2006 Elsevier B.V. All rights reserved.
Simulation of InGaN quantum well laser performance using quaternary InAlGaN alloy as electronic blocking layer
(2005-11-01)
Chang, YA
;
Luo, CY
;
Ku, HC
;
Kuo, YK
;
Lin, CF
Laser performance of an InGaN edge-emitting laser using a quaternary InAlGaN electronic blocking layer is investigated. Varying the aluminum (Al) composition in InAlGaN with a fixed indium (In) value (Al : In = 5 : 1) indicates that a lower threshold current and higher characteristic temperature (T(0)) value can be obtained when the Al composition is higher than 20%. When Al = 25%, the threshold current is reduced at the expense of a decreased To value from 149 to 130 K when the In composition increases from 1 to 7% in a temperature range of 300-370 K. The decreased T(0) value is mainly attributed to the increase in electronic leakage current.
Spin and orbital magnetic moments of Fe3O4
(2004-08-13)
Huang, DJ
;
Chang, CF
;
Jeng, HT
;
Guo, GY
;
Lin, HJ
We present measurements of the spin and orbital magnetic moments of Fe3O4 by using SQUID and magnetic circular dichroism in soft x-ray absorption. The measurements show that Fe3O4 has a noninteger spin moment, in contrast to its predicted half-metallic feature. Fe3O4 also exhibits a large unquenched orbital moment. Calculations using the local density approximation including the Hubbard U method and the configuration interaction cluster-model suggest that strong correlations and spin-orbit interaction of the 3d electrons result in the noninteger spin and large orbital moments of Fe3O4.