Search Results - (Author, Cooperation:J. S. Huang)

2018-06-02

Institute of Physics (IOP)

1674-1137

Physics

2018-02-12

Institute of Physics (IOP)

1674-1137

Physics

2018-07-27

Institute of Physics (IOP)

1674-1137

Physics

2018-06-03

Institute of Physics (IOP)

1755-1307

1755-1315

Geography

Geosciences

Physics

2018-04-10

The American Association of Immunologists (AAI)

0022-1767

1550-6606

Medicine

2018-02-10

The American Association of Immunologists (AAI)

0022-1767

1550-6606

Medicine

2013-10-25

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2018-10-09

The American Society for Pharmacology and Experimental Therapeutics

0022-3565

1521-0103

Medicine

2018-10-13

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We have used static and dynamic light scattering to study the dynamics of aggregation of synthetic melanin, an amorphous biopolymeric substance, in low pH aqueous solution. We have found that, depending on the final pH value of the solutions, there existed two regimes of the aggregation kinetics, one corresponding to diffusion limited aggregation (DLA), and the other corresponding to reaction limited aggregation (RLA). The precipitates formed in these two regimes can be characterized by fractal structures. We have found fractal dimensions of df =1.8 for the DLA clusters and df =2.2 for the RLA clusters. These results agree well with the proposed limits of the fractal dimensions of the gold aggregates formed in aqueous solutions by Weitz et al.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We have activated heavily boron-doped and arsenic-doped silicon-on-insulator (SOI) strips by applying electrical current. The SOI strips were implanted with 40 keV BF2+ or As+ at a dosage of 5×1015 ions/cm2. Without postimplantation annealing, these implanted SOI strips can be activated by applying a current up to 1×106 A/cm2, the resistance decreased from 8.80 to 0.61 kΩ for a 10 μm wide, 50 μm long, and 0.2 μm thick n+ silicon strip, for instance. This reduction of resistance is close to that obtained by the conventional postimplantation annealing at 900 °C for 30 min. To separate the effect of Joule heating from that of current activation, the temperature of the SOI strips during the current activation has been measured by Pt sensors. The result indicates that the temperature rise due to Joule heating is low and cannot explain the observed activation. We conclude that implanted dopants in Si can be activated by current stressing. To confirm it, carrier concentration obtained by Hall measurement is presented. © 1999 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

With continuing scaling down in microelectronic devices, the current density and the power consumption in the devices must increase. Hence, device reliability under high current density is an issue for ultralarge-scale integration technology. This study investigates the heating behavior of the heavily doped Si channels under high current stress. Thermal and electrical characterization of the channels in bulk Si and in silicon-on-insulator were conducted. An abnormal asymmetrical heating along the channels in bulk Si has been observed. We propose a junction leakage mechanism to explain the phenomenon observed. Other asymmetrical thermal effects, such as electron–hole recombination and Peltier effect, have also been discussed. © 1999 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We have studied the oxidation kinetics of Cu and Cu3Ge thin films in air using in situ resistivity measurement and x-ray photoelectron spectroscopy. Thin films of Cu oxidize in air around 250 °C to form CuO with an activation energy of 0.74 eV. In contrast to Cu, thin films of Cu3Ge oxidize only above 450 °C. The excellent oxidation resistance of Cu3Ge is due to the thin GeO2 layer which protects Cu3Ge from oxidation below 450 °C. Above 510 °C, GeO2 evaporates and the oxidation protection is lost. Besides the excellent oxidation resistance and low resistivity, we also found Cu3Ge to have a better adhesion to SiO2 than Cu. It has the potential to be used as an adhesion layer and passivation layer in Cu metallization. © 1995 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Two-dimensional simulations of amorphous silicon thin-film transistors are presented for the case when source-drain voltage is turned on long before gate voltage is turned on. Discrepancies between these results and the one-dimensional results of M. F. Willums, M. Hack, P. G. LeComber, and J. G. Shaw [MRS Symp. Proc. 258, 985 (1992)] are discussed. Valid reasons for drain current decay are provided, and occupation dynamics for the trap states are shown in order to distinguish these from the one-dimensional results of C. van Berkel, J. R. Hughes, and M. J. Powell [J. Appl. Phys. 66, 4488 (1989)] where a two-fluid model occupation function was assumed. The invalidity of such approximation is explicitly demonstrated. The mean trap-filling energy level moves up in three stages: First, the level varies with log t, then varies linearly with t, and finally, with log (log t) to a steady-state level.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Cu3Ge films have been found to have a low resistivity, good adhesion onSiO2, good thermal stability on Si, and good oxidation resistance. It has the potential as an ideal adhesion/barrier/passivation layer for Cu ultralarge scale integration metallization. The kinetics of Cu3Ge formation and the thermal stability ofCu3Ge against Al were studied by in situ resistivity measurement, Rutherford backscattering spectrometry, and transmission electron microscopy. We found that Cu reacted with Ge in the temperature range of 100–200 °C. The activation energy of the Cu–Ge compound formation was found to be 1.1±0.1 eV. The Cu–Ge compound was identified asε-Cu3Ge from transmission electron microscope diffraction patterns. Upon annealing theε-Cu3Ge became unstable on Al at the temperature range of 300–350 °C. In the reaction between Al andCu3Ge, Cu preferentially reacted with Al to form anε-Al2Cu3 compound. The activation energy of formation of the Al–Cu compound was found to be 2.1±0.1 eV. © 1997 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Stability of contacts in shallow junction devices against high current density is a reliability issue for very large scale integration technology. We have observed a strong polarity effect on failure at nickel and nickel silicide contacts on both n- and p-type Si under high stress conditions. In a pair of cathode and anode contacts the Ni/n+-Si contact pair fails at the anode, while the Ni/p+-Si pair fails at the cathode. The Ni/Ni2Si/n+-Si and Ni/Ni2Si/p+-Si were found to fail preferentially at the cathode. Microbeam Rutherford backscattering spectrometry and Auger electron spectroscopy depth profiles show that a silicide reaction occurs between Ni and Si during current stressing, especially at the failed contacts. In situ resistance data indicate that the resistance of the failed contact increases with time while that of the other contact in the pair remains constant. Transmission electron microscopy shows that the silicide formation is not uniform at the damaged contacts. A mixture of dominant epitaxial NiSi2 and a minor amount of polycrystalline NiSi2 phases was identified. We have proposed mechanisms to explain the polarity effect on failure: wear-out mechanism for the damaged positive contacts of Ni/n+-Si, electromigration enhanced silicide formation for the damaged negative contacts of Ni/Ni2Si/n+-Si and electron-hole recombination mechanism for the damaged negative contacts of Ni/p+-Si and Ni/Ni2Si/p+-Si. © 1997 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Electromigration-induced resistance behavior of via-terminated metal lines was studied. We found a strong correlation between void morphology and step-like resistance behavior. For the lines which exhibit pronounced resistance steps, voids are formed at the top or bottom Al/TiN interface. For the lines which exhibit gradual resistance increases, only complete void formation severing the whole line occurs. The step-like resistance behavior is more pronounced when the current density is close to the critical current density. Possible mechanisms for the resistance steps are discussed. © 2001 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A technique for inducing white-light emission from organic multiheterostructures is proposed. The configuration of organic multiheterostructure white-light emitting diodes is ITO/TPD(50 nm)/BePP2(5 nm)/TPD(4 nm)/BePP2:rubrene(5 nm)/TPD(4 nm)/Alq3(10 nm)/Al. Triphenyldiamine derivative (TPD) is used as a hole-transporting layer and the potential barrier layers. Blue fluorescent phenylpyridine beryllium (BePP2), orange fluorescent rubrene, and green fluorescent aluminum complex (Alq3) are used as three primary colors. BePP2 and BePP2 doped with rubrene act as the potential wells sandwiched between TPD barrier layers, in which excitons are confined. Alq3 is used as an electron-transporting green-color emitter. The white-light emission spectrum covers a wide range of the visible region, and the Commission Internationale de l'Eclairage coordinates of the emitted light are (0.32, 0.38) at 9 V. The maximum brightness and luminous efficiency of this device are 4000 cd/m2 (at 17 V) and 0.4 lm/W, respectively. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We demonstrate low-voltage inverted transparent vacuum deposited organic light-emitting diodes employing an indium-tin-oxide coated glass substrate directly as cathode and a semitransparent top Au thin film as anode. The devices comprise an intrinsic 8-tris-hydroxyquinoline aluminum (Alq3) emitting layer sandwiched in between n- and p-doped charge transport layer with appropriate blocking layers. They exhibit low driving voltages (∼4 V for a luminance of ∼100 cd/m2). The devices are about 50% transparent in the Alq3 emission region and emit green light from both sides with a total external current efficiency of about 2.5 cd/A. © 2002 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The p+- and n+-Si channels were prepared by implanting a dose of 5×1015 ions/cm2 of BF2+ and As+ at 40 keV, respectively, into the n-Si and p-Si substrates, followed by a 900 °C-30 min annealing. Nickel contacts (cathode and anode) to these channels were electron-gun evaporated. Electrical current was applied gradually to 80 mA to these channels, corresponding to current densities of 106–107 A/cm2. For the p+-Si, the resistance responded by increasing to a maximum, then decreasing until a precipitous drop took place. For the n+-Si, the resistance increased by a less amount compared to the p+-Si, but also dropped abruptly. The resistance drop is permanent in the p+-Si channels, but not in the n+-Si channels. Mechanisms responsible for these resistance changes in terms of Joule heating, high field effect and junction leakage are proposed. For the precipitous drop in channel resistance of the p+-Si, scanning electron microscopy and transmission electron microscopy showed that a NiSi2 line bridging the cathode and anode contacts had been formed. No silicide line formation in the n+-Si channels was observed. © 1998 American Institute of Physics.

Electronic Resource