摘要:

Ultrafast optoelectronic characteristics of GaAs implanted with 200 keV arsenic ions at dosage as low as1013 ions/cm2are reported. Ultrashort photoexcited carrier lifetimes of0.23±0.02,0.87±0.02,and3±0.2 pswere determined for as-implanted, rapid thermal annealing (RTA) (600 °C for 30 s) and furnace-annealed (600 °C for 30 min) arsenic-ion-implanted GaAs orGaAs:As+,respectively. The switching response of photoconductive switches (PCSs) fabricated on the latter two materials were∼3and 8 ps, respectively. The leakage current of the PCS fabricated on furnace-annealed sample was as low as 30 nA. The breakdown fields exceeded 150 (instrument-limited) and 90 kV/cm for furnace- and RTA-annealed samples, respectively. The optical responsivity of low-dosage arsenic-implanted GaAs photoconductive switch can be as high as 0.01 A/W. This also compared favorably with the same device made on state-of-the-art photoconductor such as molecular-beam epitaxy grown GaAs at low temperatures. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120210

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Nd-dopedLiNbO3films have been prepared on (012) sapphire substrates by pulsed laser deposition.LiNbO3phase is formed using Li rich targets, a1.5×10−2 mbaroxygen pressure atmosphere, and heating the substrate to 520 °C. The crystallinity of 1-&mgr;m-thick films has been enhanced by postdeposition thermal treatments at 600 °C. The [Nd]/[Nb] concentration ratio in the film is equal to its value in the target; however, a limit for the Nd incorporation to theLiNbO3phase has been found due to the preferential nucleation of Li deficient phases for[Nd]/[Nb]>0.1.The Nd photoluminescence of the films have been studied at 77 K exciting the4F3/2multiplet. The photoluminescence of congruentLiNbO3single crystals is well reproduced in films prepared from targets with a[Li]/[Nb]=1.6composition. Films prepared from targets with a[Li]/[Nb]=3composition, additionally show an emission, with a main maximum at 1064 nm, the splitting of the4F3/2multiplet being80 cm−1.The possible origin of the latter photoluminescence is discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120211

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Atomic force microscopy (AFM) has been used to modify a polyimide surface to give controlled liquid crystal (LC) alignment, and to examine the modification produced. Strong LC azimuthal anchoring was observed typically for normal forces>300 nNand line densities>5 &mgr;m−1,and optically diffracting LC elements were fabricated by repeatedly overpatterning the same area along different directions. Atomic force microscopy images showed little sign of topographic modification such as grooving, whereas lateral force images showed locally increased friction. Estimated contact pressures, 0.08–0.3 GPa, suggest shear-yielding occurs within a surface layer, causing polymer chain alignment. The AFM micromechanical interaction is compared with that occurring during the conventional cloth-rubbing LC alignment process.

ISSN:0003-6951    

DOI:10.1063/1.120212

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Monolithic colliding pulse mode locking of a molecular beam epitaxy (MBE) grown GaAs/AlGaAs quantum well laser has been achieved through back doping of the active region to simulate the residual doping present in metal organic vapor phase epitaxy grown mode-locked laser wafers. Frequency domain measurements are presented which show multiple colliding pulse mode-locked operation of an MBE grown device at 186 and 372 GHz. Devices with no intentional doping in the active layer showed no evidence of mode-locked operation. Band-edge absorption spectra are also presented which indicate the effect doping has in broadening the excitonic linewidth in the saturable absorber. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120213

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The process of bias-enhanced nucleation of diamond has been monitored and analyzed by ellipsometry. The time evolution of optically equivalent thickness has been obtained and it has been confirmed with the help of x-ray photoelectron spectroscopy that four stages exist: they are carbonization, incubation, nuclei growth, and film growth. It has been considered, during the incubation stage, that carbonization and etching proceed simultaneously and that high density and oriented diamond nuclei are generated by the accelerated elimination of weak C–C bonds and the faster formation ofsp3C–C bonds in a substrate. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120214

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Laser-ablation atomic fluorescence (LAAF) spectroscopy has extremely high sensitivity in the analysis of trace elements. Using the ArF laser-ablation technique at a wavelength of 193 nm, removal of thin surface layer of the order of 1.1 nm/shot for the first 50 shots and 0.4 nm/shot after that is demonstrated for a solid glass sample. A constant fluorescence signal from Na atoms is obtained for each shot. There is a possibility of determining the depth distribution of an element with subnanometer resolution by applying LAAF spectroscopy. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120215

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A novel type of poly(p-phenylenevinylene)s which contain (bis(2,2′:6′,2′′-terpyridine) ruthenium (II) complexes has been developed. The absorption of the polymers at 500 nm was strongly enhanced by the metal complexes due to the presence of the metal–ligand charge transfer transition. The charge transportation is dispersive with hole carrier mobilities and activation energy of∼7×10−5 cm2 V−1 s−1and 0.20 eV, respectively, depending on the concentration of the metal complex. A log &mgr; vsE1/2plot shows that hole mobilities decrease with increasing field, which suggests the presence of off-diagonal disorder in the hopping sites. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120548

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Erbium-doped multicomponent phosphate glass waveguides were deposited by rf sputtering techniques. The Er concentration was5.3×1020 cm−3.By pumping the waveguide at 980 nm with a power of∼21 mW,a net optical gain of 4.1 dB at 1.535 &mgr;m was achieved. This high gain per unit length at low pump power could be achieved because the Er–Er cooperative upconversion interactions in this heavily Er-doped phosphate glass are very weak [the upconversion coefficient is(2.0±0.5)×10−18 cm3/s], presumably due to the homogeneous distribution of Er in the glass and due to the high optical mode confinement in the waveguide which leads to high pump power density at low pump power. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120216

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Double capillary scheme is proposed for high performance electrical discharge in a capillary. This scheme allows more than103shots without significant destruction. It is shown that a thin main capillary can be filled with the plasma formed in a trigger capillary discharge so that the discharge in the main capillary can be excited and a hollow distribution of electron density can be obtained with concentration of up to a few1019cm−3.Main properties of this scheme are reported. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120217

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

As semiconductor manufacturing moves towards smaller logic devices and thinner gate oxides, there is serious concern that pattern-dependent charging during plasma etching will impede progress by distorting etch profiles and by causing oxide breakdown. Simulations of the final overetch predict that the use of ultrathin oxides(⩽5 nm),combined with a low substrate potential, will actually eliminate notching by enabling electron tunneling from the substrate to decrease surface charging potentials at the bottom of high aspect ratio trenches. Comparison with published experimental results validates the simulations. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120218

出版商:AIP    

年代:1997

数据来源: AIP