摘要:

We report on the design and the optical properties of a spin‐coated multilayer organic microcavity. Tri(stilbene)amine blended with polysulfone as the first layer and an oxadiazole derivative (BPBD) blended with polystyrene as the second layer are sandwiched between two planar mirrors. Enhancement of the luminescence and spectrally narrow emission are observed. By means of time resolved luminescence spectroscopy we show that the spontaneous emission rate is increased in the cavity. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113222

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A variety of GaP lens arrays have been routinely produced (array dimensions up to 1.5×1.0 cm, 30×50 elements) with high yield, uniformly good finish, and low transmission loss for 0.8 &mgr;m<&lgr;<2.5 &mgr;m. Microlenses up to 300 &mgr;m in diameter withfnumbers as low as 0.7 have been fabricated by a new sealed ampoule mass‐transport technique. The mesa‐step spacing was increased from 10 to 15 &mgr;m, with mass‐transport smoothing time‐at‐temperature as short as 8 h, representing a transport‐rate 10–40 times higher than previously reported. By additional chemistry control, smoothing of 30 &mgr;m spacings has been demonstrated. Only small pieces of phosphorus are required (no phosphine or hydrogen), consequently little safety burden is incurred. Smoothing in the fused quartz ampoules is shown to be self‐terminated by wafer oxidation, which is sufficiently delayed by loose‐fitting aluminum oxide shielding. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113223

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence of 1.3 &mgr;m wavelength strained multiple quantum well InGaAsP/InP laser structures has been used to understand the excess carrier redistribution between the quantum well and waveguide regions at a high level of excitation. A model is developed to describe the experimental results. The model suggests that space charge barriers play a significant role in the electron confinement in quantum wells at the high excitation range typical of laser diode operation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113224

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Off‐resonant nonlinear optical measurements have been made in a Fabry–Perot cavity containing a polydiacetylene (PTS) single crystal. The cavity length was controlled to select specific bias points on the Fabry‐Perot fringe and the measurements were made by a pump‐probe technique using 90 ps pulses at 1.06 &mgr;m wavelength. The changes in transmission at selected bias points were measured as a function of time delay between the pump and the probe. The measured response time was found to be pulse‐width limited and the maximum changes in transmission were as large as 50% at low optical intensities (∼10 MW/cm2). The sign ofn2was determined from the direction of the fringe shift and was found to be negative. All‐optical switching (82 MHz) at a picosecond time scale is demonstrated for an organic material. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113225

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new mechanism for exciton lasing in ZnSe/ZnCdSe quantum wells is proposed. Lasing, occurring below the lowest exciton line, may be associated with a BCS‐like condensed (coherent) exciton state. This state is most stable at low temperatures for densities in the transition region separating the exciton Bose gas and the coherent exciton state. Calculations show the gain region to lie below the exciton line and to be separated from the absorption regime by a transparency region of width, for example, about 80 meV for a 90 A˚ ZnSe/Zn0.75Cd0.25Se quantum well. Experimental observation of the transparency region using differential spectroscopy would confirm this picture. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113226

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electroluminescence is obtained from nearly monodisperse CdSe nanocrystallites (quantum dots) incorporated into thin films (1000 A˚) of polyvinylcarbazole (PVK) and an oxadiazole derivative (t‐Bu‐PBD) and sandwiched between ITO and Al electrodes. The electroluminescence and photoluminescence spectra (bandwidths ≤40 nm) are nearly identical at room temperature and are tunable from ∼530 to ∼650 nm by varying the size of the dots. Voltage studies at 77 K indicate that while only the dots electroluminesce at the lower voltages, both the dots and the PVK matrix electroluminesce at higher applied voltages. Variable temperature studies indicate that the electroluminescence efficiency increases substantially as the films are cooled down to cryogenic temperatures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113227

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon samples were implanted with 20 keV He at various temperatures. The damage and the size of the He bubbles created during the implantation were measured with Raman spectroscopy and transmission electron microscopy. Room temperature implantation with 2.5×1017He atoms/ cm2produced an amorphized layer with a high density of small voids (∼5 nm). After annealing at 923 K the amorphous layer was recrystallized, but still contained extended defects. The He bubbles coalesced forming large bubbles in the implanted region. Implantation at 723 K left the Si essentially crystalline, but with a large number of defects. The He bubbles created at this temperature were larger than after room temperature implantation. Light emitting properties of this porous material are briefly discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113228

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Ion bombardment during plasma‐enhanced chemical vapor deposition of hydrocarbon films mainly governs the properties of the films. The range of this ion‐induced modification of the optical properties of hydrocarbon films was determinedinsituby monochromatic ellipsometry. The hydrocarbon films were deposited by an electron cyclotron resonance methane plasma onto silicon substrates and additional rf bias was applied to vary the kinetic energy of the impinging ions. The ion‐induced modification of the film properties was investigated by means of a double layer consisting of a polymerlike film with low optical absorption and a hard carbon film with high absorption on top. The deposition of this double layer was monitoredinsituby ellipsometry during the growth and during the erosion of this film system in an oxygen plasma at floating potential. From these data it is possible to determine with high accuracy the range of the ion‐induced modification of the optical properties. This layer ranges from 6 A˚ at 30 V dc self‐bias to 40 A˚ at 100 V dc self‐bias, which is consistent withTRIM.SPcalculations for the bombardment of polymerlike films by hydrogen ions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113229

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A procedure to pattern thin metal films on a nanometer scale with a scanning tunneling microscope (STM) operating in air is reported. A 30 nm film of hydrogenated amorphous silicon (a‐Si:H) is deposited on a 10 nm film of TaIr. Applying a negative voltage between the STM tip and thea‐Si:H film causes the local oxidation ofa‐Si:H. The oxide which is formed is used as a mask to wet etch the not‐oxidizeda‐Si:H and subsequently, the remaining pattern is transferred into the metal film by Ar ion milling. Metal wires as narrow as 40 nm have been fabricated. Sincea‐Si:H can be deposited in very thin layers on almost any substrate, the presented procedure can be applied to structure all kind of thin films on a nanometer scale. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113230

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Transmission electron microscopy was used to study the interfacial reactions and crystallographic structure in high‐temperature sputtered Al alloy/TiN system. An intermediate layer and semispherical precipitates were observed as the reaction products during high‐temperature sputtering at 500 °C. Electron diffraction analysis indicated that the intermediate layer consisted of hexagonal AlN and cubic TiN. Semispherical precipitates were also found to consist of tetragonal Al3Ti. Additional energy dispersive x‐ray spectrometer analysis suggested that the intermediate layer was formed by the diffusion of Al atoms into the TiN film. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113231

出版商:AIP    

年代:1995

数据来源: AIP