摘要:

The refractive index of fully strained Si1−xGexlayers, with compositionsx=0.20, 0.25, 0.30, and 0.33, has been measured using spectroscopic ellipsometry as a function of the wavelength in the 0.9–1.7 &mgr;m range. The dependence of the refractive index on the wavelength, for these compositions, is similar to that of crystalline Si. Its value for any wavelength is lower than that of relaxed Si1−xGexof the same composition. The experimental values of the refractive index of the fully strained Si1−xGexwere fitted to the expressionnSiGe(x,&lgr;)=nSi(&lgr;)+(1.16–0.26 &lgr;)x2. This expression is applicable for wavelengths from 0.9 to 1.7 &mgr;m and compositionsx≤0.33. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114907

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

TE/TM polarization mode switching is demonstrated in an AlGaAs/GaAs distributed feedback laser diode. The device has two current injecting electrodes and as an active layer a conventional multiquantum well (MQW) structure. A small amplitude modulation of the current into one of the electrodes switches the polarization mode. Each mode corresponds to a stable single longitudinal mode of a distributed feedback laser. The lasing wavelength can be tuned continuously, without mode hopping, over 0.7 nm by controlling the total injection current. This new kind of polarization switching is promising for optical switching systems and optical frequency division multiplexing devices. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114908

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The far field angular intensity distributionI(&thgr;) of the &lgr;=633 nm radiation transmitted through diffracting circular apertures is measured for diameters ranging between 60 and 500 nm. The circular apertures are located at the apex of aluminum coated tapered optical fiber tips.I(&thgr;) depends sensitively on the aperture diameters down to &lgr;/6. This property is used to determine the optical aperture size of metal coated tapered optical fiber tips used for near field scanning optical microscopy. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115262

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The piezoelectric strain coefficients have been measured as a function of composition for films in the PbZrO3–PbTiO3(PZT) solid solution system, using a double‐beam laser interferometry technique. This compositional dependence of piezoelectric, and the associated dielectric and ferroelectric properties for films 1 &mgr;m in thickness with varying Zr/Ti ratio, deposited on platinized silicon substrates using a modified sol‐gel route, corresponds to data reported for undoped PZT ceramics with respect to the effective morphotropic phase boundary composition. Films with composition near the morphotropic phase boundary, Pb(Zr0.52Ti0.48)O3, show enhanced values of the longitudinal piezoelectric coefficient, 194 pC/N; dielectric permittivity, 1310; and remanent polarization, 36 &mgr;C/cm2. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115263

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Hydrogenated single crystal (100) diamond surfaces subjected to an electrochemical (EC) treatment are selectively oxidized at room temperature. Part of the surface remains hydrogenated, except for a narrow transition region between the oxidized and hydrogenated regions. Ultraviolet photoelectron spectroscopy indicates that the transition region has negative electron affinity (NEA), as do the surfaces of hydrogenated crystals. The oxidized and hydrogenated parts of the EC‐treated surfaces do not have NEA. A possible explanation is that contaminants eliminate NEA in the hydrogenated parts of the EC treated surfaces, but the transition region remains uncontaminated. None of the oxidized surfaces exhibit NEA. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115264

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

X‐ray diffraction and dielectric measurement have been applied to investigate the phase transition and transport properties ofSr0.56C60O1.5which is obtained by the reaction ofSrCl2withC60anion aquatic solution. The new compound has a similar structure, but different transport properties as compared with metallic Sr‐doped C60. X‐ray diffraction shows that a first‐order phase transition around 100 °C is related to the rearrangement ofSr2+in the interstitial sites of the C60lattice. The step change of ac conductivity near 100 °C is also attributed to the hopping ofSr2+between interstitial sites. The ionic conductivity indicates the possibility of synthesizing superionic conductors based on C60and its derivatives. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115265

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the photodegradation of poly(p‐phenylenevinylene) polymer when the film was irradiated with laser light at a wavelength corresponding to the peak wavelength of electroluminescence. Degradation in photoluminescent properties was significant in an air environment but not under vacuum. This indicates that the oxygen in air aids photodegradation and this hypothesis was confirmed by optical spectroscopy. This degradation may be associated with long‐term stability of the electroluminescence device. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115266

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Er3+‐doped Ta2O5bulk gels were prepared via the sol‐gel process and characterized. In this heated gel, green upconversion fluorescence was observed around 545 nm under 805 nm excitation (4I15/2→4I9/2). Electron spin resonance (ESR) spectra for Er3+in the gels were also determined at 4.2 K. Remarkable features observed in upconversion fluorescence and in ESR were discussed on the basis of dispersion of Er3+ions in the Ta2O5gel. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115267

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Al films deposited on sputtered‐TiN/Si substrate by metalorganic chemical vapor deposition (MOCVD) from dimethylethylamine alane (DMEAA) were characterized using x‐ray diffraction (XRD), Auger electron spectroscopy (AES), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The TiN film sputtered on the Si has a preferred orientation along the growth direction with the ⟨111⟩ of the film parallel to the Si⟨111⟩. Sputtering of the TiN film on the Si induced strains at the interface. The TiN/Si interface is flat while the Al/TiN interface is rough. There exist many dislocations at the Al/TiN interface. The Al2O3phase was formed at the Al/TiN interface during the early stages of Al deposition. In the Al grains, there exist many tangled dislocations and a few Al2O3particles. With increasing deposition time, the Al film surface roughness increases. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115268

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nb/Cu multilayers grown by molecular beam epitaxy have been studied by x‐ray diffraction and atomic force microscopy. X‐ray diffraction provides the average interface roughness while atomic force microscopy shows the roughness and topology of the upper surface. Comparison of both methods shows that high‐angle diffraction averages over a lateral length which is in good agreement with the typical grain size. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115269

出版商:AIP    

年代:1995

数据来源: AIP