摘要:

Theoretical analysis of surface‐emitting complex‐coupled distributed‐feedback (SE‐CC‐DFB) lasers with a second‐order grating reveals that operation in a single‐lobed, orthonormal beam can be fundamentally favored. This happens when the modal‐gain difference between symmetric and antisymmetric modes due to the optical‐field (longitudinal) overlap with the gain/loss grating overcomes the modal‐gain difference based on radiation losses. The analysis is performed for a simple three‐layer structure with gain placed in the high‐index regions (i.e., in‐phase, second‐order CC‐DFB). Lasing at or near the Bragg frequency provides essentially uniform near‐field patterns, thus immunizing the device to gain spatial hole burning. The results and their implications are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114592

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We show that the photoinduced defect population growth of an optically thick film may have stretched exponential time dependence if the defect does not decay nor diffuse within the time scale of the experiment. After the formulation of this simple model, low‐temperature photoinduced absorption of polyaniline is described as an example. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114593

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Simultaneous irradiation of multiwavelength beams emitted from a vacuum‐ultraviolet (VUV) Raman laser offers great potential for high‐quality microfabrication of fused quartz by ablation. In this process, short wavelength components of the beam play two roles, that is, stationary effect and transitional effect. The stationary effect means photodissociation of Si–O bonds and formation of metastable absorption sites to the longer wavelength beam components. The transitional effect increases the absorption to the fundamental beam with a 266 nm wavelength from 0% to more than 60%. This phenomenon may be explained as the excited‐state absorption (ESA) due to the coupling of the VUV laser beams with the fundamental beam. The mechanism of the high‐quality ablation is discussed by making a comparison between these two effects. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114594

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The valence band offsets at the heterointerfaces of the CdF2/CaF2/Si(111) structure grown by molecular beam epitaxy were evaluated using x‐ray photoelectron spectroscopy, and the energy band diagram of this heterostructure was proposed. It was found that the interface of CdF2/CaF2has large conduction band offset: 2.9 eV, and the energy level of CdF2conduction band edge is below that of Si. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114595

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Differential scanning calorimetry was used to characterize the energetics and kinetics of interdiffusion in solder/metal diffusion couples. The heat of formation of Cu3Sn from Cu6Sn5and Cu thin films was found to be &Dgr;Hr=−4.3±0.3 kJ/mol, similar to the results of previous measurements on bulk samples. We have seen that the nucleation of Cu3Sn begins at temperatures near 360 K, but that the nucleation and initial growth of Cu3Sn is not a well‐defined Arrhenius process in these diffusion couples. Later portions of our differential scanning calorimetry scans were identified with diffusion‐limited growth of Cu3Sn. From these calorimetry data we have estimated the averaged interdiffusion coefficient,D˜(cm2/s)=D0 exp (−E/kbT), wherekbis Boltzmann’s constant andD0=3.2×10−2cm2/s andE=0.87 eV/atom. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114596

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

To study the incorporation of nitrogen, diamond films were prepared by chemical vapor deposition homoepitaxially on {100} and {111} oriented diamond substrates. 50 ppm of isotopic15N2was added to the process gas. Nuclear reaction analysis was applied to determine quantitatively the concentration of incorporated15N. The analysis is based on the detection of the 4.44 MeV &ggr;‐radiation of the15N(p,&agr;1&ggr;)12C reaction. By a proper suppression of the &ggr;‐background, a sensitivity of better than 0.5 ppm can be achieved. The measurements reveal a preferred incorporation of nitrogen into {111} growth sectors, the15N concentration in {111} growth sectors is by a factor of 3–4 larger than in the {100} growth sectors. The N/C ratios in the films were found to be in the ppm regime and four orders of magnitude below the N/C ratios in the gas phase. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114788

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Carbon nitride thin films have been successfully grown on nickel substrates by a novel arc‐plasma jet chemical vapor deposition. These films were characterized by Auger electron spectroscopy, transmission electron microscopy, and Raman spectroscopy. Small grains (∼0.1 &mgr;m) as well as nanocrystallites found in the films were identified to be &bgr;‐C3N4. Raman spectroscopy also confirmed the existence of &bgr;‐C3N4phase in the films through five pronounced Raman bands as expected from the Hooke’s law approximation based on the vibrational frequencies obtained in analogous compound, &bgr;‐Si3N4. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114789

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The morphological instability of copper germanide (Cu3Ge) films in contact with amorphous germanium is reported. Through secondary ion mass spectrometry, x‐ray diffraction, transmission electron microscopy, and electrical measurements, the breakdown of the continuous layer has been monitored. On the contrary, with Cu3Ge in contact with single crystal germanium, no instability is observed at the same temperature. The crystallization of the amorphous germanium appears to be the mechanism responsible for the instability. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114790

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This letter presents a simple, quick, nondestructive method for the determination of ordering in Ga0.51In0.49P layers using x‐ray diffractometry. The skew, symmetric arrangement of x‐ray reflection was used for this purpose enabling the measurements of all allowed (hkl) reflections. Ordered Ga0.51In0.49P layers grown by metalorganic vapor‐phase epitaxy at different substrate temperatures were studied. The {1/2,1/2,1/2}, {1/2,1/2,3/2}, and {1/2,1/2,5/2} reflections of the ordering‐induced monolayer superlattices have been observed. The experimental results are discussed in detail, demonstrating that x‐ray diffractometry is a powerful means to evaluate ordering in semiconductors. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114791

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Grey tracks produced in KTiOPO4(KTP) by applying a dc electric field have been studied through optical absorption, Raman scattering, and synchrotron x‐ray topography. A study of the optical absorption and Raman scattering from the grey‐tracked region suggests that their formation is accompanied by changes in the electronic levels of Ti4+. There is no evidence for a major structural change or disorder in the grey‐tracked region. However, the x‐ray topographs do indicate the presence of a remnant strain in the lattice, which might contribute to the observed changes in the Raman intensities. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114792

出版商:AIP    

年代:1995

数据来源: AIP