摘要:

Second‐harmonic generation in the proton‐exchanged LiTaO3waveguide is greatly enhanced by reducing the amount of proton exchange in fabricating the domain grating and the waveguide. To reduce the amount of proton exchange, a Ta‐SiO2mask is used for the periodic domain inversion and a SiO2mask for the proton‐exchanged waveguide. The fabricated device generates second‐harmonic blue light of 1 mW at 429 nm with the fundamental wave power of 10.3 mW. Its normalized efficiency is 1500 %/Wcm2, which is the highest value for LiTaO3waveguide devices reported to date. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115832

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The effect of dispersive, linear propagation (e.g., in single‐mode optical fiber) on the intensity noise from semiconductor lasers is investigated. Relations between the frequency and amplitude noise variations of semiconductor lasers are obtained from the laser rate equations and used to calculate the change in the relative intensity noise (RIN) spectrum that occurs during dispersive propagation. Propagation in fiber with positive dispersion (D≳0) over moderate distances (several km for standard single‐mode fiber at 1.55 &mgr;m) is found to reduce the RIN over a wide range of frequencies. Measurements with a 1.56 &mgr;m distributed feedback laser confirm the main theoretical results and demonstrate reductions in RIN of up to 11 dB with 4 km of standard fiber. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115833

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A methodology has been developed to achieve rapid two‐dimensional self‐consistent simulation of plasma transport and reaction in an inductively coupled source of arbitrary geometry and with arbitrary plasma and surface chemistries. In this modular finite element fluid simulation the reactor was divided into bulk plasma and sheath. The bulk plasma was assumed quasineutral and the electrons were assumed to be in Boltzmann equilibrium. Separate modules computed the power deposition into the plasma, electron temperature, charged species densities, and neutral species densities. Simulation results agreed favorably with available experimental data, taken in a chlorine plasma in a Gaseous Electronics Conference reference cell, without using any adjustable parameters. Rapid convergence makes the simulation tool especially attractive for technology computer‐aided design (TCAD) applications. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115834

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Hydrogen‐terminated vicinal Si(111) surfaces provide quasi‐van der Waals substrates with regularly spaced atomic height steps for the epitaxy of organic material films. Molecular beam epitaxy of vanadyl and copper phthalocyanines (VOPc and CuPc) was attempted on just‐cut and 7°‐miscut surfaces in order to investigate the effect of the steps on the epitaxial growth feature. The molecular arrangement of the films was characterized by a new technique using multiple‐azimuth reflection high energy electron diffraction. Growth on misoriented substrates producted VOPc monolayer films consisting of one‐dimensional chains nearly aligned to the steps and multilayer CuPc films with controlled domain orientations. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115835

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Characteristics of LaNiO3(LNO) thin films deposited by rf sputtering process were compared with that prepared by pulsed laser deposition (PLD) process. rf sputtered LNO films were [200] preferentially oriented with a low surface resistivity (&rgr;s=0.55 m&OHgr; cm) and the PLD deposited films were [110] predominated with a slightly larger surface resistivity (&rgr;s=6.38 m&OHgr; cm). Using Pt coating as underneath layer markedly reduced the surface resistivity (&rgr;s=0.05 m&OHgr; cm) without modifying the texture characteristics of the LNO layers. PLZT films subsequently deposited on LNO layers inherited the texture characteristics of the underlying LNO layers. Ferroelectric properties of PLZT films were optimized when using LNO–Pt double layers as bottom electrodes. The remanent polarization and coercive force obtained werePr=14.9 &mgr;C/cm2andEc=3.5 kV/cm, respectively. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115836

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The evolution of the tantalum/diamond interface upon room‐temperature Ta deposition on the (100) surface of a boron doped, synthetically grown diamond single crystal was monitored by Auger electron spectroscopy (AES), ionization loss spectroscopy (ILS), and electron energy loss spectroscopy (ELS). Characteristic loss peaks indicate carbide formation at the interface from very low coverages on, reflecting the strong interaction between tantalum and carbon. Thicker layers of TaC are formed during subsequent thermal annealing by diffusion of carbon into the tantalum film, at the same time the topmost diamond region is transformed into poorly ordered graphitic carbon. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115837

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Synthesis of Ge nanocrystals in SiO2films is carried out by precipitation from a supersaturated solid solution of Ge in SiO2made by Ge ion implantation. The films exhibit strong room‐temperature visible photoluminescence. The measured photoluminescence peak energy and lifetimes show poor correlations with nanocrystal size compared to calculations involving radiative recombination of quantum‐confined excitons in Ge quantum dots. In addition, the photoluminescence spectra and lifetime measurements show only a weak temperature dependence. These observations strongly suggest that the observed visible luminescence in our samples is not due to the radiative recombination of quantum‐confined excitons in Ge nanocrystals. Instead, observations of similar luminescence in Xe+‐implanted samples and reversible PL quenching by hydrogen or deuterium suggest that radiative defect centers in the SiO2matrix are responsible for the observed luminescence. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115838

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The initial stage of layer‐by‐layer sputtering of Si(111) surfaces with 500 eV Ar ions has been studied by using scanning reflection electron microscopy. At a moderate temperature of 900 K, vacancy islands are formed in the middle of wide terraces. At higher temperatures over 990 K, the atomic steps retreat as the ion dose is increased. The results show that layer‐by‐layer sputtering is characterized by vacancy creation caused by ion impact, and by thermally activated surface migration of vacancies. Moreover, the step area decorated by electron‐beam‐assisted carbon deposition acts as a step pinning site during the layer‐by‐layer sputtering. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115839

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A method for the bulk treatment of polymeric materials is proposed. Energetic ions created after capture of a neutron beam by constituent atoms located within the polymer can be used to cause radiation‐induced modifications such as cross linking in the polymer. In contrast to traditional ion implantation, the proposed method enables bulk treatment because of the relatively deep penetration of neutrons. Analytical estimates and Monte Carlo computations are performed for the10B(n,&agr;)7Li reaction for the cross linking and hydrogen depletion of boron‐doped polystyrene. Requirements for the polymer composition and microstructure, as well as potential synthesis methods are discussed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115840

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

15R polytype of diamond has been synthesized using a specially designed oxy‐acetylene flame system along with 3C diamond and cubic carbon on polycrystalline molybdenum substrates. X‐ray diffraction has been used to detect the 15R phase as the dominant phase in these films. Rapid changes in the substrate temperature during the growth process are expected to be responsible for the growth of these phases. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115841

出版商:AIP    

年代:1996

数据来源: AIP