摘要:

The extraction of diffusion length and surface recombination velocity in a semiconductor with the use of an electron beam induced current line scan has traditionally been done by fitting the line scan into complicated theoretical equations. It was recently shown that a much simpler equation is sufficient for the extraction of diffusion length. The linearization coefficient is the only variable that is needed to be adjusted in the curve fitting process. However, complicated equations are still necessary for the extraction of surface recombination velocity. It is shown in this article that it is indeed possible to extract surface recombination velocity with a simple equation, using only one variable, the linearization coefficient. An intuitive feel for the reason behind the method was discussed. The accuracy of the method was verified with the use of three-dimensional computer simulation, and was found to be even slightly better than that of the best existing method. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148846

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A novel high-frequency electron spin resonance (ESR) spectrometer is described. The features are high sensitivity, a continuously tunable operating frequency of 40–60 GHz, a cylindrical cavity with a novel coupling scheme, and simultaneous detection of absorption and dispersion. A radio frequency coil can be integrated into the cavity for electron nuclear double resonance (ENDOR) experiments. ESR and ENDOR spectra of a test sample are presented in order to demonstrate in particular the scientific potential of a variable-frequency spectrometer. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148847

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A new high-pressure cell as useful equipment for a polarizing microscope is described. Measurements in a temperature range between−40and+270 °Cunder hydrostatic pressures up to 300 MPa allow for example the observation of polymer morphology and phase transitions. In addition to a documentation on video and photograph, respectively, the computer-controlled light intensity measurement offers the possibility of a quantitative analysis. Investigations on the phase diagram of poly(diethylsiloxane) have been carried out and show, that the transition temperature from mesophase to isotropic melt decreases with increasing pressure for pressures above 160 MPa. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148848

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Several analytical mass spectrometric and optical spectroscopic methods require a step during which a nonvolatile substance is desorbed by a laser pulse. It is, however, very difficult to use these methods for quantitative measurements because an accurate control over the amount desorbed by the laser pulse is generally not possible, especially when mixtures of several substances are used. We report a new fast and convenient sample preparation procedure that solves these problems. A solution of the analytes is mixed with a solution of poly(vinyl chloride) to obtain a homogeneous and vacuum-stable thin polymer membrane after the solvent has evaporated. Laser ablation is then performed directly from this membrane, allowing an accurate control of the amount of ablated analytes and excellent reproducibility. Quantitative laser desorption mass spectrometry over three orders of magnitude as well as optical spectroscopic measurements using this sample preparation method are demonstrated for polycyclic aromatic hydrocarbons. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148849

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A new sputtering device using a radio-frequency magnetron discharge with a rectangular hollow-shaped electrode has been developed for a low-pressure discharge (∼ a few mTorr). The spatial structures of the electron density, the etching rate of the target material (copper), and the deposition rate were measured in uniform and convex profiles of the externally applied magnetic field. The device realized the uniform use of the target material under the arrangement of the magnetic-field configuration. The resistivity of the deposited copper thin film was also obtained, which was found to be similar to that of conventional copper(∼10−8 &OHgr; m).©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148850

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This article reports on a new apparatus, called the laser double ablation reactor, for studies on the reactivity of clusters. Structure and operative principle of the apparatus were presented. With this apparatus reactions between manganese/carbon clusters and sulfur clusters, and between silver and sulfur clusters were studied. The experiments indicate that manganese/carbon clusters appear inert when they react with sulfur clusters, while for reactions between silver and sulfur clusters, the products[AgS4]+,[AgS8]+,[AgS12]+,and[AgS16]+,mainly are obtained. In comparison to the results obtained by Fourier transform ion cyclotron resonance, it shows that the new apparatus is very efficient for study on reactions between clusters. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148851

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An electrochemical cell has been developed forin situx-ray diffraction from a working electrode under clean conditions equivalent to ultrahigh vacuum conditions of5×10−10 mbar.The substrate crystals can be preparedex situand transferred into the cell under protection of ultrapure water within a few seconds. The oxygen level in the electrolyte is reduced by continuousN2flow to less than 0.2&percent; compared to that of a fresh electrolyte. This can be done while rotating the cell by 360° about the surface normal. The electrode potential is accurately measured at the position of the crystal using a Luggin capillary and a standard reference electrode. We demonstrate the performance of our cell byin situsynchrotron x-ray diffraction measurements on ultrathin Co layers electrodeposited on Cu(001) in an aqueousH2SO4/CoSO4solution. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148852

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The use ofpHpotentiometric measurements in titrimetric analysis is commonplace in chemical and biological systems. The methodology usually works well, but problems arise in chemical systems involving slow equilibrium processes. This article describes a microprocessor controlled system that measurespHduring the course of titration and will only allow the addition of titrant when there is no detectible drift inpHwith time. The apparatus described has been used in these laboratories for several years and is extremely stable and reliable. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148853

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Low-voltage operation of a plasma reactor for exhaust gas treatment has been performed by using a multipoint-to-plane geometry device at high frequency. The plasma was produced in a narrow gap by a dielectric barrier discharge of 2–3 kV at 50 kHz. The multipoint electrode has 585 points in the shape of a quadrangular pyramid with 30°. Nitrogen oxide (NOx) removal performance of the reactor was tested for an exhaust gas from a diesel engine generator (20 kV A). The NOx components have been removed with about 100&percent; efficiency of 0.3 mol/kW h from the exhaust gas with NOx concentration of 200 ppm. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148854

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The aim of this project was to construct a laboratory scale fluidized bed reactor that simulates the behavior of full scale municipal solid waste combustors. The design of this reactor is thoroughly described. The size of the laboratory scale fluidized bed reactor is 5 kW, which corresponds to a fuel-feeding rate of approximately 1 kg/h. The reactor system consists of four parts: a bed section, a freeboard section, a convector (postcombustion zone), and an air pollution control (APC) device system. The inside diameter of the reactor is 100 mm at the bed section and it widens to 200 mm in diameter in the freeboard section; the total height of the reactor is 1760 mm. The convector part consists of five identical sections; each section is 2700 mm long and has an inside diameter of 44.3 mm. The reactor is flexible regarding the placement and number of sampling ports. At the beginning of the first convector unit and at the end of each unit there are sampling ports for organic micropollutants (OMP). This makes it possible to study the composition of the flue gases at various residence times. Sampling ports for inorganic compounds and particulate matter are also placed in the convector section. All operating parameters, reactor temperatures, concentrations of CO,CO2,O2,SO2,NO, andNO2are continuously measured and stored at selected intervals for further evaluation. These unique features enable full control over the fuel feed, air flows, and air distribution as well as over the temperature profile. Elaborate details are provided regarding the configuration of the fuel-feeding systems, the fluidized bed, the convector section, and the APC device. This laboratory reactor enables detailed studies of the formation mechanisms of OMP, such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), poly-chlorinated biphenyls (PCBs), and polychlorinated benzenes (PCBzs). With this system formation mechanisms of OMP occurring in both the combustion and postcombustion zones can be studied. Other advantages are memory effect minimization and the reduction of experimental costs compared to full scale combustors. Comparison of the combustion parameters and emission data from this 5 kW laboratory scale reactor with full scale combustors shows good agreement regarding emission levels and PCDD/PCDF congener patterns. This indicates that the important formation and degradation reactions of OMP in the reactor are the same formation mechanisms as in full scale combustors. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148855

出版商:AIP    

年代:1998

数据来源: AIP