摘要:

A new, low cost, vibrating reed mechanical spectrometer has been developed. The setup consists of a pulse train generation system for capacitive excitation of the specimen in one of its flexural vibration modes and of a capacitive current measuring and amplification circuit for detection of the specimen oscillation. The used detection method is convenient for low damping levels (internal friction,Q−1≤0.02) and low vibration amplitudes (≤0.1 &mgr;m) only. The resonance frequency and the mechanical energy dissipation are derived by numerical analysis of the measured freely decaying vibrations. In terms of experimental performance several such analysis methods (Hilbert transformation method, zero‐transition method, nonlinear fitting) are evaluated. The system’s performance is illustrated with some informative examples.

ISSN:0034-6748    

DOI:10.1063/1.1144621

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

To image the orientational order in a broad class of biological and manufactured materials, a new microscope has been developed that integrates laser scanning microscopy with polarization modulation polarimetry. Polarimetry allows quantitative characterization of the molecular orientation and the degree of order through characterization of optical anisotropy. Combined with laser scanning microscopy, it is used here to image the anisotropy with high spatial resolution, sensitivity, and speed. The design of the microscope is presented; and the vast improvement in sensitivity achieved using PM‐LSM over conventional polarization microscopy is illustrated by imaging the linear dichroism of ultrathin Langmuir–Blodgett polymer films. PM‐LSM allows imaging of the magnitude and orientation of linear dichroism in films as thin as three molecular layers (∼66 A˚) at high resolution by rastering a diffraction limited spot of laser light across the sample. The rate of image acquisition is over 2000 pixels/s, two to three orders of magnitude faster than the previous methods of imaging optical anisotropy.

ISSN:0034-6748    

DOI:10.1063/1.1144622

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

In this article we demonstrate how to obtain the ultimate lateral resolution in surface plasmon microscopy (SPM) (diffraction limited by the objective). Surface plasmon decay lengths are determined theoretically and experimentally, for wavelengths ranging from 531 to 676 nm, and are in good agreement. Using these values we can determine for each particular situation which wavelength should be used to obtain an optimal lateral resolution, i.e., where the plasmon decay length does not limit the resolution anymore. However, there is a trade‐off between thickness resolution and lateral resolution in SPM. Because of the non‐optimal thickness resolution, we use several techniques to enhance the image acquisition and processing. Without these techniques the use of short wavelengths results in images where the contrast has vanished almost completely. In an example given, a 2.5 nm SiO2layer on a gold layer is imaged with a lateral resolution of 2 &mgr;m, and local reflectance curves are measured to determine the layer thickness. The SPM image is compared with an atomic force microscopy image of the same object. We obtain a 3 &mgr;m resolution when thickness differences within a lipid monolayer are imaged and measured.

ISSN:0034-6748    

DOI:10.1063/1.1144623

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

This article describes the construction and operation of a source of 2–5 keV argon atoms for use in the strong (1–7 T)B‐field environment of a photoelectron spectromicroscope. The velocity spread of the atom beam has been determined from the time of flight. Atom‐induced secondary‐electron yield measurements on selected areas of various metallic elemental samples are described and the results show that yields differ by up to a factor of 4×103between elements and trend towards lower yields with increasing atomic number. A number of ultraviolet photoelectron spectra of the fast‐atom sputter‐cleaned sample surfaces are also presented. These spectra are angle‐integrated over the full 2&pgr; of electron‐emission angles.

ISSN:0034-6748    

DOI:10.1063/1.1144624

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A microscanning electron microscope (SEM) column has been constructed as an attachment of an ultrahigh‐vacuum chamber with a 70 mm diam flange to observe microstructures on a solid surface. The micro‐SEM column is 26 mm diam and 140 mm long and operated in an energy range from 100 eV to 3 keV. It consists of a thermal‐field‐emission (TFE) gun and two magnetic lenses. The excitation of the objective lens for 3 kV electrons is 250 A T at a working distance of 10 mm. The saturated temperature of the objective lens at the excitation of 250 A T is approximately 50 °C and the vacuum of the chamber is 2×10−10Torr. The electron probe is adjustable against a specimen position from the outside of the vacuum by movement of the SEM column with screws. The spot size of the electron probe is 100 A˚ at 3 kV and 3000 A˚ at 300 eV in conditions of a working distance of 10 mm and a probe current of 3×10−11A.

ISSN:0034-6748    

DOI:10.1063/1.1144625

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A scanning tunneling microscope (STM) has been developed, dedicated for use on artificially fabricated nanostructures at low temperatures. With this STM mesoscopic phenomena can be studied, combining the unique possibilities of scanning tunneling microscopy and artificially fabricated nanostructures for investigating the physics in this regime. The STM is vibration insensitive, has reliable coarse approach mechanisms in three dimensions, and operates at low temperatures. In order to be able to position the tip above the structure of interest, also a searching strategy has been developed. In this article we describe design and operation of the STM and demonstrate searching.

ISSN:0034-6748    

DOI:10.1063/1.1144626

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An atomic force/scanning tunneling (AFM/STM) microscope intended for operation inside a scanning electron microscope (SEM) is described. This AFM/STM/SEM system enables us to image a sample conventionally by SEM as well as to investigate the local surface topography by AFM or STM. This device incorporates a new method for monitoring AFM cantilever deflection that utilizes the focused electron beam of the SEM.

ISSN:0034-6748    

DOI:10.1063/1.1144627

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A scanning tunneling microscope (STM) operable from room temperature to 1.5 K with an integrated sample preparation chamber has been constructed and successfully tested. Both the sample and the tunneling tip can be cleaned and/or modified in a UHV processing chamber which is connected at the top of a liquid‐helium flow cryostat. The STM is mounted to a threaded rod inside the cryostat so that it can be translated vertically. This allows a newly prepared sample/tip to be transferred onto the STM and lowered into a cryogenic environment without breaking vacuum, minimizing surface contamination which causes significant tunneling problems at cryogenic temperatures.

ISSN:0034-6748    

DOI:10.1063/1.1144628

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An analysis of two‐dimensional fast Fourier transform from images of periodical lattices (like highly oriented pyrolytic graphite) has been performed to understand and decouple the various parameters which account for distorted images in stylus microscopy. The effects of the various sources of image distortion have been described by means of linear maps and a mathematical approach has been developed to find the various correction coefficients resulting from the Fourier space analysis which restore the correct geometry of the images. Furthermore, the trend analysis of the distortion angle upon the scanning frequency shows the possibility of decoupling the role of ‘‘static’’ and ‘‘time dependent’’ distortion parameters. This possibility may be used for anaprioriprediction of possible distortions in stylus microscopy and thus for a real‐time correction of the images during scanning.

ISSN:0034-6748    

DOI:10.1063/1.1145207

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Geometrical distortions of scanning tunneling or atomic force microscope pictures can be caused by delayed response of the piezo‐ceramics and errors of the nonlinear feedback system. The images are adversely affected mostly at the boundaries where the tip motion is reversed and also at surface steps. Assuming logarithmic corrections for the time dependence of the piezo response and for the feedback nonlinearity, it is shown how these errors can be eliminated. The procedure is applied to three test samples: well‐ordered clean single‐crystal gold and copper surfaces, for which the correction parameters are determined as a function of temperature, scan velocity, and the place where the tips move into the scanned area. Gathering this information from various test samples, a data base can be built up that can be used to correct other samples recorded under the same conditions.  

ISSN:0034-6748    

DOI:10.1063/1.1144629

出版商:AIP    

年代:1994

数据来源: AIP