摘要:

This article presents the construction and performance of a new type of temperature sensor, which can resolve temperature changes of the order of10−4 °C in the range of 0.1 °C. Measured with the new temperature sensor, the daily change of temperature in our underground laboratory is less than 0.0034 °C. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148244

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have tested two methods of compensating environmental disturbances applicable to high-temperature superconducting quantum interference device (SQUID) systems operating in magnetically unshielded environments. For testing, we used first- and second-order axial electronic gradiometer setups with rf SQUID magnetometers operating at 77 K and base lines between 7 and 8 cm. The magnetometers were single-layer washer rf SQUIDs with bulk or thin-film magnetic flux concentrators in flip-chip geometry. The tested methods resulted in disturbance compensation levels comparable to those attained using electronically formed gradiometers. The white noise of the compensated magnetometers resulted in13.5 fT/cm &sqrt;Hzfor first-order and 22 fT/cm2&sqrt;Hzfor second-order compensation down to a few Hz. Common mode rejection was balanced to better than 10 000 for homogeneous fields and better than 200 for gradient fields with second-order compensation. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148245

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A novel absolute displacement measurement by using a heterodyne interferometer, with a frequency-modulated laser diode has been successfully implemented. In this signal processing scheme, the synthesized modulation index of a phase-modulated interferometer is used for measuring the displacement, which is independent of the variation of the modulation frequency. The error induced from the intensity modulation in the laser diode can be eliminated. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148281

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We describe an aperture emission mode scanning near-field optical microscope (SNOM), optimized for material surface science applications. This instrument can be operated in both transmission and reflection configurations, in order to investigate transparent as well as opaque samples. It employs optical shear-force detection for tip/sample distance control, designed to minimize interference with the probe light. The SNOM head has been fully integrated on a homemade atomic force microscope platform and is placed in a controlled atmosphere chamber for reduction of surface contaminants. Within the compactness and the versatility obtained in our instrument, we have been able to optically discriminate different materials with a &lgr;/20 lateral resolution, and to distinguish polymeric aggregates, without damaging the surface, in spite of their rather poor optical contrast.©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148246

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An improvement to the currently used ac impedance detection method for tip-sample distance control in near-field scanning optical microscopes is described and demonstrated. The output signal of the electronic bridge is increased by a factor of 5000 so that a root-mean-square chip can be used in place of sensitive lock-in detection. It is shown that the signal-to-noise ratio of this new method is high enough to detect 0.07 nm changes in topography. In addition, this modification makes the electronics for the shear force feedback compact and inexpensive. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148247

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optical microscopy is an important measurement tool in many industries. This importance is primarily due to the ease-of-use and nondestructive characteristics of optical microscopes. Unfortunately, the far-field optics of conventional microscopes limit their resolution to approximately 200 nm. An imaging technique called near-field microscopy uses a subwavelength aperture to circumvent this limit to obtain images with enhanced resolution without many of the destructive consequences of other techniques. Visible microscopes based on this technique have produced images that demonstrate 10–15 nm resolution. This article describes the extension of these techniques to the infrared regime. A description of an infrared microscope capable of imaging the thermal emissions from micron scale conductors using optical techniques has been given. The microscope has been designed to operate in both the collection mode using an external infrared radiation source and in the self-illumination mode using thermally activated objects. Several infrared images of 2-&mgr;m-wide conductors have been provided to demonstrate the resolution capabilities of the microscope. These images clearly show the presence of the conductors and represent a significant increase in resolution over conventional infrared imaging devices. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148248

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A superior lamellae etching drop-off technique is described for the preparation ofWtips without the use ofCCl4.Sharp tips with an apex of 25 nm or less can be produced routinely. In the case of Pt/Ir wire, the chemical inertness of the material means that it has to be reduced in diameter before being etched to yield a tip. In order to accomplish this, a capillary diameter reduction technique has also been developed for use in combination with the lamellae etching drop-off technique. The apparatus does not require the use of micromanipulators or micromovers. The shapes of tips with apexes as small as 25 nm can be investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This low cost method of producing sharp tips scanning tunneling microscopy is very effective and it would probably be feasible to develop an automatic tip preparation with a little more technical effort. Since it is possible to produce well shapedWtips almost every time after acquiring a little skill, it is not usually necessary to check their shape by TEM or SEM before use. In contrast, the success rate with Pt/Ir tips is only up to 70&percent;, so that it is advisable to check their shapes by TEM. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148249

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A scanning tunneling microscope with a completely digital control is described which is able to determine in addition to the sample topography the local reactance of the surface by using a mathematical procedure. The new types of information allow a more detailed discussion of surface properties. The measurements were carried out at gold films on silicon wafers. On a plasma polymer gold composite surface typical reactance differences will be demonstrated. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148250

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The article describes the principles and current performance of a scanning Kelvin probe microscope for contact potential measurements with a lateral resolution on the 100 nm scale and a sensitivity in the millivolt range. Preliminary results are presented regarding the variation of the surface potential across charged grain boundaries in polycrystalline silicon. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148251

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A technique has been developed to enhance the resolution of an optical scanning microdensitometer. Phase shifting optics are used to obtain a signal with high resolution, but with a complex structure. This signal is subtracted from a reference signal to produce the equivalent of an isolated, very narrow, bright line. This line is then scanned across the specimen. Improvements in resolution of about a factor of 2, compared to a conventional optical system, have been observed at numerical apertures up to 0.55, without sacrificing either the working distance or the depth of focus. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148252

出版商:AIP    

年代:1997

数据来源: AIP