摘要:

A compact(150 &mgr;m×150 &mgr;m),electrostatic actuator for out-of-plane(z)actuation of a probe tip has been designed, fabricated, and tested. Static deflections of±0.7 &mgr;mout of the plane of the substrate have been achieved. The device consists of a single crystal silicon tip on a torsional cantilever with out-of-plane interdigitated electrode capacitors. This cantilever and electrode design allows a wide range of stiffnesses, actuator force, and frequency response. Significant improvements in performance (larger tip displacement and increased sense capacitance) and a higher density of devices per unit area can be obtained as the minimum feature size decreases. Applications such as information storage, molecular manipulation, and nanolithography require high density, parallel arrays for reasonable throughput. To demonstrate the suitability of this device for use in such arrays, a12×12array of microelectromechanical probe tips with integrated actuators and capacitive sensors for scanning probe microscopy has been fabricated. The size of each array element is about 150 &mgr;m by 150 &mgr;m with a tip-to-tip spacing in the array of 200 &mgr;m. Given these dimensions, the packing density of the devices is about2500 units/cm2.©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148361

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have built a simple two-stage thermostat for measuring small-angle neutron scattering from liquids or solids in the vicinity of a phase transition. The thermostat was tested between 20 and 75 °C. The long-term temperature stability varies within ±0.2 and ±0.5 mK, depending on the set-point temperature. Positive and negative temperature steps of 0.5 mK and more can be obtained without overshoot. Small-angle neutron spectra from a binary ionic mixture in the critical domain are also reported. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148362

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A synchrotron x-ray diffraction method is presented for structural investigations of interfaces between low-Z substrates and heavier liquids. The method, similar to methods used in neutron scattering, is based on illuminating the interface through the solid substrate. The backgrounds arising from bulk scattering and the signal-to-background ratio are estimated and compared with experimental results. An ultrahigh vacuum (UHV) setup is described in which the atomic arrangement and roughness of clean interfaces can be studiedin situ. Our first results illustrate the possibilities for both out-of-plane and in-plane diffraction studies. The specular reflectivity of the Ga/diamond(111)-2×1 interface was measured for perpendicular momentum transfers up to 2.2Å−1. In an in-plane study of Ga/Si(111)-7×7 the in-plane structure factor of Ga liquid within a depth of∼50 Å was compared to the structure factor of the bulk liquid. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148380

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A film balance for the investigation of insoluble monolayers at the macroscopic oil–water interface is described. The design of the balance enables simultaneous surface tension and optical reflection measurements under well defined conditions. The oil-phase is contained within a quartz housing whose dimensions are optimized for imaging purposes. The performance of the apparatus is illustrated by the &pgr;,A-isotherm of a phospholipid and ellipsometric images of the morphology of the phospholipid dipolmitoyl-phosphatidyl-ethanolamine at the hexadecane–water interface. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148363

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present here the design of a novel and simple setup for measuring the thermal conductivity of thin films. This method is based on the well known principle of phase lag of a traveling thermal wave. In the present setup, the traveling thermal wave is generated in the thin film by irradiating its one edge by an infrared laser. The phase lag (&Dgr;&thgr;) between the excitation wave and the resulting thermal wave, at a variable distancedfrom the edge of the sample, is determined by measuring the deflection of another “probe-laser.” The thermal diffusivity is then directly calculated from the slope of the plot between &Dgr;&thgr; andd.This method offers an accuracy of better than ±5&percent;. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148364

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The new algorithm of the thermal conductivity and thermal diffusivity determination from the transient hot-wire method has been applied to measurements performed in several solid materials. The algorithm makes use of the exact formula for the temperature variations, instead of its simple, asymptotic form that has been employed earlier. In the process of the least-square optimization of the residual function three parameters are obtained; thermal conductivity, thermal diffusivity, and the initial temperature. Two different variants of the method are presented: the classical one with the power kept constant during the measurements and the newly introduced constant current technique. The latter one has an advantage of requiring simpler conditioning electronics, and can therefore be recommended in space applications. The results of data processing show that thermal conductivity can be reliably determined even from the nonasymptotic part of the temperature measurements. The determination of thermal diffusivity is more difficult and requires high quality temperature data from the whole measurement interval. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148365

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An innovative nanocalorimeter has been developed for measuring specific heats of thin films, multilayers (typical thickness: 1000 Å) and single crystals (mass: 1 &mgr;g) in the temperature range of 1.5–20 K. The addenda of the device are as small as 3 nJ/K at 4 K (0.5 nJ/K at 1.5 K), thus samples with a heat capacity of the order of nJ/K at 4 K can be measured. Heat capacity differences as a function of temperature or an external magnetic field (5 T) were determined with a resolution of&Dgr;C/C≃10−4.This way we have seen heat capacity variations of less than a pJ/K. We present as an example measurements on very smallMn12O12acetate single crystals and a measurement of a thin superconducting Pb layer. In the latter measurement we could evidence via specific heat a finite size effect. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148366

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A description of a fully automated calorimeter for rapid measuring the heat capacity of solids in the temperature region from∼3to∼350 Kand in magnetic fields from 0 to 10 T is given. A comprehensive mathematical analysis of the semiadiabatic heat pulse technique for heat capacity measurements on solid materials resulted in the development of the necessary formal algorithms for the complete automatization of the data collection process. Simultaneously a procedure for the on-line evaluation of uncertainties in the measured heat capacity data is developed. An approach which eliminates the need for a separate temperature sensor(s) attached to an adiabatic heat shield(s) used to maintain semiadiabatic conditions during heat pulse heat capacity measurements has been proposed and tested. The sensorless technique provides reliable control of the heat transfer inside a vacuum chamber and results in accurate heat capacity data. The calibration results show that the heat capacity can be measured with an average accuracy better than 1&percent; on small samples(∼1 g)over the whole temperature region. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148367

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

By the use of a gold-plated silver sample holder, and aRuO2-Cernox combination thermometer, low-temperature specific-heat measurements in the temperature range from 0.35 to 90 K, and in magnetic fields up to 17.5 T, have become possible with remarkably improved accuracy. At 500 mK, the lower limit for the heat capacity that can be measured amounts to 0.02 mJ/K. The sensitivity in that case is about 0.3 &mgr;J/K. The error margin is 1&percent; for large heat capacities (larger than twice the sample-holder contribution) at higher temperatures, increasing to 3&percent; for small heat capacities (half of the sample-holder contribution) around 500 mK. In high fields, for accurate measurements (error <3&percent;) the temperature range is restricted to above 0.5 K. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148383

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The magnetic susceptibility,&khgr;=∂M/∂H,can be determined for ultrathin films using the surface magneto-optic Kerr effect and an ac technique (ac-MOKE) where the response to a small, modulatedHfield is measured. Optimization of the signal-to-noise ratio is imperative if the measurements are to be used to extract critical scaling exponents from the small tail of &khgr; in the paramagnetic region. These optimal conditions are different than those appropriate for more conventional staticHmeasurements (dc-MOKE) used to generate magnetic hysteresis loops, because the relative noise contributions from the laser stability, sample stability, and detector are changed. A simple method for determining optimum conditions is demonstrated, and the technique is used to show that a 1.8 ML Fe/W(110) film has the critical exponent &ggr; of the 2D Ising model. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148368

出版商:AIP    

年代:1997

数据来源: AIP