摘要:

Bi(111) films grown on mica substrates and then exposed to air have been imaged with an atomic force miroscope in 0.01 M HCl. By exposing the Bi(111) to air, layers of Bi oxide are readily formed, which can be removed by imaging in HCl. The images are atomically resolved and show two types of structure: large epitaxial areas of hexagonal structure with a spacing of 7.6 Å, and a few smaller regions with a spacing of 4.5 Å. The former agrees well with the (√3×√3)R30° structure of an overlayer of atomic oxygen atoms adsorbed on Bi(111), and the latter with the uncovered Bi(111) surface.

ISSN:0734-211X    

DOI:10.1116/1.585190

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Wear marks and frictional force distribution on amorphous carbon films, fluorinated amorphous carbon films, silicon‐containing amorphous carbon films, and fluorinated silicon‐containing amorphous carbon films were investigated by point contact microscopy. Film surfaces were also analyzed by x‐ray photoelectron spectroscopy. The fluorinated silicon‐containing (40%) amorphous carbon film has the highest strength of the tested films. CF4plasma treatment fluorinated the silicon‐containing (40%) amorphous carbon film, and significantly reduced its frictional coefficient to less than 0.3. The surface of fluorinated silicon‐containing (40%) amorphous carbon film is composed of carbon, silicon, fluorine, and oxygen. Carbon, silicon, and fluorine show the plural chemical states of SiC and CFx. This increases film strength and enhances the lubricating effect of the fluorinated silicon‐containing (40%) amorphous carbon film.

ISSN:0734-211X    

DOI:10.1116/1.585191

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We have made simultaneous measurements of the tunnel current and the force of interaction as a gold‐coated cantilever approaches towards and recedes from a gold sample in atmosphere. We will describe the effects arising from the surface contaminant layer. We also have made an estimation of the minimum value of the contact (repulsive) force that should be present for tunneling between gold and gold in air to be observed.

ISSN:0734-211X    

DOI:10.1116/1.585192

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The quality factor and frequency of vibration of a quartz crystal oscillator decreases slightly when a film adsorbs on its surface. Simultaneous measurements of the shifts in quality factor and frequency allow one to quantitatively deduce the degree to which the film ‘‘slips’’ due to the oscillatory motion of the underlying substrate, and also the force which would be required to slide the film along the surface at constant speed. Experiments have been carried out for krypton monolayers undergoing solidification on a smooth gold surface and on an atomically rough silver surface. The force per unit area required to slide a liquid monolayer is roughly the same for each surface. Less force is required to slide a solid monolayer along the smooth surface, while the opposite is true for the rough surface.

ISSN:0734-211X    

DOI:10.1116/1.585193

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The effect of compressive and shear forces between tip and surface during the operation of the scanning tunneling microscope (STM) is illustrated with examples obtained both in air and vacuum environments. We show that at typical gap resistances used in STM (≤20 GΩ) these forces can have significant effects. Compressive or repulsive forces give rise to anomalous topographic corrugations (elastic deformations) as well as to permanent damage (inelastic or plastic deformation). These forces also cause the anomalously low values obtained in measurements of the tunneling barrier height. The effects of shear forces when imaging weakly bound material will also be demonstrated.

ISSN:0734-211X    

DOI:10.1116/1.585194

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We have developed a batch process for the microfabrication of silicon force sensors. A force sensor typically consists of a tip mounted onto a cantilever which is connected to a handling piece. The sensors are being used as microprobes and force transducers in scanning force microscopes. Our sensors are etched from single crystal silicon. The process, which mainly involves a combination of wet and dry etching techniques, results in cantilevers and tips suitable as general purpose force sensors. The newly developed batch microfabrication process is superior to the process which uses wet etching of individual metal wires and it differs substantially from the known process to produce thin film cantilevers with and without integrated tips. The sensors have been applied in various microscopes, and with different types of operation including the repulsive, attractive, and magnetic force mode.

ISSN:0734-211X    

DOI:10.1116/1.585195

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Scanning force microscopy (SFM), operated in the attractive imaging mode, enables the precise measurement of the force between tip and sample over a tip–sample distance ranging from contact to tens of nanometers. The basic long range interactions (>1 nm: i.e., hydrodynamic, electrostatic, van der Waals, and capillary forces) between tip and sample have been measured and will be discussed. Each force leads to a different mode of operation in profiling samples. The most critical part of the SFM is the force sensor. Exact knowledge of the sensor properties is required for the interpretation of SFM measurements. We have used micromachined silicon sensors consisting of a monolithic silicon cantilever with integrated silicon tip and have performed a detailed characterization of the tip geometry and resonance properties. Examples of surface images on different samples (conductors, insulators and biological materials) and structures, ranging from atomic steps up to several microns high features, have been investigated to demonstrate capabilities and problems in SFM imaging.

ISSN:0734-211X    

DOI:10.1116/1.585196

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Displacement transducers based upon quantum mechanical tunneling of electrons can potentially achieve a sensitivity far superior to conventional transducers. The reason for this is that the dynamical influence of the tunneling transducer on a test mass is insignificant compared to that of traditional capacitive, inductive or piezoelectric transducers. Thus the fluctuating ‘‘back action’’ force from electrical noise in the tunneling transducer is nearly eliminated. The ‘‘back action’’ force becomes dominant as the test mass is miniaturized, thus the tunneling transducer may be especially useful in micro‐fabricated sensors. In this paper we present an equivalent circuit model for a tunneling transducer including noise and outline a method for calculating the minimum detectable signal in any given application. We also discuss some practical limits for tunneling‐based sensors.

ISSN:0734-211X    

DOI:10.1116/1.585197

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A scanning tunneling microscope (STM), operated in vacuum in the field emission mode, has been used to observe the latent image written with a focussed 50 kVe‐beam in a polydiacetylene negative resist. The ability to study the latent image in the undeveloped resist allows the resolution degradation caused by the exposure process to be separated from that occurring during the resist development step. The minimum linewidth observed in the resist is close to 80 nm in both the developed and undeveloped resist. This linewidth is significantly greater than that expected on the basis of the 50 kVe‐beam probe size, electron scattering, and secondary electrons. The results indicate that the resolution degradation occurs during the exposure process rather than during post‐exposure processing. This implies that swelling during development is not the critical problem it is with other negative resists. The quality and accuracy of the STM observations is discussed together with descriptions of related surface modifications createdinsituwith the STM.

ISSN:0734-211X    

DOI:10.1116/1.585198

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We have developed a technique to write nanometer‐scale features on surfaces. The technique combines two of the most advanced technologies: the laser and the scanning tunneling microscope (STM). Laser radiation is used to break the chemical bonds of trimethylaluminum to free aluminum atoms in the region of the tunneling gap of the STM. The atoms are subsequently selectively excited and ionized. The ions are then driven softly toward the surface where they are deposited by the field in the tunneling gap of the microscope. Since the field of the tip can be confined to a few nanometers, the writing can be controlled with such resolution. The technique is also capable of filling holes and addressable nondestructive erasing.

ISSN:0734-211X    

DOI:10.1116/1.585199

出版商:American Vacuum Society    

年代:1991

数据来源: AIP