scholarly journals Shape of Field-Induced Nanostructures Formed by STM

2007 ◽  
Vol 2007 ◽  
pp. 1-5
Author(s):  
Subhashis Gangopadhyay ◽  
Asit Kumar Kar ◽  
Balbir Kumar Mathur
Keyword(s):  
Scanning Tunneling Microscope ◽  
Gold Film ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Novel Technique ◽  
Pit Formation ◽  
Material Surfaces ◽  
Tungsten Tip

Creation of controlled and reproducible nanostructures on material surfaces using scanning tunneling microscope is a novel technique, which can be used for a variety of applications. We have examined the shape of the nanostructures so formed on the gold film using tungsten tip and examined the formation parameters, which govern their shape and size. During our investigations it is found that the reproducibility of mound formation can reach up to 90%under optimum operating conditions, whereas the pit formation can be made with almost 100%reproducibility. Formation mechanism of such nanostructures is also discussed.

Effects of Gallium Arsenide Passivation on Scanning Tunneling Microscope Excited Luminescence

1995 ◽  
Vol 380 ◽  
Author(s):  
E. E. Reuter ◽  
S. Q. Gu ◽  
P. W. Bohn ◽  
J. F. Dorsten ◽  
G. C. Abeln ◽  
...  
Keyword(s):  
Luminescence Intensity ◽  
Scanning Tunneling Microscope ◽  
Sample Surface ◽  
Scanning Tunneling ◽  
Tunnel Current ◽  
Tunneling Microscope ◽  
Bias Pulse ◽  
Tungsten Tip ◽  
Excited Luminescence ◽  
Sample Distance

ABSTRACTAn ambient scanning tunneling microscope (STM) was used to excite luminescence in ptype epitaxial GaAs with four separate surface preparations: bare GaAs, Au layer, sulfurmonochloride layer, and one monolayer of octa-decyl-thiol. The STM with tungsten tip was operated at a constant tunnel current of 5 nA during a +1 V bias applied to the sample and the resulting tip to sample distance was fixed during a higher voltage bias pulse which excited luminescence. The luminescence intensity increased rapidly with increasing bias voltage for all passivation types with the octa-decyl-thiol passivation achieving the highest STM excited luminescence (STMEL) of 3500 photons/sec at 4 V bias. Above about 4 V the luminescence from the octa-decyl-thiol and sulfur-monochloride passivated samples fell off irreversibly, indicating that the sample surface had been modified. The Au passivated and unpassivated samples showed no such luminescence drop up to 4.8 V, the highest bias employed. Photoluminescence (PL) studies of the samples showed that PL intensities exhibited a weaker dependence upon passivation type than did STMEL intensities, a result consistent with the assertion that STMEL is more sensitive to the surface properties of the sample than is PL.

A Combined Scanning Tunneling Microscope-Quartz Crystal Microbalance Study of Heating and Wear at a Sliding Interface

2008 ◽  
Author(s):  
Benjamin D. Dawson ◽  
Jacqueline Krim
Keyword(s):  
Quartz Crystal Microbalance ◽  
Scanning Tunneling Microscope ◽  
Quartz Crystal ◽  
Scanning Tunneling ◽  
Asperity Contact ◽  
Complete Understanding ◽  
Complex Issue ◽  
Tunneling Microscope ◽  
Sliding Interface ◽  
Tungsten Tip

The unique capabilities resulting from combining a scanning tunneling microscope (STM) and a quartz crystal microbalance (QCM) have been used to characterize the heating and wear at the interface of a tungsten tip and Indium substrate with a change in the contact characteristics of the interface occurring for sufficient sliding speeds. The advantage of this system is the ability to probe heat rise from an asperity contact which will aide in developing a more complete understanding of the complex issue of heat generated via friction.

Scanning tunneling microscopy of E. coli RNA polymerase deposited onto an Au substrate by an electrochemical process

1991 ◽  
Vol 49 ◽  
pp. 378-379
Author(s):  
Rebecca W. Keller ◽  
Carlos Bustamante ◽  
David Bear
Keyword(s):  
Scanning Tunneling Microscope ◽  
Biological Sample ◽  
Substrate Surface ◽  
Electrochemical Process ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Tunneling Microscope ◽  
E Coli ◽  
Preparation Techniques

Under ideal conditions, the Scanning Tunneling Microscope (STM) can create atomic resolution images of different kinds of samples. The STM can also be operated in a variety of non-vacuum environments. Because of its potentially high resolution and flexibility of operation, it is now being applied to image biological systems. Several groups have communicated the imaging of double and single stranded DNA.However, reproducibility is still the main problem with most STM results on biological samples. One source of irreproducibility is unreliable sample preparation techniques. Traditional deposition methods used in electron microscopy, such as glow discharge and spreading techniques, do not appear to work with STM. It seems that these techniques do not fix the biological sample strongly enough to the substrate surface. There is now evidence that there are strong forces between the STM tip and the sample and, unless the sample is strongly bound to the surface, it can be swept aside by the tip.

STM of freeze-fracture replicas: Problems and promises

1993 ◽  
Vol 51 ◽  
pp. 68-69
Author(s):  
J. T. Woodward ◽  
J. A. N. Zasadzinski
Keyword(s):  
Scanning Tunneling Microscope ◽  
Organic Materials ◽  
Freeze Fracture ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Molecular Scale ◽  
Organic Surfaces ◽  
Metal Layers ◽  
Conductive Surfaces

The Scanning Tunneling Microscope (STM) offers exciting new ways of imaging surfaces of biological or organic materials with resolution to the sub-molecular scale. Rigid, conductive surfaces can readily be imaged with the STM with atomic resolution. Unfortunately, organic surfaces are neither sufficiently conductive or rigid enough to be examined directly with the STM. At present, nonconductive surfaces can be examined in two ways: 1) Using the AFM, which measures the deflection of a weak spring as it is dragged across the surface, or 2) coating or replicating non-conductive surfaces with metal layers so as to make them conductive, then imaging with the STM. However, we have found that the conventional freeze-fracture technique, while extremely useful for imaging bulk organic materials with STM, must be modified considerably for optimal use in the STM.

The atomic-force microscope and its future in biology

1993 ◽  
Vol 51 ◽  
pp. 704-705
Author(s):  
Jean-Paul Revel
Keyword(s):  
Silicon Nitride ◽  
Laser Beam ◽  
Atomic Force Microscope ◽  
Scanning Tunneling Microscope ◽  
Point Of View ◽  
Scanning Tunneling ◽  
Close Relative ◽  
Tunneling Microscope ◽  
Atomic Force ◽  
Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

FIELD ION MICROSCOPE AND ATOM-PROBE STUDIES OF SCANNING TUNNELING MICROSCOPE TIPS

1988 ◽  
Vol 49 (C6) ◽  
pp. C6-55-C6-59 ◽  
Author(s):  
O. NISHIKAWA ◽  
K. HATTORI ◽  
F. KATSUKI ◽  
M. TOMITORI
Keyword(s):  
Scanning Tunneling Microscope ◽  
Atom Probe ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Field Ion Microscope
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