Fast scanning tunneling microscope in constant current mode

1989 ◽  
Vol 333 (4-5) ◽  
pp. 340-342 ◽  
Author(s):  
S. Bräuer ◽  
B. Krämer ◽  
H. Pagnia ◽  
N. Sotnik ◽  
K. -H. Vetter ◽  
...  
Keyword(s):  
Scanning Tunneling Microscope ◽  
Current Mode ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Constant Current Mode

TUNNELING SPECTROSCOPY OF NANOMETER-SIZE CLUSTERS DEPOSITED ON GRAPHITE

1996 ◽  
Vol 03 (01) ◽  
pp. 979-982 ◽  
Author(s):  
A. WAWRO ◽  
A. KASUYA ◽  
R. CZAJKA ◽  
Y. NISHINA
Keyword(s):  
Scanning Tunneling Microscope ◽  
Electronic Structures ◽  
Energy Gap ◽  
Current Mode ◽  
Constant Current ◽  
Vacuum System ◽  
Graphite Substrate ◽  
Scanning Tunneling ◽  
Nanometer Size ◽  
Au Clusters

The electronic structures of Sb, Ni, and Au clusters of nanometer size are discussed. Clusters were deposited on a graphite substrate and analyzed with a scanning tunneling microscope in an ultrahigh-vacuum system. Scanning at constant-current mode at different bias voltages was used as a method of spectroscopic measurements. Disappearing of the clusters images at certain range of voltage biases is attributed to occurrence of the energy gap in electronic structure of clusters, suggesting their nonmetallic behavior.

Scanning tunneling microscopy of planar biomembranes

1989 ◽  
Vol 47 ◽  
pp. 14-15
Author(s):  
K. A. Fisher ◽  
S. Whitfield ◽  
R. E. Thomson ◽  
K. Yanagimoto ◽  
M. Gustafsson ◽  
...  
Keyword(s):  
Scanning Tunneling Microscope ◽  
Surface Deformation ◽  
Pyrolytic Graphite ◽  
Current Mode ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Biological Macromolecules ◽  
Tunneling Microscopy ◽  
Aspect Ratios ◽  
Planar Membranes

The scanning tunneling microscope (STM) is capable of imaging conductive surfaces at atomic resolution. When STMs are used to image biological samples, however, STM resolution is limited to nanometer levels whether samples are hydrated, air-dried, or metal-coated. Lateral resolution is poor due to the nature of biological macromolecules (large Image aspect ratios) as well as to STM tip effects (shape, multiple tips, and tip/sample Interactions). If samples are adsorbed to highly-oriented pyrolytic graphite (HOPG) surfaces and scanned in the topographic (constant current) mode, vertical resolution is also uncertain due to contamination-mediated surface deformation artifacts. Nevertheless, because the STM is capable of detecting sub-Ångstrom displacements in z (e.g. to 0.02 Å in UHV), we have examined the feasibility of using the STM to determine the thickness of planar membranes attached to glass and mica surfaces. Planar membrane monolayers also uniquely provide the opportunity to correlate biochemical and TEM information with STM topographic images.

Scanning tunneling microscope/scanning tunneling spectroscopy investigation of the structural modulation on the surface of cleaved Bi2Sr2CaCu2Oy, single crystal

1995 ◽  
Vol 10 (4) ◽  
pp. 817-822 ◽  
Author(s):  
Wu Ting ◽  
R. Itti ◽  
Y. Ishimaru ◽  
G. Gu ◽  
Y. Enomoto ◽  
...  
Keyword(s):  
Single Crystals ◽  
Scanning Tunneling Microscope ◽  
Current Mode ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Electronic Density ◽  
Tunneling Microscope ◽  
Structural Modulation ◽  
Stm Images

The surface of cleaved Bi2Sr2 CaCu2O3 (Bi2212) single crystals has been studied by means of scanning tunneling microscope (STM) and scanning tunneling spectroscopy (STS) at room temperature in ultrahigh vacuum. We obtain atomic images of the BiO surface using logarithmic current mode and conventional mode. It is demonstrated that the Bi atoms in the BiO plane are not missing. Some Bi atoms are depressed down below the BiO surface. STS obtained at different places of the surface shows more or less the same feature, indicating that local electronic density of states does not change much due to the depression or the well-known structural modulation. The possible origins of the variation in the period of the structural modulation in the BiO plane of cleaved Bi2212 single crystals extracted from STM images are also studied.

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.

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