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.

Mono-Atomic Tips and Scanning Tunneling Microscopy

1986 ◽  
Vol 44 ◽  
pp. 762-763
Author(s):  
H.-W. Fink
Keyword(s):  
Scanning Tunneling Microscope ◽  
Sample Surface ◽  
Solid Surfaces ◽  
Scanning Tunneling ◽  
Detailed Structure ◽  
Tunneling Microscopy ◽  
Tunnel Current ◽  
Basic Principles ◽  
Tunneling Microscope ◽  
Distance Dependence

The power of the Scanning Tunneling Microscope (STM) to resolve the detailed structure of solid surfaces is based on the strong distance dependence of the tunnel current, while the tip is scanned over the surface to be investigated.In the first part of the paper, the basic principles of operation of the STM are to be reviewed, and examples of the information that can be obtained today are presented. From this, it will be evident that knowledge of the atomic arrangement of the tip is important in order to separate tunnel-current changes related to the tip from those owing to the structure of interest, namely, the sample surface.

A two-spring model of the tip-sample interaction using the Scanning Tunneling Microscope in air

1991 ◽  
Vol 49 ◽  
pp. 382-383
Author(s):  
John T. Woodward
Keyword(s):  
Liquid Bridge ◽  
Scanning Tunneling Microscope ◽  
Freeze Fracture ◽  
Tunneling Current ◽  
Sample Surface ◽  
Scanning Tunneling ◽  
Weakly Bound ◽  
Electrically Conductive ◽  
Tunneling Microscope ◽  
Piezoelectric Drive

The scanning tunneling microscope (STM) is capable of imaging surface features of electrically conductive samples with lateral resolution of 2 Angstroms and vertical resolution of 0.1 Angstroms. This is accomplished by rastering a conducting tip just above the sample surface using a piezoelectric drive. The tunneling current between the tip and the sample, which depends on the distance separating the two, is then used to keep the tip a constant distance above the sample and generate a height plot of the surface.When an STM is used in air, a small liquid bridge can be formed between the scanning tip and the sample as shown in Fig. 1, This bridge results from any fluid contamination on the surfaces along with condensation of primarily water from the air. For most applications of the STM, this liquid bridge has little effect on the image. However if the sample is somewhat flexible or only weakly bound on the STM base, as is the case for freeze fracture replicas, the forces exerted by the liquid bridge on the sample as the tip scans the surface can significantly alter measured heights from their actual values.

Antimony Cluster Manipulation on the Si(001) Surface by Means of STM

1996 ◽  
Vol 448 ◽  
Author(s):  
I.I. Kravchenko ◽  
C.T. Salling ◽  
M.G. Lagally
Keyword(s):  
Success Rate ◽  
Scanning Tunneling Microscope ◽  
Sample Surface ◽  
Pulse Voltage ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Sample Separation

AbstractWe present results of the manipulation of antimony clusters on Si(001) by means of a scanning tunneling microscope. By adjusting tip-sample separation and pulse voltage, an antimony cluster can be removed from the sample surface without damaging it. The success rate of the removed-cluster redeposition from the tip back onto the surface is 30%. In the remainder of the attempts a square shaped structure is created that had a hillock in the center. The hillock exhibits a metallic-like I-V curve. Such a structure cannot be created without an Sb cluster previously removed from the surface and located on the tip.

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.

Investigation On Laser-Induced Effects In Nanostructure Fabrication With Laser-Irradiated Scanning Tunneling Microscope Tips in Air Ambient

2000 ◽  
Vol 617 ◽  
Author(s):  
Z. H. Mai ◽  
Y. F. Lu ◽  
W. D. Song ◽  
W. K. Chim
Keyword(s):  
Thermal Expansion ◽  
Scanning Tunneling Microscope ◽  
Scanning Tunneling ◽  
Gold Films ◽  
Primary Reason ◽  
Nanostructure Fabrication ◽  
Tunneling Microscope ◽  
The Relationship ◽  
Kinetics Of ◽  
Sample Distance

AbstractIn this paper, we report our investigation on the kinetics of nanostructure fabrication on gold films and on H-passivated Ge surfaces. The relationship between the current and the tip-sample distance of the STM junction was measured for both gold films and H-passivated Ge surfaces. The tip-sample distance for gold films under a electrochemically etched W tip is approximately 2 nm, while that for H-passivated Ge sufaces is more than 27 nm. The thermal expansion length of the tip under laser irradiation was calculated. From the comparison of the thermal expansion length and the tip-sample distance, we can reach the conclusion that for gold films, thermal mechanical indention is the primary reason of nanostructure formation, while for H-passivated Ge surfaces, optical enhancement is the only reason.

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.

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