Applications Of Stm Sfm Beyond Imaging Biology Essay


In Scanning Tunneling Microscopy , the electron charge is used as information carrier in the imaging process. Scanning Tunneling Microscopy have revolutionized the real space imaging of molecules[1], providing a detailed understanding of the ways in which they interact with each other and with the adsorbent which allows us to understand their nucleation and growth, their electronic coupling to the surface and their chemical activity. In Scanning Tunneling Microscopy (STM), the small tunneling current between the tip and the conductive surface is being used as the feedback parameter to move the tip and to also image the surface with up to an atomic resolution. Scanning Tunneling Microscopy (STM) is used to measure the tunneling current which contains information about electron transfer through water layers which is extremely important for mostly all electro chemical processes. The tunneling current also contains important information about the electronic states of absorbed molecules, which could be used to identify and also study the reactivity of the molecules. Scanning Tunneling Microscopy (STM) can also be used to create nanostructures

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In Scanning Force Microscopy (SFM), which is also known as the atomic force microscope (AFM) is a high resolution imaging tool which is used to probe and manipulate matter at forces and length scales which controls the molecular structures and molecular interactions.

Scanning Force Microscopy (SFM) can be applied in biological sciences, insulators tips or oxidized Silicon (Si) and metal tips are employed. Application of STM/SFM which is non-contact where conducting tips interact with the thin polar films grown on the metal substrates.

Scanning Tunneling Microscopy (STM) can be applied in electrochemistry and also on individual molecules on the temperature of pyrolysis. This first involves the direct photolithographic patterning of metal containing photo resist; follow the removal of the poly matrix and reduction of metal oxide which allows the growth of aligned carbon nanofibres/nanotubes by the pyrolysis of hydrocarbons such as acetylene in which a film-type mask is produced in the process.

In conclusion, the experiment result showed that the catalyst particle site and density as well as the pyrolysis temperature play an important role in the alignment of the carbon nanofibre/nanotubes.


In the combined application of Scanning Tunneling Microscopy and non-contact Scanning Force Microscopy (NC-SFM) [2], the conducting tips interact with the thin polar films grown on the surface of the metal substrates or with the conducting oxides [3].

This implies that the interaction of the tip with the film and of the film with the substrate involves the image force and it must be taken into consideration in the analysis and interpretation of Scanning Force Microscopy images. The combined application of Scanning Tunneling Microscopy and non- contact Scanning Force Microscopy (NC-SFM) gives the same result with combined application of Scanning Tunneling Microscopy and contact mode imaging [4-6].

Experiment shows that in non-contact Scanning Force Microscopy (NC-SFM), the cantilever is driven with a constant frequency of 100-200KHZ and oscillates with an amplitude of around 100-200Å above the surface [6, 7]. The tip-surface interaction affects the main frequency of the cantilever oscillations to change when the end of the tip approaches the sample. The map of displacement of the base of the cantilever needed to maintain a constant frequency change as the tip scans the surface in which the surface image is formed. In the moving away of the displacements from the surface bright and those towards its dark where an image contrast is formed. It also shows that, in the attractive region of the tip-surface interaction close to the surface, the most stable image is formed.

Experiment [7] shows that for stable imaging to be formed, [8] the distance between the tip end and the surface atoms must be larger than about 4-5Å. in some cases the tip crashes into the surface many times during one series of experiment[9]but it is very rare for the tip structure to change during one image so the structure of the tip apex is dependent on vacuum conditions, the tip preparation and it also depends on the stability of imaging. In Scanning Force Microscopy, the metallic or doped silicon (Si) tips used in carrying out the experiments are either covered by islands of a native oxide or covered by the surface material.

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In this experiment a relative importance of image forces in non-contact Scanning Force Microscopy (NC-SFM) contrast formation was used, i.e. a finite cluster of Nacl absorbed on a metallic substrate. In case of Scanning Tunneling Microscopy (STM) [10] and non-contact Scanning Force Microscopy (NC-SFM) experiment [10, 11], an insulating film grows on a metal. Firstly, the image force between tips and surfaces is calculated using a numerical method and also the atomistic simulation technique implementation. After that, the relative strength of the image force with respect to the van der Waals forces and chemical forces present in different tip-systems which include the surface terrace, neutral and charged steps was studied, and then the dipole formed by a vacancy par at a step was also studied. The results and limitations of Scanning Tunneling Microscopy and non-contact Scanning Force Microscopy (NC-SFM) experiment were also discussed.

The application of Scanning Tunneling Microscopy (STM) and non-contact Scanning Force Microscopy (NC-SFM) using finite cluster of Nacl absorbed on a metallic substrate can be described theoretically by using a conducting spherical tip of radius R interacting with a conducting semi-infinite substrate which is also known as the substrate with an absorbed final cluster of ionic material which is known as the sample on it. That is, a conducting spherical tip of radius R interacting with not only a conducting semi-infinite Substrate (substrate) but also with an absorbed finite cluster of ionic material (sample) on it [12]. The conducting tip by an ionic material is contaminated by using a finite cubic mgo cluster oriented by one of its corners down to the Nacl cluster that was absorbed on the metal.

The conducting tip by an ionic material is contaminated by using a finite cubic mgo cluster oriented by one of its corners down to the Nacl cluster that was absorbed on the metal substrate. In this case, the tip and substrate are conductive which is enough to keep their surfaces at constant potential at each point of flow cantilever oscillations. They are both connected together in a joint circuit, that is, the tip and the substrate. The tip and substrate will form an external non-uniform electrostatic field and an additional contribution to the system energy when bias is applied to them. The bias applied to the tip and substrate will affect the geometry of the sample atoms and also affect the force imposed on the tip. However, this effect on tip and substrate is not very useful for typical experimental values of the bias (<1v).

A result show that in Scanning Tunneling Microscopy (STM) [3]and non-contact Scanning Force Microscopy (NC-SFM)[10,11] application is used to calculate the tip-surface forces of several characteristic systems with respect to image forces and these systems can also represent a surface-substrate class in which image forces play a major role in the interactions.


STM/SFM can also be applied in immunoassays, in this process, the Scanning Force Microscope have high resolution and ability to detect single binding events which can be combined with micro array technologies to give a sensitive, cost-effective substitute for conventional assays. In this application, Scanning Tunneling Microscopy is used to image gold beads bound to immune complexes over conductive surfaces while Scanning Force Microscopy is used to differentiate between individual human serum albumin (HSA), anti-HSA antibodies, and HAS= anti-HAS complexes absorbed in mica.

In this application, the grid regions consisting of a hydrophobic octadecanethiolate monolayer was separated by the coupling sites. The addition of surfactant Tween80 was used to eliminate the non specific binding of the receptor, a goat anti-rabbit antibody to the grid regions which allows these regions to serve as an internal reference plane for the increase in height upon binding. The interaction was completed at a time of approximately 5mins which is in agreement with other antigen-antibody-binding studies.


In this type of application, a vacuum is used. In the vacuum, a simple one-dimensional square-well barrier is placed between the Scanning Tunneling Microscopy (STM) tip and the substrate as shown in the figure below. This is used to describe the electron tunneling mechanism in electrochemical Scanning Tunneling Microscopy (STM). This mechanism is used to describe the exponential decay in the tunneling current I, as the substrate-tip distance, S increases by

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I α exp (-1.025) (1)

Where Ø is the tunneling barrier height in electron volts and S is an angstrom despite the fact that imaging force experienced by the tunneling electrons is some of the factors being ignored, it does not affect the verification of exponential decay over a wide range of tunneling currents experimentally.

The logarithm of the tunneling current dependent with respect to the distance is a measure of tunneling barrier height[13], which can be written mathematically as,

Ø=²/8m (dlnI/ds) ² (2)

We can measure the tunneling barrier height by increasing the tip-substrate distance through the Z-piezo regularly using an ac modulation. This is because the square barrier becomes ill defined when the tip-substrate distance is very small does not include imaging force. The figure below is a one-dimensional substrate-vacuum-STM tip tunnelling junction [13-19].

Scanning Tunneling Microscopy (STM) experiment [17, 18] using the vacuum shows that non-experimental can only occur at an extremely small tip-substrate distance where the tunneling barrier disappears.

Scanning Tunneling Microscopy (STM) experiment can be applied to study redox proteins such as cytochrome and blue copper protein pseudomaon as aeruginosa azurin. In this process, there is a spike localized beside the centre of each protein which implies that there is higher electron tunneling concentration through the spike region. The tunneling current enhancement in the spike could occur due to the redox centre, copper in the azurin molecule.

Another application is an electrochemical Scanning Tunneling Microscopy (STM) nanofabrication technique [20] which uses localized etching and plating on the surface through the sharp Scanning Tunneling Microscopy (STM) tip. This is carried out by using a tip-substrate bias of 1.4v at a current of 1nA in 0.05% HF, Scanning Tunneling Microscopy (STM) was used to scan it and it was observed that the area scanned by Scanning Tunneling Microscopy (STM) was etched, because of this 20nm wide and 1-5nm deep of nanostructures was fabricated with the use of Scanning Tunneling Microscopy (STM). It was observed that there was local oxidation or etching of the Si electrode in the empty states at the Scanning Tunneling Microscopy (STM) tip that is [22], the tunneling of electrons from the valence band of the Si electrode used [21].


Scanning Tunneling Microscopy (STM) can be applied on individual molecules, an example is porphyrin-based molecules cu-tetra-3, 5 di-tertiary-butyl-phenyl porphyrin[23], which is a process in where the porphyrin system interact electronically with the substrate and then decoupled by the di-butyl-phenyl (DBP) substituent's while another example is Fullerene C60 which[19]happens

when the electron deficient molecule is coupled strongly to the substrate through hybridization, splitting and broadening of the lowest unoccupied molecular orbitals (LUMO) States in particular.

Highest occupied molecular orbital and lowest unoccupied molecular orbitals that is, HOMO-LUMO manifold hybridized with the substrate must be present for Scanning Tunneling Microscopy (STM) to be achieved by virtual resonance tunneling through the tails of the electronic molecular wave function [24, 25] which exhibits a non-zero positive or negative contribution in the Fermi level Ef region when it is being adsorbed on a metallic structure.

Scanning Tunneling Microscopy (STM) can also be applied on magnetic nanostructures [25, 26] because of its high resolution tools which allow the characterization of magnetic nanostructures with high precision.

It can also be used to monitor the growth mode of magnetic films and also the intermixing at the interface between a non magnetic substrate and a magnetic film [26].

Scanning Tunneling Microscopy (STM) has also been used to study self-assembled monolayers and sub-monolayers of butanethiol adsorbed onto highly uniform and also it has been used to study the DNA adsorbates on different substrates which were prepared by using different decomposition techniques and it was investigated. In the elimination of the residual organic adsorbates on the Au/mica the elimination which are sulfochromic and piranha acids. This treatment of the oxidizing solution leads to etching of the surface and disruption of surface error.

Results show that Scanning Tunneling Microscopy (STM) is used to take the images at approximately 24-48 hours, the growth of crystalline domains at the expense of the disordered liquid phase show after film deposition. The film structure show a well-resolved striped phase of 75x75nm2 image. The surface defect density is reduced by using a uniform gold film because the surface is planar and the gold substrate separated. Each separated gold substrate has stripes that are brighter than the adjacent stripes; this is due to the difference in elevation. The bright stripes are higher than the dark stripes because they are approximately 0.2-0.4Å and their distribution varies across the image and the sample.


Scanning Tunneling Microscopy (STM) has been used to examine, buthanethiol monolayers, butanethiol sub-monolayer formations. It has also been applied to vacuum which has a scanning range which varies from nanometer to micrometer at a stabilized current of about 30PA-3nA.

Scanning Force Microscopy (SMF) is also an analytical tool in basic and applied biological science. It is used in the study of nanomanipulation and nanofabrication.

Scanning Tunneling Microscopy (STM) has also being developed to probe fast kinetics and it is also useful in extracting electron properties transfer and probed molecules. The electronic information which make one to identify molecules and also the chemical reactivity of the molecules.

It also makes us to understand the electro chemical mechanism in the fabrication of varying nanostructures.