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Glossary terms about Image

A "picture" of the surface being examined. Generally presented in false colour with bright areas representing higher areas of the quantity being measured.

▼3 more terms contain Image

32 pages mention Image

AFM calibration methods
L. Tip characterization from AFM images of nanometric spherical particles. 
AFM imaging: Interactions between the probe and sample
A plot of this upward and downward motion (z), as a function of the tip x - y position on the sample surface, provides a high-resolution image of the surface topography. 
AFM papers
L., et al. Recent Advances in Atomic-Force Microscopy of DNA. Scanning 15(5): 296-299, 1993.Journal Link... Umemura, K., Arakawa, H., et al. High-Resolution images of Cell-Surface Using a Tapping Mode Atomic-Force Microscope. 
AFM: Background information
Either the probe or sample is mounted on a piezoelectric scanner which can move in the x,y, and z directions, and is used to raster scan the probe across the sample surface to acquire an image in 3 dimensions. 
Cantilever tuning - only for tapping and non-contact modes
Composite control (PID)
PID is the most complex but also has the widest application:  
Contact and tapping modes
This means that the user gets the greatest sensitivity to measure the topography of the sample.  
Contact mode
The vertical movement is used to build an image
Derivative control
Can’t be used alone because it does not actually measure the error (only its change)  
The following a is general discussion of feedback in the context of collecting images in SPM. 
Floating control
In this case, output of the controller is determined both by the error and an input which changes the output at a defined rate  
Thus, the higher you can have the integral gain, the better image quality can be achieved. 
How is the Data Displayed?
In the vast majority of cases, the data is displayed as a false colour image
Image artefacts
Tip convolution is due to the radius of curvature of the tip being similar to or larger than the width of the feature being imaged. 
Image Scanning and feedback parameter optimisation - scan rate
Scan rate  
Integral control
To overcome this, the error is summed over time (integrated) and that sum is multiplied by a gain to be added to the present controller output:  
Electron microscopes create magnified images of samples by focusing an electron beam using magnetic fields produced by electromagnetic lenses composed of wire coils. 
Laser alignment on cantilever
Figure 17 shows optical images of the laser alignment procedure. 
Measuring forces in the tip-sample space
It now experiences no surface forces and therefore the deflection of the cantilever is zero and the curve is flat.  
Non-contact mode
If a very thin fluid layer is covering a rigid sample, in non-contact mode the tip may be oscillating above the fluid and so the liquid layer and the underlying surface can be imaged. 
Proportional control (P)
Scanner artefacts
Nonlinearity of the x - y plane displays as surface features appearing stretched or contracted at the top of the image, and then appearing to correct nearer to the middle and bottom of the image
Scanning probe microscopy in practice
Scanning Tunneling Microscopy (STM)
The unique aspect of STM is that is can readily be used to acquire images with atomic resolution which is not generally true for the other SPMs. 
Set point - Tapping mode
This will result in poor image tracking, similar to that displayed in Figure 13. 
Set-point - contact mode
However, if too much force is applied to the surface then the tip could damage the sample surface, or in time damage to the tip itself can result in image artefacts e. 
Specimen choice
Therefore any surface with more than five microns of roughness will be extremely difficult to image with most AFMs. 
Tailor this module
You can create you own customised menu and share it with students or colleagues by sending them a link. Drag menu items into a custom menu.  
Tapping mode
Therefore, tapping mode is preferred to image samples with structures that are weakly bound to the surface or soft samples. 
Tip artefacts
The resultant image can possess a number of tip artefacts and it is important for AFM users to recognize these artefacts. 
Virtual Scanning probe microscopy
Please select which sample you would like to view under the scanning probe microscope.