The Scanning Tunneling Microscope
The scanning tunneling microscope is a type of instrument which is used to show the 3D image of electrons or a surface it is also known as STM.
We can say that it’s a tool for viewing the nano properties of electrons at the fixed distance; The STM is based on the recent concept of quantum tunneling or small size tunneling.
Components of Scanning tunneling Microscope
STM have many important conponents like any other scanning device. These components works together to provide accurate result. components are listed below.
- Scanning tip
- Piezoelectric controlled height and x,y scanner
- Coarse sample-to-tip control,
- Vibration isolation system, and
How Scanning tunneling Microscope works ?
Scanning tunneling microscope scans the electrons at fixed distance. First, a voltage bias is applied and the conducting tip is placed closer to the sample to be examined.The tip is also known as stylus ,stylus is extremely sharp and usually made up of a finest diamond , which is switched off when the tip and sample are sufficiently close.
When a conducting edge or tip is brought near the surface to be tested, a specific voltage variation is applied which allows electrons to pass through the tunnel in the vacuum. In the result, tunneling current is obtained which is the function of accurate tip position. Information is gathered by monitoring the current according to the tip position which scans across the surface, and this information is usually displayed in form of image.
The stylus is moved in the upward direction and then lowered in order to keep the each signal undistorted .This allows it to follow even the smallest data of the surface it is scanning. Storing the vertical movement of the stylus makes it possible to observe the structure of the surface atomically in organized manner. A profile of the scanned surface is created, and with the help of this profile contouring map is generated from the computer system attached to the microscope. The STM works best with conductors. But it can also work with the organic molecules all required is to fix organic molecules on a surface and study their structures. This technique has been used in the study of DNA molecules.
Current applications of scanning tunneling microscope
Studies of surfaces if significant in many field of work like physics and microelectronics. These kinds of microscopes are used in the physics, chemistry, micro and Nanoelectronics where they are used to observe atomic surfaces. For example in catalysis. It is considered to be one of the most efficient and high performance devices in the world of advance research and step up technologies. The most common purpose of scanning tunneling microscope is the DNA test.
Issues Regarding STM
- STM could be a challenging technique, as it need very clean and plain and stable surfaces, extra sharp tips, high vibration control , and efficient and integrated electronic devices. these all specifications makes STM expensive.
- The resolution of the image scanned by STM is limited because radius of curvature is fixed and scanning stylus tip does not support the modification in the resolution.
- If scanning tip has two tips than there is a chance of occurrence of artifacts instead of single atom display.
- Because of huge sensitivity of tunnel current, proper vibration and isolation is required for obtaining best results from the STM.
- At first,Binnig and Rohrer magnetic levitation was used to keep the scanning tunneling microscope free from extra vibrations and now mechanical or gaseous spring systems are usually used for controlling vibrations. Additional mechanisms for reducing current are also required sometime to proper implement the scan.
Note: Video tutorial which describes how scanning tunnel microscope works.