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Muhammad Khurram Farooqi (CIIT/FA11/MSPHY/006/LHR) Department of Physics CIIT Lahore 1 Scanning Probe Microscopy Submitted by Report ( Submitted to) Dr. Aamir Razzaq

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Introduction 2

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Scanning Probe Microscopy 3 Scanning Probe Microscopy (SPM) is a technique of microscopy which makes images of surfaces, using a physical probe that scans the sample.microscopy An image of the surface is obtained by mechanically dragging the probe on surface of the specimen, line by line. SPMs are used both as standard analysis tools and as high-level research instruments.

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Historical Background 4 SPM was founded with the invention of the scanning tunnelling microscope in 1981.scanning tunnelling microscope In 1986, very soon after their first publications about the STM in 1981, the inventors of this marvellous instrument, Gert Binnig and Heinrich Rohrer from the IBM Research Laboratory in Rschlikon (Switzerland), were awarded the Nobel Prize in Physics.Nobel Prize Nowadays, SPMs can be found in many academic and industrial physics, chemistry and biology laboratories.

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Components 5

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Figure 6

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S.P.M Working 7

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Working 8 The STM works like a record player The principle of the STM is very simple. Can be compared best with that of an old-fashioned record player. Just like in a record player, the instrument uses a sharp needle, referred to as the tip, to interrogate the shape of the surface.

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Working 9 But in contrast with a normal record player, the STM tip does not touch the surface. A voltage is applied between the metallic tip and the specimen, typically between a few milliVolts (mV) and a few Volts (V).

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Working 10 When the tip is far away from the surface, the current is zero. The STM operates at very small distances between the tip and the surface of only 0.5 to 1.0 nm, i.e. 2 to 4 atomic diameters. At these distances, the electrons can jump from the tip to the surface or vice versa. This jumping is a quantum mechanical process, known as tunneling.

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Working 11 Hence the name of this microscope is tunneling microscope. The tunneling process is very difficult, which implies that the tunneling current is always very low. STMs usually operate at tunneling currents between a few picoAmperes (pA) and a few nanoAmperes (nA).

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SPM Environments 12 Scanning probe microscopes can be operated in a variety of environments. But only four environments are described: Ultra-high vacuum (UHV), Ambient (air), Liquid, and electrochemical (EC).

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1. Ultra-high Vacuum 13 The first STMs were operated primarily in UHV to study atomically clean surfaces. STM applied to atomically clean surfaces allows characterization of structure, without the added complication of contamination that is always present in air.

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2. Ambient(Air) 14 The easiest, least expensive, and thus most popular environment for SPMs is ambient, or air. STM in air is difficult, since most surfaces develop a layer of oxides or other contaminants that interfere with the tunnelling current. A clean, fresh surface can be prepared by peeling away older surfaces.

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3. Liquid 15 Liquid cells for the SPM allow operation with the tip and the sample fully submerged in liquid, It has capability for imaging hydrated samples. A liquid environment is useful for a variety of SPM applications, including studies of biology, geologic systems, corrosion etc.

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4. Electrochemical 16 Like UHV, electrochemical cells provide a controlled environment for SPM operation. EC-SPMs consist of a cell, a potentiostat, and software. Applications of EC-SPM include real- space imaging of electronic and structural properties of electrodes.

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Key features include An instrument that is easy to use Has lower operating costs. Minimal training time is desirable in a multi-user facility. Finally, an instrument that is easy to run will be used moreand produce more results. 17

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1. User Interface SPMs are built upon operating systems that allow multi-tasking. 18

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2. Optical Microscope All SPMs include optical microscopes to help monitor. A good optical microscope speeds up our work. In optical microscope, the following features are present: optical image clarity useful magnification range zoom lens integrated video camera 19

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Applications 20 One of the most versatile and at the same time also very complex SPM measurement technique is the optical nearfield microscopy (Scanning Nearfield Optical Microscope, SNOM or NSOM). This class of instruments are used for investigation of electromagnetic interactions (light) with a resolution below the wavelength of the used electromagnetic field.

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Applications 21 An STM can be used as a spectroscopy tool, probing the electronic properties of a material with atomic resolution. It is used to study the local electronic structure of the surface known as scanning tunnelling spectroscopy (STS).

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Innovation 22 If we have this instrument in our Lab then we can scan the surface if the Electroactive Conducting Polymers ECPs and quite easily fine out their properties such as Electrical Mechanical Surface analysis etc

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Types 23

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The End 24