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SPM Probe tips

SPM Probe tips. CNT attached to a Si probe tip. Rectangular Cantilever:. Spring constant:. Microcantilevers: Mechanical properties. Resonant frequency:. E: Young’s Modulus I: Moment of inertia L: length, W: width, h: height. Triangular Cantilever:. Microcantilevers II.

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SPM Probe tips

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  1. SPM Probe tips CNT attached to a Si probe tip

  2. Rectangular Cantilever: Spring constant: Microcantilevers: Mechanical properties Resonant frequency: E: Young’s Modulus I: Moment of inertia L: length, W: width, h: height Triangular Cantilever:

  3. Microcantilevers II • Detection Of Cantilever Deflection: • There are 3 common techniques for cantilever detection: • Optical detection: commonly used for scanning probe microscopy. This is well suited for a single cantilever, but not suitable for an array of cantilevers • Piezoresistive detection: used for sensing purposes and in integrated circuit applications. Generally not as sensitive as the Optical detection technique • Capacitive detection: used in some transducers. Highly sensitive for short distances, but not for long distances. Cantilever quality factor Q: Quality factor depends on loss mechanisms. Usually the quality factor is ~50 in air. In vacuum, it can go up to several thousand or more. Ultimately, the resolution of the cantilever deflection in resonance is mostly limited by its thermomechanical noise given as

  4. The cantilever based sensors can be classified into three groups • General detection of any short range forces: Scanning probe microscopy • Detection of mass attachment: based on changes in frequency response • Detection of molecular adsorption: based on changes in surface stress of a functionalized cantilever. This can also be detected based on resonance amplitude change. • Detection of radiation (IR or nuclear): based on deflection of a bimaterial cantilever, or from deflection changes • Detection of charges or electric or magnetic fields: Based on resonance frequency or amplitude changes Microcantilevers III Cantilever based sensors: Note that although cantilevers are highly sensitive to stress changes, but resonance frequency based changes are the most sensitive due to quality factor enhancement.

  5. Goutam Koley Kelvin probe technique Kelvin probe technique measures surface charge, surface potential, and surface work function. The advantages are quantitative nature, and ease of operation. Evac qVcon = qVdc = Si + Eg,Si - (semi + qs) semi Si EC Ec qs p+ Silicon Eg,Si EF,semi qVcon Ev,EF,Si Probe Tip Semiconductor Sample G. Koley and M. G. Spencer, J.Appl. Phys. 90, 337 (2001)

  6. Goutam Koley Mathematical Model for SKPM G. Koley and M. G. Spencer, J.Appl. Phys. 90, 337 (2001)

  7. Goutam Koley CONTROLLER SKPM Measurement System AMPLITUDE DETECTOR LASER OSCILLATOR LOCK-IN CIRCUITRY POSITION DETECTOR Vacsint Z SCANNER CONTROLLER SAMPLE Vdc Vdc MORPHOLOGY IMAGE SURFACE POTENTIAL IMAGE G. Koley and M. G. Spencer J.Appl. Phys. 90, 337 (2001)

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