class38 - Scanning Tunneling Microscope Todays class...

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Today’s class: • Wrap-up S canning T unneling M icroscope (STM) discussion Quantum harmonic oscillato • Quantum harmonic oscillator • Superposition states Scanning Tunneling Microscope Measure current between tip and sample Requires very precise control of the tip position and height. How to do it? With a piezoelectric actuator! Typical piezo: 1V b 100nm displacement. Applying 1mV moves tip by one atom diameter (~100pm) Piezoelectric actuators and sensors are everywhere! Buzzers in electronic gadgets and in smoke alarms. Microphones in cell-phones. Quartz crystals. BBQ grills and lighters. Knock sensors in car engines. Seismology. Seismology. Concrete compactors Sonar devices (Submarines, Robotics, Automatic doors) Bones Tunneling rate: T ~ (e - α d ) 2 = e -2 α d How big is α ? h E) m(V = 0 2 α 10 How sensitive to distance? Need to look at numbers. d If V 0 -E = 4 eV, α = 1/(10 -10 m) So if d is 3 x 10 -10 m, T = e -6 = .0025 add 1 extra atom (d ~ 10 -10 m), how much does T change? T = e
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This note was uploaded on 08/24/2010 for the course PHYS 2130 taught by Professor Staff during the Spring '08 term at Colorado.

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class38 - Scanning Tunneling Microscope Todays class...

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