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EECS 321 Spring 2002 Semiconductor Electronic Devices Prof. David A. Smith (Dave)

EECS 321 Spring 2002 Semiconductor Electronic Devices Prof. David A. Smith (Dave) Glennan 514B, das23, x4073 Class: MWF 9:30-10:20, White 411. LECTURE 6 (12 slides). PHENOMENOLOGICAL BASIS of QUANTUM MECHANICS. Variable wavelength source. metal. V. Adjustable intensity.

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EECS 321 Spring 2002 Semiconductor Electronic Devices Prof. David A. Smith (Dave)

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  1. EECS 321 Spring 2002 Semiconductor Electronic Devices Prof. David A. Smith (Dave) Glennan 514B, das23, x4073 Class: MWF 9:30-10:20, White 411 LECTURE 6 (12 slides) Prof. Dave Smith

  2. PHENOMENOLOGICAL BASIS of QUANTUM MECHANICS Prof. Dave Smith

  3. Variable wavelength source metal V Adjustable intensity collector A Adjust V to stop current Ref: S&B Chapter 2 The Photoelectric Effect no emission for n<n0 Energy quantized E=E0-eV 0=(hn-ef)-eV eV= hn-ef stopping potential f=c/l -ef Work function Classical physics of E+M waves couldn’t explain these features  Works at arbitrarily low intensity  Energy localized Prof. Dave Smith

  4. Electromagnetic wave propagation: E=E0ej(wt-kx) Power flow: Poynting vector shows intensity P=ExB. Energy density is E=eE2/2. Fields have a spatial distribution in electromagnetic waveguides (metal or dielectric). Light Passing by a sharp edge shows interference fringes. We can associate P with the probability per unit time of finding a photon in a given volume of space. Let the E-field Really be a amplitude Y(x) and probability function = |Y(x)|2 Conclusion: Photons exhibit wave-particle duality Prof. Dave Smith

  5. + Planetary model of atomic electrons doesn’t make sense in Classical Mechanics Charged planetary atoms would collapse while radiating… But atomic radiation is clearly quantized (decay spectra form sharp lines) Ref: S&B Chapter 2 Prof. Dave Smith

  6. Atomic Spectra – specifically H Convert to l, l2, 1/l (=c/f), etc. looking for mathematical pattern to aid in developing a theory… DEab=cR(1/a2-1/b2) Ref: S&B Chapter 2 Prof. Dave Smith

  7. The Bohr model of the H atom Problem 11. Reproduce the Bohr math for planetary orbits that gets the proper energy levels and spectroscopic series. What is the Rydberg constant that you get in cm-1 (see Eq. 2-3b in text)? What is the wavelength for Balmer E32 in Angstroms? Quantization rule: n wavelengths fit in nth orbit L=nhbar E32 Ref: S&B Chapter 2 Prof. Dave Smith

  8. Electron beam: The 2-slit experiment Double slit filament Fluorescnt screen Photographic plate 50 kV plates Ref: Haliday, Resnick and Krane, 4th ed., Wiley (1992) Prof. Dave Smith

  9. Electron beams and light beams from a straight edge LIGHT Photons act like waves (interference) But also they act like particles (as in the photoelectric effect) ELECTRONS Electrons act like waves (interference) As shown in the expt to the right. Ref: Haliday, Resnick and Krane, 4th ed., Wiley (1992) Prof. Dave Smith

  10. particle-like wave-like Light photoelectric effect interference Electrons e-beams interference p=E/c=hf/c=h/l=hbar2p/l=hbark p=mv  h/l Wave-Particle Duality PHOTONS: deBroglie wavelength ELECTRON Analogy: Problem 12. Motivate the relation p=E/c for E+M plane waves. This will require you reviewing the Poynting vector and the concept of radiation pressure. Prof. Dave Smith

  11. Problem 13. Do S&B Problem 2.6. LIGHT ELECTRONS Ref: Haliday, Resnick and Krane, 4th ed., Wiley (1992) Prof. Dave Smith

  12. Problem 14. Reading Assignment: • A. Tonomura et al., • “Demonstration of single-electron buildup • of an interference pattern,” • Am. J. Phys. Vol. 57, pp. 117-120 (Feb. 1989). • Look up the electron microscope on the • web or elsewhere. Describe how it works. • Use a sketch or two. Is it intrinsically a quantum • device or definitely classical or a mixture? • Explain. • (b) What is the velocity and wavelength • of the 50-kV accelerated electrons? • (c) What is the prohibition against • very long duration experiments? • (d) There is a deep meaning to the • observation that there is never more • than one electron in transit at any • given time. Discuss why this means • that the electron acts like a wavefront. Ref: Feynman Lectures on Physics, vol.3, Addison Wesley (1965). Prof. Dave Smith

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