Fabrication and Characterization of Nanomaterials纳米材料的制备与表征.ppt
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John Carruthers, Portland State University Fabrication and Characterization of Nanomaterials John Carruthers Physics Department Portland State University June 26, 2006 Fabrication and Characterization of NanomaterialsOutline of Opening Lecture Why physics changes at the nanoscale Examples of nanoscale devices, circuits, and systems General semiconductor IC fabrication methods and limitations Need for metrologies to support semiconductor fabrication, performance evaluation, failure analysis, and reliability assessment Types of metrologies Wrapup and future challenges Why physics changes at the nanoscale Surface area/volume ratio increases as 1/R and the surfaces and interfaces become the major contributor to materials properties, thermodynamic behavior, and energy carrier dynamics at the nanoscale Diffusion of atoms to surfaces and interfaces changes the thermodynamic equilibrium conditions Solid transport of heat, matter, charge carriers, photons, -- all change at the nanoscale because the scattering centers are spaced further apart than the nanoscale dimensions Electronic density of states becomes discontinuous when dimensions are reduced to quantum wells, quantum wires, and quantum dots. This leads to new physical concepts such as energy filtering, carrier “pocket engineering”, and electronic transitions (such as semimetal-semiconductor transitions) Size-dependent energy levels due to quantum confinement change the energetics of doping semiconductor nanocrystals Fluid transport in nanoscale channels can be enhanced by atomic smoothness, contact angle changes, and molecular ordering of the molecules being transported Why physics changes at the nanoscale Terascale semiconductor device densities lead to new nanoscale problems: Overlap of electric fields causes threshold voltage lowering in devices and parasitic signal transfer in interconnects Tunneling induced leakage causes excessive charge loss across very thin dielectrics (increases exponentially as 1/thickness
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