Chapter 1: --Bohr's formula for H spectra is derived with the assumptions of discrete non-radiating orbits and that the centrifugal force cancels the nucleus-electron attraction --Definition: anisotropy - exhibiting properties with different values when measured in different directions --Crystal Lattice Structures Simple Cubic Face Centered Cubic - additional atom in center of each face Body Centered Cubic - additional atom in center of cube Diamond/Tetrahedral - most important for semiconductors, uses covalent bonding unlike others Zinc Blend - like tetrahedral, but with two different kinds of atoms *Elements that form covalent crystals: carbon, silicon, germanium, gray tin --Definition: phonon - quantized mechanical vibration --When two atoms are brought close together, the energy levels of each disturb the other, causing an upshift of energy on one side and a corresponding downshift in energy on the other side. This is the reason why dies can absorb such a wide range of light-each atom pair has slightly different upshift and downshift, covering a lot of possibilities. "The phenomenon of energy-level splitting is very much like that which takes place between two tuned circuits. If two identical tuned circuits are coupled together, each will influence the other and they will each resonate at a slightly altered frequency. If the coupling is made large enough, the familiar double-peaked response is obtained. ..as the atoms are brought closer, the spreading increases." Chapter 2: --A potential could excite electrons into the conduction band, but this won't contribute much to conductivity since the mean free path is 10^(-8)m and after that much travel, the excited electron will have a collision that converts all the potential it took in being excited into wasted heat. To cause a current, there would have to be enough potential to divide into all the steps of this length across the entire piece of metal. That would be the breakdown voltage. For conductors with electrons in the conduction band, not nearly as much energy is taken from the field because they don't have to be excited to a higher energy level. --Mean free time/Mean free path - how long electron goes before a collision --Half filled bands contribute large amounts of conductivity since they have plenty of electrons and plenty of space to move to --Conductivity = charge*(no. e- in conduction band)*(velocity of electrons/potential) The last parentheses is called the mobility and it is a function of the metal The total conductivity is this product plus the corresponding product for "holes" --"The external field simply bends the path of the electron between collisions." Chapter 3: --Particle Distribution Functions: Maxwell-Boltzmann - classical distribution, describes gases and other rarefied systems f_mb(E) = A*exp(-E/(kT)) Chapter 4: --Intrinsic - refers to properties of a crystal in its purest form --Minority Carrier Suppression - doping of one type cancels out the other type Chapter 5: --Hall Effect - potential is developed across a current carrying metal strip when the strip is placed in a magnetic field, described by the Lorentz Law, hence the new potential is perpendicular to the magnetic field and the current. The hall effect is weak in metals, but larger in semiconductors. Chapter 6: --Circuit Potential - difference in work functions between two metals The circuit potential between two substances is the difference in their Fermi Energies because the circuit potential is equal to the Fermi energy in the solid. (The circuit potential is the sum of the structural potential and the macropotential(=charge distributions such as surface charge, double layers, and space charge), the circuit potential is what gets measured with a voltmeter) --Why is a double layer created? --Since semiconductors have less free electrons, the potential change is distributed deeply into the semiconductor so it can access enough electrons to cover the difference Chapter 7: --There is almost no electric field in the crystal body-current is carried almost entirely due to diffusion due to density gradients.