A student asserts that silicon and germanium become good insulators at very low temperatures and good conductors at very high temperatures. Do you agree? Explain your reasoning.

In this and following questions, we develop a model for spontaneous emission of a photon by a diatomic molecule AB (a model molecule), which rotates and vibrates. In intermediate calculations, atomic units (a.u.) will be used: unit of mass = the mass of electron, unit of charge is the proton charge e, (e is a positive constant so that the charge of electron is -e). The initial state of the molecule is an excited rotational (1=1) and excited vibrational state (v=1). We consider a molecule with the reduced mass µ = 10,000 a.u. (it is similar to the mass of CO). After emitting a photon, the molecule will go to the 1=0, v=0 state. The first question is about the model potential of the molecule. It is represented by a potential of the form: V(r) = C6 p12 C12 p6 " where r is the distance between A and B in the molecule, C6 and C12 are positive constants (C6 =2 and C₁2-1). This potential has a well meaning that the molecule is bound. The first thing to do is find vibrational states of the…

1. An additiona layer was inserted in the middle of a 20 layer-pair dielectric stack of quarter-wave layers (titanium-dioxide & fused silica, initial medium: air, substrate: BK7 glass, n = 1.5, design wavelength 600 nm). Please numerically find the power reflection coefficient vs wavelength (visible & near infrared) for the following cases: 1) The additional layer is a quarter-wave layer from titanium dioxide. 2) The additional layer is a one-eighth-wave layer from aluminum oxide.

Use T if it's True and F if it's False. Justify  I. A semiconductor is characterized by having a very wide forbidden band, between conduction and valence.II. The band of the Energetic Interval where there are those electrons that can move freely and are free from the attraction of the atom is called conduction.III. In a semiconductor with donor atoms (for example P in Si), the donor level is just below the conduction band.IV. A diode will conduct current in only one direction and act as an open circuit when the current tries to move in the opposite direction.

Answer it correctly please. Explain your answer. I will rate accordingly with multiple votes.

Would you expect that a material with little or no crystal structure (a “glass”) could exhibit superconductivity? Why or why not?

Is it reasonable to expect superconductivity in a "glass," a material with almost no crystalline structure? Why or why not, if that's the case?

For Ge semiconductor, assume the Fermi energy level is 0.15 eV below the conduction band energy Ec. Let the absolute temperature T for items i and ii be 200 K. i. Find the temperature at which there is an electron at the state Ec + 0.5 x KbT with probability 30%. ii. Repeat item i by using the Boltzmann approximation rather than the Fermi-Dirac distribution. ii. Find the difference in temperature between items i and i above and express this difference as percentage.