Band Definition and 531 Threads

Might be an easy question (or not). What determines the band gap of an element? As far as I know, silicon is the most efficient single-element semiconductor because of it's small (but nonzero) bandgap. Next (as far as I know) is Selenium. I'm aware there are more efficient compounds, but...

How to sketch the band diagram of intrinsic semiconductors including the fermi level with the electric field present verses distance? Its not a homework question.

Homework Statement Write a Java program to solve the following problem. An elastic rope starts out with length 100 meters. The start of the rope is fixed to a pole and a worm is placed on the rope at the start and the worm starts crawling towards the end. Each day the worm crawls 6 meters...

I am reading about solid state electronics(semiconductors). I've read that when atoms of many many atoms are brought close each other,as in a solid, the energy levels of energy states of different atoms get split up into different closely lying energy states collectively forming a band...

Homework Statement Calculate Efi with respect to the center of the bandgap in silicon for t= 200, 400, 600 kelvin. Homework Equations ni = Nc e^-((Ec- Ef)/(kt)) k = boltzman constant t= temperature in kelvin Ec = energy level of the conduction band ef= fermi energy level ni=...

So I've cut the isolated band of my earphones to see what's inside (my cheap earphones quit working). I expected to see copper. And I have. But, there is also a red wire and a blue wire amongst the copper. At they dyed copper, or a different metal...

Hi, I understand for metals the conduction band is usually partially filled. However, at absolute zero, is the conduction band empty (for metals)? I'm asking this because as far as I know, the definition of valence band is "the highest occupied band at absolute zero" However, I have...

Hi All, There is a simple question in my mind. A band with energy Ek has dispersion in k space. Then what it looks like in the real space?

When a n-type semiconductor is brought into contact with a metal, then alignment of the chemical potentials of both systems leads to band bending within the depletion layer, e.g on the semiconductor side. does the amount of band bending (change of potential) also depend on the donor...

why band gaps occur according to bloch theory?

how is the relationship between fermi level and band structure of solids can effect electrical conduction properties of a material?

Buckaroo Bonzai's band has 88 on the drums. Yes, it's similar to another logo for BB, with the first one backwards. I noticed a device on his vehicle looked nearly identical to the flux capacitor in the DeLorean in Back to the Future. BB - '84 Back to the Future - '84 Poetic license or...

Metal nanoparticles (Au, Ag, Al or ...) can coat on porous silicon, the particles can be located inside the pores or on the silicon micro/nano structures. By applying this type of coating is there any change in band structure of porous silicon? As I've measured the band gap has changed.

HI, I am wondering what factors go into spectral efficiency and determining and calculating guard bands. Could a tunable antenna or filter within a handset reduce the necessary size of a guard band thereby increasing a networks spectral efficiency? How are guard bands determined/defined and...

Hiya, been given this question which I am having problems with. Semi conductor quantum well structure contains a 100A thick layer of GaAs between thick AlGaAs layers. Find the band gap for the structure, where GaAs has the following parameters; conduction band effective mass 0.067 me, heavy...

Hi everyone, I'm working on random materials which are coincidencely oxides and showing semiconductor behaviour... Some of these are metals and i suddenly realize MOS (which are practically everywhere). I know them, i know how they work and behave still i can't get to understand the effect of...

Hi all, I'm working on some image analysis as a part of my research, specifically trying to match images. The method I am using transforms the image into the frequency domain and then applies a band pass (or mesa) filter to eliminate noise and the dc component of the image. I have never...

Homework Statement The Gibbs free energy of an elastic band satisfied dG = -SdT - LdF where F is the tension and L the string's length. At fixed temp the entropy is given by S = So - a(L-Lo)^2 + b(L-Lo)^2 Where Lo is the length of the elastic at zero tension and a and b are positive...

The band gap discontinuity in DFT? Hi everybody... I've read about the band gap problem of Density functional theory, there is a discontinuity of the band gap when an electron add to the Kohn-Sham system I have two questions could anybody answer me? please 1- why this discontinuity happens...

We know in silicon a valence electron can be excited to conduction band if it absorbs one photon(one photon absorption) or two photon(two photon absorption),my question is that it must need a certain amount of time for the electron to 'travel' from the valence band to the conduction band(I...

I am not able to understand how a bandgap voltage reference works. The simplest ckt I found was here - (figure 2) - http://www.national.com/rap/Application/0,1570,24,00.html You have 2 branches of diodes, in one branch rich (high) current flows and in the other lean (small) current flows...

1. i have a physics project where we have to make a car that accelerates the fastest during 3.0 m. it also must be accelerating for the whole 3.0m. I am using a simple rubber band car where the rubber bands are attached to both axels and are wound up. i have to make a bunch of calculations but...

We really need help naming our band, I just found this forum and it seems like an excellent place to try, so a little contest: If we choose a name you come up with you will receive $200 usd by paypal. The ideal name should grab people's attention. If it helps: we’re inspired by sci-fi...

Hi everybody, I would like to know if someone could explain to me what happens to the refraction index of gold at grazing angle (X-ray applications), and particularly the band structure explanation (if you have it!)... Indeed, I heard that the x-ray telescopes were made of parallel mirrors...

Can anybody tell me the significance of the band origin for a P(Q)R structure in the ultraviolet region of a molecules spectrum? In standard vibrational spectra, I understand that its roughly the harmonic frequency of the oscillator, and that the rotational constant can also be found from...

Dear All I am having problems with how to draw band diagrams with band bending for Schottky Barriers and PN junctions. My issue is that I don't know how you determine which Fermi level remains fixed at its equilibrium level and which Fermi level moves to align with it when the two materials...

Does a PNA show FFT If I'm looking at gain across a band on a PNA could one say that I'm looking at an FFT or is that complete nonsense?

What does it mean if the valence band of a n-type semiconductor shifts towards lower binding energy after deposition of a metal on-top. Is it simply charge transfer from the metal towards the semiconductor or vice versa? I mean , the valence band is fully occupied, so there are no states for the...

Elastic Potential Energy of Elastic Band* Homework Statement A stretched elastic band of mass 0.55 g is released so that its initial velocity is horizontal, and its initial position is 95 cm above the floor. What was the elastic potential energy stored in the stretched band if, when it lands...

Hi! Is anyone familiar with generating band structures from DFT simulations? I am using graphene, and am trying to plot the electronic structure at the high symmetry points (K, M, and gamma). Grappling to understand this theory, my questions are: 1. Is the location of the high symmetry...

When we say generally TiO2 band gap energy, is it meaning direct or indirect band energy? Some papers show only direct BG or indirect BG or both. Is it right that one semiconductor has one of direct and indirect BG. I am a little bit confused.

ok let's say i have a semiconductor like germanium with band gap of around 0.67eV at rtp. so this means that i need around 0.67 x 10-19 J of energy to cause valence electrons to jump to conduction band right? do i use the formula E = 1/2 kT to relate this energy to temperature? so i...

Hey I am doing a practical on the spring constant of a rubber band, we have studied hooke's law and from that found that the spring constant of a spring is well F = -kx so F is proportional to x. While i did the same experiment with a rubber band, hung it on a clamp connected to a retort...

I need to calculate the density of states for a dispersion relation which is like the free electron dispersion, but with one effective mass in the kx, ky directions, and a different effective mass in kz. So I need to integrate the inverse gradient of E(k) over a surface of constant energy, ie...

Situation: I'm having issues with the iliotibial band in my left leg, and it is preventing me from running. I've been icing it daily and doing lateral leg raises along with various stretching exercises. I've also just purchased a foam roller (didn't know what the heck they were until now)...

Warning: I'm not a practicing chemist. Answers in as-simple-as-possible language (but not oversimplified!) would be greatly appreciated! I'd like to know if the chemical properties of a solid can be affected by conduction band electrons. I assume that, in the majority of cases (and perhaps...

Hi, I have a question regarding Energy band. The energy band of a simple cubic semiconductor crystal with a lattice constant b can be represented as in the following function: E(k) = E0 + E1[cos(kxb) + cos(kyb) +cos(kzb)] where E0 and E1 are independent of the wave vector k. i)...

Homework Statement An acoustic signal consists of three tones, each of different frequency and different effective pressure amplitude: P_1=5\times10^{-2} Pa,P_2=7\times10^{-2} Pa,P_3=.1 Pa, and f_1=104 Hz,f_2=190 Hz,f_3=237 Hz. Find the intensity in the 100 to 110 Hz band. Homework...

Hi, I've encountered some problem during solved the band pass filter and twin-T notch filter. I don't really understand what the question exactly meant...hope can get some idea in here..thx 1.) A signal conditioning system uses a frequency variation from 6 kHz to 60 kHz to carry...

Why a rubber band gets warmer when repeatedly stretched and relaxes? Where does the gained ME comes from? Besides, does rubber band obeys Hooke's Law?

　 Is the Energy Band of Wood vs Crystals similar? 　 As I understand it. In crystals the interaction of the atoms are more intimate.. meaning all the atoms in the crystals can influence one another which produced solid energy band. While in wood, the distance are further and hence the...

Wikipedia says that "in band theory, energy bands are actually made up of many discrete energy levels which are too close together to resolve. Within a band the number of levels is of the order of the number of atoms in the crystal, so although electrons are actually restricted to these...

hi guys, i came across this problem in my material science class. can anyone help me with this problem? thanks! ** (-> an electron) Ec ___________________________ }-> 0.2eV, from Ec to electron Ec - Ev = 1eV Ev ____________________________...

Hi What could be the band diagram of pn-junction diode at very low temperature where dopant ionzation is completely frozen out? Would it still be like the band diagram at room temperature?

If you stretch a rubber band around a pole, the band exerts a force onto the surface of the pole (F1 in figure 1). Is it possible to calculate this force if I know the force needed to stretch the rubber band to the same total length as the circumference of the pole? That is to say: 1. I know...

Homework Statement A frequency band from 76 MHz to 86 MHz is available for wireless transmission. Design a frequency division multiplexing system with 2 MHz wide channels and 2 MHz guard bands (assume that guard bands aren’t necessary at the lower and upper ends of the band). Indicate...

If not: then how do the holes in a semiconductor manage to conduct electricity (if they can't travel through the solid)? If there are: 1) then what is the difference between the valence and the conduction band? 2) then why do the electrons in a semiconductor need to reach the conduction band to...

Hii, I was wondering whether there is any correlation between the energy eigenvalues of a single atom (say He) with the electronic band structure of a collection of He atoms. for example, for He atoms the lowest energy would be the ground state, with 2 electrons. So will the lowest band for a...

for metals the conduction and valence bands overlap. So how do you distinguish between the conduction and valence bands? How do you find out the lower limit of the conduction band and the higher limit of the valence band? Or is it the case that the highest conduction band in a metal goes from...

Hello, In my book it says that semiconductors have a full valence band and a fermi energy somewhere in between that valence band and the conduction band. But its two examples of semiconductors, crystals of Silicon or Germanium, have a 3s^2 3p^2 resp. 4s^2 4p^2 outer shell, so surely they...