What is Energy gap: Definition and 31 Discussions

In solid-state physics, an energy gap is an energy range in a solid where no electron states exist, i.e. an energy range where the density of states vanishes.
Especially in condensed-matter physics, an energy gap is often known more abstractly as a spectral gap, a term which need not be specific to electrons or solids.

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  1. hagopbul

    B Viewing IR radiation with cell phone cameras

    Hello All: i saw some youtube videos on testing IR controllers on normal with no add ons Cell phone camera and the cell phone screen is showing signal emitted by the IR LED of the remote controller , how the cell phone camera sensor are able to register a signal from an IR LED , the pixle in...
  2. Rzbs

    I Importance of the energy gap in electronic transport properties

    In the solid state physics by Ashcroft & Mermin, in chapter 9 there is a paragraph that I would be grateful if anyone could explain it more for me. The paragraph is: As it said in chapter 12 it will be seen. I read chapter 12 but unfortunately I can't understand what exactly it want to say...
  3. Amitkumarr

    Chemistry HOMO-LUMO energy gap of compounds

    According to me Option A is a correct option because as the energy difference between two atomic orbitals increases, their interaction, and thus the value of E (or E*) decreases. Here, E is the energy difference between the bonding molecular orbital and the atomic orbital of lower energy , while...
  4. A

    Energy gaps for quasi-free electrons in a 2D lattice

    Hi! Situation: quasi-free electron in a 2D lattice, considering atomic potential V(r) = exp{-|r|/b} (r is the distance from the atom) I'm trying to compute the first five energy gaps at point (10), firstly I don't understand the meaning of calculated 5 energy gaps at one point and usually we...
  5. G

    A Energy gap between energy bands in solid state physics

    I know that Bragg reflection in solid states at the edge of e.g. the first Brillouin Zone causes standing waves at these edges, which creates a gap between the energy bands. In this picture below you can see the probability density of a symmetric (+) and anti-symmetric (-) standing wave. The...
  6. S

    Energy Gap of 2 states in a deep rectangular potential well.

    What is the energy gap between the ground state (n=0) and the first excited state (n=1) of an electron trapped in a deep rectangular potential well of width 1Å?
  7. G

    Semiconductor resistor in series with a capacitor -- Energy gap

    Homework Statement Consider a circuit that consists on a resistor of an intrinsic semiconductor R and a capacitor C in series. The voltage between the terminals of the circuit is U, which is an alternated sinusoidal voltage. U1, which is the voltage in the capacitor as a phase difference of 30...
  8. T

    Energy gap between orbitals and stability

    We know that the lower the energy gap between bonding and antibonding orbital the easier it is to break the bond making it unstable. However, in a conjugated double bond, the overlapping of wavefunctions cause the energy gap between the bonding and antibonding orbital go down. Then why...
  9. A

    I Understanding the Energy Gap and Topology in Topological Phase Transitions"

    As a condition for a topological phase transition it seems that there must be an energy gap that closes and reopens. I have seen this many places, but never an intuitive, easy explanation. Can someone give that?
  10. carllacan

    How can I calculate the energy gap?

    Hi. I am sometimes asked to find the energy gap at a point k in the reciprocal space of a lattice with a periodic potential. From what I've read I understand that I have to 1) use Schrödinger's equation in k-space, from which I 2) get a system of infinitely many equations, and then 3)...
  11. U

    Can someone explain peierls distortion/transition to me?

    Peierls distortion states that for a 1 dimensional polymer (like polyacyteline) with lattice spacing a they should have a half-filled conduction band, why? And how does changing the lattice space to 2a cause it to form an energy gap? In my mind it should be the same as the first case...
  12. S

    How could change the energy band gap(E-K) using the strain?

    Hi! I'm sung dae with tensile strain, energy band structure could be changed. bang gap decrease with compressive strain, energy band structure could be changed. bang gap increase but I'm not sure why it could be changed .. Is there someone who explain in detail ? thanks. have a nice day! :)
  13. E

    Explaining the Absence of Band Gaps in Superconductors

    Hi all, I am currently writing a report about superconductors, and am currently reading about how the band gap shows that single electrons are not the charge carriers responsible for superconductivity. However, I was confused when I read that electrons are fermions and as such there are no band...
  14. U

    Energy gap between brillouin zones?

    Homework Statement Consider a monovalent 2D crystal with a rectangular lattice constants ##a## and ##b##. Find expressions for the fermi energy and fermi wavevector in 2D. Show that the fermi surface extends beyond first zone if ## 2a > b\pi##. If the crystal is now divalent, estimate the...
  15. A

    Semiconductor Energy Gap: Silicon Explained

    Hello everyone, I have a quick question about the energy of the silicon. I know that, as a semiconductor, the silicon has an energy gap between the valence band and the conduction band. But according to this image ...
  16. G

    Why do doped semiconductors have a decreased band gap?

    Could anyone please explain why doped semiconductors show decrease of the bang gap in comparison to the pure semiconductors. Web/literature links to relevant information will be appreciated. Thanks.
  17. K

    What is the energy gap of Titanium Nitride (TiN) and is it indirect or direct?

    Hello all, Does anyone knows what is the exact energy gap of Titanium Nitride (TiN) film? Is it indirect band gap or direct band gap? From literatures, I've found that the band gap for TiN is around 3.35-3.45eV. . May someone could suggest the specific band gap for TiN? Thanks.
  18. E

    Variation in effective energy gap?

    Hi, I've worked out that for the particle-in-a-box model (square well) the energy E E = 3h^2/8mL^2 where m is the effective mass of the electron. The next question asks Hence derive an expression for the variation of the effective energy gap in the quantum dot as a function of its...
  19. J

    Can we measure the band energy gap from Fluorescence spectra

    Can we measure the band energy gap from Fluorescence spectra? If yes, in what way? the excitation spectra or the emission spectra or both Is there a good reference on this subject specifically :smile:
  20. E

    Energy Gap of Intrinsic Semiconductors: Temperature Dependence

    Energy gap dependence on temperature for intristic semiconductors (Si,Ge) I need help on this topic, where to find text about this, and models that describe it (Varshni's model, linear model,...)
  21. N

    Energy gap calculation for semi-conductors.

    Homework Statement Most solar radiation has a wavelength of 1 µm or less. (a) What energy gap should the material in a solar cell have if it is to absorb this radiation? (b) Is silicon an appropriate solar cell material? Explain your answer. Homework Equations f = c/lambda E =...
  22. L

    Energy gap from conductivity- temperature graph

    Homework Statement Hi, I have some values of conductivity in some temperatures. 0.01 at 400 Kelvin 10 at 600 K 70 at 700 K 1000 at 1000 K And I'm asked to find the energy gap of this intrinsic semi- conductor. Homework Equations The Attempt at a...
  23. H

    Energy Gap of Electron in Dirac Comb Potential

    Pg 202 of Griffiths Introduction to Quantum Mechanics Homework Statement Hi, I am trying to solve a question involving band structure of solids... The electron is placed in an area filled with positive ions which is represented by a dirac delta potential... Homework Equations The...
  24. Y

    N-carriers, number density, energy gap E_g, temperature

    hi folks, I've gotten most of this problem but for one part. I've learned quite a bit reading about the physics involved here on the web, but for all I've learned when I apply it, it doesn't work (ie give the right answer). So, I'm missing something. Homework Statement In silicon, E_g =...
  25. A

    Find band gap, energy gap for semiconductor using software

    Homework Statement I'm using Exciting software, which run in Linux for windows (virtual). My task is to find band gap, energy gap and so on for semiconductor material using this software. I have to find band gap, energy gap and so on properties for Thallium Gallium Phosphide (TlGaP). To get...
  26. E

    Understanding the Origin of Energy Gap in Kittel's Book

    [SOLVED] kittel page 166 Homework Statement In Figure 3 of Chapter 7 of Kittel's Solid-state physics book, it says that this is the key to understanding the origin of the energy gap. However I do not understand why. It seems like if you take the expectation value of either |\psi(-)|^2 or...
  27. P

    What are the energy gaps of semiconductors used in CD, DVD, and Blu-ray lasers?

    The lasers used to "read" CDs, DVDs, and Blu-ray discs operate at 780 nm, 650 nm, and 405 nm, respectively. These are produced through semiconductors. Find the energy gap needed for each laser. (Blue-ray discs can have higher information density because of the shorter wavelength). Ok. I...
  28. J

    Exploring the Meaning of k, k1, and k2 in Energy Gap Theory

    Hi, I just get confused on the some definations in the energy gap theory. in the equation \cos {k_1a} \cos{k_2b} - \frac{k_1^2 + k_2^2}{2k_1k_2} \sin {k_1a} \sin{k_2b} = \cos {kd} where \frac {\hbar ^2 k_1^2}{2m} = E \frac {\hbar ^2 k_2^2}{2m} = E - V however the...
  29. N

    What Is the Energy Gap in Superconductors and How Is It Measured?

    I need some clarification on what is meant by the energy gap of a superconductor. From my own understanding, is is caused by the manifestation of cooper pair, and hence can not obey fermi-dirac statistics, but abides with bose-einstein statistics. However, I feel that this reasoning is...
  30. L

    Effects of Temperature on Germanium Conductivity & Energy Gap

    The conductivity of pure germanium increases by 50% when the temperature is increased from 20 degree C to 30 degree C. What is the energy gap E_g between the conduction and the valence bands of germanium? b) For silicon E_g = 1.1eV, what is the percentage change in the conductivity for the...
  31. P

    Energy gap and bragg refraction

    I'm asked to prove that the condition for the existence of an energy gap at the boudnry of the Brillouin zone on a 1D lattice is equivalent to the condition for Bragg refraction. I don't understand this question. Doesn't an energy gap arise solely when there is a potential? Meanwhile, Bragg...
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