Energy gap Definition and 31 Threads

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...

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...

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...

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...

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...

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?

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...

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...

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?

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)...

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...

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! :)

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...

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...

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 ...

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.

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.

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...

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:

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,...)

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 =...

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...

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...

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 =...

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...

[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...

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...

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...

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...

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...

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...