What is Band: Definition and 531 Discussions

Hi, I perform my post-processing and analysis of data from silvaco in MATLAB and would like to export values from the .str file to a file that can be read easily into matlab. Does anyone know of a way to do this programmatically? I can do it in tonyplot, but I've got everything else scripted...

Hello i need to know what should i do, Consider i have a box, top half and bottom half. so now i have to hold the top half and bottom half together with the rubber band then how do i know what rubber band will be enough to exert force so that both parts of box are hold together. also i...

Hi, Iam trying to understand the differences between metals, semiconductors and insulators. Regarding the conductivity properties. Iam new to this area so please correct me if I am wrong. I may be simplifying things now; 1) If I put a voltage over a solid, I only measure a current if...

I am learning Ashcroft's Solid State Physics. In the Electrons in a Weak Periodic Potential, I got some problems. 1. Ashcroft mentioned in the footnote: The reader familiar with stationary perturbation theory may think that if there is no exact degeneracy, we can always make all level...

Homework Statement The equation of state for a rubber band with temperature T is \mathcal{F}=aT\left[\frac{L}{L_0}-\left(\frac{L_0}{L}\right)^2\right] Where \mathcal{F} is the tension, L is the stretched length and L_0 is the unstretched length a) Write the Central Equation for the...

Question Statement Polyacetylene can be modeled naively as a one dimensional chain of carbon atoms each separated by a lattice constant 'a'. Taking the electrons in such a system to be nearly free and applying a weak periodic perturbation we can derive a dispersion relation giving a curve...

I am reading Martin Crossley's book, Essential Topology. I am at present studying Example 5.55 regarding the Mobius Band as a quotient topology. Example 5.55 Is related to Examples 5.53 and 5.54. So I now present these Examples as follows: I cannot follow the relation (x,y) \sim (x', y')...

why do the atoms in excited state alone could emit line spectra?can't they emit when they are not in gaseous state? why only molecules can emit band spectra?can't atoms emit them

Edit: I've made some progress on this one, and I now understand that the valence and conductance bands are composed of molecular orbitals contributed by each metallic atom joining the molecule. For example, three lithium atoms would contribute three total molecular orbitals, resulting in three...

Homework Statement For the rubber band model, calculate the fractional change in (L-L0) that results from an increase δT in temperature, at constant tension. Express the result in terms of the length and temperature. Homework Equations U=cL0T τ=bT((L-L0)/(L1-L0)); τ=tension, L1=elastic...

Imagine an infinitely stretchable elastic band where one end is attached to a vertical wall and the other on a horse, as shown in figure. On the elastic band, very close to the wall, there is a snail. If we assume that the initial length of the band is L, and the horse and snail start moving...

Homework Statement This isn't for a homework problem per say, though it is a coursework question. I'm writing a lab report on Multi-Quantum Well Laser Diodes and am trying to explain the basic semiconductor physics behind it. As such I need a diagram of the band structure. Homework...

Since all the directions are equivalent in an isotropic crystal, can we deduce that the energy band is exactly spherical?

Can anyone elobrate what is the (specification, durability, safety, and performance ) for band brakes used in conveyor system...??Your help is much appreciated. Thank you.

Hello Physics Forums. Our professor asked us to do a program on constructing the band diagram of BCC and FCC for nearly free electron approximation. what is the best algorithm i can use? i can program a bit, it's just the step-by-step method i am not sure of. thank you

My book has a discussion of how the Bragg model can explain the origin of energy band gaps in solid. I have attached the relevant part of this discussion. I would very much like if someone could help me understand what it's basically trying to say. Facts: 1) In the free electron model, the...

Why can't electrons move inside the valence band? Is that the Pauli exclusion principle - and is it true that the electrons can't move even when the valence band is only partially filled?

Homework Statement An elastic band is hung on a hook and a mass is hung on the lower end of the band. When the mass is pulled downward and then released, it vibrates vertically. The equation of motion is s = 2 cos t + 3 sin t, t≥0, where s is measured in cm and t in seconds. (Take the positive...

Homework Statement Consider a pn junction in Si at 300K (other parameters given), with doping NA = 1021/m3 and ND = 1023/m3. Assume all impurities are ionized. On this basis find the Fermi level on each side. From this find the band bending VB and make a sketch of the pn junction. Homework...

What does "valence band mixing" means? Could you provide me some reference about it?

Hi, Which of ZnS and CdSe will have the larger band gap energy, explain. The answer is given as Zinc sulfide will have a larger band gap energy than cadmium selenide. Both are II-VI compounds, and Zn and S are both higher vertically in the periodic table than Cd and Se. In moving from...

For an electron gas generated in the inversion layer of a semiconductor interface, my book gives the conduction band density of states for the two dimensional electron gas as: ##g(E)=\frac{L^2m^*}{\hbar^2 \pi}## Where m* is the effective mass of the electron. I can't follow how this was...

Is it possible for a disordered or amorphous structure to have band structure? I understand derivation of bands from Kronig-Penney model. E.g. does amorphous silicon have a band structure? While amorphous silicon oxide does not have a band structure?

Hello everyone ! In below picture we can see band bending in semiconductor at SiO2 interface, as show in picture how charge's BE(binding energy) and KE(kinetic energy) are changing..?? Or what happens to charges total energy in band bending ..?? \\

Hi All, This is part solution, part request for peer review. I wasn't able to find a model for the motion of a particle dropped onto an elastic band so I've created my own in Excel (attached). Note that the model is primarily focussed on the motion of the particle, and not the elastic...

(To the moderator,please don't shift to the Homework thread list.This thread explores the conceptual part of gear changes) A 2 liter engine has T(max)=185Nm at \omega_e=4500 rpm, has a manual gearbox with the following gear ratios: n1=3.42, n2=2.14, n3=1.45, n4=1.03, n5=0.81, nr=3.46, nd=4.06...

Hi, I want to design an ADC with these specifications: Fin = 20MHz BW= 20MHz ENOB > 4 Power consumption P < 1mW Could anyone suggest me some ADC for this kind? I have searched a lot in IEEE but there are only two ADC with SAR ADC and time-interleaved ADC. The ultralow power consumption...

How does one interpret band structures (i.e. E,k solution pairs for a given Hamiltonian) for a non-primitive cell? I was looking at these slides: http://www.tcm.phy.cam.ac.uk/castep/CASTEP_talks_06/clark2.pdf Slide 9 has the "normal" silicon band structure obtained with a primitive cell...

Why are insulators supposed to possesses a "conduction band", even if usually empty? If you do take the energy to cross the "band gap" and displace an electron, just why should it become delocalized/conductive? Couldn´t it just lose energy rapidly by exciting phonons until it gets trapped...

Homework Statement Hi guys, I'm trying to solve questions from past exams; here comes one. There are 2 possible fundamental equations for the rubber bands: ##S=L_0\gamma \left ( \frac{aU}{L_0} \right ) ^{1/2} -L_0 \gamma \left [ \frac{1}{2} \left ( \frac{L}{L_0} \right ) ^2 + \frac{L_0}{L}...

Does the (intrinsic) Fermi level of an insulator HAVE to lie very near the middle of the band gap? I know it might deviate slightly if electrons and holes have different effective masses, e.g. in Si. But can it be radically different? For example, are there insulators with 5 eV band gaps that...

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:

Hello! I'm having my materialphysics exam in a few days, and looking some of the older exams I saw that there are many times questions about band structure and density of states. More specifically there might be a picture of some band structure plus the density of states, like this. Then...

Homework Statement I just have to calculate midband gain for a typical NPN BJT. The transistor model is a 2N3904 Have I calculated something wrong?? My gain is 0.748

Homework Statement Please see attachment. Homework Equations The Attempt at a Solution Not really a homework problem. This is 1 of my exam question which I believe I had the right answer but my professor insists that he has the right one. I started by equating work done, W =...

Hello, I am writing a technical essay on solar cells and I am having trouble finding out exactly what the valance and conduction band actually are. It's a bit elusive, the textbooks I am using simply state the two bands without explaining what they are. If anybody could provide any...

As my title states, I want to understand why electrons in the conduction band can move around so easily in the material. Is it due to the presence of many closely spaced (blurred out) energy levels which make it easy for the electrons to move around? Or are the electrons undergoing some kind...

Hello, Is there an established relationship between the diffraction intensity that a sample produces with its band structure? Thanks

Is there an easy way of designing a band pass filter whose pass band could be varied over a certain band?? The pass band is in MHz range. Thanks

I mean why is it that the eye evolved to detect "visible" light instead of, say, microwaves. What is it about the visible light spectrum?

Hi! I'm reading about band structure and conduction in regular crystals and semiconductors, and I've hit a few confusing points my book doesn't explain well enough for me. In one part, they're explaining conduction in a 1D crystal with lattice spacing a (and therefore reciprocal lattice...

What are the parameters affects the band gap in a band structure?

The absorption spectra of some materials appear as the absorption bands (for example: TiO2 powder) while the other appear as the absorption peaks (for example: Quantum dots). Please explain why they are different?

Apologies if this is rather trivial. I'm having a hard time wrapping my mind around the mathematics of energy bands and periodic potentials. I understand that an electron in a periodic potential will be of the form \phi_k(r) = e^{ik.r}u_k(r) . This wavefunction has periodicity of the...

Assume that a mass is attached to an elastic band and then allowed to oscillate. Would the formula for the period of oscillation be that as the same of the formula for the period of the oscillation for a spring. T=2∏(√m/k) ?

Boundary of a Mobius band - I think S1 V S1, everyone else says S1?? Hey I am having a huge problem! There are a few problems where I'm using Van Kampen's theorem and for one part of the problem I need to compute the fundamental group of the boundary of the Mobius band. Everyone keeps telling...

Hello , about the band theory I was confused some how seeing the attached image I ask :- 1- when the atoms are far away we take a single atom alone as a system , but when atoms get closer we identify them all as the system , right ?! 2- why do we use the word " splitting" , why...

n is the band index and k is the electron wave vector. Now is energy band specified when for each n , k runs through all the values available that specify periodic boundary conditions ? But in Ashcroft Mermin , it is also given that for a given k , there exists an infinite family of solutions...

Suppose an electron in a crystal(periodic potential) has the Bloch wave function \psi (k_0,x) at t=0. Applying a constant electric field E(at t=0), the electron would still have Bloch-type wave function at any time t with k(t)=-(1/\hbar) eEt+k_0. Now According to this formula for k(t), one can...

Homework Statement What are the color band colors and associated band values for a 1kΩ resistor The Attempt at a Solution resistor color codes are read like so: ab*10^c±tol 1kΩ=10*10^2 a=1, b=0, 10=c Now I get confused. What should the tol be?