Band Definition and 481 Threads

When electrons leave the valence band and jump over the gap to the conduction band, what is the density of the remaining holes? If 2.5 electrons/cm^3 leave the VB to the CB, will the density of remaining holes be 2.5 electrons/cm^3? To me it is logical, but I am wondering if mass of electron...

My question is as follows: if you place an insulator into an applied field, the only thing that will happen is that the potential energy of each band will shift, according to the potential that it is in. Why is this exact same thing not what takes place in conductors? Why do the electrons at the...

I'm studying a two dimensional lattice with delta functions at the lattice points. When I diagonalized the hamiltonian I noticed that if I kept the dimension of my matrix less than 5 I would get band gaps at all the BZ boundaries. However, if I increased my matrix to a dimension 5 or higher...

Hi everyone:) Is there anyone who has worked on the phenomena near the band edge of photonic crystals? for example spontaneous emission near the band edge? there are lots of articles specially from Sajeev John " spontaneous emission near the edge of a photonic band gap" Phys.Rev.A vol50 num 2...

I am struggling in understanding what the band structure (E vs. k) diagram tells me. Let's say I have the following material: http://www2.warwick.ac.uk/fac/sci/physics/current/postgraduate/regs/mpags/ex5/phonons/indirect_absorption/indirect_absorption.bmp...

Homework Statement For a stretched rubber band, it is observed experimentally that the tension f is proportional to the temperature T if the length L is held constant. Show that: a) The internal energy U is a function of temperature only b) Adiabatic stretching of the band results in an...

I'm trying to reconcile how a built-in potential can form in a semiconductor heterojunction in which there is a significant band cliff to majority carrier diffusion from both sides of the junction i.e. there is a cliff which should block hole diffusion from the p-type as well as a cliff which...

Hi,there are many literatures concered with band decomposed charge density(As an example,see FIG.3 in PHYSICAL REVIEW B 78, 235430 2008). For condution band,there should not be charges or electrons when the system is in the ground state,but,those literares still show a band decomposed charge...

Hi Guys, i need your help, where can i download free articles about the band gap of semiconductor materials (like copper (II) oxide). don't mention sciencedirect and arxiv, because i already explore that, and they provide limited research articles. thank you.

Homework Statement Consider an n-type Si (Eg =1.1eV, ED=EC, εr=11.8) with a bulk doping density ND=1×1017cm-3, a density of acceptor type surface state 1×1014 cm-2 and these states are at the middle of the band gap. Evaluate the amount of: a) band bending b)depletion layer thickness c) density...

The ISM band is a set of frequency bands from about 6 kHz to 246 GHz; see http://en.wikipedia.org/wiki/ISM_band#ISM_bands. Is there a design that will block all of these bands? A guess is in the attached file: each box is solid metal or wire mesh, and the boxes nest in a Matryoshka-doll fashion.

Hi, I'm a second year Design Engineering student. This year we're having some basic physics class. We're doing projects on potential energy at this moment. I'm having a problem with the following; The assignment: The teacher assigned us that only 6 Joules of potential energy may be used to...

Homework Statement Hi everyone, I am trying to construct qualitative band diagrams and I think I have confused myself. I am not sure on how to figure out what the electron configurations are of the orbitals when k=0. I get that at k=π/2 it is the opposite state but I can't seem to figure out...

I'm trained in Condensed Matter Physics, and I'm trying to learn EE. The concept of band bending always baffled me a bit. Here's why: The band edge bloch states are delocalized over the whole of the crystal, and have fixed given eigenvalues. How can this eigenvalue change over the length of the...

Hi! I am having difficulty grasping what band theory actually is, especially what the bands are and the energy gap between them. Are they probabilities? Shared electrons between atoms such as in metallic bonding? What is the difference between the conductor band and the valence band? I think I...

Is there any simple justification about graphene having no band gap? How bout its linear E-K? Why bilayer graphene has a quadratic E-K and electric field can open a band gap there? I do not completely understand the broken symmetry argument? Also Why MoS2 which has similar structure, do not...

Hey guys, So this is entirely theoretical and I am just curious if its possible and how it could be done. But how can you go about changing the bandwidth of a particular signal? So a lot of times we have a signal at a given frequency, and there might be a little bit of aliasing into other...

I have done the computations of band structure of cobalt adsorbed graphene. In 3x3 supercell of cobalt adsorbed (one cobalt atom) graphne, there is opening of band that is gap between conduction and valence band but there is no gap in 4x4 supercell of cobalt adsorbed graphene. I've done this in...

Does this mean if I had a rubber band and weighed it, then stretched and weighed it while being stretched out, that it would weigh more at that time? Since at that time it has stored energy, which equates to mass?

Homework Statement "You have a 1 km long rubber band with one end attached to the wall, and the other in your hand. The bug begins to crawl towards you on the rubber band, starting from the wall, at a rate of 1 cm/sec. As he crawls the first centimeter you extend the rubber band 1 km; when he...

i search all over the web but i cannot find the definition. Although I find all the literature saying that metal have valence band and conduction band overlapped, (and I cannot find a metal example with valence band and conduction band not being overlapped), I wonder if there is a...

According to solid state texts in Brillouin zone borders where diffraction condition satisfies we have a band gap. However I usually see Band gaps which are located in the center of Brillouin zone. Please correct me if I am wrong.

My understanding of the atomic structure is that electrons can gain energy in quantas, so that's why we have orbitals with sharply defined energy around the nucleus. One would logically think that every atom of the same element has the exact same orbitals with the exact same energy of orbital...

I am reading about the ionization energy in semiconductors and came across this thing that for Silicon, the ionization energy is lower than its band gap energy. I don't understand how can this be?

how the dispersion relation(i.e. E-k relation) affects carrier mobility in metals or semi-metals?

Could anyone please explain the concept of Band offset?

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...

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...