What is Band: Definition and 531 Discussions

A rectangular semiconductor has dimensions of 2x2x1 mm, the unit cell is cubic and has edge length of 2 angstroms. find the number of states in one band of this semiconductor. What I have done: volume of unit cell = (2x10^7)^3 = 8x10^-21 mm^3 volume of semi conductor = 4 mm^3 number of...

Dear colleagues, I am trying to deal with quantum-chemical calculations of metal-containing coordination polymers, and I have a question which turned out to be difficult to me: If a system includes copper atoms, which implies that it has 'unpaired' electron, how to describe a band gap in...

Interesting article from SciAm on transforming a rubberband into a trefoil knot and how math in the knot world of zero thickness says no but the real world says yes. http://www.scientificamerican.com/article.cfm?id=mathematical-impressions-can-you-turn-rubber-band-into-knot

Homework Statement Describe the ”conduction band” in Na metal. Why it is half-filled and non-magnetic? The Attempt at a Solution Na has electron configuration: [Ne]3s^1 the 3s band is highest in energy and is the conduction band for Na. since Na has 1 electron in the 3s band, and...

Homework Statement A person performs an exercise where he pulls a rubber band stuck in a wall to later return it to its resting position. The two movements forward and backward, is equivalent to one practice cycle. They both happen in a horrizontal plane with a constant velocity of v=0.5ms-1...

I've been looking on journals and textbook, as well as internet. Does anybody know if there is an equation to find out the value of direct optical band gap and indirect optical band gap? What is the difference of optical band gap, direct optical bandgap and indirect optical bandgap? also...

In n-type semiconductor, Can electron stay between donor energy level and valence band? Can I say that the donor energy level here refer to the Fermi level? Thank you

Electrons in the conduction band of metal will be attracted by the nucleus of atom? I wonder why there can be electron in the conduction band of metal at 0K .At 0K , all electron should lose its energy as(3/2)kT=0. Thank you

Hi, Does anyone have an intuitive idea of why it is always the valence bands split under spin/orbit coupling, but not conduction band? (or a much smaller splitting than valence band) I know through tight-binding calculations, if I plug in numbers correctly, conduction bands always have...

the 2 signals shown are used for modulating ( DSB-SC) a carrier with frequency fc. Now i need to find the similarities and differences between their time domain representation. Clearly the both will have same envelope. Now i tried for the difference part but could not find it. One possibility...

Can a hole go to conduction band? In p-type, the hole is above the fermi level, lower than conduction band, higher than valence band, how can this be happened? And will this happen when the p-type is at 0K

This is regarding youngs elastic modulus I need help as I am trying to figure out the stress and strain of an elastic band when a force has been applied - in youngs modulus. Does anyone know how to go about this?

Please link to execrable songs by musicians that should have known better. Some "songs" like "I'm so glad" by Cream appear to be album-fillers instead of serious music. Clapton has gold records on his wall, but this stinker causes me to change the channel or hit "next" on the CD player...

Homework Statement Find the density of carriers N in the conduction band of intrinsic silicon at room temperature Homework Equations lower integrand Ec, upper integrand= Ec+1*qe, Eg=1.12eV, Ev=0 Ec=Ev+Eg Ef=Ev+Eg/2 m*n=1.08*(9.11*10^31), T=300K...

I am a little bit confused about the upward band bending in a n-type Si which is in contact with a metal. Suppose that electrons flow from Si to the metal to align the chemical potentials such that positive donor levels become depleted. In equilibrium one ends up with a negative charge density...

Okay, I am working on my physics lab, and I have a few questions regarding it. First, we are asked to make a prediction: "Predict how you think the presence of a rubber band will affect the force felt by the force probe from the rubber band compared to masses hung directly from the hook?" My...

hello, is there anyone who can help me in the band gap calculation. my situation is that: I can calculate the band gap of sigle crystalline graphene, because i know the high symmetrical pionts of the first Brillouin zone of an hexagonal crystalline(M-G-K-M). But the problem is that...

Homework Statement The first vibrational band in the absorption spectrum of H2CO is at 28871 cm-1. The first two bands in the emission spectrum (from v'=0 level) lie at 27021 cm-1 and 24687 cm-1. Explain these observations. Determine the band origin of the electronic transition and the...

I found a lecture on the internet where a LCAO assumptions are used to calculate the phonon band structure. In this lecture (Here) we can find that the true Hamiltonian: H = \frac{p^2}{2m}+V_0(x) where V_0(x)=V_0(x+a) is replaced with the following aproximate hamiltonian: H\cong \sum_n...

I search it on google, books, articles, everyone cite it but no one explain fully what it is. If you can: bibliography please! Thanks a lot!

In a metallic system, the Fermi level is crossed either from the conducting zone into the non-conducting zone or vice versa. Is there an interpretation one can give to the direction of the crossing? In other words, if the 1D band gap diagram shows the fermi line is crossed from the...

Homework Statement Calculate the number n_0 of electrons per volume unit in the conduction band for the lithium, copper and aluminium. Compare this result with the number of electrons of valence per volume unit of these metals. Homework Equations None given, no ressource either...

Hi, I am trying to model a type II GaSb/InAs superlattice through the 8 band k.p method in MATLAB...I have studied general quantum mechanics but have no background in coding. I need to calculate the bandstructure and the CB,VB wavefunctions...can anyone provide me with a sample code for better...

In band theory of solids, when an electron's wave vector lies at the first brillouin zone border, it satisfies the bragg condition and there is some forbidden region for that wave vector. I like to know what happens for such these electrons that they can not have some energies in the forbidden...

As we know, in intrinsic semiconductors the fermi level is halfway between the valence and conduction band. and The fermi level is the level in which the most energetic electron settles at T=0. but my question: How can the fermi level be in a forbidden region in intrinsic semiconductors? or...

I need some help with FREQ. on the MHz Band and the kHz Band? If I am on a Radio that displays the FREQ 909.5 MHz I know I would write this out as 909,500,000 Hz and this is 9 Hundred and 9 Thousand 5 Million Herts Am I right?

I am new to solid state physics, having been in computational chemistry (quantum mechanics) for the larger part of my career. Hence have a lot of newbie like questions that are not easily answered by google/wikipedia searching. 1)In viewing a 1-dimensional band gap diagram, crossing the...

I was reading about electronic band structure in wiki and I didn't understand why the conduction bands are necessary for flowing current in a material. If all the atoms in a solid shares valence band and all its eletrons, then these electrons may travel through the solid. I didn't get why the...

Hi, I'm studying for a course in semiconductor devices, involving pn-diodes, schottky-diodes and mosfet transistors. Just wondering if there's any good online resource that demonstrates specifically how to draw energy band diagrams for the various devices in various situations (applied...

Hello everyone, I have finished high school not long ago, and haven't start my uni. So I take this time to read some physics. I have no one teachs me, the only book I have is 'Giancoli's PHYSICS'. Its a good book (discriptive but not mathematical, which suits me as I haven't done much...

In crystalline material, bands arise due to the interaction of electron waves with periodic potentials. Can anyone please explain the origin of energy bands in non-crystalline material..couldn't find relevant links on Google.

I'm reading a paper on photovoltaic hydrogen production and the author claims that for reasonable solar efficiencies the band gap must be less than 2.0eV. This I understand. My question is how will it effect the photon absorption if the band gap is much smaller. Say the band gap energy is...

Hello! If I run an agarose gel of undigested DNA of an organism with more than one chromosome, and obtain one band (slightly smeared), what does this mean? The chromosomes aren't all the same length (some might be approximately half the size of others). Is it because they all become...

Hello, I just watched this video, where Dr Brattain talk about semiconductor physics and I thought about what I learned in my solid state physics course, namely band theory. I have several questions : 1)The explanation in terms of chemical bonds given by Dr Brattain (around 10mins) seems a...

I am considering making a yagi antenna for a wifi adapter and I have been warned about some possible side effects that I wanted confirmed or disproved.. I read somewhere that the 2.4GHz band also is the resonant frequency of water and is used by microwave ovens, but at a more powerful rate...

I don't understand the fibre bundle structure of the Mobius band, described by my textbook. "The base space ##X## is a circle obtained from a line segment L as indicated in Fig. by identifying its ends. The fibre ##Y## is a line segment. The bundle ##B## is obtained from the product ##L \times...

"Band structure a result of Pauli"? Professor hopelessly vague or in essence correct? Hello, I'm taking an introductory course on Solid State physics (level: last year undergrad physics) and the professor said one can view the band structure in solids as a result of the Pauli principle...

Hello Forum, I am looking at the energy levels between the n and p regions of a diode. The p-side has a conduction band that starts at a higher energy (same for the valence band). The n-side has the valence and condution bands that are at lower energy. The Fermi energy line is the same...

Hi, I would like to get suggestions about the physical meaning of the (1) flat-band voltage and the (2) Fermi-level. Before being marked as newbie, I'd like to point out that I know how to calculate them and know that the (1) flat band voltage is the one which you apply, the energy band...

Why the voltage drop across the insulator is linear in the band diagram of a MOSFET??

hello, i have a question related to metallic bonding. As far as i know, valence band is defined as the highest filled level in the band and conductionband as the 1st unfilled level. So, if I have 100 Li, we will have 100 orbitals which form a band. Since we have 100electrones, 50 pairs, so we...

Homework Statement My problem is I want to know how to transform a low pass filter into a band pass and high pass filter. Suppose that we are given the impulse response of the system which is h(n) The Attempt at a Solution In order to transform this system into a band pass filter, I need to...

Hello, do you know why no electron can stay in the band gap? Is it impossible at every energy? Thank you!

Dear forum people, I just learned how to get a tight-binding dispersion for graphene: E = +- \sqrt{1+4\cos((\sqrt{3}a/2) k_x)\cos((a/2) k_y)+4\cos^2((a/2) k_y)} But i can not figure out how can I plot that. I want to plot that in the following path: K \rightarrow \Gamma \rightarrow M...

Hi and thanks for reading, I don't really understand the valleys in the conduction band, in the E vs. k diagram, there is the L-valley, r-valley and X-valley. Each has a different momentum... and are at different energy levels. I understand that at any temperature above absolute zero, a...

I've been having a very difficult time understanding why band structure is expressed in terms of momentum/crystalline directions. I've included a picture of the band structure of silicon so that you can better understand my question. I think I understand basic crystalline structures and the...

I'm thinking mainly within the context of the useful semiconductors here (Si, GaAs, etc.)... What does it mean for an electron to be in the L or X valley instead of the Gamma valley? If Gamma is the k = 0 point, then momentum p = 0. Does that mean being in L or X means all the electrons...

Hi, thanks for reading my questions. I've been reading and reading and reading and reading and I'm trying to understand the difference between conductors, semiconductors, and insulators at an atomic level. When reading about electricity I often find that metals have a "sea" of "free"...

Homework Statement For a stretched rubber band, it is observed experimentally that the tension f is proportional tot he temperature T if the length L is held constant. Prove that: (a) the internal Energy U is a function of temperature; (b) adiabatic stretching of the band results in an...

Hi I've been searching on the web for this two topics, band structure and fermi surface, both of copper. I can't find any of them from a free source, I am doing just a report of my class of introduction to solid state and I just have found this two things in articles that must be bought. If...