What is Band: Definition and 531 Discussions

Hello all, I'm just getting to grips with conduction in solids and am trying to find some values for the band gap between the valence and the conduction bands. All I can find anywhere are typical values for semiconductors (or about an eV). I also found that carbon in the diamond configuration...

I've thought briefly about the problem of estimating a narrow band with signal when limited data is available. Various filtering and smoothing schemes can be imagined. Each of these scheme's will mean you will lose data at at least one of the end points. FIR algorithms, result in a filter with...

Setup: I'm trying to make the band structure for a planar photonic crystal with finite thickness, i.e., a quasi-3D problem. I only want the x-direction band structure. So, I'm using variable floquet periodic BCs for the x-direction boundaries, and 0 degree floquet periodic BCs for the...

Hi, I have just started using a MATLAB program written by someone to do k.p modelling of the quantum well structures.The out put of it is several files.One file has a list of eigen values.Real and imaginary parts.How do I know which energies are CB,LH,HH?since it's a type 2 quantum well,with...

Hi, I would like to know how we can use indirect band semiconductors in lasers. Such type of semiconductors do not emit photons when transition takes place. Energy is given up as heat to the lattice. Regards,

Hi, Really having a hard time finding conduction band offsets for semiconducting quantum wells - specifically GaAs/AlGaAs and CdTe/CdMgTe. I've heard 0.1 and 0.3 eV for AlGaAs and haven't seen anything on CdTe. Does anybody know of a reference where I could find these tabulated. Thanks a...

This seems like almost too much of an elementary question, but what properties of metals / insulators cause their bandgaps to differ?

How does a direct band gap (like that in GaAs) vary with its well width?

is this correct? An energy band is a continuous distribution of similar energy levels? What is the reason for energy bands in solids? The reason is there is a close proximity of many atoms which is because the energy difference becomes very small. So the energy is bundled together rather...

Show how the band model can explain the relationship between the optical and electronic properties of solids? any ideas one were to start looking? lost with this question

band gap arises due to lattice potential.band gap is produced at zone boundary due to bragg reflection.there it behaves like standing wave instead of traveling wave?further formation of 2 standing waves?please help

Delta energy required to excite hole from lowest energy orbit to valence band? I have calculated the orbit of a hole in its lowest energy orbit, but am struggling to work out \delta\epsilon (energy needed to excite it to valence band). Any help much appreciated.

Hi In the band diagram of an ideal Metal Semiconductor contact with \Phi_{M} < \Phi_{S} (work function of metal < work function of semiconductor) and a p-type semiconductor, why does the Fermi Level intersect the Intrinsic level right at the metallurgical junction? Thanks.

Homework Statement Draw a free body diagram showing all the forces on the elastic band, and a free body diagram showing all the forces on the bag of coins Homework Equations F=-kx F=mg The Attempt at a Solution I drew the forces on the elastic band as T = mg (m = mass of coins...

It has to be Nickelback. I know there are other talentless bands out there but Nickelback is completely lacking any form of talent. Plus they're Canadian.

Hi guys i have a question about how semiconductor materials absorb photons at less than the band gap energy. Particularly in an indirect material like silicon. Looking at absorption spectra for silicon i expected for it to immediately drop off at lower than the band gap energy ~1100 nm (1.12...

I do. I am known as "FugTheDrummer". This band is an unedited, unrehearsed, unscripted endeavor brought to you by "2.25". Its also known as a Jam Band. And worse names as well. Please feel free to post your myspace page in this thread... or, if there is provision for mp3s post those...

In the text, there is a rubber band model for 1D chain of N links. Assume each link of the rubber band is align horizontally either to the right or to the left. In the text, define N_+ as the number of links directed to the right and N_- represents the number of links directed to the left. I...

Hi folks, I am new to PF. First I have to apologize for the following english -- it is not my native language. I have problems in understanding the formation of the conduction and valence bands of solids: For example in III-V compound semiconductors both constituents are sp3 hybridized...

Homework Statement draw a circuit for a and pass filter using only capacitor and resistors that will transmit signals in the range 200-1500 hertz. if there are only 100 nf capacitors choose resistor values. Homework Equations The Attempt at a Solution i know the circut would...

The Steepwater Band -- Playing The Cubby Bear in Chicago 12/26 Hey folks, long time no see! I'm taking next semester off so we'll be seeing a lot more of each other now. So, who among you is in or around Chicago and wants to see a kick *** rock and roll show tomorrow night? As the subject line...

Hi Community! I have to study the valence bad of Iron. Could anyone suggest me some articles where spin-resolved photoemission and inverse photoemission experiments are presented? Obviously textbooks are welcome too :smile: Thanks!

This first one is ok and I understand it: 1) Say that n =2 and l = 0. How many 'levels' does it have for N atoms? Ans: So I can easily draw a line for 1s and 2s and say that there will be 2N levels. But I am having problems with some more complex situations. But: 2) Say n = 2. How many...

Homework Statement Hi, I have a practical to do soon, it's only a basic thing because we've only been doing physics for just over a month - plotting a stress-strain graph for an elastic band... 2. The attempt at a solution Now, I was just going to measure the original length of...

Homework Statement In mos capacitor, energy band will bend because of different work function between M&S. But Why apply a "flat band voltage" to flat the bent band? what's the purpose? Homework Equations The Attempt at a Solution I have been looking for the answer from...

Homework Statement A band Pass filter is given with the following configuration, R-Resistor, C-Capacitor: See Attatchment 1 - Circuit.jpg https://www.physicsforums.com/attachment.php?attachmentid=16241&stc=1&d=1225999965 R1 = R2 = 10 kΩ C1 and C2 are unknown Cut off Frequencies...

Homework Statement http://img225.imageshack.us/img225/3118/photo1587hx4.jpg This #74 is on the SAT Practice Subject Test in Physics, which is also the Physics test administered in January 2003. Homework Equations I don't even know how to begin this problem. The Attempt at a...

My professor has said several times that if you increase the potential (electrostatic) you will get a lower energy in terms of a band diagram. In particular, I have been working with MOS-Capacitors and this seems to be the case. For example for an n-type semiconductor. If you apply a...

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...

Suppose we have a rubber band of some elasticity k and of unstreched radius r0 (the band is always kept in the shape of a circle). What work is necessary to strech it to some larger radius r? How do we apply Hooke's law in this situation? Thanks

Can a semiconductor absorb a higher energy photon than its Band gap Eg and make a transition from valence band to conduction band? For a example commonly used IR detector is InAs (semiconductor) whose Eg is 0.354 eV, if a blue light falls on it, will it able to absorve that energy and make a...

we know that at temperature above 0K, in semiconductor some electron collecting sufficient energy fron surroundings to cross the band gap, placed in the conduction band. But what's the actual procedure to make the transition. I mean to say is it direct absorption of IR photons or by some other...

In the first diagram on http://hyperphysics.phy-astr.gsu.edu/hbase/solids/fermi.html" , the band gap in a semiconductor is shown. What is the corresponding Fermi momentum? If you plug E_F into the dispersion relation, you get no solution for k_F, right? I ask because an equation is given...

I was taught this in school but my teacher could not explain why the band splits again with decreasing atomic distance. Also, then i wondered how do you explain the fact the it splits again nicely into 4N states for the valence band and 4N states for the conduction band? Could some one help...

Hi, In all the tutorials of DFT softwares I have encountered computing of the band structure for different systems by using e.g. L-Gamma-X-(U)Gamma circuits. In the texts I have read I have found about X & Gamma but what are L & (U)-Gamma? I also enountered that they have separated the...

Hallo ... I would like to know about the effect of the effective mass on the band structre of the materails..

I have a project that I'm working on involving a rubber band powered vehicle. I have a pretty well developed design involving several methods of propulsion but my main concern is a trigger mechanism in which to release this source of power from the rubber bands. Im not sure whether to go...

My physics/electronics teacher told me some thing really interesting and confusing a wile ago and I have been trying to get my head round it. The forward voltage in a LED (voltage needed to drive the current) is proportional to the band gap energy. However Blue LEDs have a higher forward...

hello to everyone. It is normally said that in semiconductors the Fermi level is half way between the valence and the conduction band. I have the following question on that: what does it mean that the Fermi level is in the band gap? It should mean that the maximum energy of an electron in the...

i know this is a simple question, but i have been looking for a while (maybe 15 min) and i cannot find what is so special about Cu, Ag, and Au? i know there is something special about these 3 metals. something that none of the other metals have. i remember it having to do with fermi velocity /...

Homework Statement There has been created a heterojunction of two different semiconductors, Si and GaP. I am to determine the valence- and conduction band offset with Tershoff's model. Homework Equations The problem is that I can't find the relevant model. Therefore, I cannot find the...

Hi This semester my group and I are calculating the band structure of silicone (bulk and nano crystals). In bulk silicon a indirect band gap occurs, where the highest occupied valence band and the lowest unoccupied conduction band are situated at different k-values. Does anyone know why...

How Can Energy Band Over Lap?! MY question is when i read energy band over lap i thought it is coming because of the huge number of atoms and the small distance between them but is it possible that energy bands of differnt energy bands get over lap and they are have different quantuam numbers...

Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most of the light incident upon it. This works through a process known as multiphoton absorption. In this process, several photons are absorbed at the same time. If very...

Homework Statement A rock group is playing in a club. Sound emerging outdoors from an open door spreads uniformly in all directions. If the decibel level is 70 dB at a dis- tance of1.0 m from the door,at what distance is the music just barely audible to a person with a normal threshold...

Homework Statement [Edit: Please also see additional posts below. I have tried to clarify my question somewhat but didn't want to edit this one just incase anyone can help with the full problem. Thanks! :) ] I did a lab on the band gap in germanium where I measured the voltage across a...

Homework Statement I feel like I have a pretty good conceptual understanding of the origin of band theory, but these two problems were totally above my head. Kittel Ch7 #2 Consider the free electron bands of an fcc crystal lattice in the approximation of an empty lattice, but in the...

Rubber Band Car For Physics-- Any Help? I'm building a rubber band car for physics and need as much help as possible. I'm by myself this time because I chose (and regret it). But, so far I have found this much out: Stuff so far: *Records/CD's are good because of large Diameter *Heating...

Hi again, first of all i want to thanks the replies to my previous posts. Second... I'm looking for a paper about the GaP band structure. Actually i only need the band structure tu compare it with mine but i need the reference to that paper, can you help me?? sorry for my bad english by the way...

Hi, can anybody rigurously explain the relationship between the band diagram in k-space (I think I understand this one) and the diagram in real space (as is often used to explain the p-n-junction).