# Homework Help: Hall Effect Relocated

1. Nov 1, 2004

### Emc2brain

Hall Effect!!!! Relocated

Hey guys, I'm having a little confusion. Have spent too much time in trying to work through this. . .

In performing the Hall Effect experiment, I took data of the Hall voltage versus Temperature. I performed this three times for different fixed B, magnetic fields. The conversion factor for temperature (degrees celsius) to volts is 40 microvolts/Kelvin (not even sure if we use this here?). In the attachment there is a graph of vH vs. T for some B. I feel like I am a blind mouse, I'm confused as to what I am to derive from this relationship. Perhaps the resistivity relationship, but again, not sure. If anyone has any insight I would be most thankful.

I have completed another portion of the experiment vH versus B (for fixed T). Here I obtained a linear relationship. From this I could easily calculate the Hall Coefficient, RH. So I have that completed; its the former that is giving me trouble.

Thanx
Hannah

File size:
19 KB
Views:
74
2. Nov 1, 2004

### Pieter Kuiper

It is conventional to have the independent variable (temperature in this case) on the horizontal axis.

Looks like a semiconductor, the number of carriers increases with temperature, as does the conductivity.

3. Nov 1, 2004

### Emc2brain

Thanx for your reply. What you mentioned is actually how I initially began my analysis, the only problem here with Temperature on the x-axis and hall voltage on the y-axis is that there is a gradual increase, a maximum reached, then a decrease (even as the temperature is steadily increasing). But now, in considering this, perhaps this peak has to do with the intrinsic and extrinsic behaviors of the temperature, in relation to the # of carriers. If this is true, I still don't know where to begin here there. . .

LOST
Hannah

4. Nov 1, 2004

### Integral

Staff Emeritus

5. Nov 1, 2004

### Dr Transport

First of all, what is the material you are measuring????? I assume that you are measuring a semiconductor, from there we can help you determine whether or not it is p-type or n-type. I suspect that your data is showing classic scattering mechanisms, impurity at low temperatures and optical phonon at higher temperatures. There is a "simple" explanation for the trends you are seeing.

dt

6. Nov 1, 2004

### Pieter Kuiper

At high temperatures the Hall effect in semiconductors goes down also because the positive and negative carriers have opposite signs of the Hall effect. The sign may reverse when the sample reaches the intrinsic region.

But I do not know how to explain the increase in the beginning.

7. Nov 1, 2004

### Dr Transport

Doping aside, scattering at low temperatures takes 2 forms, neutral impurity and acoustic-phonon scattrering. Acoustic phonon scattering decreases with increasing temperature, impurity scattering increases with temperature, hence the increas in voltage as T increases. Look in any solid state text that has a significant amount of material about semiconductors. I can think of one off of the top of my head, Tranport in Compiund Semiconductors by B.R. Nag or The Physics of Semiconductors by Yu and Cardona. Both treat electronic transport very well and will give you clues to solving this problem. At some point, the phonon scattering and ionized inpiurity scattering takes over and voltage decreases again.

dt

8. Nov 2, 2004

### Emc2brain

Thank you Transport, I will see if the university has that book or any other semi-conductor text. I did fail to mention that the "Hall element" here is a p-type semiconductor, Germanium. But, so it is NOT abnormal to see an increase (in dt) then a decrease (in dt)? Okay, even with the text I have or what I have researched I still cannot determine what I am supposed to derive from the Temp vs. VHall relationship (maybe this is so because this is very elemental that it is not worth mentioning?). But I do understand your concepts (intrinsic-extrinsic), just don't know where I am supposed to go from here. If there's anything you can add, that would be great. If not, thank you for your help!

Hannah

9. Nov 2, 2004

### Pieter Kuiper

Maybe I should not help you this much, but there is a link to a relevant .pdf-file on
http://w3.msi.vxu.se/~pku/FyC703/Hall.html [Broken]

Last edited by a moderator: May 1, 2017
10. Nov 2, 2004

### Emc2brain

Hahahahah! Yeah, you shouldn't have given that, that's the one our professor gave my partner and I! The exact one. Look's like I'm just gonna have to bug him then . . . Thanx so much for helping me. I'm obviously lacking some sort of knowledge here.

Hannah