Van der pauw resistance question

[iamlovelyboy]

All,
Why is it that Van der pauw resistance eliminates contact resistance issues when measuring sheet resistance using this method when compared to the 2 terminal msmt?
can someone please enlighten me?
Thank you

Lovelyboy
UC Irvine grad student.

 

[NoTime]

Here is some info -> http://en.wikipedia.org/wiki/Van_der_Pauw_method

 

[iamlovelyboy]

Hi...
i did go through this...but it doesn't answer my question... if you know the answer can you please help me?

 

[NoTime]

I'm not real strong on this, so it may not be entirely correct.

The 2D sheet can be thought of as an array of resistors.
Using 2 contacts you just get the resistance of the entire array.
With the four contacts you can compute the resistance of an effective 1D sheet, without the artifacts that an actual 1D sheet might introduce.
Not particularly important unless you want to work with the Hall effect where the carrier density across the sheet is not going to be a constant.