4 ms·

I don't understand how it can be described as '2D'. If it were 2D you would be able to stack an infinite amount without the stack getting higher.

by danford 12y ago

tedsanders 12y ago
"2D" describes the freedom of the electrons. They can move in X and Y, but not Z. This restricted freedom causes all sorts of unique electronic behavior never seen in 3D systems. You are certainly correct that graphene has height. Source: I am getting a PhD in 2D electron physics
zacharypinter 12y ago
My guess is that the people describing it as 2D are focusing on different properties of 2-dimensional space than you are and would agree with you that stacking it would increase the height.
dm2 12y ago
I think there is a different definition of 2D in the materials science field. http://www.mri.psu.edu/centers/2dlm/ http://www.mri.psu.edu/centers/2dlm/ http://www.chemistryviews.org/details/ezine/4976821/Is_Graphene_Really_a_2D_Material.html http://www.chemistryviews.org/details/ezine/4976821/Is_Graph... http://gigaom.com/2013/07/19/graphene-isnt-the-only-2d-material-here-are-a-few-others-that-could-change-material-science/ http://gigaom.com/2013/07/19/graphene-isnt-the-only-2d-mater... http://www.mrs.org/s13-cfp-o/ http://www.mrs.org/s13-cfp-o/
Osmium 12y ago
Loosely, it refers to the degrees of freedom an electron has in the material. For example, if you consider the 'density of states' – a quantity which can be thought of as the number of electrons at a given energy level – it has a different characteristic shape depending on whether the material is '1D', '2D', '3D' or even '0D': http://britneyspears.ac/physics/dos/images/Image441.gif http://britneyspears.ac/physics/dos/images/Image441.gif [As an aside, britneyspears.ac is a surprisingly good resource for a lot of basic solid state physics. You can find a full derivation of the above graph on there.] Edit: To illustrate, this next graph is the density of states for three different Carbon-based materials: graphite which is '3D', graphene which is '2D' and a nanotube which is '1D'. http://me3007.wdfiles.com/local--resized-images/thermal-and-electronic-properties-of-carbon-nanotubes/QuantDOS.jpg/medium.jpg http://me3007.wdfiles.com/local--resized-images/thermal-and-... [Source: Hone, J., Quantized Phonon Spectrum of Single-Wall Carbon Nanotubes, Science, 289, 1730, 2000 via http://me3007.wikidot.com/thermal-and-electronic-properties-of-carbon-nanotubes http://me3007.wikidot.com/thermal-and-electronic-properties-...] You can see how these curves are similar to the theoretically-derived curves in the previous graph.

I don't understand how it can be described as '2D'. If it were 2D you would be able to stack an infinite amount without the stack getting higher.

by danford 12y ago

I don't understand how it can be described as '2D'. If it were 2D you would be able to stack an infinite amount without the stack getting higher.

tedsanders 12y ago

"2D" describes the freedom of the electrons. They can move in X and Y, but not Z. This restricted freedom causes all sorts of unique electronic behavior never seen in 3D systems. You are certainly correct that graphene has height. Source: I am getting a PhD in 2D electron physics

zacharypinter 12y ago

My guess is that the people describing it as 2D are focusing on different properties of 2-dimensional space than you are and would agree with you that stacking it would increase the height.

dm2 12y ago

I think there is a different definition of 2D in the materials science field. http://www.mri.psu.edu/centers/2dlm/ http://www.mri.psu.edu/centers/2dlm/ http://www.chemistryviews.org/details/ezine/4976821/Is_Graphene_Really_a_2D_Material.html http://www.chemistryviews.org/details/ezine/4976821/Is_Graph... http://gigaom.com/2013/07/19/graphene-isnt-the-only-2d-material-here-are-a-few-others-that-could-change-material-science/ http://gigaom.com/2013/07/19/graphene-isnt-the-only-2d-mater... http://www.mrs.org/s13-cfp-o/ http://www.mrs.org/s13-cfp-o/

Osmium 12y ago

Loosely, it refers to the degrees of freedom an electron has in the material. For example, if you consider the 'density of states' – a quantity which can be thought of as the number of electrons at a given energy level – it has a different characteristic shape depending on whether the material is '1D', '2D', '3D' or even '0D': http://britneyspears.ac/physics/dos/images/Image441.gif http://britneyspears.ac/physics/dos/images/Image441.gif [As an aside, britneyspears.ac is a surprisingly good resource for a lot of basic solid state physics. You can find a full derivation of the above graph on there.] Edit: To illustrate, this next graph is the density of states for three different Carbon-based materials: graphite which is '3D', graphene which is '2D' and a nanotube which is '1D'. http://me3007.wdfiles.com/local--resized-images/thermal-and-electronic-properties-of-carbon-nanotubes/QuantDOS.jpg/medium.jpg http://me3007.wdfiles.com/local--resized-images/thermal-and-... [Source: Hone, J., Quantized Phonon Spectrum of Single-Wall Carbon Nanotubes, Science, 289, 1730, 2000 via http://me3007.wikidot.com/thermal-and-electronic-properties-of-carbon-nanotubes http://me3007.wikidot.com/thermal-and-electronic-properties-...] You can see how these curves are similar to the theoretically-derived curves in the previous graph.