Do the XRD peaks of a crystalline shift to the high or low 2θ direction by doping? In other words, does the doping lead to XRD peaks shifting or change in the peaks intensity?
Abbas - Theoretically, doping other atoms into a structure will lead to both peak shifts and changes in intensity. The peak shifts occur because of the difference in SIZE of the atoms, and cause the repeat distances in the crystal structure to expand or contract depending on whether the doped atom is larger or smaller than the host atom. The change in intensity occurs because the electron density of the doped atom is different than that of the surrounding atoms, and can make some peaks more intense and other peaks less intense. However, as other answerers have pointed out, the degree of these changes depends on the concentration of the doping atom - if that concentration is sufficiently small, like at the ppm level or below, you may not notice any change in the diffraction pattern.
It very much depends on the system that you're studying. You may want to look into what's called, Vegard's Law (http://en.wikipedia.org/wiki/Vegard%27s_law). In many materials, we find that if we dope with atoms of different sizes, the lattice parameters will shift. If it is a larger ion, we expect the lattice to grow and thus the peaks in your diffraction pattern (in 2 theta) will shift to smaller angles.
However, beyond that, in XRD, the strength of the scattering from a given element will depend on its atomic number. So, if the atom you are doping is rather different than that of the original composition, you will also see a relative change in peak intensity.
You can fit these differences with Rietveld programs such as fullprof, GSAS, or TOPAS.
Good luck!
http://en.wikipedia.org/wiki/Vegard%27s_law
Dear William ,
thanks.in the n-type and p-type semiconductors in the Si ,please compare the impurity atoms size with the host atoms and tell me doping lead to the peaks shifting or change in the peaks intensity.
Regards,
It depends on the doping concentration. In the case of Si, the doping concentration stays around 10^10 - 10^11 /cm3. This concentration is very small compared to the atomic concentration of Si 10^23 /cm3. I am not sure that this doping concentration modifies the diffraction patterns of Si in XRD.
Abbas - Theoretically, doping other atoms into a structure will lead to both peak shifts and changes in intensity. The peak shifts occur because of the difference in SIZE of the atoms, and cause the repeat distances in the crystal structure to expand or contract depending on whether the doped atom is larger or smaller than the host atom. The change in intensity occurs because the electron density of the doped atom is different than that of the surrounding atoms, and can make some peaks more intense and other peaks less intense. However, as other answerers have pointed out, the degree of these changes depends on the concentration of the doping atom - if that concentration is sufficiently small, like at the ppm level or below, you may not notice any change in the diffraction pattern.
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