We have deposited mixed Boron Carbide phases using PECVD. While deconvoluting XPS results, we have got a peak at 187.42 eV in B1s spectrum which we are having trouble to identify. Since the peak at 188.44 eV represents B atom in B4C environment as we found in many journals; we are suspecting that 187.42 eV may be some phase BxC where x>4.
There is no BN formation which we have already cross checked by trying to deconvolute N1s peak. It shows bonding only with Oxygen. We also have IR results of the sample. Now, decreasing binding energy indicates increasing oxidation number of Boron indicating presence of more Boron atoms.
We have to find out what the phase of BxC at 187.42 eV is?
My experience with Boron compounds in XPS is limited, but in the samples I have investigated, I have observed binding energies between 187 and 188 eV due to BoroHydrides (e.g. B10H14 or NaBH4).
My other thought is this is not an explicitly bound boron, but instead interstitial site boron (compare with nitrogen and interstitial nitrogen in N-doped TiO2)
Dear Sir,
it may be useful to check whether the additional peak at 187.42 eV is related to the
bulk or to the surface of the sample by looking at the 188.44 eV : 187.42 intensity ratio when varying the take-off angle.
In case that the 187.42eV intensity increases with increasing surface sensitivity
you may think of the formation of, e.g., B6O at the surface (as caused by small amounts of contaminations from oxygen) since the following
reference predicts a binding energy of about 187.41 eV for this species:
.
Belyansky M., Trenary M., Ellison C.
Journal: Surf. Sci. Spectra 3, 147 (1994)
Sincerely, FM
I would agree with Frank and look at the O(1s) and grazing angle spectra. I had overlooked that you were creating these materials via a CVD method, so a trace of oxygen could easily form such boron oxides.
Dear Sir,
unfortunately I do not have access to this journal. However, in case that
the peak at 187.42 eV is indeed due to the formation of B6O at the surface
you should observe a second peak of nearly the same intensity at about
189.2 eV. This is caused by the chemical shift for two different boron sites
within the B6O crystal structure.
The abstract of the above mentioned paper reads as follows:
"The XPS spectrum of the boron suboxide, B6O, is reported. The spectra
were obtained on a powder sample that was prepared and characterized at
the Diamond Technology Center, Norton Company. It was characterized with
x‐ray diffraction and was prepared by established methods. The B 1s peak is
split into two components of approximately equal area corresponding to the
equal numbers of boron atoms at the two inequivalent sites of the B6O
structure. The two B 1s components have binding energies of 187.4 and
189.2 eV."
Sincerely, FM
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