Theoretical and Experimental Evidence for the Inability of Impurity Doping to Provide Majority Carriers to Si Nanocrystals (poster)

We report on phosphorous (P) doping of Si nanocrystal (SiNC)/SiO2 systems [1]. Relevant P configurations within SiNCs, at SiNC surfaces, within the sub-oxide interface shell and in the SiO2 matrix were evaluated by hybrid density functional theory (h-DFT). Atom probe tomography (APT) and its statistical evaluation provide detailed spatial P distributions. We obtain ionisation states of P atoms in SiNC/SiO2 systems at room temperature using X-ray absorption near edge structure (XANES) spectroscopy in fluorescence yield mode. This non-destructive volume characterization technique leaves the material unchanged which is paramount to probe P in its original state. P K shell energies were confirmed by h-DFT. We found that P diffuses into SiNCs and resides virtually exclusive on interstitial sites. XANES and h-DFT delivered evidence that the ionization probability of P in the SiO2/SiNC system is extremely low; free localized electrons to SiNCs are not provided.
[1] D. König, S. Gutsch, H. Gnaser, et al., Sci. Rep. (Nature), Vol. 5, 09702 (2015), DOI: 10.1038/srep09702