Atom Probe Tomography Analysis of Boron and/or Phosphorus Distribution in Doped Silicon Nanocrystals

Abstract

Silicon nanocrystals (Si NCs) are intensively studied for optoelectronic and biological applications due to having highly attractive features such as band engineering. Although doping is often used to control the optical and electrical properties, the related structural properties of solely doped and codoped Si NCs are not well-understood. In this study, we report the boron (B) and/or phosphorus (P) distribution in Si NCs embedded in borosilicate glass (BSG), phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG) using atom probe tomography (APT). We compared solely and codoped Si NCs grown at different temperatures so that we may compare the effects of codoping and temperature on the B and/or P distribution. Proximity histograms and cluster analyses reveal that there exist boron-rich layers surrounding Si NCs and also B–P clusters within the Si NCs. Raman spectra also show a structural change between codoped Si NCs in solids and free-standing codoped Si NCs. These results lead us to understand that codoped Si NCs disperse in polar solvents.

Doped and codoped silicon nanocrystals: The role of surfaces and interfaces

“…In these cases the formation energy assumes negative values. It is interesting to note that Nomoto et al [129] have observed that codoping is an effective means of promoting segregation and stability of the These results are confirmed by the calculation performed in the case of multidoping [235]. In Fig.…”

“…However, the self-purification effects can be strongly influenced by the presence of defects, vacancies or different capping species used to saturate the dangling bonds at the interface; this fact explains the efficient incorporation of dopant atoms in small Si-NCs with diameter less than 2 nm [129,153,154,155,156].…”

“…Regarding the impurity location, APT and proximity histogram [129] revealed incorporation of B and P into the Si-NCs with clear differences. The B concentration sligthly decreased on going from the matrix to the Si-NC interfaces and from the Si-NC interfaces to the NC core.…”

Versatility of doped nanocrystalline silicon oxide for applications in silicon thin-film and heterojunction solar cells

“…Both, P and B, were found to be distributed nearly equally across both phases. This is in contrast to thermally grown films of Si nanocrystalls embedded in a SiO 2 matrix where an increased P content was found in the Si nanocrystalls for n-type material and a decreasing amount of B towards the inner part of the nanocrystalline Si for p-type material [20]. A possible cause might be a lack of time and/or energy provided to the system during PECVD to rearrange the dopant atoms to their thermodynamically favorite sites.…”

“…Before, a 300 nm layer of Pt was deposited on the films to prevent damage from Ga ions during the FIB milling. More details on the sample preparation can be found in [20]. The measurements were performed on a CAMECA LEAP 4000Xsi with a pulsed 355 nm laser (250 kHz, 50 pJ) and an overall detection efficiency of 57 %.…”