Silicon Quantum Structures with Massive Energy Offset Due to SiO2- vs. Si3N4-Embedding: Alternative to Electronic Impurity Doping (talk)

Ultrasmall silicon (Si) nanoelectronic devices require an energy shift of electronic states for n- and p-conductivity. Nanocrystal (NC) self-purification and out-diffusion in field effect transistors cause doping to fail. Even if dopants manage to enter SiNCs, their ionization energy increases tremendously over values known from bulk Si; no free charge carriers can be provided [1]. We show that silicon dioxide (SiO2) and silicon nitride (Si3N4) create energy offsets of electronic states in embedded Si quantum dots (QDs) in analogy to doping [2]. Hybrid density functional theory (h-DFT), interface charge transfer (ICT), and experimental verifications arrive at the same size of QDs below which the dielectric dominates their electronic properties. Large positive energy offsets of electronic states and an energy gap increase exist for Si QDs in Si3N4 versa SiO2. Using DFT results, the SiO2/QD interface coverage is estimated with nitrogen (N) to be 0.1 to 0.5 monolayers (ML) for samples annealed in N2 versus argon (Ar). The interface impact is described as nanoscopic field effect and propose the energy offset as robust and controllable alternative to impurity doping of Si nanostructures.
[1] D. König, S. Gutsch, H. Gnaser, et al., Sci. Rep. (Nature), 5, 09702 (2015), DOI: 10.1038/srep09702
[2] D. König, D. Hiller, S. Gutsch, M. Zacharias, Adv. Mater. Interfaces 1, 1400359 (2014)