Active Impurity Doping of Silicon Nanovolumes: Failure and Alternatives
We report on phosphorous (P) doping of Silicon nanocrystal (SiNC) /SiO2 systems . Rele-vant 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. P K shell energies were confirmed by h-DFT. While P diffuses into SiNCs and predominantly resides on interstitial sites, its ioniza-tion probability is extremely low; free localized electrons to SiNCs are not provided.
As alternative, SiO2 and Si3N4 create substantial energy offsets of electronic states in SiNCs . h-DFT, interface charge transfer and experimental verifications arrive at the same NC size below which the embedding dielectric dominates their electronic properties. An increased energy gap was found for Si NCs in Si3N4 vs. SiO2 by h-DFT and confirmed in experiment. We describe the interface impact as nanoscopic field effect and show that the energy offset is very robust and controllable. As application example, we propose an undoped CMOS-able and CMOS technology-compatible Si-Nanowire MISFET.
Dr. Dirk König completed his PhD with 1st class Honours at the Institute of Physics TUCh, Germany. In 2004-05 he was a Post-doc at materials group ”Super-computer based modelling of novel gate dielectrics”, 65 nm technology node, AMD Europe, Dresden, and TUCh, both Germany. From 2005-14 he was Research Fellow / Senior Research Fellow (SRF), Head of Theory and Characterisation group, ARC Photovoltaics centre of Excellence / Australian Centre of Advanced Photovoltaics (ACAP), UNSW, He is currently Deputy Director (Research), Integrated Material Design Centre (IMDC), and SRF, ACAP, UNSW, Sydney.
Dirks research interests are in the fields of
- Novel/alternative materials for quantum structures and hot carrier absorbers
- Quantum & solid state physics, HF-DFT (Gaussian), EMA (FORTRAN, MatLab), reactivity and thermochemistry of solids
- Thin film characterisation (I,C,G/V, DLTS, PES, IPES, RBS, SIMS, TEM, EELS, PL, FT-IR)
- Concepts of practical realisation of third generation PV devices
- Preparation of quantum structures (wet chemistry, sputtering, anneal/RTP, passivation, metallisation)