Investigation of the Si/SiO2 interface in silicon nanowires and its role in donor deactivation and charge transport

Silicon nanowires (SiNWs) have been investigated experimentally and theoretically for several years. Their intriguing and yet not fully understood properties and the potential for applications in nanoelectronics, spintronics, energy harvesting, production and storage, sensors, and neuroelectronics motivate this research effort. Due to the high surface area SiNWs represent also a perfect material science lab to investigate with high accuracy specific issues related to defects and interfaces. The investigation of defects at the interface between silicon and silicon oxide becomes very important when the SiNW diameter is below a certain critical value and the surface-to-volume ratio increases [1, 2]. In the present work we focus on the investigation of the doping of silicon nanowires addressing the role of hydrogen, as well as other passivating species, and Pb defects at the Si/oxide (SiO2, Al2O3, HfO2 deposited by atomic layer deposition) interface [3-5] in the donor deactivation mechanisms and the role of the confinement and dielectric mismatch in determining the donor electronic wave function. To address these intriguing issues we have used different complementary experimental techniques such as electron paramagnetic resonance (EPR), both continuous wave and pulsed, FT-IR, Raman, DLTS, electrochemical capacitance voltage (ECV) and MD-PICTS. Silicon nanowires have been produced by metal-assisted chemical etching (MACE) [6, 7] using either AgNO3 nanoparticles or a thin Au layer as catalyst. Oxidation and etching has been used to reduce the size of the nanowires. The reported results are relevant for the wide range of applications exploiting the peculiar silicon nanowires electronic properties and surface reactivity. References: [1] V. Schmidt, S. Senz, and U. Gösele, Appl. Phys. A. 86, 187 (2007) [2] M. T. Björk, H. Schmid, J. Knoch, H. Riel and W. Riess, Nature Nanotech. 4, 103 (2009) [3] M. Fanciulli, A. Vellei, C. Canevali et al., Nanosci. Nanotechnol. Lett. 3, 568 (2011) [4] M. Fanciulli, A. Molle, S. Baldovino, A. Vellei , Microelectronic Engineering 88, 1482 (2011) [5] M. Fanciulli, M. Belli, S. Paleari, A. Lamperti, M. Sironi, and A. Pizio, ECS J. Solid State Sci. Technol. 5(4), 3138 (2016) [6] Z. Huang, N. Geyer, P. Werner et al., Adv. Mater. 23, 285 (2011) [7] C. Canevali, M. Alia, M. Fanciulli, M. Longo, R. Ruffo, C.M. Mari, Surface & Coatings Technology 280, 37 (2015)