- Process Variability and Electrostatic Analysis of Molecular QCA M. Graziano, London Centre for Nanotechnology A. Pulimeno, R. Wang, X. Wei, M. Ruo Roch, G.Piccinini, Politecnico di Torino Molecular Quantum-dot Cellular Automata (mQCA) is an emerging paradigm for nanoscale computation. Its revolutionary features are the expected operating frequencies (THz), the high device densities, the non- cryogenic working temperature, and, above all, the limited power densities. The main drawback of this technology is a consequence of one of its very main advantages, i.e. the extremely small size of a single molecule. Device prototyping and the fabrication of a simple circuit are limited by the lack of control in the technological process [Pulimeno et al. 2013a]. Moreover, high defectivity might strongly impact the correct behavior of mQCA devices. Another challenging point is the lack of a solid method for analyzing and simulating mQCA behavior and performance, either in ideal or defective conditions. Our contribution in this paper is threefold. i) We identify a methodology based on both ab-initio simu- lations and post-processing of data for analyzing a mQCA system adopting an electronic point of view (we baptized this method as “MoSQuiTo”). ii) We asses the performance of a mQCA device (in this case a bis- ferrocene molecule) working in non ideal conditions. We use as a reference the information on the fabrication critical issues and on the possible defects that we are obtaining while conducting our own ongoing exper- iments on mQCA. iii) We determine and assess the electrostatic energy stored in a bis-ferrocene molecule both in an oxidized and in a reduced form. Results presented here consist of quantitative information for a mQCA device working in manifold driv- ing conditions and subjected to defects. These information are given in terms of a) output voltage b) Safe- Operating-Area (SOA), c) electrostatic energy, d) relation between SOA and energy, i.e. possible energy reduction subject to reliability and functionality constraints. The whole analysis is a first fundamental step toward the study of a complex mQCA circuit. It gives important suggestions on the possible improvements of the technological processes. Moreover, it starts an interesting assessment on the energy of a mQCA, one of the most promising feature of this technology. 1. INTRODUCTION The most important reason why Quantum-dot Cellular Automata elements [Lent et al. 1993] could successfully substitute CMOS devices relies on the information propaga- tion principle. Information transfer among QCA devices is determined only by local field interaction and does not involve charge transport. As a consequence, the power dissipated is dramatically reduced. Notwithstanding the amazing device density al- lowed by the extremely reduced feature sizes, the power dissipation, and especially the power density, is much less than in CMOS technologies [Pulimeno et al. 2012] and in other emerging technologies based on electron transport [Graziano et al. 2013][Za- hir et al. 2014]. This point represents the most promising reason to explore mQCA potentials. In recent years the QCA principle has been studied, and in some cases experimen- tally demonstrated, considering a few different technologies, materials and approaches [Lent et al. 1993][Imre et al. 2003][Graziano et al. 2011][Vacca et al. 2012] [Awais et al. 2013][Vacca et al. 2014][Awais et al. 2012] (see the next section for a state of the art de- scription). In this work we focus on molecular QCA, which promises nanometer-scale devices, ultra-high device densities, room-temperature operation and, in particular, very low energy dissipation [Blair et al. 2009]. In particular, we study a real molecule, a bis-ferrocene molecule (Figure 1(A)), specifically ad-hoc synthesized for this purpose [Arima et al. 2012] that we adopted for our own experiments. The technological pro- cess, though, both in general and specifically for this molecule, is currently lacking Author’s addresses: VLSI Laboratory, Electronics and Telecommunications Department, Politecnico di Torino, corso Duca degli Abruzzi 24, Torino (TO), Italy. Mariagrazia Graziano is also with London Centre for Nanotechnology, Physics and Astronomy Department, UCL, London. -, Vol. -, No. -, Article -, : -.