Decoding of stochastically assembled nanoarrays

Abstract

A key challenge that will face nanotechnologies will be controlling the uncertainty introduced by stochastic selfassembly. In this paper we explore architectural and manufacturing strategies to cope with this uncertainty when assembling nanoarrays, crossbars composed of two orthogonal sets of coded parallel nanowires. Because the encodings of nanowires that are assembled into a nanoarray cannot be predicted in advance, a discovery process is needed and specialized decoding circuitry must be employed. We have developed a probabilistic method of analysis so that various design strategies can be evaluated. * This research was funded in part by NSF Grant CCR-0210225. † Contact person. Appears in Procs. ISVLSI 2004. 2 Overview of the Crossbar and Modulation-Doped Nanowires This section describes modulation-doped nanowires and their role in stochastically assembled nanoarrays. 2.1 Modulation-Doped Nanowires

Radial addressing of nanowires

“…] and length λ A binary reflected codes (λ A -BRCs) [Gojman et al 2004;. To describe them we assume that controllable NW regions are aligned with MWs ].…”

“…Using (h, λ A )-hot codes, DeHon et al show that with high probability N modulation-doped NWs can be controlled with 2.2 log 2 N + 11 MWs when the design goal is that all NWs doping patterns be different. Using binary reflected codes and the assumption that at least half of the NWs have different doping patterns, Gojman et al [Gojman et al 2004] show that this number can be reduced to 2 log 2 N + 8 MWs, although a somewhat better upper bound might be obtained for (h, λ A )-hot codes. They also analyze the area needed for the translation memory.…”

“…If a BRC is shifted axially by the pitch of MWs, the doping pattern under MWs corresponds to that of another BRC [Gojman et al 2004]. In other words, the set of BRCs is closed under displacements by multiples of a MW pitch.…”

“…The state of a switch at a crosspoint (defined by a pair of orthogonal NWs) can be sensed without changing its state by application of a smaller electric field. Nanocrossbars have the potential to serve as very high density memories and programmed logic arrays (PLAs) [DeHon 2003;DeHon et al 2003;Gojman et al 2004;DeHon et al 2005]. A prototype 8 × 8 crossbar with a density of 6.4 Gbits/cm 2 has been announced that is based on these technologies [Chen et al 2003] and a memory with storage capacity of 10 Gbits based on crossbars of NTs is promised (see http://www.nantero.com).…”

Evaluation of design strategies for stochastically assembled nanoarray memories

“…It is proposed that nanocrossbars be used as very high density memories and programmed logic arrays (PLAs) [DeHon 2003;DeHon et al 2003;Gojman et al 2004;Rachlin et al 2005;DeHon et al 2005]. A prototype 8 × 8 crossbar with a density of 6.4 Gbits/cm 2 has been announced that is based on these technologies ] and a memory with storage capacity of 10 Gbits based on cross-bars of NTs is promised (see http://www.nantero.com).…”