Fault detection and analysis of bistable rotaxane molecular electronic switch - A simulation approach

Abstract

As the transistor size approaches nano dimension, short channel effects become dominant in micro devices, leading to an incessant struggle to keep pace with Moore's law. This paved way to development of newer technologies like molecular electronics. The self-assembled bottom-up approach makes molecular switches more prone to defects than micro devices. The widely studied molecular switches are mechanically coupled and this paper deals with bistable rotaxane. Feasibility of using bistable rotaxane as a molecular electronic device is analysed in terms of total molecular energy, energy band gap, ionisation energy and distance between ring and dumbbell. Total molecular energy is the vital criteria that decides the feasibility of using a self-assembled rotaxane as a switch. Rotaxane has a band gap of 1.44 eV at Ground State CoConformer (GSCC) and hence acting as a semiconductor. Ionisation energy and position of ring are also important in deciding the switching activity. Due to process variations during self-assembly, ring can localise anywhere over the dumbbell and it may leads to a faulty switch. This work describes a method to verify the switching action of bistable rotaxane through simulation. Testing method described here is carried out before the actual manufacturing of nano crossbar and hence cost effective.

A Novel Defect Tolerance Scheme for Nanocrossbar Architectures with Enhanced Efficiency

“…Molecular switching elements may lose their switching capability during the manufacturing process and such switches are considered as a defective switch. Defects in a molecular switching element can be of three categories: (1) stuck-at-off, (2) stuck-at-on [8], and (3) neither stuck-at-off nor stuck-at-on [9]. Stuck-at-off : These type of defects makes the corresponding crosspoint switch not capable of conducting electrical current or, in the case of a molecular switch, the molecule can possess only its ground state co-conformer (GSCC) geometry. Stuck-at-on fault : These defects make the corresponding switch constantly conduct electric current or, in case of a molecular switch, their geometry is permanently stuck in the metastable state co-conformer (MSCC) state. Neither stuck-at-off nor stuck-at-on fault : This type of fault is typically found in molecular switching elements.…”

“… Stuck-at-off : These type of defects makes the corresponding crosspoint switch not capable of conducting electrical current or, in the case of a molecular switch, the molecule can possess only its ground state co-conformer (GSCC) geometry. Stuck-at-on fault : These defects make the corresponding switch constantly conduct electric current or, in case of a molecular switch, their geometry is permanently stuck in the metastable state co-conformer (MSCC) state. Neither stuck-at-off nor stuck-at-on fault : This type of fault is typically found in molecular switching elements. Here, the molecule loses its intended switching action, but it is neither stuck-at-off nor stuck-at-on position.Our previous studies presented a detailed analysis on these type of faults [9] and in this paper we are concentrating only on the fault tolerance method for stuck-at faults.…”

“…Our previous studies presented a detailed analysis on these type of faults [9] and in this paper we are concentrating only on the fault tolerance method for stuck-at faults.…”