Analysis and modulation of Molecular
QCA wire and development of MQCA
devices
PhD poster day of DET, 4 Dec. 2014
Author: Ruiyu Wang ID:33909 I PhD year
Tutor: Gianluca Piccinini
Collaborators: Mariagrazia Graziano
Azzurra Pulimeno
Attended Courses
Name of Courses
Applications of Electrical and Mechanical Network Analogies
Chimica-fisica dei materiali per le nanotecnologie
Etica informatica
Fibre ottiche in vetro per applicazioni fotoniche
Lingua italiana I livello
Microelectronic systems
Sistemi elettronici a basso consumo
Un metodo alternativo per l’insegnamento della fisica
Total
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
2 / 15
Date
18/09/2014
16/07/2014
12/05/2014
28/04/2014
18/09/2014
08/09/2014
18/09/2014
17/10/2014
Credit
5
7
4
4
3
6
6
2
37
Outline of research
1 Research context and motivation
Intro & Background
Motivation
2 Addressed research questions
3 Novel contributions
4 Adopted methodology
MoSQuiTo
External biasing condition
Wire simulation and algorithm of analysis
Calculation of charge distribution on wire
5 Publication
6 Future work
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
3 / 15
Intro & Background of QCA technology
• The QCA theory was introduced as a new concept for
digital computing ( C.S. Lent, 1994).
• QCA cell contains 6 dots with two free charges.
• 3 different states can be encoded depending location of
charges.
• Function blocks are implemented by aligning QCA cells
together (wire, majority voter, etc).
"1"
"0"
"Null"
(A)
INPUT2
OUTPUT
INPUT1
Molecular QCA wire
INPUT
(B)
OUTPUT
INPUT3
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
4 / 15
Motivation
• More Moore trend
I The scaling of transistor is down to molecular size.
I Huge power density is involved.
• More than Moore approaches
I A change of paradigm.
I No charge transportation during logic encoding.
• Molecular QCA (MQCA)
I Considered to be the most promising.
I High frequency, high device density, and room temperature
operation.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
5 / 15
Motivation cont.
• Real molecule (“bis-ferrocene”) was synthesized
I No systemic approach is used to analyse such devices
from an electronic point of view.
I Essential to study and understand their performances as
much as possible near the physical level.
• Molecular QCA wire
I Simplest demonstration of functional block.
I Analysis of wire provides general knowledge in terms of
information propagation.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
6 / 15
Addressed research questions
• Implementation of systematic tool
I Developed to analyse molecule behaviour with respect to
the state of the art.
• Information degradation among molecules
I Electrostatic repulsion provides interaction between nearby
molecules in QCA technology.
I Logic signal is not sensitive enough after propagated
through several molecules.
• Simulation of MQCA wire
I Iterative simulation step for emulating molecular wire.
I Analysis and modulation of information propagation along
wire.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
7 / 15
Novel contribution
• “MoSQuiTo”(Molecular Simulator Quantum-dot cellular
automata Torino).
I
Designed to study molecular QCA systems from an
electronic point of view.
• Implementation of external biasing condition.
I Enhance or prohibit MQCA’s performance.
• Algorithm for analysing information propagation.
I Demonstration of linearity and superposition of interactions
between nearby molecules on wire.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
8 / 15
Adopted methodology
1. Our own suite “MoSQuiTo” is organized in two stages:
I
I
Ab-initio simulation: utilized in order to compute and
evaluate the electronic structure and properties of
molecules.
Post-processing of data: utilized to elaborate useful figures
of merits (aggregated charge, equivalent input voltage VIN ,
etc).
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
9 / 15
Adopted methodology cont.
2. Implementation of external biasing condition
I
I
I
I
Called “clock” and used to enhance or hinder molecular
QCA’s performance.
Implemented by placing two layers of point charges parallel
with molecules.
The polarity of point charges of clock is opposite.
With “clock”, the switching of logic signal, or the
propagation of information is better.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
10 / 15
Adopted methodology cont.
3. Simulation of wire.
I
A molecular QCA wire based on bis-ferrocene molecules
was made by means of iterative simulation steps.
4. Algorithm for analysing wire
I
I
Designed for determining information propagation along
molecular QCA wire.
Discovery of the linearity between the driver’s influence
(VIN ) and charge distribution on molecule.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
11 / 15
Adopted methodology cont.
4. Algorithm Cont.
I
I
Based on linearity discovered, the superposition method is
exploited.
Superposition in terms of interactions between nearby
molecules.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
12 / 15
Calculation of charge distribution on wire
• According to algorithm just defined, the calculation of
charge distributed on molecules along the wire is possible.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
13 / 15
Publication
• Submitted to ACM Journal on Emerging Technologies in
Computing Systems:
I
“Process Variability and Energy Analysis of Molecular
QCA”, M. Graziano, A. Pulimeno, R. Wang, X. Wei, M. Ruo
Roch, G. Piccinini.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
14 / 15
Future work
1. Profound analysis of longer wire
I
I
I
More molecules (> 2) is about to considered.
Multiple inter-molecule distance (0.9nm, 0.8nm, etc).
Gives important feedback for analysing and demonstrating
propagation of information through wire.
2. Exploration of a minimum distance on wire
I
I
Based on existed algorithm regarding the superposition of
interaction.
To decouple interaction between molecules on wire.
3. Analysis of more complicated MQCA devices.
I
Majority voter, etc.
Ruiyu Wang
Molecular QCA wire
4 Dec. 2014
15 / 15