RICERCA ITALIANA     

Design of novel nanostructured materials for electronic and optical applications via first-principles theory and simulations

Università degli Studi di Modena e Reggio Emilia

Abstract

Nanotechnology and nanoscience are concerned with material science and its application at the nanometer scale. Rather than a new specific area of science, nanoscience is a new way of thinking. Its revolutionary potential lies in its intrinsic multidisciplinarity and its development and successes depend strongly on common efforts and fruitful interaction. Nanocrystalline materials exhibit a variety of novel physical properties as consequence of the interplay between quantum confinement and electronic correlation. These properties offer the possibility of design new and extremely interesting materials for a variety of technological applications. In particular regarding the development of innovative optical and transport devices and of solar cells of new generation. In order to engineer nanomaterials with specified properties and to fabricate nano-scale optolelectronic devices with the desired behaviour, it is necessary to understand the structural,electronic and optical properties on a fully quantum mechanical level. The theory plays a crucial role because a precise knowledge of the electronic excitations represents a fundamental step towards the innovations, design and fabrication of materials and devices based on nanoscale-technology having properties tuned to the requirements of real technological applications. This project is aimed to integrate and develop the research capabilities of four teams having complementary expertises in the ab-initio study of processes related to >>>

Principal Investigator

Stefano Ossicini Università degli Studi di MODENA e REGGIO EMILIA

Research Objectives

The scientific aim of this program is the substantial improvement and development of a theoretical approach "with atomic understanding" for the determination of the structural,electronic and optical properties of nanostructured and low-dimensional systems.
To reach this goal we will integrate and develop the research capabilities of 4 research teams in the field of the fundamental science of nanoscale systems and advanced materials. These teams have actively and succesfully collaborated in the past in several national projects. Moreover both Roma and Milano nodes already belong to an European Network of Excellence (NoE) entitled NANOQUANTA, whereas Modena and Napoli nodes are both active in the European Network Psi-k "Electronic Structure Calculation of Solids and Surfaces". Through the active collaboration and the powerful combination of quantum-mechanical theory and computer simulation we will make contact with nanoscience experimental studies and directly with technologically relevant structural, electronic and optical processes. Several state-of-the-art computer codes are available for the proposed research program: besides publicly available codes, we will use a number of computer codes developed, all or in part, whithin our groups. We will strongly focus on the development of both theoretical and algorithmic methods. In particular we will use many-body perturbation theory (MBPT) and time-dependent density-functional theory (TDDFT), both >>>

First Results

A primary purpose of this project is the development of new theoretical and computational tools for an improved description of electron correlation, spin and optical properties. These tools are aimed to understand the interplay between the experimentally observed changes in optical properties and the related structural modifications of the material under study. Another key point of this project will be the application of these tools to several nanostructured and low-dimensional semiconductor systems, involved in many of the present cutting-edge developments: in nanotechnology, in semiconductor device fabrication, in quantum computing, bio-functionalization, and photovoltaic applications. The aim is to design specific systems for their potential applications in opto- and nano-micro-electronics. We expect a strong impact of our results in fundamental research and in applied research on systems that are important for optoelectronics devices being fully compatible with conventional electronics, for the conversion of sunlight to electric power and in the general field of nanotechnology.
Regarding the development of new theoretical and computational tools the main expected results are:
i) the calculation of the response functions MBPT using the GW approximation and the solution of the Bethe-Salpeter equation (BSE), which explicitely contains the dynamics of the electron-hole pairs. We will able to develop approximations that boosts the efficiency without sacrificing >>>

Timescale

24 months

National and international background

Semiconductor device fabrication shows a remarkable trend towards miniaturization, driven by many scientific and technological innovations. The size of device components is now reaching the nanometric scale, which is the actual fabrication technological limit. This limitation could be overcome by substituting traditional inorganic semiconductor components with single nanostructures, such as nanocrystals nc), nanowires(nw), nanotubes(nt), or organic molecules[1]. For example, during the past decade, several breakthroughs have increased the hopes of using nanostructured silicon as an optical active material[2]. The basic idea has been to take advantage of the reduced dimensionality of the nanocrystalline phase[3]. New devices incorporating Si nanostructures have attract effort of research for their optical features in the photonic branch[3].Since optical gain from Si-nc embedded in a Si02 matrix has been demonstrated[4,5],the possibility to use Si for optoelectronics is becoming reliable.An efficient electrical carrier injection for embedded Si-nc has been developed[6].The first Raman Si Laser[7] using Si waveguide as the gain medium has been realized,and improved[8] implanting impurities,converting Si into a material with electron(n-side)and hole(p-side) conduction. Indeed Si-nw are emerging as a powerful building blocks for the integration of photonics devices on a chip[9]. Photovoltaic conversion of solar energy, from photons to electrons, has so far been dominated by >>>