Organic molecular films on semiconductors for device applications

The functionalisation of semiconductors through the direct attachment of organic molecules to their surfaces is an emerging area of fundamental research that will lead to the creation of new and exciting functional devices. This activity brings together the enormous breadth of functionality and tailorability of organic molecules-including their chemical, bio-chemical, physical, electronic, and optical properties-with the highly sophisticated and massively parallel capabilities of todays semiconductor processing techniques and technology. In addition to the obvious advantages for incorporating molecular functionality with existing semiconductor devices, semiconductor surfaces are particularly attractive hosts on which to bind molecules because of the robust covalent attachments that organic molecules form with semiconductor surfaces; this often leads to structures that are highly stable, even at room temperature or above. In addition, it is anticipated that organic molecules will form the basis of novel devices where individual molecules are incorporated as active elements (molecular electronics), and their use could extend to ultra-high density information storage applications and quantum computing. However, such applications require a detailed understanding of the interfaces between these molecules and the surfaces to which they are bound. It is therefore critical for the fabrication of such devices and the proper understanding of the science that underpins their operation that we: (1) develop a detailed understanding of the fundamentals of the organic-semiconductor interface; and (2) develop methods and techniques for the creation of defect-free and thermally stable organic layers on semiconductors with the ability to tune the properties of the molecular layer. The aim of the proposed research is to investigate the functionalisation of semiconductor surfaces with organic molecules through the formation of stable, covalently bound, low defect density, homogeneous and heterogeneous organic layers and multilayers on semiconductor surfaces. The techniques that will be applied are scanning tunnelling microscopy and spectroscopy (STM/STS); synchrotron X-ray methods such as photoelectron spectroscopy, X-ray standing wave spectroscopy (XSW) and near-edge X-ray adsorption fine structure spectroscopy (NEXAFS); and atomic force microscopy (AFM) and conductive AFM (cAFM). The major goal of this project is to find ways to maintain the strong advantages provided by the semiconductor substrate when forming organic overlayers; i.e., to maintain the highly homogenous, highly periodic, and highly reproducible nature of the atomically clean and flat semiconductor surface within the organic film

The main beneficiaries of this research will be academic and industrial researchers with interests in the molecular functionalisation of semiconductor materials. In the immediate term, this research is likely to be of most interest within the organic electronics community where knowledge of the mechanisms of charge transport through organic molecules and across organic-semiconductor interfaces is of interest. There is also potential for this work to impact within the rapidly growing and potentially lucrative organic display industry. In the longer term, there may be impacts within scientific and industrial biomolecular communities in the areas of biomolecule immobilisation and biocompatible implants. Benefits to the general public will be of a general interest nature in the short term, e.g., through publication of the work in non-specialist literature. In the longer term the public will benefit through the potential technological applications such as electronic, computational, light emitting, or biofunctional devices, as well as the associated economic benefits for the UK.