This project, supported by the Solid State and Materials Chemistry Program, aims to provide a new means of synthesizing and designing functional and stable inorganic-organic interfaces for exploitation across a wide range of applications, such as selective, high-sensitivity chemical and biological sensors and efficient photon harvesting platforms. The traditional synthesis approach for attaching molecular overlayers to semiconductors creates minimal modifications to the inorganic support except to 1) remove any surface oxide present pre-attachment, and 2) attach appropriate molecular linking groups, if needed. A key requirement for device exploitation is therefore the creation of a highly - dense overlayer that impedes re-oxidation of the interface. The goal of this project is to demonstrate the feasibility of using oxides designed as chemical templates that impact molecular attachment by inhibiting or enhancing different chemical reaction pathways. This approach will be used to ultimately create a stable, functional interface. An emphasis on determining the key chemical reactions governing cysteamine and succinic acid attachment to InAs, a model III-V semiconductor, is the focus of this effort with the goal of developing a follow-on application-focused materials/device proposal to NSF.
NON-TECHNICAL SUMMARY Inorganic-organic interfaces are the heart of a new generation of electronic and photonic devices. This research project aims to create more stable and higher performance interfaces designed for devices used in energy and sensing applications. The core of the effort is to design oxide interface materials that control the attachment of molecules to device surfaces yielding new performance regimes and higher reliability. The project marries the critical disciplines of chemistry, materials science, and engineering and, as such, students will derive considerable educational benefit from the experience gained working across these boundaries. This project involves collaboration between Prof. April Brown, Duke University, Dept. of Electrical and Computer Engineering, Dept. of Biomedical Engineering, and Dr. Maria Losurdo, CNR-Bari, Italy. The exchange of students between Duke and CNR in this multidiscipline effort also provides significant enhancements to their education.
Semiconductor devices are crucial to the global economy and quality of life. A key to advancing the use of devices especially in the area of medical sensors is the controlled attachment of molecules to the surfaces of such devices. Such molecules can target specific molecules in the air or fluids to bind them and create an electronic signal reading out the event. During our project we explored a novel approach to controlling molecular attachment by modifying the surface of the semiconductor by changing its composition and, therefore, how it oxidizes upon air exposure. Different molecular groups will interact differently with the oxide phases. Through understanding these relationships we hope to create a more stable interface between the molecules and the semiconductor and, ultimately to create a chemical template that can control how molecules bind to the surface. During this one year project, we demonstrated the tight coupling between the chemical and electronic properties of the surface of InAs, an important III-V semiconductor for high frequency electronics and future next-generation CMOS devices. In addition, we mapped out the chemical relationships between a set of molecules and different phases of the surface oxide in terms of the formation of specific molecular bonds. We found that the current in a simple device is highly sensitive to the specific chemical interactions.
