AVS 60th International Symposium and Exhibition
    Surface Science Wednesday Sessions
       Session SS+EM-WeA

Paper SS+EM-WeA9
Specific Attachment of Ethylenediamine on Modified Si(111) Surfaces

Wednesday, October 30, 2013, 4:40 pm, Room 201 A

Session: Semiconductor Surfaces and Interfaces
Presenter: T. Peixoto, University of Texas at Dallas
Authors: T. Peixoto, University of Texas at Dallas
Y.J. Chabal, University of Texas at Dallas
Correspondent: Click to Email
Silicon nitridation is of fundamental interest to the microelectronics, biotechnology and nanotechnology communities, with its ability to act as an oxygen diffusion barrier for devices while concurrently optimizing the effective dielectric constant. The Si-N bond plays a key role in the stability of silicon nitride layers, used in devices due to its durability and thermal stability; amine groups aid in additional functionalization of surfaces enabling the attachment of quantum dots, nanoparticles, and biological molecules allowing for development of new surfaces/devices. The incorporation of nitrogen groups on the silicon surface thus allows for the creation of modified surfaces with expanded properties and extensive tailorability. Despite these advantages, a clear understanding of the underlying mechanisms towards well controlled nitride and amino group attachment on Si surfaces, is not completely developed.

To uncover the reaction mechanisms, we have performed experiments with several different Si(111) surfaces terminations (SiH, SiF, and SiCl) and reacted with the bifunctional molecule ethylediamine (NH2-CH2-CH2-NH2). With its amine termination on ends of the molecule, ethylediamine makes it possible to obtain amine functionality following Si-N attachment on the surface. Our results indicate that ethylenediamine only physisorbs on hydrogen-terminated Si(111) surfaces, as evidenced by the intensity and high wavenumber of the (N-H) deformation and stretch modes and the binding energy of the main N1s peak in XPS. When exposed to a 1/3 nanopatterned Si(111)-F surface, the intensities of the stretch and deformation modes are consistent with a 1/3 coverage, and their frequencies associated with interacting amine groups expected of an ordered monolayer. Importantly, XPS shows a component of the N1s core level that is associated with direct bonding to silicon. In contrast, ethylediamine molecules appear to adsorb by bridge configuration on fully chlorine-terminated Si surfaces, indicating that both NH2 ends dissociate and react, as evidenced by a dominance of Si-N bonds in XPS and undetectable (N-H) deformation and stretch in IR spectra.

These results provide a means to controlling amine functionalization of silicon surfaces, and further understanding of the reaction mechanism for nitrogen group attachment on F, Cl, H terminated Si(111) surfaces.