Paper SS+EM-WeA11
Wet Chemical Approach for Amino Functionalization of Oxide-free Si(111) Surfaces
Wednesday, October 31, 2012, 5:20 pm, Room 22
| Session: |
Semiconductor Surfaces |
| Presenter: |
T. Peixoto, University of Texas at Dallas |
| Authors: |
T. Peixoto, University of Texas at Dallas
P. Thissen, University of Texas at Dallas
Y.J. Chabal, University of Texas at Dallas
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| Correspondent: |
Click to Email |
The ability to functionalize H-terminated Si surfaces with NH2 groups is crucial for a number of applications, such as biomedical (bio-sensors), solid diffusion barrier films, single electron devices, MOSFETs and MEMS. The Si-N bond provides a versatile functionality for chemical modification. Although the creation of a well-defined and stable interface for the Si-N bonds has remained elusive, chlorosilanes have been shown to easily react with gas-phase or liquid ammonia and primary and secondary amines to achieve a stable silicon nitride bond1.
For fluorosilane surfaces, we have performed DFT calculations indicating that the kinetic barrier for the NH3 reaction with Si-F surfaces is only slightly higher than for Si-Cl surfaces, suggesting the reaction should occur at moderate temperatures (<70oC). The 1/3 ML Si-F and 2/3 ML Si-H nanopatterned2 model surface has a tailorable distance between Si-F groups (from 6.8 Å for 1/3ML to 3.9 Å at higher coverages) allowing the adsorption mechanism to be investigated in detail (and evaluated by DFT calculations) and the role of NHx-NHx interactions explored. We further show that the Si-F surface reacts with amino containing molecules (NH2-R-NH2), as evidenced by the reaction between Si-F and ethylenediamine at room temperature. Using these reactions we demonstrate that the amidation for the nanopatterned surface takes place for both small molecules (NH3) and larger amino chains (NH2-CH2-CH2-NH2) with similar kinetics. The surfaces were characterized using Fourier-transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) to verify reaction mechanisms.
These results provide a fundamental understanding of the amidation reaction mechanism for achieving stable Si-N bonds using fluorosilanes surfaces. Achieving a well-defined and stable Si-N interface is significant for a number of important technological applications.
References:
[1] Tian, F.; Taber, D.F.; Teplyakov, A.V. J. Am. Chem. Soc.2011, 133, (20769)
[2] Michalak, D. J.; Amy, S. R.; Aureau, D.; Dai, M.; Esteve, A.; Chabal, Y. J. Nat. Mater.2010, 9, (266).