Congresos y reuniones científicas
Título:
The Role of the Organic Layer Functionalization in the Formation of Silicon/Organic Layer/Metal Junctions with Coinage Metals
Autor/es:
E. M. PATRITO; F. SORIA; M. F. JUÁREZ; P. PAREDES OLIVERA
Reunión:
Congreso; 2012 MRS Spring Meeting; 2012
Institución organizadora:
Materials Research Society
Resumen:
Introducing
organic molecules in electronics is limited by the ability to connect them
electrically to the outside world. This involves the formation of top metal
overlayers on the organic surfaces. This is not a trivial task because most
known methods to make such contacts are likely to damage the molecules [1].
Understanding the atomic and molecular level interaction of metal atoms with
organic surfaces is becoming increasingly important as the number of
applications involving metalâ??organic interfaces grows. The design of silicon/alkyl
layer/metal junctions for the formation of optimal top metal contacts requires
the knowledge of the mechanistic and energetic aspects of the interactions of
metal atoms with the modified surface. This involves a) the interaction of the
metal with the terminal groups of the organic layer, b) the diffusion of metal
atoms through the organic layer and c) the reactions of metal atoms with the
silicon surface atoms. The diffusion through the monolayer and the metal
catalyzed breakage of Siâ??C bonds must be avoided to obtain high quality
junctions. In this work we developed a complete mechanistic and energetic
picture of all the processes involved in the formation of silicon/alkyl
layer/metal junctions. Our results are in agreement with the available experimental
observations and provide detailed information on the reaction pathways and
energy barriers involved in the formation of the junction. We performed a
comprehensive density functional theory investigation to identity the reaction
pathways of all the processes involved [2]. The diffusion of gold atoms through
the alkyl layer was compared for two systems: compact alkyl monolayers on
Si(111) and compact alkanethiol monolayers on Au(111). In the absence of a
reactive terminal group, gold atoms penetrate through the monolayers with small
energy barriers. However, the presence of thiol terminal groups introduces a
high energy barrier which blocks the diffusion of metals into the monolayer. On
the alkylated Si(111) surface, the diffusion barriers increase in the order Ag
< Au < Cu and correlate with the stability of metalâ??thiolate complexes
whereas the barriers for the formation of metal silicides increase in the order
Cu < Au < Ag in correlation with the increasing metallic radii. The
reactivity of gold clusters with functionalized Si(111) surfaces was also
investigated. Metal silicide formation can only be avoided by a compact
monolayer terminated by a reactive functional group. The mechanistic and
energetic picture obtained in this work contributes to understand the factors
that influence the quality of top metal contacts during the formation of
silicon/organic layer/metal junctions.