AVS 52nd International Symposium
    Electronic Materials and Processing Wednesday Sessions
       Session EM+SS-WeM

Paper EM+SS-WeM9
Self-assembled Monolayers with Reactive Endgroups: Studies of Inorganic-Organic Interfaces and the Initiation of Top Contact Formation

Wednesday, November 2, 2005, 11:00 am, Room 309

Session: Contacts to Organic and Molecular Devices
Presenter: A. Dube, Cornell University
Authors: A. Dube, Cornell University
M. Sharma, Cornell University
A.S. Killampalli, Cornell University
J.R. Engstrom, Cornell University
Correspondent: Click to Email
Self-assembled monolayers (SAMs) have attracted considerable interest over the past several years in the field of molecular electronics. In such applications two interfaces become important, and understanding the formation of both is critical to effectively making use of SAMs in these devices. While formation of the bottom contact is a well studied area, the formation of top contacts is an immature field. We have been examining the reactions of transition metal coordination complexes, such as Ti[N(CH@sub 3@)@sub 2@]@sub 4@ and Ta[N(CH@sub 3@)@sub 2@]@sub 5@, with SAMs possessing different head group chemistries [e.g., RSiCl@sub 3@ on SiO@sub 2@, R-(thiophene) on Au] and endgroup functionalities (e.g., -CH@sub 3@, -NH@sub 2@ and -OH) in order to develop an understanding of interface and contact formation. In this presentation we will highlight our most recent work that includes the self-assembly and reactions of functionalized molecular wires (thiophenes with conjugated ethynyl-phenylene backbones) adsorbed on Au using in situ angle resolved x-ray photoelectron spectroscopy (ARXPS). Here we find that the saturation density of the SAM increases from ~ 2.1 to 3.4 x 10@super 14@ molecules-cm@super -2@ as the length of the conjugated backbone is roughly doubled. More importantly, these layers, which possess an isopropylamine endgroup, react via ligand exchange with Ti[N(CH@sub 3@)@sub 2@]@sub 4@ even at -50 °C, forming a structure that has a Ti:SAM stoichiometry of ~ 1:2. ARXPS shows conclusively that these Ti coordination complexes bond with the SAMs exclusively at the isopropylamine group, and can seed additional deposition of the top contact. We will discuss the importance of these and other results concerning what they say about designing an effective means to make top contacts to molecular monolayer structures.