AVS 52nd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM1-ThM

Paper EM1-ThM5
Metal Molecule Silicon Devices

Thursday, November 3, 2005, 9:40 am, Room 309

Session: Molecular Electronics
Presenter: A. Scott, Purdue University
Authors: A. Scott, Purdue University
D.B. Janes, Purdue University
Correspondent: Click to Email
While the majority of molecular electronic devices have employed metal contacts, semiconductor contacts could allow more stable chemical bonds and enhanced electrical functionality. Integrating molecular devices on silicon is a promising approach to molecular electronics@footnote 1@ and would leverage capabilities of the microelectronics industry. In this study, metal-molecule-silicon devices have been fabricated and characterized. Molecules are grafted to 111 silicon surfaces by electrochemical reduction of diazonium salts,@footnote 2@ resulting in robust molecular layers that are covalently bound to the surface by C-Si bonds. Aromatic molecules with various headgroups have been grafted to Si and characterized using infrared spectroscopy and cyclic voltammetry. Metal top contacts are deposited using an indirect evaporation technique which minimizes metal penetration, as demonstrated previously on GaAs.@footnote 3@ Electrical testing of these devices indicates that transport can be modulated by both substrate doping and molecular chemistry. If a large metal-semiconductor barrier is present and the substrate is lightly doped, the current-voltage characteristics are only slightly modified by the addition of a molecular layer. N-type Si-Au Schottky diodes (N@sub D@=10@super 15@cm@super -3@) have current densities of 3 A/cm@super 2@ at 0.5 volt, and the addition of a molecular layer reduces the current density by less than an order of magnitude. In devices where the barrier height is small and the substrate heavily doped, transport is more dominated by molecular effects. P+ (N@sub A@=10@super 19@cm@super -3@) Si-Au Schottky diodes exhibit current densities of 10@super 6@ A/cm@super 2@, and the addition of a molecular layer decreases this by 1 to 4 orders of magnitude depending on the molecular species. @FootnoteText@ @footnote 1@Guisinger et al., Nano Let. 55-59, 2004@footnote 2@Allongue et al.,JEAC 161-174, 2003@footnote 3@Lodha and Janes, APL, 2809-2811, 2004.