1 © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com Fabrication of Reproducible, Integration-Compatible Hybrid Molecular/Si Electronics Xi Yu, Robert Lovrinc ˇic ´, Olga Kraynis, Gabriel Man, Tal Ely, Arava Zohar, Tal Toledano, David Cahen,* and Ayelet Vilan* because of the huge conformational flexibility of molecules at room temperature compared to non-molecular inorganic solids. Thus, incorporating molecules in a solid electrical junc- tion toward their reliable use for “molecular electronics” is no less a challenge of self-assembly and surface chemistry than of molecular synthesis. A major shortcoming of molec- ular electronics is the wide spread in performance, often over orders of magnitude of supposedly identical systems/devices. This variability is attributed to transport by tunneling, [1] the efficiency of which varies exponentially with the length of the tunneling path and with the energy difference between the electrode’s Fermi energy, E F , and the molecular levels closest to E F . Therefore, reproducibility is reported as standard deviations of log(current), σ log10 , [2,3] with narrowest reported values of σ log10 = 0.3. [2a,4] Valid scientific information can be extracted despite the poor reproducibility by relying on a large number of measurements (statistics) [2,5] or focusing on spectroscopic aspects, such as transition voltage [6] or inelastic electron tunneling spectroscopy (IETS). [7] Nevertheless, Reproducible molecular junctions can be integrated within standard CMOS technology. Metal–molecule–semiconductor junctions are fabricated by direct Si–C binding of hexadecane or methyl-styrene onto oxide-free H-Si(111) surfaces, with the lateral size of the junctions defined by an etched SiO 2 well and with evaporated Pb as the top contact. The current density, J, is highly reproducible with a standard deviation in log(J) of 0.2 over a junction diameter change from 3 to 100 μm. Reproducibility over such a large range indicates that transport is truly across the molecules and does not result from artifacts like edge effects or defects in the molecular monolayer. Device fabrication is tested for two n-Si doping levels. With highly doped Si, transport is dominated by tunneling and reveals sharp conductance onsets at room temperature. Using the temperature dependence of current across medium-doped n-Si, the molecular tunneling barrier can be separated from the Si-Schottky one, which is a 0.47 eV, in agreement with the molecular-modified surface dipole and quite different from the bare Si–H junction. This indicates that Pb evaporation does not cause significant chemical changes to the molecules. The ability to manufacture reliable devices constitutes important progress toward possible future hybrid Si-based molecular electronics. Molecular Electronics DOI: 10.1002/smll.201400484 Dr. X. Yu, Dr. R. Lovrinc ˇic ´, [+] O. Kraynis, G. Mann, [++] T. Ely, [+++] A. Zohar, T. Toledano, Prof. D. Cahen, Dr. A. Vilan Department of Materials and Interfaces Weizmann Institute of Science P.O.B. 26, Rehovot 76100, Israel E-mail: david.cahen@weizmann.ac.il; ayelet.vilan@weizmann.ac.il [+] Institute for High-Frequency Technology, TU Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany [++] Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA [+++] Stratasys, 2 Holtzman St. Rehovot 76124, Israel 1. Introduction Molecules are considered as the ultimate nm-sized building units with composition, structure and function that are in principle controllable. In reality, this view is deceptive small 2014, DOI: 10.1002/smll.201400484