Demonstration of Molecular Assembly on Si (100) for CMOS-Compatible Molecule-Based Electronic Devices

Abstract

In this work, we establish the potential of a UV-promoted direct attachment of alkanes with alcohol and thiol linkers to the silicon (100) surfaces for use in molecular electronic devices with increased potential for integration with existing CMOS technologies. Characterization of the self-assembled monolayers via Fourier transform infrared spectroscopy, spectroscopic ellipsometry, and X-ray photoemission spectroscopy shows that the films assembled on the Si (100) are comparable in quality, aliphatic monolayer coverage, and extent of substrate oxidation to those assembled on the more extensively studied Si (111) crystal face. Simple Si (100)-based electronic devices fabricated with the monolayers exhibited molecule-dependent electrical characteristics. These data highlight the effectiveness of the assembly on Si (100), the ability to fabricate enclosed Si (100)-based molecular devices, and the potential for the future integration of these devices with more conventional technologies.

Molecules on Si: Electronics with Chemistry

“…The Si(111) face, and not the industry-used (100) plane, is preferred for wet chemistry because it can be made atomically smooth over a macroscopic area. [10,89] In any case, comparable transport characteristics were observed for MOMS on either Si(111) [97] or Si(100). [88,89] Smoothing is done with 40% NH 4 F and 2% HF for (111) and (100) planes, respectively.…”

“…[10,89] In any case, comparable transport characteristics were observed for MOMS on either Si(111) [97] or Si(100). [88,89] Smoothing is done with 40% NH 4 F and 2% HF for (111) and (100) planes, respectively. [11,88] For work with monolayers, substrate smoothness should extend from a few up to hundreds of mm 2 , depending on the size of the contact, a situation that is very different from that tested in STM/AFM studies.…”

“…Many functionalized groups, apart from alkenes (C¼ À C), [31,69,80,86] can adsorb on H-terminated Si, such as alkynes (C¼C), [87] alcohols, [69,88] aldehydes, [69] thiols (SH) [72,89] or Grignard reagents. [42,83,90] Aromatic molecules are mostly electrochemically adsorbed as diazonium salts [43,62,91] or by photochemical binding of ethynylbenzene.…”

“…This improves the accuracy of the transport measurement, because of smaller net capacitance and a decrease in the ratio of setup (series) to junction resistance. [62,69,71,89] The question here is how clean and flat the Si surface is between the patches of SiOx or photoresist, i.e., after patterning. Common spectroscopies (IR, XPS) cannot be used, as they generally require significantly larger areas.…”

Wet chemical routes to the assembly of organic monolayers on silicon surfaces via the formation of Si–C bonds: surface preparation, passivation and functionalization

“…changes in the band-bending) and alter the conductivity of the substrate. 53,207 This molecular gate 129 approach has stimulated vast research, 43,63,64,129,278 but despite encouraging recent reports, 279 at present the development of real-world molecular electronics, such as high density memories, 40,41 remain a long-term target. Serious practical obstacles toward the fabrication of a real device still exist.…”