Method of selectively aligning and positioning nanometer-scale components using AC fields

#The present invention relates to an assembly technique to facilitate the transport measurements of electronic molecules, and more particularly to a method of selectively aligning and positioning and assembling nanometer-scale components using alternating current (AC) electric fields.

#Molecular electronics is a rapidly growing field and is providing for a means to overcome the miniaturization limits that Si technology is approaching. Molecules and nanometer-scale components, with unique functionality are considered possible candidates for molecular electronics. One of the challenges facing molecular electronics is communicating the information/functionality of the molecules to the “outside” world. In order to accomplish this, a simple and robust procedure needs to be developed to selectively place and “wire” nanometer-scale components, such as molecules, to metal electrodes. A rapid screening method to “hook-up” candidate molecules to be tested and determine their functionality is also considered a crucial step toward molecular electronics.

#Assessing the feasibility of molecular electronics requires the screening of a large number of nano-scale components, for their potential applications. The main challenge is to make electrical contact to molecules to determine their transport properties. For instance, typical dimensions of molecular systems are well below the resolution limits of electron beam lithography. Although various fabrication approaches have been proposed, a quick and simple way to make measurements on a small number of molecules still remains a challenge.

#The foregoing and further and more specific objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings, in which:

#FIGS. 1 and 2 illustrate in a simplified cross-sectional views, steps in the method of selectively aligning and positioning a nanometer-scale component according to the present invention;

#FIG. 3 illustrates in a simplified isometric view the selective alignment of a nanometer-scale component according to the method of selective alignment of the present invention;

#Disclosed is a molecular assembly technique using an alternating current (AC) electric field to facilitate selective alignment and transport measurements of electronic nanometer-scale components. The term nanometer-scale components, for purposes of this disclosure, is intended to include nanoparticles, nanotubes, nanowires, nanorods, synthetic polymers, synthetic molecules, and biomolecules, including DNA molecules, proteins, or the like. With the appropriate choice of amplitude and frequency, the use of an AC bias dramatically enhances the placement of desired nanometer-scale components over other contaminant species in the solution, such as in a solution containing carbon nanotubes and organic or inorganic contaminants.

#Referring now to FIGS. 1-2 illustrated in simplified cross-sectional views is an assembled structure utilized for selective alignment of nanometer-scale components according to the present invention and the method of using the structure to provide for selective alignment. More specifically, illustrated in FIG. 1 is a first step in the method of selectively aligning and positioning nanometer-scale components, wherein provided is a molecular assembly 10 including two or more electrodes (discussed presently). Assembly 10 in this particular embodiment includes a substrate 17, comprised of a semiconductor material 16 which has been coated with an insulating material 18. It should be understood that anticipated by this disclosure is an alternate embodiment in which substrate 17 is formed as a single layer of insulating material, such as glass plastic ceramic, or any dielectric material that would provide insulating properties. By forming substrate 17 of an insulating material, the need for a separate insulating layer formed on top of a semiconductive layer, or conductive layer, such as layer 18 of FIG. 1, is eliminated.

#In the embodiment illustrated in FIGS. 1-2, semiconductor material 16 is disclosed as comprised of any semiconductor material well known in the art, such as silicon (Si), gallium arsenide (GaAs), germanium (Ge), silicon carbide (SiC), indium arsenide (InAs), or the like. Insulating material 18 is disclosed as comprised of any material that provides insulative properties such silicon oxide (SiO2), silicon nitride (SiN), or the like. Together semiconductor material 16 and insulating material 18 form substrate 17 as illustrated in FIGS. 1-2. In this specific example, assembly 10 includes a first electrode 12 and a second electrode 14 formed on an uppermost surface of insulating material 18. Fabrication of metal electrodes 12 and 14 is carried out using a combination of photolithography and electron beam lithography on an oxidized silicon substrate 17. Fine features of electrodes 12 and 14 are patterned by a standard PMMA resist process using standard liftoff technique. Electrodes 12 and 14 are formed to define therebetween a gap 20 and provide for the application of an AC electric field (as illustrated in FIG. 2).