Scalable Interconnection and Integration of Nanowire Devices without Registration

Abstract

A general strategy for the parallel and scalable integration of nanowire devices over large areas without the need to register individual nanowire−electrode interconnects has been developed. The approach was implemented using a Langmuir−Blodgett method to organize nanowires with controlled alignment and spacing over large areas and photolithography to define interconnects. Centimeter-scale arrays containing thousands of single silicon nanowire field-effect transistors were fabricated in this way and were shown to exhibit both high performance with unprecedented reproducibility and scalability to at least the 100-nm level. Moreover, scalable device characteristics were demonstrated by interconnecting a controlled number of nanowires per transistor in “pixel-like” device arrays. The general applicability of this approach to other nanowire and nanotube building blocks could enable the assembly, interconnection, and integration of a broad range of functional nanosystems.

Nanowires and Carbon Nanotubes

“…4b; see also Supplementary Information, Fig. S4) yield a peak transconductance, g m ¼ dI d /dV g , of 6 mS with an on current, I on , of $16 mA, an on/off ratio .10 5 and a threshold voltage, V t , of 0.55 V. These values compare well with, or exceed, previous multi-Si NW FETs prepared using Langmuir-Blodgett assembly 8 , and moreover, significant improvements should be possible, for example, by substituting much higher performance Ge/Si core/shell NWs 22 . Importantly, histograms of V t and I on ( Fig.…”

“…1d), which resolve individual Si NWs within the transferred BBF, show that the Si NWs recorded from different areas of this large substrate are well aligned along the upward expansion direction of the bubble. Indeed, the angular deviation of the Si NWs is less than 108 over the entire 150-mmdiameter wafer and represents a very substantial advance over previous studies [4][5][6][7][8] .…”

“…To characterize key features of this method, we first focused on silicon NW blown-bubble films (BBFs), because Si NWs can be produced in high yield with uniform diameters and electronic properties 8,12 . Si NWs were covalently modified using 5,6-epoxyhexyltriethoxysilane, and then combined with an epoxy solution to yield stable and well-dispersed suspensions from 0.01 -0.22 wt% (see Methods).…”

“…To realize such applications, researchers have directed considerable effort to the development of methods of assembly that might ultimately lead to integrated systems. For example, there have been studies of individual or small numbers of NW and NT devices prepared by random deposition, electric field directed assembly 4 , flowassisted alignment 5 , and selective chemical and biological patterning 6,7 , and up to centimetre-scale assembly of NWs using the Langmuir-Blodgett technique 8 . However, it is still unclear whether these methods can be extended to large-scale assembly of NWs and NTs on both rigid and flexible substrates with controlled alignment and density.…”

Nanowire-Based Biosensors

“…The combination of tunable conducting properties of semiconducting NWs (16)(17)(18)(19)(20) and the ability to bind analytes on their surface yields direct, label-free electrical readout, which is exceptionally attractive for many applications (23 -31). We discuss representative examples in which these new sensors have been used for detecting a wide range of biological and chemical species.…”