Self-integration of nanowires into circuits via guided growth

Abstract

The ability to assemble discrete nanowires (NWs) with nanoscale precision on a substrate is the key to their integration into circuits and other functional systems. We demonstrate a bottom-up approach for massively parallel deterministic assembly of discrete NWs based on surface-guided horizontal growth from nanopatterned catalyst. The guided growth and the catalyst nanopattern define the direction and length, and the position of each NW, respectively, both with unprecedented precision and yield, without the need for postgrowth assembly. We used these highly ordered NW arrays for the parallel production of hundreds of independently addressable single-NW field-effect transistors, showing up to 85% yield of working devices. Furthermore, we applied this approach for the integration of 14 discrete NWs into an electronic circuit operating as a three-bit address decoder. These results demonstrate the feasibility of massively parallel "self-integration" of NWs into electronic circuits and functional systems based on guided growth.T he sustained progress in semiconductor technology introduces new challenges associated with the scaling and functionality of nanosize components. In the face of these challenges, alternative unconventional device and fabrication concepts based on bottom-up assembly of synthetic nanostructures are being intensively explored (1). These nanostructures, such as quantum dots (2), nanotubes (3), and nanowires (NWs) (4), can be chemically synthesized with exquisite control over their structures and properties down to the atomic level. On the other hand, their self-assembly alone is unlikely to produce the arbitrary geometries and long-range order that are required for their integration into functional systems. To realize such systems, bottomup assembly may be used as a complementary step in a sequence of top-down fabrication processes. Such a hybrid top-down/ bottom-up approach can be based on the directed self-assembly of building blocks onto a lithographically produced template to fit the design of an integrated functional system. Thus, the building blocks integrate themselves into the system, as one of the layers in the overall design. Here we demonstrate the feasibility of this "self-integration" concept with the parallel fabrication of large numbers of devices and complex circuits, based on guided growth of horizontal NWs (5).NWs are attractive building blocks for the bottom-up assembly of nanoscale devices and functional systems with potential applications in nanoelectronics (6), photonics (7), renewable energy (8), and biology (9). They can be synthesized with precisely controlled nanoscale dimensions and chemical compositions (10). Moreover, they may be structured to possess unique electronic properties, such as ballistic conductivity due to confinement of a 1D charge-carrier gas in core-shell NWs (11). The potential of NW-based electronics has been demonstrated for various NW materials (12). However, most studies were done at the single-device level. The main obstacle toward NW integration...

Nanowire nanocomputer as a finite-state machine

“…The multitile nanoFSM and 2-bit full adder programmable circuits demonstrated above highlight several distinct features compared with previous circuits based on bottom-up-assembled elements (8)(9)(10)(11)(12)(13)(14)(15)(16)(17). First, the complexity is more than threefold in terms of number of devices (180 transistor elements) compared with all of the previous work (9)(10)(11)(12)(13)(14)(15)(16)(17), with the density of devices in the nanoFSM also much greater.…”

“…First, the complexity is more than threefold in terms of number of devices (180 transistor elements) compared with all of the previous work (9)(10)(11)(12)(13)(14)(15)(16)(17), with the density of devices in the nanoFSM also much greater. This complexity is further enhanced in terms of circuit functionality by incorporation of both sequential and combinational logic elements.…”

“…1B) represents a very substantial step forward in complexity compared with previous work (8)(9)(10)(11)(12)(13)(14)(15)(16)(17), given the large number of individual nanowires that must be organized in an efficient and scalable manner and the stringent demands on individual logic devices with respect to input/ output (I/O) voltage matching and control over threshold voltage variation. It also represents an experimental implementation of a bottom-up multitile or modular circuit architecture (8,(20)(21)(22)(23)(24).…”

“…Therefore, much effort has been invested in the nanoelectronics field for the development of novel, alternative, nanometer-scale electronic device and fabrication technologies that could serve as potential routes for ever-denser and more capable systems to enable continued technological and economic advancement (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). These efforts have yielded simple nanoelectronic circuits (3)(4)(5)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) and more complex circuit systems (6, 7) that use novel nanomaterials but are not integrated on the nanometer scale. In this regard, building a nanocomputer that transcends the ultimate scaling limitations of conventional semiconductor electronics has been a central goal of the nanoscience field and a long-term objective of the computing industry.…”

“…Previous efforts have yielded circuit elements that perform simple logic functions using small numbers of individual nanoelectronic devices (8)(9)(10)(11)(12)(13)(14)(15)(16)(17), but have fallen far short of demonstrating the combination of arithmetic and register elements required to realize a FSM. Specifically, integration of distinct functional circuit elements necessitates the capability to fabricate and precisely organize circuit systems that interconnect large numbers of addressable nanometer-scale electronic devices in a readily extensible manner.…”