A silicon structure for electrical characterisation of nanoscale elements

Abstract

The problem of mass manufacturing electrode structures suitable for contacting nanoscale elements lies primarily in the difficulty of fabricating a nanometre-scale gap between two electrodes in a well controlled, highly parallel manner. In ULSI circuit production, the gate and substrate in MOSFETs are routinely fabricated with a precise vertical spacing of 3 nm between them. In this work, we have investigated a number of highly parallel methods for the generation of nanogaps, including reconfiguration of the ubiquitous MOS device structure. The silicon dioxide layer that provides vertical separation and electrical insulation between two regions of silicon (the crystalline substrate and the poly-crystalline gate) gives a leakage current of 1 nA μm−2 at 1 V for an oxide thickness of 2 nm [1]. This will enable objects the size of single molecules that are held across this layer to be detected electrically if they provide currents on the nanoampere scale, assuming a parasitic area for leakage between gate and substrate of order 1 µm2. In the future this kind of device has the potential to provide a bolt-on technology for the fabrication of ULSI circuits in which conventional CMOS devices are directly hybridised with functional nanoscale elements.

Scanning Tunneling Microscopy of Self-Assembled Phenylene Ethynylene Oligomers on Au(111) Substrates

“…Its monothiolated analogue has shown NDR in nanopore experiments 2 and in c-AFM. 7 We use dithiols instead of monothiols, because they allow a well-defined adsorption of molecules in two-terminal devices, such as gold nanogaps 13 or break junctions, provided such gaps can be produced with the correct width. In contrast to nanopore experiments, where typically thousands of molecules contribute to the measurement, the STM permits a very local conductivity measurement that only contacts very few molecules at a time.…”

Electrical and optical properties of semiconductor nanocrystals

“…Previous work has used alkanedithiol linker molecules to attach semiconductor nanocrystals between metal nanoelectrodes (Klein et al 1996(Klein et al , 1997. In the future it may be advantageous to attach nanocrystals directly to semiconductor electrodes, both for ease of integration with existing semiconductor technology and possibly to allow the construction of resonant tunnelling devices exploiting the quantized energy levels in the nanocrystals (Sazio et al 2001).…”

Self-Assembled Monolayers of CdSe Nanocrystals on Doped GaAs Substrates

“…3,4 Semiconductor electrodes may in the future provide an attractive alternative to metals, since nanometer-sized gaps may be fabricated by selective etching of semiconductor heterostructures in wafer-scale processes that are compatible with traditional semiconductor processing methods. 5 These structures might show interesting electrical properties, perhaps similar to the negative differential resistance that is observed in resonant tunneling diodes where a quantum-confined system is placed between two doped semiconductor "leads". Characterization of nanocrystals and molecules attached to semiconductor surfaces is therefore an important area of research, and here we study the assembly of CdSe nanocrystals on GaAs surfaces using alkanedithiols as linkers.…”

“…Both organic molecules and inorganic nanocrystals have been investigated as suitable active elements. Devices have typically been fabricated using planar metal electrodes to contact a monolayer of organic molecules, , or using nanometer-sized gaps between metal electrodes to contact small numbers of molecules or nanocrystals. , Semiconductor electrodes may in the future provide an attractive alternative to metals, since nanometer-sized gaps may be fabricated by selective etching of semiconductor heterostructures in wafer-scale processes that are compatible with traditional semiconductor processing methods . These structures might show interesting electrical properties, perhaps similar to the negative differential resistance that is observed in resonant tunneling diodes where a quantum-confined system is placed between two doped semiconductor “leads”.…”