The promise of advanced neuroprosthetic systems to significantly improve the quality of life for a segment of the deaf, blind, or paralyzed population hinges on the development of an efficacious, and safe, multichannel neural interface for the central nervous system. The candidate implantable device that is to provide such an interface must exceed a host of exacting design parameters. We present a thin-film, polyimide-based, multichannel intracortical Bio-MEMS interface manufactured with standard planar photo-lithographic CMOS-compatible techniques on 4-in silicon wafers. The use of polyimide provides a mechanically flexible substrate which can be manipulated into unique three-dimensional designs. Polyimide also provides an ideal surface for the selective attachment of various important bioactive species onto the device in order to encourage favorable long-term reactions at the tissue-electrode interface. Structures have an integrated polyimide cable providing efficient contact points for a high-density connector. This report details in vivo and in vitro device characterization of the biological, electrical and mechanical properties of these arrays. Results suggest that these arrays could be a candidate device for long-term neural implants.

A variation in the saturated phase-breaking time in a ballistic quantum dot is found to occur as the size is varied. This variation differs from that observed earlier, in which a transition from quasi-twodimensional to zero-dimensional behavior was thought to occur. Instead, these results suggest that the saturated phase-breaking rate is governed by a change in the total number of electrons within the dot. At higher temperatures, the phase breaking is governed by coupling to the quantum wire leads, and t f may show the T 22͞3 variation expected for a one-dimensional wire due to the electron-electron interaction.[S0031-9007(99)

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The two-dimensional electron gas formed at the inverted surface of a tilted silicon substrate shows unusual magnetotransport properties due to the presence of a minigap in the density of states. For metal–oxide–semiconductor inversion layers the strong scattering at the interface limits the mobility to values μ<10–20 000 cm2/V s. To achieve mobilities approaching 105 cm2/V s we have used strained Si:SiGe quantum wells grown on substrates tilted away from the (001) normal by 0°, 2°, 4°, 6°, and 10°. Their transport properties have been measured in the temperature range of 20–500 mK. All the samples show strong Shubnikov–de Haas oscillations. For the 2° and 4° samples the envelope of the fast oscillations is modulated by a longer period oscillation at low magnetic fields. We attribute the slow oscillation in the 2° and 4° samples to the presence of a minigap. For the 6° and 10° samples the minigap is higher than the Fermi energy and is not expected to influence the transport properties.

Future VLSI scaling realization of gate lengths is expected to 70 nm and below. While we do not know all the underlying physics, we are beginning to understand some limiting factors, which include quantum transport, in these structures. The discrete nature of impurities, the fact that devices have critical lengths comparable to their coherence lengths, and size quantization will all be important in these structures. These phenomena will lead to pockets of charge, which will appear as coupled quantum dots in the device transport. We review some of the physics of these dots.