J Deneen

Microscopy of nanoparticles for semiconductor devices

The miniaturization of semiconductor devices brings the impending need for nanoscale components for which nanoparticles of semiconductor materials are uniquely suited. However, their small length scales are known to produce properties unique from those of their bulk form. Full characterization of the nanoparticles suggested for use in devices becomes imperative. This study investigates silicon nanocubes prepared by a constricted-mode capacitive silane-argon plasma. These cubes have been proposed as key components in nanoscale transistors. Various techniques are used to examine these particles and their implementation in a potential device is explored.

Defects and interfaces in nanoparticles

As the dimensions of semiconductors are reduced into the nanoscale, the defects and interfaces that may be present have taken on new importance. In many cases, these nanoscale materials may have properties that are unique to their size and morphology. Using the transmission electron microscope, observations of these interfaces can shed light on the possible formation processes undergone by the nanoparticles and lead to further advances in nanoscale semiconductor manufacturing.

The Effects of Processing on the Morphology of Nanoparticles

One of the major challenges confronting the utilization of nanoparticles in industrial and social applications is that of producing the nanoscale materials. Of the methods of manufacturing nanoscale materials, processes involving plasmas have been shown to be cost-effective and versatile in the production of chemically diverse material. Using transmission electron microscopy, individual nanoparticles produced by a thermal plasma-based production method have been examined. The observations of these studies imply that the thermal history of the nanoparticles during formation is of great importance in the determination of the resulting nanoparticle morphology. Such results have the potential to enable the manufacturing of nanoparticles of a specific size and shape from plasmas.

TEM study of the morphology of nanoparticles

The use of nanoparticles in various applications requires consistent production of particles with uniform size and shape, especially since it has been widely shown that their properties can deviate from bulk behavior at this small scale [1, 2]. Nanoparticles tend to differ from bulk material in part because their surface to volume ratio is much larger. Very small particles can have morphologies which differ from that of bulk material if this provides for lower-energy surfaces. Clearly, since the surface is so important for such small particles, it is crucial to know which surfaces are present in order to understand and model their properties.

Interfaces of ZnO Nanowires Grown on Semiconducting Surfaces

The large direct band gap of ZnO makes it an important semiconductor. ZnO can be grown in the form of nanowires on various substrates, which makes it a potential candidate for nanoparticle-based device applications such as heterojunction solar cells. Aligned nanowires of ZnO can be grown on semiconductor surfaces to make p–n junctions. The characteristics and performance of devices are critically dependant on the alignment, distribution and the nanowire–substrate interface character. While various methods to control the alignment and distribution of ZnO nanowire on different surfaces have been reported in the literature [1], the structure of the interface between the ZnO nanowire and the semiconducting surface is almost unknown. The motivation of this work is to characterize the interface of ZnO nanowires grown on a Si surface.

Single nanoparticle semiconductor devices

Using a new technique in forming the cubic single-crystal silicon nanoparticles that are about 40 nm on a side, the authors have demonstrated a vertical-flow surround-gate Schottky-barrier transistor. This approach allows the use of well-known approaches to surface passivation and contact formation within the context of deposited single-crystal materials for device applications. It opens the door to the novel three-dimensional integrated circuits and new approaches to hyper integration. The fabrication process involves successive deposition and planarization and does not require nonoptical lithography. Device characteristics show reasonable turn-off characteristics and on-current densities of more than 107 A/cm2

Characterization of defects in ZnS and GaN

The compound semiconductors ZnS and GaN both exhibit a wide direct bandgap and chemical and thermal stability. ZnS can be grown as long belt-like structures, making it potentially useful as a nanoscale component in electronic devices. Since the properties of nanoscale materials typically differ from those of their bulk counterparts, a fundamental understanding of the structure of the ZnS nanostructures is essential, particularly since they contain significant numbers of planar defects. Commercial samples of GaN also contain large numbers of planar defects which are not well understood. The present study will discuss similar defects in the two materials.

Mechanical Response of Semi-Brittle Nano Particles under an Imposed Cyclic Field

In elastic plastic solids, approaching the sub micron scale, critical experiments indicated significant differences in the mechanical response. Thus, mainly in small volume behavior a length scale issue is introduced with implications on the basic understanding of deformation and fracture processes. The current study is centered on the mechanical response of silicon particles in the range of 20-50 nm on sapphire substrate. Monotonic and cyclic mechanical tests have been performed by contact mechanics methodology at ambient temperature. Mechanical information and visualization assisted by scanning probe microscope-based nano indentation alluded to a model founded on dislocation dynamic effects. This facilitated developments regarding the length scale subject in the light of fatigue concepts and structural integrity aspects.