Si Cones Research Articles

Microstructural characterization of Si cones fabricated by Ar +-sputtering Si/Mo targets

Ar + sputtering of Si wafers surrounded by Mo plates induced the formation of uniform cones over a large area on the Si surface. Scanning electron microscopic study showed that the cones were formed on the entire surface of the Si wafer. The uniform cones were 0.4–0.7 μm in diameter and 5–6 μm high. They were further characterized by means of cross-sectional transmission electron microscopy, and micro-diffraction. It was found that the cone contained a pure Si regime and a Mo-rich regime. In the binary Mo–Si zone, we identified three distinct areas vertically: (1) domains of Mo-induced Si ordered structures; (2) a small volume of a new Mo 3Si 2 structural variant, intergrown with the Si ordered structure; and (3) a small amount of pure Mo nanoparticles covering the surface of the cones. The formation of the large and uniform cones may provide a new surface configuration for potential applications in surface science and technology.

Influence of the composition of a NbNx thin-film field emitter array on emission characteristics

We fabricated NbNx thin-film field emitter arrays by the ion beam assisted deposition technique which can prepare transition-metal nitride thin films at a relatively low temperature of about 500 °C. The emitter arrays were fabricated by depositing NbNx thin films on Si cones. The nitrogen composition of the film is controlled by selecting the deposition condition, such as the arrival rate ratio of N to Nb flux. We investigated the influence of the nitrogen composition of the NbNx thin-film field emitter arrays on electron emission characteristics. The emitter arrays with a higher nitrogen composition emitted electrons at a lower voltage and showed more stable emission than those with a lower composition. We compared the emission stability of the NbNx emitters with that of the Si emitters. The emission from the NbN emitter (composition ∼1.0) was more stable than that from the Si emitter by a factor of 10 in terms of the noise power.

High-resolution electron microscopy of Si cones formed on Ar+-bombarded Si wafers

Conical Si projections generated on Si wafers bombarded with obliquely incident Ar+ ions were studied by high-resolution transmission electron microscopy. The cones were composed of an [111]-oriented bulk phase covered with a disordered thin layer, but the bulk phase was not perfectly ordered, containing an amorphous domain underneath the outermost area. Such a multi-phase structure is inexplicable in terms of ion erosion, suggesting interplay of the redeposition of sputtered Si atoms on the bombarded area with the ion-erosion process so as to promote cone evolution. The cones were also characterized by the development of web-like platelets at their acute angles, an indication of a crystal growth process involved in the surface phenomenon observed.

High-resolution electron microscopy of Si cones formed on Ar+-bombarded Si wafers

High-resolution electron microscopy of Si cones formed on Ar+-bombarded Si wafers