Black Silicon with high density and high aspect ratio nanowhiskers

Physical properties of black Silicon (b-Si) formed on Si wafers by reactive ion etching in chlorine plasma are reported in an attempt to clarify the formation mechanism and the origin of the observed optical and electrical phenomena which are promising for a variety of applications. The b-Si consisting of high density and high aspect ratio sub-micron length whiskers or pillars with tip diameters of well under 3 nm exhibits strong photoluminescence (PL) both in visible and infrared, which are interpreted in conjunction with defects, confinement effects and near band-edge emission. Structural analysis indicate that the whiskers are all crystalline and encapsulated by a thin Si oxide layer. Infrared vibrational spectrum of Si-O-Si bondings in terms of transverse-optic (TO) and longitudinal-optic (LO) phonons indicates that disorder induced LO-TO optical mode coupling can be an effective tool in assessing structural quality of the b-Si. The same phonons are likely coupled to electrons in visible region PL transitions. Field emission properties of these nanoscopic features are demonstrated indicating the influence of the tip shape on the emission. Overall properties are discussed in terms of surface morphology of the nano whiskers

Hybrid synthesis and processing schemes for highly-ordered polyaniline nanoarchitectures

We report on a newly developed technology for the nanoscale processing of the conducting polyaniline (PANI) with an unprecedented areal patterning order and density control exceeding 0.25 teradot/inch 2 . A simple two-step process is put forward to hierarchically build a large variety of functional PANI nanostructures on virtually any type of flexible or rigid substrates. Using template confinement, through Pt catalyzed electroless growth, highly-ordered arrays of distinct PANI nanowires are produced. Complex three-dimensional (3D) structural control is achieved through a direct pattern transfer using a novel type of resist- and dose-modulated 3D electron beam lithography. The method is scalable and provides a generic approach for nanopatterning surfaces with functional polymers. Aspects of the nanoscale PANI growth mechanism are discussed and the highly controllable, sub-picogram scale fabrication is emphasized. Simple schemes for single PANI nanowire fabrication, processing and device integration are presented. \ua92010 IEEE