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Quantum silicon nanowires (SiNWs) arrays have been synthesized by chemical vapor deposition template method without catalyst. The results of SEM and TEM reveal clear alignment of the SiNWs and each nanowire with perfect lattices is a single crystal. The growth mechanism of SiNWs without catalyst is discussed based on VLS mechanism. The unusual pattern in the Raman spectrum may be a unique characteristic of low-dimensional nano-scale materials. Enhanced photoluminescence properties may be associated with the quantum confinement effect and the formation of ordered arrays. Field emission from SiNWs arrays under various anode–cathode distances are analyzed based on Fowler–Nordheim theory. The superior field emission behavior is believed to originate from the oriented growth and the sharp tips of SiNWs. [Copyright &y& Elsevier]

Designed alloy catalysts have shown promise in structure-controlled growth of single-wall carbon nanotubes (SWCNTs). However, due to the high-dimensional growth parameter space and low efficiency of the conventional trial-and-error optimizing approach, it is still challenging to explore and to establish the relations between catalyst compositions and the structure of SWCNTs. Here, we present a high-throughput strategy to investigate the statistical patterns in catalyst activity and selective growth of SWCNTs using Co/Pt/Mo ternary catalysts. Statistical analysis reveals that in the Co/Pt/Mo ternary diagram, there is an active region in the Co-rich Co–Mo corner to grow SWCNTs with high yield (≥25 tubes/μm2) and high quality (I G / I D ≥ 40). Enriched semiconducting (s-) SWCNTs with a purity higher than 90% were obtained along the boundary of the high yield region, near the Co–Pt axis. The statistical patterns of the yield, quality and selectivity are associated with the alloy composition, revealing a negative correlation between the yield and enrichment of s-SWCNTs. High-resolution transmission electron microscope characterization shows that a Co–Pt alloy catalyst with a uniform size distribution facilitates the s-SWCNT enrichment. And the separate phases of a Co–Mo/Co catalyst stabilize the active Co phase, leading to long catalyst lifetime and high yield of SWCNTs. A high-throughput strategy is developed to investigate the statistical patterns of the catalyst activity and the selective growth of single-wall carbon nanotubes (SWCNTs) grown from Co/Pt/Mo ternary catalysts. The structure of Co/Pt and Co/Mo catalysts linked with SWCNTs are further identified by using high-resolution transmission electron microscope. [Display omitted] [ABSTRACT FROM AUTHOR]

High-purity (∼96%) isolated s-SWCNT film with narrow diameter distribution were prepared on large scale by oxygen-assisted FCCVD method. [Display omitted] • Bulk isolated s-SWCNT films with a high content of 96% were selectively prepared. • O 2 was found to play function on catalyst particle size and s-SWCNT diameter. • FET devices show good performance verifying the enrichment of s-SWCNTs. Semiconducting single-wall carbon nanotubes (s-SWCNTs) are promising for use in flexible electronics as a channel material. However, it remains a big challenge to directly grow high purity, high-quality s-SWCNTs in large scale. Here we report the synthesis of isolated s-SWCNTs by an oxygen-assisted floating catalyst chemical vapor deposition method. By controlling the density of nucleated SWCNTs, isolated or small-bundled, rather than large-bundled SWCNTs were generated in a floating state, so that the oxygen introduced could more efficiently selectively etch the metallic-SWCNTs formed. In addition, it was found that the oxygen also functions in limiting the size of Fe catalyst nanoparticles in a narrow range of 5–8 nm. As a result, isolated s-SWCNTs with a narrow diameter distribution were synthesized. The content of s-SWCNTs reached ∼96%, and the percentage of isolated tubes was estimated to be ∼83%. Thin-film transistors (TFTs) constructed using the s-SWCNT film showed high on/off ratios ranging from 2.1 × 104 to 1.2 × 106, verifying the effective enrichment of s-SWCNTs. [ABSTRACT FROM AUTHOR]

Abstract: The high-quality phosphorus-doped ZnO nanocombs were synthesized by the simple chemical vapor deposition method without use of any catalyst. The images of field-emission scanning electron microscopy show that the phosphorus-doped ZnO nanocombs have a uniform length of 8μm with the diameter of 70nm and the cusp of the teeth of 20nm. The measurement results of selected-area electron diffraction pattern indicate that the phosphorus-doped ZnO nanocombs are single crystalline structure. The phosphorus related acceptor emission was observed in the photoluminescence spectra of phosphorus-doped ZnO nanocombs at 11K. The acceptor binding energy is estimated to be ∼127meV. [Copyright &y& Elsevier]