Automated Computer Vision-Enabled Manufacturing of Nanowire Devices.

We present a high-throughput method for identifying and characterizing individual nanowires and for automatically designing electrode patterns with high alignment accuracy. Central to our method is an optimized machine-readable, lithographically processable, and multi-scale fiducial marker system─dubbed LithoTag─which provides nanostructure position determination at the nanometer scale. A grid of uniquely defined LithoTag markers patterned across a substrate enables image alignment and mapping in 100% of a set of >9000 scanning electron microscopy (SEM) images (>7 gigapixels). Combining this automated SEM imaging with a computer vision algorithm yields location and property data for individual nanowires. Starting with a random arrangement of individual InAs nanowires with diameters of 30 ± 5 nm on a single chip, we automatically design and fabricate >200 single-nanowire devices. For >75% of devices, the positioning accuracy of the fabricated electrodes is within 2 pixels of the original microscopy image resolution. The presented LithoTag method enables automation of nanodevice processing and is agnostic to microscopy modality and nanostructure type. Such high-throughput experimental methodology coupled with data-extensive science can help overcome the characterization bottleneck and improve the yield of nanodevice fabrication, driving the development and applications of nanostructured materials

Kinetic Control of Catalytic CVD for High-Quality Graphene at Low Temperatures

Low-temperature (∼600 °C), scalable chemical vapor deposition of high-quality, uniform monolayer graphene is demonstrated with a mapped Raman 2D/G ratio of >3.2, D/G ratio ≤0.08, and carrier mobilities of ≥3000 cm² V^–1 s^–1 on SiO₂ support. A kinetic growth model for graphene CVD based on flux balances is established, which is well supported by a systematic study of Ni-based polycrystalline catalysts. A finite carbon solubility of the catalyst is thereby a key advantage, as it allows the catalyst bulk to act as a mediating carbon sink while optimized graphene growth occurs by only locally saturating the catalyst surface with carbon. This also enables a route to the controlled formation of Bernal stacked bi- and few-layered graphene. The model is relevant to all catalyst materials and can readily serve as a general process rationale for optimized graphene CVD

Diffusion- and Reaction-Limited Growth of Carbon Nanotube Forests

We present a systematic study of the temperature and pressure dependence of the growth rate of vertically aligned small diameter (single- and few-walled) carbon nanotube forests grown by thermal chemical vapor deposition over the temperature range 560−800 °C and 10−5 to 14 mbar partial pressure range, using acetylene as the feedstock and Al2O3-supported Fe nanoparticles as the catalyst. We observe a pressure dependence of P0.6 and activation energies of <1 eV. We interpret this as a growth rate limited by carbon diffusion in the catalyst, preceded by a pre-equilibrium of acetylene dissociation on the catalyst surface. The carbon nanotube forest growth was recorded by high-resolution real-time optical imaging

Dynamic Catalyst Restructuring during Carbon Nanotube Growth

We study the restructuring of solid nickel catalyst nanoparticles during carbon nanotube growth by environmental transmission electron microscopy and multiscale modeling. Our molecular dynamics/continuum transport calculations of surface-diffusion-mediated restructuring are in quantitative agreement with the experimentally observed catalyst shape evolutions. The restructuring time scale is determined by reduced Ni diffusion through the stepped Ni−C interface region where the catalyst surface strongly anchors to the growing nanotube

Dynamic Catalyst Restructuring during Carbon Nanotube Growth

We study the restructuring of solid nickel catalyst nanoparticles during carbon nanotube growth by environmental transmission electron microscopy and multiscale modeling. Our molecular dynamics/continuum transport calculations of surface-diffusion-mediated restructuring are in quantitative agreement with the experimentally observed catalyst shape evolutions. The restructuring time scale is determined by reduced Ni diffusion through the stepped Ni−C interface region where the catalyst surface strongly anchors to the growing nanotube

Dynamic Catalyst Restructuring during Carbon Nanotube Growth

We study the restructuring of solid nickel catalyst nanoparticles during carbon nanotube growth by environmental transmission electron microscopy and multiscale modeling. Our molecular dynamics/continuum transport calculations of surface-diffusion-mediated restructuring are in quantitative agreement with the experimentally observed catalyst shape evolutions. The restructuring time scale is determined by reduced Ni diffusion through the stepped Ni−C interface region where the catalyst surface strongly anchors to the growing nanotube

Dynamic Catalyst Restructuring during Carbon Nanotube Growth

We study the restructuring of solid nickel catalyst nanoparticles during carbon nanotube growth by environmental transmission electron microscopy and multiscale modeling. Our molecular dynamics/continuum transport calculations of surface-diffusion-mediated restructuring are in quantitative agreement with the experimentally observed catalyst shape evolutions. The restructuring time scale is determined by reduced Ni diffusion through the stepped Ni−C interface region where the catalyst surface strongly anchors to the growing nanotube

Diffusion- and Reaction-Limited Growth of Carbon Nanotube Forests

We present a systematic study of the temperature and pressure dependence of the growth rate of vertically aligned small diameter (single- and few-walled) carbon nanotube forests grown by thermal chemical vapor deposition over the temperature range 560−800 °C and 10−5 to 14 mbar partial pressure range, using acetylene as the feedstock and Al2O3-supported Fe nanoparticles as the catalyst. We observe a pressure dependence of P0.6 and activation energies of <1 eV. We interpret this as a growth rate limited by carbon diffusion in the catalyst, preceded by a pre-equilibrium of acetylene dissociation on the catalyst surface. The carbon nanotube forest growth was recorded by high-resolution real-time optical imaging

Dynamic Catalyst Restructuring during Carbon Nanotube Growth

We study the restructuring of solid nickel catalyst nanoparticles during carbon nanotube growth by environmental transmission electron microscopy and multiscale modeling. Our molecular dynamics/continuum transport calculations of surface-diffusion-mediated restructuring are in quantitative agreement with the experimentally observed catalyst shape evolutions. The restructuring time scale is determined by reduced Ni diffusion through the stepped Ni−C interface region where the catalyst surface strongly anchors to the growing nanotube

Dynamic Catalyst Restructuring during Carbon Nanotube Growth

We study the restructuring of solid nickel catalyst nanoparticles during carbon nanotube growth by environmental transmission electron microscopy and multiscale modeling. Our molecular dynamics/continuum transport calculations of surface-diffusion-mediated restructuring are in quantitative agreement with the experimentally observed catalyst shape evolutions. The restructuring time scale is determined by reduced Ni diffusion through the stepped Ni−C interface region where the catalyst surface strongly anchors to the growing nanotube