Supplementary document for A dual layer chessboard metasurface sandwiched by a spin-on-carbon for spectral modulation - 6822671.pdf

The refractive index of spin-on-carbo

An Environmental Transmission Electron Microscopy Study of the Stability of the TiO₂ (1 × 4) Reconstructed (001) Surface

The anatase TiO2 nanocrystals with dominant (001) facets attracted tremendous attention in the past decade. However, the reported intrinsic property of the (001) surface is still a cause of controversy. A crucial reason is that the (001) surface usually undergoes a (1 × 4) reconstruction, which may result in a remarkable difference in property. Herein, we performed an in situ environmental transmission electron microscopy (ETEM) study regarding the formation and stability of the (1 × 4)-(001) surface of TiO2 nanocrystals. The systematic ETEM studies confirmed that the (1 × 4)-(001) surface could be generated at elevated temperature (above 300 °C) when the surface contaminants were removed and the formed reconstruction could survive under different conditions, which indicate the surface reconstruction should be taken into account in related property research. In addition, an oriented layer-by-layer beam damage process on the (001) surface is confirmed, and optimal imaging conditions were also investigated, which would help to identify the intrinsic structure of the TiO2(001) surface

Real-Time Observation of Reconstruction Dynamics on TiO₂(001) Surface under Oxygen via an Environmental Transmission Electron Microscope

The surface atomic structure has a remarkable impact on the physical and chemical properties of metal oxides and has been studied extensively by scanning tunneling microscopy. However, acquiring real-time information on the formation and evolution of the surface structure remains a great challenge. Here we use environmental transmission electron microscopy to directly observe the stress-induced reconstruction dynamics on the (001) surface of anatase TiO₂. Our in situ results unravel for the first time how the (1 × 4) reconstruction forms and how the metastable (1 × 3) and (1 × 5) patterns transform into the (1 × 4) surface stable structure. With the support of first-principles calculations, we find that the surface evolution is driven by both low coordinated atoms and surface stress. This work provides a complete picture of the structural evolution of TiO₂(001) under oxygen atmosphere and paves the way for future studies of the reconstruction dynamics of other solid surfaces

Real-Time Observation of Reconstruction Dynamics on TiO₂(001) Surface under Oxygen via an Environmental Transmission Electron Microscope

The surface atomic structure has a remarkable impact on the physical and chemical properties of metal oxides and has been studied extensively by scanning tunneling microscopy. However, acquiring real-time information on the formation and evolution of the surface structure remains a great challenge. Here we use environmental transmission electron microscopy to directly observe the stress-induced reconstruction dynamics on the (001) surface of anatase TiO₂. Our in situ results unravel for the first time how the (1 × 4) reconstruction forms and how the metastable (1 × 3) and (1 × 5) patterns transform into the (1 × 4) surface stable structure. With the support of first-principles calculations, we find that the surface evolution is driven by both low coordinated atoms and surface stress. This work provides a complete picture of the structural evolution of TiO₂(001) under oxygen atmosphere and paves the way for future studies of the reconstruction dynamics of other solid surfaces

Atomic-Scale Observation of Vapor–Solid Nanowire Growth <i>via</i> Oscillatory Mass Transport

<i>In situ</i> atomic-scale transmission electron microscopy (TEM) can provide critical information regarding growth dynamics and kinetics of nanowires. A catalyst-aided nanowire growth mechanism has been well-demonstrated by this method. By contrast, the growth mechanism of nanowires without catalyst remains elusive because of a lack of crucial information on related growth dynamics at the atomic level. Herein, we present a real-time atomic-scale observation of the growth of tungsten oxide nanowires through an environmental TEM. Our results unambiguously demonstrate that the vapor–solid mechanism dominates the nanowire growth, and the oscillatory mass transport on the nanowire tip maintains the noncatalytic growth. Autocorrelation analysis indicates that adjacent nucleation events in the nanowire growth are independent of each other. These findings may improve the understanding of the vapor–solid growth mechanism of nanowires

In Situ STEM Determination of the Atomic Structure and Reconstruction Mechanism of the TiO₂ (001) (1 × 4) Surface

The widely studied anatase TiO₂ (001) surface usually shows a (1 × 4) reconstruction, which may directly influence its physical and chemical properties. Although various atomic models are proposed, the debates regarding the models and the formation mechanism of such reconstruction remain until now due to the lack of direct experimental evidence at the atomic level. Herein, we report the atomic-scale determination of the atomic structure and the reconstruction mechanism of the TiO₂ (001) (1 × 4) surface by in situ spherical aberration corrected scanning transmission electron microscopy (STEM) at elevated temperature. The atomic features of the reconstructed surface are unambiguously identified in our experiments, providing a solid evidence to verify the ad-molecule model, which was predicted by the calculations 15 years ago. Furthermore, the mysterious reconstruction route is revealed by our real time STEM images, which involves a new metaphase of the (001) surface. These results are expected to help resolve current dispute concerning the reconstruction models and understand the true performances of the anatase TiO₂ (001) surface

Real-Time Observation of Reconstruction Dynamics on TiO₂(001) Surface under Oxygen via an Environmental Transmission Electron Microscope

The surface atomic structure has a remarkable impact on the physical and chemical properties of metal oxides and has been studied extensively by scanning tunneling microscopy. However, acquiring real-time information on the formation and evolution of the surface structure remains a great challenge. Here we use environmental transmission electron microscopy to directly observe the stress-induced reconstruction dynamics on the (001) surface of anatase TiO₂. Our in situ results unravel for the first time how the (1 × 4) reconstruction forms and how the metastable (1 × 3) and (1 × 5) patterns transform into the (1 × 4) surface stable structure. With the support of first-principles calculations, we find that the surface evolution is driven by both low coordinated atoms and surface stress. This work provides a complete picture of the structural evolution of TiO₂(001) under oxygen atmosphere and paves the way for future studies of the reconstruction dynamics of other solid surfaces

Real-Time Observation of Reconstruction Dynamics on TiO₂(001) Surface under Oxygen via an Environmental Transmission Electron Microscope

The surface atomic structure has a remarkable impact on the physical and chemical properties of metal oxides and has been studied extensively by scanning tunneling microscopy. However, acquiring real-time information on the formation and evolution of the surface structure remains a great challenge. Here we use environmental transmission electron microscopy to directly observe the stress-induced reconstruction dynamics on the (001) surface of anatase TiO₂. Our in situ results unravel for the first time how the (1 × 4) reconstruction forms and how the metastable (1 × 3) and (1 × 5) patterns transform into the (1 × 4) surface stable structure. With the support of first-principles calculations, we find that the surface evolution is driven by both low coordinated atoms and surface stress. This work provides a complete picture of the structural evolution of TiO₂(001) under oxygen atmosphere and paves the way for future studies of the reconstruction dynamics of other solid surfaces

Orientational Electrodeposition of Highly (002)-Textured Zinc Metal Anodes Enabled by Iodide Ions for Stable Aqueous Zinc Batteries

Regulating the crystallographic texture of the zinc (Zn) metal anode is promising to promote Zn reversibility in aqueous electrolytes, but the direct fabrication of specific textured Zn still remains challenging. Herein, we report a facile iodide ion (I–)-assisted electrodeposition strategy that can scalably fabricate highly (002) crystal plane-textured Zn metal anode (H-(002)-Zn). Theoretical and experimental characterizations demonstrate that the presence of I– additives can significantly elevate the growth rate of the Zn (100) plane, homogenize the Zn nucleation, and promote the plating kinetics, thus enabling the uniform H-(002)-Zn electrodeposition. Taking the electrolytic cell with the conventional ZnSO4-based electrolyte and commercial Cu substrate as a model system, the Zn texture gradually transforms from (101) to (002) as the increase of NaI additive concentration. In the optimized 1 M ZnSO4 + 0.8 M NaI electrolyte, the as-prepared H-(002)-Zn features a compact structure and an ultrahigh intensity ratio of (002) to (101) signal without containing the (100) signal. The free-standing H-(002)-Zn electrode manifests stronger resistance to interfacial side reactions than the conventional (101)-textured Zn electrode, thus delivering a high efficiency of 99.88% over 400 cycles and ultralong cycling lifespan over 6700 h (>9 months at 1 mA cm–2) and assuring the stable operation of full Zn batteries. This work will enlighten the efficient electrosynthesis of high-performance Zn anodes for practical aqueous Zn batteries

Early Stage Growth of Rutile Titania Mesocrystals

Exploring the crystallization process of metal oxide mesocrystals has attracted enormous attention recently. However, due to the lack of insight into the behaviors of short-lived species at initial growth stages, there is currently a gap in understanding the underlying growth mechanism. Here, a combination of a preseeded hydrothermal method and transmission electron microscopy allows us to witness the rapid crystallization by particle attachement (CPA) in the early growth stage of capsule-shaped rutile titania mesocrystals. The presence of the embryonic form of nanocapsules, the slight misalignment of the primary particles, and, most importantly, the atomic interface between primary particles during attachment strongly indicate the existence of CPA mechanism. Furthermore, we rationalize our findings in terms of the free energy landscapes that govern nonclassical formation pathways. Our study provides a practical approach to explore the formation mechanism of fast-growing crystals at their initial growth stages