Electron-beam induced synthesis of nanostructures: a review

As the success of nanostructures grows in modern society so does the importance of our ability to control their synthesis in precise manners, often with atomic precision as this can directly affect the final properties of the nanostructures. Hence it is crucial to have both deep insight, ideally with real-time temporal resolution, and precise control during the fabrication of nanomaterials. Transmission electron microscopy offers these attributes potentially providing atomic resolution with near real time temporal resolution. In addition, one can fabricate nanostructures in situ in a TEM. This can be achieved with the use of environmental electron microscopes and/or specialized specimen holders. A rather simpler and rapidly growing approach is to take advantage of the imaging electron beam as a tool for in situ reactions. This is possible because there is a wealth of electron specimen interactions, which, when implemented under controlled conditions, enable different approaches to fabricate nanostructures. Moreover, when using the electron beam to drive reactions no specialized specimen holders or peripheral equipment is required. This review is dedicated to explore the body of work available on electron-beam induced synthesis techniques with in situ capabilities. Particular emphasis is placed on the electron beam-induced synthesis of nanostructures conducted inside a TEM, viz. the e-beam is the sole (or primary) agent triggering and driving the synthesis process

Synthesis of carbon nanotubes with and without catalyst particles

The initial development of carbon nanotube synthesis revolved heavily around the use of 3d valence transition metals such as Fe, Ni, and Co. More recently, noble metals (e.g. Au) and poor metals (e.g. In, Pb) have been shown to also yield carbon nanotubes. In addition, various ceramics and semiconductors can serve as catalytic particles suitable for tube formation and in some cases hybrid metal/metal oxide systems are possible. All-carbon systems for carbon nanotube growth without any catalytic particles have also been demonstrated. These different growth systems are briefly examined in this article and serve to highlight the breadth of avenues available for carbon nanotube synthesis

Reversible electron charge transfer in single-wall carbon nanotubes

Single-wall carbon nanotubes (SWCNT) have proved to be very special materials due to their unique electronic properties. Over the last years many scientists have dedicated their research to the study of the these materials as an electronic system. Amphoteric doping effects (n-type and p-type), which can be reversed, became a very popular way of manipulating the optic and electronic properties of carbon nanotubes. In the particular case of SWCNT, the most common and widely used procedure, which changes their properties, is acid treatment applied as a purification procedure. The effect of the addition of this kind of the dopant has been widely studied but not fully understood so far. Here, we present a study, of two kinds of SWCNT, produced within different techniques: (i) chemical vapors deposition and (ii) laser ablation. The main difference between the two types is the diameter distribution of the obtained materials, which is broad in the first technique and narrow in the second. After the acid treatment it is possible to observe a diameter sensitive doping effect on both samples. Resonance Raman spectroscopy, optical absorption spectroscopy (OAS) in UV/Vis/NIR and the Fourier transform middle-infrared (FTIR) spectroscopy have been applied for the characterization of the samples

Reversible electron charge transfer in single-wall carbon nanotubes

Single-wall carbon nanotubes (SWCNT) have proved to be very special materials due to their unique electronic properties. Over the last years many scientists have dedicated their research to the study of the these materials as an electronic system. Amphoteric doping effects (n-type and p-type), which can be reversed, became a very popular way of manipulating the optic and electronic properties of carbon nanotubes. In the particular case of SWCNT, the most common and widely used procedure, which changes their properties, is acid treatment applied as a purification procedure. The effect of the addition of this kind of the dopant has been widely studied but not fully understood so far. Here, we present a study, of two kinds of SWCNT, produced within different techniques: (i) chemical vapors deposition and (ii) laser ablation. The main difference between the two types is the diameter distribution of the obtained materials, which is broad in the first technique and narrow in the second. After the acid treatment it is possible to observe a diameter sensitive doping effect on both samples. Resonance Raman spectroscopy, optical absorption spectroscopy (OAS) in UV/Vis/NIR and the Fourier transform middle-infrared (FTIR) spectroscopy have been applied for the characterization of the samples

Atomic resolution imaging and topography of boron nitride sheets produced by chemical exfoliation

Here, we present a simple method for preparing thin few-layer sheets of hexagonal BN with micrometer-sized dimensions using chemical exfoliation in the solvent 1,2-dichloroethane. The atomic structure of both few-layer and monolayer BN sheets is directly imaged using aberration-corrected high-resolution transmission electron microscopy. Electron beam induced sputtering effects are examined in real time. The removal of layers of BN by electron beam irradiation leads to the exposure of a step edge between a monolayer and bilayer region. We use HRTEM imaging combined with image simulations to show that BN bilayers can have AB stacking and are not limited to just AA stacking. © 2010 American Chemical Society

Graphene

Providing fundamental knowledge necessary to understand graphene's atomic structure, band-structure, unique properties and an overview of groundbreaking current and emergent applications, this new handbook is essential reading for materials scientists, chemists and physicists. Since the 2010 physics Nobel Prize awarded to Geim and Novosolev for their groundbreaking work isolating graphene from bulk graphite, there has been a huge surge in interest in the area. This has led to a large number of news books on graphene. However, for such a vast inflow of new entrants, the current literature is surprisingly slight, focusing exclusively on current research or books on previous "hot topic" allotropes of carbon. This book covers fundamental groundwork of the structure, property, characterization methods and applications of graphene, along with providing the necessary knowledge of graphene's atomic structure, how it relates to its band-structure and how this in turn leads to the amazing properties of graphene. And so it provides new graduate students and post-docs with a resource that equips them with the knowledge to undertake their research. Discusses graphene's fundamental structure and properties, acting as a time-saving handbook for validated research Demonstrates 100+ high-quality graphical representations, providing the reader with clear images to convey complex situations Reviews characterization techniques relevant to grapheme, equipping the reader with experimental knowledge relevant for practical use rather than just theoretical understanding. © 2013 Elsevier Inc. All rights reserved

Graphene

Providing fundamental knowledge necessary to understand graphene's atomic structure, band-structure, unique properties and an overview of groundbreaking current and emergent applications, this new handbook is essential reading for materials scientists, chemists and physicists. Since the 2010 physics Nobel Prize awarded to Geim and Novosolev for their groundbreaking work isolating graphene from bulk graphite, there has been a huge surge in interest in the area. This has led to a large number of news books on graphene. However, for such a vast inflow of new entrants, the current literature is surprisingly slight, focusing exclusively on current research or books on previous "hot topic" allotropes of carbon. This book covers fundamental groundwork of the structure, property, characterization methods and applications of graphene, along with providing the necessary knowledge of graphene's atomic structure, how it relates to its band-structure and how this in turn leads to the amazing properties of graphene. And so it provides new graduate students and post-docs with a resource that equips them with the knowledge to undertake their research. Discusses graphene's fundamental structure and properties, acting as a time-saving handbook for validated research Demonstrates 100+ high-quality graphical representations, providing the reader with clear images to convey complex situations Reviews characterization techniques relevant to grapheme, equipping the reader with experimental knowledge relevant for practical use rather than just theoretical understanding. © 2013 Elsevier Inc. All rights reserved

Structural transformations of carbon chains inside nanotubes

In situ aberration-corrected high-resolution transmission electron microscopy is used to examine the structural transformations of carbon chains that occur in the interior region of carbon nanotubes. We find electron-beam irradiation leads to the formation of two-dimensional carbon structures that are freely mobile inside the nanotube. The inner diameter of the nanotube influences the structural transformations of the carbon chains. As the diameter of the nanotube increases, electron-beam irradiation leads to curling of the chains and eventually the formation of closed looped structures. The closed looped structures evolve into spherical fullerenelike structures that exhibit translational motion inside the nanotubes and also coalesce to form larger nanotube structures. These results demonstrate the use of carbon nanotubes as test tubes for growing small carbon nanotubes within the interior by using only electron-beam irradiation at 80 kV. © 2010 The American Physical Society

Examining the stability of folded graphene edges against electron beam induced sputtering with atomic resolution

Low energy electron beam irradiation of the edges of graphene can lead to rearrangement of the carbon atomic structure. We demonstrate the ability to distinguish intrinsic edges of graphene from edges formed by back folding based upon atomic structure and their susceptibility to sputtering. We examine how the atomic structure of the edges of graphene and few layer graphene sheets influences their stability under electron beam irradiation at a low electron accelerating voltage of 80 kV using aberration-corrected high-resolution transmission electron microscopy. We demonstrate that edges of few layer graphene produced by back folding are extremely robust against electron beam induced sputtering as compared to intrinsic edges that are naturally formed. The stability of the folded edges in few layer graphene is shown to increase with increasing number of layers. The higher stability of fold edges is related to the absence of any unsaturated carbon atoms that can be sputtered by electron beam irradiation. © 2010 IOP Publishing Ltd

Examining co-based nanocrystals on graphene using low-voltage aberration-corrected transmission electron microscopy.

We present a method to produce graphene and few layer graphene sheets using solution phase chemistry, which are used as ultrathin support membranes for enhanced imaging of nanomaterials using transmission electron microscopy. We demonstrate this by decorating the surface of the graphene sheets with Co-based nanocrystals (CoCl(2) and hcp Co). Low-voltage aberration-corrected high resolution transmission electron microscopy at 80 kV is used to image the nanocrystals on the thin graphene supports. We show that electron beam irradiation causes the CoCl(2) nanocrystals to become mobile on the graphene surface and exhibit both rotational and translational motion. We provide real-time in situ monitoring with atomic resolution of the coalescence of two CoCl(2) nanocrystals on the graphene surface, driven by electron beam irradiation. The CoCl(2) nanocrystals are then annealed in vacuum and transform into Co nanocrystals with hcp crystal structure. We show that these Co nanocrystals are catalytic and electron beam irradiation leads to the etching of the graphene surface, not observed for the CoCl(2) nanocrystals