Hetero-junctions of boron nitride and carbon nanotubes: Synthesis and characterization

Hetero-junctions of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) are expected to have appealing new properties that are not available from pure BNNTs and CNTs. Theoretical studies indicate that BNNT/CNT junctions could be multifunctional and applicable as memory, spintronic, electronic, and photonics devices with tunable band structures. This will lead to energy and material efficient multifunctional devices that will be beneficial to the society. However, experimental realization of BNNT/CNT junctions was hindered by the absent of a common growth technique for BNNTs and CNTs. In fact, the synthesis of BNNTs was very challenging and may involve high temperatures (up to 3000 degree Celsius by laser ablation) and explosive chemicals. During the award period, we have successfully developed a simple chemical vapor deposition (CVD) technique to grow BNNTs at 1100-1200 degree Celsius without using dangerous chemicals. A series of common catalyst have then been identified for the synthesis of BNNTs and CNTs. Both of these breakthroughs have led to our preliminary success in growing two types of BNNT/CNT junctions and two additional new nanostructures: 1) branching BNNT/CNT junctions and 2) co-axial BNNT/CNT junctions, 3) quantum dots functionalized BNNTs (QDs-BNNTs), 4) BNNT/graphene junctions. We have started to understand their structural, compositional, and electronic properties. Latest results indicate that the branching BNNT/CNT junctions and QDs-BNNTs are functional as room-temperature tunneling devices. We have submitted the application of a renewal grant to continue the study of these new energy efficient materials. Finally, this project has also strengthened our collaborations with multiple Department of Energy\u27s Nanoscale Science Research Centers (NSRCs), including the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory, and the Center for Integrated Nanotechnologies (CINTs) at Sandia National Laboratories and Los Alamos National Laboratory. Results obtained during the current funding period have led to the publication of twelve peer reviewed articles, three review papers, two book and one encyclopedia chapters, and thirty eight conference/seminar presentation. One US provisional patent and one international patent have also been filed

Room temperature tunneling switches and methods of making and using the same

The tunneling channel of a field effect transistor comprising a plurality of tunneling elements contacting a channel substrate. Applying a source-drain voltage of greater than a turn-on voltage produces a source-drain current of greater than about 10 pA. Applying a source-drain voltage of less than a turn-on voltage produces a source-drain current of less than about 10 pA. The turn-on voltage at room temperature is between about 0.1V and about 40V.https://digitalcommons.mtu.edu/patents/1137/thumbnail.jp

Two-dimensional electronics and optoelectronics: Present and future

Since the successful isolation of graphene a little over a decade ago, a wide variety of two-dimensional (2D) layered materials have been studied. They cover a broad spectrum of electronic properties, including metals, semimetals, semiconductors, and insulators. Many of these 2D materials have demonstrated promising potential for electronic and optoelectronic applications

Two-dimensional electronics and optoelectronics

The discovery of monolayer graphene has led to a Nobel Prize in Physics in 2010. This has stimulated research on a wide variety of two-dimensional (2D) layered materials. The coupling of metallic graphene, semiconducting 2D transition metal dichalcogenides (TMDCs) and black phosphorus has attracted tremendous amount of interest in new electronic and optoelectronic applications. Together with other 2D materials such as the wide band gap boron nitride nanosheets (BNNSs), all these 2D materials have led towards an emerging field of van der Waal 2D heterostructures. This book is originally published in Electronics (MDPI) as a special issue of “Two-Dimensional Electronics and Optoelectronics”. The book consists of a total of eight papers, including two review articles, covering important topics of 2D materials. These papers represent some of the important topics on 2D materials and devices. Promises and challenges of 2D materials are discussed herein, which provide a great recent guidance for future research and development

Recent advances in electronic and optoelectronic Devices Based on Two-Dimensional Transition Metal Dichalcogenides

Two-dimensional transition metal dichalcogenides (2D TMDCs) offer several attractive features for use in next-generation electronic and optoelectronic devices. Device applications of TMDCs have gained much research interest, and significant advancement has been recorded. In this review, the overall research advancement in electronic and optoelectronic devices based on TMDCs are summarized and discussed. In particular, we focus on evaluating field effect transistors (FETs), photovoltaic cells, light-emitting diodes (LEDs), photodetectors, lasers, and integrated circuits (ICs) using TMDCs

Two-Dimensional Electronics and Optoelectronics

The discovery of monolayer graphene led to a Nobel Prize in Physics being awarded in 2010. This has stimulated further research on a wide variety of two-dimensional (2D) layered materials. The coupling of metallic graphene, semiconducting 2D transition metal dichalcogenides (TMDCs) and black phosphorus have attracted a tremendous amount of interest in new electronic and optoelectronic applications. Together with other 2D materials, such as the wide band gap boron nitride nanosheets (BNNSs), all these 2D materials have led towards an emerging field of van der Waal 2D heterostructures. The papers in this book were originally published by Electronics (MDPI) in a Special Issue on “Two-Dimensional Electronics and Optoelectronics”. The book consists of eight papers, including two review articles, covering various pertinent and fascinating issues concerning 2D materials and devices. Further, the potential and the challenges of 2D materials are discussed, which provide up to date guidance for future research and development

Controlling dissociative adsorption for effective growth of carbon nanotubes

Dissociative adsorption has been widely simplified as part of the vapor–liquid–solid (VLS) growth model. We found that the addition of specific carrier gases can critically modify the growth rate and growth density of multiwall carbon nanotubes (MWNTs). These results were explained by dissociative adsorption of C2H2 molecules and a solid-core VLS growth model. Based on these integrated mechanisms, vertically aligned MWNTs were grown with an initial growth rate as high as ∼800μm∕h. This efficient growth process results at temperature and C2H2 partial pressures at which the decomposition and segregation rates of carbon are balanced. Appropriate use of carrier gas is one of the factors that could facilitate efficient and continuous growth of carbon nanotubes in the future

First-principles study of strain-induced modulation of energy gaps of graphene/BN and BN bilayers

First-principles calculations based on density functional theory are performed on graphene/BN and BN bilayers to investigate the effect of the strain on their energy gaps. For the graphene/BN bilayer, the bands have characteristic graphenelike features with a small band gap at K. Application of strain modulates the band gap, whose magnitude depends on the strength of interaction between constituent monolayers. For the BN bilayer, on the other hand, a large band gap is predicted, which remains nearly the same for small strains. The increased inhomogeneity in charge density of different carbon sublattices due to a stronger interplanar interaction is the cause of the predicted variation in the band gap with strains applied along the perpendicular direction in the graphene/BN bilayer

Strain-induced formation of carbon and boron clusters in boron carbide during dynamic indentation

The authors found that the level of amorphization or structural disorder in boron carbide is higher when induced by dynamic indentation compared to static indentation. Visible and uv Raman spectroscopies indicate that sp2-bonded aromatic carbon clusters were formed, consistent with the detected photoluminescence spectra. Infrared absorption shows that amorphous boron clusters were created by dynamic indentation which has strain rates ∼108 order higher than that introduced by static indentation. The decreased intensity of infrared stretching mode of carbon-boron-carbon (CBC) chains also suggests that amorphization is due to the collapse of B11C(CBC) unit cells, which reorganize into the energetically favorite carbon and boron clusters