A fast synthesis route of boron-carbon-nitrogen ultrathin layers towards highly mixed ternary B-C-N phases

We report a direct and fast synthesis route to grow boron-carbon-nitrogen layers based on microwave-assisted plasma enhanced chemical vapour deposition (PECVD) by using methylamine borane as a single source molecular precursor. This easy and inexpensive method allows controlled and reproducible growth of B-C-N layers onto thin Cu foils. Their morphological, structural, chemical, optical and transport properties have been thoroughly characterized by a number of different microscopies, transport and spectroscopic techniques. Though disorder and segregation into C-rich and h-BN-rich domains have been observed in ultrathin flat few layers, high doping levels have been reached, inducing strong modifications of the electronic, optical and transport properties of C-rich and h-BN-rich phases. This synthesis procedure can open new routes towards the achievement of homogeneous highly mixed ternary B-C-N phase

A genetic modifier screen identifies chromosomal intervals harboring potential midline interacting genes

This work investigates the growth of B-C-N layers by chemical vapor deposition using methylamine borane (MeAB) as single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B-C-N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and Graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is significant presence of C-N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B-C-N layers is presented, discussed and compared with previous seminal works with samples of similar composition.Comment: 35 pages, 7 figure

Chemical vapor deposition growth of boron-carbon-nitrogen layers from methylamine borane thermolysis products

This is the Accepted Manuscript version of an article accepted for publication in Nanotechnology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6528/aa9c07This work investigates the growth of B-C-N layers by chemical vapor deposition using methylamine borane (MeAB) as the single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B-C-N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is a significant presence of C-N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B-C-N layers is presented, discussed and compared with previous seminal works with samples of similar compositio

Preparation and structural characterization of new alkoxo- and (alkoxo)(amido)(imido)-niobium(V) compounds. Crystal structure of [NbCl(μ-OMe)[N(SiMe3)2](NSiMe3)]2

The reactions of NbCl3 with Me3SiOMe in the appropriate molar ratios have given new alkoxoniobium(V) derivatives of the type NbCl5-x (OMe)x (x = 2 (I), 3 (II)). Reactions of I and II with various ligands afford the corresponding species NbCl5-x(OMe)xL, x = 2, L = OPPh3 (III); L = OAsPh3 (IV); L = THF (V); L = Cl- (VI); x = 3, L = OPPh3 (VII); L = Cl- (VIII). Similar hexacoordinate compounds NbCl3(OR)2(OPPh3), (R = Me (III), R = Et (IX), R = Pri (X)) have been obtained by reactions of NbCl5(OPPh3) with the relevant Me3SiOR compounds. Compounds I and II also react with {[LiN(SiMe3)2]Et2O}2 to give [NbCl(μ-OMe)[N(SiMe3)2](NSiMe3)]2 (XI) and [Nb(OMe)(μ-OMe)[N(SiMe3)2](NSiMe3)]2 (XII). All the compounds have been characterized by IR and NMR spectroscopy and the crystal structure of XI has been determined by X-ray diffraction. XI crystallizes in the monoclinic space group P21/c with a 10.236(1), b 9.789(1), c 21.201(3) Å, β 102.67(1)° and Dc 1.30 g cm-3 for Z = 4. A final R value of 0.042 (Rw = 0.052) based on 4272 reflections was obtained. The two metal atoms are asymmetrically bridged by the two methoxide ligands. Chloride, amido, and imido ligands complete the coordination spheres of both metal atoms. © 1988

A comparative study of the ZnO growth on graphene and graphene oxide: the role of the initial oxidation state of carbon

The role of the oxidation state of carbon on the early stages of growth of metal oxides was studied for the particular case of ZnO deposition on graphene and graphene oxide on SiO2 (G/SiO2 and GO/SiO2, respectively) substrates. The growth was carried out by thermal evaporation of metallic Zn under an oxygen atmosphere at room temperature. This technique permits quasi-equilibrium conditions during the oxide growth, allowing the characterization of the fundamental interaction between ZnO and the graphene-based substrates. Although in both cases ZnO follows a Volmer–Weber growth mode controlled by nucleation at defects, the details are different. In the case of the GO/SiO2 substrate, the nucleation process acts as a bottleneck, limiting the coverage of the complete surface and allowing the growth of very large ZnO structures in comparison to G/SiO2. Moreover, by studying the Zn-LMM Auger spectra, it is shown how the initial nature of the substrate influences the composition of the ZnO deposit during the very early stages of growth in terms of Zn/O atomic ratio. These results are compared to those previously reported regarding ZnO growth on graphite and graphene on Cu (G/Cu). This comparison allows us to understand the role of different characteristics of graphene-based substrates in terms of number of defects, oxidation state, graphene support substrate and number of graphene layers.This investigation has been funded by the MINECO of Spain through the FIS2015-67367-C2-1-P project and by the Comunidad de Madrid through the NANOMAGCOST-CM P2018/NMT4321 project. One of the authors (C.M.) thanks MCIU for a FPU grant.Peer reviewe

Electronic Decoupling of Graphene from Copper Induced by Deposition of ZnO: A Complex Substrate/Graphene/Deposit/Environment Interaction

This study presents experimental data of the interactions and reactions that occur during the early stages of the growth of ZnO on graphene supported on polycrystalline copper and the subsequent changes on the electronic properties of the graphene. The combination of substrate, graphene, and intercalated species (such as oxygen and water molecules) between graphene and copper due to air exposure, together to the evaporation of metallic zinc under oxygen atmosphere, induces the electronic decoupling of the graphene from copper by the formation of a nanometric layer of copper oxide. In particular, the final stage consists in the formation of a complex interface formed by ZnO/ZnO /Zn/G/CuO/Cu. The role of each actor is discussed in terms of a galvanic corrosion reaction of the metallic substrate where the graphene is the cathode and the initial deposition of metallic zinc accelerates the kinetics of this reaction, after which ZnO grows on the metallic zinc initially deposited. In this manner, the electronic properties of graphene can be engineered by the combination and interrelation of substrates, environment, and new-deposited materials, revealing a more complex and realistic picture for real fabrication processes. These results may help to improve the real applicability of graphene in mass production devices.This investigation was funded by the Ministerio de Economía y Competitividad of Spain through the FIS2015-67367-C2-1-P project and by the Comunidad de Madrid through the NANOMAGCOST-CM P2018/ NMT4321 project. One of the authors (C.M.) thanks Ministerio de Educación, Cultura y Deporte for a FPU grant. The authors also would like to thank SEGAINVEX (UAM) and SCAI (UMA) for technical suppor

N-state random switching based on quantum tunnelling

In this work, we show how the hysteretic behaviour of resonant tunnelling diodes (RTDs) can be exploited for new functionalities. In particular, the RTDs exhibit a stochastic 2-state switching mechanism that could be useful for random number generation and cryptographic applications. This behaviour can be scaled to N-bit switching, by connecting various RTDs in series. The InGaAs/AlAs RTDs used in our experiments display very sharp negative differential resistance (NDR) peaks at room temperature which show hysteresis cycles that, rather than having a fixed switching threshold, show a probability distribution about a central value. We propose to use this intrinsic uncertainty emerging from the quantum nature of the RTDs as a source of randomness. We show that a combination of two RTDs in series results in devices with three-state outputs and discuss the possibility of scaling to N-state devices by subsequent series connections of RTDs, which we demonstrate for the up to the 4-state case. In this work, we suggest using that the intrinsic uncertainty in the conduction paths of resonant tunnelling diodes can behave as a source of randomness that can be integrated into current electronics to produce on-chip true random number generators. The N-shaped I-V characteristic of RTDs results in a two-level random voltage output when driven with current pulse trains. Electrical characterisation and randomness testing of the devices was conducted in order to determine the validity of the true randomness assumption. Based on the results obtained for the single RTD case, we suggest the possibility of using multi-well devices to generate N-state random switching devices for their use in random number generation or multi-valued logic devices.</p

A fast synthesis route of boron–carbon–nitrogen ultrathin layers towards highly mixed ternary B–C–N phases

We report a direct and fast synthesis route to grow boron–carbon–nitrogen layers based on microwave-assisted plasma enhanced chemical vapour deposition (PECVD) by using methylamine borane as a single source molecular precursor. This easy and inexpensive method allows controlled and reproducible growth of B–C–N layers onto thin Cu foils. Their morphological, structural, chemical, optical and transport properties have been thoroughly characterized by a number of different microscopies, transport and spectroscopic techniques. Though disorder and segregation into C-rich and h-BN-rich domains have been observed in ultrathin flat few layers, high doping levels have been reached, inducing strong modifications of the electronic, optical and transport properties of C-rich and h-BN-rich phases. This synthesis procedure can open new routes towards the achievement of homogeneous highly mixed ternary B–C–N phases

Large-Area Heterostructures from Graphene and Encapsulated Colloidal Quantum Dots via the Langmuir–Blodgett Method

This work explores the assembly of large-area heterostructures comprised of a film of silica-encapsulated, semiconducting colloidal quantum dots, deposited via the Langmuir–Blodgett method, sandwiched between two graphene sheets. The luminescent, electrically insulating film served as a dielectric, with the top graphene sheet patterned into an electrode and successfully used as a top gate for an underlying graphene field-effect transistor. This heterostructure paves the way for developing novel hybrid optoelectronic devices through the integration of 2D and 0D materials