Monolayer molybdenum disulphide (MoS2) is a promising two-dimensional direct-bandgap semiconductor with potential applications in atomically thin and flexible electronics. An attractive insulating substrate or mate for MoS2 (and related materials such as graphene) is hexagonal boron nitride (h-BN). Stacked heterostructures of MoS2 and h-BN have been produced by manual transfer methods, but a more efficient and scalable assembly method is needed. Here we demonstrate the direct growth of single- and few-layer MoS2 on h-BN by chemical vapor deposition (CVD) method, which is scalable with suitably structured substrates. The growth mechanisms for single-layer and few-layer samples are found to be distinct, and for single-layer samples low relative rotation angles (<5 degree) between the MoS2 and h-BN lattices prevail. Moreover, MoS2 directly grown on h-BN maintains its intrinsic 1.89 eV bandgap. Our CVD synthesis method presents an important advancement towards controllable and scalable MoS2 based electronic devices.
Boron nitride (BN) has been explored these days because of its extraordinary optical, chemical and mechanical properties. BN is sensitive to its crystal structure that slight change in lattice parameters enormously change its properties. Present study deals with synthesis, characterization as well as photocatalytic applications of BN-based composite. When boron nitride was mixed with SnO2 having tetragonal crystal structure, dissociation into smaller sheets occurred and the material oriented to (102) plane. SnO2 particles attached both sides of BN sheets provided high surface area which make t…
According to classical grain growth laws, grain growth is driven by the minimization of surface energy and will continue until a single grain prevails. These laws do not take into account the lattice anisotropy and the details of the microscopic rearrangement of mass between grains. Here we consider coarsening of body-centered cubic polycrystalline materials in three dimensions using the phase field crystal model. We observe as function of the quenching depth, a cross over between a state where grain rotation halts and the growth stagnates and a state where grains coarsen rapidly by coalescenc…
Grain growth in nanocrystalline Al was studied by means of molecular dynamics simulations. The novelty of this study results from the utilization of an algorithm to resolve per-grain kinetics and orientation change from molecular dynamics data sets. To this aim, a highly efficient algorithm for the identification and reconstruction of crystallites from molecular dynamics data sets of FCC materials was developed. This method is capable of calculating specific attributes of grains, namely, volume, center of mass, average orientation and orientation spread. In addition, it provides a mapping meth…
Atomically thin MoS2/graphene heterostructures are promising candidates for nanoelectronic and optoelectronic technologies. Among different graphene substrates, epitaxial graphene (EG) on SiC provides several potential advantages for such heterostructures including high electronic quality, tunable substrate coupling, wafer-scale processability, and crystalline ordering that can template commensurate growth. Exploiting these attributes, we demonstrate here the thickness-controlled van der Waals epitaxial growth of MoS2 on EG via chemical vapor deposition, giving rise to transfer-free synthesis …
We present results on the growth of CdTe-HgTe core-shell nanowires, a realization of a quasi one-dimensional heterostructure of the topological insulator HgTe. The growth is a two step process consisting of the growth of single crystalline zinc blende CdTe nanowires with the vapor-liquid-solid method and the overgrowth of these wires with HgTe such that a closed shell is formed around the CdTe core structure. The CdTe wire growth is monitored by RHEED allowing us to infer information on the crystal properties from the electron diffraction pattern. This information is used to find and control t…
The fabrication of ZnSe/ZnTe superlattices grown by the process of rotating the substrate in the presence of an inhomogeneous flux distribution instead of successively closing and opening of source shutters is studied via Monte Carlo simulations. It is found that the concentration of each compound is sinusoidally modulated along the growth direction, caused by the uneven arrival of Se and Te atoms at a given point of the sample, and by the variation of the Te/Se ratio at that point due to the rotation of the substrate. In this way we obtain a ZnSe$_{1-x}$Te$_x$ alloy in which the composition $…
We consider the grain growth and stagnation in polycrystalline microstructures. From the phase field crystal modelling of the coarsening dynamics, we identify a transition from a grain-growth stagnation upon deep quenching below the melting temperature $T_m$ to a continuous coarsening at shallower quenching near $T_m$. The grain evolution is mediated by local grain rotations. In the deep quenching regime, the grain assembly typically reaches a metastable state where the kinetic barrier for recrystallization across boundaries is too large and grain rotation with subsequent coalescence is infeas…
Hexagonal boron nitride (hBN) has been grown on sapphire substrates by ultra-high temperature molecular beam epitaxy (MBE). A wide range of substrate temperatures and boron fluxes have been explored, revealing that high crystalline quality hBN layers are grown at high substrate temperatures, $>$1600$^\circ$C, and low boron fluxes, $\sim1\times10^{-8}$ Torr beam equivalent pressure. \emph{In-situ} reflection high energy electron diffraction (RHEED) revealed the growth of hBN layers with $60^\circ$ rotational symmetry and the $[11\bar20]$ axis of hBN parallel to the $[1\bar100]$ axis of the sapp…
Based on first-principles calculations, we propose that a layered electride Mg2O can serve as an effective substrate, in place of metal substrate, to grow honeycomb borophene (h-borophene). We first confirm the thermodynamic stability of h-B@Mg2O heterostructure by energetics analysis and dynamic stability by absence of imaginary frequency in phonon spectra. Then, kinetically, we identify the atomistic pathways for a preferred 2D growth mode over 3D growth, and reveal a growth transition from 2D compact islands to h-borophene at ~13-atom cluster size, indicating the feasibility of epitaxial gr…
Single-phase Ni0.46Mn0.54As films with strained C1b symmetry have been successfully grown on GaAs (001) substrates by molecular-beam epitaxy. The epitaxial relationship between the film and the substrate has been studied using synchrotron radiation, and a preferred configuration of (110)-orientated Ni0.46Mn0.54As on (001)-orientated GaAs was revealed. In addition, the magnetic properties of the films were found to be significantly influenced by the growth temperature. The optimized growth temperature is determined to be ~370 degree Celsius , for which relatively high Curie temperature, large s…
In the synthesis of highly crystalline single-walled carbon nanotubes (SWCNTs), high growth temperatures are preferred, while the formation of impurity amorphous carbon (a-C) causes the termination of SWCNT growth and degrades its properties. To remove this by-product, H2O and CO2 have been employed in metal-catalyzed SWCNT growth systems because of their oxidizing ability. Recently, nonmetallic nanoparticles have become one of the growth seed candidates because of their high melting points and fewer metal impurities. In this study, by using nanodiamond-derived carbon nanoparticles as the soli…
Heterostructures of two-dimensional (2D) layered materials with selective compositions play an important role in creating novel functionalities. Effective interface coupling between 2D ferromagnet and electronic materials would enable the generation of exotic physical phenomena caused by intrinsic symmetry breaking and proximity effect at interfaces. Here, epitaxial growth of bilayer Bi(110) on 2D ferromagnetic Fe3GeTe2 (FGT) with large magnetic anisotropy has been reported. Bilayer Bi(110) islands are found to extend along fixed lattice directions of FGT. The six preferred orientations could …
An iterative algorithm based on Monte Carlo method is used to model thin film growth of AB type molecule and crystallization. Primarly, PVD technique is investigated since it is one of the most preferred on thin film growth processes. The formation of thin film has been simulated for a cubic region with 10000 A type and 10000 B type atoms. Up to third nearest neighboring cells have been taken into account to realize the inter-atomic interactions. Boltzmann statistics is used to deal temperature effect by treating both A and B atoms as classical particles. The proposed substrate with the same c…
In a combined experimental and theoretical study, we investigate the influence of the material source arrangement in a molecular beam epitaxy (MBE) system on the growth of nanowire (NW) core-shell structures. In particular, we study the shell growth of GaN around GaN template NWs under the boundary condition that Ga and N do not impinge on a given sidewall facet at the same time. Our experiments with different V/III ratios and substrate temperatures show that obtaining shells with homogeneous thickness along the whole NW length is not straightforward. Analyzing in detail the shell morphology w…
Quantum confinement was found to play a critical role in the formation of Au(111) islands grown on the surface of MoS2. These confinement effects are fully three dimensional, with a strong correlation to the relatively large Fermi wavelength associated with the Au(111) planes. The confinement effects result in preferred heights with a periodicity of nearly 2 nm and persist to much higher temperatures than are typically seen in electronic growth mode systems. These findings indicate the potential to explore electronic growth modes in a new class of systems based on metal - layered semiconductor…
The basic science responsible for the fascinating shapes of ice crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our Scanning Tunneling Spectroscopy (STS) data we provide compelling evidence that these fractals are 2D ice. They grow while they are in material contact with the atmosphere at 20 $^{\circ}$C and with…
