Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMolecular Beam Epitaxy Growth of Scandium Nitride on Hexagonal SiC, GaN, and AlN
114
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
RF plasma assisted MBE growth of Scandium Nitride (ScN) thin films on GaN (0001)/SiC, AlN (0001)/Al2O3 and on 6H-SiC (0001) hexagonal substrates is found to lead to a face centered cubic (rock-salt) crystal structure with (111) out-of-plane orientation instead of hexagonal orientation. For the first time, cubic (111) twinned patterns in ScN are observed by in-situ electron diffraction during epitaxy, and the twin domains in ScN are detected by electron backscattered diffraction, and further corroborated with X-ray diffraction. The epitaxial ScN films display very smooth, sub nanometer surface roughness at a growth temperature of 750C. Temperature-dependent Hall-effect measurements indicate a constant high n-type carrier concentration of ~1x1020/cm3 and electron mobilities of ~ 20 cm2/Vs.
rate research
Read More
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, $sim1times10^{-8}$ 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 $[11bar20]$ axis of hBN parallel to the $[1bar100]$ axis of the sapphire substrate. Unlike the rough, polycrystalline films previously reported, atomic force microscopy (AFM) and transmission electron microscopy (TEM) characterization of these films demonstrate smooth, layered, few-nanometer hBN films on a nitridated sapphire substrate. This demonstration of high-quality hBN growth by MBE is a step towards its integration into existing epitaxial growth platforms, applications, and technologies.
Hexagonal boron nitride (h-BN) is a layered two-dimensional material with properties that make it promising as a dielectric in various applications. We report the growth of h-BN films on Ni foils from elemental B and N using molecular beam epitaxy. The presence of crystalline h-BN over the entire substrate is confirmed by Raman spectroscopy. Atomic force microscopy is used to examine the morphology and continuity of the synthesized films. A scanning electron microscopy study of films obtained using shorter depositions offers insight into the nucleation and growth behavior of h-BN on the Ni substrate. The morphology of h-BN was found to evolve from dendritic, star-shaped islands to larger, smooth triangular ones with increasing growth temperature.
Recently theorized hybrid II-IV-N{_2} / III-N heterostructures, based on current commercialized (In,Ga)N devices, are predicted to significantly advance the design space of highly efficient optoelectronics in the visible spectrum, yet there are few epitaxial studies of II-IV-N{_2} materials. In this work, we present heteroepitaxial ZnGeN{_2} grown on GaN buffers and AlN templates. We demonstrate that a GaN nucleating surface is crucial for increasing the ZnGeN{_2} crystallization rate to combat Zn desorption, extending the stoichiometric growth window from 215 {degree}C on AlN to 500 {degree}C on GaN buffers. Structural characterization reveals well crystallized films with threading dislocations extending from the GaN buffer. These films have a critical thickness for relaxation of 20 nm - 25 nm as determined by reflection high energy electron diffraction (RHEED) and cross-sectional scanning electron microscopy (SEM). The films exhibit a cation-disordered wurtzite structure, with lattice constants a = 3.216 {AA} {pm} 0.004 {AA} and c = 5.215 {AA} {pm} 0.005 {AA} determined by RHEED and X-ray diffraction (XRD). This work demonstrates a significant step towards the development of hybrid ZnGeN{_2}-GaN integrated devices.
The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h-BN) flakes is demonstrated. Formation of single-layer graphene is clearly apparent in Raman spectra which display sharp optical phonon bands. Atomic-force microscope images and Raman maps reveal that the graphene grown depends on the surface morphology of the h-BN substrates. The growth is governed by the high mobility of the carbon atoms on the h-BN surface, in a manner that is consistent with van der Waals epitaxy. The successful growth of graphene layers depends on the substrate temperature, but is independent of the incident flux of carbon atoms.
The effects of mobility of small islands on island growth in molecular beam epitaxy are studied. It is shown that small island mobility affects both the scaling and morphology of islands during growth. Three microscopic models are considered, in which the critical island sizes are $i^*=1,2$ and 3 (such that islands of size $s le i^*$ are mobile while islands of size $s ge i^{ast}+1$ are immobile). As i^* increases, islands become more compact, while the exponent $gamma$ which relates the island density to deposition rate increases. The morphological changes are quantified by using fractal analysis. It is shown that the fractal dimensions are rather insensitive to changes in i^*. However, the prefactors provide a quantitative measure of the changing morphologies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
