Papers by Keyword: RHEED

Abstract: The in-situ monitoring of the MBE grown nanostructures can be carried out using the RHEED method. During the droplet epitaxal growth, the observation of the nanostructure formation is very important to understand the growth kinetics. In the present work, a novel in-situ RHEED evaluation and further MBE related developments are introduced, with which the quality of the nanostructure preparation can be improved.

Abstract: The technique of reflection high-energy electron diffraction (RHEED) has been applied to study the graphene growth on conductive and semi-insulating 6H-SiC (0001) substrates using two RHEED devices. It was found the oriented growth of graphene on the conductive wafer and both oriented as disordered graphene growth on semi-insulating wafer due to the partial formation of polycrystalline component in nanocarbon film. It was shown that the appearance of the graphene polycrystalline phase was caused by the lower perfection structure of the surface of the semi-insulating substrate as compared to the conductive substrate.

Abstract: The SiC surfaces were cleaned by the hydrogen plasma with ECRPEMOCVD plasma system at low temperature of 200°C, after the traditional wet cleaning. The surfaces were investigated by RHEED and X-ray Photoelectron Spectroscopy before and after hydrogen plasma treatment. The RHEED imagines showed that the SiC surfaces by hydrogen plasma treatment were more flatter than the SiC surfaces by the traditional wet cleaning, and we found the result that more treatment time, more flatter. The XPS spectra examinations indicated that the surface oxides reduced obviously and the C/C-H compounds on the SiC surface were removed by hydrogen plasma treatment, so the antioxidant ability of the SiC surface was improved.

Abstract: An alternative solution for producing logic devices in microelectronics is spintronics (SPIN TRansport electrONICS). It relies on the fact that in a magnetic layer, the electrical current can be spin polarized. To fabricate such components, a material whose electronic properties depend on its magnetic state is needed. The Mn-Ge system presents a lot of phases with different magnetic properties, which can be used for spintronics. The most interesting phase among the Mn-Ge system is Mn₅Ge₃ because of its stability at high temperatures, its Curie temperature which is close to room temperature and its ability of injecting spin-polarized electrons into semiconductors. In this paper, we have combined Reflection High-Energy Electron Diffraction (RHEED) and X-ray Diffraction (XRD), to study the sequence of formation of Mn_xGe_y phases during reactive diffusion of both a 50 nm and a 210 nm thick Mn films deposited by Molecular-Beam Epitaxy (MBE) on Ge (111).

Abstract: In order to improve the channel elecron mobility and decrease the surface roughness of SiC ,we have cleaned the SiC surfacre by hydrogen plasma with ECR–PEMOCVD plasma system. The surfaces were investigated by RHEED and X-ray Photoelectron Spectroscopy before and after hydrogen plasma cleanging. It indicated that the Si oxide content of SiC surface cleaned by hydrogen plasma for 18minutes is significantly higher than for 12 minutes and the SiC surface cleaned for 12 minutes at 200°C with ECR–PEMOCVD plasma system is the most smooth. The hydrogen plasma cleaning technology is very useful to improve the channel elecron mobility of MOS device.

Abstract: The doping of Cu in the BaSi₂ films grown by molecular beam epitaxy (MBE) with various Cu concentrations for the suitability of the solar cells was studied in this paper. The main objective of the present work is to investigate and compare the carrier concentration of Cu-doped BaSi₂ films grown with different Cu Knudsen cell temperatures and qualify as a potential candidate for more efficient solar cells. The reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) measurements and secondary ion mass spectroscopy (SIMS), were used to determine the structure, depth profile and composition of the grown samples. The electrical properties like resistivity as well as carrier concentration were measured by using a four point probe method and Van der Pauw technique, respectively. During the MBE growth, different temperatures for Cu Knudsen cell ranging from 800 to 1200 °C were chosen and the optimum growth condition for both heavily doped n-type as well as p-type in the MBE was investigated. In our previous work, the Al, Sb doped BaSi₂ were used as a potential candidate for the formation of pn-junction for solar cells, but the result was not encouraging one due to diffusion and segregation problems in the surface and BaSi₂/Si interface regions. In the present work n-type BaSi₂ layers with their dopant atoms uniformly distributed in the grown layers for the formation of high-quality of BaSi₂ pn-junction with single crystal nature were successfully developed. The realizations to develop cost effective and more efficient solar cells are inevitable for both terrestrial as well as space applications.

Abstract: In recent years, spintronics whose principle is based on controlling the spin of electrons in semiconductor layers is presented as a complementary or even an alternative solution for production of logic devices in microelectronics. It relies on the fact that electric current in a magnetic layer can be spin polarized. Manufacture of such components is based on the use of materials or heterostructures whose electronic properties depend on their magnetic state. The magnetic Mn-Ge system is interesting because of its possible development at high Curie temperature and its integration on Si substrate. Among all of the Mn-Ge phase compounds of the diagram, Mn₅Ge₃ seems the most interesting one for spintronics applications: it is a stable and ferromagnetic phase at room temperature. In this paper, we present first results of the study, by Reflection High Energy Electron Diffraction (RHEED), X-ray diffraction (XRD) and Atomic Force Microscopy (AFM), of the sequence of formation of the Mn_xGe_y phases in the case of reaction of a nanometric-thick Mn film (200nm) deposited by MBE on Ge (111).

Abstract: In situ monitoring of surface processes and understanding of growth processes are important in achieving precise control of crystal growth. Therefore, many surface monitoring techniques are used during crystal growth by molecular beam epitaxy (MBE). The most popular is reflection high-energy electron diffraction (RHEED) and photoemission current which provides information on the morphology during the growing surface. The photoemission oscillation technique has been successfully used in situ to monitor the growth of materials and to control the thickness as well as the roughness of the deposited layer. In this paper, we report results of atomic scale simulations used to study the dynamics of homoepitaxial growth of GaAs(001) β2(2x4) reconstructed surface and, in particular, the RHEED oscillations of the photoemission current.

Abstract: XPD and XRD measurements revealed a difference in the crystallographic polarity of 3C-SiC(111) grown on Si(111) carbonized by ethene diluted in hydrogen at atmospheric pressure in a rapid thermal chemical vapour deposition reactor and the crystallographic polarity of 3C-SiC(111) formed in an ethene hydrogen gas mixture at low pressures. In the first case C-face polar material was formed, whereas in the second case the grown expitaxial layer exhibits Si-face surface polarity.

Abstract: The effects of several surfactants on the homoepitaxial and heteroepitaxial growth of metallic films and multilayers have been studied and compared. Our measurements clearly revealed that pre-deposition of a small amount of surfactant prior to the adatom deposition changed thin film growth mode and structure. The pre-deposited surfactant enhanced layer-by-layer (LBL) growth of the homoepitaxial and heteroepitaxial growth of metallic films. The surfactant also enhanced the epitaxial growth of metallic multilayer.