Combinatorial gas phase electrodeposition for fabrication of three-dimensional multimodal gas sensor array. - In: Materials today, ISSN 2214-7853, Bd. 33 (2020), 6, S. 2451-2457
https://doi.org/10.1016/j.matpr.2020.01.335
Localized and programmable chemical vapor deposition using an electrically charged and guided molecular flux. - In: ACS nano, ISSN 1936-086X, Bd. 14 (2020), 10, S. 12885-12894
Chemical vapor deposition is a widely used material deposition technique. It commonly provides a uniform material flux to the substrate to cause uniform thin film growth. However, the ability to precisely adjust the local deposition rate would be highly preferable. This communication reports on a chemical vapor deposition method performed in a localized and programmable fashion by introducing an electrically charged and guided molecular flux. This allows for local adjustments of the deposition rate and three-dimensional shape by controlling the electric fields. Specifically, the precursor molecules are charged and then guided by arrays of electrodynamic funnels, which are created by a patterned dielectric layer, to predetermined deposition locations with a minimal spot size of 250 nm. Furthermore, nearest neighbor coupling is reported as a shaping method to cause the deposition of three-dimensional nanostructures. Additionally, the integration of individually addressable domain electrodes offers programmable charge dissipation to achieve an ON/OFF control. The described method is applicable to a wide variety of materials and precursors. Here, the localized and programmable deposition of three-dimensional copper oxide, chromium oxide, zinc oxide, and carbon nanowires is demonstrated.
https://doi.org/10.1021/acsnano.0c03726
Structural analysis of sputtered Sc(x)Al(1-x)N layers for sensor applications. - In: Materials science and smart materials, (2020), S. 13-18
Investigation of epitaxial graphene via Raman spectroscopy: origins of phonon mode asymmetries and line width deviations. - In: Carbon, ISSN 1873-3891, Bd. 170 (2020), S. 666-676
In this work a comprehensive study is presented for the analysis of epitaxial graphene layers using Raman spectroscopy. A wide range of graphene types is covered, from defective/polycrystalline single layer graphene to multilayer graphene with low defect density. On this basis the influence of strain type, Fermi level and number of layers on the Raman spectrum of graphene is investigated. A detailed view on the 2D/G dispersion and the respective slopes of uniaxially and biaxially strained graphene is given and its implications on the asymmetry of the G peak analyzed. A linear dependency of the phonon mode asymmetry on uniaxial strain is presented in addition to the known Fermi level dependence. Additional impacts on the asymmetry are found to be arising from the defect density and transfer doping of adsorbates. The discovered transfer doping mechanism is contrary to pure phonon excitation through excitons and exhibits increasing asymmetry with increasing Fermi level. A new characteristic correlation between the 2D mode line width and the inverse I(D)/I(G) ratio is introduced that allows the determination of the strain type and layer number and explains the difference between Raman line widths of monolayer graphene on different substrates.
https://doi.org/10.1016/j.carbon.2020.07.016
Corona assisted tuning of gallium oxide growth on 3C-SiC(111)/Si(111) pseudosubstrates. - In: Materials science forum, ISSN 1662-9752, Bd. 1004 (2020), S. 102-109
Gallium oxide was grown on silicon carbide substrates using a corona discharge assisted vapor phase epitaxy process and gold catalyst. It is shown that by implementing the corona discharge the morphology of the gallium oxide can be transformed. The excitation of the gas phase and the generation of excited species directly influence the growth morphology suppressing nanowire growth and supporting the transformation into heteroepitaxial growth.
https://doi.org/10.4028/www.scientific.net/MSF.1004.102
Wurtzite SiC formation in plastic deformed 3C and 6H. - In: Materials science forum, ISSN 1662-9752, Bd. 1004 (2020), S. 243-248
Single side clamped 3C and 6H single crystal silicon carbide beams were elastic deformed using a special designed deformation stage in an electron microscope and subjected to high temperatures. The structural transitions occurring during the plastic relaxation process were recorded in situ in the electron microscope using reflection high energy electron diffraction in {110} azimuthal direction. For both polytypes, a polytype phase transition into the wurtzite silicon carbide polytype was observed independent on the surface polarity. The critical initial elastic deformation of the polytype phase transition into the wurtzite phase for the cubic silicon carbide polytype is larger compared to the 6H-SiC. This is due to the higher partial dislocation densities needed to transform the cubic modification into the wurtzite phase.
https://doi.org/10.4028/www.scientific.net/MSF.1004.243
Graphene quality assessment using an entropy approach of SEM images. - In: Materials science forum, ISSN 1662-9752, Bd. 1004 (2020), S. 525-530
In this work a new approach of analyzing epitaxial graphene layers on semi-insulating SiC through the gray-scale entropy of SEM images as a measure for the graphene inhomogeneity is demonstrated. Raman spectroscopy as a versatile and the standard tool for graphene characterization allows additionally the determination of the layer properties such as layer count, Fermi level, defect concentration and strain. It is shown that the gray-scale entropy correlates with the defect density derived from Raman measurements and thus can be used as an additional characterization technique with much higher resolution than the conventional Raman spectroscopy allows. As a consequence, the results are used to reflect the two-stepped growth itself and to conclude for advantageous growth conditions.
https://doi.org/10.4028/www.scientific.net/MSF.1004.525
Structural and local electronic properties of clean and Li-intercalated graphene on SiC(0001). - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), O 80.3
Surface structure of MOVPE-prepared GaP(111)B. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), O 91.2
Vertical current transport processes in MOS-HEMT heterostructures. - In: Applied surface science, Bd. 527 (2020), 146605
https://doi.org/10.1016/j.apsusc.2020.146605