DSpace Collection:http://hdl.handle.net/2445/994872024-03-28T22:55:44Z2024-03-28T22:55:44ZGrowth Study and Characterization of Single-Layer Graphene Structures Deposited on Copper Substrate by Chemical Vapour Deposition. [Capítol llibre]Chaitoglou, StefanosBertrán Serra, EnricAndújar Bella, José Luishttp://hdl.handle.net/2445/1754162024-03-12T17:02:13Z2021-03-19T10:58:52ZTitle: Growth Study and Characterization of Single-Layer Graphene Structures Deposited on Copper Substrate by Chemical Vapour Deposition. [Capítol llibre]
Author: Chaitoglou, Stefanos; Bertrán Serra, Enric; Andújar Bella, José Luis
Abstract: Currently, the graphene industry is moving forward to the import of graphene in a number
of novel applications. To take full advantage of the excellent properties of the material,
the standardization of the growth process is an emergency. The suitable growth
technique should ensure the high yield, accompanied by high quality of single-layer
graphene sheets. Chemical vapour deposition is the technology that fulfils the above
requirements, promoting the growth of largescale graphene films through automatized
processes. In the present chapter, we present the latest advances in this field, summarizing
the most recent publication activity of the authors. The results outline how the
control in the growth process over parameters like the gases flow, growth temperature
and pressure can affect the nucleation density of graphene domains, the growth rate and
percent coverage. Growth of graphene domains with different morphologies depends on
the crystallographic orientation of the copper lattice. At the same time, the formation of
ripples occurs in the graphene surface as a result of the copper foil compression during
the cooling step. These ripples are responsible for the appearance of a compressive stress
in the graphene sheets. We demonstrate the control over such stress through the variation
in the hydrogen flow during the growth.2021-03-19T10:58:52ZTribological Properties of Fluorinated Amorphous Carbon Thin FilmsRubio Roy, MiguelCorbella Roca, CarlesAndújar Bella, José LuisBertrán Serra, Enrichttp://hdl.handle.net/2445/1744022024-03-12T17:02:13Z2021-02-26T10:01:13ZTitle: Tribological Properties of Fluorinated Amorphous Carbon Thin Films
Author: Rubio Roy, Miguel; Corbella Roca, Carles; Andújar Bella, José Luis; Bertrán Serra, Enric
Abstract: The peculiar electronic configuration of carbon atoms, 1s2 2s2 2p2, and the small energy
difference between their 2p and 2s orbitals, compared to the binding energy of the carbon
bonds, allow the electrons to rearrange in s and p mixed orbitals that enhance the binding
energy with other atoms. This process is called hybridization and produces three different
types of orbitals: sp = s + p, sp2 = s + p + p and sp3 = s + p + p + p.
Each different bonding state corresponds to a certain structural arrangement: sp bonding
gives rise to chain structures (with two σ bonds and two π bonds), sp2 bonding conforms
onto planar structures (three σ bonds and one π bond) and finally sp3 bonding produces
tetrahedrical structures (four σ bonds). The p orbitals that form π bonds overlap less than the
orbitals forming σ bonds. The reduced overlapping makes π bonds weaker than σ bonds.
However, a number of scenarios are possible. Sometimes, as in ethene (C2H4), a σ and π
bond combine producing a stronger bond between carbon atoms. This is called a double
bond: C=C. Triple bonds consist of a σ bond and two π bonds, as in ethyne (C2H2). Although
chemically stronger thanks to double bonds, the mechanical stability obtained with sp2
hybridization in solids is limited, due to the planar geometry. Instead, sp3 hybridization
allows the creation of a three dimensional network of σ bonds.2021-02-26T10:01:13ZEffects of anomalous propagation conditions on weather radar observationsBech, JoanMagaldi, AdolfoCodina, BernatLorente, Jeronihttp://hdl.handle.net/2445/247962024-03-12T17:02:13Z2012-05-03T07:32:05ZTitle: Effects of anomalous propagation conditions on weather radar observations
Author: Bech, Joan; Magaldi, Adolfo; Codina, Bernat; Lorente, Jeroni
Abstract: In this chapter our objective is to provide an overview of the effects of anomalous propagation conditions on weather radar observations, based mostly on studies performed by the authors during the last decade, summarizing results from recent publications, presentations, or unpublished material. We believe this chapter may be useful as an introductory text for graduate students, or researchers and practitioners dealing with this topic. Throughout the text a spherical symmetric atmosphere is assumed and the focus is on the occurrence of ground and sea clutter and subsequent problems for weather radar applications. Other related topics such as long-path, over-the-horizon propagation and detection of radar targets (either clutter or weather systems) at long ranges is not considered here; however readers should be aware of the potential problems these phenomena may have as range aliasing may cause these echoes appear nearer than they are ¿ for more details see the discussion about second trip echoes by Zrnic, this volume.2012-05-03T07:32:05Z