Effect of sample thickness on carbon ejection from ultrathin graphite bombarded by keV C_{60}

Molecular dynamics computer simulations are employed to investigate the effect of a sample thickness on the ejection process from ultrathin graphite. The thickness of graphite varies from 2 to 16 graphene layers and the system is bombarded by 10 keV C₆₀ projectiles at normal incidence. The ejection yield and the kinetic energy of emitted atoms are monitored. The implications of the results to a novel analytical approach in secondary ion mass spectrometry based on the ultrathin free-standing graphene substrates and transmission geometry are discussed

Photonic structures - simulations and application

Fotonika jest szybko rozwijającą się dziedziną pozwalającą na manipulacje światłem często w zaskakujący sposób. Jedną z dziedzin badań są światłowody fotoniczne i mikrostrukturalne a wśród nich światłowody z zawieszonym rdzeniem. Mają one potencjalnie szerokie zastosowanie, m.in. jako sensory chemiczne.W pracy przeprowadzono badania nanokrystalicznego, funkcjonalizowanego tlenku tytanu(IV) z użyciem światłowodów z zawieszonym rdzeniem. Celem badań było uzyskanie dodatkowych informacji o stanach wzbudzonych tego związku.Przeprowadzono także charakteryzację odkrytego zjawiska dotyczącego światłowodów z zawieszonym rdzeniem. Efekt ten objawia się wzmocnieniem sygnału pochodzącego od czerwonego lasera (780nm) poprzez dodatkowe wprowadzanie do światłowodu światła z lasera niebieskiego (405nm).Badania zostały dodatkowo wzbogacone o symulacje propagacji oraz rozkładu pola elektromagnetycznego w zastosowanych światłowodach.Photonics is one of the fastest developing research fields. It lets one manipulate light often in an unobvious manner. Photonic and microstructural fibres, in particular suspended core optical fibres, are among the above-mentioned research. They may have interesting applications such as chemical sensing.In the thesis nanocrystalline, surface modified titanium oxide was investigated using suspended core fibres. The research was meant to give an insight into excited states of TiO2.Author also characterized a discovered effect taking place in suspended core fibres. The effect gives amplified signal from red laser (780nm) by simultaneously using blue laser (405nm).The research was also aided by performed simulations of propagation and distribution of electromagnetic field in fibres used

Polymer brushes grafted from the gold surface.

Polymer brushes are especially promising material which could be used as functional covering of the surfaces in many fields of science and technology, such as nanoelectronics, biotechnology or chemical analysis. One of the mostly examined ways of obtaining polymer brushes is the ATRP polymerisation. It is an easy, impurities resistant and predictable method of polymerisation of compounds in bulk as well as grafted on various surfaces.In this thesis I am synthesizing ATRP initiator - omega-Mercaptoundecyl Bromoisobutyrate, which can be used in future in preparing further researched polymer brush. The initiator may be used in polymerization using grafting from method especially with gold surface thanks to creating self-assembled monolayer attached to it.Szczotki polimerowe są szczególnie obiecującym materiałem, który może być wykorzystywany jako funkcjonalne pokrycie powierzchni w wielu dziedzinach takich jak nanoelektronika, biotechnologia lub analityka chemiczna. Jednym z szeroko badanych sposobów uzyskiwania szczotek polimerowych jest polimeryzacja metodą ATRP. Pozwala ona na prostą, odporną na zanieczyszczenia i przewidywalną polimeryzację związków tak w roztworze jak i szczepionych na różnych powierzchniach.Przedmiotem pracy jest synteza inicjatora ATRP - estru omega-merkaptoundecylowego kwasu bromoizobutylowego, który w przyszłości może zostać wykorzystany do utworzenia szczotki polimerowej podlegającej dalszym badaniom. Inicjator ten umożliwia polimeryzację metodą "grafting from", szczególnie przy wykorzystaniu podłoża ze złota, dzięki tworzeniu się samoorganizującej monowarstwy przyczepionej do powierzchni

Mechanisms of particle ejection from free-standing two-layered graphene stimulated by keV argon gas cluster projectile bombardment : molecular dynamics study

Molecular dynamics computer simulations are employed to investigate processes leading to particle ejection from free-standing two-layered graphene irradiated by keV argon gas cluster projectiles. The effect of the primary kinetic energy and the projectile size on the ejection process is investigated. It has been found that both these parameters have a pronounced influence on the emission of particles. The interaction between argon projectiles and graphene is strong regardless of graphene's minimal thickness. A significant portion of the primary kinetic energy is deposited into the sample. Part of this energy is used for particle emission, which is substantial. As a result, circular nanopores of various dimensions are created depending on the bombardment conditions. A major part of the deposited energy is also dispersed in a form of acoustic waves. Different mechanisms leading to particle ejection and defect formation are identified depending on the projectile energy per atom. The implications of the results to a novel analytical approach in Secondary Ion Mass Spectrometry based on ultrathin free-standing graphene substrates and a transmission geometry are discussed

Sputtering of octatetraene by 15 keV C_{60} projectiles : comparison of reactive interatomic potentials

Molecular dynamics computer simulations have been used to probe the effect of the AIREBO, ReaxFF and COMB3 interatomic potentials on sputtering of an organic sample composed of octatetraene molecules. The system is bombarded by a 15 keV C60 projectile at normal incidence. The effect of the applied force fields on the total time of simulation, the calculated sputtering yield and the angular distribution of sputtered particles is investigated and discussed. It has been found that caution should be taken when simulating particles ejection from nonhomogeneous systems that undergo significant fragmentation described by the ReaxFF. In this case, the charge state of many particles is improper due to an inadequacy of a procedure used for calculating partial charges on atoms in molecules for conditions present during sputtering. A two-step simulation procedure is proposed to minimize the effect of this deficiency. There is also a possible problem with the COMB3 potential, at least at conditions present during cluster impact, as its results are very different from AIREBO or ReaxFF

Effect of substrate thickness on ejection of phenylalanine molecules adsorbed on free-standing graphene bombarded by 10 keV C_{60}

Molecular dynamics computer simulations have been employed to investigate the effect of substrate thickness on the ejection mechanism of phenylalanine molecules deposited on free-standing graphene. The system is bombarded from the graphene side by 10 keV C_{60} projectiles at normal incidence and the ejected particles are collected both in transmission and reflection directions. It has been found that the ejection mechanism depends on the substrate thickness. At thin substrates mostly organic fragments are ejected by direct collisions between projectile atoms and adsorbed molecules. At thicker substrates interaction between deforming topmost graphene sheet and adsorbed molecules becomes more important. As this process is gentle and directionally correlated, it leads predominantly to ejection of intact molecules. The implications of the results to a novel analytical approach in Secondary Ion Mass Spectrometry based on ultrathin free-standing graphene substrates and a transmission geometry are discussed