A common method of cancer treatment is radiation therapy. In radiation therapy, a treatment planning system is made to specify the dose of X-rays needed to eradicate the tumor. To assure the right amount of X-ray dosage a quality assurance is using a phantom containing radiation sensors. The sensors are made of semiconductor materials with heavy metal-based contacts. Irradiating heavy elements with a high-intensity beam such as Xrays causes secondary scattering of electrons, resulting in an additional photocurrent which may distort the signal used in the quality analysis. By exchanging the heavy-metal contact material to a lighter version such as a carbon-based material, preventing secondary scattering, the error obtained from the quality analysis can be minimized.In this thesis, characterization of contacts between radiation diodes and a copper substrate by flip-chip bonding with reduced graphene oxide-based anisotropic conducting adhesive is made. The parameters of the connections are characterized with respect to electrical, thermal and mechanical properties.Analysis of the novel contact material is done by comparing different types of graphene-based anisotropic fillers with a commercial metal-based filler. Results obtained indicate that it is possible to exchange the metal-based fillers in an anisotropic conducting adhesive with reduced graphene oxide coated polymer spheres as a contacting material for radiation sensing technology. / En vanlig metod som används för att behandla cancer är strålningsterapi. I strålningsterapi görs ett behandlingsplaneringssystem för att specificera en exakt dos av röntgenstrålning som krävs för att slå ut en tumör. För att säkerställa att man ger rätt dos av röntgenstrålning utförs en kvalitetssäkring genom att använda en fantom innehållande strålningssensorer. Sensorerna är gjorda av halvledarmaterial men har oftast anslutningar gjorda av tunga metalliska material. När man bestrålar metaller med hög intensitet, exempelvis röntgenstrålning, emitteras en sekundär spridning av elektroner i form av en fotoström som kan störa signalen i kvalitetsäkrningen. Genom att byta ut metallen som används i anslutningarna till ett kontaktmaterial med lägre atomnummer som exempelvis kolbaserade material, förhindras den sekundära spridningen av elektroner, som troligtvis minskar felet som uppstår vid kvalitetssäkringen.I detta arbete har en kartläggning av kontakter mellan stålningsdioder och ett kopparsubstrat, genom en flip-chip-bindning process med ett ledande adhesiv baserat på reducerad grafenoxid gjorts. Kontaktparametrarna som kartlagts är baserade på termiska, elektriska och mekaniska egenskaper.Kartläggningen av kontakterna har i mestadels gjort genom att jämföra olika typer av grafen baserade partiklar ett kommersiellt metalbaserat material gjort för flip-chipbindning. Resultaten från arbetet indikerar att det är möjligt att byta ut det metallbaserade partiklarna i ett anisotropt ledande adhesiv med reducerade grafenoxid-belagda polymersfärer som ett ledande material för strålningsapplikationer.

Lasers are increasingly used for a wide range of different applications for both civil and military purposes. Due to the distinct properties of laser light, use of lasers often comes with a risk of damage to the human eye and other optical sensors. Therefore, an effective laser protection is needed. 2D-materials is a relatively new class of materials, which have shown to possess many unique properties compared to its bulk counterparts. Some 2D-materials exhibit nonlinear optical (NLO) properties, and specifically optical power limiting (OPL) effects, and have therefore been researched for laser protection applications. In this work, two different 2D-materials, MXene Ti3C2 and graphene oxide (GO), have been combined with a hybrid organic-inorganic polymer, a so called melting gel (MG), to synthesise nanocomposites possessing OPL effects for laser protection applications. Different methods of incorporating the 2D-materials in the polymer matrix as well as the effect on optical properties of different concentrations of 2D-materials were investigated. The prepared nanocomposites were characterised using optical microscopy, spectroscopy and OPL measurements in order to investigate and quantify their linear and nonlinear optical properties. The MG was optically clear, mechanically stable and easy to synthesise, which makes it a suitable candidate as a matrix for a laser protection nanocomposite. Additionally, it was possible to dope the MG with the two different 2D-materials to create nanocomposites showing desirable optical properties in the visible spectrum. However, many samples showed signs of clustered 2D-particles indicating that the dispersion could be improved. Finally, OPL measurements, performed at 532 nm, showed that the MG itself exhibited OPL effects, both 2D-materials showed a stronger OPL effect than the non-doped MG and that GO-doped samples gave a better protection than the MXene samples.

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storage devices in micro sizes are receiving more and more attention. One of them, on-paper Microsupercapacitors (MSCs), has become a key energy storage device because of its good mechanical flexibility and high power density. In this project, a triphase system with electrochemically exfoliated graphene and graphene quantum dots to synergistically stabilize PEDOT:PSS in ethylene glycol/water solvent was developed for scalable and reliable inkjet printing. Without any post-treatment, the printed patterns with a large thickness (up to 9 μm, about 0.4 μm per layer) attain a sheet resistance of as low as 4 Ω2−1 and high resolution at a small drop spacing of 10 μm. Thanks to these feature, the areal capacitance of the on-paper MSCs can reach >2 mF cm−2 at a high scan rate of 1000 mV s−1. The device also exhibits excellent mechanical flexibility, long cycle life (>95% capacitance retention after 10000 cycles CV test) and long service time (retain 84% capacitance after 4 months in air without any encapsulation). Moreover, we can directly print the interconnect to connect 4 devices on paper substrate in series or in parallel and thus get rid of metal current collector. / Med den snabba utvecklingen av flexibel och bärbar elektronik får energilagringsenheter i mikrostorlek allt mer uppmärksamhet. En av dem, mikrosuperkondensatorer (MSC) på papper, har blivit en viktig energilagringsenhet på grund av sin goda mekaniska flexibilitet och höga effekttäthet. I det här projektet utvecklades ett trefasigt system med elektrokemiskt exfolierad grafen och grafenkvantprickar för att synergistiskt stabilisera PEDOT:PSS i etylenglykol/vattenlösningsmedel för skalbar och tillförlitlig bläckstråleutskrift. Utan någon efterbehandling uppnår de tryckta mönstren med stor tjocklek (upp till 9 μm, ca 0,4 μmper lager) ett arkmotstånd på så lågt som 4 Ω2−1 och hög upplösning vid ett litet droppavstånd på 10 μm. Tack vare dessa egenskaper kan den ytliga kapacitansen hos MSC på papper nå >2 mF cm−2 vid en hög skanningshastighet på 1000 mV s−1. Anordningen uppvisar också utmärkt mekanisk flexibilitet, lång livslängd (>95% kapacitansbehållning efter 10000 cykler i CV-test) och lång livslängd (behåller 84% kapacitans efter 4 månader i luft utan inkapsling). Dessutom kan vi direkt skriva ut kopplingen för att ansluta fyra enheter på papperssubstratet i serie eller parallellt och på så sätt bli av med metallströmkollektorn.

This study focuses on the visible light response of hetero-structures of TiO2-graphene- MoS2 for solar energy harvestings. The commercial P25 TiO2 nano-particles, and selfprepared layered reduced graphene oxides (RG) and MoS2 were assembled for the targeted hetero-structure materials as visible-light responsible solar harvesting cocatalysts. The hydrothermal method was applied for nano-material synthesis, the reduction of graphene oxides, and bonding formation. Multiple characterization methods (SEM-TEM, XRD, XPS, UV-VIS, PL, FT-IR, TGA) have been applied to understand the electron-hole pair separation and recombination, and performance tuning in their visible-light photo-catalysis rhodamine B (Rh.B) degradations process Compared to TiO2, an obvious red shift of light absorption (from 3.1 eV to 2.6 eV) of the as-prepared RG-TiO2 was observed by UV-vis analysis, and an enhanced photocatalytic degradation of the Rhodamine B (Rh.B) using the as-prepared RG-TiO2 was also observed in a Xe lamp exposure test. The explication of these two approaches to photocatalytic improvements were concluded as the energy gap changing, the formation of Ti-O-C chemical bonds between TiO2 and RG for charge transfer and the reduction of the band gap, as well as a likelihood of up-conversion photoluminescence mechanism (UCPL). The synthesis temperature was found to be critical factor to control binding formation and agglomeration of nano-materials. The lower and higher temperatures induced ineffective formations of preferable bonding structures and the significant agglomeration. The optimal synthesis temperature was found to be within 120 ℃-150 ℃ in the TiO2-RG system. For better understanding of the Ti-O-C bonding, a heterostructure of TiO2 nanotube arrays with GO (TNA-GO) was synthesized using the Langmuir-Blodgett (LB) assembly method. The band gap of this assemble was very close to the previous TiO2-RG synthesized below 120 ℃, which is very close to that of TiO2 nano-particles. This lead to the conclusion on the significance of the Ti-O-C bonding in the visible-light-responsible photo-catalysis solar harvestings. This study revealed the fundamental mechanisms on the bonding formations and the significant visible-light-response of hetero-structcures between commercial-available, inexpensive and non-toxic TiO2 and layered materials, such as the zero-band-gap graphene and the smaller-band-gap MoS2. This mechanisms understanding will greatly sustain applications of economical-effective and environmental-safe TiO2.

In this thesis, the effect of the sample properties on the characteristics of the hot carrier luminescence in graphene is investigated. The present work focuses on the two main issues described below. The first issue is the modification effects of near-infrared pulsed laser excitation on graphene. For excitation fluences several orders of magnitude lower than the optical damage threshold, the interaction with ultrafast laser pulses is found to cause a stable change in the properties of graphene. This photomodification also results in a decrease of the hot photoluminescence intensity. The detailed analysis shows that ultrafast photoexcitation leads to an increase in the local level of hole doping, as well as a change in the mechanical strain. The variation of doping and strain are linked with the enhanced adsorption of atmospheric oxygen caused by the distortion of the graphene surface. These findings demonstrate that ultrashort pulsed excitation can be invasive even if a relatively low laser power is used. Secondly, the variation of the hot photoluminescence intensity with the increasing charge carrier density in graphene is investigated. The electro-optical measurements performed using graphene field-effect transistors show a strong dependence of the photoluminescence intensity on the intrinsic carrier concentration. The emission intensity has a maximum value in undoped graphene and decreases with the increasing doping level. The theoretical calculations performed using a refined two-temperature model suggest that the reduction of the photoluminescence intensity is caused by an increase in the hot carrier relaxation rate. The modification of the carrier relaxation dynamics caused by photoinduced doping is probed directly using the two-pulse correlation measurements. The discovered sensitivity of the hot photoluminescence to the intrinsic carrier concentration can be utilised for spatially-resolved measurements of the Fermi level position in graphene samples, offering an advantage in resolution and speed.

Carbon is the most well-known black material in the history of man. Throughout the centuries, carbon has been used as a black material for paintings, camouflage, and optics. Although, the techniques to make other black surfaces have evolved and become more sophisticated with time, carbon still remains one of the best black materials. Another well-known black surface is black silicon, reflecting less than 0.5% of incident light in visible spectral range but becomes a highly reflecting surface in wavelengths above 1000 nm. On the other hand, carbon absorbs at those and longer wavelengths. Thus, it is possible to combine black silicon with carbon to create an artificial material with very low reflectivity over a wide spectral range. Here we report our results on coating conformally black silicon substrate with amorphous pyrolytic carbon. We present a superior black surface with reflectance of light less than 0.5% in the spectral range of 350 nm to 2000 nm.

This thesis focuses on understanding the chemistry involved in a variety of surface modification reactions, both on metal oxides and graphene. In this work, the rates of chemisorption of a prototypical phosphonic acid on ITO under several processing protocols are measured using XPS to determine the optimal procedure. UPS is used to track the dependence of the electronic structure of the system, specifically of the work function and position of the valence band maximum on coverage. Phosphonic acid monolayers with appropriate tail groups can also be used to initiate chemistry from surfaces, which has potential for building layers of organic-electronic devices, including organic solar cells and capacitors. The growth of non-conjugated polymers from BaTiO₃ nanoparticles using a facile ATRP technique is studied via solution-phase and solid-state techniques to determine its applicability to make matrix-free composites for hybrid dielectrics. In addition, the surface chemistry involved in Kumada Catalyst-Transfer to grow polythiophene derivatives from ITO is examined via XPS. Finally, the newly emerged alternative for replacement of ITO as transparent electrode, graphene, is n- and p-doped using redox-active, solution-processable metal-organics, which increased its conductivity and allowed the work function to be tuned over a range of 1.8 eV. The systems are characterized in a systematic study, and the results are promising for future applications of graphene.