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Integrated photoelectrochemical water splitting with sunlight is one possible solution to growing global energy needs. Integration of catalysts, photoabsorbers and a membrane require low barriers to charge dissipation if a free standing device structure is to be achieved. The n-type/PEDOT:PSS junction has be identified as the major resistive component and constitutes a large barrier to charge dissipation. In this thesis, the modification of the interface between n-type Si/PEDOT:PSS was achieved by growing a highly – doped region at the contact between the wire and the membrane to reduce voltage loss at the junction from 300 mV to 130 mV. In addition, modification of the surface using a thiophene moiety is observed to decrease the voltage loss from 300 mV to 30 mV. Formation of an insulating silicon oxide on the methyl functionalized surface of the microwires identified a need for characterization of planar silicon samples representative of the sides of the microwires. Si (110), (211) and (111) crystal faces were functionalized with a methyl group and showed different resistance to oxidation. The Si (111) surface was the most resistant while the Si (211) surface was observed to be the least resistant to ambient oxidation.

Vacuum field emission devices have become a promising candidate for emerging display technology due to their interesting properties compared to conventional thermionic emission devices that require high temperature and power to operate. Unlike thermionic emission, field emission devices can induce the electrons to emit at low temperature; sharp and thin emitters on the cathode are desired in order to increase the field emission. Many candidates from other research groups, such as Carbon Nanotubes (CNTs), SiC and ZnO, appear to have high field emission, but their complicated fabrication processes are the drawback. The silicon nanowhiskers produced by Geological & Nuclear Sciences (GNS) using Electron-Beam Rapid Thermal Annealing (EB-RTA) are an alternative material that is fast, inexpensive and uncomplicated to produce. They are based on the thermal desorption of silicon oxide, which forms silicon nanowhiskers on the silicon wafer in a short duration. Field emission diode structures on Silicon on Insulator (SOI) wafers were fabricated in order to investigate the field emission due to these GNS silicon nanowhiskers. An uncomplicated fabrication process using photolithography and etching process was developed. Electron beam lithography (EBL) was also used to create the different feature sizes directly onto the SOI wafer. The silicon nanowhiskers grown on these structures are as high as 35 nm with density distribution up to 30 µm⁻¹. The electrical characteristics of these devices are diode-like when the voltage range from -40 V to 40 V is applied. The best samples produced an emitted current as high as 2 mA, which is suitable for many applications, such as flat panel displays, x-ray sources and high frequency devices. However, in some cases, the diode structures failed to show the diode-like characteristics, perhaps as a result of bad contact connections or the emitters have been worn out after applying high voltage for some time. Device life time and stability were also considered and investigated via a number of electrical measurements for a period of time as long as one hour in this study. Even though these nanowhiskers have shown promising results, there are still many aspects to be considered to improve the experiments, such as the vacuum system and better contacts.

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Difuzija – dažniausiai naudojamas procesas, gaminant elektroninius prietaisus. Anglies difuzija iš epitaksinio sluoksnio kristaliniame silicyje gali būti sukelta keliais būdais. Šiame bakalauro darbe nagrinėjame netiesinę difuziją, kai bandiniai veikiami rentgeno spinduliais. Bandymui buvo naudojamos skirtingo storio Cz-Si plokštelės, padengtos plonu dc = 10 µm anglies epitaksiniu sluoksniu. Bandiniai 1 h buvo švitinami DRON-3M difraktometru skirtingos energijos minkštaisiais rentgeno spinduliais. Vario anodo įtampos atitinkamai kiekvienai plokštelei buvo parinktos 10 kV, 20 kV ir 30 kV, o srovės stipris visais atvejais - 20 mA. Šio darbo tikslas - ištirti anglies atomų difuzijos iš epitaksinio sluoksnio į silicį priklausomybę nuo rentgeno spindulių energijos. Spinduliuotės sukelti defektai (priemaišinių anglies atomų absorbcija) buvo matuojami Furje interferometru. Eksperimentas buvo vykdomas kambario temperatūroje. Didžiausią anglies atomų difuzijos koeficientą bei įsiskverbimo gylį gavome prie 10 kV. Gautus rezultatus lyginome su termodifuzijos prie 830 C temperatūros eksperimento rezultatais. Rentgeno spinduliais sukeltos difuzijos koeficientas didesnis , o įsiskverbimo gylis - . Baigiamąjį darbą sudaro 36 puslapiai be priedų, 13 paveikslų ir 1 lentelė. / Diffusion - the most commonly used process in the production of electronic devices. Carbon diffusion in crystalline silicon from epitaxial layer can be induced in several ways. This bachelor thesis is dealing non-linear diffusion of the samples affected by X-rays. In this test were used Cz-Si plates of different thickness, coated with a thin dc = 10 µm layer of carbon epitaxial layer. The samples were irradiated for 1 h with DRON-3M diffractometer at different energy of soft X- rays . Cu anode voltage for each plate were different - 10 kV , 20 kV, 30 kV but a current of all cases - 20 mA . The goal of this test - to investigate the diffusion of carbon into the silicon epitaxial layer dependence on X-ray energy. Defects produced by radiation (carbon impurity absorption) were measured with Fourier interferometer. The experiment were made at room temperature. The largest carbon diffusion coefficient and penetration depth we received at 10 kV. The obtained results were compared with results of thermo diffusion at 830 C temperature. X-rays induced diffusion coefficient higher times, and the depth of penetration - times. The final thesis contains 36 pages, not including appendixes, it includes 13 pictures and 1 table.

There is a growing interest for relying on cleaner and more sustainable energy sources due to the negative side-effects of the dominant fossil-fuel based energy storage and conversion systems. Cleaner, electrochemical energy storage through lithium-ion batteries has gained considerable interest and market value for applications such as electric vehicles and renewable energy storage. However, capacity and rate (power) limitations of current lithium-ion battery technology hinder its ability to meet the high energy demands in a competitive and reliable fashion. Silicon is an element with very high capacity to Li-ion storage although commercially impractical due to its poor stability and rate capabilities. Nevertheless, it has been heavily researched with more novel electrode nanostructures to improve its stability and rate capability. It was found that silicon nanomaterials such as silicon nanowires have inherently higher stability due to mitigation of cracking and higher rate capability due to the short Li-ion diffusion distance. However, electrode compositions based only on silicon nanowires without additional structural features and a high conductive support do not have enough stability and rate capability for successful commercialization. One structural and conductive support of silicon materials studied in literature is graphene. Graphene-based electrodes have been reported as material capable of rapid electron transport enabling new strides in rate capabilities for Li ion batteries. This thesis presents a novel electrode nanostructure with a simple, inexpensive, scalable method of silicon nanwire synthesis on graphene nanosheets via nickel catalyst. The research herein shows the different electrode compositions and variables studied to yield the highest achievable capacity, stability and rate capability performance. The carbon coating methodology in addition to enhancing the 3D conductivity of the electrode by replacing typical binders with pyrolyzed polyacrylonitrile provided the highest performance results.

Graphene is a single layer of carbon atoms, laid out in a hexagonal lattice. The material has remarkable properties that opened up several new research areas since its discovery in 2004. One promising field is graphene based biosensors, where researchers hope to create new devices that are smaller, cheaper and more reliable than those based on today’s technology. Among several manufacturing methods, graphene grown on silicon carbide is one of the promising ones for biosensing. A chip design has been developed in order to support research into graphene on silicon carbide as a base material for biosensors. Along with the chip, a holder for electrochemical measurements has been designed and an investigation into the requirements of a custom measurement device for the sensor has been undertaken.

A novel large-scale silicon system platform with 9.6cm² of active silicon interposer area is demonstrated. The platform contains three interposer tiles and two silicon bridges, and a novel self-alignment technology utilizing positive self-alignment structures (PSAS) and a novel mechanically flexible interconnect (MFI) technology are developed and used to align and interconnect tiles and bridges on an FR4 substrate. An accurate alignment < 8μm between silicon bridges and interposer tiles makes it possible to accommodate nanophotonics to enable a high bandwidth and low-energy system in the future. In addition, mechanically flexible interconnects and silicon bridges are used to provide electrical connections between interposer tiles without having to use motherboard-level interconnects. Finally, an elastomeric bump interposer is developed to enable the packaging of PSAS-enabled silicon systems, and PSAS' compatibility with a thermo-compression bonding process is demonstrated to enable a wide range of system configurations involving interposer tiles and bridges, including the multi-chip package configuration used with the elastomeric bump interposers.