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Darbo tikslas yra ištirti neatkaitintų ir atkaitintų prie aukštų temperatūrų vakuume LaNiO3 sluoksnių Rentgeno fotoelektronų spektrus. Darbe aprašyti Rentgeno fotoelektronų spektroskopijos (RFS) (XPS- X-ray photoelectron spectroscopy) metodo, naudojamo įvairių medžiagų paviršių cheminei sudėčiai nustatyti, pagrindai. Pirmame skyriuje aprašyti: La- Ni oksidiniai junginiai ir jų tyrimų metodika, plonų nanostruktūrizuotų medžiagų sluoksnių nusodinimo iš dujų fazės (plazmos) metodas- magnetroninis dulkinimas (magnetron sputtering), aparatūra, XPSPeak programos pritaikymas Rentgeno fotoelektronų spektrų tyrimui bei jos naudojimo galimybės. Antrasis skyrius yra skirtas Rentgeno fotoelektroninių spektrų matavimų, naudojant spektrometrą XSAM 800 (Kratos Analytical, Didžioji Britanija) ypatumams ir bandinių gamybos metodikai aptarti. Trečiajame skyriuje pateikiami eksperimentiniai rezultatai gauti, matuojant LaNiO3-x Rentgeno fotoelektronų spektrus. Darbo pabaigoje yra pateikiamos išvados, kurios galėtų būti naudingos, tobulinant LaNiO3-x bandinių gamybos technologiją. / The aim of presented work was to investigate the X-ray photoelectron spectra (XPS) of LaNiO3-x thin films. The films were produced by DC magnetron sputtering. It is known that the temperature dependence of resistivity of as grown films has the metallic character. After the temperature annealing in the high vacuum condition this dependence changes to the semiconductor like character. XPS spectra of the oxygen region of as grown samples indicate that oxygen ions are in three states – O2-, hydroxyl groups (OH)-, and water. After the temperature annealing in the high vacuum condition oxygen ions are only in the two states - O2- and hydroxyl groups (OH)-. Thus the changes of the resistivity temperature dependence are caused by the changes of the oxygen ions system after the temperature annealing in the high vacuum. After temperatures processing in vacuum the samples some time have been sustained in atmospheric conditions, the temperature dependence of resistance again came back to an initial metal condition. This fact means that for the synthesis of qualitative thin layers it is necessary to change technological conditions of production.

The shift to the Cu/low-k interconnect scheme requires the development of diffusion barrier/adhesion promoter materials that provide excellent performance in preventing the diffusion and intermixing of Cu into the adjacent dielectrics. The integration of Cu with low-k materials may decrease RC delays in signal propagation but pose additional problems because such materials are often porous and contain significant amounts of carbon. Therefore barrier metal diffusion into the dielectric and the formation of interfacial carbides and oxides are of significant concern. The objective of the present research is to investigate the fundamental surface interactions between diffusion barriers and various low-k dielectric materials. Two major diffusion barriers¾ tatalum (Ta) and titanium nitride (TiN) are prepared by DC magnetron sputtering and metal-organic chemical vapor deposition (MOCVD), respectively. Surface analytical techniques, such as X-ray photoelectronic spectroscopy (XPS), transmission electron microscopy (TEM), and atomic force microscopy (AFM) are employed. Ta sputter-deposited onto a Si-O-C low dielectric constant substrate forms a reaction layer composed of Ta oxide and TaC. The composition of the reaction layer varies with deposition rate (1 Å-min-1 vs. 2 Å-sec-1), but in both cases, the thickness of the TaC layer is found to be at least 30 Å on the basis of XPS spectra, which is corroborated with cross-sectional TEM data. Sputter-deposited Cu will not wet the TaC layer and displays facile agglomeration, even at 400 K. Deposition for longer time at 2 Å-sec-1 results in formation of a metallic Ta layer. Sputter deposited Cu wets (grows conformally) on the metallic Ta surface at 300 K, and resists significant agglomeration at up to ~ 600 K. Cu diffusion into the substrate is not observed up to 800 K in the UHV environment. Tetrakis(diethylamido) titanium (TDEAT) interactions with SiO2, Cu and a variety of low-k samples in the presence (~ 10-7 Torr or co-adsorbed) and absence of NH3 result in different products. TDEAT interactions with SiO2 are dominated by Ti interactions with substrate oxygen sites, and that Ti oxide/sub-oxide bond formation can proceed with relatively low activation energy. No Ti carbide or Si carbide formation is observed. Co-adsorption of TDEAT and NH3 on SiO2 at 120K followed by annealing to higher temperature results in enhanced Ti-N bond formation, which is stable against oxidation up to 900K in UHV. Similarly, continuous exposures of TDEAT on SiO2 at 500K in the presence of NH3 exhibit a relatively enhanced Ti-N spectral component. Co-adsorption of NH3 and TDEAT on Cu (poly) surface at 120K, followed by annealing to 500K, results in complete desorption of Ti, N or C-containing species from the Cu substrate. Reaction of TDEAT with a Cu surface at 500K yields a Ti-alkyl species via a b-hydride elimination pathway. TDEAT/Cu interactions are not observably affected by overpressures of NH3 of 10-7 Torr. TDEAT interaction with a porous carbon doped oxide low-k substrate at 700K demonstrates undissociated or partly dissociated Ti-NR species trapped in the dielectrics matrix due to its high porosity. In addition, carbide formation is observed from C(1s) XPS spectra. For a hydrocarbon low-k film, the majority sites (carbon) are highly unreactive towards TDEAT even at higher temperature due to a lack of functional groups to initiate the TDEAT/low-k surface chemistry.

Wang Yuhao = 利用X光电子谱和导电原子力显微镜对聚3, 4-乙烯二氧噻酚 : 聚苯磺酸改性的研究 / 王宇昊. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Wang Yuhao = Li yong X guang dian zi pu he dao dian yuan zi li xian wei jing dui ju 3, 4-yi xi er yang sai fen : ju ben huang suan gai xing de yan jiu / Wang Yuhao. / Abstract --- p.ii / 論文摘要 --- p.iii / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Figures --- p.ix / List of Tables --- p.xiii / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Review of conducting conjugated polymers --- p.1 / Chapter 1.1.1 --- Development of conjugated polymer --- p.1 / Chapter 1.1.2 --- Basic concepts in independent-electron theories of conducting conjugated polymers --- p.2 / Chapter 1.1.2.1 --- "Huckel model and its difficulty, the importance of election-phonon" --- p.2 / Chapter 1.1.2.2 --- The SSH model and dimerization --- p.3 / Chapter 1.1.2.3 --- "Charge carriers in conducting conjugated polymers: soliton, polaron and bipolaron" --- p.5 / Chapter 1.1.3 --- "Poly(3,4-ethylenedioxythiophene) or PEDT" --- p.5 / Chapter 1.1.4 --- Derivatives of PEDT --- p.6 / Chapter 1.1.5 --- Application of PEDT and its derivatives --- p.7 / Chapter 1.2 --- Polymeric light emitting diodes (PLED) --- p.7 / Chapter 1.2.1 --- Invention Polymeric light emitting diodes (PLED) --- p.7 / Chapter 1.2.2 --- Electric structure of PLEDs --- p.7 / Chapter 1.2.3 --- Transition from excitons to photons --- p.8 / Chapter 1.2.4 --- Controlling electron and hole injection --- p.8 / Chapter 1.2.5 --- Application of PEDT-PSS as hole transporting layer in PLED --- p.9 / Chapter 1.2.6 --- "Phase separating in PEDT-PSS blend, removing the PSS rich layer" --- p.9 / Chapter 1.3 --- Motivations of the thesis work --- p.10 / References --- p.10 / Chapter CHAPTER 2 --- INSTRUMENTATION --- p.27 / Chapter 2.1 --- X-ray Photoelectron Spectroscopy --- p.27 / Chapter 2.1.1 --- History of XPS techniques --- p.27 / Chapter 2.1.2 --- Physical Basis --- p.28 / Chapter 2.1.3 --- Chemical Shift of Binding Energy in XPS --- p.29 / Chapter 2.1.4 --- Binding Energy Referencing in XPS --- p.29 / Chapter 2.1.5 --- Sampling Depth of XPS --- p.30 / Chapter 2.1.6 --- Instrumental Setup of XPS --- p.30 / Chapter 2.2 --- Scanning Probe Microscopy --- p.31 / Chapter 2.2.1 --- Introduction --- p.31 / Chapter 2.2.2 --- Atomic Force Microscopy and Conductive Atomic Force Microscopy --- p.31 / Chapter 2.2.3 --- Instrumental Setup for Conductive AFM --- p.32 / Chapter 2.3 --- The Low Energy Ion Beam (LEIB) system at CUHK --- p.32 / Chapter 2.3.1 --- Introduction --- p.32 / Chapter 2.3.2 --- Principle --- p.33 / Chapter 2.3.3 --- Instrumentation Setup --- p.33 / References --- p.33 / Chapter CHAPTER 3 --- Effects of Ar+ bombardment at 500 and 100eV --- p.42 / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Sample Preparation --- p.42 / Chapter 3.3 --- Ar+ sputtering and XPS measurement of the sputtered sample. --- p.43 / Chapter 3.4 --- Results and Discussion --- p.44 / References --- p.49 / Chapter CHAPTER 4 --- Effects of annealing on PEDT-PSS thin films studied by XPS and AFM --- p.60 / Chapter 4.1 --- Introduction --- p.60 / Chapter 4.2 --- Sample Preparation --- p.60 / Chapter 4.3 --- XPS measurements and results --- p.61 / Chapter 4.3.1 --- XPS of C 1s core level of PEDT-PSS --- p.61 / Chapter 4.3.2 --- XPS of O 1s core level of PEDT-PSS --- p.62 / Chapter 4.3.3 --- XPS of S 2p core level of PEDT-PSS --- p.62 / Chapter 4.3.4 --- XPS of Valence Band of PEDT-PSS --- p.64 / Chapter 4.4 --- C-AFM measurements and results --- p.65 / Chapter 4.4.1 --- C-AFM measurements on PEDT-PSS --- p.65 / Chapter 4.5 --- Measurements and results about film insolubility and conductivity --- p.65 / Chapter 4.5.1 --- Insolubility measurements --- p.66 / Chapter 4.5.2 --- Conductivity measurements --- p.66 / Chapter 4.5.3 --- Results from the film insolubility and conductivity measurements --- p.66 / Chapter 4.6 --- Conclusion --- p.67 / References --- p.68 / Chapter CHAPTER 5 --- Effects of low energy proton bombardment of PEDT-PSS films studied by XPS and AFM --- p.90 / Chapter 5.1 --- Introduction --- p.90 / Chapter 5.2 --- XPS and c-AFM studies of PEDT-PSS films bombarded by H+ --- p.90 / Chapter 5.2.1 --- Sample preparation --- p.90 / Chapter 5.2.2 --- Results and discussion --- p.90 / Chapter 5.3 --- Conductivity measurements --- p.92 / Chapter 5.3.1 --- Sample preparation for conductivity measurements --- p.92 / Chapter 5.3.2 --- Results and discussion --- p.93 / Chapter 5.4 --- Conclusion --- p.93 / References --- p.93 / Chapter CHAPTER 6 --- Concluding Remarks and Future Works --- p.106 / Chapter 6.1 --- Concluding Remarks --- p.106 / Chapter 6.2 --- Future Work --- p.106 / Chapter APPENDIX --- The SSH model in describing polyacetylene --- p.108 / Chapter Part 1 --- Assumptions of the SSH model --- p.108 / Chapter Part 2 --- Bloch model and SSH model. --- p.113 / Reference --- p.117

>Magister Scientiae - MSc / Solar cells offer SA an additional energy source. While Si cells are abundantly available they are not at an optimal efficiency and the cost is still high. One technology that can enhance their performance is SiNW. However, material properties such as the diameter, porosity and length determine their effectiveness during application to solar cell technology. One method of growing SiNW uses Sn catalysts on a Si substrate. As the properties of the Sn nanoparticle govern the properties of the SiNW, this thesis investigates their formation and properties by depositing a Sn layer on a Si wafer and then subjecting it to different temperatures, during process the layer forms into nanoparticles. At each temperature the morphology, composition and crystallinity will be determined using XPS, SEM, TEM and EDS. Thus, in Chapter 1 there is an overview, Chapter 2 deals with techniques used in this study, Chapter 3 will give the quantitative and qualitative results on the XPS analysis and Chapter 4 will illustrate the structural behaviour of the annealed Sn film samples.

<p class=MsoNormal style='text-align:justify;text-indent:.5in;line-height:150%'><span style='mso-bidi-font-weight:bold'>M-DNA is a novel complex formed between DNA and transition metal ions under alkaline conditions.<span style='mso-spacerun:yes'>  </span>The unique properties of M-DNA were manipulated in order to rationally place metal ions at specific regions within a double-stranded DNA helix.<span style='mso-spacerun:yes'>   </span>Investigations using thermal denaturation profiles and the ethidium fluorescence assay illustrate that the pH at which M-DNA formation occurs is influenced heavily by the DNA sequence and base composition.<span style='mso-spacerun:yes'>  </span>For instance, DNA with a sequence consisting of poly[d(TG)d(CA)] is completely converted to M-DNA at pH 7.9 while DNA consisting entirely of poly[d(AT)] remains in the B-DNA conformation until a pH of 8.6 is reached.<span style='mso-spacerun:yes'>  </span>The pH at which M-DNA formation occurs is further decreased by the incorporation of 4-thiothymine (s⁴T).<span style='mso-spacerun:yes'>  </span>DNA oligomers with a mixed sequence composed of </span>half d(AT) and the other half d(TG)d(CA)<span style='mso-bidi-font-weight: bold'> showed that only 50% of the DNA is able to incorporate Zn²⁺ ions at pH 7.9.<span style='mso-spacerun:yes'>  </span>This suggests that only regions corresponding to the tracts of <span class=GramE>d(</span>TG)d(CA) are being transformed.<span style='mso-spacerun:yes'>   </span><o:p></o:p></span></p> <p class=MsoNormal style='text-align:justify;text-indent:.5in;line-height:150%'><span style='mso-fareast-language:ZH-CN'>Duplex DNA monolayers were self-assembled on gold through <span class=GramE>a</span> Au-S linkage and both B- and M-DNA conformations were studied using X-ray photoelectron spectroscopy (XPS) in order to better elucidate the location of the metal ions.<span style='mso-spacerun:yes'>  </span>The film thickness, density, elemental composition and ratios for samples were analyzed and compared.<span style='mso-spacerun:yes'>  </span>The DNA surface coverage, calculated from both XPS and electrochemical measurements, was <span class=GramE>approximately 1.2 x 10¹³molecules/cm²</span>for B-DNA.<span style='mso-spacerun:yes'>  </span>All samples showed distinct peaks for C 1s, O 1s, N 1s, P 2p and S 2p as expected for a thiol-linked DNA.<span style='mso-spacerun:yes'>  </span></span><span style='mso-bidi-font-weight: bold'>On addition of Zn²⁺ to form M-DNA the C 1s, P 2p and S 2p showed only small changes </span><span style='mso-fareast-language:ZH-CN'>while both the N 1s and O 1s spectra changed considerably.<span style='mso-spacerun:yes'>  </span>This result is consistent with Zn²⁺ interacting with oxygen on the phosphate backbone as well as replacing the imino protons of thymine (T) and guanine (G) in M-DNA.<span style='mso-spacerun:yes'>   </span>Analysis of the Zn 2p spectra also demonstrated that the concentration of Zn²⁺ present under M-DNA conditions is consistent with Zn²⁺ binding to both the phosphate backbone as well as replacing the imino protons of T or G in each base pair.<span style='mso-spacerun:yes'>  </span>After the M-DNA monolayer is washed with a buffer containing only Na⁺ the Zn²⁺ bound to the phosphate backbone is removed while the Zn²⁺ bound internally still remains. </span><span style='mso-bidi-font-weight:bold'>Variable angle x-ray photoelectron spectroscopy (VAXPS) was also used to examine monolayers consisting of mixed sequence oligomers.<span style='mso-spacerun:yes'>  </span>Preliminary results suggest that under M-DNA conditions, the zinc to phosphate ratio changes relative to the position of the <span class=GramE>d(</span>TG)d(CA) tract being at the top or bottom of the monolayer.<span style='mso-spacerun:yes'>  </span><span style='mso-spacerun:yes'> </span><o:p></o:p></span></p> <p class=MsoNormal style='text-align:justify;text-indent:.5in;line-height:150%'><span style='mso-bidi-font-weight:bold'>Electrochemistry was also used to investigate the properties of M-DNA monolayers on gold and examine how the localization of metal ions affects the resistance through the DNA monolayer.<span style='mso-spacerun:yes'>  </span>T</span>he effectiveness of using the IrCl₆^2-/3-redox couple to investigate DNA monolayers and the potential advantages of this system over the standard Fe(CN)₆^3-/4- redox couple are demonstrated.<span style='mso-spacerun:yes'>  </span>B-DNA monolayers were converted to M-DNA by incubation in buffer containing 0.4 mM Zn²⁺ at pH 8.6 and studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) with IrCl₆^2-/3-.<span style='mso-spacerun:yes'>  </span>^{<span style='mso-spacerun:yes'> </span>}Compared to B-DNA, M-DNA showed significant changes in CV, EIS and CA spectra.<span style='mso-spacerun:yes'>  </span>However, only small changes were observed when the monolayers were incubated in Mg²⁺at pH 8.6 or in Zn²⁺ at pH 6.0.<span style='mso-spacerun:yes'>  </span>The heterogeneous electron-transfer rate (<i style='mso-bidi-font-style:normal'>k</i>_ET) between the redox probe and the surface of a bare gold electrode was determined to be 5.7 x 10^-3 cm/s.<span style='mso-spacerun:yes'>  </span>For a B-DNA modified electrode, the <i style='mso-bidi-font-style:normal'>k</i>_ET through the monolayer was too slow to be measured.<span style='mso-spacerun:yes'>  </span>However, under M-DNA conditions, a <i style='mso-bidi-font-style:normal'>k</i>_ET of 1.5 x 10^-3 cm/s was reached.<span style='mso-spacerun:yes'>  </span>As well, the percent change in resistance to charge transfer (R_CT), measured by EIS, <span class=GramE>was</span> used to illustrate the dependence of M-DNA formation on pH.<span style='mso-spacerun:yes'>  </span>This result is consistent with Zn²⁺ ions replacing the imino protons on thymine and guanine residues.<span style='mso-spacerun:yes'>  </span>Also, at low pH values, the percent change in R_CT seems to be greater for <span class=GramE><span style='mso-bidi-font-weight:bold'>d(</span></span><span style='mso-bidi-font-weight: bold'>TG)₁₅d(CA)₁₅ compared to oligomers with mixed d(AT) and d(TG)d(CA) tracts.<span style='mso-spacerun:yes'>  </span></span>The IrCl₆^2-/3-redox couple was also effective in differentiating between single-stranded and double-stranded DNA during dehybridization and rehybridization experiments.<span style='mso-spacerun:yes'>  </span><span style='mso-bidi-font-weight:bold'><o:p></o:p></span></p>

<p class=MsoNormal style='text-align:justify;text-indent:.5in;line-height:150%'><span style='mso-bidi-font-weight:bold'>M-DNA is a novel complex formed between DNA and transition metal ions under alkaline conditions.<span style='mso-spacerun:yes'>  </span>The unique properties of M-DNA were manipulated in order to rationally place metal ions at specific regions within a double-stranded DNA helix.<span style='mso-spacerun:yes'>   </span>Investigations using thermal denaturation profiles and the ethidium fluorescence assay illustrate that the pH at which M-DNA formation occurs is influenced heavily by the DNA sequence and base composition.<span style='mso-spacerun:yes'>  </span>For instance, DNA with a sequence consisting of poly[d(TG)d(CA)] is completely converted to M-DNA at pH 7.9 while DNA consisting entirely of poly[d(AT)] remains in the B-DNA conformation until a pH of 8.6 is reached.<span style='mso-spacerun:yes'>  </span>The pH at which M-DNA formation occurs is further decreased by the incorporation of 4-thiothymine (s⁴T).<span style='mso-spacerun:yes'>  </span>DNA oligomers with a mixed sequence composed of </span>half d(AT) and the other half d(TG)d(CA)<span style='mso-bidi-font-weight: bold'> showed that only 50% of the DNA is able to incorporate Zn²⁺ ions at pH 7.9.<span style='mso-spacerun:yes'>  </span>This suggests that only regions corresponding to the tracts of <span class=GramE>d(</span>TG)d(CA) are being transformed.<span style='mso-spacerun:yes'>   </span><o:p></o:p></span></p> <p class=MsoNormal style='text-align:justify;text-indent:.5in;line-height:150%'><span style='mso-fareast-language:ZH-CN'>Duplex DNA monolayers were self-assembled on gold through <span class=GramE>a</span> Au-S linkage and both B- and M-DNA conformations were studied using X-ray photoelectron spectroscopy (XPS) in order to better elucidate the location of the metal ions.<span style='mso-spacerun:yes'>  </span>The film thickness, density, elemental composition and ratios for samples were analyzed and compared.<span style='mso-spacerun:yes'>  </span>The DNA surface coverage, calculated from both XPS and electrochemical measurements, was <span class=GramE>approximately 1.2 x 10¹³molecules/cm²</span>for B-DNA.<span style='mso-spacerun:yes'>  </span>All samples showed distinct peaks for C 1s, O 1s, N 1s, P 2p and S 2p as expected for a thiol-linked DNA.<span style='mso-spacerun:yes'>  </span></span><span style='mso-bidi-font-weight: bold'>On addition of Zn²⁺ to form M-DNA the C 1s, P 2p and S 2p showed only small changes </span><span style='mso-fareast-language:ZH-CN'>while both the N 1s and O 1s spectra changed considerably.<span style='mso-spacerun:yes'>  </span>This result is consistent with Zn²⁺ interacting with oxygen on the phosphate backbone as well as replacing the imino protons of thymine (T) and guanine (G) in M-DNA.<span style='mso-spacerun:yes'>   </span>Analysis of the Zn 2p spectra also demonstrated that the concentration of Zn²⁺ present under M-DNA conditions is consistent with Zn²⁺ binding to both the phosphate backbone as well as replacing the imino protons of T or G in each base pair.<span style='mso-spacerun:yes'>  </span>After the M-DNA monolayer is washed with a buffer containing only Na⁺ the Zn²⁺ bound to the phosphate backbone is removed while the Zn²⁺ bound internally still remains. </span><span style='mso-bidi-font-weight:bold'>Variable angle x-ray photoelectron spectroscopy (VAXPS) was also used to examine monolayers consisting of mixed sequence oligomers.<span style='mso-spacerun:yes'>  </span>Preliminary results suggest that under M-DNA conditions, the zinc to phosphate ratio changes relative to the position of the <span class=GramE>d(</span>TG)d(CA) tract being at the top or bottom of the monolayer.<span style='mso-spacerun:yes'>  </span><span style='mso-spacerun:yes'> </span><o:p></o:p></span></p> <p class=MsoNormal style='text-align:justify;text-indent:.5in;line-height:150%'><span style='mso-bidi-font-weight:bold'>Electrochemistry was also used to investigate the properties of M-DNA monolayers on gold and examine how the localization of metal ions affects the resistance through the DNA monolayer.<span style='mso-spacerun:yes'>  </span>T</span>he effectiveness of using the IrCl₆^2-/3-redox couple to investigate DNA monolayers and the potential advantages of this system over the standard Fe(CN)₆^3-/4- redox couple are demonstrated.<span style='mso-spacerun:yes'>  </span>B-DNA monolayers were converted to M-DNA by incubation in buffer containing 0.4 mM Zn²⁺ at pH 8.6 and studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) with IrCl₆^2-/3-.<span style='mso-spacerun:yes'>  </span>^{<span style='mso-spacerun:yes'> </span>}Compared to B-DNA, M-DNA showed significant changes in CV, EIS and CA spectra.<span style='mso-spacerun:yes'>  </span>However, only small changes were observed when the monolayers were incubated in Mg²⁺at pH 8.6 or in Zn²⁺ at pH 6.0.<span style='mso-spacerun:yes'>  </span>The heterogeneous electron-transfer rate (<i style='mso-bidi-font-style:normal'>k</i>_ET) between the redox probe and the surface of a bare gold electrode was determined to be 5.7 x 10^-3 cm/s.<span style='mso-spacerun:yes'>  </span>For a B-DNA modified electrode, the <i style='mso-bidi-font-style:normal'>k</i>_ET through the monolayer was too slow to be measured.<span style='mso-spacerun:yes'>  </span>However, under M-DNA conditions, a <i style='mso-bidi-font-style:normal'>k</i>_ET of 1.5 x 10^-3 cm/s was reached.<span style='mso-spacerun:yes'>  </span>As well, the percent change in resistance to charge transfer (R_CT), measured by EIS, <span class=GramE>was</span> used to illustrate the dependence of M-DNA formation on pH.<span style='mso-spacerun:yes'>  </span>This result is consistent with Zn²⁺ ions replacing the imino protons on thymine and guanine residues.<span style='mso-spacerun:yes'>  </span>Also, at low pH values, the percent change in R_CT seems to be greater for <span class=GramE><span style='mso-bidi-font-weight:bold'>d(</span></span><span style='mso-bidi-font-weight: bold'>TG)₁₅d(CA)₁₅ compared to oligomers with mixed d(AT) and d(TG)d(CA) tracts.<span style='mso-spacerun:yes'>  </span></span>The IrCl₆^2-/3-redox couple was also effective in differentiating between single-stranded and double-stranded DNA during dehybridization and rehybridization experiments.<span style='mso-spacerun:yes'>  </span><span style='mso-bidi-font-weight:bold'><o:p></o:p></span></p>

Although silicon (Si) nanostructures exhibit size dependent light emission, which can be attributed to quantum confinement, the role of surface passivation is not yet fully understood. This understanding is central to the development of nanocrystal-based detectors. This study investigated the growth, surface chemistry, passivation with deuterium (D2), ammonia (ND3) and diborane (B2D6) and the resulting optical properties of Si nanostructures. Si nanocrystals less than 6 nm in diameter are grown on SiO2 surfaces in an ultra high vacuum chamber using hot-wire chemical vapor deposition and the as grown surfaces are exposed to atomic deuterium. Temperature programmed desorption (TPD) spectra show that that the nanocrystals surfaces are covered by a mix of monodeuteride, dideuteride and trideuteride species. The manner of filling of the deuteride states on nanocrystals differs from that for extended surfaces as the formation of the dideuteride and trideuteride species is facilitated by the curvature of the nanocrystal. No photoluminescence (PL) is observed from the as grown unpassivated nanocrystals. As the deuterium dose is increased, the PL intensity also begins to increase. This can be associated with increasing amounts of mono-, di- and trideuteride species on the nanocrystal surface, which results in better passivation of the dangling bonds and relaxing of the reconstructed surface. At high deuterium doses, the surface structure breaks down and amorphization of the top layer of the nanocrystal takes place. Amorphization reduces the PL intensity. Finally, as the nanocrystal size is varied, the PL peak shifts, which is characteristic of quantum confinement. The dangling bonds and the reconstructed bonds at the NC surface are also passivated and transformed with D and NDx by using deuterated ammonia (ND3), which is predissociated over a hot tungsten filament prior to adsorption. At low hot wire ND3 doses PL emission is observed at 1000 nm corresponding to reconstructed surface bonds capped by predominantly monodeuteride and Si-ND2 species. As the hot wire ND3 dose is increased, di- and trideuteride species form and intense PL is observed around 800 nm that does not shift with NC size and is associated with defect levels resulting from NDx insertion into the strained Si-Si bonds forming Si2=ND. The PL intensity at 800 nm increases as the ND3 dose is increased and the intensity increase is correlated to increasing concentrations of deuterides. At extremely high ND3 doses PL intensity decreases due to amorphization of the NC surface. In separate experiments, Si NCs were subjected to dissociative (thermal) exposures of ammonia followed by exposures to atomic deuterium. These NCs exhibited size dependent PL and this can be attributed to the prevention of the formation of Si2=ND species. Finally, deuterium-passivated Si NCs are exposed to BDx radicals formed by dissociating deuterated diborane (B2D6) over a hot tungsten filament and photoluminescence quenching is observed. Temperature programmed desorption spectra reveal the presence of low temperature peaks, which can be attributed to deuterium desorption from surface Si atoms bonded to subsurface boron atoms. The subsurface boron likely enhances nonradiative Auger recombination. / text

This work describes the synthesis of dendrimer-encapsulated nanoparticles (DENs) and the expansion of the characterization ability for these materials. The dendrimer-template method for the synthesis of nanoparticles allows precise control over the size, composition and structure of nanoparticles in the 40-250 atom range. In this size regime, the surface structure of the nanoparticles dominates their catalytic properties. The long term goal of this research is to correlate the structure of these nanoparticles to their catalytic activity, improving the ability to predict superior catalysts a priori. As a prerequisite for this analysis, the precise structure of the catalytically active nanoparticle must be determined. Characterization of nanoparticles in the 1-2 nm region is significantly more difficult than more commonly used nanoparticles of 3-5 nm diameter or larger. Typical characterization of these nanoparticles involves UV-vis spectroscopy for Mie absorbance and transmission electron microscopy for size analysis. This work involves the use of extended X-ray absorption-fine structure (EXAFS) to determine the local structure of the nanoparticles. For monometallic Pt DENs, EXAFS was combined with UV-vis, TEM, X-ray photoelectron spectroscopy (XPS) and electrochemistry to determine that the Pt system is not simply nanoparticles but a more complex, bimodal state. EXAFS has also been used to differentiate between different bimetallic structures. For PdAu DENs, there are two synthetic methods used. When both metals are reduced simultaneously, the resulting nanoparticles have a quasi-random alloy structure. These nanoparticles were then extracted from the dendrimer into an organic solvent by use of alkanethiols. The extraction process changed the alloy structure into Au-core/Pd-shell. When Pd and Au were reduced in sequence, the DENs were formed as a Au-core/Pd-shell material, regardless of the order of the reduction of the metals. The Au-core/Pd-shell structure was also present after extraction. In addition to structural analysis to determine the result of different synthetic methods, EXAFS was also used in situ to measure the structure of Pt DENs during the oxidation of absorbed CO. These in situ measurements are important for determining the structure of the actual catalyst rather than the precursor nanoparticle. In this case, the Pt DENs changed from a bimodal distribution into fully reduced nanoparticles by the application of a reducing potential. The binding of CO to the Pt DENs and subsequent oxidation did not cause measurable agglomeration of the nanoparticles. This reduction of the Pt system by electrochemical means was also explored as a synthetic method. The Pt-dendrimer complex was placed on a TEM grid for electrochemical treatment. A potential step was shown to reduce some of the Pt-dendrimer complexes into Pt nanoparticles of the expected size. However, most of the complexes were not reduced. Therefore, only the standard chemical reduction followed by electrochemical treatment is sufficient to fully reduce the nanoparticle samples. This work has explored additional synthetic methods for the synthesis of monometallic and bimetallic DENs. The use of EXAFS, as well as other advanced characterization techniques, has advanced knowledge of the structure of various DENs. Both the characterization toolset and the synthetic methods will provide a basis for investigations of catalytically active materials. / text

Στην παρούσα διπλωματική εργασία αναλύονται λεπτά υμένια (thin films) διαφόρων πολυμερικών ή ολιγομερών οργανικών ενώσεων, με την επεξεργασία μετρήσεων που είχαν ληφθεί με την επιφανειακά ευαίσθητη τεχνική της φασματοσκοπίας φωτοηλεκτρονίων από ακτίνες Χ (XPS). Από την ανάλυση των φασμάτων XPS προκύπτουν συμπεράσματα τόσο για την παρουσία συγκεκριμένων χημικών στοιχείων στα δείγματα (ποιοτική ανάλυση) όσο και για την συγκέντρωση των στοιχείων αυτών στην περιοχή ανάλυσης (ποσοτική ανάλυση). / This thesis analyzed thin films (thin films) various polymeric or oligomeric organic compounds, the processing of measurements taken with the surface sensitive technique of spectroscopy X-ray photoelectron (XPS). From the analysis of XPS spectra resulting conclusions as to the presence of certain chemical elements in samples (qualitative analysis) and for the concentration of these elements in the analysis (quantitative analysis).