Orientadores: Richard Landers, Abner de Siervo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T07:30:46Z (GMT). No. of bitstreams: 1 Carazzolle_MarceloFalsarella_D.pdf: 4221752 bytes, checksum: 6156780985399992bdd317898895589e (MD5) Previous issue date: 2014 / Resumo: O descobrimento de novos materiais com alta constante dielétrica e compatível com o atual processo de fabricação de dispositivos CMOS (complementary metal-oxide-semiconductor) tem sido uma grande barreira tecnológica que está impedindo as indústrias de semicondutores a manter o contínuo aumento de desempenho desses dispositivos. O principal limitante da atual tecnologia está sendo os efeitos indesejáveis de corrente de fuga através do dielétrico que ocorrem devido à contínua miniaturização dos transistores. Além de esse novo material possuir uma alta constante dielétrica também é fundamental que ele tenha uma estabilidade térmica sobre a superfície de Si ou Ge, uma vez que o processo de fabricação desses CMOS requererem tratamentos térmicos necessários para ativação dos dopantes que chegam a temperaturas da ordem de 900 oC para Si e 400 oC. O HfO2 é um excelente candidato devido a sua alta constante dielétrica mas tem apresentado problemas de estabilidade térmica sobre as superfícies de Si e Ge pois forma uma liga metálica de siliceto de háfnio em contato com o Si ou óxido de germânio em contato com o Ge. Essa tese descreve e discute os resultados de estudos sistemáticos de estabilidade térmica de filmes ultrafinos de HfO2 crescidos sobre as superfícies de Si3N4/Si nas direções cristalográficas (100) e (111) e variando as espessuras do filme de nitreto de silicio, o uso de nitreto de silício foi proposto para formar uma barreira física separando HfO2 do Si. Também foram realizados estudos de estabilidade térmica de filmes ultrafinos de HfO2 crescidos sobre as superfícies de Ge/Si(100) and Ge/Si(111), sendo que nesse caso o Ge foi crescido camada sobre camada usando o Sb como surfactante. As técnicas experimentais de XPS, ARPXS e LEED foram amplamente utilizadas e essenciais para a execução desse trabalho, especialmente em combinação com a fonte de radiação síncrotron do LNLS que permitiu a geração de espectros de alta resolução energética. Com os resultados desses trabalhos foi possível identificar uma espessura mínima do filme de Si3N4 de forma a possibilitar o seu uso como uma camada intermediária mantendo o sistema termicamente estável até 950 oC. As análises dos resultados de Ge também identificaram uma configuração termicamente estável, em especial o sistema HfO2/Ge/Si(111) não apresentou a formação da liga GeO2 durante o tratamento térmico, resultados estes atribuídos ao aumento na energia de formação do GeO2 causado pela diferença de empacotamento na direção (111) em relação a (100) / Abstract: The development of alternative high-k gate dielectrics for future complementary metal-oxide-semiconductor (CMOS) devices is indispensable in achieving both low leakage current and small equivalent oxide thickness. The thermal stability of these dielectrics on Si or Ge is a crucial issue to integrate them into CMOS, because standard device fabrication requires high temperature annealing, i.e. a dopant activation process (> 900 oC for Si and > 400 oC for Ge). HfO2 is one of the best candidates because of its high dielectric constant and high conduction band offset. On the other hand the formation of metallic Hf-silicide or GeO2 during the annealing process for activation is one of the most serious problems for Si-CMOS or Ge-CMOS, respectively. This thesis reports the results of a systematic study on the thermal stability of the HfO2 ultrathin films grown on Si3N4/Si, (100) and (111) surfaces, for different silicon nitride film thickness deposited by low energy nitrogen ion implantation technique. Also the thermal stability of HfO2 ultrathin films grown on Ge/Si(100) and Ge/Si(111) surfaces were studied as a function of annealing temperature. From these studies it was possible (1) to determine the minimum thickness of Si3N4 buffer layer to stabilize the HfO2 film up to 950 oC on top of the silicon surfaces and (2) to avoid the formation of GeO2 interlayer in the HfO2/Ge/Si(111) system probably because the crystallographic orientation of Si surface / Doutorado / Física / Doutor em Ciências

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This dissertation reports the application of nonlinear optical effects for the investigation of vibrational and electronic spectroscopy of molecules adsorbed on thin film metal oxide surfaces and metal oxide surfaces. The main emphasis of the experiments cited here is to introduce the recently developed multi-photon technique, Waveguide Surface Coherent anti-Stokes Raman Scattering Spectroscopy (WSCARS), to the scientific community. Planar optical waveguides have been utilized to generate large optical field enhancements on metal oxide surfaces. Guided waves have been employed to obtain the surface coherent anti-Stokes Raman scattering spectra of pyridine, phenol, benzene, methanol, CD₃OD, 2,4-pentadione, oxygen, ammonia and ND₃ adsorbed onto a ZnO (0001) surface. Vibrational spectra of transient species (O₂⁻) adsorbed on ZnO (0001) surface are also presented. Furthermore, the WSCARS has been used to monitor catalytic hydrogenation of ethylene adsorbed on ZnO (0001) surface. The WSCARS technique is compared with the other vibrational surface probes. Future directions and limitations of the technique are also discussed. Electronic spectra of surface bound species have been examined by resonantly enhanced surface second harmonic generation (SSHG). SHG spectra of trans-cinnamic acid adsorbed on optically cleaned fused silica have been obtained at room temperature and at 4 K. Surface second harmonic generation has been applied to study the adsorption of water and acetone onto thermally grown silicon dioxide/silicon surface. SSHG has been successfully applied to monitor photo-oxidation and photo-reduction of a rutile (110) surface. Experiments are described, data are presented, and surface-adsorbate binding modes are discussed.

This dissertation presents solid-state NMR studies that probe the dynamic and conformational properties of polymers adsorbed on solid surfaces in the dry state. The systems studied include a series of ethylene based random copolymers where the binding group is modified, and two diblock copolymer systems where the blocks have different intrinsic mobilities and surface interactions. The thesis begins by looking at the structures formed by the adsorption of poly (ethylene-co-acrylic acid) (PEA), poly (ethylene- co-vinyl alcohol) (EVOH), poly (ethylene-co-vinyl acetate) (EVA), and polyethylene (PE) on metal oxide powders (zirconia and alumina). NMR spectroscopy, FTIR-PAS, and TGA were used to characterize the surface behaviour of the systems with comparisons made between the bulk and adsorbed copolymers. 13C CPMAS, 1H and T 1 relaxation measurements were all recorded with the aim of correlating the microscopic structure of the surface with changes in NMR data. The chain conformation of adsorbed ethylene copolymers was found to strongly depend on the binding strength of the polar sticker groups with the substrates. / The chain dynamics of adsorbed diblock copolymers in the dry state are reported for the first time. Poly (styrene)-b-poly ( t-butyl acrylate) (PS-PtButA) and poly (styrene)-b-poly (acrylic acid) (PS-PAA) were selected to vary both the block size and the binding strength. Once again the primary surface characterization methods are NMR spectroscopy, FTIR-PAS, and TGA. 13C CPMAS, 1H, T1, and T1rho relaxation measurements were all recorded with the aim of correlating the surface structures with changes in NMR data. For the most part, the observed trends in the chain mobilities of the anchor (PAA) and buoy (PS) blocks with block size can be correlated with the predicted mushroom, intermediate and extended brush structures which collapse upon removal of the solvent. However, the chain mobility of the PS buoys decreases with increasing anchor block size. Although the chain mobility of the PS buoys are moderately enhanced relative to the bulk state, the mobility is sufficiently restricted to comfirm the picture of a thin glassy layer with adhesive properties similar to the surface of bulk polystyrene. / The diblock copolymers poly (2-vinylpyridine), poly (isoprene)- b-poly (2--vinylpyridine), (PI-P2VP) and poly (isoprene)- b-poly (4-vinylpyridine) (PI-P4VP) were selected to complement the PS-PAA system as both systems have been studied by surface force microscopy. The large contrast in chain mobilities of the PI and PVP blocks allowed spectral editing through variation of the 13C cross polarization parameters. The trends in mobility with block size differ from that of PS-PAA in that the segmental mobility of the buoys increases with anchor block size as expected. The chain mobility of the collapsed PI brushes is significantly enhanced as compared to the bulk state, again supporting the interpretation of surface microscopy studies which require an entropically unfavorable flattened, yet rubbery, surface structure.

Sulfur adsorbed on metallic and oxide surfaces, whether originating from gaseous environments or segregating as an impurity to metallic interfaces, is linked to the deterioration of alloy performance. This research dealt with investigations on the interactions between sulfur and iron or iron alloy metallic and oxide surfaces under ultrahigh vacuum conditions. Sulfur was either intentionally dosed from a H2S source on an atomically clean metal surface, or segregated out as an impurity from the bulk to the metal surface by annealing at elevated temperatures.

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The spallation of aluminum, chromium, and iron oxide scales is a chronic problem that critically impacts technological applications like aerospace, power plant operation, catalysis, petrochemical industry, and the fabrication of composite materials. The presence of interfacial impurities, mainly sulfur, has been reported to accelerate spallation, thereby promoting the high-temperature corrosion of metals and alloys. The precise mechanism for sulfur-induced destruction of oxides, however, is ambiguous. The objective of the present research is to elucidate the microscopic mechanism for the high-temperature corrosion of aluminum alloys in the presence of sulfur. Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM) studies were conducted under ultrahigh vacuum (UHV) conditions on oxidized sulfur-free and sulfur-modified Al/Fe and Ni3Al(111). Evaporative deposition of aluminum onto a sulfur-covered iron surface results in the insertion of aluminum between the sulfur adlayer and the substrate, producing an Fe-Al-S interface. Aluminum oxidation at 300 K is retarded in the presence of sulfur. Oxide destabilization, and the formation of metallic aluminum are observed at temperatures > 600 K when sulfur is located at the Al2O3-Fe interface, while the sulfur-free interface is stable up to 900 K. In contrast, the thermal stability (up to at least 1100 K) of the Al2O3 formed on an Ni3Al(111) surface is unaffected by sulfur. Sulfur remains at the oxide-Ni3Al(111) interface after oxidation at 300 K. During annealing, aluminum segregation to the g ¢ -Al2O3-Ni3Al(111) interface occurs, coincident with the removal of sulfur from the interfacial region. A comparison of the results observed for the Al2O3/Fe and Al2O3/Ni3Al systems indicates that the high-temperature stability of Al2O3 films on aluminum alloys is connected with the concentration of aluminum in the alloy.

Metal and oxide interactions are of broad scientific and technological interest in areas such as heterogeneous catalysis, microelectronics, composite materials, and corrosion. In the real world, such interactions are often complicated by the presence of interfacial impurities and/or high electric fields that may change the thermodynamic and kinetic behaviors of the metal/oxide interfaces. This research includes: (1) the surface hydroxylation effects on the aluminum oxide interactions with copper adlayers, and (2) effects of high electric fields on the interface of thin aluminum oxide films and Ni3Al substrate. X-ray photoelectron spectroscopy (XPS) studies and first principles calculations have been carried out to compare copper adsorption on heavily hydroxylated a- Al2O3(0001) with dehydroxylated surfaces produced by Argon ion sputtering followed by annealing in oxygen. For a heavily hydroxylated surface with OH coverage of 0.47 monolayer (ML), sputter deposition of copper at 300 K results in a maximum Cu(I) coverage of ~0.35 ML, in agreement with theoretical predictions. Maximum Cu(I) coverage at 300 K decreases with decreasing surface hydroxylation. Exposure of a partially dehydroxylated a-Al2O3(0001) surface to either air or 2 Torr water vapor results in recovery of surface hydroxylation, which in turn increases the maximum Cu(I) coverage. The ability of surface hydroxyl groups to enhance copper binding suggests a reason for contradictory experimental results reported in the literature for copper wetting of aluminum oxide. Scanning tunneling microscopy (STM) was used to study the high electric field effects on thermally grown ultrathin Al2O3 and the interface of Al2O3 and Ni3Al substrate. Under STM induced high electric fields, dielectric breakdown of thin Al2O3 occurs at 12.3 } 1.0 MV/cm. At lower electric fields, small voids that are 2-8 A deep are initiated at the oxide/metal interface and grow wider and deeper into the metal substrate, which eventually leads to either physical collapse or dielectric breakdown of the oxide film on top.