We have investigated the influence of hard spherical hydrophilic nanoparticles (fumed silica) on the phase behavior of PS/PVME (polystyrene/polyvinyl methyl ether) blend as a compatibilizer. The size of nanoparticles is comparable to the radius of gyration of the polymers and the particles preferentially segregate into one of the polymeric components. Phase separation was assessed using rheological analysis (RMS), differential scanning calorimetry (DSC), and optical microscopy (OM). In order to investigate the kinetics of phase separation in the presence of nanoparticles, time sweep experiments were employed via rheological analysis and OM. A certain composition of PS/PVME was highly concerned to shed light on the dynamic of phase separation, in the presence of nanoparticles, in the unstable region of phase diagram. The phase diagram shifted up nearly 10°C in the presence of nanoparticles. Blends compatibilized by spherical nanoparticles could provide an interesting and economic alternative to the conventional methods of compatibilization by block copolymers.

Palladium nanoparticles were synthesized by thermal decomposition of palladium(II) hexafluoroacetylacetonate (Pd(hfac)2), an atomic layer deposition (ALD) precursor, on a TiO2(110) surface. According to X-ray photoelectron spectroscopy (XPS), Pd(hfac)2 adsorbs on TiO2(110) dissociatively yielding Pd(hfac)(ads), hfac(ads), and adsorbed fragments of the hfac ligand at 300 K. A (2 × 1) surface overlayer was observed by scanning tunneling microscopy (STM), indicating that hfac adsorbs in a bidentate bridging fashion across two Ti 5-fold atoms and Pd(hfac) adsorbs between two bridging oxygen atoms on the surface. Annealing of the Pd(hfac)(ads) and hfac(ads) species at 525 K decomposed the adsorbed hfac ligands, leaving PdO-like species and/or Pd atoms or clusters. Above 575 K, the XPS Pd 3d peaks shift toward lower binding energies and Pd nanoparticles are observed by STM. These observations point to the sintering of Pd atoms and clusters to Pd nanoparticles. The average height of the Pd nanoparticles was 1.2 ± 0.6 nm at 575 K and increased to 1.7 ± 0.5 nm following annealing at 875 K. The Pd coverage was estimated from XPS and STM data to be 0.05 and 0.03 monolayers (ML), respectively, after the first adsorption/decomposition cycle. The amount of palladium deposited on the TiO2(110) surface increased linearly with the number of adsorption/decomposition cycles with a growth rate of 0.05 ML or 0.6 Å per cycle. We suggest that the removal of the hfac ligand and fragments eliminates the nucleation inhibition of Pd nanoparticles previously observed for the Pd(hfac)2 precursor on TiO2.

Atomic layer deposition (ALD) of alumina using trimethylaluminum (TMA) has technological importance in microelectronics. This process has demonstrated a high potential in applications of protective coatings on Cu surfaces for control of diffusion of Cu in Cu2S films in photovoltaic devices and sintering of Cu-based nanoparticles in liquid phase hydrogenation reactions. With this motivation in mind, the reaction between TMA and oxygen was investigated on Cu(111) and Cu2O/Cu(111) surfaces. TMA did not adsorb on the Cu(111) surface, a result consistent with density functional theory (DFT) calculations predicting that TMA adsorption and decomposition are thermodynamically unfavorable on pure Cu(111). On the other hand, TMA readily adsorbed on the Cu2O/Cu(111) surface at 473 K resulting in the reduction of some surface Cu1+ to metallic copper (Cu0) and the formation of a copper aluminate, most likely CuAlO2. The reaction is limited by the amount of surface oxygen. After the first TMA half-cycle on Cu2O/Cu(111), two-dimensional (2D) islands of the aluminate were observed on the surface by scanning tunneling microscopy (STM). According to DFT calculations, TMA decomposed completely on Cu2O/Cu(111). High-resolution electron energy loss spectroscopy (HREELS) was used to distinguish between tetrahedrally (Altet) and octahedrally (Aloct) coordinated Al3+ in surface adlayers. TMA dosing produced an aluminum oxide film, which contained more octahedrally coordinated Al3+ (Altet/Aloct HREELS peak area ratio ≈ 0.3) than did dosing O2 (Altet/Aloct HREELS peak area ratio ≈ 0.5). After the first ALD cycle, TMA reacted with both Cu2O and aluminum oxide surfaces in the absence of hydroxyl groups until film closure by the fourth ALD cycle. Then, TMA continued to react with surface Al–O, forming stoichiometric Al2O3. O2 half-cycles at 623 K were more effective for carbon removal than O2 half-cycles at 473 K or water half-cycles at 623 K. The growth rate was approximately 3–4 Å/cycle for TMA+O2 ALD (O2 half-cycles at 623 K). No preferential growth of Al2O3 on the steps of Cu(111) was observed. According to STM, Al2O3 grows homogeneously on Cu(111) terraces.

The reaction between adsorbed trimethylaluminum (TMA) and water was studied on Pt(111) and Pd(111) surfaces. Upon exposure to TMA at approximately 10 −5 mbar, C-and Al-containing species appeared on both surfaces, as observed by X-ray photoelectron spectroscopy (XPS). On both surfaces, the adsorbed Al oxidation state observed by XPS was closest to metallic. Density functional theory (DFT) calculations suggest that decomposition to methyl aluminum (Al-CH 3 ; "MMA") or atomic Al is thermodynamically favorable. The formation of a Pd−Al alloy was observed on Pd (111), but Pt−Al alloy formation was not observed on Pt(111). Following TMA adsorption, each surface was exposed to water vapor at 400°C either at a pressure of 7 × 10 −6 mbar (UHV-XPS) or at 0.1 mbar (in situ XPS). The substrate and water dosing conditions determined the ability of each surface to remove residual carbon: on Pt(111), carbon from the TMA precursor was removed from Pt(111) during 0.1 mbar water exposure at 400°C, whereas carbon was not removed after the 7 × 10 −6 mbar water exposure. On Pd(111), however, carbon-containing fragments of TMA were removed at both water pressures. XPS also revealed another effect of water dosing conditions: the as-deposited Al was only fully oxidized to Al 2 O 3 during water exposure at 0.1 mbar, whereas mixed hydroxidecontaining and metallic Al species persisted after exposure to water at 7 × 10 −6 mbar on both surfaces.

The behavior of trimethylaluminium (TMA) was investigated on the surfaces of Pt(111) andPd(111) single crystals. TMA was found to dissociatively adsorb on both surfaces between 300 -473 K. Surfaces species observed by high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS) after TMA adsorption at 300 K included Al-CH 3 and CH x,ads (x = 1, 2, or 3) on Pt(111), and ethylidyne (CCH 3 ), CH x,ads (x = 1, 2, or 3), and metallic Al on Pd(111). Density functional theory (DFT) calculations predicted methylaluminum (MA, Al-CH 3 ) to be the most kinetically favorable TMA decomposition product on (111) terraces of both surfaces, however, HREELS signatures for Al-CH 3 were detected only on Pt(111), whereas ethylidyne was observed on Pd(111). XPS demonstrated higher amount of carbonaceous species on Pt(111) than on Pd (111) DFT calculations showed that further dissociation of MA to metallic aluminum and methyl groups to be more kinetically favorable on step sites of both metals. In our proposed reaction mechanism, MA migrates to and dissociates at Pd(111) steps at 300 K forming adsorbed methyl groups and metallic Al. Some methyl groups dehydrogenate and recombine forming ethylidyne. Metallic Al or ejected Pd atoms from steps diffuse across Pd(111) terraces until coalescing into irregularly shaped islands on terraces or steps, as observed by scanning tunneling microscopy (STM). Upon heating above 300 K, the Pd-Al alloy diffuses into the Pd bulk. On Pt(111), a high coverage of carboncontaining species following TMA adsorption at 300 K prevented MA diffusion and dissociation at steps, as evidenced by isolated clusters of MA in STM images. Heating above 300 K resulted in MA dissociation, but no Pt-Al alloy formation was observed. We conclude that the differing abilities of Pd and Pt to hydrogenate carbonaceous species plays a key role in MA dissociation and alloy formation, and, therefore, the adsorption and dissociation chemistry of TMA depends on properties of the metal substrate surface and determines thin film morphology and composition.