Native alpha-cyclodextrin (alpha-CD) is found to spontaneously form films at aqueous solution/air interfaces. Shape-response measurements to volume perturbations on drops hanging from a capillary indicate that temperature and sodium dodecyl sulfate (SDS) concentration strongly modify the viscoelastic properties of such films. By using isothermal titration calorimetry (ITC), Brewster angle microscopy (BAM), atomic force microscopy (AFM), and molecular dynamics (MD) simulations, it is shown that the films consist of self-assembled nanotubes whose building blocks are cyclodextrin dimers (alpha-CD2) and alpha-CD2-SDS1 complexes.

In this article, we report film properties of HfO2 and La2O3 gate dielectrics grown on Si(100) substrate using atomic layer deposition (ALD) with various surfaces modified before film growth. The precursors used for HfO2 and La2O3 films are hafnium tetrachloride (HfCl4), lanthanum tris[bis(trimethylsilyl)amide] (C18H54N3LaSi6) and water. Pre-deposition treatments examined for HfO2 dielectric films include (1) surface nitridation using NH3, N2O, or NO, (2) substrate annealing in an oxidizing or reducing ambient, and (3) surface fluorination. These results were compared to those obtained using established approaches of growing HfO2 on an OH terminated surface produced chemically. Linear film growth was observed for the HfO2 with all pre-deposition treatments. Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) and transmission electron microscopy (TEM) analysis indicated that all pre-treatments result in good film coverage with no interaction between HfO2 and silicon at the silicon substrate. The as deposited ALD HfO2 film is mainly amorphous, continuous, and relatively smooth on all pretreated Si surface. The thickness of a thin interfacial layer varies depending on the particular pre-treatments. Similar studies were also conducted for the growth of ALD La2O3. In this case, a significant interaction between La2O3 and silicon substrate was observed on films grown directly on chemical oxide. A rough interface between La2O3 and the silicon substrate is clearly seen in XTEM results. This interaction is more significant when the film is deposited at higher temperature. The XTEM images showed that the ALD La2O3 films are mostly amorphous. Results show that independent of surface pre-treatments, interactions between La2O3 and the silicon substrate occur for the deposition conditions explored here. Electrical characterization using evaporated platinum electrodes and mercury probe of the high-k film stacks have been carried out to determine the impact of the pre-treatments on the electrical properties of the films. Results indicated that ALD HfO2 films have higher dielectric constant, lower leakage and better flatband voltage stability during post deposition annealing compared to ALD La2O3 films. These results indicate that ALD HfO2 is a more promising candidate than ALD La2O3 due to superior thermal stability in contact with silicon.

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We present a study of how patterns formed by Langmuir monolayer domains of a stable phase, usually solid or liquid condensed, propagate into a metastable one, usually liquid expanded. During this propagation, the interface between the two phases moves as the metastable phase is transformed into the more stable one. The interface becomes unstable and forms patterns as a result of the competition between a chemical potential gradient that destabilizes the interface on one hand and line tension that stabilizes the interface on the other. During domain growth, we found a morphology transition from tip splitting to side branching; doublons were also found. These morphological features were observed with Brewster angle microscopy in three different monolayers at the water/air interface: dioctadecylamine, ethyl palmitate, and ethyl stearate. In addition, we observed the onset of the instability in round domains when an abrupt lateral pressure jump is made on the monolayer. Frequency histograms of unstable wavelengths are consistent with the linear-instability dispersion relation of classical free-boundary models. For the case of dendritic morphologies, we measured the radius of the dendrite tip as a function of the dendrite length as well as the spacing of the side branches along a dendrite. Finally, a possible explanation of why Langmuir monolayers present this kind of nonequilibrium growth patterns is presented. In the steady state, the growth behavior is determined by Laplace's equation in the particle density with specific boundary conditions. These equations are equivalent to those used in the theory of morphology diagrams for two-dimensional diffusional growth, where morphological transitions of the kind observed here have been predicted.

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