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Ultrathin 2.5 nm high-k aluminum oxide ͑Al 2 O 3 ͒ films on p-type silicon ͑001͒ deposited by atomic layer deposition ͑ALD͒ were investigated with noncontact atomic force microscopy ͑NC-AFM͒ in ultrahigh vacuum, using a conductive tip. Constant force gradient images revealed the presence of oxide charges and experimental observations at different tip-sample potentials were compared with calculations of the electric force gradient based on a spherical tip model. This model could be substantially improved by the incorporation of the image of the tip in the semiconductor substrate. Based on the signals of different oxide charges observed, a homogenous depth distribution of those charges was derived. Application of a potential difference between sample and tip was found to result in a net electric force depending on the contact potential difference ͑CPD͒ and effective tip-sample capacitance, which depends on the depletion or accumulation layer that is induced by the bias voltage. CPD images could be constructed from height-voltage spectra with active feedback. Apart from oxide charges large-scale ͑150-300 nm lateral size͒ and small-scale ͑50-100 nm͒ CPD fluctuations were observed, the latter showing a high degree of correlation with topography features. This correlation might be a result from the surface-inhibited growth mode of the investigated layers.

Recent efforts on growth modeling of atomic layer deposition (ALD) have emphasized the need for an accurate understanding of the process, especially of the initial stage of the deposition. In this paper the first results obtained from in situ reflective high-energy electron diffraction (RHEED) measurements during the ALD of Al 2 O 3 on Si(001), using Al(CH 3 ) 3 and H 2 O as precursors, are presented. The goal of this work is to show the feasibility of using a surface-sensitive analysis technique to study the surface chemistry during ALD. The results show the expected decrease in reflected intensity on deposition of aluminum atoms and a recovery of intensity, attributed to removal of methyl groups from the surface, on exposure to H 2 O. Growth initiation by TMA exposure, and subsequent growth inhibition are observed. A discrete time model of ALD is used to analyze the measured decay in reflected intensity.

The electrical and physical properties of CeO 2 -HfO 2 nanolaminates on Si͑100͒, by pulsed laser deposition, are investigated. Layers were deposited using pure CeO 2 and HfO 2 targets at various substrate temperatures ranging from 220 to 620°C at Ar + H 2 and O 2 and in situ postdeposition anneal of nanolaminates performed by controlled cooling from deposition temperature to room temperature under high oxygen pressure. After layer growth and anneal, top and bottom Au electrodes were deposited by sputtering. Electrical characterization was done by C-V and I-V measurements. The highest k value of 30 was found for the laminates deposited at 520°C in Ar + H 2 ambient. It is found that the properties of CeO 2 -HfO 2 nanolaminates deposited at reducing atmosphere are dependent on the layer thickness. Thicker layers showed a higher dielectric constant and higher leakage current densities than thinner layers.As a result of aggressive scaling of the dimensions of complementary metal-oxide silicon ͑CMOS͒ devices, research on new high dielectric constant ͑high-k͒ materials for replacing SiO 2 has become a major issue in materials science of dielectrics in recent years. HfO 2 is the most promising candidate, and has been investigated intensively by the semiconductor industry and research institutions. CeO 2 is also one of the promising candidates because it is thermodynamically stable on silicon, which is advantageous for reducing interfacial SiO 2 regrowth. 1 CeO 2 with its fluorite structure has a very small lattice mismatch of 0.35% on silicon that allows epitaxial or highly oriented crystalline layers. CeO 2 also has a k value of 20-26 and a bandgap of approximately 6 eV. 2 Laminated structures are used for tailoring the electrical and physical properties of oxides. 3 Conduction and valence band offsets the dielectric constant and in particular the leakage current properties of the resulting composite dielectric can be engineered by lamination. Pulsed laser deposition ͑PLD͒ is known for its flexibility and precision for growing atomically smooth alternating layers on various substrates. 4 In this work, first results of laminated CeO 2 -HfO 2 dielectric layers deposited by PLD are presented. ExperimentalCeO 2 -HfO 2 nanolaminates were grown on HF-dipped silicon ͑100͒ substrates at temperatures varying from 220 to 620°C by PLD from high-density, pure ͑above 99.99% purity͒ CeO 2 and HfO 2 targets in an ultrahigh vacuum ͑UHV͒-PLD system ͑with a base pressure below 5 ϫ 10 −9 mbar͒. A 248 nm KrF laser is used for PLD at 1 and 3 J/cm 2 for CeO 2 and HfO 2 targets, respectively. Target-tosubstrate distance was 45 mm and laser repetition rate was 5 Hz for all deposited layers. These settings resulted in a deposition rate of 0.125 nm/s. A 0.1 mbar Ar + H 2 ͑5%͒ gas mixture was used as deposition ambient to create a reducing atmosphere to prevent excessive silicon oxide formation during deposition, as well as to reduce the CeO 2 first layer to Ce 2 O 3 . The latter is thermodynamically more stable on silicon than CeO 2 toward SiO 2...

We investigated the thickness evolution of silicon dioxide grown on a silicon surface terminated by H-Si groups, at room temperature and an elevated temperature of 250 o C. At room temperature, we observed a noticeable difference in the oxidation rate between light-illuminated samples and the samples kept in the dark. No measurable difference between the oxidation of p-type Si and n-type Si was observed. To describe the low-temperature oxidation, we made further steps towards the extension of our oxidation model earlier developed for thin oxides grown in the temperature range 750-950 o C.