Results are reported from a pilot study under the Consultative Committee for Amount of Substance (CCQM) to compare measurements of and resolve any relevant measurement issues in the amount of thermal oxide on (100) and (111) orientation silicon wafer substrates in the thickness range 1.5-8 nm. As a result of the invitation to participate in this activity, 45 sets of measurements have been made in different laboratories using 10 analytical methods: medium -energy ion scattering spectrometry (MEIS), nuclear reaction analysis (NRA), RBS, elastic backscattering spectrometry (EBS), XPS, SIMS, ellipsometry, grazing -incidence x-ray reflectometry (GIXRR), neutron reflectometry and transmission electron microscopy (TEM). The measurements are made on separate sets of 10 carefully prepared samples, all of which have been characterized by a combination of ellipsometry and XPS using carefully established reference conditions and reference parameters.The results have been assessed against the National Physical Laboratory (NPL) data and all show excellent linearity. The data sets correlate with the NPL data with average root-mean-square scatters of 0.15 nm, half being better than 0.1 nm and a few at or better than 0.05 nm. Each set of data allows a relative scaling constant and a zero thickness offset to be determined. Each method has an inherent zero thickness offset between 0 nm and 1 nm and it is these offsets, measured here for the first time, that have caused many problems in the past. There are three basic classes of offset: water and carbonaceous contamination equivalent to ∼1 nm as seen by ellipsometry; adsorbed oxygen mainly from water at an equivalent thickness of 0.5 nm as seen by MEIS, NRA, RBS and possibly GIXRR; and no offset as seen by XPS using the Si 2p peaks. Each technique has a different uncertainty for the scaling constant and consistent results have been achieved. X-ray photoelectron spectroscopy has large uncertainties for the scaling constant but a high precision and critically, if used correctly, has zero offset. Thus, a combination of XPS and the other methods allows the XPS scaling constant to be determined with low uncertainty, traceable via the other methods. The XPS laboratories returning results early were invited to test a new reference procedure. All showed very significant improvements. The reference attenuation lengths thus need scaling by 0.986 ± 0.009 (at an expansion factor of 2), deduced from the data for the other methods. Several other methods have small offsets and, to the extent that these can be shown to be constant or measurable, these methods will also show low uncertainty. Recommendations are provided for parameters for XPS, MEIS, RBS and NRA to improve their accuracy.  Crown

Using tapping mode atomic force microscopy, we studied the influence of molar mass (13.9−183 kg/mol) on the lamellar orientation at the surface of thin films of symmetric polystyrene−polybutadiene diblock copolymers prepared via spin-coating and by slow solvent-casting. The ratio between film thickness and lamellar thickness was varied between 0.5 and 10. Whereas for film thicknesses between 1 and 10 times the lamellar thickness, a lamellar orientation parallel to the film surface is preferred for low molar masses (below ∼55 kg/mol), high molar mass samples (above ∼90 kg/mol) rather form lamellae oriented perpendicular to the surface. For film thicknesses equal to the lamellar thickness, the films do not exhibit any texture, whereas for film thicknesses equal to half the lamellar thickness, a weak surface structure could be observed. This is consistent with symmetric wetting, i.e., the same block adsorbs at both film interfaces, but their selectivity is only weak. Thus, entropic contributions like chain stretching along a wall and the enrichment of free chain ends at the interface become important, and both parallel and perpendicular orientations of lamellae in thin films can occur.

Molecular self‐attack: According to mythology, a scorpion may sting itself to death; similarly, 3‐aminopropyltriethoxysilane catalyzes its own hydrolysis in the atomic layer deposition (ALD) of SiO2 thin films and nanostructures. Between 120 and 200 °C, the growth rate is constant at 0.06 nm per ALD cycle. The SiO2 films are chemically and optically pure. SiO2 nanotubes of aspect ratio 500 exhibit smooth walls of accurately controlled thickness.

No abstract

Articles you may be interested inCharacterization of cubic boron nitride growth using UV-extended real-time spectroscopic ellipsometry: Effect of plasma additions and dynamic substrate bias steps Cubic boron nitride thin film deposition by unbalanced magnetron sputtering and dc pulsed substrate biasing Phase and microstructure investigations of boron nitride thin films by spectroscopic ellipsometry in the visible and infrared spectral range

The optical dielectric functions for polarization perpendicular and parallel to the c-axis (optical axis) of pulsed-laser-deposition grown wurtzite MgxZn1−xO (0⩽x⩽0.29) thin films have been determined at room temperature using ellipsometry for photon energies from 1 to 5 eV. The dielectric functions reveal strong excitonic contributions for all Mg concentrations x. The band gap energies (E0A=3.369 eV for ZnO to 4.101 eV for x=0.29) show a remarkable blueshift. The exciton binding energy (61 meV for ZnO) decreases to approximately 50 meV for x≈0.17 and increases to approximately 58 meV for x=0.29. In contrast to ZnO, the MgxZn1−xO alloys are found uniaxial negative below the band gap energy, opposite to previously reported results.

No abstract

Articles you may be interested inStructure and optical properties of a-plane ZnO/Zn0.9Mg0.1O multiple quantum wells grown on r-plane sapphire substrates by pulsed laser deposition Erratum: "Aging effect and origin of deep-level emission in ZnO thin film deposited by pulsed laser deposition" [Appl. Phys. Lett.86, 221910 (2005)] Appl. Phys. Lett. 87, 039902 (2005); 10.1063/1.1978974 Aging effect and origin of deep-level emission in ZnO thin film deposited by pulsed laser deposition Appl. Phys. Lett. 86, 221910 (2005); 10.1063/1.1939078Er-doped ZnO thin films grown by pulsed-laser deposition