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Two high-k gate stacks with the structure Si/SiO"2/HfO"2/TiN/poly-Si are characterised using nanoanalytical electron microscopy. The effect of two key changes to the processing steps during the fabrication of the stacks is investigated. Electron energy-loss spectroscopy is used to show that the TiN layer has a very similar composition whether it is deposited by PVD or ALD. Spectrum imaging in the electron microscope was used to profile the distribution of elements across the layers in the stack. It was found that when the anneal after HfO"2 deposition is carried out in a NH"3 atmosphere instead of an O"2 atmosphere, there is diffusion of N into the SiO"2 and HfO"2 layers. There is also significant intermixing of the layers at the interfaces for both wafers.

Analytical electron microscopy techniques are used to investigate elemental distributions across a high-k dielectric stack with a metal gate. Electron energy-loss spectroscopy results from a Si(100)/SiO2/HfO2/TiN/poly-Si gate stack prior to activation show evidence of interface reactions having occurred with the formation of an oxide layer at the TiN/poly- Si interface.

A previous study of chromite and ferrite spinels revealed energy-loss near-edge structure (ELNES) in the oxygen K-edge that could not be reproduced in non-spin polarised calculations. Chromite and ferrite spinels typically undergo transitions to long range ordered magnetic structures at temperatures below ~15K. A model in which dynamic magnetic short range order (SRO) persists above the Neel temperature until 100K has been proposed using neutron powder diffraction. In the TEM, the interaction time of the fast electron with the specimen is sufficiently short for dynamic magnetic interactions to influence the observed ELNES at 300K. Here we present new spin polarised calculations performed using the commercially available codes FEFF8.2 and Wien97. The calculated oxygen K-edge ELNES show improved agreement with experiment when magnetic interactions are included in the calculation.

Electron beam damage effects on a partially and a fully processed HfO2 gate stack on silicon substrates are investigated, and their origins and prevention are discussed. Growth of silica between the silicon and hafnia layers is observed for the partially processed sample but is not seen for the fully processed wafer. Two sources of oxygen are found to react with the substrate to form silica. One is from the glue used in sample preparation. The oxygen from this source can be prevented from diffusing to the substrate by putting a gold barrier layer between the stack and the glue. The other source seems to come from the amorphous HfO2 layer. Using a cooling rod sufficiently slows the diffusion rate so that growth is no longer observed.

Thinning specimens to electron transparency for electron microscopy analysis can be done by conventional (2 - 4 kV) argon ion milling or focused ion beam (FIB) lift-out techniques. Both these methods tend to leave ''mottling'' visible on thin specimen areas, and this is believed to be surface damage caused by ion implantation and amorphisation. A low energy (250 - 500 V) Argon ion polish has been shown to greatly improve specimen quality for crystalline silicon samples. Here we investigate the preparation of technologically important materials for nanoanalysis using conventional and lift-out methods followed by a low energy polish in a GentleMill™ low energy ion mill. We use a low energy, low angle (6 - 8°) ion beam to remove the surface damage from previous processing steps. We assess this method for the preparation of technologically important materials, such as steel, silicon and GaAs. For these materials the ability to create specimens from specific sites, and to be able to image and analyse these specimens with the full resolution and sensitivity of the STEM, allows a significant increase of the power and flexibility of nanoanalytical electron microscopy.

Superconducting thin films of Nd1−xBa2+xCu3O7−δ have been grown on single crystal SrTiO3 substrates by pulsed laser deposition (PLD) using an off-stoichiometric Nd0.97Ba2.03Cu3O6 (Ba-rich NBCO) target. The statistical methods of Experimental design and regression analysis were used to understand and optimise the growth mechanism. The structural properties of both the target and the films were investigated by X-ray diffraction (XRD). The surface morphology of the films was examined by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). Electron probe microanalysis (EPMA) using a scanning electron microscope equipped with wavelength-dispersive X-ray (WDX) spectrometers was used to carry out qualitative and quantitative analysis of both the target and films. Micro-Raman spectroscopy was used to study the oxygen sublattice vibrations of both the target and the films.

Raman spectroscopy is a form of vibrational spectroscopy that is well suited to the molecular identification of a variety of analytes, including both explosives and biological agents. The technique has been gaining more widespread interest due to improvements in instrumentation, sensitivity, and its ease of use, in comparison to other techniques. In this paper, we describe recent advances in Raman spectroscopy with respect to the detection of high-energy explosives and biological materials. In particular, emphasis is placed on the exploitation of enhancement factors that overcome traditional limitations on sensitivity, namely, surface enhancement and resonance enhancement, functionalization of target analytes, and the use of novel lab-on-a-chip technology.

The thermal budget involved in processing high-k gate stacks can cause undesirable physical and chemical changes which limit device performance. The transmission electron microscope and associated analytical techniques provide a way of investigating these changes on a sub-nanometre scale. Using electron energy loss near edge structure (ELNES), information on the local chemistry may be extracted. These techniques are applied to high-k dielectric stacks grown on Si and containing HfO2 and HfSiO layers.

Superconducting thin films of Nd1−xCaxBa2Cu3O7−δ (x = 0.03 and 0.08) have been grown on single crystal SrTiO3 substrates by pulsed laser deposition. The statistical methods of Experimental Design and regression analysis were used to optimize the film properties and to understand the correlation between the growth parameters and film properties. The orientation of the films was investigated by x-ray diffraction. The surface morphology of the films was examined by atomic force microscopy and scanning tunnelling microscopy. Qualitative and quantitative elemental analyses of the films were carried out using electron probe microanalysis. Micro-Raman spectroscopy was used to study the oxygen sublattice vibrations of the films. The effect of annealing on the superconducting transition temperature of the patterned films was also studied.

Hafnia and hafnium silicate thin films and bulk powders were analysed using thermal analysis, X-ray diffraction and transmission electron microscope techniques to improve understanding of the crystallisation mechanism of the dielectric material. It was found that thin films exhibit instability under device processing conditions. Starting precursors greatly affect the crystallisation pathway in the bulk materials. By studying these phenomena a better understanding of the chemistry involved during crystallisation can be gained.

There is a continued interest in the development of new on-chip protocols for the determination of the causes of infectious disease. In this paper, we demonstrate the use of surface-enhanced resonance Raman scattering (SERRS) for detecting the clinically relevant nucleic acid sequences of Chlamydia trachomatis in a bead-based lab-on-a-chip format, incorporating a solid-phase sample clean-up on-chip. The assay uses streptavidinated polymer microspheres to capture a biotinylated PCR product of the oligonucleotide sequence, which was subsequently hybridized against a complementary rhodamine-labeled, Raman active probe. Central to the assay is an in-channel integrated microfilter, which was used to retain the microspheres, enabling the bound target to be separated from the rest of the sample as part of a solid-phase clean-up (thereby removing any contributions from the background). After washing, the bound Rhodamine labeled detection probe was released thermally from the microspheres by heating and was subsequently mixed on-chip with a stream of silver nanoparticles. The signal was detected downstream using a Raman spectrometer to collect the SERRS response. The assay offers several advantages over traditional laboratory methods, including: the speed of the assay on-chip, the potential for sample clean-up; and the low volume of sample required.

We demonstrate three-dimensional trapping of micrometer-diameter silica particles, partially coated with silver, within conventional optical tweezers. Although metallic particles are usually repelled from the beam focus by the scattering force, we show that transparent spheres partially coated with silver can be trapped with efficiencies comparable with dielectric particles. The trapping characteristics of these particles are examined as a function of metallic coverage, and the application of these particles to surface-enhanced resonance Raman scattering is investigated.

Surface-enhanced resonance Raman scattering (SERRS) is considerably more efficient than Raman spectroscopy, thereby enabling the detection of single molecules. Strong and short-lived SERRS emissions (

Remote nanoparticle detection is required for the development of in situ biological probes. Here we describe the labelling of silver nanoparticles to produce multiply coded particles which can be detected by surface enhanced resonance Raman scattering (SERRS). There is a potential for thousands of codes to be written and read without the need for spatial resolution of components of the code. The use of these systems in bioanlaysis and in situ detection is discussed.

The energy-loss near-edge structure (ELNES) at the oxygen $K$ edge in two $AB_2O_4$ spinels (A=Mg, B=Al,Cr) is reported. In $MgAl_2O_4$ the experimental data is successfully modelled within the LDA framework. In the case of $MgCr_2O_4$ spin-polarisation, in the form of antiferromagnetic ordering on the Cr sub-lattice, must be included despite the fact that the measurements were performed at approximately 30 times above $T_N$. A model in which dynamic short-range antiferromagnetic ordering is present at room temperature is proposed to explain the results of the experiments and calculations., 10 pages, 3 figures

Magnetic ordering has been shown to have a significant effect on the shape of the oxygen K-edge energy-loss near edge structure (ELNES) in a series of chromite spinels. However, the ELNES of these materials has only been simulated using a rough approximation of antiferromagnetism - the true nature of the magnetic interactions responsible for the detailed oxygen K-edge shape is still unknown. Chromite spinels typically undergo transitions to long range ordered antiferromagnetic (AFM) structures at temperatures below ~15K. Dynamic short range magnetic order (SRO) has been observed at temperatures up to 150K using neutron powder diffraction (NPD). It is not clear whether long range magnetic order, short range magnetic order or paramagnetic effects are responsible for the characteristic oxygen K-edge ELNES observed at room temperature. Here we discuss the possibility of carrying out paramagnetic simulations using the real space multiple scattering program FEFF8.2, and show preliminary results of paramagnetic simulations of the oxygen K-edge ELNES of magnesium chromite.

The syntheses of a number of azo and azine dyes with various surface attachment groups is described. The dyes use different methods of achieving surface complexing and are evaluated for their suitability as multiple labels for SERRS. The surface complexing agents, 8-hydroxyquinoline, benzotriazole, and pyridine are both shown to form robust layers on the silver surface. The relative intensities of the SERRS signals from each dye were shown to be predictive by considering the molar absorption coefficient at the laser excitation frequency.

The first simultaneous detection of three dye-labelled oligonucleotides in a microfluidics chip by SERRS is reported.

The results of a systematic study of the oxygen K-edge electron energy-loss spectroscopy (ELNES) from a series of aluminium- and chromium-containing spinels are presented. Extra fine structure in the region up to 10 eV above the edge onset is observed for the chromium-containing compounds and is assigned to transitions to states created by mixing of oxygen 2p and metal 3d orbitals. The experimental data has been simulated using the multiple scattering code, FEFF8. Good agreement was obtained in the case of magnesium aluminate, but relatively poor agreement was obtained in the case of the chromites. The possible fingerprints in the oxygen K-edge ELNES corresponding to a high degree of inversion in the spinel structure and to a tetragonal distortion of the cubic structure are discussed.

Silica particles were partially coated with silver, and a suitable chromophore, such that they could be trapped within an optical tweezers system and simultaneously be excited to emit a surface–enhanced resonance Raman scattering (SERRS) spectrum. A standard 1064 nm TEM00 mode laser was used to trap the bead whilst a frequency doubling crystal inserted into the beam gave several microwatts of 532 nm co-linear light to excite the SERRS emission. The configuration has clear applications in providing apparatus that can manipulate a particle whilst simultaneously obtaining surface sensitive sensory information.