Derek J. Gardiner

Monitoring the quality of diamond films using Raman spectra excited at 514.5 nm and 633 nm

Abstract A relative Raman scattering cross-section has been experimentally determined for diamond and non-diamond carbon spectra excited by argon ion 514.5 nm radiation. This has been used to arrive at a semi-quantitative evaluation of diamond film quality. The results are compared with those obtained using helium-neon excitation at 633 nm.

Ex situ and in situ determination of stress distributions in chromium oxide films by raman microscopy

Raman microscopy has been used, in situ, to measure stress variations in a-Cr2O3 scale as it formed at 800°C on chromium metal. Stress in the growing scale was seen to decrease with increasing thickness. The stresses in adhering, buckled and spalled oxide scale, at room temperature, following oxidation at 800°C, have also been measured and are consistent with these features being the result of stress relief behaviour. The stress induced shift of the v1A1g vibrational mode of a-Cr2O3 has been determined as 2.8 ± 0.8 kbar cm−1. Raman microscopy has also been used to determine the distribution of stress, with 1 μm spatial resolution in a chromia film formed on 20Cr-25Ni-Nb stainless steel. It has been demonstrated that compressive stress at the centre of grains is relieved at grain boundaries. Values of + 19.5 kbar and −19.5 kbar were obtained for the hydrostatic parts of the stress tensors for grain and grain boundary respectively, by comparison with data obtained from chromia powder and single crystals in diamond anvil cell experiments. Results are presented in the form of Raman frequency shift profiles and a stress contour map of an entire grain and boundary.

Copper(I) halide complexes of imidazole thiones: Crystal structure of dimeric monochloro bis(1-methylimidazoline-2-thione) copper(I)

Abstract Copper(I) halides form complexes with imidazole-2-thione imtH2, 1-methylimidazoline-2-thione, imtH and 1,3-dimethylimidazoline-2-thione, dmimt of formula: Cu(imtH2)X (X = Cl, Br, I) and CuL2X (L = mimtH and dmimt; X = Cl, Br, I). These complexes have been characterised by a variety of physical and spectroscopic techniques. The crystal structure of Cu(mimtH)2Cl consists of centrosymmetrically constrained dimers occupying a monoclinic unit cell of space group P21/n with Z = 2. The dimers contain a pair of copper(I) atoms tetrahedrally coordinated by terminal chlorine and terminal S-bonded mimtH together with two S-bridging (μ2) mimtH molecules. The Cu2S2 core of the dimer is lozenge shaped with CuS distances of 2.301(1) and 2.572(1) A, a CuSCu angle of 73.2(1)° and separation distances of 2.914(1) and 3.916(1) A between copper atoms and sulphur atoms, respectively. The final R index for 1937 counter reflections is 0.0308.

Tris-(1-methylimidazoline-2(3H)-thione)copper(I) nitrate: Preparation, thermal analysis and crystal structure

Abstract The preparation of a complex of 1-methylimidazoline-2(3H)-thione) (mimtH) with copper(II) nitrate is described. A combination of elemental and thermal analysis has shown the formula to be, Cu(mimtH)3(NO3). Magnetic measurements, infrared spectroscopy and a single crystal X-ray study have established the presence of copper(I) in distorted trigonal planar, Cu(mimtH)3+, cations. Averaged dimensions within the coordination sphere are: 2.249(A) (CuS), 119.6° (SCuS) and 107.3° (CuSC). The nitrate ions form hydrogen bonds (NH O) with the imido groups of the ligands.

Stress and Structural Images of Microindented Silicon by Raman Microscopy

The microline focus spectrometer (MiFS) Raman imaging process is described and is used to investigate stress and structure defect patterns in micro-indented single-crystal silicon. Raman intensity, frequency, and bandwidth images are reported with 0.3-μm pixel resolution, which reveal residual compressive stress distributions around the indentation site and areas of tensile stress at the crack tips. A previously unreported annular structural defect region, remote from the indent site, is observed in images where the indenter tip edges are aligned with the 110 direction of the silicon crystal.

Tetrakis-[1-methylimidazoline-2(3H)-thione]μ2-[1-methylimidazoline-2(3H)-thione]-di-copper(I) sulphate trihydrate: preparation, thermal analysis and crystal structure

Abstract 1-emthylimidazoline-2(3H)-thione (mimtH) reacts with copper(II) sulphate pentahydrate in aqueous acetone to produce the dinuclear complex, Cu 2 (mimtH) 5 SO 4 · 3H 2 O; the formula has been established by a combination of chemical and thermal analysis. The monoclinic crystals, (space group P c , Z = 2), contain dinuclear cations, sulphate ions and water molecules. The dinuclear cation, Cu 2 (mimtH) 5 2+ , consists of two trigonal copper(I) atoms, four terminal, monodentate, S-donating mimtH molecules and one S-bridging (μ 2 ) mimtH molecule. Some average dimensions are:CuS, 2.258 A and SCuS, 120.0°; the CuSCu bridging angle is 94.8° and the CuCu separation distance is 3.308 A.

Automated micro-Raman mapping and imaging applied to silicon devices and zirconia ceramic stress and grain boundary morphology

An automated, point-by-point, Raman mapping and imaging system is described that combines a 0.5-μm stepper-motor-driven stage, a Raman microscope, and a filter spectrograph with an intensified diode array detector. High-resolution Raman images of a silicon device structure and a map showing the presence of the monoclinic phase of zirconia (ZrO2) at grain boundaries and in stressed regions of a sintered tetragonally stabilized ceramic are reported. The importance of image processing is demonstrated and emphasised.

Automated Mapping of High-Temperature Corrosion Products on Iron Chromium Alloy Using Raman Microscopy

An automated Raman microscope mapping system is described which uses single point analysis combined with a stepper-motor-driven microscope stage. Methods for one-dimensional full spectra line-scans and repetitive frequency selective line-scans providing a two-dimensional species map are reported. The technique is applied to a surface feature appearing on a sample of Fe-Cr steel oxidized at 800°C for 143 h. The results suggest that Fe3O4, FeCr2O4 and Cr2O3 develop fairly uniformly across much of the surface and that the formation of raised areas of more extensive corrosion is due to the absence of Cr2O3 in these regions. In addition, a sample oxidized at 675°C for two hours was ball-cratered to provide a Raman depth profile. The corrosion scale was complex—the outermost layer comprising Fe2O3 and some Fe3O4, while the inner layer consisted mainly of FeCr2O4, with some evidence of Cr2O3.

ANALYSIS OF WHITE AND BLUE PIGMENTS FROM WATERCOLOURS BY RAMAN MICROSCOPY

Summary The application of Raman microanalysis to the investigation of pigments taken from watercolours is described. The pigment samples identified include calcium carbonate (chalk), titanium dioxide in its anatase crystal form, zinc oxide, barium sulphate and ultramarine taken from a selection of watercolours. The Raman spectra of the white pigments and extenders barium carbonate, lead carbonate, lead sulphate and calcium sulphate (gypsum), and the blue pigments cerulean blue, Prussian blue, indigo, copper phthalocyanin and lapis lazuli, are also reported.

Stress and crystallinity in 〈100〉, 〈110〉, and 〈111〉 oriented diamond films studied using Raman microscopy

Stress and crystallinity variations along the growth direction in three diamond films of different preferred orientations have been investigated using Raman microscopy to monitor the change in band center and full width at half maximum (FWHM) of the first‐order diamond phonon with distance along a single diamond crystal. The results showed a consistent trend for the 〈100〉 oriented film, with both the peak position and FWHM being largest close to the silicon substrate and decreasing along the direction of crystal growth. The 〈110〉 and 〈111〉 orientations showed random variation throughout.