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Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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This work is concerned with the characterisation and observation of structural defects in bulk crystals of CdTe and Cd(_0.96)Zn(_0.04)Te and epitaxial layers of Cd(_0.24)Hg(_0.76)Te, and the validation of appropriate characterisation techniques. The driving force behind this project being the use of Cd(_x)Hg(_1-x)Te as an infra-red detector material. The cathodoluminescence technique has been shown to be an excellent technique for both the qualitative and quantitative identification of structural defects in bulk CdTe and (Cd,Zn)Te. The temperature dependent CL contrast technique is developed and is used to quantitatively distinguish dislocations and precipitates which are represented by a qualitatively similar contrast in CL micrographs. The contrast variations at both type of defect are discussed, and the temperature dependence of the contrast at dislocations is compared with contrast theories derived for the complementary electron beam induced current (EBIC) technique. The action of a saturated ferric chloride solution as a defect revealing etch for CdTe has also been investigated. The etch was found to reliably develop pits on a range of crystal orientations including the technologically important (iii)3 face of both CdTe and Cd(_0.96)Zn(_0.04)Te. Direct correlations with CL and infra-red microscopy has shown the etch to successfully reveal twin boundaries, dislocations and precipitates. The etchant is also shown to reliably develop pits in (Cd,Hg)Te epilayers. The structural quality of boules of CdTe grown by the vertical Bridgman technique with and without the accelerated crucible rotation technique (ACRT) have been assessed by CL microscopy, ferric chloride defect etching and triple axis X-ray diffraction. The use of the ACRT modification is shown to decrease die dislocation and precipitate content, and the mosaic tilt, within CdTe boules. ACRT CdTe is also shown to contain a comparable dislocation density, and a lower precipitate density, to that observed in boules of non-ACRT Cd(_0.96)Zn(_0.04)Te. The lowest mosaic tilt however is seen to occur in (_0.96)Zn(_0.04)Te. Dislocation rosettes observed in ACRT CdTe grown from a Cd rich source are shown to be a result of Cd precipitates and the crystal quality of melt grown CdTe is compared with the quality of boules of CdTe grown from the vapour using the 'Durham' technique. Defect etching and triple axis X-ray studies on epitaxial films of LPE (_0.24)Zn(_0.76)Te have indicated a reduction in the dislocation density with increasing thickness, for layer thicknesses < 6µm. In thicker regions the film dislocation density is observed to maintain a constant (or background) level, the magnitude of which varies from layer to layer. For growth on CdTe and (_0.96)Zn(_0.04)Te substrates, both containing a similar dislocation density (i.e < 5 x 10(^4) cm(^2)), the constant (thick film) dislocation density is seen to be higher than the dislocation density in the corresponding substrate, with its magnitude being dependent on the lattice misfit in the system. These observations are discussed with reference to Mattthews-Blakeslee, and dislocation half-loop, strain relief mechanisms. The fall in the dislocation density from the interface value to the constant (thick layer) value is seen to show a good fit to a strain relief model which predicts the depth dependence of dislocation densities within epitaxial films.

Ferrets are labelled Unwanted Organisms under the Biosecurity Act (1993) due to their predation on New Zealand's native protected species and their status as potential vectors of Bovine Tuberculosis. There was suspicion that ferrets could detect the infrared light-emitting equipment used to monitor predator and prey behaviour. A two-alternative forced-choice operant procedure was used to test whether five pigmented male ferrets could detect infrared (870 and 920 nm) light. First, the ferrets were taught to press a lever under a lit visible (white) light emitting diode (LED) for food rewards. After up to 101 40-minute sessions, each ferret could lever press under the lit-light at or above the pass criteria of 75% responses over four consecutive (or five out of six) sessions. The same ferrets were then tested for stimulus generalisation over different stimulus properties by changing the wavelength/colour and intensity of the lit-light. The overall mean accuracy of each ferret's response to each coloured light varied between 92% and 84%. When a red light was systematically dimmed to halve the intensity nine times, all five ferrets still met the set pass criteria with overall accuracies of between 88% and 78%. This indicated that changing the properties of the light stimuli would not disrupt the ferrets' abilities to perform the learned task. This test was a necessary prerequisite before changing the light stimuli to potentially invisible wavelengths in the infrared spectrum. The light stimulus was changed to a single infrared (870) nm LED. Two of five ferrets showed strong evidence (response accuracies of 77% 4 and 72% 2) and one ferret showed weak evidence (60% 3) that they could see the light at this wavelength. Extraneous cues such as ultrasound emitted at the onset of a stimulus light or a predictable schedule of reinforcement were eliminated as potential response cues. These tests helped to prove that the ferrets were using only the light stimulus to discriminate which stimulus was lit. It may be possible that at least some feral ferrets can detect the light produced from infrared monitoring equipment that emits light wavelengths at or below 870 nm. This has significant implications for conservation because infrared equipment is used by conservation agencies in New Zealand and overseas to monitor predator and prey behaviour in the wild. If the infrared lighting is detected by the subject being observed, then it may potentially influence the behaviour of the animal, or attract a predator towards threatened native species.

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Efficient absorption of light is required for a large number of applications such as thermo-photovoltaics,thermal imaging, bio-sensing, thermal emitters, astronomy, and stealth technology. Strong light absorbers found in nature with high intrinsic losses such as carbon black, metal-black, and carbon nano-tubes etc. are bulky, not design-tunable and are hard to pattern for micro- and nano- devices. We developed thin-film, high performance absorbers in the visible, near-, mid-, long-wave - and far-IR region based on a 3 layer metal-dielectric-metal (MDM) structure. We fabricated a 3-layerMDMabsorber with large band-widths in the visible and near IR spectral range without any lithographic patterning. This was the first demonstration in the optical range of the Salisbury Screen, which was originally invented for radar absorption. A Fabry-Perot cavity model depending on the thickness of the dielectric, but also the effective permittivity of the semi-transparent top metal gives calculated spectra that agree well with experiment. Secondly, we fabricated long-wave IR and far-IR MDM absorbers comprising surface patterns of periodic metal squares on the dielectric layer. Strong absorption in multiple bands were obtained, and these depended weakly on polarization and angle of incidence. Though such absorbers had been extensively studied by electrodynamic simulations and experiment in the visible to far- R regions, there existed no analytic model that could accurately predict the wavelengths of the multiple resonances. We developed a theoretical model for these absorbers based on standingwave resonances, which accurately predicts resonance wavelengths for experiment and simulation for the first time. Unlike metamaterial theories our model does not depend on the periodicity of the squares but only on their lateral dimension and the thickness of the dielectric. This feature is confirmed by synchrotron-based IR spectral imaging microscopy of single isolated squares.