Made available in DSpace on 2014-10-09T12:45:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:48Z (GMT). No. of bitstreams: 1 07289.pdf: 1409533 bytes, checksum: ae80bf28ff4706eac9069ba157863cf9 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:98/05254-9

The objective of this dissertation is the development of the necessary processing steps needed to manufacture infrared photodiodes on InAs1-xSbx material. Preliminary surface preparation steps were performed on both InAs and InSb material, thus covering both possible extremes of the antimony mole fraction. The first experiments endeavoured to characterise the effect of several possible etchants with regards to etch rate, repeatability, limitations for photolithographic patterning and the resultant surface roughness. The etchants investigated include a lactic acid based etchant, a sulphuric acid based etchant, an acetic acid based etchant, an ammonium based etchant, a hydrochloric acid based etchant as well as an organic rinse procedure. These cleaning and etching steps were evaluated at several temperatures. Measurements were performed on an Alpha Step stylus profiler as well as an atomic force microscope. Metal-insulator-semiconductor capacitor devices were manufactured, on both InAs and InSb material, in order to investigate the effects of the above-mentioned etchants combined with surface passivation techniques in terms of surface state densities. Capacitance-versus-bias voltage measurements were done to determine the resultant surface state densities and to compare these to the surface state density of an untreated reference sample. The surface passivation techniques included KOH, Na2S as well as (NH4)2S anodisation. Auger electron spectroscopy measurements were done on InAs and InSb material in order to examine possible surface contamination due to the etchants as well as combinations of these etching and anodisation procedures. The extent of surface coverage by contaminants as well as by the intrinsic elements was measured. The results of the cleaning and etching as well as the surface passivation studies were used to manufacture photovoltaic infrared diodes on an MOCVD (metal oxide chemical vapour deposition) grown p-InAs0.91Sb0.09/i- InAs0.91Sb0.09/n-GaSb structure. Current-versus-voltage and electro-optical measurements were performed on the these diodes in order to evaluate the effect of sulphuric acid based etching combined with KOH, Na2S or (NH4)2S anodisation on the detector performance. The results of surface passivated structures were compared to those of an unpassivated reference detector.

A sensing method that can monitor metallic structures continuously would eventually produce safer metallic structures as well as a more efficient and economic way to monitor corrosion. A secondary focus of this research is the implementation of a fiber optic sensor to measure refractive indices of unknown solutions. The surface plasmon sensor, interrogated with white light resulted in attenuations of light at different wavelengths when solutions of different refractive indices were introduced. This sensor has been shown to respond to the three configurations of polished single mode and multimode, as well as the unpolished multimode sensors. The sensitivity calculated was comparable with the sensitivity of the Kretschmann arrangement The transmissive aluminum-clad fiber sensor was shown to be effective in providing a response to the process of corrosion. Varying lengths of aluminum-clad fiber was spliced to acrylate multimode fiber and different wavelengths of sources were used to test the sensor in a bath of NaOH. The results were similar and reproducible. A tapered sensor configuration was attempted and proved to be very useful. / Master of Science

Since the recent discovery of a new class of high critical temperature superconductors (HTS), much interest has been shown in their potential use as optical detectors. The purpose of this research was to test thin film samples of the HTS Y1Ba2Cu3O7-delta as detectors and investigate any response to optical radiation. A laboratory test facility was designed and built for this purpose. The experimental results exhibit a variety of optical responses that are dependent upon the physical characteristics of each HTS thin film. Polycrystalline films exhibited a different detection mode than did epitaxial films. This research demonstrates that HTS thin films are viable optical detectors and have the potential to become competitive high-performance detectors as the new technology continues to emerge.

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The need for absolute radiometric calibration of space-based sensors will continue to increase as new generations of space sensors are developed. A reflectance-based in-flight calibration procedure is used to determine the radiance reaching the entrance pupil of the sensor. This procedure uses ground-based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of five calibrations of the Landsat-5 Thematic Mapper (TM). For the 12 measurements made in TM bands 1-3, the RMS variation from the mean as a percentage of the mean is (+OR-) 1.9%, and for measurements in the IR, TM bands 4,5, and 7, the value is (+OR-) 3.4%. The RMS variation for all 23 measurements is (+OR-) 2.8%. The absolute calibration techniques were put to another test with a series of three calibration of the SPOT-1 High Resolution Visible, (HRV), sensors. The ratio, HRV-2/HRV-1, of absolute calibration coefficients compared very well with ratios of histogrammed data obtained when the cameras simultaneously imaged the same ground site. Bands PA, B1 and B3 agreed to within 3%, while band B2 showed a 7% difference. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft-based radiometer data. This procedure was applied on four dates with two different surface conditions per date. A strong correlation, R('2) = .996, was shown between reflectance values determined from satellite imagery and low-flying aircraft data. Of the 32 predicted reflectance values only six had a difference greater than 0.01. A mean difference of .0007 was obtained for the 32 cases. In addition, a procedure had to be developed to obtain uncorrected digital counts from processed satellite imagery.

This thesis investigates the use of an avalanche Platinum Silicide (PtSi) Schottky Barrier Diode as a detector in fiber optic communication systems for the 1.3 to 1.5 mum spectral region. The avalanche process is used to amplify the signal prior to electrical interfacing in order to enhance the signal-to-noise ratio. The amount of multiplication is predicted by the impact ionization coefficients for electrons and holes, alpha and beta, respectively. By using PtSi Schottky diodes, where alpha > beta, pure electron injection can be accomplished by irradiating with photons of energy psi hnu Eg (where psi is the Schottky Barrier height and Eg is the bandgap of silicon), thus maximizing multiplication and minimizing noise. An alternative means for avalanching involves the quantum effects of impurity-band ionization. By using a heavily doped semiconductor and operating at low temperatures, one can achieve noise-free gain at lower electric field strengths. (Abstract shortened with permission of author.)

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