Optical beam induced current mapping has found wide-spread applications in charactering semiconductor devices and integrated circuitry. Conventionally a focused cw laser beam is employed to excite carriers in the depletion region that is subsequently detected to form the contrast signal for scanning imaging. Device defects that may quench the photo-generated carriers can then be easily revealed. However, such detection is static in nature and the dynamics behavior of a device remains unknown. In this study, we are using a pulsed laser with high repetition rate and a high frequency phase sensitive lock-in loop to achieve temporal resolution at sub-nanosecond. In this way, the temporal response at a selected position on the device can be characterized

As the great studies have been made in light emitting diodes, the application becomes more variety for different field. High bright light emitting diodes apply a new light source for fluorescence lifetime measurements. We use confocal scanning microscopy and a high frequency sensitive lock-in amplifier to obtain the electroluminescence image at ten of micrometer. We drive the light emitting diodes by radio frequency signal and observe it. We parallel connection an inductance to match the parasitic capacity in high frequency to obtain better light emitted brightness.

No description available.

Chromium doped crystals exhibit different emitting properties for their different valance species and the host crystals. Ruby shows narrow twin peaks around 694 nm for its Cr3+ ions. Cr4+:YAG has a broadband luminescence range on 1.1~1.6£gm, which is suitable for optical communication. The thesis aims to study the luminescent spectra of Cr ions in different crystal structure (Al2O3 and YAG). Cr concentration dependent spectra indicate Cr3+ moving toward the octahedron sites. It results the change of luminescent spectra and luminescent decay lifetime. Both FTIR and confocal microscopy are used for the investigations. Step-scan FTIR provides the relation of luminescence intensity relating to both wavenumber and delay time, of the external light source.The high numerical aperture optics in the confocal microscope provides higher collection efficiency, and results a better S/N ratio. In addition, Raman spectra are measured. Ruby and sapphire crystals exhibit different Raman spectra, which results from the electronic resonance of the Cr3+ ions in the ruby crystal.

Lung cancer is the leading cause of death from cancer in Canada and is typically treated with surgical resection of the tumor. To ensure good prognosis and limit metastases no cancer cells can be left behind during resection. This project uses time-resolved fluorescence and diffuse reflectance to differentiate cancerous and non-cancerous lung tissue. These differences could be used during surgical resection of tumor to ensure no positive margins are present. Using a bi-modal spectroscopy device, BEAR, optical properties were determined for 36 tumor, 36 fibrotic and 9 normal lung tissue samples. Most optical parameters showed statistically significant differences between tumor and other tissue types. Metabolic based optical parameters showed statistically significant differences between fibrotic and normal tissue while non-metabolic based parameters showed no difference. As surgical margins are likely to be between tumor and fibrotic tissue the results demonstrate success and promise for implementing this system. Future work using fresh samples would develop the system further and would be a step closer to in vivo use during surgery. / Thesis / Master of Science (MSc) / Lung cancer is the leading cause of death from cancer and is typically treated by surgically removing the tumor. To improve survival all cancer cells must be removed which can be challenging. This project uses light to extract properties that can differentiate cancerous and non-cancerous lung tissue. These differences could be used during surgery to ensure no cancer cells remain. The project tests this system on 36 tumor, 36 fibrotic and 9 normal lung tissue samples. Most parameters showed significant differences between tumor and other tissue types. Given that often times the surgical boundaries are between tumor and fibrotic tissue the results demonstrate promise in implementing this system. Future work using fresh samples would develop the system further and bring it one step closer to being used during surgery.

<p>In this thesis time-resolved photoluminescence spectroscopyis presented as a powerful tool to study the carrier dynamicsin various self-assembled quantum dot (QD) structures, whichare potentially attractive for device applications.</p><p>The experiments reveal the impact of proton irradiation onInGaAs QDs and comparable quantum wells. Nonradiativerecombination at defects–an important material parameterand“measure”of the structure optical quality–is found to play a much less important role for the QD samples.The superior radiation hardness can be explained as a result ofthe three-dimensional carrier confinement in QDs. Comparisonsbetween the structures show a decrease of photoluminescenceintensity for quantum wells but a slight increase for QDsirradiated at low to intermediate doses. This somewhatunexpected characteristic is described by an enhanced carriertransfer into the dots via the defects introduced in thematerial by the protons.</p><p>In a different structure carrier dynamics in spatiallyaligned of InAs QDs are investigated. Alignment along lines isachieved by misfit dislocations deliberately introduced in thesubstrate. Photoluminescence spectra of the dots exhibit muchsmaller inhomogeneous broadening than for the reference sampleas a result of an improved QD uniformity. Samples with varyingbuffer layer thicknesses were grown to study the influence ofdislocation related traps on the observed fastphotoluminescence decay. It is found that the fast carriertrapping is predominantly caused by point defects close to theQDs or at the QD/barrier interfaces.</p><p>Additional numerical simulations confirm the roles of thetwo independently acting traps in nonradiativerecombination.</p>

No description available.

Time-resolved electroluminescence has been primarily and widely applied in the field of optoelectronic devices and phosphor materials. Here we use the method to measure the response time and phase difference of green light-emitting diode. In our experiment, which is essentially dominated by pulsed signal from function generator¡Bhigh spatial resolution from laser scanning microscopic and phase-lock characteristic from lock-in amplifier to complete our experimental result. We are capable to detect relative carrier information within any point or any surface region from epi-layer of green light-emitting diode. Otherwise, the carrier transport of the sample is able to be observed through time-resolved characteristic measurement. Laser cutting would be beneficial for obvious phase-difference observation and mobility acquirement.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Two families of amphiphilic polymers were characterized with respect to their ability to respond to changing solution conditions using steady-state and time-resolved fluorescence. Firstly, a series of 5 sequential amphiphilic polypeptides consisting of hydrophilic and ionizable aspartic acid (Asp) and hydrophobic phenylalanine (Phe) in varying sequence (AspxPhey)n were studied. The effect of pH on the collapse and aggregation behaviour of the samples was investigated using light scattering which determined that the samples became insoluble when the fraction of ionized amino acids decreased below 0.2. Pyrene fluorescence measurments demonstrated that hydrophobic aggregate formation was the cause of this behaviour. The fluorescence and light scattering experiments yielded a detailed description of how pH affects the collapse and aggregation behaviour of amphiphilic polypeptides. Secondly, a series of poly(N-isopropylacrylamide) chains in aqueous solution, varying in length and end-labelled with pyrene (Py2-PNIPAM), were studied with respect to their temperature dependent solubility using turbidimetry, light scattering, and fluorescence. The cloud point temperature (Tc) of the Py2-PNIPAM samples was found to increase with increasing chain length. Steady-state fluorescence spectra yielded the ratio of excimer intensity to that of monomer intensity, or (IE/IM)SS, which reached a maximum at Tc. Time-resolved fluorescence decays were analyzed using Model-Free Analysis (MFA). The MFA yielded the average rate constant of excimer formation <k>, and the parameters fagg, fdiff and ffree, which reflect the molar fractions of pyrenes that form excimer from pre-formed aggregates, form excimer by diffusion, and do not form excimer, respectively. Increasing the temperature above Tc caused a strong decrease in <k> and ffree, and a sharp rise in fdiff, which is consistent with the formation of mesoglobules. Increasing the temperature above the dehydration temperature of unlabelled PNIPAM (Tm = 34 oC) caused the distribution of pyrene to stabilize. The third study focused on aqueous mixtures of Py2-PNIPAM and unlabelled PNIPAM, and their ability to mix when the temperature was raised above Tm. Using turbidimetry, separate transitions for Py2-PNIPAM and unlabelled PNIPAM were identified. Steady-state fluorescence of the labelled chains demonstrated separate (IE/IM)SS transitions for the labelled and unlabelled chains as well. The MFA of the time-resolved fluorescence decays yielded no transition in <k> at Tm, while fagg, fdiff and ffree showed transitions consistent with unlabelled PNIPAM entering the Py2-PNIPAM mesoglobules. This led to the conclusion that the two polymers are able to mix at and above Tm, and that the mesoglobules are not frozen and vitreous. Fourthly, a variety of pyrene-labelled polymers in organic solution were studied using steady-state and time-resolved fluorescence, where the results of Birks’ Scheme and the Fluorescence Blob Model (FBM) were compared to the results of the MFA. The MFA was found to be able to faithfully reproduce the results of the other, more established, models. In addition, the MFA allowed the calculation of (IE/IM)SPC, the ratio of excimer to monomer intensity as determined by time-resolved fluorescence, which scaled linearly with both (IE/IM)SS and <k>. From this it was concluded that the MFA is able to fit the decays of pyrene-labelled polymers with any architecture studied thus far, but also provides an absolute measure of IE/IM which can be reproduced in any lab.