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Nanofabrication involves the fabrication of devices at the nanometer scale. In this work, we used nanofabrication to design and fabricate nanostructures of squares and hexagons of different spatial pitch and gap width in Gallium Arsenide (GaAs). These structures have a gap of 300nm, 400nm, and pitch of 900nm, 1000nm and 1100nm. The fabrication process involves solvent cleaning, deposition of silicon oxide, soft and hard bake, photolithography and development. Both wet and dry etching were used to fabricate the expected structures. Results from scanning electron microscopy (SEM) to examine the shapes of the fabricated arrays are presented in this study. By combining dry and wet etches, we obtained the desired shapes and depth of hexagons and squares with rounded edges. We report detailed fabrication processes and their corresponding results at each step.
In this work, we fabricated nano-arrays for high power antireflection applications using contact photolithography. Fortunately for the antireflection application, pattern periodicity is more important than obtaining the exact shape of the nanostructure. The fabricated structure, even though not the same as the original pattern, can still produce promising antireflection results. We have studied how the range of the distance between the mask and the photoresist affects the shapes of the produced patterns including holes, posts, and cones. The experimental results with different shapes and periodic patterns produced by different diffraction distances are explained with simulation results involving Fourier transformation and Fresnel diffraction of the mask patterns.
However, the morphology did not change. It was also observed that impurities such as magnesium oxide (MgO) affect the morphology significantly.
Plants exhibit complex responses to changes in environmental conditions such as radiant heat flux, water quality, airborne pollutants, soil contents. We seek to utilize the natural chemical and electrophysiological response of plants to develop novel plant-based sensor networks. Our present work focuses on plant responses to high-energy radiation – with the goal of monitoring natural plant responses for use as benchmarks for detection and dosimetry. For our study, we selected a plants cactus, Arabidopsis, Dwarf mango (pine), Euymus and Azela. We demonstrated that the ratio of Chlorophyll a to Chlorophyll b of the leaves has changed due to the exposure gradually come back to the normal stage after the radiation die.
We used blue laser-induced blue fluorescence-emission spectra to characterize the pigment status of the trees. Upon blue laser excitation (400 nm) leaves show a fluorescence emission in the red spectral region between 650 and 800nm (chlorophyll fluorescence with maxima near 690nm and 735 nm). Sample tree subjects were placed at a distance of 1m from NIST-certified 241AmBe neutron source (30 mCi), capable of producing a neutron field of about 13 mrem/h. This corresponds to an actual absorbed dose of ~ 1 mrad/h.
Our results shows that all plants are sensitive to nuclear radiation and some take longer time to recover and take less. We can use their characteristics to do differential detection and extract nuclear activity information out of measurement results avoid false alarms produced environmental changes. Certainly the ultimate verification can be obtained from genetic information, which only need to be done when we have seen noticeable changes on plant optical spectra, mechanical strength and electrical characteristics.
The measured results are processed in Fourier domain. The signal and noise spectra of the 4 microphone/4 reflector have a combined SNR of 11.48 dB, while the results of 16-microphones/1-reflector have a combined SNR of 17.82 dB. The worse SNR result of the 4-phone/4-reflector system may not simply due to the other system has more microphones. It also because of the average effect of the full reflector area, which can blur the phase of each element and the noise, cannot be cancelled more exactly.
28-dB gain mid-infrared optical amplification using resonant quantum cascade laser optical amplifier
The effect of contact resistance in a broadband semiconductor optical amplifier using SAG techniques
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