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<td><img alt="Dissertation Defense Announcement at the Cullen College of Engineering" width="600" height="171" src="https://www.egr.uh.edu/sites/www.egr.uh.edu/files/enews/2022/images/dissertation1.png">
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<div style="font-size:24px; color:rgb(200,16,46); line-height:28px"><strong>Single-Crystalline III-N Film Growth for Photonic, Electronic, Sensing, and Energy Harvesting Applications</strong></div>
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<div style="font-size:18px; margin-bottom:5px"><strong>Mina Moradnia</strong></div>
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November 6, 2022; 2:00 PM - 4:00 PM (CST)<br>
<span style="color:rgb(34,34,34)">Location: Mechanical Engineering Conference Room (Eng 1, #202)</span> <br>
Zoom: <a href="https://urldefense.com/v3/__https://uh-edu-cougarnet.zoom.us/j/91234970981?pwd=Y3gzZXEyMkxsTlJjN29Ic2VnNm1DUT09__;!!LkSTlj0I!FBF32DGHzLDtQCcjX9vXAlO_J_EZnSO46inWdP4wOumZdENzzc2PysoneIocfAADDdgFddwoS1MDz0rPwV5GmLfx$" data-auth="NotApplicable" style="font-size:small; text-align:start">https://uh-edu-cougarnet.zoom.us/j/91234970981?pwd=Y3gzZXEyMkxsTlJjN29Ic2VnNm1DUT09</a></p>
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<strong>Committee Chair:</strong><br>
Jae-Hyun Ryou, Ph.D.</p>
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<strong>Committee Members:</strong><br>
Haleh Ardebili, Ph.D. | Jiming Bao, Ph.D. | Rebecca Forrest, Ph.D. | Tian Chen, Ph.D.</p>
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<strong>Abstract</strong></p>
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<font face="arial, sans-serif" size="2" style=""><span style="background-image:initial; background-position:initial; background-size:initial; background-repeat:initial; background-origin:initial; background-clip:initial">The flexible platform will be the next
generation of electronic devices for the growing demand of the industry. </span><span style="text-align:start">Current flexible devices are made by the deposition of non-single-crystal thin films on flexible substrates or by the layer transfer of single-crystal
thin films onto secondary flexible substrates, which result in low performance devices or complicated fabrication processes, respectively. We develop a process for direct deposition of single-crystal-like semiconductor films on flexible substrates to achieve
high-performance flexible devices using simple fabrication processes. For the transfer-free direct deposition of flexible III-N films, we demonstrated high-crystalline-quality aluminum nitride (AlN) and gallium nitride (GaN) on a flexible copper (Cu) foil/tape
using graphene as an intermediate seed layer. Graphene and AlN were directly grown by chemical vapor deposition and DC reactive magnetron sputtering, respectively, to achieve a highly-textured AlN film in both <i>a</i>- and <i>c</i>-crystallographic directions.
Then, a single-crystal-like GaN layer was grown by metalorganic chemical vapor deposition (MOCVD) on the AlN buffer layer. The proposed method enables continuous roll-to-roll process for device fabrication, bringing economic advantages to the semiconductor
technology with low-cost and large-scale </span><span style="text-align:start">manufacturing capability. In addition, </span><span style="text-align:start">group IIIa-N materials, such as AlN and GaN thin films, draw increasing attention in piezoelectric applications
due to their exceptional properties of high-temperature stability, spontaneous electric polarization, low dielectric permittivity, high sound velocity, efficient transduction, and high stiffness</span><span style="text-align:start">. However, the piezoelectric
coefficients and the resulting electromechanical coupling factors (<i>k<sub>t</sub></i><sup>2</sup>) of III-N materials are relatively low as compared to those of currently dominant piezoelectric materials such as lead zirconate titanate</span><span style="text-align:start">. </span><span style="text-align:start">Transition-metal-alloyed
III-V nitride thin films cause significant impact on the enhancement of the piezoelectric properties in group-IIIa-N (III-N) films, such as wurtzite AlN, by group-IIIb transition metals. Therefore, we focus on a new <span style="background-image:initial; background-position:initial; background-size:initial; background-repeat:initial; background-origin:initial; background-clip:initial"></span><span style="color:rgb(34,34,34); background-image:initial; background-position:initial; background-size:initial; background-repeat:initial; background-origin:initial; background-clip:initial">Hybrid
Chemical Vapor (HybCVD) thin film growth method </span></span><span style="background-image:initial; background-position:initial; background-size:initial; background-repeat:initial; background-origin:initial; background-clip:initial"><span style="text-align:start">along
with theoretically study the thermodynamics of (1) precursor reaction chemistry and (2) solid-phase formation of ScAlN, YGaN, and YAlN in different parts of source zones and mixing/growth zone.</span><span style="text-align:start"> </span><span style="text-align:start">The
combination of MOCVD and HVPE growth methods simultaneously provides good control on the uniformity and quality of piezoelectric films based on transition-metal-alloyed III-N materials.</span></span></font></p>
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<td><img alt="Engineered For What's Next" width="600" height="82" src="https://www.egr.uh.edu/sites/www.egr.uh.edu/files/enews/2022/images/dissertation2.png"></td>
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