Browsing by Author "Lee, Mark"
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Item 0.3 THz CMOS Transceiver Pixels for Reflection Mode Active Imaging(December 2022) Byreddy, Pranith Reddy 1993-; Thuraisingham, Bhavani; O, Kenneth K.; Lee, Mark; Henderson, Rashaunda; Saquib, MohammadElectromagnetic waves at frequencies ranging from 0.1 to 10THz, commonly referred to as THz waves have a wide variety of medical, security and industrial imaging applications. However, generation and detection of signals at these frequencies are quite challenging. The complementary metal-oxide semiconductor (CMOS) technology which is widely used in most of the modern consumer electronic devices is an affordable means for generation and detection of THz signals. Near-millimeter-wave and terahertz imagers are expected to complement visible light, IR, Radar and Light Detection and Ranging (LiDAR) imaging by providing a unique combination of angular resolution and a capability to image in visibly impaired conditions such as fog, rain and dust as well as for imaging through other materials. This research aims at the design of concurrent transceiver pixels operating at frequencies around 300GHz for reflection mode active imaging using a CMOS process technology. A 7-element array of 287-GHz CMOS transceiver pixels with pixel area smaller than (λ/2)2 housed in a QFN package is demonstrated. Each pixel concurrently performs transmission and coherent detection using a push-push VCO, that functions as a 287-GHz transmitter, a 143-GHz LO, and a sub-harmonic mixer at the same time. An effective isotropic radiated power (EIRP) of −2.5dBm and sensitivity of −88dBm for 1-kHz noise bandwidth are achieved. Link budget analyses suggest that it should be possible to perform reflection-mode active imaging at 10 m using the array, and a reflector with a diameter of 15-cm and a simulated near-field gain of 44.6dB. The packaged array exhibits a 2.5-dB higher EIRP and a 3-dB lower noise figure than the array without QFN packaging due to the antenna performance enhancement. This demonstrates that it is possible to package 300- GHz integrated circuits with an on-chip patch antenna using a low-cost technique. Lens-less short-range reflection-mode imaging through cardboard is demonstrated at 275GHz using a pair of concurrent CMOS transceiver pixels separated by ~5mm on a PCB. An isolation study employing EM simulations is performed to quantify the unwanted coupling. This is first such demonstration at frequencies above 100GHz. The separation between the imaged object and pixels is ~1cm and the operation at 275GHz allows the lateral resolution to be reduced to ~2mm due to a smaller wavelength. This pixel achieves an EIRP of -18.9dBm and a double-sided noise figure (NFDSB) of ~51dB in an area of 0.45×0.49 mm2. An 1x3 array of 296-GHz CMOS concurrent transceiver pixels incorporating circuits for baseband signal extraction in addition to the RF section in an area of (λ/2)2 is demonstrated. The EIRP of array is ~-6dBm and NFDSB is ~48dB. An E-shaped patch antenna to broaden the antenna bandwidth is used. Using a pair of these arrays, lens-less short-range reflection-mode imaging of a target ~1cm away through a cardboard is demonstrated. More importantly, use of the arrays improves isolation between the pair by ~10 dB to ~70 dB compared to that when single pixels are used. This work points to a path for incorporation of millimeter and sub-millimeter wave imaging capabilities in a handheld device.Item Complex Permittivity of Advanced Dielectrics Across the 6G Frequency Band(2022-08-01T05:00:00.000Z) Mcgarry, Michael Patrick; Lee, Mark; Smaldone, Ronald; Henderson, Rashaunda; King, Lindsay J.; Glosser, RobertAs industry moves to higher frequencies with the use of 5G telecommunication (up to 38 GHz) and automotive radar (up to 77 GHz), electrical characteristics for a wide range of materials are needed. To potentially employ these materials with millimeter-wave ICs (MMICs), quantitative knowledge of the materials’ dielectric properties across a broad millimeter-wave band is necessary. To solve this, we created a nondestructive measurement of the complex relative permittivity, εr = ε′ + jε′′, on some possible MMIC packaging materials, ranging from epoxy composites to liquid crystal polymers as well as laminates and bond plys. Measurements using phase-sensitive transmission over the WR3, WR5, and WR8 frequency bands (90 to 325 GHz) show that ε′ can vary significantly in traditional packaging materials. For example, a known material at low frequencies, Vectra A130, is shown to be dispersive at high frequencies with a slope of 0.17%/GHz. Thus, across the WR5 band the ε′ changes from about 1.95 at 140 GHz to about 2.8 at 220 GHz. Results like this could be used to model the performance of packaged MMICs in HFSS and to design composites or other types of MMIC packaging material to have tailored values of ε′ and in the loss tangent for better system results. As an example of modeling, electromagnetic modeling results for an in-package horn antenna molded from one of the dielectric composites measured are presented.Item Coupling of Ionic and Electronic Processes in Lead Halide Perovskite Devices and Nanostructures(2021-12-01T06:00:00.000Z) Haroldson, Ross Everett; Zakhidov, Anvar; Cao, Yan; Gartstein, Yuri; Lee, Mark; Slinker, Jason; Stefan, MihaelaLead Halide Perovskites (LHPs) such as Methylammonium Lead Iodide (MAPbI3) or Cesium Lead Bromide (CsPbBr3) have garnered massive attention from researchers in photovoltaic, light emitting, and other optoelectronic fields as an interesting class of materials with attractive semiconducting and optical properties. Fabrication processes of LHPs are relatively simple compared to conventional inorganic semiconductors and don’t require powerful or expensive equipment which is promising for commercial development. However, they have shown dynamic performance behaviors and instabilities that have yet to be fully understood. These dynamic behaviors on the time scale of seconds have been attributed to their mobile charged point defects redistributing themselves during device operation. The ions (or charged defects) act as mobile intrinsic donors and acceptors that can be utilized in device operations. This thesis discusses the physical origin that strongly couples the electronic and ionic transport of LHPs and demonstrates devices that exploit and utilize this coupling. This coupling enables the dual functionality of mixed halide solar cells to also act as effective light emitting devices. We also demonstrate that utilizing extrinsic ionic salts such as lithium hexafluorophosphate (LiPF6) can serve as sacrificial ions that help protect the bulk of the perovskite from fast degradation. We studied the dynamic performance of LHP optoelectronic devices configured as perovskite lightemitting electrochemical cells (PeLECs) under various temperatures and conditions. We develop novel equivalent circuit models to extract the diffusion coefficients and concentrations of dominant ionic species at play in PeLEC devices in vacuum and dry air, in the dark or under illumination, and at different temperatures. Activation energies of ionic species in PeLECs were calculated by the temperature dependence of fitted parameters from diffusion elements in the equivalent circuits used to model impedance spectroscopy measurements. This thesis advances the knowledge and understanding of ion migration (or charged point defect transport) in LHP devices and how it affects their performance.Item Design and Applications of Nanoscale Light Sources(2022-08-01T05:00:00.000Z) Li, Xi; Gu, Qing; Ng, Vincent; Henderson, Rashaunda; Lee, Mark; Friedman, JosephFast and efficient nanoscale light sources are at the heart of on-chip optical communication and computation systems. With the rapid development of advanced fabrication techniques and the use of metal in cavity designs, light confinement, and manipulation at the nanoscale, far below the diffraction limit of light, have become possible. Over the years, various nanoscale lasers and LEDs have been analytically or experimentally demonstrated. From the modulation bandwidth perspective, nanolasers are ultimately limited by gain compression at high injection currents. From the energy efficiency perspective, nanolasers are inefficient due to the required high injection current to reach the lasing threshold. In contrast, nanoLEDs can simultaneously support large modulation bandwidth due to the Purcell effect, and high energy efficiency because they can be operated at low injection currents without the need to reach the lasing threshold. This dissertation is focused on the design and applications of nanoscale light sources towards the realization of nanoLEDs that can support high speed modulation and efficient operation. Firstly, we present an optically pumped version of a shifted-core coaxial nanoLED, with a footprint of merely 1/3 of its emission wavelength in all three dimensions at telecommunication wavelengths. By shifting the metallic core off the center of the coaxial cavity, the effective mode volume can be reduced to 0.0078×(λ0/na)3, resulting in a Purcell factor over 390 and a modulation bandwidth exceeding 60 GHz. Furthermore, this nano-emitter features improved emission directivity, which increases its coupling efficiency to an on-chip waveguide. As this nano-emitter supports only one TEM-like mode over the entire material gain spectrum, the spontaneous emission factor becomes close to unity, which greatly improves its internal quantum efficiency. In order to calculate the Purcell factor precisely, we exhaustively studied the effective modal volume, Veff. We found that for cavities with poor confinement and low quality factors, the choice of a correct field normalization method is crucial to adequately describe the diverging behavior of the cavity’s effective modal volume. Secondly, we present the design of an electrically pumped shifted-core coaxial nanoLED. We design the multiple quantum well III-V gain material to achieve high internal quantum efficiency and an impedance transformer to improve the injection efficiency into the nanoLED. Lastly, we propose a biochemical sensor based on plasmonic nanofocusing phenomenon in a pair of coupled shifted-core coaxial nano-cavities. By placing a fluidic channel between the two cavities in close vicinity to the hotspots created by the coupled modes, the sensitivity of this biochemical sensor can be greatly enhanced. In our simulation, this biochemical sensor shows an ultra-high sensitivity up to 1.5179×104 nm/RIU.Item Electrodynamic Response of Advanced Dielectric Materials in Broadband Frequency Range(2018-08) Motaharifar, Elaheh; Lee, MarkReliable index or permittivity data over a broad THz frequency range is challenging to find in the existing literature for many dielectric materials commonly used in the electronics industry. In this work, two classes of dielectric material characterization techniques are introduced for different dielectric polymeric materials and a high quality single crystal perovskite to expand the current knowledge on their potential electrical or opto-electronics applications in THz frequency range. First, the non-magnetic polymeric dielectric materials measurements were made using a Fourier Transform Infrared Spectrometer from 3-75 THz. Two different analyses models were used to investigate material’s properties according to the experimental data. The first model, offresonance model, used where experimental data showed non-resonance response for materials exposing to the external electric field. In contrast, on or near lattice vibration or molecular bond resonances, the attenuation or loss of material can become large enough to cause no transmission through the sample. When this occurs, we used a resonance model in the presence of resonances where the frequency of applied electric field matches with the intrinsic frequency of atoms or molecules in materials. A high quality single crystal of Methylammonium Lead Bromide perovskite also used inside FTS and the reflection and transmission measurements were done. The experimental data showed a sharp reflectance near 1.35 THz, indicating of an isolated optical phonon reststrahlen band. It also showed another reststrahlen band arising from two overlapping optical phonon modes. In the frequency regions where fall into reststrahlen bands, the real part of permittivity has an anomalous value since there is no propagating electromagnetic wave inside the material. In contrast, in the frequencies higher than 12 THz we just saw localized molecular bond resonances and no reststrahlen band observed. The other technique we introduced was a quasi-optical millimeter-wave spectrometer for magnetic and non-magnetic material characterization. We used a high resistivity silicon to investigate and confirm the accuracy of the experimental model along with the analysis model to extract permittivity and permeability of the materials.Item Explicitly Quantum Mechanical Silicon Complementary-Metal-Oxide Semiconductor Devices(2019-05) Hu, Gangyi; 0000-0002-6253-8426 (Hu, G); Lee, MarkEnormous growth in silicon large scale integrated circuits (IC) has been accelerated by reducing the size of their fundamental elements such as complementary-metal-oxide-semiconductor (CMOS) transistors over the past fifty years. Quantum effects will become extremely important when the device length scale becomes smaller than the mean free path of an electron in the conduction band, which is close to scale of hundreds of silicon atoms, approaching the limit of Moore’s law. Quantum transport demonstrated as negative differential transconductance (NDTC) has been discovered in quantum well (QW) n-channel metaloxide-semiconductor (NMOS) transistors fabricated on an industrial 45 nm technology node silicon CMOS process line. NDTC regimes provide a new current-voltage transfer function that was exploited to build a folding frequency multiplier circuit using only one single QW NMOS transistor, resulting in significant circuit simplification and quiescent power reduction. Intrinsic gain measurements on silicon QW NMOS transistors show that these devices can have negative gain with magnitude up to 2.5 at room temperature, which is the prerequisite to build amplifier and oscillator applications. With the downsizing of silicon devices, a single defect inside a device such as a trap at the Si/SiO₂ interface of a CMOS transistor, plays a more and more important role in reducing device stability and limiting device sensitivity. The random telegraph signal (RTS) noise that is generated by random capture and emission of charge carriers in the inversion channel by static traps, has been observed in the source-drain current of silicon quantum mechanical NMOS transistors with current fluctuation up to 76%. Most interestingly, the switching rate of RTS gradually diminished to zero at 15 K over time scale of one to two hours, while keeping the current fluctuation stable. This decay in the switching rate may be due to a metastable oxygen vacancy defect that gradually repairs itself after repeated capture and emission of charge, deactivating the trap defect, suggesting a mechanism to eliminate at least some forms of RTS through a “cryogenic anneal”. As silicon devices are scaled down, it may become possible to build silicon thermoelectric generators (TEGs) using silicon nanowires (NW) or other forms of nanostructured silicon because of a potential large reduction in the phonon contribution to thermal conductivity, resulting in a large figure-of-merit (ZT) two orders-of-magnitude greater than bulk silicon. TEGs can recycle waste heat into electrical power, have applications ranging from on-chip thermal management embedded into ICs to environmental energy sources for low-power microsensors in the Internet-of-Thins (IoT). Very high specific power generation capacity up to 29 µW·cm⁻²K⁻², which compares favorably to that of (Bi,Sb)₂(Se,Te)₃ based TEGs, has been observed in silicon NW TEGs fabricated on an industrial 65 nm technology node silicon CMOS process line. This high specific power capacity results from the ability of CMOS processing to fabricate a very high areal density of thermocouples while keeping packing fraction low and to control parasitic electrical and thermal impedances. These silicon TEGs can be seamlessly integrated with commercial scale silicon CMOS microelectronic circuits at very low marginal cost.Item Integrated Circuit "Astrolabe" Angular Displacement Sensor Using On-Chip Pinhole Optics(2020-11-30) Wijesinghe, Udumbara C; Lee, MarkAn integrated circuit sensor capable of tracking the angular displacement of an object tagged with a quasi-point source of light, such as a light emitting diode (LED), is designed, developed, experimentally characterized and physically modeled. The sensing element consists of four photocathodes enclosed inside an integrated circuit metal box with a pinhole aperture, which eliminates the need for external focusing optics. The angular displacement of an LED along both orthogonal latitudinal and longitudinal arcs is encoded as normalized photo-cathode current imbalances. A set prototype sensor including variations in aperture shape, aperture dimension, cathode separation, surface gratings, and blocking structures were fabricated using industrially standard “0.18 µm technology node” silicon complementary metal-oxide semiconductor (CMOS) technology. In these prototype sensors, the sensor signal is found to be linearly proportional to LED angular position across an approximately ± 50° field-of-view. A simple one-dimensional model of sensor response is developed, and the fundamental performance characteristics of prototype sensors are presented. A figure-of-merit is introduced that helps determine the uncertainty in angular measurement for a given measurement bandwidth and incident optical power. In these prototype astrolabes, the amplified signal figure-of-merit roughly a factor of 10 worse than needed to be practically useful. Based on the results of the prototype sensors, a wide range of improved second-generation sensor layout variations was designed, fabricated, and experimentally tested. Second-generation astrolabe variations included, anode gratings, guard rings, aperture area variations, cathode separation variations, cathode type variations, unit cell dimension variations and some sensors had integrated on-chip preamplifiers. The improved features and their impact on sensor characteristics are presented. More advanced physics-based 1-d and 2-d theoretical models have been derived in order to understand the operating principles of the sensor thoroughly. Numerical technology computeraided design (TCAD) models of the type used widely in the semiconductor industry have been used to simulate the device physics of the sensors. The figure-of-merit obtained from the unamplified signals of the second generation astrolabes is three times better than that of the prototype sensors. However, second generation sensors show only 30% improvement with signal amplification compared to the 85% improvement resulted from the sensor first generation. Possible noise sources that could affect the sensor performance have been studied, modeled and a new measurement setup is proposed to track the angular position of a moving object in real time.Item Microwave Conductance of Aligned Multiwall Carbon Nanotube Textile Sheets(2014-12-30) Brown, Brian L.; Bykova, Julia S.; Howard, Austin R.; Zakhidov, Anvar A.; Shaner, Eric A.; Lee, Mark; Brown, Brian L.; Bykova, Julia S.; Howard, Austin R.; Zakhidov, Anvar A.; Lee, MarkMultiwall carbon nanotube (MWNT) sheets are a class of nanomaterial-based multifunctional textile with potentially useful microwave properties. To understand better the microwave electrodynamics, complex AC conductance measurements from 0.01 to 50 GHz were made on sheets of highly aligned MWNTs with the alignment texture both parallel and perpendicular to the microwave electric field polarization. In both orientations, the AC conductance is modeled to first order by a parallel frequency-independent conductance and capacitance with no inductive contribution. This is consistent with low-frequency diffusive Drude AC conduction up to 50 GHz, in contrast to the "universal disorder" AC conduction reported in many types of single-wall nanotube materials.Item Millimeter-wave Packaging Materials and CPW Interconnects on Silicon(August 2022) Mahjabeen, Nikita; Henderson, Rashaunda; Bastani, Farokh; O, Kenneth K.; Blanchard, Andrew J.; Lee, MarkAccurate millimeter wave (mm-wave) circuit and system design is challenging due to un- known dielectric properties above 40 GHz, higher loss due to multimode propagation in substrates, and electromagnetic modeling limitations when compared with on-wafer mea- surement. This dissertation attempts to address these challenges by studying material char- acterization techniques and coplanar waveguide (CPW) line performance on silicon wafers. The dielectric characterization techniques have been investigated from 10 MHz to 110 GHz for substrates and fixed thickness packaging dielectrics. Broadband data using a coaxial line technique was demonstrated for the first time in literature up to 67 GHz. The accuracy of the properties improves for material thicknesses which are greater than half wavelength. For the thin samples, a stacking technique has been introduced to electrically increase the thickness. The broadband data was achieved using a single 1.85 mm airline from 10 MHz to 67 GHz, followed by a WR10 waveguide from 75 to 110 GHz. As resonant techniques are more accu- rate, a microstrip ring resonator was used where the copper trace was printed using a craft cutter tool and was adhered onto non-copper clad materials. This is a fast, low-cost, and non-destructive solution and is suitable for frequencies below 20 GHz. This study will en- able high frequency design solutions for packaging technologies used for antennas-in-package (AiP) and three dimensional (3D) printed RF circuits. Next, broadband loss characterization of coplanar waveguide (CPW) transmission lines has been studied on undoped high resistivity silicon (HRS) from 10 MHz to 325 GHz. Electromagnetic (EM) modeling limi- tations in the Ansys HFSS simulation tool have been examined for full thickness wafers of 525μm and two innovative EM ports were introduced. The bridge-probe lumped port model showed promising results to address the probe parasitics at high frequency. The tunnel wave- port showed simulation capability up to 325 GHz which otherwise would be limited to 80 GHz using general waveport for 400 μm thick substrates. The on-wafer measurement data shows that unwrapped ground, narrow ground width and thinning of substrates can reduce the loss of the lines. A glass spacer was used to separate the wafer from the probe station chuck. Compared to simulation, higher loss was observed in the measured data up to 110 GHz due to a possible unavoidable parasitic surface channel in silicon. This problem can be mitigated by surface passivating the silicon. At frequencies from 140 to 325 GHz, this issue was not observed. The loss of the conventional CPW lines has been used as a baseline to characterize the performance of copper nanowire interconnect technology integrated within the lines. This work can contribute to the advancement of copper-to-copper interconnects for die-to-wafer or wafer-to-wafer connections for 3D packaging technology. The potential of HRS for passive device design was further explored by introducing short and open stubs on the center conductor of CPW lines as filter elements operating up to 325 GHz which showed excellent response compared with simulation.Item Millimeter-wave Wideband MSK Receiver and Transmitter in CMOS(2021-05-01T05:00:00.000Z) Dong, Shenggang; O, Kenneth K; Desmedt, Yvo; Henderson, Rashaunda; Lee, Mark; Fonseka, John PThe sub-terahertz portion of the electromagnetic spectrum can provide a large bandwidth for both wireless communication and wireline communication using dielectric waveguides. To fully exploit the bandwidth, the communication systems inevitably require frequency division multiplexing. Since integrating a highly frequency-selective multiplexer and a de-multiplexer is challenging at these frequencies, use of MSK (Minimum Shift Keying) modulation with reduced out-of-band emission is a potential approach to alleviate this technical challenge. Furthermore, MSK is a constant envelope modulation and allows more power efficient operation of transmitters. This is particularly important at sub-terahertz frequencies, where the power efficiency of circuits is low. Lastly, MSK signals can be demodulated using a phase locked loop (PLL) based receiver that tracks the carrier frequency of signals incident to a receiver, which greatly relaxes the frequency synchronization requirements in both transmitter and receiver. PLL-based receivers are also simple to implement. Although MSK signals have such merits for sub-THz communication, the previously reported carrier frequency of Gilbert-mixer-based MSK transmitters is lower than 60 GHz and data rate lower than 2 Gbps. The maximum data rate of PLL-based receivers is 10’s of Mbps. Increasing the data rate of PLL-based receiver and generation of high-data rate MSK signals are the main topics of this dissertation. First, a 180-GHz MSK receiver using a phase-locked loop (PLL), which self-synchronizes carrier frequency is demonstrated. The mixer first receiver is fabricated in a 65-nm CMOS process. A double balanced anti-parallel-diode-pair sub-harmonic mixer performs the phase detection, reducing the frequency of LO by half. Tunable zeros realized by series inductors are used to improve the stability and to increase the data rate handling capability. Without external LO synchronization, the receiver demodulates MSK signals at 10 Gbps with a bit error rate (BER) of < 10-12 and at the maximum data rate of 12.5 Gbps with a BER of 3.8×10-5 . The BER at 10 Gbps is the lowest and the data rate of 12.5 Gbps is the highest for PLL receivers. Second, high data rate 180-GHz MSK modulated signals for dielectric waveguide communication are generated using a transmitter fabricated in 65-nm CMOS. To accomplish this, techniques for controlling the relative phases of half-sine shaping signal and data, “Misaligned-to-Aligned” are proposed and demonstrated. Limited by the instrumentation for MSK signal analyses, the eyes of transmitted MSK signals have been verified for a data rate up to 10 Gbps. The MSK signal generator provides a 5X higher data rate among all the previously reported MSK transmitters at a 3X higher carrier frequency. Thirdly, a dual-band minimum shift keying (MSK) transmitter operating at 180 GHz and 315 GHz is demonstrated in 65-nm CMOS. The transmitter incorporates the data encoder and wideband I/Q phase alignment for MSK signal generation. Limited by the instrumentation for the MSK signal analyses, the 315-GHz channel is used to form a 10-Gbps link at BER= 5×10-5 with an on-chip PLL-based receiver. It has increased the highest carrier frequency of MSK signal generation from 180 GHz to 315 GHz. This work also demonstrates the first single-chip transmitter in CMOS that supports frequency division multiple access (FDMA) communication above 150 GHz.Item Negative Differential Transconductance in Silicon Quantum Well Metal-Oxide-Semiconductor Field Effect/Bipolar Hybrid Transistors(American Institute Of Physics Inc., 2014-11-25) Naquin, Clint; Lee, Mark; Edwards, H.; Mathur, G.; Chatterjee, T.; Maggio, K.Introducing explicit quantum transport into Si transistors in a manner amenable to industrial fabrication has proven challenging. Hybrid field-effect/bipolar Si transistors fabricated on an industrial 45 nm process line are shown to demonstrate explicit quantum transport signatures. These transistors incorporate a lateral ion implantation-defined quantum well (QW) whose potential depth is controlled by a gate voltage (VG). Quantum transport in the form of negative differential transconductance (NDTC) is observed to temperatures > 200 K. The NDTC is tied to a non-monotonic dependence of bipolar current gain on VG that reduces drain-source current through the QW. These devices establish the feasibility of exploiting quantum transport to transform the performance horizons of Si devices fabricated in an industrially scalable manner.Item Probing Dynamic Cellular Properties Using Genome Editing and Systems Biology(2021-12-01T06:00:00.000Z) Nowak, Chance Michael; Bleris, Leonidas; Lee, Mark; Palmer, Kelli; Kim, Tae Hoon; Campbell, ZacharyGenome editing has revolutionized not only the future of biological research, but also holds the promise of being a powerful therapeutic for genetic diseases. When considering the multitude of genetic regulations that contribute to various biological processes and their individual contributions that permit diseased cellular states, especially in instances where more than a single genetic aberration is attributed to the diseased phenotype, it is crucial to consider the interconnectivities of gene regulators and their individual contributions to cell health. Biological network maps that reveal the relation of gene products to one another can provide insight into the biological properties they govern. A biological network map consists of nodes (gene products) connected by edges that are dictated by the nature of the interaction between the two nodes. Nodal ablation (i.e., knocking out a gene to render it non-functional) has been crucial in understanding diseased states. However, this type of mutational analysis essentially disregards the impact that individual edges have on the network as a whole. The goal of my dissertation work was to utilize the genome editing tool Cas9 to disrupt the p53-miR-34a network in an edge-specific manner in order to demonstrate not only the complexity of these networks, but to also underscore the importance that individual edges have on the tumor suppressor phenotype. To this end, I, along with a team of researchers, developed a genetic screen using Cas9-bearing lentiviral vectors to disrupt 93 miR-34a binding sites within the 3’ untranslated region (UTR) of 71 genes impactful to cell survival under apoptotic conditions. I quantified the degree of apoptosis in two colorectal cancer cell lines that differ in functional p53 status, and that each harbored miR-34a binding site mutations within the pro-survival gene Bcl-2 3’UTR, demonstrating the importance of the miR-34a-Bcl-2 edge on apoptotic progression. Concurrently, I investigated the phenomenon of cell cycle desynchronization by tracking the DNA distribution of a population of cells starting from a synchronized state until asynchrony with flow cytometry analysis. In doing so, I utilized statistical tools to quantify the degree of desynchronization that does not rely on individual cell cycle phase labeling. Additionally, with the help of my peers, tested and validated a mathematical model the capitulates experimental observations. I explored the sensitivity of the model to changes in its parameters to reveal that cell cycle variability within the population is a main contributor to cell cycle desynchronization. Furthermore, I tested this model prediction by treating cells with lipopolysaccharide to enhance cellular noise, resulting in a greater variability of cell cycle duration, which was also shown to increase the rate of cell cycle desynchronization. Taken together, my research provides insight into the importance individual edges have to biological networks and their resulting phenotypes, as well as the underlying sources of cell population heterogeneity and its contribution to cell cycle variability.Item Silicon-based Thermoelectrics for Microelectronic Applications(2022-05-01T05:00:00.000Z) Dhawan, Ruchika; Lee, Mark; Dabkowski, Mieczyslaw; King, Lindsay J.; Slinker, Jason D.; Lv, Bing; Kolodrubetz, MichaelThe large advancement of miniature (∼0.1 cm2 area) silicon integrated circuit (IC) sensors and networking devices for internet-of-things (IoT) and biomedical electronics has prompted the problem of making such devices energy-autonomous, i.e., how to energize such devices reliably and sustainably when they are embedded in isolated environments that have no sunlight for photovoltaics, have no access to wall plug power, and cannot routinely be accessed for regular maintenance or battery replacement. Recently, significant interest has developed in small microelectronic thermoelectric generators (µTEGs) as an autonomous energy source for IoT and biomedical devices wherever a reliable thermal gradient exists. Miniaturized solid-state thermoelectric (TE) devices can interconvert thermal gradients and electric fields for power generation or refrigeration. Most current research on TE technology concentrates on developing new materials with high TE figure-of-merit ZT = α 2σ κ T, where α, κ, σ and T are the material’s Seebeck coefficient, thermal conductivity, electrical conductivity, and the mean operating temperature, because the ideal thermodynamic maximum efficiency of a TEG increases with the ZT of the materials used to form the thermopile. However, high ZT materials are usually toxic or non-earth abundant, expensive to manufacture, and are generally incompatible with the Si IC fabrication process, all of which can substantially increase the cost of integration with standard IC devices, making these materials inappropriate for large-scale integration. Bulk Si is neglected for TE applications because of its poor ZT ∼ 10−2 − 10−3 near room temperature due to its large thermal conductivity. Recently, new opportunities for TE materials have been created because of significant advances in the scientific understanding of nanostructure effects on TE properties. It is now thought to be possible to build nanostructured silicon TEGs with a large reduction in κ due to significant phonon scattering, thus enhancing the ZT of material. In this research, µTEGs with a small area (<< 1 mm2), using doped Si and Si0.97Ge0.03 as the TE material, are fabricated on a standard industrial Si IC process line following the same protocols and process flows used to make commercial IC devices. These µTEGs can generate very large specific power densities (power per unit area for heat flow per square of temperature difference, ∆T ) of 84 µWcm−2K−2, which is comparable to the best existing high ZT bulk TEGs. Moreover, these miniature Si µTEGs can generate voltages exceeding 1.5 V with several µA of current using commonly encountered ∆Ts ∼ 20 to 25 K, which are sufficient to properly energize some existing commercially available low-power IoT ICs. These µTEGs are compatible with industrial fabrication techniques so can be directly integrated on-chip in the same process flow with the circuits they support, providing one solution to energy autonomy at an extremely low marginal cost. These Si-based µTEGs build on an unconventional approach to µTEG device design that emphasizes the application of device physics and circuit engineering principles to optimize a µTEG’s generated power per unit area at any given ∆T, rather than focusing on the thermodynamic efficiency, for applications with a high specific power density as the primary requirement. Using the ability of CMOS processing to fabricate ultrahigh density devices with low packing fraction, we can integrate ∼ 104 thermocouples cm−2 while maintaining a reasonable temperature gradient across the device, thereby producing high total power and voltage density despite relatively low efficiency per TE element. Modern Si processing is also very good at controlling parasitic thermal and electrical resistances, thus minimizing extrinsic degradation of overall TEG performance. Experimental results on µTEG fundamental performance characteristics (i.e. power and voltage generation) as well as TE Peltier cooling are presented. For optimizing the performance of TEGs, Physics-based models at both the material level including the effects of dopant concentration and small percentage Ge alloying, and the device design level including effects of parasitic electrical and thermal resistances and proper design of thermopile packing fraction have been developed. These models help optimize the TEGs to provide maximum power production in future designs. The wide acceptance of TE technology in a broad range of IC applications demands not only the research on suitable TE materials but also understanding the device physics along with the ability to determine basic TE properties such as Seebeck (α) and Peltier (π) coefficients at the device level. A wide range of literature exists on measurement of α but π is rarely measured and is usually derived from α using the first Kelvin relation, π = αT. We have developed a new method for measuring π in any TE device using only standard measured device parameters (i.e thermal impedance and short circuit current) without the need to correct for Ohmic heating (I 2R) that has historically made reliable measurements of π difficult. The experimental verification of the first Kelvin relation is illustrated using the independently measured value of α and π on commercial TE materials.Item Terahertz Up-conversion Mixers Using Varactors in CMOS and Their Applications(2022-05-01T05:00:00.000Z) Chen, Zhiyu; O, Kenneth K.; Summers, Joshua; Henderson, Rashaunda M.; Lee, Mark; Saquib, MohammadWireless communication at frequencies above 100 GHz is drawing attention due to its high data rate capability resulting from the wide available bandwidth. The recent advances of the high frequency performance of complementary metal oxide semiconductor (CMOS) technology have made it an affordable way for implementing the wireless systems. In order to support high-order modulations to increase the data rate, and an increased range, the transmitter must have a high output 1-dB compression point (OP1dB) and a wide bandwidth. Since the transistor fmax in CMOS has peaked at ~350 GHz, it is challenging to implement 300-GHz transmitters in CMOS. Consequently, the performance of the last up-conversion mixer in a transmitter is a key factor determining its performance. A 300-GHz sub-harmonic up-conversion mixer using symmetric varactors (SVAR’s) is demonstrated. This mixer takes an IF signal centered at 150 GHz and up-converts to RF at 290 GHz with an LO of 70 GHz. Implemented in 65-nm CMOS, the mixer achieves the maximum conversion gain (CG) of -16 dB and OP1dB of -11.4 dB. The OP1dB when reported was more than 10 dB higher compared to that of the other CMOS sub-harmonic up-conversion mixers in the literature. Fundamental mixing has superior conversion efficiency and output power. To increase CG and OP1dB, a fundamental up-conversion mixer with a similar structure using asymmetric varactors (ASVAR’s) is demonstrated. Using a similar transformer-based hybrid structure, this mixer achieves measured CG of -12.5 dB. The OP1dB is greater than -2 dBm with LO power of 15 dBm at 140 GHz. Due to the imbalance, a -21-dBm leakage at 2fLO is presented at the output. To reduce the generation of unwanted harmonic terms, a double-balanced up-conversion mixer using ASVAR is demonstrated in 65-nm CMOS. It utilizes a power-splitting-transformer hybrid for differential signal isolation. The up-converter achieves measured OP1dB of -6.2 dBm and maximum CG of -11.2 dB including input and output baluns, and a 3-dB bandwidth of ~25 GHz. The CG and OP1dB are the highest among all up-converters in CMOS with RF at ~300 GHz. These results are particularly critical for mixer-last transmitters operating near 300 GHz for high datarate communication. A 280-GHz transmitter using the proposed double-balanced mixer is experimentally demonstrated in 65-nm CMOS. The transmitter has a maximum output power of -8 dBm. The spectrum measurement shows the capability of transmitting 30-Gbps QPSK signals. This transmitter is the first ever demonstration of transmitters using varactor-based mixer above 100 GHz and supporting such a data rate.Item Theoretical Simulation of Negative Differential Transconductance in Lateral Quantum Well nMOS Devices(American Institute of Physics Inc, 2017-01-23) Vyas, P. B.; Naquin, C.; Edwards, H.; Lee, Mark; Vandenberghe, W. G.; Fischetti, Massimo V.; 0000-0001-5926-0200 (Fischetti, MV); 21146635654041982414 (Vandenberghe, WG); Vyas, P. B.; Lee, Mark; Vandenberghe, William G.; Fischetti, Massimo V.We present a theoretical study of the negative differential transconductance (NDT) recently observed in the lateral-quantum-well Si n-channel field-effect transistors J. Appl. Phys. 118, 124505 (2015)]. In these devices, p⁺ doping extensions are introduced at the source-channel and drain-channel junctions, thus creating two potential barriers that define the quantum well across whose quasi-bound states resonant/sequential tunneling may occur. Our study, based on the quantum transmitting boundary method, predicts the presence of a sharp NDT in devices with a nominal gate length of 10-to-20 nm at low temperatures (~10 K). At higher temperatures, the NDT weakens and disappears altogether as a result of increasing thermionic emission over the p⁺ potential barriers. In larger devices (with a gate length of 30 nm or longer), the NDT cannot be observed because of the low transmission probability and small energetic spacing (smaller than k_{B}T) of the quasi-bound states in the quantum well. We speculate that the inability of the model to predict the NDT observed in 40 nm gate-length devices may be due to an insufficiently accurate knowledge of the actual doping profiles. On the other hand, our study shows that NDT suitable for novel logic applications may be obtained at room temperature in devices of the current or near-future generation (sub-10 nm node), provided an optimal design can be found that minimizes the thermionic emission (requiring high p⁺ potential-barriers) and punch-through (that meets the opposite requirement of potential-barriers low enough to favor the tunneling current).Item Tracking the Biochemistry of Cancer Cells and Dynamics of Physical Systems Using Nuclear Magnetic Resonance(2021-08-01T05:00:00.000Z) Khashami, Fatemeh; Krawcewicz, Wieslaw; Lumata, Lloyd; Lee, Mark; Glosser, Robert; Slinker, Jason; Lv, BingNuclear magnetic resonance (NMR) spectroscopy, providing a versatile technique for analyzing cancer metabolism based on 13C NMR analysis, is one of the most important tools for biological and more specifically cancer study purposes. The chemical shifts for 13C nuclei in organic molecules are spread out up to 200 ppm, enabling signal from each carbon in a compound be seen as a distinct peak. The relatively weak signals obtained from the NMR spectroscopy enables probing sensitive physical systems such as living systems without significantly disturbing them. In this dissertation, we have tracked 13C metabolism in different type of cancers, specially Glioblastoma Multiforme (GBM). GBM is an aggressive type of the Central Nervous System (CNS) tumor that grows within the brain tissue. In this study, we have investigated how the individually used fructose and glucose sugars and there combinations as high fructose corn syrup (HFCS) are metabolized in cultured SFxL glioblastoma and Huh-7 hepatocellular carcinoma cells as probed by 13C NMR spectroscopy. To understand more about cancer metabolism we did more study in glycolysis activity and pentose phosphate pathway (PPP). We used [1,2-13C] glucose to investigate the amount of lactate that could be produced from glycolysis versus PPP as the alternative route. Furthermore, we have investigated the metabolism of [1,2-13C] glucose with inhibitors of Lactate dehydrogenase A (LHDA) and sodium oxamate in GBM cells. LDHA is an important enzyme that is active in most of tissues. LDHA catalyzes the reversible conversion of pyruvate to lactate. Moreover, we have investigated the spin-lattice relaxation time (T1) of water-glycerol mixtures at the earth magnetic field. The water 1H T1s at various ratios of water-glycerol contents were measured at different temperatures ranging from 253.15 K to 353.15 K. In summary, this PhD dissertation presents and discusses a unique tool for deciphering cancer metabolism in vitro using NMR spectroscopy.