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Jueves 25 de Octubre, 2018
Viernes 26 de Octubre, 2018
Thermoelectric Energy Harvesting
The process that captures small amounts of energy that would otherwise be lost as heat, light, sound, vibration or movement is currently known as energy harvesting or energy scavenging. This captured energy has the potential to replace batteries for small, low power electronic devices. Specifically, thermoelectric energy-harvesting system takes advantage of any temperature difference and of the Seebeck effect to generate electrical power from any temperature gradient. In this work, it will be summarized all the efforts of the Microelectronics group at INAOE in its effort for searching new and more efficient materials and devices for thermoelectric energy-harvesting.
Physical measurements of semiconductor materials using in situ TEM and the atomic structure correlation
Transmission electron microscopy (TEM) provides information at atomic scale to study structural and chemical properties of novel materials such as metallic alloys, semiconductors, ceramics, etc. Understanding those materials’ behavior under external signals in now one of the most recent challenges in TEM. Physical measurements in situ TEM at individual nanostructures include mechanical (stress vs strain curves), electrical (I-V curves), phase transformations (cooling/heating), magnetization, and optical measurements. New investigations in materials at nanoscale explored by in situ TEM will be presented. Particularly, the study of crystalline orientation maps using precession electron diffraction and off-axis electron holography will be covered to study magnetic properties in materials, including in situ magnetization of metallic nanowires within the TEM column. In addition, new frontiers in crystalline analysis using fast electron diffraction, precession electron diffraction and electron dose-controlled for sensitive materials will be included in the seminar. Applications of the presented methods include the study of metallic nanoparticles, structural defects in thin films and finally the atomic study of 2D materials such as graphene, dichalcogenides and borophene.
Silicon Photomultipliers (SiPMs) for experiments in particle and astroparticle physics
Having solid-state photodetectors produced in commercial technologies that yield near single photon counting capability with picosecond time resolution has been one of the main breakthroughs in the field of silicon radiation detectors over the last years. This was achieved in form of Single-Photon Counting Avalanche Diodes (SPADs) and Silicon Photomultipliers (SiPMs). Modular 4-side tileable SiPM arrays with biasing voltages far below the several kV required by the photomultiplier tubes (PMT), a technology delivering similar performance, their comparatively lower production costs and their near absolute immunity to high magnetic fields made this the technology of choice over the standard used PMTs in many scientific and medical applications ranging from spectroscopy, positron emission tomography (PET), or neutron detection to instruments used in experiments designed for particle and astroparticle physics. The technological challenges and future perspectives of SiPM and SPAD technologies will be introduced based on different examples, such as a PET system developed for plant phenotyping, a scintillation based neutron detection system used for Small-Angle Neutron Scattering (SANS) experiments, and several atmospheric Cherenkov telescope developments used for high-energy gamma-ray detection.
Fabrication Process of c-Si Solar Cells Towards an Own Technology of High Effciency and Large Area
In this work is presented the progress of a fabrication process of solar cells based on the silicon technology, which is developed in the laboratory of microelectronics of INAOE, Puebla, Mexico. We are pursuing a simple process, of high efficiency, that could be implemented in large area (100 cm2) and compatible with industry. Our preliminary results are very satisfactory, since at this moment we have fabricated solar cells of 1 cm2 in low cost silicon substrates (silicon grown by the Czochralski method), with efficiencies of 16.4 % under standard Air Mass 1.5 solar radiation.
Considerations to Implement “In-Pixel” Thin Film Electronics for Large Area Sensor Arrays
Uninterrupted research on semiconductors and electronic devices is key for the continuous evolution of novel microelectronics. Particularly, thin film electronic devices have become a cost-effective alternative technology to be used in applications where conventional semiconductors materials (e. g. crystalline silicon) are not functional. Such applications involve systems capable of being flexible and transparent, rugged and light weight, large area and cheap. Most to these applications take advantage of cost-effective manufacturing process to produce large and highly dense arrays of active devices including a variety of sensors, light emitting elements, actuators or probes for stimulation. Moreover, to fully take advantage of these devices in large area applications, every single one of them require a backplane of thin film electronics to perform certain “active” or “passive” control/readout. Here, we will detail the methodology and considerations to design, fabricate and implement polysilicon circuits with the requirements for in-pixel preamplification for large area thin film radiation detectors. We demonstrate the implementation of a full thin film radiation detection system using CdS/CdTe sensors for single event charged particle detection. These results demonstrate the feasibility to develop fully integrated radiation detectors arrays for large area special nuclear material monitoring.
Scrutinizing MOSFET asymmetric series resistance extraction methods
The downscaling of MOSFETs’ dimensions has been affected by the growing deleterious presence of asymmetrical parasitic drain and source resistance (RD and RS). The difference between RD and RS could be caused by unintentional variations in the fabrication process and by device degradation. Many methods have been proposed and reviewed to extract the total parasitic drain and source resistance (RD + RS) assuming that both resistances are equal (RD = RS). We will review and scrutinize the methods proposed to extract the difference between drain and source resistance (RD - RS).
Applications of DFT and beyond: From electronic structure analysis to multiscale growth modeling
These days the density function theory (DFT) has a significantly important role in the fields of physics, chemistry, and biology because the accuracy of DFT has increased notably and computational cost has been reduced over the last few decades. The talk will briefly deal with the theory of DFT, and introduce its applications we are currently working on. The electronic structure analysis is a powerful application of DFT, which allows us to interpret how electrons behave in a system. We carry out electronic structures analysis based on DFT in order to understand superconductor-graphene edge contact where the superconducting proximity effect has been observed with ballistic Josephson junctions. Although DFT has been very successful with respect to ground-state properties, the Born-Oppenheimer approximation with the ground-state DFT has to be waived to reproduce exited-state dynamics. The time-dependent density functional theory (TDDFT) is a technique to use Ehrenfest dynamics instead of the Born-Oppenheimer approximation. Using TDDFT, we explore the excited-state dynamics for the electron-beam-stimulated desorption that facilitates electron-enhanced ALD at low temperature. Finally, the kinetic Monte Carlo (KMC) approach will be briefly introduced. Since DFT is still demanding for realistic length and time scales, DFT-KMC multiscale growth modeling can be used to investigate surface morphology during thin film deposition. This work was supported in part by Semiconductor Research Corporation (SRC), and also supported by grant from the U.S. Army Research Laboratory's Army Research Office (ARO).
Integrated Antennas; Past, Present and Future
The design, response and areas of opportunities of antennas, especially those included in an Integrated Circuit, are presented and analyzed. The talk is divided into three global sections, covering three frequency ranges: low frequencies from MHz to 10 GHz (The Past); the middle frequency range from 10 to 300 GHz (The Present); and high frequencies, from 300 GHz and up (The Future). In all cases, compatibility with conventional CMOS processes is highlighted, since antennas are a fundamental component in wireless communication integrated circuits.
Emerging Opportunities of Advanced Physical Analysis Techniques for Nano-scale Semiconductor Devices
High resolution transmission electron microscope (HRTEM) and the associated in-situ techniques are commonly used in the study of the material and structural systems in both start-of-the-art memory and LOGIC devices at nano-scale. HRTEM can provide detailed cross-sectional characterization of devices with compositional, chemical and structural information at atomic scale while the in-situ stressing methodologies like electrical, mechanical and temperature can further discover the fundamental mechanisms in real time. For example, in-situ TEM analysis has been used to study the basic switching mechanisms in MIS stacks to unearth the basic mechanisms responsible for the associated SET and RESET. Concurrently, scanning probe microscopy (SPM)-based techniques have also been explored to study oxygen vacancy-based RRAM switching with detailed surface, electron energy and tomography information. In this talk, new applications of advanced HRTEM and SPM techniques to comprehensively study the switching and failure mechanisms of advanced LOGIC and memory devices will be presented.
Unified Picture of Dielectric Breakdown in 2D Layered Hexagonal Boron Nitride
Hexagonal boron nitride (h-BN) has gained interest among CMOS dielectric community as a suitable dielectric for graphene-based 2-D nanoelectronic devices. h-BN possess excellent thermal, electrical, and mechanical properties enabling realization of flexible electronic devices and sensors. Reliability of h-BN has attracted attention in recent times as fabrication of high quality crystalline h-BN over large area has shown positive results. The talk would focus on h-BN dielectric breakdown mechanisms under different electrical stresses. Case studies on controlled defect generation in h-BN for ultra-low power resistive switching applications would also be presented.
Engineering of Solid-State Materials and Devices by Atomic-Layer Deposition
This work resumes some of the most important results that have been obtained in our research group regarding the use of atomic-layer deposition (ALD) as the main thin-film deposition technique for metal oxides with high dielectric constant. ALD has been applied for the development of logic, memory and sensing technologies in which ultra-thin metal oxides (Al2O3, HfO2 and TiO2 with a physical thickness of 1nm ≤ th ≤ 10nm), are the active part of the final devices under study. All these technologies are fully CMOS compatible, so that an ever increased functionality to these materials can be sought in order to accelerate truly advanced More-than-Moore applications.
Atomic Layer Deposition of Gold Metal: Mechanism and Surface Chemistry
Gold metal is an important thin film material for enhanced spectroscopy, meta-material fabrication, plasmon-based sensing, and catalysis. Since it was first reported in 2016, deposition of gold metal by atomic layer deposition has rapidly progressed to encompass both thermal and plasma processes, and the mechanism of deposition has been studied intensely to determine how the process is initiated and to improve precursor and process performance. A variety of potential precursors will be presented, and their surface chemistry will be discussed. Nucleation studies using FT-IR and synchrotron XRD will be presented to help understand the initiation of deposition, and process modifications to adapt to fluidized bed deposition will be presented.
DC and RF reliability aspects of CMOS technologies
Experimental results on 28 GHz reliability and random telegraph noise of a 45nm SOI technology, are introduced. A general observation is that reliability is frequency dependent (in the 10 MHz-67GHz frequency range), that an external magnetic field changes the capture/emission at the interface traps altering the degradation mechanism. Another relevant experimental observation is that degradation reduces at high frequencies at under specific levels of degradation. A hypothetical theory is introduced in order to explain the magneto-modulation of trapping/detrapping and reduction of degradation at high frequencies.
Advanced Materials and Devices for Large Area Electronics
The development of low temperature device technologies that have enabled flexible displays also present opportunities for flexible electronics and flexible integrated systems. In this presentation, we discuss fundamental materials properties including crystalline structure, interfacial reactions, doping, etc. defining performance and reliability of perovskite II-VI and oxide-based materials and devices for flexible and large area electronics. We investigate and evaluate several materials such as ZnO, IGZO, ZnO:N, SnO, SnOx , CdS, ZnS and CdTe for possible applications in flexible, low metal content, sensor systems for unattended ground sensors, smart medical bandages, electronic ID tags for geo-location, conformal antennas, neutron/gamma-ray/x-ray detectors, etc. Also, our efforts to develop novel integration schemes, circuits, memory, sensors as well as novel contacts, dielectrics and semiconductors for large area electronics are presented. In particular, we discuss fundamental materials properties including crystalline structure, interfacial reactions, doping, etc. defining device performance and reliability of inorganic oxides, II-VI and hybrid perovskite materials. Materials characterization methods including RBS, XPS, XRD, etc. are used to analyze materials deposited by pulsed laser deposition, chemical bath deposition and inkjet printing. Finally, we demonstrate an integrated neutron sensor fully fabricated at UT-Dallas that includes wireless communication to a mobile device.
Return of Ferroelectrics:
Low Thermal Budget HfZrO2 Ferroelectric Capacitors
In 1990s and early 2000s, PZT and SBT had been extensively investigated for ferroelectric random access memory (FRAM) using 1T-1C (or 2T-2C) architecture for high density stand-alone memory applications. Unfortunately, this technique faced a scaling limit due to thickness scaling, 3D integration and compatibility to sub 100 nm CMOS technology. Since ferroelectricity of Hf based oxide has been reported in 2011, the renaissance of ferroelectric begins for realization of not only conventional FRAM for NOR and embedded nonvolatile devices but also memory transistor (1T) for next generation SCM (storage class memory) and 3D cross-point devices for neuromorphic devices. In this presentation, ferroelectric properties of atomic layer deposited Hf0.5Zr0.5O2 (HZO) thin films will be reported for the development of future ferroelectric random access memory capacitors. A 10 nm thick HZO sample annealed at 400°C for 60 s in an N2 atmosphere after TiN top electrode deposition showed large switching polarization (~45 μC/cm2) and low ferroelectric saturation voltage (~1.5 V) from pulse-switching write/read measurement tests. Furthermore, endurance fatigue measurements were performed and no significant degradation was observed until 108 switching cycles at 2 V. This low thermal budget ferroelectric capacitor technique is expected to be adopted at the stage of backend process and 3D integration for novel applications. I will also discuss alternative thoughts on ferroelectric negative capacitance issues. In addition, J. Kim’s lab activities, particularly related to advanced atomic-layer deposited (ALD) ultrathin films and their characterization, will be also introduced.
Fabrics as a high-tech material for printed sensors and actuators
Woven and non-woven fabrics such as cellulose paper and textiles, are low-cost, flexible, porous and generally biodegradable materials that are ideally suited for the fabrication of disposable sensors and actuators. Unlike microfabricated (e.g., PDMS-based) microfluidic systems, printed microfluidics produced using fabrics do not require pumps and other complex components, allowing construction of highly compact, miniaturized devices for rapid, multiplex sensing of various bioanalytes (such as DNA) in the field. The intrinsic properties of cellulose fabrics (cellulose is a highly hydrophilic biopolymer) also enable measuring gaseous analytes in a completely new way. This new method of sensing gases allows monitoring respiratory activity in humans and detecting volatiles formed by the degradation of food to measure food freshness. Regardless of the application, devices produced using fabrics only require a series of simple methods of fabrication without the need for specialized facilities such as a cleanroom. In this talk, I will present our latest work on sensors and actuators created using fabrics and how they can enable new classes of low-cost technologies.