Electrically Guided DNA Immobilization and Multiplexed DNA Detection with Nanoporous Gold Electrodes.

Molecular diagnostics have significantly advanced the early detection of diseases, where the electrochemical sensing of biomarkers (e.g., DNA, RNA, proteins) using multiple electrode arrays (MEAs) has shown considerable promise. Nanostructuring the electrode surface results in higher surface coverage of capture probes and more favorable orientation, as well as transport phenomena unique to nanoscale, ultimately leading to enhanced sensor performance. The central goal of this study is to investigate the influence of electrode nanostructure on electrically-guided immobilization of DNA probes for nucleic acid detection in a multiplexed format. To that end, we used nanoporous gold (np-Au) electrodes that reduced the limit of detection (LOD) for DNA targets by two orders of magnitude compared to their planar counterparts, where the LOD was further improved by an additional order of magnitude after reducing the electrode diameter. The reduced electrode diameter also made it possible to create a np-Au MEA encapsulated in a microfluidic channel. The electro-grafting reduced the necessary incubation time to immobilize DNA probes into the porous electrodes down to 10 min (25-fold reduction compared to passive immobilization) and allowed for grafting a different DNA probe sequence onto each electrode in the array. The resulting platform was successfully used for the multiplexed detection of three different biomarker genes relevant to breast cancer diagnosis

Suspended 1D metal oxide nanostructure-based gas sensor

Department of Materials Science and EngineeringWe developed a novel batch fabrication technology for the ultralow-power-consumption metal oxide gas sensing platform consisting of a suspended glassy carbon heating nanostructure and hierarchical metal oxide nanostructures forests fabricated by the carbon-micro electromechanical systems (carbon-MEMS) and selective nanowire growth process. We have developed a new manufacturing process for suspended glass carbon nanostructures such as single nanowire, nano-mesh and nano-membranes fabricated using carbon-MEMS consisting of the UV-lithography and the polymer pyrolysis processes. We designed a gas sensing platform consisting of suspended glassy carbon heating nanostructures and suspended hierarchical metal oxide nanostructure forests for the sensing part. Glassy carbon structure produced by the carbon-MEMS has many advantages such as high thermal & chemical stabilities, good hardness, and good thermal & electrical characteristics. The electrical conductivity of glassy carbon nanostructures has been increased more than three times by using rapid thermal annealing (RTA) process owing to the inferior heating property of glassy carbon nano-heater in the electrical conductivity. In order to divide the suspended glassy carbon nano-heater and the suspended hierarchical metal oxide nanostructures forests, the insulating layer of HfO2 materials is a high dielectric constant and is deposited uniformly using a atomic layer deposition (ALD) process on a suspended glassy carbon nano-heater. Suspended hierarchical metal oxide nanostructures forests were grown circumferentially on the suspended HfO2/glassy carbon nano-heater using a hydrothermal method consisting of the seed deposition and the growth processes. For selective metal oxide seed layer deposition process, a short-time exposed polymer patterning process was performed using the positive photoresist. After the polymer patterning process, a metal oxide seed layer is deposited using the rf-sputtering system, followed by a metal oxide nanostructure growth process. The distinguishing architecture of a suspended hierarchical metal oxide nanostructures forests/HfO2/glassy carbon nanostructure ensures efficient mass transport to the metal oxide nanostructure detection point of the gas analyte, resulting in highly sensitive gas detection. In the absence of an external heating system, the ultralow-power-consumption gas sensing platform of a suspended hierarchical metal oxide nanostructures forests/HfO2/glassy carbon nanostructure has excellent the gas sensing characteristics.ope

Caracterização do estresse mecânico de nanoestruturas de silício tensionado por espectroscopia Raman

Orientadores: José Alexandre Diniz, Marcos Vinicius Puydinger dos SantosDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A engenharia de silício tensionado provou ser uma tecnologia de sucesso para manter a lei de Moore e apresenta um grande potencial para o seu uso em nós tecnológicos altamente estressados e ainda menores na microeletrônica do futuro. Essa tarefa demanda o uso de técnicas de caracterização do estresse mecânico para o desenvolvimento e pesquisa em semicondutores. Uma potencial ferramenta de caracterização que permite a medição do estresse no silício de forma quantitativa é a espectroscopia Raman. Esse método de caracterização consiste em uma técnica não destrutiva e bem estabelecida que permite a caracterização do estresse com uma resolução espacial abaixo de 1 ?m e não requer procedimentos complexos de preparação da amostra. Contudo, estudos sobre o comportamento do deslocamento Raman em estruturas altamente tensionadas (tensão maior que 2 GPa) com dimensão crítica menor que 100 nm são escassos na literatura, sendo um gargalo para o uso de medidas Raman de forma sistemática em dispositivos tecnológicos futuros. Aqui, foi investigado o comportamento do estresse em função do deslocamento Raman da superfície de silício (001) de nanofios suspensos ultra finos (15 nm de espessura) e altamente tensionados com estresses na faixa de 0 ¿ 6.3 Gpa ao longo da direção cristalográfica [110]. O uso de nanofios ultrafinos como plataforma de estudo , ao longo da direção cristalográfica [110], permitiu a investigação sistemática de um bloco essencial que pode estar presente nos canais de transistores nMOS futuros. Alêm disso, essa plataforma suspensa atingiu valores de tensão ultra altos (até 6.3GPa) sem atuadores externos, permitindo pela primeira vez o estudo sistemático do comportamento da espectrocopia Raman em nanofios altamente tensionados. Os estresses foram medidos por simulações de elementos finitos (FEM) como forma de atingir uma grande precisão na caracterização da tensão. Então, medidas Raman experimentais foram realizadas seguidas de um protocolo de correção térmica para extrair o pico Raman corrigido livre de efeitos térmicos. O coeficiente de deslocamento do estresse (SSC) extraído, para baixa tensão (abaixo de 4.5 GPa), estava em boa concordância com alguns valores de SSC da literatura. Para maiores valores de tensão (maior que 4.5 GPa), demonstrou-se, pela primeira vez, que a relação linear deslocamento Raman - estresse não ocorre, requerendo uma correção empírica do modelo que está sendo proposta neste trabalho. Esses resultados demonstram a viabilidade da técnica Raman para caracterização do estresse de nanofios de silício ultrafinos, no qual deve ser útil para caracterizar nanodispositivos de silício tensionado para nós tecnológicos abaixo dos 100 nm sujeitos a uma faixa ampla de tensão, contribuindo para um tópico importante na indústria de semicondutoresAbstract: Strained silicon engineering has proven to be a successful technology to keep Moore¿s law and presents a great potential for its use in even smaller and highly stressed technological nodes in microelectronics in the future. Such a task demands the use of stress characterization techniques for semiconductor research and development. One potential characterization tool which makes possible quantitative stress measurement of silicon is the Raman spectroscopy. This characterization method is a wellestablished non-destructive technique that permits stress characterization with a spatial resolution of below 1 ?m and does not require complex sample preparation procedure. However, studies on Raman shift behavior of highly stressed structures (stress greater than 2 GPa) with the critical dimension smaller than 100 nm are scarce in the literature, being a bottleneck for the systematic use of Raman measurements in future technological devices. Here, it was investigated the Raman shift-stress behavior from the (001) silicon surface of highly strained ultra-thin (15 nm-thick) suspended nanowires with stresses in the range of 0 ¿ 6.3 GPa along the [110] direction. The use of ultrathin nanowires as a platform of study, along the [110] crystallographic direction, allowed the systematic investigation of one essential block that might be present in future nMOS transistors channels. Furthermore, this suspended platform reached ultra-high stress values (up to 6.3 GPa) without external actuators, allowing for the first time the systematic study of the Raman stress behavior of highly stressed nanowires. The stresses were evaluated by finite element method (FEM) simulations to achieve great accuracy in the stress characterization. Then, experimental Raman measurements were performed, followed by a thermal correction protocol to extract the corrected Raman peak free of thermal effects. The extracted stress shift coefficient (SSC), for lower stresses (below 4.5 GPa), was in good agreement with some of the SSC values in literature. For higher stresses (greater than 4.5 GPa), it was demonstrated, for the first time, that the linear shift Raman - stress relation does not hold, thus requiring an empirical model correction proposed in this work. The results demonstrate the feasibility of the Raman technique for the stress characterization of ultra-thin silicon nanowires, which should be useful to characterize strained silicon nanodevices for technological nodes below 100 nm under a wide range of stresses, contributing to such an important topic in the semiconductor industryMestradoEletrônica, Microeletrônica e OptoeletrônicaMestre em Engenharia Elétrica2018/02598-4FAPES

Nanogap Device: Fabrication and Applications

A nanogap device as a platform for nanoscale electronic devices is presented. Integrated nanostructures on the platform have been used to functionalize the nanogap for biosensor and molecular electronics. Nanogap devices have great potential as a tool for investigating physical phenomena at the nanoscale in nanotechnology. In this dissertation, a laterally self-aligned nanogap device is presented and its feasibility is demonstrated with a nano ZnO dot light emitting diode (LED) and the growth of a metallic sharp tip forming a subnanometer gap suitable for single molecule attachment. For realizing a nanoscale device, a resolution of patterning is critical, and many studies have been performed to overcome this limitation. The creation of a sub nanoscale device is still a challenge. To surmount the challenge, novel processes including double layer etch mask and crystallographic axis alignment have been developed. The processes provide an effective way for making a suspended nanogap device consisting of two self-aligned sharp tips with conventional lithography and 3-D micromachining using anisotropic wet chemical Si etching. As conventional lithography is employed, the nanogap device is fabricated in a wafer scale and the processes assure the productivity and the repeatability. The anisotropic Si etching determines a final size of the nanogap, which is independent of the critical dimension of the lithography used. A nanoscale light emitting device is investigated. A nano ZnO dot is directly integrated on a silicon nanogap device by Zn thermal oxidation followed by Ni and Zn blanket evaporation instead of complex and time consuming processes for integrating nanostructure. The electrical properties of the fabricated LED device are analyzed for its current-voltage characteristic and metal-semiconductor-metal model. Furthermore, the electroluminescence spectrum of the emitted light is measured with a monochromator implemented with a CCD camera to understand the optical properties. The atomically sharp metallic tips are grown by metal ion migration induced by high electric field across a nanogap. To investigate the growth mechanism, in-situ TEM is conducted and the growing is monitored. The grown dendrite nanostructures show less than 1nm curvature of radius. These nanostructures may be compatible for studying the electrical properties of single molecule

Nanofabrication of Metallic Nanostructures and Integration with Light Detection Devices

Metallic nanostructures have been investigated with various applications especially for integration with light detection devices. The incident light can be manipulated by those nanostructures to enhance light absorption therefor improve device performance. However, previous studies focused on optical design. The electrical properties of these integrated light detection devices have not been fully considered. The photon generated carriers transport and collection are critical for light detection devices as well. An optimized device platform considering from both the optical and electrical aspects to fully utilize these nanostructures is highly desired for future light detection devices. This dissertation targeted on three objectives, beginning with the fabrication process development of various nanostructures on different substrates. High quality nanostructures were achieved with minimum 20nm gap and 45nm line width. The second objective was developing the metallic fishnet nanostructures integrated Schottky contact a-Si solar cell to improve both light absorption and photon generated carrier collection. The fishnet was designed as the light trapping structure and 2D connected top contact to collect carriers. The third objective was developing metallic nanostructures integrated GeSn photodetectors. The H shape nano antennas were integrated on GeSn photodetectors. Multiple resonant absorption peaks at infrared range were observed using spectroscopic ellipsometry. However, there was no obvious photoresponse value improvement of developed solar cells and H shape antennas integrated GeSn photodetectors. For further investigation, interdigitated electrodes integrated GeSn photodetectors were designed. With less carrier transit time, the responsivity value of the integrated Ge0.991Sn0.009 photodetector was 72µA/W at 1.55µm at room temperature which was 6 times higher comparing to device without integration. Meanwhile, with the increased carrier life time by decreasing temperature, the responsivity value of integrated Ge0.93Sn0.07 detectors at 1.55µm at 100K was 8.5mA/W which was 200 times higher than the value at 300K. These results suggest relative large surface recombination rate was the dominant loss mechanism in metallic nanostructures integrated light detection devices, as the ratio of carrier life time and transit time determines the gain of photodetector. The light detection devices integrated with metallic nanostructures can be developed to maximize device performance with light trapping effect and carrier collection efficiency

Progress in Nanoporous Templates: Beyond Anodic Aluminum Oxide and Towards Functional Complex Materials

Successful synthesis of ordered porous, multi-component complex materials requires a series of coordinated processes, typically including fabrication of a master template, deposition of materials within the pores to form a negative structure, and a third deposition or etching process to create the final, functional template. Translating the utility and the simplicity of the ordered nanoporous geometry of binary oxide templates to those comprising complex functional oxides used in energy, electronic, and biology applications has been met with numerous critical challenges. This review surveys the current state of commonly used complex material nanoporous template synthesis techniques derived from the base anodic aluminum oxide (AAO) geometry

Primary thermometry triad at 6 mK in mesoscopic circuits

Quantum physics emerge and develop as temperature is reduced. Although mesoscopic electrical circuits constitute an outstanding platform to explore quantum behavior, the challenge in cooling the electrons impedes their potential. The strong coupling of such micrometer-scale devices with the measurement lines, combined with the weak coupling to the substrate, makes them extremely difficult to thermalize below 10 mK and imposes in-situ thermometers. Here we demonstrate electronic quantum transport at 6 mK in micrometer-scale mesoscopic circuits. The thermometry methods are established by the comparison of three in-situ primary thermometers, each involving a different underlying physics. The employed combination of quantum shot noise, quantum back-action of a resistive circuit and conductance oscillations of a single-electron transistor covers a remarkably broad spectrum of mesoscopic phenomena. The experiment, performed in vacuum using a standard cryogen-free dilution refrigerator, paves the way toward the sub-millikelvin range with additional thermalization and refrigeration techniques.Comment: Article and Supplementar