Self-switching diodes as RF rectifiers: evaluation methods and current progress

In the advancement of the Internet of Things (IoT) applications, widespread uses and applications of devices require higher frequency connectivity to be explored and exploited. Furthermore, the size, weight, power and cost demands for the IoT ecosystems also creates a new paradigm for the hardware where improved power efficiency and efficient wireless transmission needed to be investigated and made feasible. As such, functional microwave detectors to detect and rectify the signals transmitted in higher frequency regions are crucial. This paper reviewed the practicability of self switching diodes as Radio Frequency (RF) rectifiers. The existing methods used in the evaluation of the rectification performance and cut-off frequency are reviewed, and current achievements are then concluded. The works reviewed in this paper highlights the functionality of SSD as a RF rectifier with design simplicity, which may offer cheaper alternatives in current high frequency rectifying devices for application in low-power devices

Current and Potential Developments of Cortisol Aptasensing towards Point-of-Care Diagnostics (POTC)

Anxiety is a psychological problem that often emerges during the normal course of human life. The detection of anxiety often involves a physical exam and a self-reporting questionnaire. However, these approaches have limitations, as the data might lack reliability and consistency upon application to the same population over time. Furthermore, there might be varying understanding and interpretations of the particular question by the participant, which necessitating the approach of using biomarker-based measurement for stress diagnosis. The most prominent biomarker related to stress, hormone cortisol, plays a key role in the fight-or-flight situation, alters the immune response, and suppresses the digestive and the reproductive systems. We have taken the endeavour to review the available aptamer-based biosensor (aptasensor) for cortisol detection. The potential point-of-care diagnostic strategies that could be harnessed for the aptasensing of cortisol were also envisaged

Characteriztaion and modeling of Ultra-Thin Body fully-depleted SOI MOSFETs

Traditional scaling methodology which utilizes channel doping, shallow junctions, etc. is no longer sufficient to control the short channel effects (SCE) in the devices scaled down into decananometer range. For ultimate scaling when the SCE control becomes more crucial, alternative architectures such as e.g. ultra-thin body (UTB) silicon-on-insulator (SOI) offer better SCE control while maintaining very high device performances. Ultra-thin body device featuring ultra-thin buried oxide (UTBB) is the focus of this study. In the beginning of the thesis, the impact of the buried oxide thinning from standard (140 nm) to ultra-thin (10 nm) dimensions is investigated through experiments and simulations paying particular attention to the impact of drain and substrate biases. Better electrostatic control with lower DIBL can be achieved in UTBB devices compared to UTB ones. However, thin buried oxide triggers stronger influence of substrate depletion and coupling through the substrate on the device behavior. Simulations and experiments demonstrate that introduction of so-called ground-plane (i.e. localized highly-doped region in the substrate just underneath the BOX) can eliminate the substrate depletion effect without deteriorating the other benefits. Next, widely-employed by industry MASTAR equations for DIBL and subthreshold slope are modified in order to take into account the mean channel position and substrate depletion thickness as a function of substrate bias. In addition, the perspectives of UTBB for analog and RF applications are experimentally analyzed and benchmarked with other state-of-the art technologies. Lastly, the experimental and simulation study of UTBB MOSFETs is extended to Asymmetric Double Gate (ADG) operation regime. ADG-mode is shown to significantly improve device performance with final cut-off in the same frequency range as in single-gate mode.(FSA 3) -- UCL, 201

FET-biosensor for cardiac troponin biomarker

Acute myocardial infarction or myocardial infarction (MI) is a major health problem, due to diminished flow of blood to the heart, leads to higher rates of mortality and morbidity. The most specific markers for cardiac injury are cardiac troponin I (cTnI) and cardiac troponin T (cTnT) which have been considered as ‘gold standard’. Due to higher specificity, determination of the level of cardiac troponins became a predominant indicator for MI. Currently, field-effect transistor (FET)-based biosensors have been main interest to be implemented in portable sensors with the ultimate application in point-of-care testing (POCT). In this paper, we review on the FET-based biosensor based on its principle of operation, integration with nanomaterial, surface functionalization as well as immobilization, and the introduction of additional gate (for ambipolar conduction) on the device architecture for the detection of cardiac troponin I (cTnI) biomarker

FET-biosensor for cardiac troponin biomarker

Acute myocardial infarction or myocardial infarction (MI) is a major health problem, due to diminished flow of blood to the heart, leads to higher rates of mortality and morbidity. The most specific markers for cardiac injury are cardiac troponin I (cTnI) and cardiac troponin T (cTnT) which have been considered as ‘gold standard’. Due to higher specificity, determination of the level of cardiac troponins became a predominant indicator for MI. Currently, field-effect transistor (FET)-based biosensors have been main interest to be implemented in portable sensors with the ultimate application in point-of-care testing (POCT). In this paper, we review on the FET-based biosensor based on its principle of operation, integration with nanomaterial, surface functionalization as well as immobilization, and the introduction of additional gate (for ambipolar conduction) on the device architecture for the detection of cardiac troponin I (cTnI) biomarker

Perspectives of UTBB FD SOI MOSFETs for Analog and RF Applications

Ultra-thin body and buried oxide (UTBB) fully depleted (FD) silicon-on-insulator (SOI) MOSFETs are widely recognized as a promising candidate for 20 nm technology node and beyond, due to outstanding electrostatic control of short channel effects (SCE). Introduction of a highly-doped layer underneath thin buried oxide (BOX), so called ground-plane (GP), targets suppression of detrimental parasitic substrate coupling and opens multi-threshold voltage (V Th ) and dynamic-V Th opportunities within the same process as well as the use of back-gate control schemes [1, 2]. Electrostatics, scalability and variability issues in UTBB MOSFETs as well as their perspectives for low power digital applications are widely discussed in the literature [1–5]. At the same time assessment of UTBB FD SOI for analog and RF applications received less attention. This chapter will discuss Figures of Merit (FoM) of UTBB MOSFETs of interest for further analog/RF applications summarizing our original research over the last years [6–15]. Device analog/RF performance is assessed through the key parameters such as the transconductance, g m , the output conductance, g d , the intrinsic gain, A v and the cut-off frequencies, f T and f max. Particular attention is paid to (1) a wide-frequency band assessment, the only approach that allows fair performance prediction for analog/RF applications; (2) the effect of parasitic elements, whose impact on the device performance increases enormously in deeply downscaled devices, in which they can even dominate device performance. Whenever possible, we will compare FoM achievable in UTBB FD SOI devices with those reported for other advanced device

Fabrication of silicon nanowire sensors for highly sensitive pH and DNA hybridization detection

A highly sensitive silicon nanowire (SiNW)-based sensor device was developed using electron beam lithography integrated with complementary metal oxide semiconductor (CMOS) technology. The top-down fabrication approach enables the rapid fabrication of device miniaturization with uniform and strictly controlled geometric and surface properties. This study demonstrates that SiNW devices are well-aligned with different widths and numbers for pH sensing. The device consists of a single nanowire with 60 nm width, exhibiting an ideal pH responsivity (18.26 × 106 Ω/pH), with a good linear relation between the electrical response and a pH level range of 4–10. The optimized SiNW device is employed to detect specific single-stranded deoxyribonucleic acid (ssDNA) molecules. To use the sensing area, the sensor surface was chemically modified using (3-aminopropyl) triethoxysilane and glutaraldehyde, yielding covalently linked nanowire ssDNA adducts. Detection of hybridized DNA works by detecting the changes in the electrical current of the ssDNA-functionalized SiNW sensor, interacting with the targeted ssDNA in a label-free way. The developed biosensor shows selectivity for the complementary target ssDNA with linear detection ranging from 1.0 × 10−12 M to 1.0 × 10−7 M and an attained detection limit of 4.131 × 10−13 M. This indicates that the use of SiNW devices is a promising approach for the applications of ion detection and biomolecules sensing and could serve as a novel biosensor for future biomedical diagnosis