Siddhartha P. Duttagupta

Bio: Siddhartha P. Duttagupta is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Porous silicon & Photovoltaic system. The author has an hindex of 24, co-authored 139 publications receiving 4206 citations. Previous affiliations of Siddhartha P. Duttagupta include Indian Institutes of Technology & Center for Excellence in Education.

Silicon-based visible light-emitting devices integrated into microelectronic circuits

Abstract: MICROELECTRONIC device integration has progressed to the point where complete 'systems-on-a-chip' have been realized1–3. Now that optoelectronics is becoming increasingly important for information and communication technologies, there is a need to develop optoelectronic devices that can be integrated with standard microelectronics. Conventional semiconductor technology is largely based on crystalline silicon, which (being an indirect bandgap semiconductor) is an inefficient light-emitting material. This has stimulated significant effort towards developing silicon-based optoelectronic components and, of the several strategies explored so far4,5, the use of porous silicon appears the most promising; porous silicon produces high-efficiency, room-temperature, visible photoluminescence6, and its material and optical properties have been studied in detail7,8. But the extreme reactivity and fragility of porous silicon have hitherto prevented its integration with conventional silicon processing technology. We have recently shown9,10 that the thermal and chemical stability of porous silicon can be greatly enhanced — while retaining desirable light-emitting and charge-transport properties — by partial oxidation. Here we take advantage of these improvements in material properties to demonstrate the successful integration of silicon-based visible light-emitting devices into a standard bipolar microelectronic circuit.

Nanocrystalline-silicon superlattice produced by controlled recrystallization

Abstract: Nanocrystalline-silicon superlattices are produced by controlled recrystallization of amorphous-Si/SiO2 multilayers. The recrystallization is performed by a two-step procedure: rapid thermal annealing at 600–1000 °C, and furnace annealing at 1050 °C. Transmission electron microscopy, Raman scattering, x-ray and electron diffraction, and photoluminescence spectroscopy show an ordered structure with Si nanocrystals confined between SiO2 layers. The size of the Si nanocrystals is limited by the thickness of the a-Si layer, the shape is nearly spherical, and the orientation is random. The luminescence from the nc-Si superlattices is demonstrated and studied.

Stable and efficient electroluminescence from a porous silicon‐based bipolar device

Abstract: A complete process compatible with conventional Si technology has been developed in order to produce a bipolar light‐emitting device. This device consists of a layer of light‐emitting porous silicon annealed at high temperature (800–900 °C) sandwiched between a p‐type Si wafer and a highly doped (n+) polycrystalline Si film. The properties of the electroluminescence (EL) strongly depend on the annealing conditions. Under direct bias, EL is detected at voltages of ∼2 V and current densities J∼1 mA/cm2. The maximum EL intensity is 1 mW/cm2 and the EL can be modulated by a square wave current pulse with frequencies ν≥1 MHz. No degradation has been observed during 1 month of pulsed operation.

A review of the antibacterial effects of silver nanomaterials and potential implications for human health and the environment

Abstract: Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver–dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials.

Optical gain in silicon nanocrystals

Abstract: Adding optical functionality to a silicon microelectronic chip is one of the most challenging problems of materials research. Silicon is an indirect-bandgap semiconductor and so is an inefficient emitter of light. For this reason, integration of optically functional elements with silicon microelectronic circuitry has largely been achieved through the use of direct-bandgap compound semiconductors. For optoelectronic applications, the key device is the light source--a laser. Compound semiconductor lasers exploit low-dimensional electronic systems, such as quantum wells and quantum dots, as the active optical amplifying medium. Here we demonstrate that light amplification is possible using silicon itself, in the form of quantum dots dispersed in a silicon dioxide matrix. Net optical gain is seen in both waveguide and transmission configurations, with the material gain being of the same order as that of direct-bandgap quantum dots. We explain the observations using a model based on population inversion of radiative states associated with the Si/SiO2 interface. These findings open a route to the fabrication of a silicon laser.

A Survey on Wearable Sensor-Based Systems for Health Monitoring and Prognosis

Abstract: The design and development of wearable biosensor systems for health monitoring has garnered lots of attention in the scientific community and the industry during the last years. Mainly motivated by increasing healthcare costs and propelled by recent technological advances in miniature biosensing devices, smart textiles, microelectronics, and wireless communications, the continuous advance of wearable sensor-based systems will potentially transform the future of healthcare by enabling proactive personal health management and ubiquitous monitoring of a patient's health condition. These systems can comprise various types of small physiological sensors, transmission modules and processing capabilities, and can thus facilitate low-cost wearable unobtrusive solutions for continuous all-day and any-place health, mental and activity status monitoring. This paper attempts to comprehensively review the current research and development on wearable biosensor systems for health monitoring. A variety of system implementations are compared in an approach to identify the technological shortcomings of the current state-of-the-art in wearable biosensor solutions. An emphasis is given to multiparameter physiological sensing system designs, providing reliable vital signs measurements and incorporating real-time decision support for early detection of symptoms or context awareness. In order to evaluate the maturity level of the top current achievements in wearable health-monitoring systems, a set of significant features, that best describe the functionality and the characteristics of the systems, has been selected to derive a thorough study. The aim of this survey is not to criticize, but to serve as a reference for researchers and developers in this scientific area and to provide direction for future research improvements.

Antimicrobial activity of metals: mechanisms, molecular targets and applications

Abstract: Metals have been used as antimicrobial agents since antiquity, but throughout most of history their modes of action have remained unclear. Recent studies indicate that different metals cause discrete and distinct types of injuries to microbial cells as a result of oxidative stress, protein dysfunction or membrane damage. Here, we describe the chemical and toxicological principles that underlie the antimicrobial activity of metals and discuss the preferences of metal atoms for specific microbial targets. Interdisciplinary research is advancing not only our understanding of metal toxicity but also the design of metal-based compounds for use as antimicrobial agents and alternatives to antibiotics.