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João Pedro Conde

Other affiliations: Princeton University, IBM, Technical University of Lisbon  ...read more
Bio: João Pedro Conde is an academic researcher from Instituto Superior Técnico. The author has contributed to research in topics: Amorphous silicon & Silicon. The author has an hindex of 32, co-authored 308 publications receiving 4310 citations. Previous affiliations of João Pedro Conde include Princeton University & IBM.


Papers
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TL;DR: In this article, the authors describe how sequences of daily global radiation can be generated for any location, using as input only the average monthly radiation for that location (or the average month number of sunshine hours) using a library of Markov transition matrices, each corresponding to a specific interval in Kt.

259 citations

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TL;DR: In this paper, the effect of hydrogen dilution on the optical, transport, and structural properties of amorphous and micro-crystalline silicon thin films deposited by hot-wire (HW) chemical vapor deposition and radio-frequency (RF) plasmaenhanced chemical vapor deblurring using substrate temperatures (Tsub) of 100 and 25
Abstract: The effect of hydrogen dilution on the optical, transport, and structural properties of amorphous and microcrystalline silicon thin films deposited by hot-wire (HW) chemical vapor deposition and radio-frequency (rf) plasma-enhanced chemical vapor deposition using substrate temperatures (Tsub) of 100 and 25 °C is reported. Microcrystalline silicon (μc-Si:H) is obtained using HW with a large crystalline fraction and a crystallite size of ∼30 nm for hydrogen dilutions above 85% independently of Tsub. The deposition of μc-Si:H by rf, with a crystallite size of ∼8 nm, requires increasing the hydrogen dilution and shows decreasing crystalline fraction as Tsub is decreased. The photoconductivity, defect density, and structure factor of the amorphous silicon films (a-Si:H) are strongly improved by the use of hydrogen dilution in the Tsub range studied. a-Si:H films with a photoconductivity-to-dark conductivity ratio above 105, a deep defect density below 1017 cm−3, an Urbach energy below 60 meV and a structure factor below 0.1 were obtained for rf films down to 25 °C (at growth rates ∼0.1–0.4 A/s) and for HW films down to 100 °C (at growth rates ∼10 A/s), using the appropriate hydrogen dilution. In the low Tsub range studied, the growth mechanism, film properties, and the amorphous to microcrystalline silicon transition depend on the flux of atomic hydrogen available. The properties of the films are compared to those of samples produced at 175 and 250 °C in the same reactors.

141 citations

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TL;DR: A flat microdevice which incorporates a thin-film amorphous silicon (a-Si:H) photodetector with an upper layer of functionalized SiO2 is used to quantify the density of both immobilized and hybridized DNA oligonucleotides labeled with a fluorophore, enabling on-chip electronic data acquisition.
Abstract: A flat microdevice which incorporates a thin-film amorphous silicon (a-Si:H) photodetector with an upper layer of functionalized SiO2 is used to quantify the density of both immobilized and hybridized DNA oligonucleotides labeled with a fluorophore. The device is based on the photoconductivity of hydrogenated amorphous silicon in a coplanar electrode configuration. Excitation, with near UV/blue light, of a single-stranded DNA molecule tagged with the fluorophore 1-(3-(succinimidyloxycarbonyl)benzyl)-4-(5-(4-methoxyphenyl)oxazol-2-yl) pyridinium bromide (PyMPO), results in the emission of visible light. The emitted light is then converted into an electrical signal in the photodetector, thus allowing the optoelectronic detection of the DNA molecules. The detection limit of the present device is of the order of 1 3 10 12 molecules/cm 2 and is limited by the efficiency of the filtering of the excitation light. A surface density of 33.5 6 4.0 pmol/cm 2 was measured for DNA covalently immobilized to the functionalized SiO2 thin film and a surface density of 3.7 6 1.5 pmol/cm 2 was measured for the complementary DNA hybridized to the bound DNA. The detection concept explored can enable on-chip electronic data acquisition, improving both the speed and the reliability of DNA microarrays.

93 citations

Journal ArticleDOI
TL;DR: The covalent immobilization of DNA, followed by DNA hybridization, and of the surface adsorption of oligonucleotides and proteins were detected electronically by the a-Si:H ISFET.

85 citations

Journal ArticleDOI
TL;DR: In this article, the optical, structural and transport properties of hydrogenated amorphous silicon-carbon alloys are studied over the entire compositional range of carbon content. And the properties of the ECR a-SiC:H alloys compared with those of alloys deposited by rf glow discharge.
Abstract: The optoelectronic and structural properties of hydrogenated amorphous silicon-carbon alloys ~a-SiC:H! are studied over the entire compositional range of carbon content. The films are prepared using low-power electron-cyclotron resonance ~ECR! plasma-enhanced chemical vapor deposition. The carbon content was varied by using different methane ~or ethylene-!-to-silane gas phase ratios and by introducing the methane ~or ethylene! either remotely into the plasma stream or directly through the ECR source, together with the excitation gas ~hydrogen!. Regardless of the deposition conditions and source gases used, the optical, structural and transport properties of the a-SiC:H alloys followed simple universal dependencies related to changes in the density of states associated with their structural disorder. The deep defect density from photothermal deflection spectroscopy, the ESR spin density, the steady state and the transient photoluminescence, the dark and photoconductivity, the temperature of the hydrogen evolution peaks and the bonding from infrared spectroscopy are correlated to the Urbach tail energy, the B factor of the Tauc plot and E04 ~defined as the energy at which the absorption coefficient is equal to 10 4 cm 21 !. Silicon-rich and carbon-rich regions with very different properties, corresponding approximately to carbon fractions below and above 0.5, respectively, can be distinguished. The properties of the ECR a-SiC:H alloys are compared with those of alloys deposited by rf glow discharge. © 1999 American Institute of Physics. @S0021-8979~99!00606-4#

84 citations


Cited by
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TL;DR: In this paper, the authors describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of diamond-like carbon.
Abstract: Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

5,400 citations

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TL;DR: In this paper, blue photoluminescence from chemically derived graphene oxide Goki Eda, Yun-Yue Lin, Cecilia Mattevi, Hisato Yamaguchi, Hsin-An Chen, I-Sheng Chen, Chun-Wei Chen, and Manish Chhowalla
Abstract: Blue photoluminescence from chemically derived graphene oxide Goki Eda, Yun-Yue Lin, Cecilia Mattevi, Hisato Yamaguchi, Hsin-An Chen, I-Sheng Chen, Chun-Wei Chen, and Manish Chhowalla 1 Department of Materials, Imperial College, Exhibition Road, London SW7 2AZ, UK. 2 Department of Materials Science and Engineering, Rutgers University 607 Taylor Road, Piscataway, NJ 08854, USA. 3 Department of Materials Science and Engineering, National Taiwan University No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan.

1,655 citations

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TL;DR: The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed in this article.
Abstract: Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

1,535 citations

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TL;DR: A review of the field of biosensors can be found in this article, where the authors discuss the reasons for success, some of the more exciting emerging technologies, and speculates on the importance of sensors as a ubiquitous technology of the future for health and the maintenance of wellbeing.
Abstract: This review is based on the Theophilus Redwood Medal and Award lectures, delivered to Royal Society of Chemistry meetings in the UK and Ireland in 2012, and presents a personal overview of the field of biosensors. The biosensors industry is now worth billions of United States dollars, the topic attracts the attention of national initiatives across the world and tens of thousands of papers have been published in the area. This plethora of information is condensed into a concise account of the key achievements to date. The reasons for success are examined, some of the more exciting emerging technologies are highlighted and the author speculates on the importance of biosensors as a ubiquitous technology of the future for health and the maintenance of wellbeing.

1,160 citations

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TL;DR: In this paper, the kinds of polymers that are used, where and how polymer materials are used and the challenges to overcome in developing flexible displays are discussed and discussed in detail.

859 citations