Publications (21) View all
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Article: Synthesis of uniformly dispersed anatase nanoparticles inside mesoporous silica thin films via controlled breakup and crystallization of amorphous TiO2 deposited using atomic layer deposition.
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ABSTRACT: Amorphous titanium dioxide was introduced into the pores of mesoporous silica thin films with 75% porosity and 12 nm average pore diameter via Atomic Layer Deposition (ALD) using alternating pulses of tetrakis(dimethylamino)titanium and water. Calcination provoked fragmentation of the deposited amorphous TiO2 phase and its crystallization into anatase nanoparticles inside the nanoporous film. The narrow particle size distribution of 4 ± 2 nm and the uniform dispersion of the particles over the mesoporous silica support were uniquely revealed using electron tomography. These anatase nanoparticle bearing films showed photocatalytic activity in methylene blue degradation. This new synthesis procedure of the anatase nanophase in mesoporous silica films using ALD is a convenient fabrication method of photocatalytic coatings amenable to application on very small as well as very large surfaces.Nanoscale 05/2013; · 5.91 Impact Factor -
Article: Selective and reversible ammonia gas detection with nanoporous film functionalized silicon photonic micro-ring resonator.
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ABSTRACT: Portable, low cost and real-time gas sensors have a considerable potential in various biomedical and industrial applications. For such applications, nano-photonic gas sensors based on standard silicon fabrication technology offer attractive opportunities. Deposition of high surface area nano-porous coatings on silicon photonic sensors is a means to achieve selective, highly sensitive and multiplexed gas detection on an optical chip. Here we demonstrate selective and reversible ammonia gas detection with functionalized silicon-on-insulator optical micro-ring resonators. The micro-ring resonators are coated with acidic nano-porous aluminosilicate films for specific ammonia sensing, which results in a reversible response to NH(3)with selectivity relative to CO(2). The ammonia detection limit is estimated at about 5 ppm. The detectors reach a steady response to NH(3) within 30 and return to their base level within 60 to 90 seconds. The work opens perspectives on development of nano-photonic sensors for real-time, non-invasive, low cost and light weight biomedical and industrial sensing applications.Optics Express 05/2012; 20(11):11855-62. · 3.59 Impact Factor -
Article: The effects of deposition temperature and ambient on the physical and electrical performance of DC-sputtered n-ZnO/p-Si heterojunction
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ABSTRACT: The effects of deposition conditions on the physical and electrical performance of the n-ZnO/p-Si heterojunction were systematically investigated. ZnO films were deposited on the Si and glass substrates using direct current (DC) magnetron sputtering with various ambients and substrate temperatures. The results showed that increasing the O2 content and substrate temperature during the deposition process could improve the crystallinity and stoichiometry of the ZnO film, resulting in a lower carrier concentration and higher resistivity. The electrical properties of the n-ZnO/p-Si heterojunctions were also affected by the deposition parameters. For the junctions fabricated in the pure Ar ambient, the sample deposited at room temperature (RT) showed Ohmic behavior, while the one deposited at 300 °C exhibited poor rectifying behavior. On the other hand, the junctions fabricated in the O2/Ar ambient possessed ideal rectifying behaviors. The different carrier transport mechanisms for the heterojunctions under forward and reverse bias were systematically studied using a high temperature current–voltage (I-V) measurement. The recombination-tunneling current showed temperature insensitive performance while the space-charge limited current (SCLC) changed with the measurement temperature.Applied Physics A 04/2012; 98(2):357-365. · 1.63 Impact Factor -
Article: In situ monitoring of atomic layer deposition in nanoporous thin films using ellipsometric porosimetry.
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ABSTRACT: Ellipsometric porosimetry (EP) is a handy technique to characterize the porosity and pore size distribution of porous thin films with pore diameters in the range from below 1 nm up to 50 nm and for the characterization of porous low-k films especially. Atomic layer deposition (ALD) can be used to functionalize porous films and membranes, e.g., for the development of filtration and sensor devices and catalytic surfaces. In this work we report on the implementation of the EP technique onto an ALD reactor. This combination allowed us to employ EP for monitoring the modification of a porous thin film through ALD without removing the sample from the deposition setup. The potential of in situ EP for providing information about the effect of ALD coating on the accessible porosity, the pore radius distribution, the thickness, and mechanical properties of a porous film is demonstrated in the ALD of TiO(2) in a mesoporous silica film.Langmuir 02/2012; 28(8):3852-9. · 4.19 Impact Factor -
Article: Annealing induced hysteresis suppression for TiN/HfO2/GeON/p-Ge capacitor
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ABSTRACT: In this paper the annealing effects in N2 on the electrical characteristics of a TiN/HfO2/GeON/p-Ge capacitor are investigated. Well behaved capacitance–voltage curves were obtained for the sample annealed at 400 °C for 3 min in N2. A negligible hysteresis was demonstrated comparing with a hysteresis of 0.5 V for the as-deposited sample. The suppression of hysteresis is attributed to the reduction of electron traps in the dielectric layer, which is verified by the MOS pulse method. Besides, the interface states' density is also greatly reduced by annealing in N2 and confirmed by the conductance method.Semiconductor Science and Technology 10/2011; 26(12):125003. · 1.72 Impact Factor
