Customer Papers
This is a searchable database of papers written by our customers, using Cambridge NanoTech systems. If you are publishing a paper based on research done on a Cambridge NanoTech ALD system, please contact us. We would be pleased to include it in our database.Showing customer papers 1-10 of 249 Next
| LINK | Ondersma, J. W.; Hamann, T. W. |
| "Impedance Investigation of Dye-Sensitized Solar Cells Employing Outer-Sphere Redox Shuttles" | |
| Journal of Physical Chemistry C, 2010, 114, 638-645 | |
| Abstract: | Electrochemical impedance spectroscopy was used to investigate dye-sensitized solar cells (DSSCs) employing outer-sphere redox shuttles. A three-electrode cell was used to overcome limitations associated with a high charge transfer resistance at the counter electrode, accurately compare alumina coated and bare photoanodes, and compare DSSCs with different solution potentials. The effect of an alumina coating, which has been shown to improve the performance of such DSSCs, was determined by comparisons of the chemical capacitance, charge transport and charge recombination. Contrary to previous reports and our expectations, no evidence of recombination from surface states was observed at any potential range for either coated or uncoated electrodes, further confirmed with open circuit voltage decay measurements. Instead, even a single atomic layer deposition cycle of alumina acts as a tunneling barrier layer, which produces the decrease in recombination rate of electrons from the TiO2 to the oxidized redox shuttle. Impedance measurement results allowed calculation of charge transport times and lifetimes for DSSCs employing a series of cobalt bipyridyl redox shuttles. Comparisons of these transport times and lifetimes produce estimates of the effective charge diffusion lengths. The relative diffusion lengths are in excellent agreement with the photovoltaic response of the DSSCs studied; however, the magnitude appears to be a slight overestimate. |
| Address: | Hamann, TW Michigan State Univ, Dept Chem, E Lansing, MI 48824 USA Michigan State Univ, Dept Chem, E Lansing, MI 48824 USA Michigan State Univ, Dept Chem, E Lansing, MI 48824 USA |
| LINK | Pitzschel, K.; Moreno, J. M. M.; Escrig, J.; Albrecht, O.; Nielsch, K.; Bachmann, J. |
| "Controlled Introduction of Diameter Modulations in Arrayed Magnetic Iron Oxide Nanotubes" | |
| ACS Nano, 2009, 3, 3463-3468 | |
| Abstract: | To date, no large-scale preparative method for arrays of nanotube enables the experimentalist to arbitrarily define changes in the tubes\' diameter along their length. To this goal, we start with anodic alumina substrates displaying controlled modulations in pore diameter obtained by alternating \"mild\" and \"hard\" electrochemical etching conditions. We then utilize atomic layer deposition (ALD) to coat the internal pore walls with conformal layers of an oxide. Ferromagnetic Fe3O4 tubes of 10 nm wall thickness and 10-30 mu m in length are thus prepared, which replicate the modulated silhouette of the template. Their magnetic properties strongly depend on the presence of diameter modulations. Introducing one or several very short segments of large diameter (150 nm) into an otherwise thin tube (70 nm diameter) brings its initially large coercive field down to a value close to the case of a homogeneously thick tube. Theoretical modeling emphasizes the major influence of the magnetostatic interactions between neighboring tubes. They are enhanced locally at the sites of diameter modulations, which directly translates into a reduction in coercive field. |
| Address: | Bachmann, J Univ Hamburg, Inst Appl Phys, Hamburg, Germany Univ Hamburg, Inst Appl Phys, Hamburg, Germany Univ Hamburg, Inst Appl Phys, Hamburg, Germany Univ Barcelona, Dept Quim Fis, Electrodep, E-08028 Barcelona, Spain Univ Santiago Chile, Dept Fis, Santiago, Chile |
| LINK | Prasittichai, C.; Hupp, J. T. |
| "Surface Modification of SnO2 Photoelectrodes in Dye-Sensitized Solar Cells: Significant Improvements in Photovoltage via Al2O3 Atomic Layer Deposition" | |
| Journal of Physical Chemistry Letters, 2010, 1, 1611-1615 | |
| Abstract: | We report here the exploitation of ultrathin layers of Al2O3 deposited via atomic layer deposition (ALD) on SnO2 photoanodes used in dye-sensitized solar cells featuring the I-3(-)/I- couple as the redox electrolyte. We find that a single ALD cycle of Al2O3 increases the lifetimes of injected electrons by more than 2 orders of magnitude. The modified SnO2 photoanode yields nearly a 2-fold improvement fill factor and a greater than 2-fold increase in open circuit photo voltage, with a slight increase in short-circuit photocurrent. The overall energy conversion efficiency increases by roughly 5-fold. The effects appear to arise primarly from passivation of reactive, low-energy tin oxide surface states, with band edge shifts and tunneling based blocking behavior playing only secondary roles. |
| Address: | Hupp, JT Northwestern Univ, Dept Chem, 2145 Sheridan Rd, Evanston, IL 60208 USA Northwestern Univ, Dept Chem, 2145 Sheridan Rd, Evanston, IL 60208 USA Northwestern Univ, Dept Chem, Evanston, IL 60208 USA Northwestern Univ, ANSER Ctr, Evanston, IL 60208 USA Argonne Natl Lab, Argonne, IL 60439 USA |
| LINK | Robinson, J. A.; LaBella, M.; Trumbull, K. A.; Weng, X. J.; Cavelero, R.; Daniels, T.; Hughes, Z.; Hollander, M.; Fanton, M.; Snyder, D. |
| "Epitaxial Graphene Materials Integration: Effects of Dielectric Overlayers on Structural and Electronic Properties" | |
| ACS Nano, 2010, 4, 2667-2672 | |
| Abstract: | We present the integration of epitaxial graphene with thin film dielectric materials for the purpose of graphene transistor development. The impact on epitaxial graphene structural and electronic properties following deposition of Al2O3, HfO2, TiO2, and Ta2O3 varies based on the choice of dielectric and deposition parameters. Each dielectric film requires the use of a nucleation layer to ensure uniform, continuous coverage on the graphene surface. Graphene quality degrades most severely following deposition of Ta2O3, while the deposition if TiO2 appears to improve the graphene carrier mobility. Finally, we discuss the potential of dielectric stack engineering for improved transistor performance. |
| Address: | Robinson, JA Penn State Univ, Ctr Electroopt, University Pk, PA 16802 USA Penn State Univ, Ctr Electroopt, University Pk, PA 16802 USA Penn State Univ, Ctr Electroopt, University Pk, PA 16802 USA Penn State Univ, Dept Mat Sci |
| LINK | Shanmugam, M.; Baroughi, M. F.; Galipeau, D. |
| "Effect of atomic layer deposited ultra thin HfO2 and Al2O3 interfacial layers on the performance of dye sensitized solar cells" | |
| Thin Solid Films, 2010, 518, 2678-2682 | |
| Abstract: | The objective of this work was to investigate the improvement in performance of dye sensitized solar cells (DSSCs) by depositing ultra thin metal oxides (hafnium oxide (HfO2) and aluminum oxide (Al2O3)) on mesoporous TiO2 photoelectrode using atomic layer deposition (ALD) method. Different thicknesses of HfO2 and Al2O3 layers (5, 10 and 20 ALD cycles) were deposited on the mesoporous TiO2 surface prior to dye loading process used for fabrication of DSSCs. It was observed that the ALD deposition of ultrathin oxides significantly improved the performance of DSSCs and that the improvement in the DSSC performance depends on the thickness of the deposited HfO2 and Al2O3 films. Compared to a reference DSSC the incorporation of a HfO2 layer resulted in 69% improvement (from 4.2 to 7.1%) in the efficiency of the cell and incorporation of Al2O3 (20 cycles) resulted in 19% improvement (from 4.2 to 5.0%) in the efficiency of the cell. These results suggest that ultrathin metal oxide layers affect the density and the distribution of interface states at the TiO2/organic dye and TiO2/liquid electrolyte interfaces and hence can be utilized to treat these interfaces in DSSCs. (C) 2009 Elsevier B.V. All rights reserved. |
| Address: | Baroughi, MF S Dakota State Univ, Dept Elect Engn |
| LINK | Shim, J. H.; Chao, C. C.; Huang, H.; Prinz, F. B. |
| "Atomic layer deposition of yttria-stabilized zirconia for solid oxide fuel cells" | |
| Chemistry of Materials, 2007, 19, 3850-3854 | |
| Abstract: | Yttria-stabilized zirconia ( YSZ) films were synthesized by atomic layer deposition ( ALD). Tetrakis( dimethylamido)zirconium and tris( methylcyclopentadienyl) yttrium were used as ALD precursors with distilled water as oxidant. From X-ray photoelectron spectroscopy ( XPS) compositional analysis, the yttria content was identified to increase proportionally to the pulse ratio of Y/Zr. Accordingly, the target stoichiometry ZrO2/Y2O3) 0.92:0.08 was achieved. Crystal and grain structures of ALD YSZ films grown on amorphous Si3N4 were analyzed by X-ray diffraction ( XRD) and atomic force microscopy ( AFM). The microstructure of the polycrystalline films consisted of grains of tens of nanometers in diameter. To evaluate ALD YSZ films as oxide ion conductor, freestanding 60 nm films were prepared with porous platinum electrodes on both sides of the electrolyte. This structure served as a solid oxide fuel cell designed to operate at low temperatures. Maximum power densities of 28 mW/cm(2), 66 mW/ cm(2), and 270 mW/ cm2 were observed at 265 degrees C, 300 degrees C, and 350 degrees C, respectively. The high performance of thin film ALD electrolyte fuel cells is related to low electrolyte resistance and fast electrode kinetics. The exchange current density at the electrode-electrolyte interface was approximately 4 orders of magnitude higher compared to reference Pt-YSZ values. |
| Address: | Shim, JH Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA Stanford Univ, Dept Mat Sci |
| LINK | Teh, E. J.; Leong, Y. K.; Liu, Y. N.; Craig, V. S. J.; Walsh, R. B.; Howard, S. C. |
| "High Yield Stress Associated with Capillary Attraction between Alumina Surfaces in the Presence of Low Molecular Weight Dicarboxylic Acids" | |
| Langmuir, 2010, 26, 3067-3076 | |
| Abstract: | Adsorbed low molecular weight charged molecules are known to give rise to a range of surface forces that affect the rheological behavior of oxide dispersions. The behavior of dicarboxylic acid bolaform compounds in alumina Slurry was investigated to determine the influence of the molecular Structure oil the nanoscale interactions between alumina Surfaces and on the macroscopic properties of the slurry. The surface forces in dispersions and between a single particle and a flat surface were characterized by yield Stress and atomic force microscopy (AFM) respectively. Absorbed muconic acid increased the yield stress of the alumina system, which indicates an additional attractive interaction between the particles, Adsorbed trans,trans (TT) muconic acid resulted in a Much higher yield Stress than cis,cis (CC) muconic acid. Force-distance data obtained via AFM displayed features indicating the presence of a capillary force attraction it low pH between the alumina surfaces when TT and CC muconic acids were adsorbed at high surface coverage. This force appeared to explain the high yield stress at low pH (pH 3.6) but the absence of a net attractive force at higher pH (pH 5) did not correlate with the yield Stress results, At low pH, the muconic acids become less soluble in the confined space between the interacting surfaces resulting in the formation of an \"oily\" muconic acid phase located between the interacting surfaces. The nanosized \"oil\" phase is the source of the capillary force. |
| Address: | Craig, VSJ Australian Natl Univ, Dept Appl Math, Res Sch Phys |
| LINK | Tien, T. C.; Pan, F. M.; Wang, L. P.; Tsai, F. Y.; Lin, C. |
| "Coverage Analysis for the Core/Shell Electrode of Dye-Sensitized Solar Cells" | |
| Journal of Physical Chemistry C, 2010, 114, 10048-10053 | |
| Abstract: | In this study, we established a core/shell (C/S) model that evaluates the surface coverage of an overlayer deposited on nanoparticles in terms of X-ray photoelectron spectroscopy signals of the nanoparticles. We used the model to estimate the coverage of Al2O3 shell layers, which were deposited on the nanoporous TiO2 electrodes of dye-sensitized solar cells (DSSCs) by atomic layer deposition (ALD), as a function of the number of ALD reaction cycles. The surface coverage increased with the average thickness of the Al2O3 shell layers, indicating that the ALD Al2O3 deposition on the nanoporous electrode was via the island growth mode. The power conversion efficiency of the DSSCs was highest after the first ALD reaction cycle for the Al2O3 shell layers, which had a coverage of 0.25, according to the C/S model. The study shows that, to further improve the PCE, optimization of the ALD Al2O3 deposition condition is required so that the surface coverage of the shell layer can be increased at the first ALD reaction cycle. |
| Address: | Tien, TC Natl Chiao Tung Univ, Dept Mat Sci |
| LINK | Alessandri, I.; Zucca, M.; Ferroni, M.; Bontempi, E.; Depero, L. E. |
| "Tailoring the Pore Size and Architecture of CeO2/TiO2 Core/Shell Inverse Opals by Atomic Layer Deposition" | |
| Small, 2009, 5, 336-340 | |
| Abstract: | |
| Address: | Alessandri, I Univ Brescia, INSTM, Via Branze 38, I-25123 Brescia, Italy Univ Brescia, INSTM, Via Branze 38, I-25123 Brescia, Italy Univ Brescia, INSTM, I-25123 Brescia, Italy Univ Brescia, Chem Technol Lab, I-25123 Brescia, Italy Univ Brescia, CNR INFM, I-25123 Brescia, Italy Univ Brescia, Dept Chem |
| LINK | Katsia, E.; Huby, N.; Tallarida, G.; Kutrzeba-Kotowska, B.; Perego, M.; Ferrari, S.; Krebs, F. C.; Guziewicz, E.; Godlewski, M.; Osinniy, V.; Luka, G. |
| "Poly(3-hexylthiophene)/ZnO hybrid pn junctions for microelectronics applications" | |
| Applied Physics Letters, 2009, 94, - | |
| Abstract: | Hybrid poly(3-hexylthiophene)/ZnO devices are investigated as rectifying heterojunctions for microelectronics applications. A low-temperature atomic layer deposition of ZnO on top of poly(3-hexylthiophene) allows the fabrication of diodes featuring a rectification ratio of nearly 10(5) at /- 4 V and a current density of 10(4) A/cm(2). Electrical characteristics are discussed taking into account the chemical structure of the stack and the energy band diagram. |
| Address: | Katsia, E CNR INFM, Lab Nazl MDM, Via Olivetti 2, I-20041 Agrate Brianza, Italy CNR INFM, Lab Nazl MDM, Via Olivetti 2, I-20041 Agrate Brianza, Italy CNR INFM, Lab Nazl MDM, I-20041 Agrate Brianza, Italy Tech Univ Denmark, Riso Natl Lab Sustainable Energy, DK-4000 Roskilde, Denmark Polish Acad Sci, Inst Phys, PL-02668 Warsaw, Poland |
Showing customer papers 1-10 of 249 Next