Papers by Tatiana Kaydanova
We report on the pulsed laser deposition (PLD) of Mo-doped indium oxide (IMO) films with mobiliti... more We report on the pulsed laser deposition (PLD) of Mo-doped indium oxide (IMO) films with mobilities of up to 125 cm2/Vsec. Films have been grown from targets with 1-4 wt.% molybdenum. The optimum electrical and optical properties were obtained with the 2% target and yielded a maximum conductivity of 3717 S/cm with mobilities of 99 cm2/V-sec on (100) yttria stabilized zirconia (YSZ) single crystal substrates. Films also exhibit greater than 90% transparency in the visible range. Compared to commercial indium tin oxide (ITO) films, these PLD-grown IMO films have similar conductivity but since they have substantially higher mobility they have a correspondingly lower carrier concentration. The lower carrier concentration should extend the infrared window of the transparency for films of the same conductivity. This may lead to improved performance in a number of applications requiring improved performance TCOs.
IEEE Transactions on Microwave Theory and Techniques, 2007
Design of tunable Gunn diode-based active antenna module including a new type of planar dielectri... more Design of tunable Gunn diode-based active antenna module including a new type of planar dielectric resonator (PDR) tuned by a ferroelectric (FE) varactor is presented. The module is designed in such a way that the PDR acts both as a stabilizing resonator and as a radiator. Microwave properties of FE elements used for voltage-controlled oscillator (VCO) tuning are considered. The
Applied Physics Letters, 2004
We report the deposition of single-phase undoped and Ca-doped CuInO2 thin films from a readily sy... more We report the deposition of single-phase undoped and Ca-doped CuInO2 thin films from a readily synthesized source target of Cu2In2O5—circumventing the very difficult fabrication of CuInO2 targets. X-ray diffraction shows that single-phase materials were obtained over a range of substrate temperatures and deposition pressures. p-type conductivities are measured to be ∼3×10−3 S∕cm, comparable to the best films previously reported. The optical properties of the films were measured by spectroscopic ellipsometry.
P-type transparent conductive oxides would have potential applications in photovoltaics, transpar... more P-type transparent conductive oxides would have potential applications in photovoltaics, transparent electronics and organic opto-electronics. In this paper we present results on the synthesis of Cu 2 SrO 2 , a p-type transparent conducting oxide, by a chemical solution route as well as the conventional pulse laser deposition (PLD) method. For Cu 2 SrO 2 by the chemical solution route, samples were made by spraying deposition on quartz substrates using an aqueous solution of Copper formate and Strontium acetate. Phase pure materials were obtained by an optimum two stage annealing sequence. This initial work led to the development of good quality homogeneous films by a related sol-gel approach. We have also used pulsed laser depostion (PLD) to deposit Cu 2 SrO 2 and CuInO 2 thin films on quartz substrates. We have obtained improved conductivities in the CuInO 2 thin films over previously published work. We present details on the nature of the relationship of process parameters to the opto-electronic properties of the films.
DOE Scientific and Technical Information. DOE Scientific and Technical Information. ...
Applied Physics Letters, 2004
ABSTRACT
Applied Physics Letters, 2007
Significant difference in the capacitance tunability of paraelectric state ferroelectric capacito... more Significant difference in the capacitance tunability of paraelectric state ferroelectric capacitors under dc and pulse voltages is demonstrated. Along with a fast tuning (tau=100 s) responsible for up to ~30% variation of the capacitance were observed. The observed effect is a main obstacle for application of paraelectric state ferroelectrics on microwaves.
Polymers
Polyester nanocomposites reinforced with graphene nanoplatelets (GnPs) with two different lateral... more Polyester nanocomposites reinforced with graphene nanoplatelets (GnPs) with two different lateral sizes are prepared by high shear mixing, followed by compression molding. The effects of the size and concentration of GnP, as well as of the processing method, on the electrical conductivity and electromagnetic interference (EMI) shielding behavior of these nanocomposites are experimentally investigated. The in-plane electrical conductivity of the nanocomposites with larger-size GnPs is approximately one order of magnitude higher than the cross-plane volume conductivity. According to the SEM images, the compression-induced alignments of GnPs is found to be responsible for this anisotropic behavior. The orientation of the small size GnPs in the composite is not influenced by the compression process as strongly, and consequently, the electrical conductivity of these nanocomposites exhibits only a slight anisotropy. The maximum EMI shielding effectiveness (SE) of 27 dB (reduction of 99.8%...
In this work, NanoXplore’s proprietary graphene nanoplatelets, heXo-G V20, are melt-extruded into... more In this work, NanoXplore’s proprietary graphene nanoplatelets, heXo-G V20, are melt-extruded into thermoplastics LLDPE, HDPE and TPU. Graphene is shown to effectively increase the stiffness and the strength of a matrix TPU. The flexural and tensile moduli increase with loading levels of graphene whereas the tensile strength increases at low loading levels, but does not further increase at higher graphene concentrations. A ten fold increase in thermal conductivity was achieved by adding heXo-G V20 graphene to LLDPE matrix. The thermal conductivity percolation threshold was reached at 10% loading. At 1% loading of graphene the onset of the decomposition temperature and maximum weight loss temperatures were shifted by about 50°C, significantly improving the thermal stability of the PE matrix. Fourteen orders of magnitude increase in electrical conductivity of HDPE was obtained at 30% loading of graphene. Excellent EMI shielding of 40 dB was achieved with 20 wt% addition of graphene in ...
Carbon Trends
Abstract Water vapour condensation is frequently used as an effective means of transferring heat ... more Abstract Water vapour condensation is frequently used as an effective means of transferring heat using dropwise condensation on non-wetting surfaces. The rate of heat transfer can be enhanced with dropwise condensation on non-wetting hydrophobic and superhydrophobic surfaces when compared to filmwise condensation on a wetting surface. Since low surface energy materials are mostly polymeric with low durability and poor thermal conductivity, copper-graphene nanoplatelet (Cu-GNP) composite coatings are developed in this work using atmospheric plasma spray (APS) and high-velocity oxy-fuel (HVOF) as versatile and scalable surface engineering techniques. It is demonstrated that by adjusting the deposition parameters, it is possible to preserve the GNPs in the coating structure. After treating with a stearic acid solution, the coatings demonstrate superhydrophobicity and extreme water repelling behavior with a water contact angle of 164° and sliding angle of 1°. Raman analysis confirmed the presence of GNP in the coating with minimal defects. It is shown that the HVOF Cu-GNP coating developed in this work can improve the corrosion resistance up to 89% when compared to the uncoated Cu surface. This coating can potentially promote dropwise condensation while offering enhanced corrosion stability.
We report on the pulsed laser deposition (PLD) of Mo-doped indium oxide (IMO) films with mobiliti... more We report on the pulsed laser deposition (PLD) of Mo-doped indium oxide (IMO) films with mobilities of up to 125 cm2/Vsec. Films have been grown from targets with 1-4 wt.% molybdenum. The optimum electrical and optical properties were obtained with the 2% target and yielded a maximum conductivity of 3717 S/cm with mobilities of 99 cm2/V-sec on (100) yttria stabilized zirconia (YSZ) single crystal substrates. Films also exhibit greater than 90% transparency in the visible range. Compared to commercial indium tin oxide (ITO) films, these PLD-grown IMO films have similar conductivity but since they have substantially higher mobility they have a correspondingly lower carrier concentration. The lower carrier concentration should extend the infrared window of the transparency for films of the same conductivity. This may lead to improved performance in a number of applications requiring improved performance TCOs.
Ag, Cu, and Ni metallizations were inkjet printed with near vacuum deposition quality. The approa... more Ag, Cu, and Ni metallizations were inkjet printed with near vacuum deposition quality. The approach developed can be easily extended to other conductors such as Pt, Pd, Au, etc. Thick highly conducting lines of Ag and Cu demonstrating good adhesion to glass, Si, and printed circuit board (PCB) have been printed at 100-200 deg C in air and N2 respectively.
We are developing inkjet printing as a low cost, high throughput approach to the deposition of fr... more We are developing inkjet printing as a low cost, high throughput approach to the deposition of front contacts for Si solar cells. High deposition rates of 1µm per printing pass were achieved with a new metalorganic ink composed of silver(trifluoroacetate) in ethylene glycol. The printing conditions were optimized to achieve a relatively high line resolution of 120 µm. The optimal parameters for the piezoelectric inkjet were a pulse frequency of 50 Hz and pulse amplitude of 25 V. The best resolution and the line quality were achieved at a substrate temperature of 180 °C and drop separation of 40 µm.
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Papers by Tatiana Kaydanova