Showing papers in "ECS Journal of Solid State Science and Technology in 2012"
TL;DR: In this article, the incorporation of Gd into HfO2 thin films is shown to induce ferroelectricity, and a significant influence of electric field cycling on both polarization and small-signal capacitancevoltage measurements can be observed.
Abstract: The incorporation of Gd into HfO2 thin films is shown to induce ferroelectricity. A significant influence of electric field cycling on both polarization as well as small-signal capacitance-voltage measurements can be observed. X-ray diffraction measurements are supported by infrared absorption analysis and give further evidence of the previously proposed non-centrosymmetric transition phase of space group Pbc21.
186 citations
156 citations
TL;DR: In this article, integrated composites laboratory (ICL), Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, USA bDepartment of Chemistry and Biochemistry, Lamar U.S.A.
Abstract: aIntegrated Composites Laboratory (ICL), Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, USA bDepartment of Chemistry and Biochemistry, Lamar University, Beaumont, Texas 77710, USA cDepartment of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA dMicroscopy and Imaging Center and Materials Science and Engineering Program, Texas A&M University, College Station, Texas 77843, USA
87 citations
86 citations
TL;DR: In this paper, the authors have synthesized multiwalled carbon nanotubes (MWCNT)-TiO2 hybrid nanocoral thin films by hydrothermal route with titanium tetrachloride (TiCl4) and functionalized MWCNT as the precursor.
Abstract: We have synthesized multiwalled carbon nanotubes (MWCNT)-TiO2 hybrid nanocoral thin films by hydrothermal route with titanium tetrachloride (TiCl4) and functionalized MWCNT as the precursor. The new MWCNT-TiO2 hybrid nanocoral material was characterized by scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, Fourier Transform Raman spectroscopy (FT-Raman), X-ray diffraction (XRD), and X-Ray photoelectron spectroscopy (XPS) etc. The study indicates that the deposition process alters the typical structures of the nanocoral MWCNT-TiO2 hybrid material. The MWCNT-TiO2 hybrid film shows drastically changed morphology; i.e. the coral like morphology of TiO2 gets disturbed and transforms into compactly arranged spherical ball like particles with size ranging from ∼550‐650 nm. The MWCNT‐TiO2 hybrid thin film exhibit high photocurrent density (0.693 mA/cm 2 ) and yields overall conversion efficiency (η )o f 2.37%.
70 citations
55 citations
TL;DR: In this article, a vanadium and tungsten mixed oxide was deposited onto glassy carbon substrates and used as pH sensor in extended gate field effect transistor (EGFET) devices.
Abstract: A vanadium and tungsten mixed oxide was deposited onto glassy carbon substrates and used as pH sensor in extended gate field effect transistor (EGFET) devices. WO3 at a molar ratio of about 5% was mixed with V2O5 by means of the sol-gel method. The main focus of this investigation was to determine the operation conditions for the best response of the device and to propose the mechanism involved in the sensor response. The use of either original or reused films were employed and the importance of the total volume of the starting solution was also examined. The time response of the V2O5/WO3-pH-EGFET sensor is due to a deprotonation mechanism of vanadium and tungsten oxide, similarly to a discharging capacitor. The loss of protons by the oxide film depends on the time it remains immersed in the buffer solution and this process is accelerated upon raising the pH value. The increase of the films fabrication volume reduces the importance of the changes of the surface charges compared to the charges of the bulk, leading to less sensitive and less stable sensor response. Therefore, the smaller the amount of material used, the better the sensing properties of the device.
52 citations
49 citations
47 citations
39 citations
TL;DR: In this article, Bhandari et al. proposed Advanced Copper Interconnects Application as an Adhesion-Enhancing Layer for Chemical Vapor Deposition of Cobalt Nitride and its service Email alerting click here in the box at the top right corner of the article or Receive free email alerts when new articles cite this article sign up
Abstract: 2012, Volume 1, Issue 5, Pages N79-N84. ECS J. Solid State Sci. Technol. Wang, Jean-Sebastien M. Lehn, Huazhi Li and Deo Shenai Harish B. Bhandari, Jing Yang, Hoon Kim, Youbo Lin, Roy G. Gordon, Qing Min Advanced Copper Interconnects Application as an Adhesion-Enhancing Layer for Chemical Vapor Deposition of Cobalt Nitride and its service Email alerting click here in the box at the top right corner of the article or Receive free email alerts when new articles cite this article sign up
TL;DR: In this paper, the authors used face off-axis sputtering to crystallize in situ-grown ITO films onto a polyethylene terephthalate (PET) substrate at 120˚ C. The process caused no mechanical damage to the substrate.
Abstract: Facial off-axis sputtering was used to crystallize in situ-grown ITO films onto a polyethylene terephthalate (PET) substrate at 120 ◦ C. The process caused no mechanical damage to the substrate. The 100-nm-thick crystalline ITO films showed a resistivity of about 4.2 × 10 −4 -cm and a transmittance of about 83% at a wavelength of 550 nm. The crystallized ITO films showed an improved mechanical durability compared with the amorphous ITO films. The integration of a 30-nm-thick amorphous SiO2 layer onto ITO/PET maintains the resistivity of the ITO films and exhibits an improvement in the transmittance of about 86% compared with the crystalline ITO films. The amorphous SiO2 layer did not adversely affect the mechanical durability of either the crystalline
IMEC1
TL;DR: In this article, the temperature dependence of atomic layer deposition (ALD) of Pt using (methylcyclopentadienyl)trimethylplatinum, (MeCp)PtMe3, precursor and O2 are presented, based on a study of reaction products by time-resolved quadrupole mass spectrometry (QMS) measurements.
Abstract: Insights into the temperature dependence of atomic layer deposition (ALD) of Pt using (methylcyclopentadienyl)trimethylplatinum, (MeCp)PtMe3, precursor and O2 are presented, based on a study of reaction products by time-resolved quadrupole mass spectrometry (QMS) measurements. Above 250°C, Pt ALD proceeds through unhindered O2 dissociation at the Pt surface, inducing complete and instantaneous combustion of the precursor ligands. Quantification of the QMS data revealed that at 300°C, approximately 20% of the C-atoms react during the precursor pulse, forming mainly CH4 (~18%) balanced by CO2 (~2%). The remaining 80% of the C-atoms are combusted during the O2 pulse. Time-resolved data indicated that the combustion reactions compete with the hydrogenation reactions for the available surface carbon. Combustion reactions were found to be dominant, provided that a sufficient amount of chemisorbed oxygen is available. When the temperature drops below 250°C, deposition becomes hindered by the presence of a carbonaceous surface layer of partially fragmented and dehydrogenated precursor ligands, formed during the precursor pulse. The carbonaceous layer limits dissociative chemisorption of O2 and hence combustion reactions (leading to CO2) whereas reduced surface reactivity also limits (de-)hydrogenation reactions (leading to CH4). Below 100°C, the carbonaceous layer fully prevents O2 dissociation and ALD of Pt cannot proceed.
TL;DR: In this article, the diameter of the resulting ZnO nanowires varies from 50 nm to 300 nm upon increasing the separation distance, between the substrate and the Zn powder source, from 12 cm to 16 cm.
Abstract: morphology, structure and photoluminescence (PL) properties of the fabricated ZnO nanowires was evaluated. The diameter of the resulted nanowires varies from 50 nm to 300 nm upon increasing the separation distance, between the substrate and the Zn powder source, from 12 cm to 16 cm. The EDX and XRD results showed that the zinc to oxygen ratio and the crystallinity of the fabricated nanowires are dependent on the substrate position. Also, the ratio of the UV to visible emission peaks of the fabricated ZnO nanowires was found to be strongly dependent on the substrate position. The PL spectra showed the enhancement in UV emissions for the samples fabricated on the substrate farther away from the Zn source with enhanced near band-edge emission for thicker nanowires. A possible mechanism for the growth of ZnO nanowires is discussed.
TL;DR: In this paper, the effect of carbon concentration on the crystalline phase and dielectric constant (k) of atomic layer deposited HfO2 films on Ge substrate was investigated.
Abstract: The effect of the carbon concentration on the crystalline phase and dielectric constant (k) of atomic layer deposited HfO2 films on Ge substrate was investigated. After annealing, the HfO2 films grown at 200 ◦ C and 280 ◦ C were crystallized to the tetragonal (t )a nd monoclinic (m) phases, respectively, which was related to the carbon contents within the films and grain boundary energy. To clarify this, the energy difference between a t -a nd am- phases (�E tetra) was calculated by first principles calculations. The higher k value
TL;DR: YBO3:Ce3+,Tb3+ phosphor was prepared from rare earth oxides and boric acid by a solid state reaction as discussed by the authors, which absorbs near UV light through 4f-5d transitions of Ce3+, followed by broad emissions through 5d-4f transitions of Tb3+.
Abstract: YBO3:Ce3+,Tb3+ phosphor was prepared from rare earth oxides and boric acid by a solid state reaction. The phosphor absorbs near UV light through 4f–5d transitions of Ce3+, followed by broad emissions through 5d–4f transitions of Ce3+ and sharp emissions through 4f–4f transitions of Tb3+. Spectroscopic investigations for samples with various Ce3+ and Tb3+ concentrations reveal nonradiative energy transfer from Ce3+ to Tb3+. Emission color of the YBO3:Ce3+,Tb3+ varies from blue (0.163, 0.019) to green (0.321, 0.585) depending on the Ce3+ and Tb3+ concentrations. The optimized green-emitting Y0.82Ce0.03Tb0.15BO3 phosphor has an emission color of (0.309, 0.547) with an external quantum efficiency of 76.7%. The photoluminescence intensity of this phosphor at 150°C keeps 87% of its intensity at room temperature, showing sufficient thermal stability for white light emitting diode applications.
TL;DR: In this paper, the formation of very thin graphene-like nanosheets of ZnO was confirmed from a photoluminescence study, which showed the presence of a narrow and sharp band edge emission at 360 nm and a weak defect related emission peak in the visible region.
Abstract: HerewereportalowcostelectrochemicalaqueoussolutionmethodforsynthesisofhighqualitytwodimensionalflatZnOnano-sheets using standard home use microwave-oven. Independent studies by field emission scanning electron microscopy and high resolution transmission electron microscopy confirm the formation of very thin graphene-like nanosheets of ZnO. The high quality of the sheets is confirmed from a photoluminescence study, which shows the presence of a narrow and sharp band edge emission at 360 nm and the presence of a weak defect related emission peak in the visible region. The conductivity of the nanosheets increases dramatically upon illumination of UV lights as compared to the dark condition. The better crystal quality and excellent photo conductivity ensure these ZnO nanosheets can be used as potential UV detector. It is also found that both response and recovery times of ZnO nano-sheets are very fast and are comparable to those of nanowires and nanorods.
TL;DR: In this paper, the polymer resin used in this research is the novalac type of phenolic resin in powder form with 60 μ ms ize and has been purchased from Resitan Co. Ltd.
Abstract: Experimental Materials.— The polymer resin used in this research is the novalac type of phenolic resin in powder form with 60 μ ms ize and has been purchased from Resitan Co. Ltd. The G powder has been purchased from Merck Co. Ltd., containing size <50 μm and the bulk density of 20‐30 g/(100 mL). The expandable graphite and CF have been purchased from Qingdao Yanxin Graphite Products Co., Ltd and Highborn International Co., Ltd, respectively. The CF cloth used in preparing the final composite has been purchased from Torrey Co. Elongation, elastic module, and maximum strength of CF cloth is 10%, 824MPa, and 190 MPa, respectively.
TL;DR: In this article, the authors investigated the effect of temperature on the optical bandgap of amorphous In-Ga-Zn-O thin films (∼250 nm thickness) deposited by radio-frequency magnetron sputtering.
Abstract: Westudiedtheeffectsofsubstratetemperature(Ts)onthesurfaceroughness,resistivity(ρ),mobility(μ),chargecarrierconcentrations (n), transmission and optical bandgap (Eg) of amorphous In-Ga-Zn-O thin films (∼250 nm thickness) deposited by radio-frequency magnetron sputtering. As Ts increased from RT to 300 ◦ C, n increased (2.6 × 10 19 → 5.0 × 10 19 /cm 3 ), ρ decreased (7.0 × 10 −3 → 4.7 × 10 −3 � −cm), and Eg (3.9 → 3.7 eV) along with the average transmission (89 → 82%) in the visible region decreased. Investigation of the O 1s core level and the Ga 3d ,I n 4d ,a nd Zn 3d shallow-core levels spectra obtained by high-resolution X-ray photoelectron spectroscopy revealed that as Ts increased, an O 1s component representing the oxygen vacancies increased in amount and that the intensity ratio of In/Ga increased but that of Zn/Ga decreased. The analysis suggests that the increase of oxygen vacancies could explain the increase of charge carrier concentration and that the compositional change could explain the change of Eg.
TL;DR: In this paper, the effect of surface states and point defects of single-crystal β-Ga2O3 epilayers before and after annealing was studied using room temperature Photoluminescence (PL) and I-V characteristics (dark current).
Abstract: MOCVD-grown single-crystal β-Ga2O3 epilayers on (0001) sapphire substrates were developed at low temperature and low pressure. As-grown β-Ga2O3 epilayers were post-annealed at different temperatures in the atmosphere. Crystalline structure and quality of epilayers, tracked by X-ray diffraction (XRD), remained almost unchanged after post-annealing. Effect of surface states and point defects of β-Ga2O3 epilayers before and after annealing are studied using room temperature Photoluminescence (PL) and I-V characteristics (dark current). The significant difference in PL property and dark current before and after annealing is attributed to healing of the surface states and point defects, as β-Ga2O3 is known for its high density of oxygen vacancies. Post-annealing single-crystal β-Ga2O3 epilayers at high temperature makes the healing possible, probably due to oxygen diffusion and surface band bending. A significant healing of surface states and point defects in single-crystal β-Ga2O3 indicates its high potential in fabrication of optoelectronic devices.
TL;DR: In this article, the authors evaluated CdTe solar cells with back contacts formed by either (i) 15nm Cu evaporation followed by application of carbon conductive paste embedded with micron sized Cu particles in ZnTe powder and (ii) only with the above mentioned conducting paste, were evaluated.
Abstract: CdTe solar cells with back contacts formed by either (i) 15nm Cu evaporation followed by application of carbon conductive paste embedded with micron sized Cu particles in ZnTe powder and (ii) only with the above mentioned conducting paste, were evaluated. A Cu-related deep level defect with an activation energy of Ea ∼ 0.57 eV was observed for Cu evaporated back contact cells and an intrinsic defect with an activation energy Ea ∼ 0.89 eV was found for cells prepared only by ZnTe:Cu embedded carbon paste. Frequency dispersion in C-V measurements confirms the presence of Cu-related deep level traps for cells with Cu evaporated back contact whereas no such defects were observed in carbon paste contact. The behavior was believed to be due to diffusion of excess Cu from the contact. It was further observed that majority carrier deep level traps (Cu-related or intrinsic) contribute differently to the degradation of electronic properties of the CdTe solar cells.