bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of ZnO and poly‐Si in thin‐film heterostructures
Authors: Angelov Orlin , Nichev Hristo , Sendova‐Vassileva Marushka , Dimova‐Malinovska Doriana 
Published: May 2010

AbstractIn this work, thin‐film heterojunction is prepared using ZnO and poly‐Si thin films and its I–V characteristics are presented. ZnO thin films have been applied for device engineering in different heterostructures, as well. In this work, the I–V characteristics of a thin‐film heterostructure n‐ZnO/poly‐Si are studied. The ZnO polycrystalline films are deposited by RF sputtering in an atmosphere of Ar on the surface of a p‐type poly‐Si layer. The poly‐Si films are prepared on glass substrate by the method of aluminum‐induced crystallization (AIC) from precursor layers of Al and a‐Si:H. The Al and a‐Si:H precursor films are deposited by magnetron sputtering on glass substrate. The a‐Si:H film precursors contain 9 at% hydrogen. The isothermal annealing of the structure glass/Al/a‐Si:H is performed in forming gas (N2 + 5%H2) in the temperature range of 530–550 °C for 7 and 21 h. The properties of the films are studied by X‐ray diffraction (XRD), optical microscopy, optical transmission and reflection, and Raman spectroscopy. The I–V characteristics of the thin‐films heterostructure n‐ZnO/ poly‐Si show diode behavior and ideality factor of 2.95.The structure exhibits photosensitivity under illumination.
Detection of volatile organic compounds using a polythiophene derivative
Authors: Gonçalves V. C. , Nunes B. M. , Balogh D. T. , Olivati C. A. 
Published: May 2010

AbstractConjugated polymers have been subject of great interest in the recent literature from both fundamental point of view and applied science perspective. Among the several types of conjugated polymers used in recent investigations, polythiophene and its derivatives have attracted considerable attention over the past 20 years due to their high mobility and other remarkable solid‐state properties. They have potential applications in many fields, such as microelectronic devices, catalysts, organic field‐effect transistors, chemical sensors, and biosensors. They have been studied as gas and volatile organic compounds (VOCs) sensors using different principles or transduction techniques, such as optical absorption, conductivity, and capacitance measurements. In this work, we report on the fabrication of gas sensors based on a conducting polymer on an interdigitated gold electrode. We use as active layer of the sensor a polythiophene derivative: poly (3‐hexylthiophene) (P3HT) and analyzed its conductivity as response for exposure to dynamic flow of saturated vapors of six VOCs [n‐hexane, toluene, chloroform, dichloromethane, methanol, and tetrahydrofuran (THF)]. Different responses were obtained upon exposure to all VOCs, THF gave the higher response while methanol the lower response. The influence of moisture on the measurements was also evaluated.
Electrical characteristics of solution‐processed InGaZnO thin film transistors depending on Ga concentration
Authors: Kim Gun Hee , Jeong Woong Hee , Kim Hyun Jae 
Published: May 2010

AbstractWe investigated the role of Ga in solution‐processed InGaZnO thin film transistors (TFTs). The incorporation of Ga into a InZnO compound system results in a decrease in the carrier concentration of the films and an off‐current of TFTs. This is a result of the Ga ions forming stronger chemical bonds with oxygen, as compared to the Zn and In ions, acting as a carrier suppressor. It was verified, using X‐ray photoelectron spectroscopy (XPS), that the vacancy‐related oxygen 1s peak was decreased when the Ga content increased.
Effect of nitrogen doping on photoresponsivity of ZnO films
Authors: Ievtushenko A. I. , Lashkarev G. V. , Lazorenko V. I. , Karpyna V. A. , Dusheyko M. G. , Tkach V. M. , Kosyachenko L. A. , Sklyarchuk V. M. , Sklyarchuk O. F. , Avramenko K. A. , Strelchuk V. V. , Horvath Zs. J. 
Published: May 2010

AbstractInvestigations of photoelectrical properties of ZnO films are important scientific task for designing UV detectors for various applications. We report the positive role of nitrogen doping in increasing photoresponsivity of ZnO:N‐based detectors. It is suggested that nitrogen slightly deteriorates the structural quality of ZnO films and compensates intrinsic defects that increase photoresponsivity. Also, the spectral response of Ni/ZnO:N/n+‐Si structures at different biases were considered.magnified image
Atomic and electronic structures at ZnO and ZrO2 interface for transparent thin‐film transistors
Authors: Wang S. J. , Wong T. I. , Chen Q. , Yang M. , Wong L. M. , Chai J. W. , Zhang Z. , Pan J. S. , Feng Y. P. 
Published: May 2010

AbstractIn this paper, we report the studies of atomic and electronic structures at ZnO and ZrO2 interface. The epitaxial heterostructures were grown by laser molecular beam epitaxy and the interface atomic structure was determined by using high‐resolution transmission electron microscopy (TEM). Band alignment for high‐k ZrO2 layer on ZnO was investigated by in situ X‐ray photoemission spectroscopy (XPS) characterization and first‐principles calculations based on density functional theory (DFT). The valence and conduction band offsets (CBOs) were found to be 0.27 ± 0.05 eV and 2.16 ± 0.05 eV, respectively. The results are in good agreement with values from theoretical calculations. The large CBO and small lattice mismatch between ZnO and ZrO2 suggest potential for ZrO2 to be used as a gate dielectric in ZnO‐based transparent electronic devices.
Controllable crystallinity of synthesized In–Ga–Zn–O nano‐powder by using a pulp precursor for printing processes
Authors: Jung Chulho , Choi Min Suk , Choi Kwang Ho , Yoon Dae Ho 
Published: May 2010

AbstractIGZO nanoparticles were synthesized using a pulp processor at different temperatures and solution concentrations for the printing processes. The nanoparticles were characterized by field emission scanning electron microscopy (FESEM), powder X‐ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The nanoparticles synthesized in a 10% of solution were 10–20 nm in diameter. On the other hand, the nanoparticles synthesized in 1 and 0.1% solution were ∼10 nm in diameter, as revealed by HRTEM. From the powder XRD and HRTEM results, the crystallinity of the IGZO nanoparticles decreased with decreasing solution concentration. In particular, the crystallinity was affected significantly by the indium concentration.
Synthesis of light‐coloured nanoparticles of wide band gap p‐type semiconductors CuGaO2 and LaOCuS by low temperature hydro/solvothermal processes
Authors: Chavillon B. , Cario L. , Doussier‐Brochard C. , Srinivasan R. , Le Pleux L. , Pellegrin Y. , Blart E. , Odobel F. , Jobic S. 
Published: May 2010

AbstractWe report here two original low temperature routes for the synthesis of nanostructured particles of p‐type TCO's CuGaO2 and LaOCuS. Light grey CuGaO2 nanolayered particles (∼300 nm large and 5 nm thick) were prepared from a hydrothermal synthetic route using soluble hydrated metal nitrates as precursors and ethylene glycol (EG) as reducing agent. We found then that the initial pH of the precursor's solution is a key parameter to tune the particle sizes (from 2 µm to 300 nm) and subsequently the colour (from dark brown to light grey) of the CuGaO2 powder. LaOCuS was obtained for the first time as greyish nanolayered particles (∼100 nm large and 10 nm thick) via a solvothermal route in ethylene diamine with hydrate chloride lanthanum, copper mono oxide and elemental sulphur as precursors. We found that the control of the chloride lanthanum precursor hydration rate is of prime importance to achieve pure material and to tune the colour of the LaOCuS sample. Both CuGaO2 and LaOCuS nanolayered particles synthesized via these soft chemistry routes exhibit all the characteristics of transparent p‐type semiconductorsmagnified image
Optical properties of organic thin films deposited via organic vapour phase deposition
Authors: Laskarakis Argiris , Georgiou Despoina , Logothetidis Stergios 
Published: May 2010

AbstractIn recent years, organic semiconductors attracted a lot of attention due to their potential use in organic electronics such as light emitting diodes (OLEDs), photovoltaics and photodetectors. Tris‐(8‐hydroxyquinoline)‐aluminium(III) (Alq3) and N,N_‐di‐[(1‐naphthyl)‐N,N‐diphenyl]‐(1,1‐biphenyl)‐4,4‐diamine (α‐NPD) are among the most commonly used electron transport and hole‐transport materials in OLEDs, respectively. In this work, Alq3 and α‐NPD thin films with various thickness values were deposited onto Si and glass substrates by organic vapour phase deposition (OVPD). Spectroscopic Ellipsometry (SE) in a wide spectral region from the infrared (IR) (900–4000 cm−1) to the near infrared–visible–far ultraviolet (NIR–Vis–fUV, 0.7–6.5 eV) has been implemented in order to investigate the influence of the thickness on their optical and structural properties. From the analysis of the SE spectra, we estimated the band gap values, the optical absorptions and the vibrational response of the materials. The results showed that the α‐NPD thin films show four characteristic absorptions and the optical response of the material is independent of the films thickness. Finally, in case of Alq3, the material shows a band gap at 2.7 eV and three characteristic absorptions.
Influence of stabilizers in ZnO nano‐dispersions on the performance of solution‐processed FETs
Authors: Mechau Norman , Bubel Simon , Nikolova Donna , Hahn Horst 
Published: May 2010

AbstractSolution‐processed field‐effect transistors (FETs) based on inorganic nano‐materials are attractive system for applications in the field of printable electronics. Stabilized suspensions made of zinc oxide nano‐particles were used to fabricate FETs by spin coating. The performance of such devices is strongly affected by the nature and concentration of the compounds added to stabilize the nano‐dispersions. In this work we compare the field‐effect mobility of zinc oxide transistors when the nano‐particle dispersion is prepared using two different types of commercially available stabilizers. For the stabilizer TEGO Dispers 752 W we observed an increase in the field‐effect mobility by more than one order of magnitude. In contrast, for TEGO Dispers 750 W where a decrease in the field‐effect mobility of more than two orders of magnitude was observed. This stark difference is attributed to be due to the electrical conductivity of the stabilizers, the morphology and interface roughness and the stabilizer particle interaction.
Study on the durability against heat in ITO/Ag‐alloy/ITO transparent conductive multilayer system
Authors: Roh Hee‐Sook , Cho Sun‐Hee , Lee Won‐Jong 
Published: May 2010

AbstractWe studied the effects of added metallic elements in Ag‐alloy layers of indium‐tin‐oxide (ITO)/Ag‐alloy/ITO transparent conductive multilayer system on the durability against heat. When Ag film was heat treated, agglomeration occurred due to the surface diffusion of the Ag atoms. This caused an increase in the sheet resistance and a decrease in the transmittance. Added metallic elements such as Au, Pd, and Cu in Ag‐alloy layers increased the onset temperature and activation energy for agglomeration. These added metallic elements also decreased the surface energy of the Ag film. The durability against heat was improved by adding metallic elements to the Ag film of the ITO/Ag/ITO multilayer system. Cu atoms, especially, diffused out to the surface of the Ag film hindered the surface diffusion of the Ag atoms, resulting the improvement of thermal stability of the Ag film. The figure of merit (FOM, T10/R□) of ITO/Ag/ITO multilayer decreased to 1/15 of its initial value after heat treatment at 450 °C for 6 h, whereas it decreased to 1/3 of its initial value when Pd and Cu were added to Ag film.
Subgap states, doping and defect formation energies in amorphous oxide semiconductor a‐InGaZnO4 studied by density functional theory
Authors: Kamiya Toshio , Nomura Kenji , Hosono Hideo 
Published: May 2010

AbstractAmorphous In‐Ga‐Zn‐O (a‐IGZO) is expected for channel layers in thin‐film transistors (TFTs). It is known that a‐IGZO is sensitive to an O/H‐containing atmosphere; therefore, it is important to clarify the roles of oxygen and hydrogen in a‐IGZO. This paper provides atomic and electronic structures, formation energies of defects and bond energies in a‐IGZO calculated by first‐principles density functional theory (DFT). It was confirmed that oxygen deficiencies having small formation energies (2–3.6 eV) form either deep fully‐occupied localized states near the valence band maximum or donor states, which depend on their local structures. All the hydrogen doping form OH bond and work as a donor. The stable OH bonds have small formation energy of ∼0.45 eV and consist of three metal cations coordinated to the O ion. The bond energy of GaO is calculated to be ∼2.0 eV, which is the largest among the chemical bonds in a‐IGZO (1.7 eV for InO and 1.5 eV for ZnO). This result supports the idea that the incorporation of Ga stabilizes a‐IGZO TFTs.
Epitaxial growth of ZnO thin films on AlN substrates deposited at low temperature by magnetron sputtering
Authors: Rahmane S. , Abdallah B. , Soussou A. , Gautron E. , Jouan P.‐Y. , Le Brizoual L. , Barreau N. , Soltani A. , Djouadi M. A. 
Published: May 2010

AbstractHexagonal aluminium nitride (AlN) and zinc oxide (ZnO) thin films have been deposited by DC and RF reactive magnetron sputtering at room temperature. For a first set of samples, sputtered AlN films were deposited on silicon ZnO substrate. For a second set, ZnO films were deposited on AlN substrate. X‐ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis of the synthesized AlN film on ZnO buffer layer have shown some amorphous zones close to the interface followed by a nanocrystalline layer exhibiting (10−10) and (0002) orientations of the hexagonal AlN crystalline phase. At the top of the film, a relatively well‐crystallized layer with a single (0002) orientation has been observed. We have related the relatively bad interface to the presence of oxygen coming from ZnO substrate. This behaviour was different for the growth of ZnO film when AlN was used as substrate. In fact, we have observed thanks to HRTEM images and selected area electron diffraction patterns, that the ZnO film deposited on AlN substrate exhibits an epitaxial growth which is strongly dependent on the crystalline quality of AlN film.
Mg‐related acceptors in GaN
Authors: Monemar B. , Paskov P. P. , Pozina G. , Hemmingsson C. , Bergman J. P. , Amano H. , Akasaki I. , Figge S. , Hommel D. , Paskova T. , Usui A. 
Published: May 2010

AbstractPhotoluminescence spectra of c ‐plane Mg doped GaN samples grown by MOVPE on bulk GaN templates reveal previously unknown properties, like the presence of several Mg‐related acceptors. The use of unstrained samples allows a study of both bound exciton (BE) and donor‐acceptor pair (DAP) spectra. Two main acceptors A1 and A2 are observed strongly in BE spectra as well as in DAP spectra, they have similar binding energies, i.e. about 220 meV. The common assignment of the deeper blue PL emission at 2.8–3.0 eV to a deep donor‐shallow acceptor transition is questioned, and discussed in connection with the compensation problem in p‐GaN. It seems like the Fermi level in p‐GaN is controlled by a set of Mg‐related acceptors at energies 0.2–0.6 eV from the valence band top. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence of GaN/AlN quantum dots at high excitation powers
Authors: Aleksandrov Ivan , Zhuravlev Konstantin 
Published: May 2010

AbstractExcitation power and temperature dependencies of the photoluminescence (PL) of wurtzite GaN/AlN quantum dots (QDs) grown by molecular beam epitaxy have been investigated. The PL band of the QDs exhibited a shift to lower energy with increasing excitation power. This red shift was attributed to the band‐gap renormalization. The non‐stationary PL decay law is non‐exponential and varies over the spectrum. The PL band of the GaN/AlN QDs shifts to lower energy with delay time after a pulsed excitation as a result of the increase of the carrier lifetime with increase in the QD size. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐temperature operation of GaN‐based OPAMP on silicon substrate
Authors: Nomoto Kazuki , Hasegawa Kazuya , Nakamura Tohru 
Published: May 2010

AbstractWe demonstrated electrical characteristics of operational amplifier (OPAMP) circuits fabricated by GaN/AlGaN/GaN HEMTs operating over 200 °C. GaN/AlGaN/GaN HEMTs, with the extremely low source resistance were fabricated by multiple ion implantation, precisely controlled ion‐implanted (I/I) resistors and Schottky barrier diodes were integrated on the silicon substrate. The GaN cap layer on the AlGaN was grown to decrease the gate leakage current and current collapse for AlGaN/GaN HEMTs. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study on the effect of the relative position of the phosphor layer in the LED package on the high power LED lifetime
Authors: Hwang Jung‐Ha , Kim Yu‐Dong , Kim Jae‐Wook , Jung Su‐Jung , Kwon Ho‐Ki , Oh Tchang‐Hun 
Published: May 2010

AbstractFor the case of the white LED (phosphor converted), the temperature affects phosphor in addition to chip and package. The heat can cause the decrease of the phosphor performance as well as the irreversible damage to the phosphor. In this study, the effect of phosphor thermal configuration on the degradation rate has been investigated experimentally and verified by the theoretical simulations. Two different configurations have been tested. One is die‐contact phosphor layer and the other is remote case. The experimental result shows that the LEDs of the die‐contact phosphor layers exhibit lower degradation rate than those of the remote phosphor layers. The thermal simulation considering the heat generation from the phosphor (energy converting loss) shows similar results. The temperature of remote phosphor layer is higher than the die‐contact case. High temperature causes rapid degradation of phosphor. As the power consumption of LEDs increases, the heat generation from the phosphor becomes no more negligible. For the higher performance and longer lifetime, we have to consider phosphor layer as the heat generator and design the layer with sufficient thermal paths. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Piezoelectric actuated epitaxially grown AlGaN/GaN‐resonators
Authors: Niebelschuetz F. , Brueckner K. , Tonisch K. , Stephan R. , Cimalla V. , Ambacher O. , Hein M. A. 
Published: May 2010

AbstractIn this work we present a novel concept of piezoelectrically actuated MEMS resonators based on AlGaN/GaN‐heterostructures. The 2DEG, which is confined at the AlGaN/GaN interface, serves as back electrode for piezoelectric actuation and read‐out. Using the inverse piezoelectric effect longitudinal in‐plane mechanical oscillations could be exited by applying a RF signal to the drive contacts. Through the charges, which were generated by the direct piezoelectric effect a sensor signal could be detected at the sense contacts of the integrated resonator structure. This enables the measurement of longitudinal resonant frequencies up to the 4th mode with values from 3 to 63 MHz. The investigations were carried out in various ambient pressure conditions, which exemplarily demonstrate the sensitivity of the quality factor to environmental parameters. Thereby the AlGaN/GaN‐resonators showed the highest sensitivity in the region of viscous damping, which leads to the possibility of sensor applications concerning the property determination of gaseous or even liquid surrounding conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dissolution Study of Salt of Long Chain Fatty Acids (Soap Scum) in Surfactant Solutions. Part II: Kinetics of Dissolution
Authors: Soontravanich Sukhwan , Landrum J. Grant , Shobe Sarah A. , Waite Chase M. , Scamehorn John F. , Sabatini David A. , Scheuing David R. 
Published: May 2010

AbstractA study of the dissolution kinetics of soap scum, calcium octadecanoate (Ca(C18)2), by aqueous solutions was carried out by measuring the rate of dissolution of Ca(C18)2 using a flow cell apparatus. These solutions contained three different types of surfactants: dimethyldodecylamine oxide (DDAO), sodium dodecyl sulfate (SDS), or octyl polyglycoside (C8APG), in the presence of a chelating agent, disodium ethylenediaminetetraacetate (Na2EDTA). The resulting rate of dissolution corresponds well with the equilibrium solubility obtained in the part I of this series even though the dissolution is rate limited (far from equilibrium). High rates of Ca(C18)2 dissolution are achieved in solutions of zwitterionic DDAO or nonionic C8APG with Na2EDTA at high pH. From rate analysis, the Ca(C18)2 dissolution was found to be surface‐reaction limited rather than limited by solution processes or wettability.
The Planetary Nebula Luminosity Function: Pieces of the Puzzle
Authors: Ciardullo R. 
Published: May 2010

AbstractExtragalactic surveys in the emission line of [O iii] λ5007 have provided us with the absolute line strengths of large, homogeneous sets of planetary nebulae. These data have been used to address a host of problems, from the measurement of the extragalactic distance scale, to the study of stellar populations. I review our current understanding of the [O iii] planetary nebula luminosity function (PNLF), and discuss some of the physical processes that effect its structure. I also describe the features of the Hα PNLF, a function that, upon first glance, looks similar to the [O iii] PNLF, but which includes a very different set of objects. Finally, I discuss recent measurements of α, the number of PNe found in a stellar population, normalized to that population's bolometric luminosity. I show that, contrary to expectations, the values of α found in actively star-forming spirals are essentially the same as those measured in late-type elliptical and lenticular systems. I discuss how this result sheds light on the physics of the planetary nebula phenomenon.
A FUSE View of Winds from the Central Stars of Planetary Nebulae
Authors: Guerrero Martín A. , Ramos-Larios Gerardo , Massa Derck 
Published: May 2010

AbstractSince the IUE satellite produced a vast collection of high-resolution UV spectra of the central stars of planetary nebulae (CSPNe), there has not been any further systematic study of the stellar winds of these stars. The high spectral resolution, sensitivity and large number of archival observations in the FUSE archive allow the study of the stellar winds of CSPNe in the far-UV domain where lines of species spanning a wide excitation range can be observed. We present here a preliminary analysis of the P Cygni profiles of a sample of ∼60 CSPNe observed by FUSE. P Cygni profiles providing evidence for fast stellar winds with velocities between 200 and 4300 km s−1 have been found in 40 CSPNe. In many cases, this is the first time that fast stellar winds have been reported for these planetary nebulae (PNe). A detailed study of these far-UV spectra is on-going.