bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Classic Molecular Semiconductor Revisited: New Aspects of Growth Mode and Conduction Characteristics in Thin Films of Phthalocyaninatozinc (PcZn)
Authors: Brinkmann Harry , Schlettwein Derck 
Published: April 2011

ABSTRACTPcZn as a well known organic semiconductor received new examination of its growth mode in thin films and reactions to oxygen exposure. PcZn thin films were grown on glass and polyimide substrates by physical vapor deposition. Ag electrodes had been deposited by a sputter process to allow electrical contact to the films. Conductivity measurements were performed in-situ during the growth of films under high vacuum conditions. Characteristic current peaks were observed and explained by a Stranski-Krastanov growth mode. Current voltage characteristics revealing space charge limitation could be obtained beginning in the monolayer range. For pristine films n-type conduction was observed. Following deposition an increase of the conductivity was measured, caused by changes of the film structure. Ripening under high vacuum conditions could be separately discussed from doping effects caused by oxygen exposure which led to the well- known p-type characteristics of PcZn.
Water-Soluble Conjugated Polyelectrolytes with Molecular Bumper for Efficient FRET Biosensor
Authors: Woo Han Young , Vak Doojin , Bazan Guillermo C 
Published: April 2011

ABSTRACTWe report the design, synthesis and photophysical properties of two new water-soluble conjugated polyelectrolytes, poly(9,9'-bis(6-N,N,N-trimethylammoniumhexyl)fluorene-alt-1,4-(2,5-bis(6-N,N,N-trimethylammoniumhexyloxy))phenylene) tetrabromide (P1i) and poly((10,10'-bis(6-N,N,N-trimethylammoniumhexyl)-10H-spiro(anthracene-9,9'-fluorene))-alt-1,4-(2,5-bis(6-N,N,N-trimethylammoniumhexyloxy))phenylene) tetrabromide (P2i). They have same electronic conjugation but the main structural difference is the presence of the anthracenyl substituent orthogonal to the polymer main backbone in P2i. Fluorescence resonance energy transfer (FRET) from the two polymers as FRET donors to fluorescein-labeled single stranded DNA (ssDNA-Fl) was studied. It is observed the emission from ssDNA-Fl via FRET by excitation of P2i with a FRET efficiency of ∼60%. Fluorescein is not emissive within the ssDNA-Fl/P1i complex. We also observed clear PL quenching (Φ = 0.8 → Φ = 0.27) of fluorescein for P2i after electrostatic complexation with ssDNA-Fl. It suggests a quenching pathway of Fl emission through photo-induced charge transfer (PCT) in the electrostatic complex. Both P1i and P2i have same HOMO-LUMO electronic structures and a similar thermodynamic driving force for either FRET or PCT. It appears that PCT operates to a larger extent with P1i, proposing that the presence of the “molecular bumper” in P2i increases Fl emission by increasing the donor-acceptor distance, which decreases more acutely PCT quenching, relative to FRET.
Ultrahigh Vacuum Seebeck Effect and Conductivity Measurements on N-Doping of C60 Films
Authors: Hayashi Naoki , Kanai Kaname , Ouchi Yukio , Seki Kazuhiko 
Published: April 2011

ABSTRACTWe constructed an ultrahigh vacuum (UHV) system with which in-situ conductivity and Seebeck coefficient measurements can be performed, including the detailed examination of the oxygen effect. It can also carry out the deposition of metal electrodes and organic films under UHV condition through measurements. The conductive characteristics of fullerene (C60) films were examined by the measurement at conductivity and Seebeck coefficient under UHV. We observed that the conductivity at room temperature was higher than 1×10−3 S cm−1. This value is two orders of magnitude in conductivity higher than the Hamed report. [A. Hamed et al., Phys. Rev. B 47, 10873 (1993).] Seebeck coefficient S was also measured. Its sign was negative, indicating electron conduction for C60 film. After the measurements under UHV, oxygen was introduced into the chamber by a variable leak valve. The conductivity decreased drastically by increasing the pressure of oxygen. It decreased more than five orders from under UHV to 1 atom oxygen. The temperature dependence of the conductivity was also examined. The conductivity was thermally activated. Activation energies of the conductivity increase by increase oxygen pressure. This means that the oxygen act as carrier traps. As an n-type dopant, acridine orange base (AOB) was co-deposited into C60 films. The magnitude in the conductivity increased but not drastic. The conductivity of doped film also decreased by increasing the pressure of oxygen. The conductivity even under 6.6×10−2 Pa, however, was high enough. Though AOB was not effective dopant against C60 film in UHV condition, AOB doped C60 film became resistant to oxygen.
Epitaxial Growth of C60 Thin Films using Continuous-wave Laser Molecular Beam Epitaxy
Authors: Yaginuma Seiichiro , Itaka Kenji , Haemori Masamitsu , Katayama Masao , Matsumoto Yuji , Koinuma Hideomi 
Published: April 2011

ABSTRACTWe have fabricated C60 thin films on various substrates (mica, MoS2, HOPG, LiF, NaCl, KBr, KCl and CaF2) by using continuous-wave laser molecular beam epitaxy (CWL-MBE), which is very suitable technique to grow epitaxial organic thin films because of good controllability of evaporation as compared with Knudsen-cell method. The films were evaluated by reflection high-energy electron diffraction with micro channel imaging plate (MCP-RHEED) and atomic force microscopy (AFM). AFM images of the C60 films on mica, MoS2 and HOPG substrates show flat and homogeneous, morphology, and epitaxial growth of the films on mica and MoS2 substrates were observed by RHEED. This result shows mica, MoS2, HOPG substrates are good candidates for epitaxial growth of C60 thin films.
Assembly of Tailored Thiophene Oligomers on Gold Electrodes - Film Formation and Properties
Authors: Collier Peter Anthony , Deivaraj Theivanayagam Chairman , Kerk Wai Tat , Chin Wee Shong , Loh Kian Ping , Bai Ping , Li Er Ping 
Published: April 2011

ABSTRACTTo examine the potential to apply chemically modified surfaces in organic thin film transistors (TFT), we report the synthesis and characterization of two tailored series of oligothiophene compounds. The oligomers have thiol end groups for coupling to gold electrodes and have regio-regular alkyl substitutions corresponding to Head-Head (HH-) and Head-Tail (HT-) molecular conformations. Variations in chain length, structures and end groups have enabled a detailed study of the deposition of films from solution and the films' properties.
Penetration of Tagged Organics into Caulked and Un-caulked Porous Dielectrics Measured by Rutherford Backscattering
Authors: Geil Robert D. , Senkevich Jay J. , Rogers Bridget R. 
Published: April 2011

ABSTRACTA novel method for studying the penetration of wet chemicals into caulked and uncaulked porous dielectrics was developed, and the barrier properties of parylene X were evaluated. Rutherford backscattering spectrometry (RBS) was used to study the penetration of chlorine-tagged organics, 3-chloro-1-propanol and a %5 HCl solution. After one minute of exposure time, eight times more 3-chloro-1-propanol diffused through uncaulked porous dielectric compared to caulked porous dielectric. Penetration from the side of the samples was found to be insignificant.
Influence of Interfacial Delamination on Channel Cracking of Brittle Thin Films
Authors: Pang Yaoyu , Huang Rui 
Published: April 2011

ABSTRACTChanneling cracks in low-k dielectrics have been observed to be a key reliability issue for advanced interconnects. The constraint effect of surrounding materials including stacked buffer layers has been studied. This paper analyzes the effect of interfacial delamination on the fracture condition of brittle thin films on elastic substrates. It is found that stable delamination along with the growth of a channel crack is possible only for a specific range of elastic mismatch and interface toughness. An effective energy release rate is defined to account for the influence of interfacial delamination on both the driving force and the fracture resistance, which can be significantly higher than the case assuming no delamination.
Wafer Level Chip Size Packaging Technology for Bulk Acoustic Wave Filters
Authors: Yamada Hajime , Aizawa Naoko , Fujino Hiroyuki , Koshido Yoshihiro , Yoshino Yukio 
Published: April 2011

ABSTRACTWafer level chip size packages (WL-CSP) have been successfully fabricated for bulk acoustic wave (BAW) filters. WL-CSP has been completed at the wafer level prior to dicing. Two silicon wafers are used as a die and a lid for chip size packaging. Both device and lid wafers have the same expansion coefficient and the package is strong enough to withstand the thermal stress. The package has a hermetic seal with copper-tin intermetallic bonding. The bonded wafers are then thinned by grinding. Via holes are formed by reactive ion etching (RIE) and filled by copper electroplating. The package has solder bumps on each terminal, ready for flip-chip assembly. We have succeeded to produce CSP-BAW filters with a hermetically sealed cavity, which is 840 micrometers squared and 280 micrometers in height including solder bumps.
Texture Evolution and Stress in Silver Thin Films on Different Substrates Using X-ray Diffraction
Authors: Zoo Yeongseok , Alford Terry L. 
Published: April 2011

ABSTRACTSubstrate surface roughness effects on Ag film texture were investigated using pole figure analysis. X-ray diffraction results confirmed that Ag thin films on smooth SiO2 substrates had strong {111} texture when compared with Ag films on PEN. It was noted that the difference of strain energy density (δEε) in Ag film on PEN (0.039 MPa) was almost 5 times greater than that on SiO2 (0.0084 MPa). The comparison between surface and strain energies revealed that the {111} texture of Ag thin film on SiO2 was explained by minimization of the surface energy and the weaker {111} texture of Ag on PEN was a result of reduced diffusion length of Ag adatoms on the rough PEN surface.
The Effects of the LDD process on Short-channel effects in Nanoscale Charge Trapping Devices
Authors: Kim Moon Kyung , Chae SooDoo , Kim Chung Woo , Kim Joo Yeon , Lee Jo-won , Tiwari Sandip 
Published: April 2011

AbstractIn the use of single/few electrons in distributed storage for non-volatile, low power, and fast memories, providing statistical reproducibility at the nanoscale is a key challenge since relative variance has dependence and the devices operate with limited number of storage sites. We have used defects at interfaces of dielectrics to evaluate this reproducibility and the performance of memories. These experiments show that nearly 100 electrons can be stored at 30 nm dimensions, sufficient for reproducibility, and that a minimum of tunneling oxide thickness is required to assure reliable retention characteristics. Different tunneling oxide thicknesses and the effect of LDD process are investigated to draw these conclusions.
Investigation of Resistive Switching at SrRuO3/Cr-doped SrZrO3/Metal Junctions
Authors: Lee Hwan-Soo 
Published: April 2011

AbstractWe have investigated charge transport properties with current perpendicular to the plane across the interface between a Cr-doped SrZrO3 perovskite oxide film and different top electrode metals. The measured resistance showed a wide variation depending on the top electrode metal, and suggested the interfacial properties with respect to contacting electrode metal kinds are responsible for the change in I-V characteristics (IVCs). The observed I-V curves were modeled with the equation I(V) = aV+bV2, where the variation of a was related to the work function of the metal whereas the variation of b was related to the oxygen affinity of the metal, consistent with space charge limited conduction through a defected interface. Additionally, the resistive switching was attributed to a change in both the a and the b coefficients. We speculate that voltage (or current) induced vacancy motion can account for a change in trap density in the oxide near the metallic electrical contact, and thus trapping or detrapping of charge carriers, showing the conductivity modulation across the junction.
Electrical Study of Ferromagnet Metal Gate MOS Diode: Towards a Magnetic Memory Cell Integrated on Silicon
Authors: Kanoun Mehdi , Benabderrahmane Rabia , Duluard Christophe , Baraduc Claire , Bruyant Nicolas , Achard Hérvé , Bsiesy Ahmad 
Published: April 2011

AbstractThis work focuses on electrical characterisation of NiFe/SiO2/Si diodes that can be used as spin injection into silicon for future spintronic devices. Capacitance-voltage characteristics show a large increase of the Si/SiO2 interfacial state density compared to Al/SiO2/Si diodes. This result suggests that nickel and/or iron may have diffused across the SiO2 layer. Consistently the current-voltage experimental characteristics can be accounted for by using trap assisted electron transport mechanism. These traps may be attributed to ferromagnet atoms in the oxide bulk.
Characterization of Sn, Zn, In, and Sb-Containing GeSe Alloys for Phase-Change Electronic Memory Applications
Authors: Campbell Kris , Davis Morgan G. , Peloquin Jeffrey M. 
Published: April 2011

AbstractTwo-terminal electronic devices consisting of stacks of chalcogenide layers containing GeTe, Ge40Se60, SnTe, or SnSe have shown promise for application as electronic phase-change memories (Campbell, K.A. and Anderson, C.M., Microelectronics Journal 38, 52–59 (2007)). Here, we report the synthesis of (Ge40Se60)100−zMz alloys where M = Sn, In, Sb, and Zn, and the corresponding bulk material Raman spectra and differential scanning calorimetry data in order to explore material compositions that might be useful for producing a multi-state phase-change memory device.
First-principles Calculations on the Zn1-xMgxO Window Layer Material for CIS Thin Film Solar Cells
Authors: Maeda Tsuyoshi , Shigemi Akio , Wada Takahiro 
Published: April 2011

AbstractWe have theoretically evaluated the phase stability and electronic structure of a Zn1-xMgxO solid solution. The enthalpies of formation for both the wurtzite and rocksalt phases of Zn1-xMgxO were calculated using a plane-wave pseudopotential method within the density functional formalism. For 0 < x < 0.5, the calculated enthalpies of formation (&[Delta]H) for the wurtzite phases were lower than those for the rocksalt phases. On the other hand, for x > 0.75, the &[Delta]H values for the wurtzite phase were larger than those for the rocksalt phases. This indicates that the wurtzite phase is more stable for a Zn1-xMgxO solid solution with 0 < x < 0.5, while the rocksalt phase is more stable for a solid solution with x > 0.75. The band gaps of a wurtzite Zn1-xMgxO solid solution increase with increasing Mg content. MgO substitution on Zn1-xMgxO largely affects the conduction band leaving the valence band nearly unchanged. The conduction band minimum (CBM) shifted to higher energy with increasing Mg content. These theoretical results qualitatively agree with the experimental results for Zn1-xMgxO thin films fabricated by RF magnetron co-sputtering.
Validation of the p-type Behavior of an Ag-doped ZnSe Film Grown Heteroepitaxially on GaAs(100) Substrate
Authors: Narushima Takashi , Yanagita Hiroaki , Orita Masahiro 
Published: April 2011

AbstractTo validate p-type semiconducting behavior in Ag-doped ZnSe, single-crystal films were grown on GaAs(100) substrates using an evaporation method with ZnSe and Ag2Se powder sources. The heteroepitaxial relationship between ZnSe(100) and GaAs(100) was observed using X-ray diffraction and transmission electron microscopy; secondary phases containing silver or silver selenide were not detected. A film doped with Ag at 1 1020 atm·cm-3 had a conductivity of 1.5 x 10-5 S·cm-1. The hot-probe test indicated p-type polarity, with a clear and reproducible rectifying characteristic demonstrated by forming a ZnSe:Ag/p-GaAs:Zn junction. The work function of a ZnSe:Ag film measured by ultraviolet photoelectron spectroscopy was 6.3 eV. The ZnSe:Ag film is suitable as an injection layer in widegap semiconductor devices and organic light-emitting diodes.
On the Origins of Impurities in CdTe-Based Thin Film Solar Cells
Authors: Emziane Mahieddine , Halliday Douglas P. , Durose Ken , Romeo Nicola , Bosio Alessio 
Published: April 2011

AbstractWe present a multi-element study of impurities in CdTe/CdS photovoltaic cells, aimed at understanding their origins and impact on devices. Our investigation was based on calibrated secondary ion mass spectrometry (SIMS) depth profiling, with Na, Zn, Sn, O, Sb, Si, Cl, In, Cu and Pb being studied. The solar cell structures were grown by sputtering and close-space sublimation, and some of them were further processed (CdCl2 and Br2-methanol) for the purpose of comparison. Using source materials of different purity allowed us to establish the origins of impurities. We found that some elements increased in concentration upon processing, namely Cl (x100), Na (x10), and In (x1.5). The concentrations of Si, Cu, Zn, Sn and Sb found in a processed device were largely unchanged - and are similar to those found in a high purity single crystal CdTe reference sample.
Optical Absorption at Digitally and Continuously Graded Indium Gallium Nitride Schottky Barriers
Authors: Praharaj Choudhury Jayant 
Published: April 2011

AbstractWe present numerical calculations of the optical absorption characteristics of graded Indium Gallium Nitride Schottky Barriers, and study their implications for photovoltaic and photodetector applications. We consider the two cases of digital and continuous grading because of their different effects on the collection of photo-generated carriers due to band discontinuities. Composition grading can achieve desired spectral response between the ranges of 0.7 eV and 3.43 eV afforded by the Indium Gallium Nitride alloy system. The presence of spontaneous and piezoelectric polarizations in this material system adds bulk and/or interface bound charges in graded layers. This has a non-trivial effect on the band profile seen by the photo-generated carriers. The layer thicknesses needed for optimal absorption characteristics are well above the theoretical critical thickness limits reported in the literature for abrupt heterojunctions. However, experimental data about critical thicknesses is scarce, especially for graded compositions. Therefore, we calculate the characteristics of the Schottky barrier for the case of spontaneous polarization only and also for the case of both spontaneous and piezoelectric polarization assuming no relaxation. The low or even negative Schottky barrier heights at low Gallium composition necessitates the use of high Gallium composition layers next to the metal, in order to suppress the excessive dark currents
Quantitative Measurement of Dopant Concentration Profiling by Scanning Nonlinear Dielectric Microscopy
Authors: Ishikawa Kenya , Honda Koichiro , Cho Yasuo 
Published: April 2011

AbstractUsing a scanning nonlinear dielectric microscopy (SNDM), we observed two standard Si samples with epitaxial staircase structures, which have known dopant density values calibrated by using secondary ion mass spectroscopy (SIMS). As the result, good quantitative correlation between dopant density values and SNDM signals was obtained without the phenomenon of contrast reversal effect, which is associated with conventional scanning capacitance microscopy (SCM) measurements. Thus, it is expected that SNDM will be an effective method for observing the quantitative measurement of two-dimensional dopant profiling on semiconductor devices.
SPM-based Electrical Characterization of Aged Waspaloy Microstructures
Authors: Kelekanjeri G. Siva Kumar V. , Gerhardt Rosario A 
Published: April 2011

AbstractThe results of SPM-based localized electrical examination of precipitation hardened Waspaloy microstructures using Electrostatic Force Microscopy (EFM) and Current-Atomic Force Microscopy (I-AFM) are reported herein. The measurements were conducted on two differently etched specimens with the same initial microstructure. Selective etching by preferentially removing the γ′ or the γ phase resulted in a non-uniform surface topography leaving the less reactive phase standing in relief relative to the depressed phase. The presence of a non-uniform surface topography affected the measured EFM response by causing an inhomogeneous surface voltage distribution. A non-linear tip-surface interaction could have further complicated the measured EFM response by making it non-localized. The EFM phase obeyed a supplementary behavior upon reversing the polarity of the DC bias. Using I-AFM, the tip current was found to be the highest at γ-γ′ interphase boundaries, which was attributed to the relaxation of the lattice atoms in the relief zone formed upon etching.
Green Light Emitting Diodes under Photon Modulation
Authors: Li Yufeng , Senawiratne Jayantha , Xia Yong , Zhu Mingwei , Zhao Wei , Detchprohm Theeradetch , Wetzel Christian M 
Published: April 2011

AbstractWith an external laser excitation, the electroluminescence (EL) of GaInN/GaN green light emitting diodes (LEDs) grown on sapphire by metal organic vapor phase epitaxy has been investigated. The EL was found significantly enhanced under this bias and the difference can not merely be attributed to additional photoluminescence (PL). Under 325 nm photon bias, the EL enhancement starts at its highest value and decreases along with an increase of the LED current. Under 408 nm and 488 nm bias, it increases first to a value smaller than that of the 325 nm bias and then decreases with a much lower rate along the current increase. The EL enhancement is attributed to the more efficient carrier injection into quantum wells (QWs) resulting from the screening of the QW polarization by photon bias. Therefore, an enhanced balance of majority and minority carriers was obtained resulting in a better radiative recombination rate. Meanwhile, the current-voltage characteristics show a negative current first and then a voltage reduction as forward voltage increases. The reverse photocurrent indicates carrier loss due to the solar cell effect in our LED device while at high current region the carrier loss is attributed to another effect controlled by the external electrical field. At the balance point of those two effects, the EL enhancement is the highest. These findings clarify the transition from highly efficient radiative recombination at low current density to the region of efficiency droop at high current densities.
Electron Band Structure of MnGaN
Authors: Alexandrov Dimiter , Dietz Nikolaus , Ferguson Ian , Yu Hang 
Published: April 2011

AbstractInvestigation of the properties of MnxGa1-xN semiconductor alloy is performed on the basis of LCAO electron band structure of this semiconductor. The authors model this alloy on the basis of Mn substitutions on Ga sites and it is identified that the ternary semiconductor MnxGa1-xN has two tetrahedral binary constituents – GaN and MnN. It is found that the sp3 hybrid orbital of the N atom attracts an electron from the 3d orbital of the Mn atom and thus the Mn-N bonding becomes of sp3 type. In this way the total electron spin of the 3d orbital of the Mn atom becomes 3/2, which determines that the energy levels 4F, 4D, 4P and 4G belonging to this orbital to be occupied. LCAO electron band structure of wurtzite MnxGa1-xN for points Γυc1 and Γυv15 (υ = 1, 2, 3, 4, 5) is calculated by previously developed method and the positions of the levels 4F, 4D, 4P and 4G in this structure are determined. It is found dependence of the total electron spin of the Mn atom on the position of the Fermi level in the electron band diagram of MnxGa1-xN. Also it is found that the total spin depends on electron inter-band transitions as well. The optical properties of the wurtzite MnxGa1-xN are determined as well.