bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dry Etch and Wet Clean Process Characterization of Ultra Low-k (ULK) Material Nanoglass®E
Authors: Murthy B. Ramana , Chang C.K. , Ahilakrishnamoorthy  , Chen Y.W. , Naman Ananth 
Published: April 2011

AbstractNANOGLASS®E (NGE) ultra low-k (ULK) dielectric material, with a k-value of ∼2.2, was integrated for 130 nm Cu/ULK interconnect process technology. This work deals with the characterization of reactive ion etching (RIE) and wet chemical processing of this film. Blanket films were characterized for etch rate, surface roughness, k-value change and chemical compatibility. Trench etching and post etch wet clean processes were developed and optimized enabling process integration for single damascene structures. Trench etch processes were evaluated for two etch schemes viz., etching under - photo resist and etching under hardmask. The details of each scheme will be described and advantages observed will be discussed. To evaluate effect of wet clean processes three different formulations were used. After formation of single damascene wafers, metal comb and serpentine structures were measured for metal continuity and bridging. Electrical continuity was achieved for long serpentine structures with 0.18μm/0.18μm line width/spacing. Based on voltage ramp test results the film was found to be sensitive to certain plasma etch conditions.
The Influence of Temperature and Concentration on Copper Deposition Kinetics in Supercritical Carbon Dioxide
Authors: Zong Yinfeng , Watkins James J. 
Published: April 2011

AbstractThe kinetics of copper deposition by the hydrogen-assisted reduction of bis(2,2,7- trimethyloctane-3,5-dionato)copper in supercritical carbon dioxide was studied as a function of temperature and precursor concentration. The growth rate was found to be as high as 31.5 nm/min. Experiments between 220 °C and 270 °C indicated an apparent activation energy of 51.9 kJ/mol. The deposition kinetics were zero order with respect to precursor at 250 °C and 134 bar and precursor concentrations between 0.016 and 0.38 wt.% in CO2. Zero order kinetics over this large concentration interval likely contributes to the exceptional step coverage obtained from Cu depositions from supercritical fluids.
Charge trapping and scattering by extrinsic gas dopants in tris(8-hydroxyquinoline) aluminum (Alq3)
Authors: Fong H.H. , So S.K. 
Published: April 2011

AbstractThe effects of various ambient gases (N2, O2, H2O) to the electron mobility of tris(8-hydroxyquinoline) aluminum, Alq3, were examined. For a clean Alq3, the electron transport is non-dispersive and essentially trap-free as revealed by optical time-of-flight measurements. At 295K, the electron mobility (μe) spans the range 0.2-1×10−6cm2V−1s−1 when the field varies from 0.4-0.9 MV cm−1. Exposing the sample to oxygen dosages in the range 1-100 Torr.s does not cause any noticeable changes in μe. The effect of oxygen on μe can be observed only at much higher oxygen dosages (>105 Torr.s). In contrast, exposing pristine Alq3 to moisture of same dosages causes a gradual reduction in μe by a factor of 4. It is proposed that oxygen diffuses into Alq3 during exposure and subsequently acts as charge scattering centers for externally injected free electrons. On the other hand, water induces charge traps at high dosages. Moisture control appears to be the most critical factor for the long-term operation of Alq3-based organic light-emitting diodes.
a-Si TFT OLED Fabricated on Low-Temperature Flexible Plastic Substrate
Authors: Sarma Kalluri R. 
Published: April 2011

AbstractActive matrix organic light emitting diode (AM OLED) display fabricated on a flexible plastic substrates has a potential for being lower cost, lighter weight, lower power and highly rugged with superior image quality, compared to the current glass substrate based AM LCDs. Amorphous silicon (a-Si) technology offers the potential for fabricating the required active matrix backplanes on low temperature (< 150°C) plastic substrates for producing flexible AM OLED displays. We have developed low-temperature a-Si TFT processes, and backplane electronics designs to fabricate and successfully demonstrate AM OLEDs using 4”-size flexible plastic substrates. Flexible AM OLED test displays with sizes up to 2×2-inch and resolutions up to 80 cgpi equivalent have been designed and fabricated. The required enabling technologies and fabrication and evaluation of these displays are discussed.
A Simple Explanation on the Crystallization Kinetics of a Cw Laser Crystallization of Amorphous Silicon
Authors: Park Seong Jin , Kang Sang Hoon , Ku Yu Mi , Jang Jin 
Published: April 2011

AbstractWe have studied a CW laser crystallization (CLC) of various-shaped a-Si patterns on glass with changing scanning speed and laser power. The crystallized region inside the patterns showed 3 distinct regions, which is distinguished by their grain size; fine grains of several tens of nanometers near the edge of the pattern, very large grains over a few micrometers at the center of the pattern, so called Sequential Lateral Crystallization region and large grains about a micrometer or less between SLC and fine grain regions. This phenomenon is due to the formation of 2-D temperature gradient inside the pattern. One is the temperature gradient between the edge and center; the temperature of outer region is lower than that of inner region during or right after a CW laser scanning. The other is the temperature gradient along the scan direction; the temperature of starting region of a CW laser scanned area is lower than that of ending region. The former contributes mainly to make molten silicon area inside a pattern, and the latter induces lateral growth along the scan direction to make long grains in SLC region.
Flexible Substrate Based Gas Sensors for Air Pollution Monitoring
Authors: Dmitriev S. , Duca Gh. , Dementiev I. , Craciun A. 
Published: April 2011

AbstractIn the given report we present results of investigation of possibility to produce gas sensors on flexible substrates (polymer roll base). As gas sensitive materials were chosen glass chalcogenide semiconductors on the base of solid solutions of (As2S3)x-(As2Se3)1−x (where x=0; 0.3; 0.5; 0.7 and 1.0) and also solid solutions of As-Tl-S-Se system. Thin films of the mentioned above materials were deposited on lavsan roll film by means of thermal evaporation under vacuum conditions 10-5 Torr. At the thickness of 1-2 um the deposited layers are possessed the specific resistance in the range of 1010-1014 Ohm.cm on dependence on chemical composition.The change of conductivity of these films in the presence of gas impurity in atmosphere was used as sensitive parameter. Gas sensitive characteristics of obtained structures were tested with such toxic and inflammable environmental pollutant gases as carbon monoxide, methane, nitrogen dioxide, hydrogen and other. All measurements of gas sensitivity were performed at room temperature. For further increase of the gas sensitivity and selectivity the very thin layer of Pd was deposited onto the surface of semiconductor layer. The last one has allowed to increasing the gas sensitive characteristics by order.Through routine technology mode ready gas sensors were created. Dimensions of the developed gas sensitive elements were 1000×1000×350 μm.
High Quality Gate Insulator for Very-Low Temperature Poly-Si TFT Employing Nitrous Oxygen Plasma Pre-Treatment
Authors: Shin Moon Young , Han Sang-Myeon , Lee Min-Cheol , Shin Hee-Sun , Han Min-Koo , Kwon Jang-Yeon , Noguchi Takashi 
Published: April 2011

AbstractWe have proposed nitrous oxide (N2O) plasma pre-treatment in order to reduce the oxide charge densities as well as to increase the breakdown field of silicon dioxide film for flexible display. Our experimental results show that the proposed treatment improved both the flat-band voltage from –3V to –1.8V and the breakdown voltage of gate oxide from 7MV/cm to 9.5MV/cm, respectively. The proposed treatment also improved poly-Si TFT characteristics such as low sub-threshold swing of 0.43V/dec.
Role of Coincident Site Lattice Boundaries in Creep and Stress Corrosion Cracking
Authors: Was G.S. , Alexandreanu B. , Andresen Peter , Kumar Mukul 
Published: April 2011

AbstractInterfaces control many properties in engineering materials, several of which are critical to the integrity of the engineering structure. In single phase, solid solution, austenitic alloys, grain boundaries are often the weak link, displaying susceptibility to creep, corrosion and stress corrosion cracking. As such, grain boundary structure control affords the opportunity to improve the overall performance of alloys in a variety of applications. The role of coincident site lattice boundary (CSLB) enhancement and grain boundary connectivity is examined for how it affects the response of an alloy to stress and the environment. Specifically, the effect of grain boundary character on creep, grain boundary sliding, intergranular stress corrosion cracking, and irradiation assisted stress corrosion cracking in austenitic nickel-base (high purity Ni-Cr-Fe and alloy 600) and iron-base (high purity Fe-Cr-Ni and 304 stainless steel) alloys and for ferritic- martensitic alloy T91 is discussed.
Expressions for the effective diffusivity in materials with interphase boundaries
Authors: Belova Irina V. , Murch Graeme E. 
Published: April 2011

AbstractWe address the problem of calculating the long-time-limit effective diffusivity in stable two- phase polycrystalline material. A phenomenological model is used where the high diffusivity interphase boundaries are treated as connected “coatings” of the individual grains. Derivation of expressions for the effective diffusivity with segregation is made along Maxwell lines. Monte Carlo simulation using lattice-based random walks is used to test the validity of the expressions. It is shown that for the case analysed the derived expressions for the effective diffusivity are in very good agreement with simulation results. The equivalent of the Hart equation is also derived. It is shown to be in poor agreement with simulation results.
Dewetting on the Surface of Rutile
Authors: Gilliss Shelley R. , Ravishankar N. , Barry C. 
Published: April 2011

AbstractAfter annealing a continuous SiO2 film on the (001) surface of TiO2, the film dewets and then spreads to form a complex pattern. The final droplet morphology displays a densely branching morphology similar to those seen in computer-simulated models. It is proposed that Bénard-Marangoni convection cells form within the film before dewetting occurs. The formation of Bénard-Marangoni convection cells prior to dewetting results in the uniform size and spacing of the droplets on the surface. These convection cells form at temperature when the TiO2 substrate dissolves into the SiO2 thin film. The change in composition results in regions of differing surface tensions and therefore leads to the formation of the convection cells.
Atomic-Scale Simulation of Grain Boundary Kinetics during Recrystallization
Authors: Trautt Z. , Upmanyu M. 
Published: April 2011

AbstractWe present two-dimensional molecular dynamics (MD) simulations of symmetric tilt grain boundary kinetics, driven by stored energy of deformation. The latter is introduced by prescribing a well-defined gradient in dislocation density across a flat grain boundary. Bicrystals simulations reveal that the boundary motion, albeit jerky, increases linearly with simulation time. We also employ a control simulation to extract the driving force for motion, which then yields a unique boundary mobility. Preliminary comparisons with curvature driven boundary migration for misorientations 30° and 22.78° suggest that misorientation dependence of boundary migration is significantly less anisotropic, in turn implying that the mechanism of motion itself is different.
Synthesis and Characterization of ZnO Nanoparticles
Authors: Abhulimen I. U. , Chen X. B. , Morrison J. L. , Rangari V. K. , Bergman L. , Das K. 
Published: April 2011

ABSTRACTNanoparticles of ZnO were synthesized using a sonochemical technique. Sonochemistry arises from an acoustic cavitation phenomenon, that is, the formation, growth and implosive collapse of bubbles in a liquid medium. The ultraviolet photoluminescence (PL) studies of the samples showed a strong PL intensity and a significant blue shift relative to the PL of the bulk. Shifts up to 70 meV were observed and attributed to a confinement effect. Scanning electron microscopy indicated roughly spherical particles, ∼160 nm in diameter. However, nano-platelets and rods were observed in transmission electron micrographs. Preliminary electrical measurements indicated a highly resistive nature of the nanoparticulate material.
Growth, Characterization, and Application of High Al-content AlGaN and High Power III-Nitride Ultraviolet Emitters
Authors: Ren Z. , Jeon S.-R. , Gherasimova M. , Cui G. , Han J. , Peng H. , Song Y. K. , Nurmikko A. V. , Zhou L. , Goetz W. , Krames M. , Cho H.-K. 
Published: April 2011

ABSTRACTA study of Si-doped and Mg-doped AlxGa1-xN up to × ∼ 50 % and the characteristics of ultraviolet (UV) light emitting diodes (LEDs) with emission wavelengths at 340 nm and 290 nm are reported. By using grading super-lattices (SLs) before n-type AlGaN growth, surface roughness is much improved. Resistivity of 2.9×10-2 Ωcm and free electron concentrations of 2.9×10 cm- are achieved for n-type Al0.45Ga0.55N. The viability of effective p-type doping is defined by a minimum concentration of Mg required to offset the background impurities and, more importantly, a maximum limit above which inversion domains and structural defects start to nucleate, accompanied by a rapid degradation of electrical transport. Resistivity of 10 Ωcm and free hole concentrations above 1017 cm−3 are achieved for AlxGa1-xN up to × ∼ 50 % within an optimum window of Mg incorporation. Output powers up to 1.5 mW from small area 340 nm LEDs (< 100 μm diameter) and 110 μW from 290 nm LEDs (100 μm diameter) directly off a planar chip have been achieved under DC condition. For large area encapsulated lamp (1×1 mm2 device area and 0.52 mm2 mesa area), output power of 79 mW from 340 nm LEDs and 8.5 mW from 290 nm LEDs are achieved under pulse mode (1kHz, 2% duty factor).
Junction Temperature Measurements in Deep-UV Light-Emitting Diodes
Authors: Xi Y. , Xi J.-Q. , Gessmann Th. , Shah J. M. , Kim J. K. , Schubert E. F. , Fischer A. J. , Crawford M. H. , Bogart K. H. A. , Allerman A. A. 
Published: April 2011

ABSTRACTThe junction temperature of AlGaN/GaN ultraviolet (UV) Light-Emitting Diodes (LEDs) emitting at 295 nm is measured by using the temperature coefficients of the diode forward voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-forward voltage is the most accurate method (± 3 °C). A theoretical model for the dependence of the diode junction voltage (Vj) on junction temperature (T) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6 K/W is obtained with the AlGaN/GaN LED sample mounted with thermal paste on a heat sink.
Nitride-Based Light-Emitting Diodes Grown on Particular Substrates: ZrB2,(3038) 4H-SiC and r-faced Sapphire.
Authors: Kamiyama Satoshi , Iwaya Motoaki , Amano Hiroshi , Akasaki Isamu 
Published: April 2011

ABSTRACTNew substrate materials; ZrB2,(3038) 4H-SiC and r-faced sapphire, are evaluated for use in nitride-based light-emitting diodes (LEDs). They are thought to be suitable for low-cost, short-wavelength, and highly efficient light-emitting devices. The ZrB2 substrate presents a high-quality nitride layers and a blue-violet LED with an excellent L-I curve. A vertical electrical transport is also possible due to its preferable work function and high electrical conductivity. Nitride layers tilted 54.7° from the c-plane can be grown on (3038) 4H-SiC. The LED grown on the (3038) 4H-SiC substrate shows a smaller blue shift of the EL peak wavelength with increasing driving current. Although the crystalline quality of nitride layers on r-faced sapphire was improved with the optimization of the misorientation angle, the performance of blue-violet LEDs is still low. Further work is needed to enable the practical application of r-faced sapphire to nitride-based LEDs.
Pressure dependence of elastic constants in wurtzite and zinc-blende nitrides and their influence on the optical pressure coefficients in nitride heterostructures
Authors: Łepkowski Sławomir P. , Majewski Jacek A. 
Published: April 2011

ABSTRACTWe have studied the nonlinear elasticity effects in III-N compounds. Particularly, we have determined the pressure dependences of elastic constants in wurtzite and zinc-blende InN, GaN, and AlN by performing ab-initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. We have found that C11, C12 in zinc-blende phase and C11, C12, C13, C33 in wurtzite phase depend significantly and almost linearly on hydrostatic pressure, for all considered nitrides. Much weaker dependences on pressure have been observed for C44 in both wurtzite and zinc-blende phases. Further, we have examined the influence of pressure dependence of elastic constant on the pressure coefficient of light emission, dEE / dP, in wurtzite and cubic, InGaN/GaN and GaN/AlGaN quantum wells. We show that the pressure dependence of elastic constants results in significant reduction of dEE / dP in nitride quantum wells and essentially improves the agreement between experimental and theoretical values.
Relationship of basal plane and prismatic stacking faults in GaN to low temperature photoluminescence peaks at ∼3.4 eV and ∼3.2 eV
Authors: Bai J. , Dudley M. , Chen L. , Skromme B. J. , Hartlieb P. J. , Michaels E. , Kolis J. W. , Wagner B. , Davis R. F. , Chowdhury U. , Dupuis R. D. 
Published: April 2011

ABSTRACTThe relationship between the optical properties and microstructure of GaN is of great interest due to the important optical and electronic applications of this material. Several different studies have been reported attempting to link the low temperature photoluminescence (PL) peak at ∼3.4 eV to the presence of various microstructural defects. However, no clear systematic studies have been reported establishing such a link for the PL peak observed at ∼3.2 eV. In this paper, we present evidence linking the ∼3.4 eV PL peak to the presence of a thin layer of cubic phase associated with basal plane stacking faults (BSF). This relationship is mainly established by studying a series of ammonothermally-grown GaN bulk crystals. The existence and strength of the ∼3.4 eV peak are found to be related to the I2 type BSF (RI2=1/3<1>) observed in these samples. To investigate the relationship between the ∼3.2 eV peak and structural defects, a series of GaN epilayers grown on either SiC or sapphire (of various off-cut angles) was investigated by TEM and PL spectroscopy. Samples grown on 3.5° off-cut SiC and 5° and 9° off-cut sapphire substrates exhibit PL peaks near ∼3.2 and ∼3.4 eV, which are absent in the on-axis SiC and sapphire cases. TEM shows that the former group of samples has defect configurations consisting of prismatic stacking faults (PSFs) folding back and forth between two different {1120} planes connected by stair rod dislocations, which in turn fold onto to I1 type BSFs again with stair rod dislocations at the fault intersections. The ∼3.2 eV PL peaks are proposed to possibly arise from transitions involving the PSFs and the stair rods associated with their mutual intersections and their intersections with the BSFs. The ∼3.4 eV peak is again attributed to the thin layer of cubic phase associated with the I1 type BSF (three bilayers as opposed to four bilayers for the I2 type BSF).
Direct AFM Observation of Strain Effects on MOCVD-Grown GaN Epilayer Surface Morphology
Authors: Florescu D.I. , Lee D.S. , Ramer J.C. , Merai V.N. , Parekh A. , Lu D. , Armour E.A. , Quinn W.E. 
Published: April 2011

ABSTRACTIn this study, we investigate the dependence of GaN surface morphology on the absolute strain values for thin (<10 μm) epitaxial films grown by MOCVD on c-plane sapphire substrates of various miscut angles towards the m-plane. Results indicate an excellent correlation between the surface roughness observed employing an AFM tool and epilayer strain values. An overall increase of surface roughness (decrease of atomic terrace width) is found with decreasing compressive strain (epilayer vs. bulk value). In addition, sapphire substrates with increasing miscut angle (0.30 deg) appear to relax the inherent, built-in strain differently in the vertical (growth) direction when compared to just (0.00 deg) substrates. Strain relaxation by typical V-shaped, hexagonal pits is directly imaged through the comparison of surface features inside and outside of pits in the thin GaN epilayer films.
X-ray Excited Optical Luminescence Studies of InGaN and Rare-Earth Doped GaN Epilayers
Authors: Katchkanov V. , Mosselmans J.F.W. , O'Donnell K.P. , Poolton N.R.J. , Hernandez S. 
Published: April 2011

ABSTRACTA successful attempt to use X-ray Excited Optical Luminescence (XEOL) for the detection of Extended X-ray Absorption Fine Structure (EXAFS) in III-nitrides is reported. The samples studied were InGaN and rare-earth (RE) doped GaN epilayers. For the first time Ga K-edge EXAFS oscillations were measured by monitoring the well-known “yellow” emission of GaN at 560 nm. The analysis of Optically Detected (OD) EXAFS data confirmed the expected local structure for Ga in GaN. The intensity oscillation of the “yellow” band when X-ray energy was scanned across the Ga K-edge indicates that core excitation of Ga atom has a high probability of transfer to defects responsible for “yellow” emission.
Discrete Steps in the Capacitance-Voltage Characteristics of GaInN/GaN Light Emitting Diode Structures
Authors: Xia Y. , Williams E. , Park Y. , Yilmaz I. , Shah J.M. , Schubert E.F. , Wetzel C. 
Published: April 2011

ABSTRACTA detailed modeling of the electronic bandstructure of GaInN alloys and GaInN/GaN heterostructures typically used for high efficiency light emitting diodes is of high relevance for future improvements. Here we are exploring opportunities to accurately quantify the carrier dynamics under forward and reverse voltage bias. In GaInN/GaN LED-type heterostructures we observe distinct steps in the junction capacitance as a function of bias voltage within the depletion regime. Up to three individual steps can be identified that correspond to alternating ranges of capacitive and resistive impedances. Our analysis suggests that we are quantitatively monitoring the electron concentration in each individual quantum well. The pronounced clarity of the data reveals a high level of epitaxial perfection and spatial homogeneity across the entire area of the junction.
Impact of Manganese incorporation on the structural and magnetic properties of MOCVD-grown Ga1−xMnxN
Authors: Kane Matthew H. , Asghar Ali , Strassburg Martin , Song Qing , Payne Adam M. , Summers Christopher J. , John Zhang Z. , Dietz Nikolaus , Ferguson Ian T. 
Published: April 2011

ABSTRACTThis paper reports the impact of the Mn incorporation on the structural and magnetic properties of Ga1−xMnxN on the metal-organic vapor phase deposition (MOCVD). Crystalline quality and phase purity were determined by high-resolution X-ray diffraction and indicated that no macroscopic second phases are formed during growth. Atomic force microscopy revealed a 2-dimensional MOCVD step-flow growth pattern in the Mn-incorporated samples. Various annealing steps were applied to some of the samples to reduce compensating defects and to investigate the effects of post processing on the growth. SQUID measurements showed an apparent ferromagnetic hysteresis behavior. However, none of the requirements for room temperature ferromagnetism in the prevailing mean field DMS theories were found. Therefore, different origins of the ferromagnetic signal are discussed.