bluuebunny/crossref_metadata_2025 huggingface dataset:
(S)-1-[N-(Benzylidene)hydrazinylcarbonyl]-2-hydroxyethylcarbamate esters: layered structures created from X—H···O (X = N,O) hydrogen-bonds
Authors: Howie R. Alan , de Souza Marcos V. N. , Pinheiro Alessandra , Kaiser Carlos R. , Wardell James L. , Wardell Solange M. S. V.
Published: March 2011

The molecular structures of tert-butyl (S)-2-hydroxy-[N-(substituted-benzylidene)hydrazinyl-carbonyl]-ethylcarbamates, C15H20N3O4X (3: X = H, o-OH, o-NO2, m-NO2 and p-CN), derived from L-serine, are formally rather similar. Despite the variation in substituent, X, tricälinic (3: X = H), (3: X = o-OH), (3: X = m-NO2)and(3: X = p-CN) are isostructural and exhibit, with minor variations, the same fundamental intermolecular O—H···O and N—H···O hydrogen-bond connectivity in two-dimensions in layers of molecules. In monoclinic(3: X = o-NO2), however, the oxygen atoms of the nitro group function as additional O—H···O and N—H···O hydrogen-bond acceptors resulting in a more complex form of two-dimensional connectivity.
Combining halogen and hydrogen bonding in the 1 : 1 molecular salt (hexamethylenetetraminium) · (p-iodobenzoate) to form 1-D zig-zag chains
Authors: Lemmerer Andreas
Published: March 2011

The crystal structure of the molecular salt (hexamethylenetetraminium) · (p-iodobenzoate) is the first example of a complex using the hexamethylene (HMTA) molecule that has both halogen and hydrogen bonding. The desired supramolecular packing arrangement of 1-D zig-zag chains was observed. A detailed breakdown of related HMTA complexes in the literature was used to show that zig-zag chains are a common packing feature of HMTA complexes with bifunctional molecules. The crystal structure determination of the molecular salt shows that the two intermolecular interactions N—H+···OOC– and N···I are positionally disordered around a centre of inversion.
India in 2010
Authors: Sharma Shalendra
Published: March 2011

The Congress Party, although in a strong position to improve matters in 2010, generally proved disappointing, especially in the realm of governance and public policy. However, Indian authorities did demonstrate the ability to manage the economy well in a challenging international economic climate. President Obama's three-day trip helped to reinvigorate bilateral ties, but India's relations with China and Pakistan remained testy.
China in 2010
Authors: Wu Guoguang
Published: March 2011

China in 2010 followed two divergent tracks: one pursued continued high-speed economic growth while the other witnessed an ongoing rise of social discontent. Both confirmed the failure of government efforts to promote so-called "scientific," or balanced, development. Political disillusion over the "China model" surfaced; China's diplomacy saw many setbacks.
Timor-Leste in 2010
Authors: Arnold Matthew B.
Published: March 2011

Timor-Leste in 2010 continued to stabilize following the political and social crisis of 2006–08. With strong economic growth and a calm security situation, the year was defined by twin national debates that will dominate the country's long-term future: how to manage its significant energy resources and how best to use the accruing wealth.
Japan in 2010
Authors: Rosenbluth Frances Mccall
Published: March 2011

The Democratic Party of Japan's first full year in office was rocky, with open competition for party leadership sandwiched between diplomatic rows with the U.S. and China. If bumps in the road are inevitable for a new party in government, the Japanese public has made an investment in the long-term health of its democracy.
The United States and Asia in 2010
Authors: Godement François
Published: March 2011

As China asserts itself, neighbors look to the United States for support. The Obama administration is providing it, but faces multiple issues, from Korea to the Afghan situation. U.S. policy toward China is being frustrated on maritime, military, and currency issues. America is balancing engagement, security reassurances, and conflict avoidance.
Taiwan in 2010
Authors: Tien Hung-Mao , Tung Chen-Yuan
Published: March 2011

The November 2010 urban mayoral elections in Taiwan will set the stage for national elections in 2012 between the Nationalist Party and the rising Democratic Progressive Party. Meanwhile, Taiwan and China successfully concluded the Economic Cooperation Framework Agreement in summer 2010, deepening economic ties across the Taiwan Strait.
Pakistan in 2010
Authors: Fair C. Christine
Published: March 2011

The 2010 floods exacerbated Pakistan's lingering domestic weaknesses including fraught civil-military relations, perilous economic conditions, and the ineptitude of the civilian government. While a military coup is unlikely anytime soon, army chief Ashfaq Pervez Kayani continues to consolidate his personal power, despite his cultivated democratic credentials, and that of the army, at the expense of the civilian leadership. The differences in the strategic interests of Pakistan and the U.S. seem stark, especially as the latter seeks to develop an exit strategy that would permit a cessation of its military action in Afghanistan.
Localisation of the melanocortin-2-receptor and its accessory proteins in the developing and adult adrenal gland
Authors: Gorrigan Rebecca J , Guasti Leonardo , King Peter , Clark Adrian J , Chan Li F
Published: March 2011

The melanocortin-2-receptor (MC2R)/MC2R accessory protein (MRAP) complex is critical to the production of glucocorticoids from the adrenal cortex. Inactivating mutations in either MC2R or MRAP result in the clinical condition familial glucocorticoid deficiency. The localisation of MC2R together with MRAP within the adrenal gland has not previously been reported. Furthermore, MRAP2, a paralogue of MRAP, has been shown in vitro to have a similar function to MRAP, facilitating MC2R trafficking and responsiveness to ACTH. Despite similar MC2R accessory functions, in vivo, patients with inactivating mutations of MRAP fail to be rescued by a functioning MRAP2 gene, suggesting differences in adrenal expression, localisation and/or function between the two MRAPs. In this study on the rat adrenal gland, we demonstrate that while MRAP and MC2R are highly expressed in the zona fasciculata, MRAP2 is expressed throughout the adrenal cortex in low quantities. In the developing adrenal gland, both MRAP and MRAP2 are equally well expressed. The MC2R/MRAP2 complex requires much higher concentrations of ACTH to activate compared with the MC2R/MRAP complex. Interestingly, expression of MC2R and MRAP in the undifferentiated zone would support the notion that ACTH may play an important role in adrenal cell differentiation and maintenance.
Identification of Novel Ras-Cooperating Oncogenes in Drosophila melanogaster: A RhoGEF/Rho-Family/JNK Pathway Is a Central Driver of Tumorigenesis
Authors: Brumby Anthony M , Goulding Karen R , Schlosser Tanja , Loi Sherene , Galea Ryan , Khoo Peytee , Bolden Jessica E , Aigaki Toshiro , Humbert Patrick O , Richardson Helena E
Published: March 2011

We have shown previously that mutations in the apico-basal cell polarity regulators cooperate with oncogenic Ras (RasACT) to promote tumorigenesis in Drosophila melanogaster and mammalian cells. To identify novel genes that cooperate with RasACT in tumorigenesis, we carried out a genome-wide screen for genes that when overexpressed throughout the developing Drosophila eye enhance RasACT-driven hyperplasia. RasACT-cooperating genes identified were Rac1 Rho1, RhoGEF2, pbl, rib, and east, which encode cell morphology regulators. In a clonal setting, which reveals genes conferring a competitive advantage over wild-type cells, only Rac1, an activated allele of Rho1 (Rho1ACT), RhoGEF2, and pbl cooperated with RasACT, resulting in reduced differentiation and large invasive tumors. Expression of RhoGEF2 or Rac1 with RasACT upregulated Jun kinase (JNK) activity, and JNK upregulation was essential for cooperation. However, in the whole-tissue system, upregulation of JNK alone was not sufficient for cooperation with RasACT, while in the clonal setting, JNK upregulation was sufficient for RasACT-mediated tumorigenesis. JNK upregulation was also sufficient to confer invasive growth of RasV12-expressing mammalian MCF10A breast epithelial cells. Consistent with this, HER2+ human breast cancers (where human epidermal growth factor 2 is overexpressed and Ras signaling upregulated) show a significant correlation with a signature representing JNK pathway activation. Moreover, our genetic analysis in Drosophila revealed that Rho1 and Rac are important for the cooperation of RhoGEF2 or Pbl overexpression and of mutants in polarity regulators, Dlg and aPKC, with RasACT in the whole-tissue context. Collectively our analysis reveals the importance of the RhoGEF/Rho-family/JNK pathway in cooperative tumorigenesis with RasACT.
Parenteral Nutrition in the Neonatal Intensive Care Unit
Authors: ElHassan Nahed O. , Kaiser Jeffrey R.
Published: March 2011

Neonatal parenteral nutrition (PN) is readily available in many hospitals and plays an essential role in the management of sick and growing preterm and term infants. PN can be used as the sole source of nutrition support for infants who cannot be fed or as an adjunct to enteral feeding. Preterm infants are a particularly vulnerable population because they are born at a time, if they had remained in utero, of rapid intrauterine brain and body growth. The impact of early malnutrition can have long-lasting negative effects on central nervous system development and growth. Despite this, PN is often provided to preterm infants based on local traditions rather than experimental evidence. The quality of PN and its early initiation are critical in providing the most adequate substrates for appropriate development. This article reviews the energy and fluid requirements of infants and presents by component (protein, carbohydrates, lipids, minerals such as calcium and phosphorus, trace elements, and multivitamins) the available literature on neonatal PN and its complications. In addition, suggested guidelines for PN administration for preterm and term neonates are presented.
Transition to Oral Feeding in Preterm Infants
Authors: Sridhar Sunita , Arguello Stacey , Lee Henry Chong
Published: March 2011

Learning to eat is an integral aspect of a preterm infant's development. It is especially important to ensure that infants are able to breastfeed effectively and transition safely from other types of feeding. This article describes the mechanisms of sucking and swallowing involved in oral feeding and proposes strategies to address the challenges that preterm infants face in transitioning to breast- or bottle-feeding.
Pharmacology Review
Authors: Hibbs Anna Maria
Published: March 2011

The common pharmacologic strategies used to treat gastroesophageal reflux disease (GERD) in the neonatal intensive care unit (NICU) include suppression of gastric acid with histamine-2 (H2) receptor antagonists and proton pump inhibitors (PPIs) and stimulation of gastrointestinal motility with dopamine receptor antagonists or motilin receptor agonists. These medications are primarily metabolized by hepatic cytochrome P450 (CYP) enzymes. Although frequently used, none of these drugs has strong evidence for efficacy in decreasing the complications of reflux in preterm infants or term neonates. In addition, a few well-conducted, masked, randomized studies that have accounted for maturational changes in their design have raised concerns about the safety of these medications in infants.
A Leed Investigation of (111) Oriented Si, Ge and GaAs Surfaces Following Pulsed Laser Irradiation
Authors: Zehner D. M. , Noonan J. R. , Davis H. L. , White C. W. , Ownby G. W.
Published: March 2011

The low energy electron diffraction (LEED) patterns obtained from clean (111) oriented Si, Ge and GaAs single crystals subsequent to their irradiation with the output of a pulsed ruby laser in an ultra-high vacuum (UHV) environment suggest that metastable (1×1) surface structures are produced in the regrowth process. Conventional LEED analyses of the Si and Ge surfaces suggest that they terminate in registry with the bulk but that the two outermost interlayer spacings differ from those of the bulk. For the case of Si these changes are a contraction of 25.5 ± 2.5% and an expansion of 3.2 ± 1.5% between the first and second and second and third layers respectively.
Direct Measurement of Cw Laser-Induced Crystal Growth Dynamics by Time-Resolved Optical Reflectivity
Authors: Olson G.L. , Kokorowski S.A. , Roth J.A. , Hess L.D.
Published: March 2011

We report the use of time-resolved optical reflectivity to directly monitor the dynamics of cw laser-induced solid phase epitaxy (SPE) of thin films. This in situ measurement technique utilizes optical interference effects between light reflected from the surface of a sample and from an advancing interface to provide continuous temporal and spatial resolution of crystal growth processes. SPE growth rates of ionimplanted films which are five orders of magnitude faster than previously observed can be induced and accurately measured with the laser method. Arsenic enhances the SPE rate, and spatially resolved measurements show that the growth rate for arsenic implanted films varies in accordance with the ionimplantation profile. Results are reported for silicon selfimplanted samples with and without subsequent arsenic ion implantation, and for silicon samples directly implanted with arsenic.
Real Time Monitoring Of The Optical Properties Of Cw Laser Annealed Silicon
Authors: Ready John F. , Thompson Mcclure B. , Brewer Terry L. , Larson William L.
Published: March 2011

The surface reflectivity of ion implanted silicon is a function of the entire past history of the material, including the nature of the implanted species and the implant dose. It is influenced by interference effects, arising from discontinuities in index of refraction at the surface and at the boundary between damaged and undamaged material. The reflectivity may be either higher or lower than that of the unimplanted silicon. As the crystalline silicon regrows from below, the reflectivity changes because of variable constructive or destructive interference. This paper describes monitoring of the surface reflectivity during continuous laser annealing. The beam from a continuous argon ion laser is scanned in a raster pattern over the silicon surface. The surface reflectivity for a HeNe laser beam is monitored as a function of time during crystalline regrowth. The reflectivity contains an oscillatory component which arises because of changes in interference due to the decreasing thickness of the noncrystalline layer. The oscillatory behavior produces a signature characteristic of the annealing. The reflectivity monitoring technique is useful for investigating the influence of parameters such as the spatial profile of the laser beam and the implantation dose on the annealing characteristics. The results are correlated with measurements of the depth profile of the implanted ions, as revealed by anodic oxidation and stripping.
Infrared Optical Properties of Ion Implanted and Laser Annealed Silicon
Authors: Miyao Masanobu , Motooka Teruaki , Natsuaki Nobuyoshi , Tokuyama Takashi
Published: March 2011

Electronic states of extremely heavily doped n-type Si obtained by high dose ion implantation and laser annealing are investigated by measuring the infrared optical properties. Free carrier effective mass (m*) and carrier relaxation time (τ) are obtained as a function of carrier concentration (1019−5×1021 cm−3). Values of m* and τ increase and decrease, respectively, with the increase of carrier concentration. These results are discussed in relation to the occupation of electrons in a new valley of the conduction band.
Pulsed Laser Annealing Effects in High Dose Rate Silicon Implants
Authors: Williams J.S. , Pogany A. P. , Beanland D. G. , Chivers D. J. , Kenny M. J. , Rose A. , Scott M. D.
Published: March 2011

High resolution Rutherford backscattering and channelling TEM and electrical measurements have been employed to investigate pulsed-ruby laser annealing effects in high dose rate ion implanted silicon wafers. The laterally non-uniform, part amorphous, part crystalline disordered structure which can result from high dose rate implants has been utilized to investigate the selective removal of amorphous or crystalline damage at near-threshold laser powers. Evidence is found for preferrential recrystallisation of amorphous damage regions over a broad laser power window which is below the threshold power required to melt adjacent crystalline silicon. At laser power levels above the crystalline-to-melt threshold, excellent uniformity in damage removal and electrical properties were obtained over the entire wafer.
Heterogeneous Nucleation of Spatially Coherent Damage Structures in Crystalline Silicon with Picosedcond 1.06 μm and 0.53 μm Laser Pulses
Authors: Walser R.M. , Becker M.F. , Ambrose J.G. , Sheng D.Y.
Published: March 2011

Several types of periodic ripple structures have been observed on the surface of solids that have been laser irradiated with beam intensities near their melting thresholds.1-7 We restrict our attention here to the coherent, onedimensional (RD) gratings induced by linearly polarized beams.3-7 These gratings have a period close to the free space laser wavelength (λ0) for normally incident beams and are normally found in the beam spot near the melt boundary (Fig. 1). The grating lines are always perpendicular to the optical electric field Ei independent of the crystallographic orientation of the sample.
Multiple-Scan E-Beam Method Applied to a Range of Semiconducting Materials
Authors: Shah N.J. , Mcmahon R.A. , Williams J.G.S. , Ahmed H.
Published: March 2011

This paper describes the conditions for activating ion implants in a range of semiconductor materials in the solid state. This includes phosphorus and arsenic implants into silicon, boron and phosphorus implants into SOS, gallium into germanium and silicon into gallium arsenide. For each material the restoration of electrical activity correlates with structural data from RBS analysis. Negligible implant diffusion occurs for the typical annealing treatments which result in full activation of dopants.
Transient and Furnace Annealing of Ion Implanted Gallium Arsenide
Authors: Williams J. S. , Harrison H. B.
Published: March 2011

This review examines the annealing behaviour of ion implanted gallium arsenide during furance, laser and e-beam processing.The two annealing regimes, namely solid phase regrowth via furnace or CW laser/e-beam annealing and liquid phase epitaxy produced by pulsed lasers/e-beam, are examined in some detail.Emphasis is placed upon an understanding of the physical processes which are important during the various annealing modes.Comparison with the annealing behaviour of ion implantedelemental semiconductors(notably silicon) is made throughout the review to highlight relevant similarities and differences between compound and elemental semiconductors.The electrical properties of annealed gallium arsenide layers are not treatedin any detail, although particular observations which are relevant to the annealing processes are briefly discussed.
Pulsed Ruby Laser Annealing of Zn, Mg, Se and Si Ion Implants in Semiconducting Gaas
Authors: Lowndes Douglas H. , Cleland J. W. , Christie W. H. , Eby R. E.
Published: March 2011

The properties of p+ and n+ layers formed by pulsed ruby laser annealing (PRLA) of shallow (Rp ~ 320–680 Å) implantations of Mg, Zn, Si and Se ions in both n- and p-type semiconducting GaAs have been evaluated using a combination of SIMS and electrical properties measurements. High activation (> 80%) was obtained for high dose (5 × 1015 ions/cm2 ) implants of both Mg and Zn, within a pulsed laser energy density “window” 0.5 ≤ Eλ ≤ 0.8 J/cm2 (FWHM pulse duration = 20–25 ns). SIMS measurements following PRLA show a wellbehaved increasing penetration of dopant ions into the GaAs substrate, with dopant ion concentrations well in excess of 1020 ions/cm3 in the near-surface region. Measured hole mobilities are consistent with the values anticipated for these high concentrations of ionized impurity scattering centers.
Computer Model of the Temperature and Carrier Concentration Induced in Si by Nanosecond and Picosecond Laser Pulses
Authors: Lietoila Arto , Gibbons James
Published: March 2011

A set of simultaneous equations for lattice temperature, carrier concentration and carrier temperature in Si is numerically solved for typical nanosecond and picosecond laser pulses. The calculated threshold energies required to reach Si melting temperature are consistent with measured thresholds to reach a flat-top reflectivity of ~ 70% for typical nanosecond pulses at 1.06 and .53 µm. In the picosecond regime, almost the entire pulse energy is at first stored in the carrier system, and a carrier temperature exceeding 30,000 K is achieved for a 3 J/cm2, 30 ps pulse at 1.06 µm. In this case, the surface carrier concentration reaches a high enough value to cause an enhanced reflectivity from the plasma lasting for at least 0.1 ns. The lattice temperature reaches 1410°C, while carriers relax their energy to the lattice after the pulse, and the energy stored in the carrier system would be enough to supply the heat of fusion at the silicon surface.
Behavior of Metastable Te Donor Concentrations in Q-Switched Ruby Laser Annealed GaAs
Authors: Pianetta P. , Amano J. , Woolhouse G. , Stolte C. A.
Published: March 2011

The thermal behavior of Te implanted, laser annealed GaAs was investigated by helium backscattering spectroscopy and transmission electron microscopy in order to correlate structural changes with the two stage reduction in the carrier concentration due to post laser anneal heating above 200°C. The activation energy for stage one which occurs in the range 200–400°C was determined to be approximately 1.3 eV. Post laser anneal heating at 450°C caused no observable structural changes. On the other hand, 850°C post laser anneal heating induced the formation of precipitates and dislocation loops as well as narrowing the channeling half-angle of Te by about 11%.
Pulse Diffused N+ Layers in GaAs
Authors: Eirug Davies D. , Ryan T.G. , Lorenzo J.P. , Kennedy E. F.
Published: March 2011

Pulse diffusion has been used for doping GaAs n-type to over 1019 cm−3. Surface arsenic loss is avoided through using As2Se3 as the diffusion source. A reduction in electrical activity similar to that reported for pulse annealed implanted layers occurs with any subsequent heat treatment. A resistive region, found at the surface of the profile, can be circumvented through additionally heating the GaAs thermally during the pulse diffusion and reducing the rapidity of the quench.
Threshold Energy Density for Pulsed Laser Annealing of Silicon
Authors: Hoonhout Dick , Saris Frans
Published: March 2011

We have made a systematic investigation of the threshold energy density for recrystallization of ion-implanted silicon by Q-switched laser irradiation as function of thickness of the disordered layer, temperature during implantation, type and dose of implanted impurity, laser wavelength, and substrate orientation. Most results have been obtained with a Q-switched ruby laser. A linear dependence of the threshold on layer thickness (in the region of 60–300 nm) was found for arsneic-implanted silicon, but not for silicon-implanted silicon. For an amorphous layer thickness of 200 nm we found very little dependence of the threshold on type of dopant. In the case of the Nd:YAG laser, however, the lowest threshold was observed for column VI elements, the highest for column IV elements and intermediate and equal thresholds for the elements from column III and B. The influence of temperature during implantation was found to be small, but the threshold appeared to be different for (100)- and (111)- oriented substrates.
C-V and Capacitance Transient Analysis of Self-Implanted Amorphous Si Layers Regrown by Swept-Line Electron Beam (Sled) Annealing
Authors: Soda K. J. , Dejule R. Y. , Streetman B. G.
Published: March 2011

It is demonstrated that swept-line electron beam (SLEB) annealing can be successfully employed to recrystallize relatively deep (∼0.5 μm) Si-implanted amorphous silicon layers. DLTS and C-V analysis of these layers show significant reductions in concentration of residual defects and magnitude of dopant redistribution effects. For comparison, similar data for furnace annealed material is also presented.
Silicon Bipolar Transistors Fabricated using Ion Implantation and Laser Annealing
Authors: Natsuaki Nobuyoshi , Miyazaki Takao , Ohkura Makoto , Nakamura Toru , Tamura Masao , Tokuyama Takashi
Published: March 2011

Bipolar transistors with laser annealed base and emitter, as well as those with furnace annealed base and laser annealed emitter, have been successfully fabricated using Q-switched ruby laser pulse irradiation. The performance of laser asannealed transistors is rather poor. However, it can be improved, to some extent, by relatively low temperature furnace annealing after laser irradiation. DC and RF characteristics of laser annealed transistors are presented in conjunction with laser irradiation effects on the characteristics of conventionally fabricated transistors.
Laser-Induced Solid Phase Epitaxy of Silicon Deposited Films
Authors: Roth J.A. , Olson G.L. , Kokorowski S.A. , Hess L.D.
Published: March 2011

A comparative study of solid phase epitaxy (SPE) of deposited and ion-implanted amorphous Si films was conducted with the use of a newly developed laser technique. The effects of interface contaminants and contaminants distributed within a deposited film on the rate of SPE and final crystal quality are reported. In the absence of impurities, deposited Si films crystallize at the same rate as ion-implanted layers and yield epitaxial films with comparable crystal quality. The presence of impurities in deposited films at the interface or distributed within the film can severely retard the SPE growth, causing several deleterious effects which ultimately degrade the film quality. These effects are more severe at high temperatures.
Laser Crystallization of Deposited Silicon Films
Authors: Celler G. K. , Leamy H. J. , Aspnes D. E. , Doherty C. J. , Sheng T. T. , Trimble L. E.
Published: March 2011

Silicon layers evaporated on crystalline Si have been crystallized by Q-switched Nd:YAG laser irradiation. A strong correlation was observed between the density of a-Si films and the quality of the epitaxial regrowth from the liquid phase. Dense films crystallized epitaxially in a wide range of laser energy densities. Layers with 20% lower density, as determined by spectroscopic ellipsometry, had higher crystallization thresholds and suffered from severe pitting of the surface. Coalescence of the excess void volume into microbubbles, stabilized by gaseous contaminants, is responsible for the surface degradation.

In polycrystalline films on amorphous insulating substrates laser melting changes the grain distribution. Rapid melting and solidification of small diameter spots creates concentric rings of large crystallites. This characteristic pattern is explained by a simple model, based on the kinetics of crystallization.
Laser Induced Controlled Nucleation and Growth Process For Large Grained Polycrystalline Silicon
Authors: Danforth S.C. , Van Gieson F. , Haggerty J.S. , Kohatsu I.
Published: March 2011

Research on a new process is described which utilized a laser to achieve controlled crystallization of amorphous Si thinfilms for photovoltaic applications. Amorphous Si films are deposited on suitable substrates using RF sputtering. A laser is used to inoculate these films with crystalline embryos at specific locations. These embryos should then grow in a controlled atmosphere annealing furnace under conditions optimized to maintain the nucleation rate at zero and the transformation rate (from amorphous to crystalline silicon) at a maximum value. The result will be a polycrystalline silicon film with a large grain size to film thickness ratio, where the ultimate grain size will be determined by the laser inoculation spacing.
Cw Laser-Recrystallized Polysilicon as A Device-Worthy Material
Authors: Gibbons James F.
Published: March 2011

The basic crystallographic and electronic properties of cw laser recrystallized thin polysilicon films are presented and shown to be suitable for fabrication of MOSFET devices. Devices and simple integrated circuits fabricated to explore the potential of this material have electrical characteristics similar to devices fabricated on single crystal material and offer significant promise for future applications.
Processing and Properties of Cw Laser-Recrystallized Silicon Films on Amorphous Substrates
Authors: Johnson N. M. , Biegelsen D. K. , Moyer M. D.
Published: March 2011

CW laser recrystallization has been used to process silicon thin films as an integral step in semiconductor device fabrication. On continuous films of polycrystalline silicon, a silicon-nitride encapsulant is used to control surface morphology during laser recrystallization. For thin films on bulk glass substrates it is necessary to pattern the silicon layer in order to minimize microcracking as well as to control recrystallization. Over single crystal silicon substrates, test devices have been fabricated in silicon islands on dual-dielectric layers. Materials and device evaluation included TEM, current-voltage, capacitance-voltage, and EBIC measurements, and the test devices consisted of p-n junction diodes, MOS capacitors, and MOS field-effect transistors.
Laser Induced Crystal Growth of Silicon Islands on Amorphous Substrates
Authors: Biegelsen D. K. , Johnson N. M. , Bartelink D. J. , Moyer M. D.
Published: March 2011

The importance of controlled lateral heat flow in the growth of single crystal silicon islands on amorphous substrates is demonstrated. In one approach the thermal profile on and around the islands is determined by varying the optical absorption with a variety of thin film structures. In another, beam spot shaping is used. Competitive nucleation is suppressed and continued in-plane epitaxial zone growth is enhanced. In this way we are able to produce single crystal islands 20μm wide and >20μm long. Routine production of such islands would enable new thin film transistor technologies.
Laser Growth of Thin Silicon Crystals in Patterned Structures
Authors: Fastow R. M. , Leamy H. J. , Celler G. K. , Wong Y. H. , Doherty C. J.
Published: March 2011

Beam processing can be applied to thin, polycrystalline silicon films on amorphous substrates to: a( increase grain size, b( produce single, isolated crystals, and c( to produce oriented single crystals. Specific methods for these tasks are outlined. Crystal growth and heat flow consideration appropriate to each are presented.
Beam Induced Reactions in Metal-Film Systems
Authors: Lau S. S. , Mäenpää Martti , Mayer James W.
Published: March 2011

Pulsed beams (laser, electron, or ion) and ion beams (ion beam mixing) have been used to induce structural and compositional changes in metal-metal and metal-semiconductor thin-film structures. Metastable crystalline and amorphous phases have been formed. Although ultra fast quenching occurs with both techniques, metastable phases are formed by quenching from the liquid with pulsed beams and from the solid-phase with ion-induced reactions. With both techniques metastable phases can be formed over a broader compositional range than with conventional melt-quench methods.
Laser Irradiation of Nickel: Defect Structures and Surface Alloying
Authors: Buene L. , Jacobson D.C. , Nakahara S. , Poate J.M. , Draper C.W. , Hirvonen J.K.
Published: March 2011

Surface layers of Ni crystals have been melted with Q-switched Nd-YAG laser radiation. The epitaxially regrown surface layers show significant differences between 〈100〉 and 〈111〉 crystals cut from the same boule. The 〈100〉 crystals exhibit a dislocation cell structure with a dislocation density of l011 - 1012 cm-2. The 〈111〉 crystals contain a laterally uniform dislocation network resulting in a much higher dislocation density for the 〈111〉 surface. The elements Ag, Au, Pd, Sn and Ta have been implanted into Ni single crystals at surface concentrations of up to 20 at %. All the as- implanted systems demonstrate solid solubility. We have used these implanted systems to study the alloys formed by laser melting of Ni. In all systems, with the exception of Ag, 100% of the atoms are trapped on lattice sites.
Pulsed Laser Mixing of Ni-Au Surface Films on Nickel Substrates
Authors: Pronko P.P. , Wiedersich H. , Seshan K. , Helling A.L. , Lograsso T.A. , Baldo P.M.
Published: March 2011

The melt phase alloying of Ni-Au films on Ni substrates has been studied for rapid quenches following 35 nano-second Q switched ruby laser pulses (0.69μ wavelength) in the energy regime of 0.5 to 3.0 j/cm2. The Ni and Au films were each 200 Å in thickness having been deposited on a polished Ni substrate by standard hot ribbon vapor deposition methods. Data was obtained on pre and post alloyed surface layers using Rutherford backscattering, transmission electron microscopy, and STEM energy dispersive X-ray analysis. The melting and resolidification dynamics of the liquid-solid interface was monitored through finite difference integration of the non-linear heat conduction equation to give temperature profiles, depth of melting and melt front velocities associated with the liquid-solid phase change. Resolidification velocities were typically 15 meters/second with melt depths extending to a few thousand angstroms depending on pulse energy. RBS data confirms that liquid phase diffusion of gold in nickel has occured. TEM analysis reveals the presence of a two phase mixture being composed of nickel rich and gold rich material. Microbeam energy dispersive X-ray analysis indicates the presence of a relatively uniform mixing of these two Phases. Pronounced one dimensional solute segregation was not observed in these specimens, however, overall penetration depths of the gold was somewhat larger for the lower energy densities than for the larger ones. Also, unusual circular cell patterns were observed in the resolidified material, their contrast being enhanced by preferential etching during the TEM specimen polishing procedure.
Velocity and Orientation Dependence of Solute Trapping In Si
Authors: Baeri P. , Foti G. , Poate J. M. , Campisano S. U. , Rimini E. , Cullis A. G.
Published: March 2011

The segregation phenomena of In, Ga and Bi in Si have been investigated as a function of the liquid-solid interface velocity following laser irradiation. The crystallization velocity has been changed within the range 0.8–5 m/s by varying either the substrate temperature during irradiation or the laser pulse duration. The measured interfacial segregation coefficients depend critically on the velocity and on the crystal orientation of the solidifying plane.
Ultra-Short Pulse Laser Annealing
Authors: Gamo Kenji , Murakami Kouichi , Kawabe Mitsuo , Namba Susumu , Aoyagi Yoshinobu
Published: March 2011

A single picosecond pulse laser annealing of ion-implanted Si is reviewed as ultra-short pulse laser annealing, comparing them with nanosecond pulse and picosecond-pulse train annealing. In order to clarify the physical mechanism of pulsed laser annealing, the dynamic behavior of the amorphous to crystalline transition has been investigated by means of time-dependent optical reflectivity measurement at 0.63 µm (cw) and 1.06 µm (30-ps pulse itself) under the irradiation of the annealing beam of a single 30-ps laser pulse at 1.06 µm. A tentative model is proposed for explaining the results and further problems which remain to be resolved are discussed.
Transmission Electron Microscopy of II-VI/III-V Semiconductor Heteroepitaxial Interfaces
Authors: Li D. , Otsuka N. , Qiu J. , Glenn J. , Kobayashi M. , Gunshor R. L.
Published: March 2011

Interfaces of pseudomorphic (100)ZnSe/GaAs and (100)CdTe/InSb heterostructures grown by molecular beam epitaxy have been studied by transmission electron microscopy. High resolution electron microscope images show dark bands with thicknesses of one or two monolayers at the interfaces. The interfaces appear as bright lines in dark field images of the 200 type reflections, while they become dark lines in dark field images of the 400 type reflections. These observations are explained by assuming the existence of interfaces layers of III2VI3 compounds which have structural vacancies in the sublattices of the group III atoms.
Plasma-Assisted Epitaxial Growth of ZnSe Films In Hydrogen Plasma
Authors: Yamauchi S. , Hariu T.
Published: March 2011

Plasma-assisted epitaxy (PAE) was applied to the growth of ZnSe films on (100) GaAs for low temperature epitaxial growth in hydrogen plasma. High purity ZnSe films were successfully grown by the control of hydrogen gas flow rate and VI/II supply ratio. Hydrogen-chloride gas and nitrogen gas mixed in pure hydrogen gas plasma around 2% respectively resulted in the growth of highly conductive n-type layers (630Scm−1 ) and nitrogen-acceptor doped layers (N-acceptor level∼100meV), however, the control of VI/II supply ratio is also very important for the efficient N-acceptor doping. The plasma optical emission spectroscopy indicated that Se-N is composed by the reaction of -ion with SeH (or Se) in hydrogen and nitrogen mixed gas plasma with Se supply.
Growth and Characterization of CDTE and CDTE Alloys
Authors: Mcdevitt S. , John D.R. , Sepich J.L. , Bowers K.A. , Schetzina J.F. , Rai R.S. , Mahajan S.
Published: March 2011

Methods used to grow bulk, CdTe crystals, effects of alloying on their perfection and typical single crystal properties are reviewed in this paper. Crystals grown by a modified horizontal Bridgman technique have lower dislocation densities than those grown by a modified vertical Bridgman method. Dislocation densities of the order of 1×103/cm2 have been observed in CdTeSe crystals grown by the former technique. Due to the difference in the distribution coefficients of Zn and Se in CdTe, CdTeSe ingots are chemically more uniform than CdZnTe ingots. Purity studies of starting materials indicate that Se substitutions may introduce more impurities than Zn additions.
Growth of ZnSxSe1−x by Mbe Using An Electrochemical Sulphur Source.
Authors: Wallace J.M. , Prior K.A. , Caveneif B.C. , Hunter J.J. , Adams S.J.A. , Haines M.J.L.S.
Published: March 2011

In this paper we describe the use of an electrochemical sulphur cell to grow ZnSxSe1−x alloys on GaAs substrates. The cell uses the ionic transport of Ag ions in Ag2S to produce a sulphur flux which depends on the applied voltage. The advantages and disadvantages of this type of source will be discussed. We also describe the versatility of the cell for fabricating ZnSxSe1−x/ZnSySe1−y multilayers as well as more complex profiles.
Selective Area Deposition of Passivants, Insulators, and Epitaxial Films of II-VI Compound Semiconductors
Authors: Dreifus D.L. , Lansari Y. , Han J.W. , Hwang S. , Cook J.W. , Schetzina J.F.
Published: March 2011

II-VI semiconductor surface passivants, insulators, and epitaxial films have been deposited onto selective surface areas by employing a new masking and lift-off technique. The II-VI layers were grown by either conventional or photoassisted molecular beam epitaxy (MBE). CdTe has been selectively deposited onto HgCdTe epitaxial layers as a surface passivant. Selective-area deposition of ZnS has been used in metal-insulator-semiconductor (MIS) structures. Low resistance ohmic contacts to p-type CdTe:As have also been realized through the use of selectively-placed thin films of the semi-metal HgTe followed by a thermal evaporation of In. Epitaxial layers of HgTe, HgCdTe, and HgTe-CdTe superlattices have also been grown in selective areas on CdZnTe substrates, exhibiting specular morphologies and double-crystal x-ray diffraction rocking curves (DCXD) with full widths at half maximum (FWHMs) as narrow as 140 arcseconds.
Atomic Layer Epitaxy of Wide Bandgap II-VI Compound Semiconductor Superlattices
Authors: Konagai M. , Takemura Y. , Kimura R. , Teraguchi N. , Takahashl K.
Published: March 2011

ZnSe, ZnTe and ZnSe-ZnTe strained-layer superlattices (SLS's) have been successfully grown by atomic layer epitaxy (ALE) using molecular beam epitaxy (MBE-ALE). The ideal ALE growth, i.e., one monolayer per cycle of opening and closing the shutters of the constituent elements, was obtained for ZnSe in the substrate temperature range of 250-350° C. However, for ZnTe, precise control of the Te beam intensity is needed to obtain the ALE growth. Optical properties of the (ZnSe)l-(ZnTe) 1 SLS were evaluated by photoluminesence. ZnSe films were also grown by ALE using metalorganic molecular beam epitaxy (MOMBE-ALE). Diethylzinc (DEZn), diethylsulfur (DES) and diethylselenium (DESe) were used as source gases for Zn, S and Se, respectively. The ALE growth of ZnSe was achieved at substrate temperature between 250 and 300° C which is about 150° C lower than that for the conventional MOMBE.
Excitonic Properties of ZnSe-ZnS Strained-Layer Superlattices and A Fibonacci Sequence
Authors: Taguchi Tsunemasa , Yamada Yoichi
Published: March 2011

Excitonic properties of ZnSe-ZnS strained-layer quantum wells (SLQWs) with type I band lineups are reviewed on the basis of our recent results of temperature- and strain-dependent photoluminescence and absorption spectra. In order to estimate the conduction and valence band offsets as a function of ZnSe well thickness, we have modified the “model-solid” theory in which the valence bands (heavy-hole band in ZnSe and light-hole band in ZnS) are relatively moved with strains. Temperature and high excitation dependent studies of the n=1 heavy-hole excitons suggest a localization of excitons and reveals the important evidence on scatterings of excitons with acoustic and optical phonons. The thermal quenching of the exciton emission is caused by thermal dissociation of quasi-two-dimensional excitons through electrons and holes, from which the activation energy for this dissociation is 4 times larger than Ea.3D (a binding energy of bulk exciton) of ZnSe. A new superlattice structure with a quasiperiodic crystal which is derived from a finite Fibonacci sequence, has been fabricated by a low-pressure MOCVD method and its photoluminescence properties are for the first time introduced.
Photoassisted MBE of II-VI Semiconductor Films and Superlattices
Authors: Giles N.C. , Harper R.L. , Han J.W. , Schetzina J.F.
Published: March 2011

This paper will review recent progress in the growth of II-VI semiconductors at NCSU by photoassisted molecular beam epitaxy, an energy-assisted growth technique in which the substrate is illuminated during the entire growth process. The materials focused on here include undoped and As-doped CdTe, As-doped HgCdTe, and In-doped HgCdTe. These materials were grown as single epilayers, as well as incorporated in other structures including heterojunctions and modulation-doped superlattices. The photo-assist during growth has allowed a substantial reduction in substrate growth temperatures, as well as an enhanced activation of n-type and p-type dopant species. The structural, electrical, and optical properties of the samples will be discussed below.
First and Second Order Raman Studies of Composition and Structural Ordering in Hg1−xCdxTe
Authors: Compaan A. , Bowman R. C.
Published: March 2011

The effects of alloy fluctuations, defect densities, and short-range clustering on the resonance behavior of first and second order LO and TO Raman scattering are studied in Hg1−xCdxTe (MCT). X-values between 0.20 and 0.32 and photon energies from 2.35 to 2.7 eV were used with samples prepared by a wide range of techniques--LPE, MOCVD, MBE, bulk growth, and pulsed laser annealing. We examine the resonance behavior of the HgTe-like TO mode at ∼120 cm−1 and the mode at 133 cm−1, which has been identified as originating from the preferential clustering of 3 Hg and 1 Cd about the Te. We find that the intensity of this peak for various bulk and epitaxially grown samples is unusually large only near the E, resonance. Pulsed laser annealing with a Nd:YAG-pumped dye laser strongly suppresses this mode in all samples suggesting that extremely rapid epitaxial regrowth may inhibit the 3:1 cluster formation. In addition, the resonance-enhanced LO overtones are suppressed by the pulsed laser anneal.
Temperature-Dependent Infrared Absorption of Hg-Based II-VI Semiconductor Superlattices
Authors: Yang Z. , Lansari Y. , Han J. W. , Yu Z. , Schetzina J. F.
Published: March 2011

The optical absorption of a series of HgTe/Cd0.85 Hg0. 15 Te superlattices (SLs) have been measured in the spectral region from 2 to 12 µm at temperatures from 300 K down to 4.2 K. Several subband transitions were identified and their transition energies were compared with theoretical calculations, with the valence band offset δEv between HgTe and CdTe as a fitting parameter. It is found that at a given temperature, a value of δEv = 420 ± 100 meV fits the results of all the SLs, and δEv does not depend on temperature to within ±100 meV.
Properties of Modulation-Doped HgCdTe Superlattices
Authors: Hwang S. , Yang Z. , Lansari Y. , Han J.W. , Cook J.W. , Giles N.C. , Schetzina J.F.
Published: March 2011

Photoassisted molecular beam epitaxy has been employed to successfully prepare p-type and n-type modulation-doped HgCdTe superlattices. The samples were grown at 170°C. In this paper, we report details of the MBE growth experiments and describe the optical and electrical properties that these new multilayered quantum well structures of HgCdTe possess.
Electrical Characterisation of P-Type CdxHg1−xTe Grown by Movpe
Authors: Royle Anne , Gough J S , Irvine S J C , Mullin J B
Published: March 2011

The results of electrical characterisation of a series of MOVPE layers of CdxHg1−xTe (CMT) grown by the interdiffused multilayer process (IMP) are reported. It is shown that the properties of the CMT layers when grown as a “sandwich” between CdTe buffer and cap layers display classical p-type Hall effect curves. These have been modelled and the sensitivity of the fitting parameters are reported. It is shown that there is evidence of complex (“anomalous”) two-layer like behaviour in low x material which is not attributable to inversion behaviour.
Low Temperature Device Processing Technology for II-VI Semiconductors
Authors: Dreifus D.L. , Kolbas R.M. , Sneed B.P. , Schetzina J.F.
Published: March 2011

Low temperature (<60° C) processing technologies that avoid potentially damaging processing steps have been developed for devices fabricated from II-VI semiconductor epitaxial layers grown by photoassisted molecular beam epitaxy (MBE). These low temperature technologies include: 1) photolithography (1 µm geometries), 2) calibrated etchants (rates as low as 30 Å/s), 3) a metallization lift-off process employing a photoresist profiler, 4) an interlevel metal dielectric, and 5) an insulator technology for metal-insulator-semiconductor (MIS) structures. A number of first demonstration devices including field-effect transistors and p-n junctions have been fabricated from II-VI epitaxial layers grown by photoassisted MBE and processed using the technology described here. In this paper, two advanced device structures, processed at <60° C, will be presented: 1) CdTe:As-CdTe:In p-n junction detectors, grown in situ by photoassisted MBE, and 2) HgCdTe-HgTe-CdZnTe quantum-well modulation-doped field-effect transistors (MODFETs).
Free-Carrier Induced Optical Nonlinearities in Narrow Bandgap Semiconductors
Authors: Walrod D. , Auyang S. Y. , Wolff P. A.
Published: March 2011

Free-carrier induced third-order optical nonlinearities can be both large and fast in narrow-gap semiconductors. We have studied a variety of mechanisms in bulk semiconductors and heterostructures using CO2 lasers and found third-order susceptibilities as large as 2×10−3 esu with picosecond relaxation times. These mechanisms saturate at much higher intensities than do slower mechanisms and hence induce huge modulations of the dielectric function. In addition, most of these processes are nonresonant so they do not require the exact matching of material parameters and are relatively insensitive to temperature.