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In this paper, for the first time, we report high quality CVD hafnium oxynitride (HfOxNy) MOSFETs with conventional self-aligned poly-Si gate. These CVD HfOxNy films deposited using TDEAH (Tetrakisdiethylamino hafnium, C/sub 16/H/sub 40/N/sub 4/Hf) and NH/sub 3/ remain amorphous after 900/spl sim/950/spl deg/C annealing. Compared to HfO/sub 2/, HfOxNy exhibits reduced leakage current by 2/spl sim/3 orders of magnitude, excellent boron penetration immunity, superior thermal stability of both EOT and leakage current after high temperature annealing, and excellent reliability.

A systematic study of long-term reliability of ultra thin CVD HfO/sub 2/ gate stack (EOT=10.5 /spl Aring/) with TaN gate electrode is presented. The polarity and area dependence and temperature acceleration of time-to-breakdown (TBO), defect generation rate, and critical defect density are studied. It is found that T/sub BD/ is polarity-independent (T/sub BD,-Vg/=T/sub BD,+Vg/). TDDB lifetime acceleration shows that 10-year lifetime of HfO/sub 2/ gate stack is projected at Vg=1.63 V for EOT=8.6 /spl Aring/ and Vg=1.88 V for EOT=10.6 /spl Aring/ at 25/spl deg/C. However, after temperature acceleration of 150/spl deg/C, area scaling to 0.1 cm/sup 2/, and the projection to low percentage failure rate of 0.01%, the maximum operating voltages are projected to be Vg=0.6 V for EOT 8.6 /spl Aring/ and Vg=0.75 V for EOT=10.6 /spl Aring/.

This is the second phase of the pK(a) predictor published earlier (J. Chem. Inf. Comput. Sci. 2002, 42, 796-805). The algorithm has been extended by treating specific chemical classes separately and generating tree-structured molecular descriptors tailored to each individual class. A training set consisting of 625 acids and 412 bases covers the major areas of chemical space involved in protonation and deprotonation. The models obtained demonstrate excellent statistics (SE = 0.41 for acids and 0.30 for bases) and yielded accurate predictions on an external test set. The quality and statistical performance of pK(a) prediction has been improved considerably over the initial implementation of the method.

Pharmacophore triplets and quartets have been used by many groups in recent years, primarily as a tool for molecular diversity analysis. In most cases, slow processing speeds and the very large size of the bitsets generated have forced researchers to compromise in terms of how such multiplets were stored, manipulated, and compared, e.g., by using simple unions to represent multiplets for sets of molecules. Here we report using bitmaps in place of bitsets to reduce storage demands and to improve processing speed. Here, a bitset is taken to mean a fully enumerated string of zeros and ones, from which a compressed bitmap is obtained by replacing uniform blocks ("runs") of digits in the bitset with a pair of values identifying the content and length of the block (run-length encoding compression). High-resolution multiplets involving four features are enabled by using 64 bit executables to create and manipulate bitmaps, which "connect" to the 32 bit executables used for database access and feature identification via an extensible mark-up language (XML) data stream. The encoding system used supports simple pairs, triplets, and quartets; multiplets in which a privileged substructure is used as an anchor point; and augmented multiplets in which an additional vertex is added to represent a contingent feature such as a hydrogen bond extension point linked to a complementary feature (e.g., a donor or an acceptor atom) in a base pair or triplet. It can readily be extended to larger, more complex multiplets as well. Database searching is one particular potential application for this technology. Consensus bitmaps built up from active ligands identified in preliminary screening can be used to generate hypothesis bitmaps, a process which includes allowance for differential weighting to allow greater emphasis to be placed on bits arising from multiplets expected to be particularly discriminating. Such hypothesis bitmaps are shown to be useful queries for database searching, successfully retrieving active compounds across a range of structural classes from a corporate database. The current implementation allows multiconformer bitmaps to be obtained from pregenerated conformations or by random perturbation on-the-fly. The latter application involves random sampling of the full range of conformations not precluded by steric clashes, which limits the usefulness of classical fingerprint similarity measures. A new measure of similarity, The Stochastic Cosine, is introduced here to address this need. This new similarity measure uses the average number of bits common to independently drawn conformer sets to normalize the cosine coefficient. Its use frees the user from having to ensure strict comparability of starting conformations and having to use fixed torsional increments, thereby allowing fully flexible characterization of pharmacophoric patterns.

A great deal of effort is currently going into the design of combinatorial libraries. Published approaches are generally "optimal" in that each best satisfies the target objective function it employs. Relative efficiencies can be compared in such cases, but it is often difficult to compare libraries generated by different methods or even by different parameterizations of the same method. This is particularly true once it is appreciated that attributes other than molecular diversity are important. This paper will discuss several ways in which library designs can be meaningfully compared to one another, visually as well as numerically. O planejamento de coleções combinatórias de compostos constitui, atualmente, um dos principais paradigmas da química medicinal. Muitos dos procedimentos publicados na literatura são "ótimos" por satisfazerem certos objetivos previamente definidos. Suas eficiências podem ser comparadas, mas em geral, torna-se muito difícil a comparação com coleções geradas por métodos diferentes ou mesmo por métodos que utilizem parametrizações diferentes. Isto é particularmente verdadeiro quando parâmetros outros que não os de diversidade molecular são importantes. Este artigo discute várias maneiras de comparar coleções de compostos, visual e numericamente.

Several different functions have been put forward for evaluating the energetics of ligand binding to proteins. Those employed in the DOCK, GOLD and FlexX docking programs have been especially widely used, particularly in connection with virtual high-throughput screening (vHTS) projects. Until recently, such evaluation functions were usually considered only in conjunction with the docking programs that relied on them. In such studies, the evaluation function in question actually fills two distinct roles: it serves as the objective function being optimized (fitness function), but is also the scoring function used to compare the candidate docking configurations generated by the program. We have used descriptions available in the open literature to create free-standing scoring functions based on those used in DOCK and GOLD, and have implemented the more recently formulated PMF [J. Med. Chem. 42 (1999) 791] scoring function as well. The performance of these functions was examined individually for each of several data sets for which both crystal structures and affinities are available, as was the performance of the FlexX scoring function. Various ways of combining individual scores into a consensus score (CScore) were also considered. The individual and consensus scores were also used to try to pick out configurations most similar to those found in crystal structures from among a set of candidate configurations produced by FlexX docking runs. We find that the reliability and interpretability of results can be improved by combining results from all four functions into a CScore.

In this study, the authors examined the effects of different annealing schemes on crystallinity in atomic layer deposition (ALD) grown Ti-containing metal gates and ultrathin ALD HfO2 high-k dielectric layers, and corresponding electrical results in metal oxide semiconductor capacitor (MOSCAP) devices. The authors investigated the effect of a postmetal deposition anneal (PMA) on the underlying HfO2, which was deposited using either a standard ALD process or a process which utilized a cyclical deposition and annealing scheme (termed DADA). The effect of the starting substrate surface, either chemically grown SiO2 or H-terminated Si, on HfO2 crystallinity was also studied. For 40 cycle ALD HfO2 (∼32 A) with a TiN overlayer, a transition from an amorphous state to a cubic phase was observed with the application of a PMA treatment. Evidence of the orthorhombic phase of HfO2 with some level of texturing was observed for 40 cycle DADA processed films annealed with a TiN cap. Concomitantly a cubic (111) texture was observed for TiN deposited on DADA processed HfO2 and subjected to a PMA. Suppression of crystallinity for HfO2 deposited on H-terminated Si and annealed with a TiN layer was observed which illustrates the need for an adequate nucleation layer for uniform grain growth and increased atomic ordering. The authors also investigated metal gate stacks with a bilayer of TiN overlying Ti which showed reflections from both cubic TiN and hexagonal TiN0.3 in the as-deposited state and after annealing clear evidence of silicidation (TiSix) was observed. In MOSCAP structures with 40 cycle ALD HfO2 and a TiN overlayer subjected to a PMA, although the cubic phase of HfO2 was stabilized, there was no associated improvement in device scaling. This study highlights the importance of the initial crystalline state and nucleation of HfO2 as well as the thermal stability of the capping metal layer material when engineering dielectric layer crystallinity by means of a postmetal cap anneal. For ultrathin HfO2 integrated in advanced metal oxide semiconductor structures, the benefits of the stabilization of a higher-k phase through postmetal gate anneal may not be fully realized due to increased leakage along grain boundaries or decrease in effective k due to changes in the lower-k interfacial layer.

As Si Metal Oxide Semiconducting Field Effect Transistors (MOSFETs) have continued to scale Short Channel Effects (SCE) have become exacerbated by the inability to continue scaling the Equivalent Oxide Thickness (EOT) of the device significantly beyond what was realized with the introduction of High K Metal Gate (HKMG) MOSFETs at the 45nm technology node. Since EOT scaling has not kept pace with the gate length (Lg) scaling needed to continually increase the transistor drive current, device makers have instead elected to introduce FinFET and Tri-Gate transistors with inherently better electrostatic control in order to realize reasonable SCE in the device. High mobility channel materials, such as Ge, are attracting increasing interest due to the possibility of realizing increased performance even without scaling the Lg of the device (1). Ge is particularly attractive for use as a channel material for P-type MOSFETs (PMOSFETs) due to its high hole mobility and Si processing compatibility. In fact, we have demonstrated experimental PMOSFET devices with hole mobilities significantly higher than what can be obtained on Si, Fig. 1. However, a significant remaining challenge to incorporating Ge into VLSI production is obtaining a stable and well-passivated dielectric/semiconductor interface using tooling and substrates compatible with current 300mm Si VLSI High Volume Manufacturing (HVM) in order to achieve reasonable device performance at sub 1nm EOTs (2). In this paper we will report progress on surface passivation and functionalization of Ge channel surfaces, as well as High K dielectric layer growth by Atomic Layer Deposition (ALD) and the resulting electrical properties measured by fabricated MOSFETs and Metal Oxide Semiconducting Capacitors (MOSCAPs). The Ge channel devices were formed on 300 mm Si wafers using Ge grown by an epitaxial process including a graded SiGe buffer layer. We have utilized a TEL CertasTMChemical Oxide Removal (COR) process (3), which uses dry HF and ammonia, rather than traditional wet cleaning, to remove Ge native oxides without damaging or roughening the fragile Ge surface. We have also studied Ge oxide interface layer formation by plasma oxidation using a Slot Plane Array (SPA) antenna (4) utilizing in-line X-ray Photoelectron Spectroscopy (XPS) to measure Ge and high K oxide thickness on monitor wafers fashioned by the same Ge epitaxial process used to make the electrical devices and compared it to the equivalent Si oxidation process, Fig. 2. Various other passivation and interface schemes were investigated and will be discussed, contrasted and compared including ozone oxidation, Al oxide passivation/interface layers, SPA plasma nitridation, and thin amorphous Si passivation layers. We have utilized Hf oxide grown by a previously reported ALD process (5) as the High K dielectric for our devices, and TiN as the metal gate. Our results show that Ge channel devices can be fabricated on 300mm Si substrates using Si VLSI-compatible toolsets and infrastructure and resulting in reasonable device characteristics, Fig. 3. Thus, Ge channel MOSFETs are found to be a promising technology for use in HVM at future VLSI technology nodes. References 1. S. Swaminathan, Y. Oshima, M. Kelly, P.C. McIntyre, Appl. Phys. Lett., 95, 032907 (2009). 2. L. Zhang, M. Gunji, S. Thombare, P.C. McIntyre, IEEE Electr. Device. L., 34, 736 (2013). 3. T. Hamelin, J. Wallace, and A. LaFlamme, U.S. Patent No. 7029536. 4. T. Sugawara, S. Matsuyama, M. Sasaki, T. Nakanishi, S. Murakawa, J. Katsuki, S. Ozaki, Y. Tada, T. Ohta, N. Yamamoto, Jpn. J. Appl. Phys., 44, 1232 (2005). 5. R.D. Clark, S. Consiglio, C. Wajda, G. Leusink, T. Sugawara, H. Nakabayashi, H. Jagannathan, L.F. Edge, P. Jamison, V. Paruchuri, R. Iijima, M. Takayanagi, B. Linder, J. Bruley, M. Copel, V. Narayanan, ECS Trans. 16, 4, 291 (2008)

A descriptor is a mathematical function which maps chemical structures into the set of real numbers or into a real-valued vector. When functions take on single values which characterize a molecule as a whole, they can be classed as one dimensional descriptors, as can substituent parameters used to partition physical chemical effects among the substructures of which the molecules being studied are comprised. Partition coefficients (e.g., logP and ClogP) and molar refractivity (MR) are examples of ID descriptors. 2D descriptors such as atom pair and substructural fingerprints and connectivity indices explicitly incorporate contributions from molecular connectivity. 3D descriptors, in contrast, include contributions from effects (e.g., through-space interactions) which are dependent on the conformation or the position of a molecule, or both. The most commonly employed 3D descriptors are molecular fields (CoMFA).1

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The reliability of atomic layer deposited Hf1-xZrxO2 with x=0.8 on a SiON interfacial layer (IL) has been analyzed in detail for three different oxide deposition processes, (i) DADA: samples were subjected to dielectric deposition and thermal annealing in a cyclical process; (ii) DSDS: samples were subjected to similar cyclical process with dielectric deposition and exposure to Ar plasma; and (iii) As-Dep: the dielectric for the control samples was deposited without any intermediate step. Capacitance-voltage and current-voltage characteristics of the MOS capacitors (MOSCAP) with metal gate (TiN), subjected to a constant field stress of 2.75 × 107 V/cm in the gate injection mode, show that the flat-band voltage shift (∆VFB ) and stress induced leakage current (SILC) below 100 s stress is the lowest for DSDS samples whereas the worst degradation was observed for DADA samples. However, identical degradation was observed in all sample types when stress was increased to 1000 s. Intermediate plasma exposure (DSDS process) seems to supress the oxide trap formation as it provides EOT downscaling ability and good reliability performance. The reliability characteristics, when compared with pure HfO2, seem to improve with the addition of ZrO2.

A multi-technique approach was used to determine the crystalline phase, texture, and electronic structure of Hf1−xZrxO2 (x = 0–1) high-k gate dielectric thin films grown by atomic layer deposition using a cyclical deposition and annealing method. X-ray diffraction (XRD) analysis performed in both grazing incidence and pole figure configurations identified the tetragonal phase for Zr/(Zr + Hf)% = 58% and a concomitant increase in tetragonal phase for further increase in Zr content. X-ray absorption spectroscopy (XAS) was used to determine the local atomic structure and metal oxide bond orientation. Polarization dependent XAS in normal and grazing incidence showed preferential metal-oxygen bond orientation consistent with the texturing observed by XRD. X-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry (SE) were also performed with special focus on spectral features which arise as a consequence of atomic ordering and specific crystalline phase. The combination of XAS, XPS, SE, and XRD enabled the determination of the effects of the deposition scheme and compositional alloying on the electronic structure, crystal field effects, optical properties, crystal phase, and texture for the mixed oxide alloy series. The multi-technique approach revealed the martensitic-like transformation of crystalline phase from monoclinic to tetragonal as the majority metal oxide concentration in the alloy mixture changed from HfO2 to ZrO2.

In order to enhance the dielectric properties of HfO2, the alloying of HfO2 with ZrO2 was studied. HfxZr1-xO2 films with different Hf:Zr ratios were deposited by atomic layer deposition (ALD) combined with a cyclical deposition and annealing scheme (termed DADA) in which an annealing was performed after every 20 ALD cycles. The impact of the ZrO2 addition on the structural properties of the ALD grown films was investigated by grazing incidence in-plane X-ray diffraction and pole figure measurement using synchrotron radiation as well as transmission electron microscopy and X-ray photoelectron spectroscopy. The HfxZr1-xO2 films with x=1 show the presence of monoclinic (-111) fiber texture. As the Zr content increases, stabilization of the tetragonal phase is observed. The pole figure measurements indicate the presence of tetragonal (111) fiber texture for the ALD HfxZr1-xO2 films with higher Zr content grown by DADA in contrast to random orientation in post deposition annealed films.

For the purpose of extending the upper temperature limit of metallorganic atomic layer deposition, mixed ligand precursors containing cyclopentadienyl (Cp, C5H5) ligands have been shown to exhibitsuperior thermal stability compared to the widely adopted tetrakis(ethylmethylamino)hafnium (TEMAH) precursor while also possessing adequate vapor pressure characteristics for use in atomic layer deposition (ALD) processing. In order to prevent the deleterious oxidation of the underlying Si from O3 the use of a milder oxidant such as H2O is preferred. Accordingly in this study, we investigated ALD using the liquid precursors CpHf(NMe2)3 and (CpMe)2Hf(OMe)Me in the temperature range 305 – 410 °C with H2O as a co-reactant and compared the film growth and electrical properties with films deposited using a conventional TEMAH/H2O process at 305 °C as well as the same process with an optimized annealing scheme. The CpHf(NMe2)3/H2O process was observed toexhibit a growth-per-cycle (GPC) in the range 0.23 – 0.36 A/cycle ...

We have recently reported electrical performance improvements in atomic layer deposited (ALD) HfO2 films grown by use of a cyclical deposition and annealing scheme (termed DADA) compared to a single deposition followed by a post-deposition anneal (PDA). We previously proposed a model for bottom-up crystallization in DADA films in contrast to random crystallization for PDA films. To elucidate the mechanisms for this structural modification, in this study we utilized grazing incidence in-plane X-ray diffraction and pole figure measurements using synchrotron radiation as well as transmission electron microscopy. Structural differences were investigated from different annealing conditions as well as from different thickness of films. We observed significant differences in structural properties of DADA films compared to films receiving PDA. We also report on the evolution of monoclinic HfO2 with a (-111) preferred orientation (fiber texture) for DADA films whereas PDA treatment resulted in a random grain alignment and mixed phase structure.

We present both EOT scaling and flatband voltage (Vfb) shift for Hf-based high-k containing metal-oxide-semiconductor capacitors (MOSCAPs) due to Al addition into the TiN metal gate. The metal gate was deposited using chemical vapor deposition (CVD) and the Hf-based high-k films were deposited using CVD or atomic layer deposition (ALD) in 300nm deposition chambers. We found that the Vfb shift amount by Al addition into TiN depends on the high-k film (HfO2 vs. HfSiON) as the shift for the HfO2 containing stack was greater than that in the HfSiON containing stack. We also examined the effect of the thermal budget of the MOSCAP flow on the Vfb shift by Al addition into TiN. We observed that the Vfb shift direction by Al addition into TiN was dependant on the MOSCAP flow (gate-first vs. gate-last like) and this Vfb shift behavior can be explained by Al-based dipole and oxygen vacancy models.

With the replacement of SiO2 by high-k Hf-based dielectrics in complementary metal–oxide–semiconductor technology, the measurement of the high-k oxide bandgap is a high priority. Spectroscopic ellipsometry (SE) is one of the methods to measure the bandgap, but it is prone to ambiguity because there are several methods that can be used to extract a bandgap value. This paper describes seven methods of determining the bandgap of HfO2 using SE. Five of these methods are based on direct data inversion (point-by-point fitting) combined with a linear extrapolation, while two of the methods involve a dispersion model-based bandgap extraction. The authors performed all of these methods on a single set of data from a 40 A HfO2 film, as well as on data from 20 and 30 A HfO2 films. It was observed that the bandgap values for the 40 A film vary by 0.69 eV. In comparing these methods, the reasons for this variation are discussed. The authors also observed that, for each of these methods, there was a trend of increasing...

In this work we present physical and electrical characterization of HfO2 films deposited using the Dep-Anneal-Dep-Anneal (DADA) deposition scheme. Electrical results from MOSCAP devices fabricated using a low temperature (Gate Last-like) integration flow are presented. In addition we report detailed physical analyses of the films and changes in the films versus as-deposited ALD HfO2 and films undergoing a single post-deposition anneal and show the correlation between observed physical changes in the film and electrical results. Observed physical changes using HR-RBS, HR-TEM, SIMS, XPS and XRR include crystallization, densification, Si intermixing, reduction of in-film carbon and improved etch resistance leading to improved leakage vs. EOT and electrical non-uniformity. Dependence of these changes on the underlying interface layer (e.g. SiO2 vs SiON) is also described.

Recent studies have shown that La2O3 films can be used to adjust the threshold voltage (Vt) of NMOS Hf-based high-k/metal gate devices to desirable values, and a dipole at the high-k/SiO2 interface has been proposed to explain the Vt shifts. In order to investigate the mechanism of the Vt shift further, we have measured the flatband voltage (Vfb) and Si band bending of technologically relevant TiN/HfO2/La2O3/SiO2/p-Si stacks where the thickness and position of the La2O3 layer have been systematically varied. We observed systematic changes in Vfb, Si band bending and the HfO2-Si valence band offset as a function of La2O3 layer thickness and position. These changes can be explained by a band alignment model that includes a dipole at the high-k/SiO2 interface, thus supporting the work of previous authors. In addition, we have derived the theoretical relationship between Vfb and Si band bending, which agrees well with our experimental measurements.

This paper presents the optimization of HfO2 high-κ gate dielectrics by utilizing cyclic depositions and anneals during atomic layer deposition (ALD). An order of magnitude reduction in gate leakage is obtained by tuning the anneal temperature, duration and sequence in the ALD. The films are also seen to have three to four times reduction in carbon content. These optimized films are moreover observed to be densified without compromising equivalent oxide thickness (EOT), carrier mobility and threshold voltage. Further electrical characterization supports that there is a suppression of trap assisted tunneling with the optimized ALD process by revealing a stronger temperature dependence on the annealed samples as opposed to the conventional ALD process.

The HfO2–Si valence and conduction band offsets (VBO and CBO, respectively) of technologically relevant HfO2/SiO2/Si film stacks have been measured by several methods, with several groups reporting values within a range of ∼1 eV for both quantities. In this study we have used a combination of x-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry to measure the HfO2–Si VBO and CBO of both as-deposited and annealed stacks. Unlike previous XPS based measurements of the HfO2–Si VBO, we have corrected for the effect of charging in the XPS measurement. We find that after correction for charging, the HfO2–Si VBOs are decreased from their typical XPS-measured values, and agree better with values measured by UV photoemission spectroscopy and internal photoemission. We also report values for the rarely reported HfO2–SiO2 and SiO2–Si VBOs and CBOs in HfO2/SiO2/Si stacks. In addition to the band offsets, XPS was used to measure the band bending in the Si substrate of HfO2/SiO2/Si film stacks. Unannealed HfO2 stacks showed downward Si band bending of 0.4–0.5 eV, while annealed HfO2 stacks showed negligible band bending. Finally, we investigated the composition of the SiO2 layer in SiO2/Si and HfO2/SiO2/Si. By decomposing the Si 2p spectra into the spin orbit partner lines of its five oxidation states we observed that the growth of the HfO2 films resulted in the growth of the SiO2 underlayer and an increase by a factor of ∼2.3 in the density of suboxide species of SiO2. Based on the relatively high binding energy of the Si 2p4+ level with respect to the Si 2p0 level and a survey of results from literature, we conclude that the SiO2 layer in the HfO2/SiO2/Si samples we measured does not undergo significant intermixing with HfO2.

The reaction of 2 equiv of LiC5Me4R (R = H, iPr, nBu) with PbCl2 affords the Pb(C5Me4R)2 metallocenes in good yields. Pb(C5Me4iPr)2 and Pb(C5Me4nBu)2 were isolated as red oils, while Pb(C5Me4H)2 wa...

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This work presents a detailed investigation of the deposition of ZrO2 using a metallorganic precursor in a 300 mm wafer processing ALD system. The ZrO2 films in this study were characterized by inline spectroscopic ellipsometry and corona-oxide-semiconductor measurements, and offline Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). A growth temperature window between 215 {degree sign}C and 340 {degree sign}C was investigated and the thermal CVD rate was observed to increase above 265 {degree sign}C, thus representing an upper temperature boundary for ALD-dominated growth. For a saturated process at 265 {degree sign}C, a within-wafer non-uniformity of < 2 % for films deposited using 8 cycles or greater was obtained. An in-situ capping with TiN followed by an in-situ post-deposition rapid thermal anneal was also performed in order to assess the thermal stability of the deposited gate stack. For rapid thermal annealed films ({greater than or equal to} 900 {degree sign}C) with a TiN cap, no significant thermally-induced chemical changes were observed while a peak in the XRD spectra attributable to tetragonal and/or cubic phase ZrO2 was observed. Excellent film conformality and coverage over a FinFET structure was observed by TEM.

Shortly after Phil Magee died of cancer in June 2005, Marvin Charton approached me at the end of an AGRO Division QSAR Symposium and asked me if I would be willing to help him organize a memorial Symposium in Phil’s honor. I was happy to do so, and was pleased to be joined in the effort by John Block the next June. Lowell Hall and Lemont Kier offered to pitch in later that year. Sponsoring organizations eventually included the AGRO, COMP and CINF Divisions of the American Chemical Society and the Cheminformatics and QSAR Society. Corporate sponsorship was provided by this Journal, Tripos International, Chemical Computing Group, eduSoft, ChemSilico, BioSAR Research, Hall Associates Consulting and Magee Real Estate. Their generous contributions were used to offset the travel expenses of several Symposium speakers who would not have been able participate otherwise. The response to our calls for Symposium papers was nearly overwhelming. Over 40 abstracts for oral presentations were submitted, with several of Phil’s friends and colleagues writing to express their regret at not being able to attend the meeting. The memorial symposium, formally titled ‘‘QSAR Reborn: A Symposium in Memory of Dr. Phillip Magee’’, consisted of six well-attended sessions spread across all five days (19–23 August 2007) of the 234th National ACS Meeting in Boston MA. The idea of putting together the Memorial issue of the Journal of Computer-Aided Molecular Design that you now hold in your hands—physically or virtually—grew in parallel to the organization of the Symposium. Symposium participants were invited to contribute, of course, but the topics were not restricted to what had been presented at the meeting. The call for papers solicited manuscripts for the Journal from the entire community, including those who were unable to attend or to speak at the Boston meeting. Just as for the Symposium, the response for Journal contributions was more than could reasonably have been hoped for. I trust that you will find the 15 papers collected here a fitting tribute to Phil’s memory. The authors hail from across the continent and around the world, representing ten states and provinces and nine different countries. They are drawn from industrial as well as academic research organizations. The collection begins with Marvin Charton’s brief biography of the man and his place in QSAR and its history. About half of the technical papers deal with 2D descriptors and about half involve 3D (or higher) levels of description, with some comparing—or even integrating— the two levels. Topics range from the practical (e.g., predicting solubility or developing a better insecticide) to the esoteric (e.g., scaling descriptors by molecular size to decorrelate them or choosing between ligandand receptorbased alignment methods). Most deal with QSAR at the level of the intact organism, just as Phil himself often did. The organisms considered range in size from viruses to guppies to humans. Although in vitro assays of one kind or another underlie some of the analyses, most concern physical, metabolic or toxicological properties. They include two studies on dermal sensitivity, one of which makes use of a data set compiled by Phil himself. In summary: the papers collected here embrace nearly as broad a chunk of the QSAR world as Phil Magee did himself. I think he would approve, and hope that you will as well.

In this work, we present a study of the growth and electrical characteristics of metalorganic atomic layer deposited (MO-ALD) HfO2 films deposited using a 300 mm Counter-Flow ALD platform. HfO2 films were deposited over a large range of process temperatures, and flow rates in order to fully characterize the MOALD process window. The HfO2 films were characterized using AFM, HRTEM, MEIS, and SIMS. Saturation curves were generated for precursor and ozone oxidant over a 150 ºC process temperature window, using two different flow rates of Hf precursor. The use of water versus ozone as an oxidant was also investigated. Since all depositions take place above the decomposition temperature of the precursor, it is critical to understand and control the rate of thermal decomposition or parasitic CVD in the process in order to realize good uniformity in a traveling wave-type system. Thus, we have measured the rate of thermal CVD over the full range of temperatures. The thermal CVD rate shows a concave Arrhenius behavior as the process rises in temperature and transitions from an ALD dominated growth mechanism to a CVD dominated mechanism. We propose a possible explanation for this behavior. In addition to the growth characteristics, we have investigated the electrical properties of the as-deposited films using in-line Quantox measurements, and gate stack structures using integrated devices. The relationship between process and electrical characteristics will be discussed.

This article reviews the many adaptations and applications of microcomputer technology for handicapped children. The review expands Peelle's (1983) computer metaphors to include: computer as sensor...

The two heme equivalents of cytochrome b -563 in the photosynthetic cytochrome b — f complex can be distinguished by their rate of reduction with dithionite at 25°C and by their optical absorption spectra at 77 K. The cytochrome b component that is rapidly reduced after addition of dithionite or reduced ferredoxin possesses an α band that splits at 77 K into two peaks, at 557 and 561 nm. Prolonged incubation with reductant reveals a second, approximately equimolar cytochrome b component that has at 77 K an unsplit α-band maximum at 561 nm. The designations cytochrome b -563 H and cytochrome b -563 L , respectively, are proposed for the rapidly and more slowly reduced cytochrome b -563 components. Potentiometric titration establishes a midpoint potential, E m , of -30 mV (electron change n ≈ 2) for cytochrome b -563 H and -150 mV ( n = 1) for cytochrome b -563 L at pH 7.5. The reduction potential of these components is raised by 2-heptyl-4-hydroxyquinoline N -oxide, giving E m values of +57 and -34 mV, respectively, with each titration slope approximating n = 2.

A class of cell envelope vesicles (M vesicles) prepared from Halobacterium halobium Rl contain a light-driven sodium pump that serves to eject sodium ions and to create an electrical potential difference in direct proportion to the intensity of illumination. The M vesicles take up protons as an immediate consequence of this electrical potential difference. Predictably, the sodium efflux rate and extent are not inhibited by proton ionophores, whereas the proton uptake is enhanced. In the presence of valinomycin and K+, the electrical potential difference and the proton uptake are abolished, but the light-driven sodium extrusion is only slightly decreased. M vesicles are essentially free (>95%) from contamination by a light-driven proton pump. The participation of a reversed bacteriorhodopsin pump is unlikely since absolutely no internally positive electrical potential difference is detectable. The ejection of sodium by M vesicles is independent of protonmotive force and the rate of the Na+ efflux does not show a gating effect in response to membrane potential. In sharp contrast, another class of cell envelope vesicles (L vesicles) accomplish sodium extrusion via an electrogenic H’/Na’ antiporter that is driven by protonmotive force and activated by membrane potential (Lanyi, J. K., and MacDonald, R. E. (1976) Biochemistry, 15, 4608-4614). We conclude that at least two mechanisms exist in H. halobium to create electrical and chemical potential energy by the transduction of light energy: the bacteriorhodopsin proton pump and a light-driven sodium pump. The consequences of this second pump to the circulation of ions and to Na’/ amino acid symport are considerable and cannot be neglected.

Urban and rural school psychologists in Virginia were surveyed on role diversity, role emphasis, continuing education, and job satisfaction. As predicted, rural school psychologists have a more diverse role, spend less time in traditional assessment activities, and are more likely to engage in activities involving them at the systems and community levels. School psychologists indicated their perceptions of differences in rural and urban school psychology. Implications of urban vs. rural practice for school psychology training programs are discussed.

(1965). The Organization of an Honors College. The Journal of Higher Education: Vol. 36, No. 6, pp. 313-321.