bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion of Hydrogen and Deuterium in Stack Systems of SixNyHz/SixNyDz and Crystalline Si
Authors: Boehme Christoph , Lucovsky Gerald
Published: April 2011

H/D-, N-H/D- and Si-H/D-bond density changes were investigated in stacks consisting of a Cz-Si substrate, a thin layer of SiO2, amorphous deuterated silicon nitride as well as amorphous hydrogenated silicon nitride in order to see if the post deposition anneal of a-SixNyHz layers on crystalline silicon wafers can actually lead to a migration of H atoms into the Si-bulk, which is an important question in regard to emitter passivation of Si-solar cells.

The stacks were grown with remote plasma enhanced chemical vapor deposition (RPECVD). A low temperature (≈200°C) process of down stream injected ammonia (NH3) and silane (SiH4) activated by an upstream injected He-plasma, produced through RF-radiation (13.65MHz) was used. Thermal treatment was executed by ex situ rapid thermal anneal in Ar ambient. For the measurements of H and D bond densities, FTIR was employed while SIMS determined atomic densities of H, D and O in the c-Si/nitride interface region. The experiments showed that H transport in silicon nitride is determined by several mechanisms including diffusion and dissociation processes and that silicon nitride deposited with high ammonia to silane ratios can produce molecular species like ammonia and H2. The study of the reaction dynamics showed that the production of molecular hydrogen is the most dominant process as long as Si-H-bonds are present in the system. After their exhaustion, an ammonia producing reaction prevails that leads with increasing temperatures to lower densities in the nitride films.
A physically-based SPICE model for the leakage current in a-Si:H TFTs accounting for its dependencies on process, geometrical, and bias conditions
Authors: Servati Peyman , Nathan Arokia , Sazonov Andrei
Published: April 2011

We have developed a physically-based analytical model of the static current-voltage characteristics of hydrogenated amorphous silicon (a-Si:H) inverted staggered thin film transistors (TFTs) in the reverse (leakage) regime (VG<0,VD>0). We studied analytically (based on measurement data) the dependence of the leakage current on process parameters (i.e. the deposition-temperature-dependent phosphorus diffusion profile in the a-Si:H active layer), geometrical parameters (i.e. a-Si:H thickness, source/drain overlap areas), and operating conditions (i.e. VG, VD). The derived analytical model is implemented in HSPICE. The simulated and measured results are in good agreement with a discrepancy of less than 5%.
A Study of the Time Scales of Processes Responsible for the Light-induced Degradation of a-Si:H by Pulse Illumination
Authors: Stradins Paul , Kondo Michio , Matsuda Akihisa
Published: April 2011

Degradation properties of a-Si:H and a-Si:D by pairs of intense light pulse pairs are examined. By varying the delay time between pulses in a pair while keeping the total illumination time and dose constant, the time scales involved in the light-induced defect creation are investigated. In nanosecond pulse case, we find a sharp drop in degradation efficiency with delay time, followed by further gradual decrease at much longer times. For microsecond pulses, the degradation efficiency varies with the delay time in microseconds. The recombination proceeds bimolecularly and is largely completed during the pulse. It is suggested that the first stage of degradation is related to bimolecular recombination that takes place during the pulse. The second stage is possibly related to longer-living metastable species.
A Critical Test of Defect Creation Models in Hydrogenated Amorphous Silicon Alloys
Authors: Palinginis Kimon C. , Yang Jeffrey C. , Guha S. , Cohen J. David
Published: April 2011

Using the modulated photocurrent method we studied the deep defect creation and annealing kinetics of amorphous silicon-germanium alloys with Ge fractions below 10at.%. The modulated photocurrent spectroscopy clearly discloses the existence of two distinct bands of majority carrier traps in these alloys. The bands were identified as neutral Si dangling bonds and neutral Ge dangling bonds. Our studies show clearly that the Si and Ge defects directly compete with each other during annealing, implying a global reconfiguration mechanism. The creation kinetics reveal the usual t1/3 illumination time dependence for the total deep defect density. However, the individual densities of Si and Ge defects have different time dependencies. The details of the creation and annealing kinetics of Ge and Si defects are used to test predictions of certain defect creation models.
Mechanisms for Metastability in Hydrogenated Amorphous Silicon
Authors: Biswas R. , Li Y.-P. , Pan B.C.
Published: April 2011

We propose metastabilities in amorphous silicon fall into two classes. One class is the local changes of structure affecting a macroscopic fraction of sites. The other class is the metastable generation of dangling bonds with mid-gap states. The local metastability is explained by a new metastable state formed when H is flipped to the backside of the Si-H bond at monohydride sites. The dipole moment of this H-flip defect is larger and increases the infrared absorption. This H-flip defect accounts for large structural changes observed on light soaking including larger absorption and volume dilation. We propose a new model for the generation of metastable dangling bonds. The new ‘silicon network rebonding model’ involves breaking of weak silicon bonds and formation of isolated dangling bonds, through rebonding of the silicon network. Hydrogen motion is not involved in metastable defect formation. Defect formation proceeds by breaking weak silicon bonds and formation of dangling bond-floating bond pairs. The floating bonds migrate through the network and annihilate, producing isolated dangling bonds. This new model provides a new platform for understanding the atomistic origins of lightinduced degradation.
Modeling the Optical Quantum Efficiency of Thin Film Amorphous Silicon Solar Cells
Authors: Rowlands Sally-anne F. , Livingstone John , Lund Christopher P.
Published: April 2011

The optical quantum efficiency and spectral response of p-i-n thin film amorphous silicon (a-Si:H) solar cells have been modeled using software based on optical admittance analysis. The optical constants of a-Si:H and Indium Tin Oxide (ITO) thin film layers have been measured by Variable Angle Spectroscopic Ellipsometry (VASE) and used as inputs into the optical admittance analysis program in order to model cells constructed from these films.

Amorphous silicon thin films and p-i-n assemblies have been deposited by glow discharge and reactive sputtering techniques. The optical constants of doped and intrinsic a-Si:H thin films were determined by VASE and the film thickness verified by Scanning Electron Microscopy studies. The optical constants of commercially available transparent conducting oxide (TCO) coated substrates have also been determined by VASE.

The experimental transmission spectra of p-i-n assemblies are compared with transmission spectra that have been modeled using the measured optical constants. Results of modeling different a-Si:H solar cell structures using these materials are presented, including a study of the optimal TCO layer thickness for p-i-n a-Si:H solar cells. This work shows that optical admittance modeling gives a good prediction of the optical behavior of p-i-n assemblies, but that accurate measurements of the optical constants of the component films are required in order to model effectively the optical quantum efficiency and photocurrent.
Relation between Growth Precursors and Film Properties for Plasma Deposition of a-Si:H at Rates up to 100 Å/s
Authors: Kessels W.M.M. , Smets A.H.M. , Hoefnagels J.P.M. , Boogaarts M.G.H. , Schram D.C. , Sanden M.C.M. van de
Published: April 2011

From investigations on the SiH3 and SiH radical density and the surface reaction probability in a remote Ar-H2-SiH4 plasma, it is unambiguously demonstrated that the a-Si:H film quality improves significantly with increasing contribution of SiH3 and decreasing contribution of very reactive (poly)silane radicals. Device quality a-Si:H is obtained at deposition rates up to 100 Å/s for conditions where film growth is governed by SiH3 (contribution ∼90%) and where SiH has only a minor contribution (∼2%). Furthermore, for SiH3 dominated film growth the effect of the deposition rate on the a-Si:H film properties with respect to the substrate temperature is discussed.
Ion-Assisted Deposition of Silicon Epitaxial Films with High Deposition Rate Using Low Energy Silicon Ions
Authors: Oberbeck Lars , Wagner Thomas A. , Bergmann Ralf B.
Published: April 2011

Ion-assisted deposition (IAD) enables low temperature (≥ 435°C), high-rate (≤ 0.5 μm/min) epitaxial growth of silicon films. Therefore, IAD is an interesting deposition technique for microelectronic devices and thin film solar cells. The Hall-mobility of monocrystalline epitaxial layers increases with deposition temperature Tdep and reaches values comparable to those of bulk Si at Tdep ≥ 540°C. Polycrystalline epitaxial layers exhibit inhomogeneous electrical properties, as shown by Light Beam Induced Current measurements. Recombination within the grains dominates over recombination at grain boundaries. Secco etching identifies an inhomogeneous density of extended structural defects in the polycrystalline epitaxial layers and in the substrate. A major part of the extended defects in the epitaxial layers originates from defects in the substrate.
Low temperature selective Si epitaxy by reduced pressure chemical vapor deposition introducing periodic deposition and etching cycles with SiH4, H2 and HCl
Authors: Kim Hong-Seung , Shim Kyu-Hwan , Lee Jeong-Yong , Kang Jin-Yeong
Published: April 2011

This paper presents the experimental results of selective Si epitaxial growth from 650 °C to 700 °C on (100) silicon wafers with oxide patterns using reduced pressure chemical vapor deposition with the SiH4-HCl-H2 gas system. In addition, an HCl etching process is introduced and the conditions of the deposition and etching processes are addressed to sustain the selectivity. As a result, we noted that the addition of HCl serves not only to reduce the growth rate on bare Si, but also to suppress the nucleation on SiO2. In these experiments it has been also observed that the Si layer was grown to 3 nm while sustaining the selectivity. Moreover, further introduction of the HCl etching process following the deposition allowed a 50 nm-thick film to sustain the selectivity for twenty periods.
Crystalline Si Films Grown Epitaxially at Low Temperatures by ECR-PECVD
Authors: Platen J. , Selle B. , Christiansen S. , Nerding M. , Schmidbauer M. , Fuhs W.
Published: April 2011

Electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) is used to grow thin epitaxial films on Si(100) wafers. We report on systematic variations of deposition parameters like substrate temperature, substrate dc bias voltage, and gas composition. The structural quality was significantly improved by increasing the substrate temperature from 325 to 500 °C. Simultaneously, compressive lattice strain tends to increase. A negative dc bias voltage resulted in highly disordered films and increased surface roughness due to enhanced ion damage. In contrast positive bias voltages decreased the defect creation by reducing the ion bombardment of the surface during growth. Under so far optimized conditions the remaining disorder is given by two-dimensional, extended defects running parallel to the growth direction and forming grain boundaries with a lateral spacing of 500–700 nm. The single grains are essentially free of one- and two-dimensional defects and show the same orientation as the substrate. By reducing the H2 dilution and adding Ar to the excitation gas the deposition rate increased from 5.3 to 16.2 nm/min. This resulted in inferior structural quality which might be attributed to the reduced etching effect, the enhanced ion bombardment and/or the increased growth rate.
Room Temperature Recrystallization of Electroplated Copper Thin Films: Methods and Mechanisms
Authors: Walther D. , Gross M. E. , Evans-Lutterodt K. , Brown W. L. , Oh M. , Merchant S. , Naresh P.
Published: April 2011

We report a comparison of the room temperature recrystallization of electroplated (EP) copper in blanket films as a function of thickness measured by focused ion beam (FIB) microscope images and sheet resistance measurements. Both sets of data show an increase in rate with film thickness from 0.75νm up to 5νm, while little recrystallization is observed in films thinner than 0.75νm. Interestingly, the recrystallization rates from FIB analysis are consistently faster than those from the sheet resistance measurements. These data suggest that the recrystallization is initiated close to the top surface of the EP Cu film, but that in thinner films a high surface-to-volume ratio allows surface inhibition or pinning to retard the transformation. A Johnson-Mehl-AvramiKolmogorov (JMAK) analysis of the two data sets yields unusually high values for the Avrami exponent μ of up to 7 for the FIB data, while lower values of around 4 are obtained for the sheet resistance data. X-ray diffraction pole figures of the films have also been collected and correlations between the crystallographic texture, film thickness and recrystallization are discussed.
Electromigration Characterization Versus Texture Analysis in Damascene Copper Interconnects
Authors: Berger T. , Arnaud L. , Gonella R. , Touet I. , Lormand G.
Published: April 2011

We have studied the effect of texture (X-ray diffraction pole figures) and grain morphology (Focus Ion Beam cross-sections) on the electromigration performances of copper damascene interconnects. Three different metallizations have been characterized : Chemical Vapor Deposition copper deposited on TiN (process A) and electroplated copper deposited either on Ta (process B) or TaN (process C). The reliability performance of these interconnects has been evaluated using both Wafer Level Reliability (WLR) and Package Level Reliability (PLR) tests on 4 and 0.6 νm wide lines using single metal level test structures. On the basis of the activation energy values and failure analysis observations, we concluded that interfacial diffusion plays a key role in the electromigration phenomenon for processes B and C whereas grain boundaries seem to be the active diffusion path for process A. The existence of several failure mechanisms during electromigration tests (interfacial or grain boundary diffusions), the impact of the damascene architecture on microstructure (sidewall textures and non columnar grain shapes) and the copper propensity for twinning seem to mask the impact of texture on the electromigration reliability of copper damascene interconnects.
Novel Low-k Dual-phase Materials Prepared by PECVD
Authors: Grill Alfred , Patel Vishnubhai
Published: April 2011

Dielectric materials based on Si, C., O, H (SiCOH) have been demonstrated previously with dielectric constants of about 2.8. This value could be potentially further reduced by increasing/introducing porosity in the SiCOH films. Depositing multiphase films containing at least one thermally unstable phase and annealing the films to remove this labile phase from the material could create the enhanced porosity. Dual-phase materials, SiCOH-CH, have been prepared in the present study by PECVD from mixtures of a SiCOH precursor with a hydrocarbon. The films have been characterized as-deposited and after thermal anneals of up to 4 hours at 400°C. The atomic composition of the films has been determined by RBS and FRES analysis and their optical properties have been determined by FTIR and n&k measurements. Metal-insulator-silicon structures have been used to measure the electrical properties of the dual-phase films. After an initial anneal at 400°C, accompanied by a significant loss of CH and some SiH species and a thickness loss of up to 50%, the films stabilized. Depending on the deposition conditions and concentration of the CH precursor in the feed gas, the dielectric constant decreased by 10-15% during the stabilization anneal and reached values as low as 2.4. These initial results indicate the possibility to further reduce the dielectric constant of PECVD produced SiCOH films and the potential to incorporate such films in the interconnect structures of future ULSI chips.
High-Temperature Mechanical Behavior and Phase Morphology of Poly(Tetrafluoroethylene)/Siloxane Nanocomposites Used as Ultra Low-k Dielectrics
Authors: Xu Ping , Qu Shichun , Rosenmayer Tom , Lin Min Y.
Published: April 2011

Poly(tetrafluoroethylene) (PTFE)/siloxane nanocomposites have been prepared as ultra low-k dielectrics. These new nanocomposites show excellent high-temperature mechanical properties compared to unfilled PTFE while their dielectric constant almost remains unchanged. Specifically, the data from the dynamic mechanical study indicates that these nanocomposites have the mechanical behavior similar to that of crosslinked polymers. Small-angle neutron scattering (SANS) has been carried out to characterize the phase morphology of the PTFE/siloxane nanocomposites and the size of the inorganic networks. It has been shown that no phase separations or orientations appear in these nanocomposites in the range of 12 to 469 nm. These SANS results suggest that these materials are single-phase nanocomposites that are very homogeneous and isotropic. They are basically PTFE-based molecular composites.
Atomic Layer CVD for Continuously Shrinking Devices
Authors: Haukka Suvi , Elers Kai-Erik , Tuominen Marko
Published: April 2011

This paper will review the basics of the atomic layer chemical vapor deposition (ALCVD) thin film growth technique. The emphasis is on the ALCVD metal nitride growth and dual damascene barrier requirements.
A Study on CVD TaN as a Diffusion Barrier for Cu Interconnects
Authors: Im Se-Joon , Kim Soo-Hyun , Park Ki-Chul , Cho Sung-Lae , Kim Ki-Bum
Published: April 2011

Tantalum nitride (TaN) films were deposited using pentakis-diethylamido-tantalum [PDEAT, Ta(N(C2H5)2)5] as a precursor. During film growth, N- and Ar-ion beams with an energy of 120 eV were supplied in order to improve the film quality. In case of thermallydecomposed films, the deposition rate is controlled by the surface reaction up to about 350 °C with an activation energy of about 1.07 eV. The activation energy of the surface reaction controlled regime is decreased to 0.26 eV when the Ar-beam is applied. However, in case of Nbeam bombarded films, the deposition is controlled by the precursor diffusion in gas phase at the whole temperature range. By using Ar-beam, the resistivity of the film is drastically reduced from approximately 10000 µω-cm to 600 µω-cm and the density of the film is increased from 5.85 g/cm3 to 8.26 g/cm3, as compared with thermally-decomposed film. The use of N-beam also considerably lowers the resistivity of films (∼ 800 µω-cm) and increases the density of the films (7.5 g/cm3). Finally, the diffusion barrier properties of 50-nm-thick TaN films for Cu were investigated aftre annealing by X-ray diffraction analysis. The films deposited using N- and Arbeam showed the Cu3Si formation after annealing at 650 °C for 1 hour, while thermallydecomposed films showed Cu3Si peaks firstly after annealing at 600 °C. It is considered that the improvements of the diffusion barrier performance of the films deposited using N- and Ar-ion beam are the consequence of the film densification resulting from the ion bombardment during film growth.
The 2,2,6,6-Tetramethyl-2-Sila-3,5-Heptanedione Route to the Chemical Vapor Deposition of Copper for Gigascale Interconnect Applications
Authors: Claessen Rolf U. , Welch John T. , Toscano Paul J. , Banger Kulbinder K. , Kornilov Andrei M. , Eisenbraun Eric T. , Kaloyeros Alain E.
Published: April 2011

A new class of copper(II) precursors containing silylated β-diketonate ligands has been developed for the chemical vapor deposition (CVD) growth of copper for applications in ultralarge scale integration interconnect schemes, including conformal seed layer for gigascale Cu integration and ultrathin Cu lines with enhanced conductivity characteristics. Cu(tmshd)2 (tmshdH = 2,2,6,6-tetramethyl-2-sila-3,5-heptanedione) has been studied as a representative compound and is appreciably more volatile than nonsilylated compounds such as Cu(tmhd)2 or Cu(tmod)2 (tmhdH = 2,2,6,6-tetramethyl-3,5-heptanedione; tmodH = 2,2,7-trimethyl- 3,5- octanedione). The CVD process employs Cu(tmshd)2 as the metalorganic precursor and hydrogen as the reducing and carrier gas. These films were deposited using a custom made, cold wall, stainless steel CVD. Copper films were produced at a substrate temperature of 250 – 320 °C, hydrogen flow rates of 20 - 100 sccm, deposition pressure of 0.2 - 1 Torr, and a source temperature of 120 – 135 °C. The films were analyzed by X-ray photoelectron spectroscopy, cross section scanning electron microscopy, transmission electron microscopy, four-point resistivity probe, Rutherford backscattering spectrometry and Auger electron spectroscopy.
Trench and Via Filling with Electroplated Copper: Effect of Current Density and Pulse Waveform
Authors: Seah C. H. , Mridha S. , Siew Y. K. , Sarkar G. , Chan L. H.
Published: April 2011

A study was carried out to investigate the effect of current density and pulse waveform on the filling of line trenches and contact vias with aspect ratio of 2:1 for sub-0.25 µm device manufacturing using normal pulse plating of copper. The growth pattern of the copper films deposited using 0.05 and 0.10 A/cm2 current density gave no significant difference. Small grains were seen to have nucleated uniformly across the line trenches and via holes after 1 second of electroplating. With increasing the deposition time to 2 seconds, a slight buildup of the film thickness was observed in both trenches and vias without significant increase in the size of the copper grains. Grain growth involving the coalescence of small grains occurred after 5 seconds of plating and a further buildup in thickness and fill up of the trenches and vias occurred after 10 seconds of deposition.

When the patterned wafers were plated with a pulse waveform of 3 ms on and 0.5 ms off, the filling of trenches could not be complete after 30 seconds of electroplating. A complete filling of the trenches was achieved within 30 seconds of deposition using a pulse waveform of 6 to 8 ms on and 1 to 2 ms off. When the on-period was increased above this range to 9.9 ms, voids were observed at the centre of the via holes.
Kinetic Roughening During Rare-Gas Homoepitaxy
Authors: Nabighian E. , Bartelt M. C. , Zhu X.D.
Published: April 2011

Using an optical reflectivity difference technique, we monitored the growth of multilayer Xe films on a commensurate monolayer of Xe on Ni(111), from 35 to 60K. A transition occurs near 40K, from rough growth at low temperature to quasi-layer-by-layer growth characterized by persistent oscillations in the reflectivity difference. We discuss this transition in terms of changes in the island formation process and the onset of second layer nucleation. The Xe sticking coefficient at 40K is obtained from the period of the oscillations in the reflectivity difference. We find that the sticking coefficient decreases with increasing fihn thickness at fixed Xe pressure.
Diamond Synthesis on Glassy Substrate With Completely Closed Reaction Chamber
Authors: Hayashi Rie , Onishi Fumitomo , Uede Mayu , Takagi Yoshiki
Published: April 2011

For diamond synthesis with gaseous reaction, crystalline materials such as Si and Mo were used as substrates. In this study, we used materials of noncrystalline oxide for substrates, for example, quartz glass.

We used unique apparatus for diamond synthesis, completely closed system, no reaction gas was introduced to the chamber and no reactant gas was evacuated from it.

Deposits were Identified as diamond with SEM, AFM and Raman spectra. With these results, we successfully confirmed our samples as diamond particles on quartz glass substrate.
Raman Studies Of LiMn2O4 Films Grown by Laser Ablation
Authors: Camacho-Lopez M.A. , Escobar-Alarcon L. , Haro-Poniatowski E. , Julieni C.
Published: April 2011

Polycrystalline thin films of lithium manganese oxide have been grown using the pulsed-laser deposition (PLD) technique. Films of LiMnO2O4, were deposited onto Si substrates heated at temperature lower than 300°C from a sintered composite target (LiMn2O4+Li2O) irradiated with a Nd:YAG laser. The structural characterizations of these films have been carried out by Raman scattering spectroscopy which probe the local environment of cations in the LiMn2O4 framework. Raman spectra of PLD LiMn2O4 films have been investigated as a function of various growth conditions, i.e. substrate temperature, partial oxygen pressure in the deposition chamber, and target composition.
Highly Ionized Carbon Plasma Generation by Dual-Laser Ablation for Diamond-Like Carbon Film Growth
Authors: Witanachchi S. , Miyawa A. M. , Mukherjee P.
Published: April 2011

Carbon plasmas produced by excimer laser ablation show a low ionization yield of about 8-10%. The coupling of a second CO2laser pulse into the plasma in the dual-laser ablation process significantly increases the plasma temperature and the ionization. The resulting rapid expansion of the plasma gives rise to high ion kinetic energies and broader ion expansion profiles [1]. Optical emission spectroscopy and an ion probe have been used to investigate the dynamics of the carbon plasma. Single and dual-laser ablated carbon plumes have been deposited on DC-biased silicon substrates to form amorphous carbon films. The diamond-like behavior of these films was studied by Raman spectroscopy. The Raman spectra were deconvolved to gauge the effect of the density and the energy of ions on the formation of diamond-like sp3 -bonded carbon (DLC) films. The advantage offered by the dual-laser process for the growth of DLC films is discussed.
Ordered Thin Films of Perylenetetracarboxylicdianhydride-bisimide and bis-(N-alkyl)-Quinacridone Dyes
Authors: Back Andrew , Alloway Dana , Schlettwein Derck , Schilling Brook , Wang J.-F. , Carducci Mike , Armstrong Neal R.
Published: April 2011

We review here the recent characterization of vacuum deposited monolayer and multilayer thin films of two different perylenetetracarboxylic-dianydride-bisimides (Cn-PTCDI; n =4,5), quinacridone, and two new bis-(N-alkyl)-quinacridone dyes (DIQA and DEHQA) on single crystal alkali halides using a combination of in situ luminescence spectroscopies and ex situ tapping mode AFM. Flat lying monolayer structures are indicated for PTCDA on the (100) faces of NaCl, KCl and KBr, for C4-PTCDI on KCl, for C5-PTCDI on both KCl and KBr and for DIQA on both KCl and KBr. Coherent thin films, exhibiting layer-by-layer growth can be achieved for PTCDA on all substrates, for C4-PTCDI on KCl and for DIQA on both KBr and KCl. Both C4-PTCDI and DIQA appear to fulfill the requirements for dyes which exhibit layered growth with the molecular plane inclined at steep angles to the surface normal.
Macromolecular Crystals in the Service of Biotechnology and Medicine
Authors: Mcpherson Alexander
Published: April 2011

The application of genetic and molecular biological methods to the engineering of proteins, the engine of the biotechnology revolution, has become increasingly dependent on knowledge of protein, nucleic acid and virus molecular structure. Structural information of high precision, essential to this enterprise, can only be obtained through X-ray crystallographic techniques. The quality of this information is directly a function of the properties and degree of perfection of the crucial intermediates, the macromolecular crystals. As a consequence, there is now broad and intense interest in developing new methods, procedures and reagents for the nucleation and growth of such crystals. There is, in addition, an expanded interest in the properties of biological crystals and the use of physical measurements in improving approaches to growing better and larger crystals. Here some of the fundamentals of macromolecular crystal growth will be reviewed, and some current trends in the field remarked upon, including the new initiative to develop a national structural genomics program.
Moving Steps and Crystal Defects on Spinel Surfaces
Authors: Yanina S.V. , Carter C.B.
Published: April 2011

The morphology of the reconstructed {001} surface of MgAl2O4 spinel is studied by scanning probe microscopy (SPM). The observations show that the {001} surface of MgAl2O4 may exist as two variants which are related through 90° rotation about the [001] axis. These surface variants exhibit different lateral forces and tend to grow/evaporate and to etch anisotropically along either the [110] or the [110] directions of the crystal. Surface terraces that are formed by different variants were found to be separated by ∼2.0 Å-high steps, while the terraces which belong to the same variant are separated by ∼4.0 Å-high steps. It is expected that the origins of the preferential motion of ledges on the {001} spinel surface is related to the anisotropic distribution of cations along either the [110] or the [110] directions within the {001} crystal planes in the spinel crystal.
Resolving the Control of Magnesium on Calcite Growth: Thermodynamic and Kinetic Consequences of Impurity Incorporation for Biomineral Formation
Authors: Davis Kevin J. , Dove Patricia M. , Yoreo James J. De
Published: April 2011

Magnesium is a key determinant in CaCO3 biomineral formation and has recently emerged as an important paleotemperature proxy. Atomic force microscopy (AFM) was used to determine the fundamental thermodynamic and kinetic controls of Mg2+ on calcite morphology and growth. Comparison of directly measured monomolecular step velocities (vs±) to theoretical crystal growth impurity models demonstrated calcite inhibition due to enhanced mineral solubility through Mg2+ incorporation. Terrace width (λ) measurements independently supported an incorporation mechanism by indicating a shift in the effective supersaturation (σeff) of the growth solutions in the presence of Mg2+. This study resolves the controversy over the molecular-scale mechanism of calcite inhibition by Mg2+ and provides an unambiguous model for the thermodynamic and kinetic consequences of impurity incorporation into CaCO3 biominerals.
Defect population and electrical properties of Ar+-laser crystallized polycrystalline silicon thin films
Authors: Christiansen S. , Nerding M. , Eder C. , Andrae G. , Falk F. , Bergmann J. , Ose M. , Strunk H. P.
Published: April 2011

We crystallize amorphous silicon (a-Si) layers (thicknesses: ∼300nm and ∼1300nm for comparison) that are deposited on glass substrates (Corning 7059) by low pressure chemical vapor deposition using a continuous wave Ar+-laser. We scan the raw beam with a diameter of ∼60νm in single traces and traces with varying overlap (30-60%). With optimized process parameters (fluence, scan velocity, overlap) we achieve polycrystalline Si with grains as wide as 100νm. The grain boundary population is dominated by first and second order twin boundaries as analyzed by electron backscattering analysis in the scanning electron microscope and convergent beam electron diffraction in the transmission electron microscope. These twins are known not (or only marginally) to degrade the electrical properties of the material. In addition to twins, dislocations and twin lamellae occur at varying densities (depending on grain orientation and process parameters). The recombination activity of the defects is analyzed by EBIC and according to these measurements crystallization receipts are defined that yield the reduction of electrically detrimental defects.
Surface Treatment on Silicon Field-Emission Cathodes
Authors: Hajra M. , Chubun N.N. , Chakhovskoi A.G. , Hunt C.E.
Published: April 2011

Arrays and single-tip p-type silicon micro-emitters have been formed using a subtractive tip fabrication technique. Following fabrication, several different surface treatments have been attempted for comparison. We utilized ion and electron bombardment at elevated pressures (with interrupted pumping), and also hydrogen seasoning during field emission operation. The objectives of these treatments include stabilization of the emission, lowering the effective workfunction, and reducing low-frequency noise. The tips were evaluated using I-V measurements in the diode configuration. A flat Si anode, spaced nominally 6 μm and 150 μm from the cathode, was used. For the purpose of treatment, the field emission characteristics are measured in a high vacuum chamber at a pressure range between 10−5 and 10−8 Torr. The results suggest that the emitters benefit from seasoning or conditioning, for optimal performance, low noise, minimum work function and maximum reproducibility and reliability over the lifetime of the cathode.
Solid-State Field-Controlled Electron Emission: An alternative to thermionic and field-emission
Authors: Binh Vu Thien , Dupin J.P. , Thevenard P. , Guillot D. , Plenet J.C.
Published: April 2011

In the solid-state field-controlled emitter (SSE), the emission barrier, which is the factor of utmost importance for surface electron emission, is tailored by a controlled extrinsic parameter like the injected space charge located near the surface. This is done by depositing an ultra-thin wide band-gap semiconductor layer on a metallic surface. It is an alternative approach to the thermionic or field emission for which the work function value is intrinsic to the material used. The emission current measurements from the SSE cold cathodes show stable emission, at low applied field (≈50 V/μm) and in poor vacuum (≈10−7 Torr). The new emission mechanism has been modeled, the calculations and the theoretical analysis confirm the experimental results. The fabrication of the SSE, either by a sputter deposition in vacuum or by a sol-gel technique, meets most of the demands specific to high throughput fabrication of cold cathodes with large emitting area dedicated to applications in vacuum microelectronics.
Field Emitter Cathodes and Electric Propulsion Systems
Authors: Marrese Colleen M. , Polk James E. , Mueller Juergen
Published: April 2011

Replacing hollow and filament cathodes with field emitter (FE) cathodes could significantly improve the scalability, power, and performance of some meso- and microscale Electric Propulsion (EP) systems. The propulsion system environments and requirements and the challenges in integrating these technologies are discussed to justify the recommended cathode configurations. Required cathode technologies include low work function coatings on Si or Mo Field Emitter Array (FEA) cathodes with arc protection and electrostatic ion filters.
Electron Emission from Microwave-Plasma Chemically Vapor Deposited Carbon Nanotubes
Authors: Tzeng Yonhua , Liu Chao , Cutshaw Calvin , Chen Zheng
Published: April 2011

A microwave plasma CVD reactor was used for the deposition of carbon nanotubes on substrates. Hydrocarbon or oxyhydrocarbon mixtures were used as the carbon source. Hot electrons in the microwave plasma at temperatures exceeding 10,000C provided a means of dissociating the vapor or gas feedstock, heating the substrate, and allowing gas species to react in the gas phase as well as on the surface of the substrate leading to the deposition of desired carbon coatings. A high vacuum chamber was used to characterize the electron emission properties of these carbon nanotube coatings using a one-millimeter diameter tungsten rod with a hemispherical tip as the anode while the carbon nanotube coatings served as the cathode. The current-voltage characteristics of the carbon nanotube coatings were measured and used for calculating the electric field at which electron emission turned on as well as calculating the field enhancement factor of the carbon nanotubes. Field emission of electrons from carbon nanotubes starting from an electric field lower than 1 volt per micrometer has been achieved.
Hot-Filament Assisted Fabrication of Carbon-Nanotube Electron Emitters
Authors: Tzeng Yonhua , Liu Chao , Chen Zheng
Published: April 2011

A hot-filament CVD reactor was used for the deposition of carbon nanotubes on substrates. Hydrocarbon or oxyhydrocarbon mixtures were used as the carbon source. Hot filaments at temperatures exceeding 2000C provided a means of dissociating the vapor or gas feedstock, heating the substrate, and allowing gas species to react in the gas phase as well as on the surface of the substrate leading to the deposition of desired carbon coatings. A high vacuum chamber was used to characterize the electron emission properties of these carbon nanotube coatings using a one-millimeter diameter tungsten rod with a hemispherical tip as the anode while the carbon nanotube coatings served as the cathode. The current-voltage characteristics of the carbon nanotube coatings were measured and used for calculating the electric field at which electron emission turned on as well as calculating the field enhancement factor of the carbon nanotubes. Field emission of electrons from carbon nanotubes starting from an electric field of as low as 1-2 volts per micrometer was achieved.
Quantum Transport Through Intermolecular Nanotube Junctions
Authors: Buldum Alper , Lu Jian Ping
Published: April 2011

Quantum transport properties of intermolecular nanotube contacts are investigated. We find that atomic structure in the contact region plays important roles and resistance of contacts varies strongly with geometry and nanotube chirality. Nanotube end-end contacts have low resistance and show negative differential resistance (NDR) behavior. Exerting small pressure/force between the tubes can dramatically decrease contact resistance, if the contact is commensurate. Significant variation and nonlinearity of contact resistance may lead to new device applications.
Well-aligned carbon nanofibers synthesized by electron cyclotron resonance chemical vapor deposition
Authors: Hoshi Fumiyuki , Tsugawa Kazuo , Goto Akiko , Ishikura Takefumi , Yumura Motoo , Koga Yoshinori , Yamashita Satoshi , Hirao Takashi , Fujiwara Shuzou , Yumura Motoo , Koga Yoshinori
Published: April 2011

Aligned carbon nanofibers and hollow carbon nanofibers were grown by MW ECR-CVD method using methane and argon mixture gas at the temperature of 550••. Carbon nanofibers and hollow carbon nanofibers were deposited perpendicularly on Si substrate and on Si substrate coated with Ni catalyst, respectively. Raman spectra of aligned carbon nanofibers and hollow carbon nanofibers showed new bands of 1340 and 1612 cm-1 of the first-order Raman scattering and 2660, 2940 and 3220 cm-1 of the second-order Raman scattering. The second-order Raman scattering bands were assigned to two overtone and one combination bands on the basis of a similar assignment of micro crystal graphite. Combination bands are intense unusually. Field emitter characteristics of the well-aligned carbon nanofibers and hollow carbon nanofiberswere investigated and the current densities were 7.25 mA/cm2 and 0.69 mA/cm2at 12.5 V/μm, respectively.
In-situ Fluid Experiments in Carbon Nanotubes
Authors: Gogotsi Yury , Libera Joseph A. , GüvenÇ Yazicioglu Almila , Megaridis Constantine M.
Published: April 2011

Closed-end multi-wall carbon nanotubes, which contain an encapsulated aqueous multi-phase fluidunder high pressure, have been produced by hydrothermal synthesis. These nanotubes are leak-tight by virtue of holding the fluid at the high vacuum of a transmission electron microscope (TEM) and can be used as a testplatform for unique in-situ nanofluidic experiments in TEM. They form an experimental apparatus, which is at least two orders of magnitude smaller than the smallest capillaries used in fluidic experiments so far. Excellent wettability of the carbon tube walls by the liquid and a dynamic behavior similar to that in micro-capillaries demonstrates the possibility of use of nanoscale (<100 nm) tubes in nanofluidic devices.However, complex interface behavior that can potentially create hurdles to fluid transport is also demonstratedherein.
Quantum coherence in sub-10 nm metal wires
Authors: Natelson Douglas , Willett Robert L. , West Kenneth W. , Pfeiffer Loren N.
Published: April 2011

We report weak localization studies of quantum coherence in metal nanowires with widths as small as 5 nm, demonstrating that structures fabricated at sub-50 nm length scales can reveal coherence phenomena not accessible in larger devices. Through selective etching of cleaved molecular-beam epitaxy (MBE)-grown substrates, we produce precise nanoscale surface relief then used as a stencil for metal deposition. This nonlithographic method of lateral definition allows the fabrication of metal (AuPd) nanowires greater than one micron in length with widths below 5 nm, a previously unexplored size regime in studies of quantum corrections to the conductance of disordered metals. Analyzing magnetoresistance data, we find that the coherence time,Tφ, shows a low temperatureTdependence close to quasi-1D theoretical expectations (Tφ∼ T-2/3in 5 nm wide wires, while exhibiting a relative saturation asT0 for wide samples of the same material. Since an externally controlled parameter, the sample geometry, can cause a single material to exhibit both suppression and divergence ofTφ, this finding provides a new constraint on models of dephasing phenomena.
Basic:

B

io-Inspired

A

ssembly of

S

emiconductor

I

ntegrated

C

ircuits
Authors: Bashir R. , Lee S. , Guo D. , Pingle M. , Bergstrom D. , Mcnally H. A. , Janes D.
Published: April 2011

In the recent years, biologically-inspired self-assembly of artificial structures, some with useful optical properties, has been demonstrated. However, to date there has been no demonstration of self-assembly of useful electronic devices for the construction of complex systems. In this paper, a new process called BASIC (Bio-Inspired Assembly of Semiconductor Integrated Circuits) is proposed. The main theme is to use the mutual binding (hybridization) and specificity of DNA strands (oligonucleotides) for the assembly of useful silicon devices on silicon or other substrate. These devices need to be ‘released’ from their host substrate into a liquid medium where they can be functionalized with single stranded DNA. Silicon-on-insulator (SOI) substrates, which naturally lend themselves for such application, due to the presence of an oxide layer underlying the silicon layer, are used. These devices can vary in size and have a thin gold layer on one surface. This approach can be used to assemble micro and nano-scale devices and circuits and can also be a powerful technique for heterogeneous integration of materials (e.g. Si on Glass or polymer). The general idea of the BASIC process can also be extended to be used with any antibody/antigen complex. Preliminary results regarding the fabrication and release of the device islands will be presented. In addition, surface AFM characterization of the gold surfaces, prior to attachment of bio-molecules, is also presented.
Relation between Local Composition, Chemical Environment and Phase Shift Behavior in Cr-Based Oxycarbonitride Thin Films
Authors: Smith J.R. , Graat P.C.J. , Bonnell D.A. , French R.H.
Published: April 2011

The latest deep ultra-violet (DUV) photomask technology requires macroscopic properties such as optical transmission, reflectance, and chemical reactivity to be precisely controlled. Therefore, a fundamental understanding of the relationship between atomic bonding and nanometer scale property variation is required. Thin films of Cr-OC-N are compositionally graded to produce specific attenuation and phase shift of optical radiation. A combination of techniques was used to relate the local atomic bonding to macroscopic properties. Sputtered neutral mass spectroscopy was used to resolve local composition, and variable angle spectroscopic ellipsometry was used to determine local optical properties (on nm scale) that are then related to local composition. Core level shifts in X-ray photoelectron spectroscopy characterize changes in the Cr environment associated with changes in composition. A model is suggested in which bonding at the atomic level is controlled within different 10-100 nm sized regions which can be combined to produce arbitrary optical properties.
Method for Measuring Profiles of Photoacid Patterns in Chemically Amplified Resists
Authors: Feke Gilbert D. , Grober Robert D. , Pohlers Gerd , Cameron James F.
Published: April 2011

We describe a method based on single molecule probing of acid concentration to measure the profiles of photogenerated acid patterns in chemically amplified resist films. We further present preliminary data which demonstrates the viability of this method.
Magnetic Nanoparticle Arrays with Ultra-Uniform Length Electrodeposited in Highly Ordered Alumina Nanopores(“Alumite”)
Authors: Metzger Robert M. , Sun Ming , Zangari Giovanni , Shamsuzzoha Mohammad
Published: April 2011

We report nanometer-scale ordered arrays of cylindrical magnetic nanoparticles with low aspect ratio and ultra-high uniformity. Protracted anodization provides hexagonally ordered nanopores in amorphous Al2O3. For instance, pulsed electrochemical deposition grows Co particles of uniform length from the bottoms of these pores: these particles are polycrystalline and randomly oriented. The magnetism of the array is dominated by particle shape and by inter-particle magnetostatic interactions. A very clear transition of the anisotropy from perpendicular to in-plane is observed at a height to radius ratio of about 2. This pulse-reverse electrodeposition shows great promise for a reliable synthesis of uniform nanostructures of many metals.
Preparation and Optical Properties of Au-shell Submicron Polystyrene Particles
Authors: Ji Tianhao , Avny Yair , Davidov Dan
Published: April 2011

Recently, there has been an immense interest in the fabrication of composite nanoparticles, such as core-shell structural materials [1-6]. These core-shell composite particles may show special properties different from those of the core or shell particles. Thus, Au or Ag nanoparticcles were coated by silica. The silica shell not only stabilizes the colloidal Au nanoparticles, but also influences their optical property [3,6]. Furthermore, Halas et al. [5] have demonstrated that by varying the ratio of gold-shell to silica-core, the plasmon optical resonance of the Au shell and silica core strongly shifts across the visible spectrum and into the infrared region. Core-shell particles can be used as building blocks for different devices including tunable Photonic-Band-Gap (PBG) structures. Herein, we report on the fabrication of such particles with emphasis on the preparation of the Au nano-shells coated polystyrene (PS) with a diameter of about 700 nm.