bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Application of On-Wafer Small Angle X-Rayscattering for the Quantification of Pore Morphology in Low Kporous Silk Semiconductor Dielectrics
Authors: Landes Brian , Kern Brandon , Stokich Ted , Niu Jason , Yontz Dorie , Radler-Carol Mike , Ouellette Mohler Kacee , Lucero Sebring , Hahnfeld Jerry , King Danny , Quintana John , Weigand Steve
Published: June 2019

The continual drive for faster interconnects requires the development of new interlayer dielectricmaterials with k values less than 2.1. Porous SiLKTM semiconductor dielectric resin wasdeveloped to achieve these low dielectric constants by introducing nanometer-sized pores intothe dense SiLK resin matrix. A quantitative description of the nano-porous morphology in low-kinterlayer dielectrics can be difficult to achieve for many reasons, including: complexities in theporous structure (size range, geometry, pore/pore interaction), inadequate mathematicaldescriptors, limitations of existing metrology technology, and availability of “tailor-made” experimental samples with a wide range of pore morphologies. On-wafer quantification of poremorphology is even more difficult as data must be obtained from extremely limited samplevolumes (thin films of ∼100-500 nm) residing on thick silicon (Si) wafer substrates.

This paper will focus on the design, development and successful application of on-wafer smallangle x-ray scattering (SAXS) technology to characterize the morphology of porous SiLK resin.It will be demonstrated, by example, that this technology is able to deliver rapid quantificationover the entire pore size range for these systems. Recently developed data acquisition, reductionand analysis tools will be described. Direct evaluation of the strengths and challenges of severalmodels used to generate average pore size and pore size distribution will be reviewed. Finally,additional capabilities offered by this technology (wafer mapping and detection of “killer” pores)will also be discussed.
Solvent diffusion in porous low-k dielectric films
Authors: Shamiryan Denis , Maex Karen
Published: June 2019

Porous materials are being investigated as low dielectric constant (low-k) materials. While porosity decreases the k-value of a material by decreasing its density, it simultaneously allows unwanted adsorption and diffusion of chemicals inside the porous matrix. To investigate this, different porous low-k materials, specifically silicon oxycarbide (SiOCH), methylsilsesquioxane (MSQ), and a polymer, were exposed to polar (ethanol) and non-polar (toluene) solvents. A difference in diffusion of polar and non-polar solvents would be an indication of the density of polar centers which attract polar molecules (such as water) and increase the dielectric constant of a film. The diffusion coefficient for toluene at room temperature was found to be approximately 2×10-5 cm2/sec for MSQ (40% porosity), 10-7 cm2/sec for SiOCH (7% porosity), 2×10-8 cm2/sec for the polymer. The observed diffusion can be described by a model of a viscous flow in a porous medium. The toluene/ethanol diffusion coefficient ratios were 4.4, 1.3, 1 for MSQ, SiOCH, and the polymer, respectively. The difference in toluene/ethanol diffusion can potentially be used to screen a material's affinity for water adsorption.
Ferromagnetic Metal Nanoclusters Encapsulated in Carbon Nanotubes
Authors: Ma Xicheng , Cai Yuanhua , Lun Ning , Wen Shulin
Published: June 2019

Ferromagnetic nanoclusters are very useful for a magnetic recording. However, the application of ferromagnetic nanoclusters is limited due to air-oxidation. One way to solve air- oxidation is to encapsulate ferromagnetic nanoclusters with inert materials such as carbon when they are produced. This allows us to keep excellent magnetic properties for a long time. In this work, we report a very simple synthetic method of carbon nanotubes (CNTs) encapsulated ferromagnetic cobalt nanoclusters by catalytic decomposing benzene over Co/silica-gel nano- scale catalysts. Unlike previous reports, the catalysts do not need to be pre-reduced prior to the forming of CNTs encapsulated cobalt nanoclusters, thus, the advantage of this method is that CNTs encapsulated ferromagnetic nanoclusters can be produced in one step, at a relatively low cost. High-resolution Transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) were used to characterize the microstructures and compositions of the products. Experimental results revealed that the encapsulated Co was always presented as high temperature alpha-Co phase with fee structure, which frequently consists of twinned boundaries and stacking faults. Based on the experimental results, a possible growth mechanism of the CNTs encapsulated Co nanoclusters was proposed. Magnetic property measurements showed that the CNTs encapsulated cobalt nanoclusters possessed excellent magnetic properties.
Elaboration of h-Bn Sheathed β-Sic Nanocables
Authors: Saulig-Wenger K. , Cornu D. , Chassagneux F. , Miele P. , Epicier T.
Published: June 2019

h-BN sheathed β-SiC nanocables were synthesized under argon at 1200°C by the direct thermal treatment of a silicon powder mixed with turbostratic boron nitride. The structure and the chemical composition of these nanocables have been investigated by HRTEM, EDX and EELS. They have a diameter ranging from 10 to 80 nm. The core of these nanocomposites is composed of pure cubic silicon carbide and the outer layers have been shown to be hexagonal boron nitride planes, set in a parallel direction to the nanocables axis.
Fabrication of Field Emitter Arrays of Carbon Nanotubes Aligned on Patterned Substrates using Self-Assembly Monolayer
Authors: Lee Ok-Joo , Jeong Soo-Hwan , Lee Kun-Hong
Published: June 2019

Field emissions from the singlewalled carbon nanotubes (SWNTs) attached on various patterned substrates such as silicon wafer and polymer film, are reported. SWNTs were cut into sub-micron length by sonication in an acidic solution. The SWNT emitters were aligned on Au surface at room temperature by self-assembly monolayer technique. The field emission measurements in a silicon wafer and a polymer film showed that the turn-on fields were 2.8 V/ νm and 3.9 V/ νm at the emission current density of 10 μA/cm2, respectively. The current densities were 0.9 mA/cm2 and 1.6 mA/cm2 at 6.0 V/ νm. This room temperature process is suitable for the fabrication of flexible field emission devices with carbon nanotubes.
Field Emission Properties of Carbon Nanotubes Synthesized by High Temperature Arc Method and Low Temperature CVD Method
Authors: Lai Hong-Jen , Kung Sheng-Chin , Hsu Chih-Ming , Li Bean-Jon , Lin Ching-Cheng , Lin Chih. Jen.
Published: June 2019

The microstructure and field emission properties of multi walled carbon nanotubes (MWNTs) were investigated. The comparisons are made between MWNTs synthesized by high temperature arc methods and low temperature CVD methods. The results of the HRTEM image clearly exhibit characteristic features of a multi walled carbon nanotube. Raman spectrum shows a stronger peak at about 1580 cm-1 indicating the formation of a well-graphitized carbon nanotube. It also shows the high temperature arc process can produce MWNT that has perfect graphitic layer structure and high I(G)/I(D) ratio. The Ratio of G-line (sp2 bond) and D-line(sp3 bond) of these MWNTs are about 2.8 to 5.2. From the field emission measurement, the low onset field is about 1.4 to 2.4 V/ m, and can be attributed to highly sharp tips and high electric conductivity of MWNTs.
Yield of InxGa1-xAs Superlattices Under Bending and Nanoindentation
Authors: Lloyd Stephen J. , P'ng Ken M.Y. , Bushby Andy J. , Dunstan David J. , Clegg William J.
Published: June 2019

A series of InxGa1-xAs superlattices grown on InP substrates with differing coherency strains have been deformed by bending at 500°C and by nanoindentation at room temperature. The deformation was characterised by transmission electron microscopy through examination of thin sections machined in a focused ion beam microscope. The bent samples sheared along {111} planes, and the most highly strained samples partially relaxed through the formation of misfit dislocations. Under indentation the majority of the plastic strain in the multilayers is accommodated by twinning whereas no twins were observed under indents in the InP substrate. The overall dimensions of the plastic zone increased linearly with indent load.
Continuum Analysis of Cooperative Pit/Island Formation and Stability in SiGe on Si(100)
Authors: Singh N. , Elzey D.M.
Published: June 2019

Recent experimental work (J. Gray, R.Hull and J. Floro, App. Phys. Lett. Vol 81, No 13, 2002) has investigated the cooperative nucleation and growth of pits and islanding at pit edges in SiGe/Si(100) epitaxial films. The pits, which are observed to form under certain growth conditions, evolve along with the islands until a complete island wall is formed around the pit's periphery. Once formed the pit'island configuration exhibits a surprising stability, with no further lateral growth during continued deposition or annealing. The pits consists of low energy {501} facets (inverted {501} pyramid) and the islands surrounding the pit also exhibiting faceting. Elastic finite element analyses of these configurations were carried out to investigate the dependence of strain energy and surface stress on pit/island geometry. In particular, our results provide insight as to the mechanism responsible for the observed size stability of the pit/island structure once it has become fully developed. Surface stress gradients arising from the geometry are also found to be responsible for the observed initial island formation at the center of pit edges during growth.
Mechanical Properties Of P(S-co-Itana)/P(S-Co-Mana), P(S-co-Ssna)/P(S-co-Mana), And P(S-co-Itana)/P(S-co-Ssna) Ionomer Homoblends
Authors: Oh Sung-Hwa , Kim Joon-Seop , Yu Jeong-A , Shin Kwanwoo
Published: June 2019

Three different sets of styrene-based ionomer homoblends containing ca. 5 mol% of ionic repeat units, i.e. poly(styrene-co-sodium itaconate) [P(S-co-ITANa)]/ poly(styrene-co-sodium methacrylate) [P(S-co-MANa)] ionomer blends, sodium sulfonated polystyrene [P(S-co-SSNa)]/P(S-co-MANa) ionomer blends, and P(S-co-ITANa)/P(S-co-SSNa) ionomer blends, were prepared and their dynamic mechanical properties were investigated. It was observed that with increasing itaconate content in the blend of P(S-co-ITANa)/P(S-co-MANa) ionomers the multiplet of the P(S-co-MANa) ionomer disrupted initially very rapidly, and ionic modulus of the blend increased drastically. In the case of P(S-co-ITANa)/P(S-co-SSNa) ionomer blends, again, the ionic modulus increased significantly with increasing itaconate content. In these two ionomer blend systems, the itaconate, having two ionic groups per ionic repeat unit, influenced the properties of the blends more noticeably than the other two ionic units, containing only one ionic group per ionic repeat unit. In the blend system of P(S-co-SSNa)/P(S-co-MANa), as expected, the cluster loss tangent peak shifted to higher temperature, ionic modulus decreased, but the ionic plateau extended more with increasing the ratio of the P(S-co-SSNa) content. However, it should be mentioned that when the ion contents of the methacrylate and sulfonate ionomers increased to over 6 mol%, at which the cluster phase of the P(S-co-MANa) ionomers is known to become dominant, compared to the matrix phase, the three loss tangent peaks were observed, which implies that methacrylate-rich and sulfonaterich phases exist together. This might be due to the fact that a copolymerization effect becomes stronger; that is, with increasing ion content the role of ionic units in random copolymer ionomers becomes more important, compared to the role of host non-ionic units. As a concluding remark, the properties of these three ionomer blend systems depend on the degree of clustering, type of ionic groups, and the number of ionic groups per repeat unit.
Dynamics of Nanoparticle Chain Aggregates of Carbon Under Tension
Authors: Bandyopadhyaya Rajdip , Rong Weizhi , Suh Yong J. , Friedlander Sheldon K.
Published: June 2019

Carbon black in the form of nanoparticle chains is used as a reinforcing filler in elastomers. However, the dynamics of the filler particles under tension and their role in the improvement of the mechanical properties of rubber are not well understood. We have studied experimentally the dynamics of isolated nanoparticle chain aggregates (NCAs) of carbon made by laser ablation, and also that of carbon black embedded in a polymer film. In situ studies of stretching and contraction of such chains in the transmission electron microscope (TEM) were conducted under different maximum values of strain. Stretching causes initially folded NCA to reorganize into a straight, taut configuration. Further stretching leads to either plastic deformation and breakage (at 37.4% strain) or to a partial elastic behavior of the chain at small strains (e.g. 2.3% strain). For all cases the chains were very flexible under tension. Similar reorientation and stretching was observed for carbon black chains embedded in a polymer film. Such flexible and elastic nature of NCAs point towards a possible mechanism of reinforcement of rubber by carbon black fillers.
An in-situ TEM Nanoindenter System with 3-axis Inertial Positioner
Authors: Bobji M.S. , Ramanujan C.S. , Doole R.C. , Pethica J.B. , Inkson B.J.
Published: June 2019

To quantify the mechanical properties and deformation behaviour of sub-micron wires, an in-situ nanoindenter system is being developed for a TEM. The miniaturized displacement controlled nanoindenter fits inside a side entry specimen holder. For coarse positioning, a novel 3-axis inertial positioner has been developed. This positioner has a range of 5mm with a 300 nm resolution. The fine displacements are generated by means of a tube piezo and the force is measured using a fibre optic interferometer.
Nanomechanical Imaging Of Multi-Walled Carbon Nanotubes
Authors: Muthuswami Lata , Ajayan P. M. , Geer R. E.
Published: June 2019

Nanomechanical mapping of individual multi-walled carbon nanotubes (MWNTs) has been undertaken to investigate intra-tube variations of mechanical response. Ultrasonic force microscopy has been used to measure the relative axial and radial variations of contact stiffness of individual MWNTs synthesized using chemical vapor deposition (CVD) and arc-discharge (AD) techniques. For CVD-based MWNTs the contact stiffness of the tube was seen to vary strongly across volume defects (axial variation of the tube radius) and is assumed to result from the high crystalline defect density associated with such radial variations. These observations support recent experimental data of effective Young's modulus inferred from electrostatically-induced nanotube vibration amplitudes.
Silylation of Partially Aggregated Colloidal Silica Nanoparticles for Reinforcement in Silicone Elastomers
Authors: Chao Timothy C. , Bergstrom Debora F.
Published: June 2019

Aqueous suspensions of colloidal silicas are readily silylated with chlorosilanes in the presence of acid and isopropyl alcohol without aggregation of the silica particles. By using chlorosilanes, spherical nanoparticles with controlled functionality can be made and transferred to an organic phase to provide stable, water free suspensions. The hydrophobic colloidal silica particles readily disperse into silicone polymers. In order to provide mechanical reinforcement comparable to traditional fumed silicas, a high filler loading of ca. 60 wt % mono-dispersed colloidal silicas need to be used.

Recently a unique pearl necklaced-shaped colloidal silicas become commercially available. These nanoparticles are successfully silylated and they maintain the original structures as evidenced by transmission electron microscopy (TEM). They are compounded into silicone polymers at ca. 30 wt % and they provide excellent viscosities and mechanical properties, especially the tear strengths. In this paper, we present the silylation, characterization and mechanical properties of these partially aggregated colloidal silica nanoparticles in silicone elastomers.
Texture and Nano Mechanical Properties of YSZ Electrolyte Thin Films Prepared by CCVD and PLD
Authors: Xu Z. , Waters C. , Wang X. , Sudhir N. , Yarmolenko S. , Sankar J.
Published: June 2019

Composite thin films of yttria stabilized zirconia (YSZ) and alumina (Al2O3) have been synthesized using liquid fuel combustion chemical vapor deposition (CCVD) and pulsed laser deposition (PLD) in the NSF Center for Advanced Materials and Smart Structures (CAMSS) at North Carolina A&T State University. With the CCVD technique, addition of alumina was realized by adding the designated amount of aluminum-organic in the reagent solution; while with PLD, doping of alumina in YSZ was accomplished by alternative ablations of an YSZ target and an alumina target. Variations in morphology, surface roughness and nano-mechanical properties of the composite thin films of Al2O3/YSZ were characterized. Crystal size of the films processed by CCVD was much larger than that processed by PLD; surface roughness follows the similar tendency. Upon high-temperature annealing, crystals in the PLD processed thin films grew up to 300 nm. The effect of Al2O3 in YSZ thin films on their nano-mechanical properties was dependent on the film deposition techniques in our research. For the films deposited by CCVD, addition of Al2O3 improved the nano hardness and elastic modulus of YSZ thin films, while a decline was observed in the mechanical properties of the films deposited by PLD.
Aerosol Deposition Method (Adm) For Nano-Crystal Ceramics Coating Without Firing
Authors: Akedo Jun , Lebedev Maxim , Iwata Atsushi , Ogiso Hisato , Nakano Shizuka
Published: June 2019

Aerosol deposition method (ADM) for shock-consolidation of fine ceramics powder to form dense and hard layers is reported. Submicron ceramic particles were accelerated by gas flow in the nozzle up to velocity of several hundred m/s. During interaction with substrate, these particles formed thick (10 ∼ 100 μm), dense, uniform and hard ceramics layers. Experiments were fulfilled at room temperature. The results of fabrications, microstructure and mechanical properties of oxides (Al2O3; (Ni,Zn)Fe2O3; Pb(Zr0.52,Ti0.48)O3 and non-oxide (AlN; MgB2) materials are presented. Every layer has polycrystalline structure with nano-meter order scale.
Using Fluctuations To Locate The Surface Roughening Transition
Authors: Bentz Daniel N. , Jackson Kenneth A.
Published: June 2019

An analysis of the fluctuations of a {100} FCC interface has been used to locate the surface roughening transition in kinetic Monte Carlo simulations. These simulations were conducted using a spin 1/2 Ising model treatment of the solid-liquid interface. A temperature gradient was imposed on the simulation cell providing a restoring force to the interface. Fluctuations in the number of solid atoms in the system were measured using time correlations. The fluctuation dissipation theorem was employed to relate the characteristic times retrieved from the time correlation to the kinetic coeffcients of the system. A dramatic change was found in these characteristic times, which locates the surface roughening transition.
Structural Evolution and Acoustic Phonon Behavior in Crystalline PTFE Latex Films
Authors: Pierno M. , Casari C.S. , Bassi A. Li , Beghi M.G. , Piazza R. , Bottani C.E.
Published: June 2019

The structural evolution of polytetrafluoroethylene (PTFE) crystalline polymer latex films is studied at hundreds nanometer length scale by atomic force microscopy and Brillouin light scattering. In a controlled sintering process the transition is observed from the original particle distribution towards a ‘fibrillar’ structure of crystalline regions embedded in a disordered matrix. This transition is accompanied by a cross-over from localized acoustic excitations to propagating acoustic phonons, related to mesoscopic elastic properties. After sintering, a ‘mark’ of the original particulate structure persists, suggesting that filming of crystalline polymers may be analogous to sintering of ceramic powders. Films of crystalline polymers can thus be exploited as model systems to study the elasto-optical properties of granular and disordered media.
Geometrical Contribution to Yield Strength in Small Volumes
Authors: Dunstan D.J. , Bushby A.J.
Published: June 2019

Critical thickness theory was developed to account for the ability of thin epitaxial metal and semiconductor layers to support high misfit or coherency strain. The thermodynamic equilibrium theory is correct, and is well approximated by a theory based on geometrical arguments. The latter theory is readily extended to arbitrary misfit strain profiles including linearly graded layers, for which a surface layer free of misfit dislocations. This result applies as well to linear strain gradients introduced by deformation, in which case the misfit dislocations are known as geometrically necessary dislocations. We show that a consequence of this surface layer is that the apparent yield strength of the material increases in small structures such as thin wires in torsion. Under large plastic deformation, even if the material is perfectly plastic, critical thickness theory also predicts an apparent work-hardening. The predictions of critical thickness theory are in excellent agreement with experimental data in the literature.
Multiscale Modeling of Mechanical Response of Quantum Nanostructures
Authors: Tewary Vinod K. , Yang Bo
Published: June 2019

A multiscale Green's function method is described for modeling the mechanical response of quantum nanostructures in semiconductors. The method accounts for the discreteness of the lattice in and around the nanostructure, and uses the continuum Green's function to model extended defects such as free surfaces in the host solid. The method is applied to calculate the displacement field due to a Ge quantum dot in a semi-infinite Si lattice. Corresponding continuum values of the displacement field are also reported.
Dislocation Behavior During Deformation- Combining Experiments, Simulation and Modeling.
Authors: Robertson I.M. , Robach J. , Wirth B. , Arsenlis A. , Livermore Lawrence
Published: June 2019

In situ straining in the transmission electron microscope has been combined with molecular dynamics computer simulations to investigate the nature of the interaction of glissile dislocations with radiation-produced defects (loops, stacking-fault tetrahedra, and He bubbles), and to determine the mechanisms by which the dislocation loops and stacking-fault tetrahedra are annihilated and defect-free channels are created. The defect pinning strength depends on the defect and on the interaction geometry. The experiments and simulations show that a single interaction is not always sufficient to annihilate a dislocation loop or a stacking-fault tetrahedra and that the nature of the defect may be changed because of the interaction. The edge/screw character of the dislocation is also important as they have different efficiencies for annihilating a defect. The dislocations responsible for creating the defect-free channels are not the preexisting dislocations but originate from grain boundaries and other stress concentrators. Cross-slip of dislocations within the channels is important for clearing and widening the channel and can create new channels. Based on these observations a dispersed-barrier hardening model in which the influence of the radiation defects and dislocation density are combined. The resulting model predicts the observed behavior, including the apparent yield drop at high defect densities.
Inhomogeneous Distribution of Dislocation Density as Manifestation of Multiscale Structure in Tubes from Zr - Based Alloys
Authors: Perlovich Yuriy , Isaenkova Margarita
Published: June 2019

An X-ray method was developed to determine the dislocation density in metal materials as a distribution depending on the orientation of Burgers vector. The method includes registration of X-ray line profiles by each successive position of the sample in the course of diffractometric texture measurement using reflections of two orders, the following determination of coherent domain size and lattice distortion by means of the Warren-Averbach method for each orientation of reflecting planes, separate calculation of the density of c- and a-dislocations with all possible orientations of Burgers vector and presentation of results in the generalized pole figures. The method was used to determine the dislocation density in tubes of Zr-based alloys for nuclear industry. Obtained data show, that the dislocation density varies within very wide interval of several orders of magnitude depending on the grain orientation both in as-rolled and annealed tubes. Features of the dislocation distribution in tubes are closely related to their crystallographic texture.
Some Theoretical Aspects of the Grüneisen Coefficient for the Equation of State of Solids
Authors: Chaissé Francis , Heuzé Olivier
Published: June 2019

The aim of this study is to specify the Güneisen coefficient variation versus volume γ(V). First for isotropic solid, and in the anharmonic approximation we recall the various classical laws on γ(V). On the other hand, the shock wave physics have shown the experimental evidence of the linear relationship between shock velocity (U) versus jump of particle velocity (u) with some further consequences on γ(V) [cf. MRS Symp. Proc. vol 731 paper W-8.1 (Spring 2002)]. In this paper, we point out the failure of the γ(V) representation in the anharmonic approximation to reproduce the shock wave data U(u). Taking now into account the anharmonic effects in solids, we propound a new analysis of the γ(V) law which is well suited for the shock wave physics of solids.
Microdiffraction Experiments and Modeling for Analyzing Multiscale Dislocation Ensembles in Materials
Authors: Ice G.E. , Barabash R.I. , Pang J.
Published: June 2019

The intensity distribution of Laue diffraction is analyzed as a function of local misorientation. We show how unpaired dislocations alter the white beam Laue patterns for isolated dislocations, for dislocation walls, and for a combination of both. We consider the effect of different statistically and geometrically necessary dislocation densities on the intensity distribution along and perpendicular to the Laue streak. A 3D x-ray crystal microscope is used to analyze the complicated plastic-elastic field in a grain of a Ni polycrystalline sample during in-situ uniaxial pulling. A change of dislocation activity with depth is demonstrated. The dislocation slip systems and their densities are determined at various depths. The model parameters are used to simulate the whole Laue pattern including details about the contours for specific Laue spots; good agreement is found between simulated and experimental contours.
Electrochemistry of Tin in Borate Buffer Solutions: An in-situ Raman study.
Authors: Díaz Raül , Díez-Pérez Ismael , Grostiza Pau , Sanz Fausto , Joiret Susanne , Allongue Philippe
Published: June 2019

The electrochemical behavior of chemically polished polycrystalline tin is investigated in borate buffer solutions at pH=7.5 using in-situ Raman measurements. Experiments reveal the appearance of “luminescence” under continuum red laser light only for a narrow range of sample potentials within the anodic plateau. The phenomenon is discussed in view of the tin oxides formed on the surface, and correlated with the assignation of the oxido-reduction processes observed in the voltammograms.
Effect of Low Temperature Annealing on High Field Magnetoresistance and Hall effect in (Ga, Mn)As Dilute Magnetic Semiconductors
Authors: Ghosh K. , Arif Mohammad , Kehl T. , Patel R. J. , Mishra S. R. , Broerman J. G.
Published: June 2019

In this paper we report the effect of low temperature annealing on the high field magnetotransport properties of epitaxial thin films of (Ga, Mn)As Dilute Magnetic Semiconductor (DMS) with low concentration (1.5 %) of Mn doping, which results in a ferromagnetic insulator. Annealing at an optimal temperature enhances the conductivity, carrier concentration, and ferromagnetic transition temperature. The field dependence of magnetoresistance is different below and above the ferromagnetic transition temperature. An attempt is made to analyze the data using a theoretical model proposed by Kaminski and Das Sarma [1].
UV Raman Scattering Analysis of Indented and Machined 6H-SiC and β-Si3N4 Surfaces
Authors: Walter Jennifer J.H. , Liang Mengning , Chen Xiang-Bai , Jang Jae-il , Bergman Leah , Patten John A. , Pharr George M. , Nemanich Robert J.
Published: June 2019

UV Raman scattering is employed as a nondestructive structure sensitive probe to investigate the vibrational properties of the wide bandgap, machined and indented surfaces of 6H-SiC and β-Si3N4. In these materials, the short absorption depth of UV light allows for accurate probing of the surface, and the transparency to visible light allows for analysis of the bulk material. The study on 6H-SiC (0001) included measurements of indentations, and of machined circular (0001) wafer edges. The indentation analysis indicates the response of the material to localized pressures. Machined 6H-SiC wafer edges and machined β-Si3N4 surfaces indicate a ductile response and ductile material removal for machining at cutting depths on a nm and μm scale. Raman scattering measurements of the ductile surfaces and ductile material removed indicate residual structure changes. The residual surface structures could indicate that a high-pressure phase transformation is the origin of a ductile response on machined brittle materials.
Highly and Rapidly Stabilized Protocrystalline Silicon Multilayer Solar Cells
Authors: Lim Koeng Su , Kwak Joong Hwan , Kwon Seong Won , Myong Seung Yeop
Published: June 2019

We have developed highly stabilized (p-i-n)-type protocrystalline silicon (pc-Si:H) multilayer solar cells. However, the source of the superior light-induced stability of the pc-Si:H multilayer absorbers compared to conventional amorphous silicon (a-Si:H) absorbers remains unclear. Photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy measured at room temperature produce strong evidence that nano-sized silicon grains embedded in regularly arranged highly H2-diluted sublayers suppress the photocreation of dangling bonds. To achieve a high conversion efficiency, we applied a double-layer p-type amorphous siliconcarbon alloy (p-a-Si1-xCx:H) structure to the pc-Si:H multilayer solar cells. The less pronounced initial short wavelength quantum efficiency variation as a function of bias voltage, and the wide overlap of dark current - voltage (JD-V) and short-circuit current - open-circuit voltage (Jsc-Voc) characteristics prove that the double p-a-Si1-xCx:H layer structure successfully reduces recombination at the p/i interface. Thus, we achieved a highly stabilized efficiency of 9.0 % without any back reflector.
Multiple-Trapping Model with Meyer-Neldel Effect and Field-Dependent Effects: Time-Of-Flight Simulations for a-Si:H
Authors: Maassen Jesse , Yelon Arthur , Hamel Louis-André , Chen Wen Chao
Published: June 2019

We have included both the Meyer-Neldel rule and field assisted detrapping in the multiple-trapping model, assuming exponential band tails of localized states. Monte Carlo simulations with fixed parameters provide transient currents and comparison of calculated and measured mobility, μ(T,F), and pre-transit dispersion parameter, α1(T,F), which are presented for temperatures ranging from 25 K to 333 K and fields from 20 kV/cm to 400 kV/cm. We observe that the values of μ1(T,F) and α(T,F) are improved with this combined model. Although this model provides satisfactory results for carrier transport for all temperature and field, differences in experimental data causes deviation of simulated results from experiment.
AFM Morphology Study of Si1-Y GeY:H Films Deposited by LF PE CVD from Silane-Germane with Different Dilution
Authors: Sanchez L. , Kosarev A. , Torres A. , Felter T. , Ilinskij A.
Published: June 2019

The morphology of Si1-Y GeY:H films in the range of Y=0.23 to 0.9 has been studied by AFM. The films were deposited by Low Frequency (LF) PE CVD at substrate temperature Ts=300 C and discharge frequency f=110 kHz from silane+germane mixture with and without, Ar and H2 dilution. The films were deposited on silicon and glass substrates. AFM images were taken and analyzed for 2x2 μm2 area. All the images demonstrated “grain” like structure, which was characterized by the height distribution function F(H) average roughness , standard height deviation Rq, lateral correlation length Lc, area distribution function F(s), mean grain area
, diameter distribution function F(d), and mean grain diameter . The roughness  of the films monotonically increases with Y for all dilutions, but more significantly in the films deposited without dilution. Lc continuously grows with Y in the films deposited without dilution, while more complex behavior of Lc(Y) is observed in the films deposited with H- or Ar dilution. The sharpness of F(H) characterized by curtosis γ depends on dilution, and the sharpest F(H) are for the films deposited with Ar ( γ=5.30,Y=0.23) and without dilution (γ=4.3, Y=0.45). Isothermal annealing caused an increase of , Lc in the films deposited with H- and Ar dilutions, while in the films prepared without dilution the behavior was more complex, depending on the substrates. After the annealing a significant sharpening of the height distributions, F(H), was observed in the films deposited with H dilution or without dilution.
Optical Properties of Amorphous Silicon-Yttrium Films
Authors: N. Shmyryeva Alexandra , V. Semikina Tetyana
Published: June 2019

This paper presents and discusses the results of measuring IR reflection and ellipsometric parameters, optical microscopy and AFM the mixed phase of amorphous Si:Y films with microcrystalline inclusions. These films were obtained by electron-beam evaporation of siliconyttrium alloys with different Y concentration (5-30 %) at two substrate temperatures (370 and 620 °C).
Fabrication of Nano-Crystalline Porous Silicon on Si Substrates by a Plasma Enhanced Hydrogenation Technique
Authors: Abdi Y. , Hashemi P. , Karbassian F. , Nayeri F.D. , Behnam A. , Mohajerzadeh S. , Koohsorhki J. , Robertson M.D. , Arzi E.
Published: June 2019

A novel plasma hydrogenation method for the fabrication of nano-crystalline structures of silicon as well as the photoluminescence and structural properties of these porous structures is presented. We have observed that the hydrogenation process followed by an annealing treatment results in the formation of nano-crystalline silicon structures where increased temperatures during hydrogenation reduces the grain size. Furthermore, by increasing the time of the hydrogenation process, the density of the silicon grains is increased.

Photoluminescence (PL) spectroscopy demonstrated the presence of a direct gap in the visible light range where materials with a smaller grain size emitted light at lower wavelengths, and a higher density of grains resulted in higher amplitudes in the PL spectrum. TEM and SEM characterization of these samples and the structure-emission relationship are also presented.
Nanocrystalline Si Films and Devices Produced Using Chemical Annealing with Helium
Authors: Wang Nanlin , Dalal Vikram L.
Published: June 2019

We report on growth of nanocrystalline Si:H films and devices using a layer-by-layer growth technique, where the growth of a thin amorphous layer by PECVD is followed by chemical annealing in a Helium plasma. The films and devices were grown using a remote, low pressure ECR plasma process. It was found that the structure of the films grown using the layerby-layer technique depended critically upon whether the annealing was done with hydrogen or helium, and the time taken to do the annealing. When the annealing was done in a hydrogen plasma, the films remained amorphous; in contrast, when the annealing was done in helium, and the annealing time was increased to 20 seconds from 10 seconds, the films became crystalline. The crystallinity of the films was confirmed using Raman spectroscopy and x-ray diffraction. The result obtained here shows that it is not necessary to have a high hydrogen dilution to obtain nanocrystalline films. Rather, the amount of hydrogen already present in an amorphous film is enough to cause crystallization, provided that enough ion flux and perhaps energy are available for converting the amorphous structure to a crystalline structure. Proof - of - concept p+nn+ junction devices were fabricated in these chemically annealed materials, and they showed classical nanocrystalline Si solar cell type behavior.
Ultra-Shallow Junction Formation by a Non-Melting Process; Double-Pulsed Green Laser Annealing
Authors: Kudo Toshio , Sakuragi Susumu , Yamazaki Kazunori
Published: June 2019

In order to investigate the possibility of nanosecond activation in the non-melting state, we adopted the method of double-pulsed green laser annealing (DPSS), controlling effectively the combined pulse width with two pulsed lasers (pulse duration: ˜100ns, frequency: 1kHz). We investigated the formation of ultra-shallow junctions (USJ) less than 10nm in spite of the deep penetration depth of the green wavelength in crystalline Si (˜1000nm). In order to limit the depth of B implant, a Ge pre-amorphization implant was performed at an energy of 3keV to a dose of 3E+14/cm2. After the pre-amorphization implant, a B implant was performed at 0.2kev and doses of 5E+14/cm2 and 1E+15/cm2. The implanted B dopants remain within the pre-amorphized Si layer. The double-pulsed laser irradiation was performed with a homogenized line beam of 0.1mm x 17mm, scanning a sample stage at a constant velocity of 10mm/s, that is, at an overlap ratio of 90%. The non-melting state was found to be in the pulse energy density range of E ≤ 780mJ/cm2 at a delay time of 300ns. Overcoming the issues of the short annealing time (˜<1μs) and the deep penetration depth (˜1000nm), we succeeded in the ultra-shallow junction formation beyond the 45nm CMOS node: maximum junction depth of 6nm, minimum sheet resistance of 0.65kohm/sq at a B dose of 1E+15/cm2, an abruptness of 1.4nm/dec.
Low Temperature Metal-Free Fabrication of polycrystalline Si and Ge TFTs by PECVD Hydrogenation
Authors: Hashemi Pouya , Derakhshandeh Jaber , Hekmatshoar Bahman , Mohajerzadeh Shamsoddin , Abdi Yaser , Robertson Michael D.
Published: June 2019

Poly-crystalline Si and Ge layers were grown at low temperatures on glass substrates by successive hydrogenation and annealing steps, with no need to any metal incorporation. Hydrogenation is performed in an RF-PECVD apparatus with different powers of hydrogen plasma and the annealing step is carried out in the same system in N2 ambient. This leads to formation of granular Si and Ge structures with average grain size of less than 100nm at temperatures as low as 250°C and 150°C, respectively. The effect of hydrogen plasma power at various temperatures on the crystallinity of the layers has been studied by SEM and TEM analyzes. Successive hydrogenation and annealing at respective temperatures of 150°C and 200°C for Ge layer and 300°C for Si layer would result in a device-quality polycrystalline Ge and Si layers which have been employed for fabrication of thin-film transistors. These TFTs show the mobility of 80cm2/Vs and 4cm2/Vs and ON/OFF ratio of more than 103 and 5×104 for Ge and Si, indicating the feasibility of this technique for applications in large-area electronics.
Active Pixel TFT Arrays for Digital Fluoroscopy in a-Si:H Technology
Authors: Lai Jackson , Safavian Nader , Nathan Arokia , Rowlands John A.
Published: June 2019

Major development challenges in application of hydrogenated amorphous silicon (a-Si:H) technology to large area digital X-ray imaging and technological attributes such as low temperature deposition and high uniformity over large area evolve around dynamic imaging modalities such as fluoroscopy, which demands both high speed readout and signal amplification capabilities in addition to long term device stability. This work reports on initial results of a variety of TFT active pixel sensor (APS) structures in a-Si:H technology, each demonstrating unique capabilities such as enhancements in signal gain, TFT threshold voltage immunity, and real-time high speed readout.
The Role of SiH3 Diffusion in Determining the Surface Smoothness of Plasma-Deposited Amorphous Si Thin Films: An Atomic-Scale Analysis
Authors: Valipa Mayur S. , Bakos Tamas , Aydil Eray S. , Maroudas Dimitrios
Published: June 2019

Device-quality hydrogenated amorphous silicon (a-Si:H) thin films grown under conditions where the SiH3 radical is the dominant deposition precursor are remarkably smooth, as the SiH3 radical is very mobile and fills surface valleys during its diffusion on the a-Si:H surface. In this paper, we analyze atomic-scale mechanisms of SiH3 diffusion on a-Si:H surfaces based on molecular-dynamics simulations of SiH3 radical impingement on surfaces of a-Si:H films. The computed average activation barrier for radical diffusion on a-Si:H is 0.16 eV. This low barrier is due to the weak adsorption of the radical onto the a-Si:H surface and its migration predominantly through overcoordination defects; this is consistent with our density functional theory calculations on crystalline Si surfaces. The diffusing SiH3 radical incorporates preferentially into valleys on the a-Si:H surface when it transfers an H atom and forms a Si-Si backbond, even in the absence of dangling bonds.
Wiring and introduction of single silicon nanocrystals into multi-walled carbon nanotubes
Authors: Švrček Vladimir , Normand Francois Le , Ersen Ovidui , Pham-Huu Coung , Begin Dominique , Louis Benoit , Ledoux Marc-Jaques
Published: June 2019

For a long time the application of silicon technology for optoelectronics has been limited by the extremely poor generation of light by bulk silicon. However, the properties of Si were found to depend on its structure at a nanometric scale and bright photoluminescence from silicon nanocrystals (Si-nc) was discovered. In this work, the results obtained for the mechanical connecting of single Si-nc by two independent techniques are presented. First, the room temperature approach of connecting and introducing Si-nc embedded in colloidal suspensions by capillary forces within multi-walled carbon nanotubes (MWCNTs) and second, the direct growth of MWCNTs on single Si-nc coated with iron catalyst are described.
Correlation of In and Ex Situ Stress to Microstructures during Al-Induced Crystallization of PECVD Amorphous Silicon
Authors: Ray S. , Lian Y.G. , Sriram V. , Tucker D. J. , Pan G. Z.
Published: June 2019

We studied the correlation of in and ex situ stress to microstructures during Al-induced crystallization for structures of Al on top (AOT) and Al on bottom (AOB) of amorphous Si (a-Si) on 3000 Å SiO2 coated on Si wafers and found that a-Si deposited on PECVD SiO2 and Al increases the stress compressively, and Al deposited on PECVD SiO2 and on a-Si decreases the stress tensilely. In addition, the stress of AOB structures is in general less than that of AOT structures. Correlation of stress to microstructures indicated that the difference in microstructures between AOT and AOB results from the nature of the layer structures themselves. By using modified Stoney's equation, the lower stress of AOB structures than AOT could be explained with existence of oxide between a-Si and Al for both AOT and AOB structures.
Electronic Properties of Improved Amorphous Silicon-Germanium Alloys Deposited by a Low Temperature Hot Wire Chemical Vapor Deposition Process
Authors: Datta Shouvik , Cohen J. David , Xu Yueqin , Mahan A. H.
Published: June 2019

We report novel material properties of a series of a-Si,Ge:H alloys grown by hot-wire chemical vapor deposition under low filament temperature (˜1800°C) and low substrate temperature (˜200-300°C). These alloys exhibit significantly improved electronic properties including low defect densities and sharp band tails (Urbach energies ≤ 45meV even for Ge fractions as high as 47at.%). On the other hand, comparisons of the transient photocapacitance and transient photocurrent spectra do not indicate very efficient hole collection in these materials. We found two distinct regimes of light-induced degradation in the alloy sample with 29at.% Ge fraction, possibly corresponding to the light induced increase of Ge and Si dangling bonds, respectively.
Experimental Study of Silane Plasma Nanoparticle Formation in Amorphous Silicon Thin Films
Authors: Thompson S. , Perrey C. R. , Belich T. J. , Blackwell C. , Carter C. B. , Kakalios J. , Kortshagen U.
Published: June 2019

RF glow discharge deposited hydrogenated amorphous silicon films containing silicon nanocrystalline inclusions (a/nc-Si:H) films are investigated as a function of a thermal gradient applied across the silane plasma during film growth. The a/nc-Si:H films are synthesized from hydrogen-diluted silane plasmas when a capacitively-coupled plasma enhanced chemical vapor deposition reactor is operated at high gas chamber pressures. Plasma diagnostics and transmission electron microscopy image analysis of films deposited with and without a thermal gradient suggest that nanoparticle formation occurs within the plasma, rather than resulting from solid-state nucleation at the growing film surface.
Hot-mesh Chemical Vapor Deposition for 3C-SiC Growth on Si and SiO2
Authors: Yasui Kanji , Eto Jyunpei , Narita Yuzuru , Takata Masasuke , Akahane Tadashi
Published: June 2019

The crystal growth of SiC films on (100) Si and thermally oxidized Si (SiO2/Si) substrates by hot-mesh chemical vapor deposition (HMCVD) using monomethylsilane as a source gas was investigated. A mesh structure of hot tungsten (W) wire was used as a catalyzer. At substrate temperatures above 750°C and at a mesh temperature of 1600°C, 3C-SiC crystal was epitaxially grown on (100) Si substrates. From the X-ray rocking curve spectra of the (311) peak, SiC was also epitaxially grown in the substrate plane. On the basis of the X-ray diffraction (XRD) measurements, on the other hand, the growth of (100)-oriented 3C-SiC films on SiO2/Si substrates was determined to be achieved at substrate temperatures of 750-800°C, while polycrystalline SiC films, at substrate temperatures above 850°C. From the dependence of growth rate on substrate temperature and W-mesh temperature, the growth mechanism of SiC crystal by HMCVD was discussed.
Study of the Oxidation of Polycrystalline SiGe: Formation of Ge Nanocrystals and their Related Luminescence
Authors: Prieto A. C. , Avella M. , Jiménez J. , Rodríguez A. , Sangrador J. , Rodríguez T. , Kling A.
Published: June 2019

Polycrystalline SiGe layers have been oxidized in either dry or wet atmospheres. The evolution of the growing oxides and the SiGe layer during the oxidation processes have been characterized using Raman spectroscopy, X-ray diffraction, Rutherford backscattering and Fourier transform infrared spectroscopy. Formation of Ge nanocrystals has been observed for both oxidation atmospheres. Violet luminescence emission has been observed and its relation to the oxidation processes has been studied. The luminescence is unambiguously related to the presence of these Ge nanocrystals. Since it does not exhibit quantum confinement, it must be related to defects linked to the nanocrystals.
Fabrication of One-dimensional Silicon Nano-wires Based on Proximity Effects of Electron-beam Lithography
Authors: Hu S. F. , Sung C. L.
Published: June 2019

One-dimensional silicon nanowire structures have been successfully made by using the proximity and accumulation effects of electron-beam (e-beam) lithography. Wire structures are fabricated in a thin poly silicon layer on a silicon substrate with a 400 nm buried SiO2. Measurements of the current-voltage characteristics at various temperatures from 4 K up to 300 K show significant nonlinearities and single-electron effect behavior. The blockade size is significantly affected by thermal effects, oscillations of the blockade, and the conductivity dependence on the gate potential.