bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atomic and Electronic Structure of Interfaces at Sic Studied by Indirect Super Hrtem and Electron Spectroscopyn Imaging
Authors: Yan J. Y. , Ichinose Hideki , Chen Fu-Rong , Kai J. J. , Takuma Eriko 
Published: June 2019

AbstractObtaining electronic and atomic structure of material simultaneously is very important for developing the nano-technology. In this paper, we demonstrate that atomic and electronic structure of an interface can be extracted with combination of Gerchberg-Saxton indirect microscopy and electron spectroscopy imaging (ESI) technique. Basically, Gerchberg-Saxton algorithm includes two projections. Projection in the real space is a maximum entropy (ME) de-convolution process and in reciprocal space is an amplitude substitution process. It has been shown that Gerchberg-Saxton algorithm can extend the structural resolution to near 0.1nm. An application case of Gerchberg-Saxton algorithm to solve the atomic structure for 3C-polytypic SiC boundary is shown.ESI spectrum processed by FFT interpolation, maximum entropy de-convolution and wavelet transformation allow us to extract 2-dimensional map of the sp2/sp3 with a sub-nanometer resolution. Grain boundary and interface at SiC are good candidates for this study, since the bond distance of Si-C is slightly less than 0.1nm which is not routinely resolvable using a FEG TEM and Si-L (99eV) and C-K-edges (283 eV) locate in a reasonable energy range. The resultant electronic structure can be compared with that calculated using WIEN97. An example of quantitative analysis on 2-dimensional sp3/sp2 map deduced from the C K-edge of ESI spectra acquired from 6H-SiC is given.
Green's Function Method for Calculation of Strain Field Due to a Quantum Dot in a Semi-Infinite Anisotropic Solid
Authors: Tewary V.K. 
Published: June 2019

AbstractA computationally convenient Green's function method is described for calculation of strain characteristics of quantum dots in an anisotropic semi- infinite solid containing a free surface. Semi-analytic expressions are derived for the strain field due to a quantum dot, strain energy of a quantum dot, and strain- field interaction between 2 quantum dots. Numerical results are presented for the strain field due to a quantum dot in GaAs. It is shown that the effect of the free surface, which has been neglected in earlier calculations using Green's function methods, is quite significant.
Chemical Structure Analysis of a Σ 9 Grain Boundary in α-SiC by Arhvtem
Authors: Takuma Eriko , Ichinose Hideki 
Published: June 2019

AbstractGrain boundary chemical structure of high purity α silicon carbide was investigated by an atomic resolution high voltage transmission electron microscope (ARHVTEM). Each of a ‘darker’ spots and each of the ‘brighter’ spots in the image have been identified to be silicon (Si) and carbon (C). Two (0001)/(1107) Σ 9 CSL grain boundaries were observed. One boundary showed a rigid body translation of 1/3 <1100> to the component crystals and the other did not. The unit period of the boundary was determined to 2.26 nm along >1120<. Two 6-membered, four 5-membered and 7-membered rings build up the boundary. Each ring consists of three C-C pairs, one Si-Si pair and non-paired Si atoms. In the case without the rigid body translation the number of lone Si atoms are four and only two Si atoms were determined in the other case. The observed structures suggest that the chemical structure of a grain boundary dominantly influences the grain boundary energy.
Ultraviolet Luminescence Emitted From ZnO Nanostructural Films by KrF Pulsed Laser Deposition
Authors: Ebihara Kenji , Ohshima Tamiko , Ikegami Tomoaki , Thareja Raj K. 
Published: June 2019

AbstractZinc Oxide (ZnO) thin films have been deposited on silicon (100), quartz glass, sapphire (0001), and glass substrates by pulsed laser deposition over a range of process conditions such as versus ambient oxygen gas pressure and substrate temperature. Photoluminescence measurements have been carried out to characterize ZnO thin films for optical device applications. We have also studied the influence of the process conditions on crystal structure and morphology of the grown films. Ultraviolet luminescence near the band gap at 3.25 eV was obtained from the optical pumped grown films. And ZnO thin films deposited on sapphire single crystal substrates exhibited strong stimulated emission around 3.12 eV with increasing pumping energy. ZnO thin films deposited at ambient oxygen gas pressure of 5 mTorr and a substrate temperature of 550 °C were predominantly c-axis oriented regardless of substrate material. The crystallite size of 22.7-49.8 nm was estimated using Scherrer's formula. AFM images of films grown on sapphire substrates display hexagonally shaped grains at various sizes.
Novel Nanosized Patterning Techniques Using An Electropulsed Scanning Probe Microscope
Authors: Melo L. V. , Brogueira P. 
Published: June 2019

AbstractScanning Probe Microscopes (SPM) have been used to change surfaces at nanometer scales. We report the deposition of user defined patterns in a controlled manner using an electropulsed SPM. The patterns were fabricated by applying -12 V electrical pulses in the 10 to 40 Hz range between a commercial CoCr conductive tip and a crystalline n-doped Si wafer. The tip damage during deposition is negligible as measurements on the same surface region before and after deposition show no detectable differences. Immediately after deposition the same tip is used for measuring the fabricated patterns. Applying one isolated electrical pulse results in a pixel with a typical size of the order of 30 nm. By combining the scanning ability of the SPM with the atmospheric deposition induced by electrical pulses on the tip, patterns can be fabricated. For example, by applying electrical pulses during a 25 nm x 800 nm tip scan in AFM tapping mode, at 40 Hz, lines with 65 nm width by 828 nm length were obtained (in good agreement with the expected dimensions of 55 nm x 830 nm derived from the pixel size and the scan range). The height of the deposited patterns is of the order of 2 to 3 nm, and was found to increase with the density of scan lines. The RMS roughness of the deposited material is shown to be strongly dependent on the electrical pulse frequency. The smoother pattern surface results from the 40 Hz pulse frequency. No deposition was observed at higher frequencies.
Fabrication of Periodic Arrays of Nanoscale Square Helices
Authors: Jensen Martin O. , Kennedy Scott R. , Brett Michael J. 
Published: June 2019

AbstractWe demonstrate fabrication of periodic arrays of nanometre scale square helices, with potential applications in three-dimensional photonic bandgap (PBG) materials. Processing is performed using a thin film deposition method known as Glancing Angle Deposition (GLAD). Through advanced substrate motion, this technique allows for controlled growth of square helices in a variety of inorganic materials. Organization of the helices into periodic twodimensional geometries is achieved by prepatterning the substrate surface using electron beam lithography. The regular turns of the helices yield periodicity in the third dimension, perpendicular to the substrate. We present studies of tetragonal and trigonal arrays of silicon helices, with lattice constants as low as 300 nm. By deliberately adding or leaving out seeds in the substrate pattern, we have succeeded in engineering line defects. Our periodic nanoscale structure closely matches an ideal photonic band gap architecture, as recently proposed by Toader and John. While our fabrication technique is simpler than most suggested PBG schemes, it is highly versatile. A wide range of materials can be used for GLAD, manipulation of lattice constant and helix pitch ensures optical tunability, and the GLAD films are robust to micromachining.
Mixed Abrasive CMP: A Study on Metal and Dielectric Films
Authors: Jindal Anurag , Hegde Sharath , Babu S.V. 
Published: June 2019

AbstractMixed abrasive slurries (MAS) containing alumina/silica and alumina/ceria abrasives were evaluated for CMP of metal and dielectric films, respectively. MAS with 0.5wt% calcined alumina and 2.5wt% silica (fumed and colloidal) abrasives were highly selective to tantalum polishing over copper and oxide. Similarly, MAS containing 1.5wt% calcined alumina and 3wt% colloidal ceria particles offered a polish rate selectivity between silicon dioxide and silicon nitride films of more than 30, without any additives, without compromising finished surface quality. This improved performance appears to be a result of modified surface morphology as well as synergistic interactions between the chemical activity of silica or ceria and the hardness of the alumina.
Photoelectron Spectroscopy Measurements of the Valence Band Structures of C60 Thin Films on Single Crystal Silicon and Polycrystalline Copper
Authors: Ha B. , Rhee J. H. , Li Y. , Singh D. , Sharma S. C. 
Published: June 2019

ABSTRACTWe have used photoelectron spectroscopy to study possible modifications in the electronic valence band structures of thin films of C60 due to their deposition on single crystal silicon and polycrystalline copper. The C60 thin films were deposited by thermal evaporation under high vacuum and further characterized by using Raman spectroscopy. We observe significant differences in the valence band structures of C60 thin films deposited on these substrates and attribute them to interactions at the interface.
Influence of Filament and Substrate Temperatures on Structural and Optoelectronic Properties of Narrow Gap a-SiGe:H Alloys Deposited by Hot-Wire CVD
Authors: Xu Yueqin , Nelson Brent P. , Williamson D.L. , Gedvilas Lynn M. , Reedy Robert C. 
Published: June 2019

AbstractWe have found that narrow-bandgap—1.25 < Tauc Gap < 1.50 eV—amorphous silicon germanium (a-SiGe:H) alloys grown by hot-wire chemical vapor deposition (hot-wire CVD) can be improved by lowering both substrate and filament temperatures. We systematically study films deposited using a one-tungsten filament, decreasing filament temperature (Tf) from our standard temperature of 2150° down to 1750°C, and fixing all other deposition parameters. By decreasing Tfat the fixed substrate temperature (Ts) of 180°C, the Ge-H bonding increases, whereas the Si-H2bonding is eliminated. Films with higher Ge-H bonding and less Si-H2have improved photoconductivity. For the series of films deposited using the same germane gas fraction at 35%, the energy where the optical absorption is 1x104(E04) drops from 1.54 to 1.41 eV with decreasing Tf. This is mainly due to the combination of an increasing Ge solid fraction (x) in the film, and an improved homogeneity and compactness due to significant reduction of microvoids, which was confirmed by small angle X-ray scattering (SAXS). We also studied a series of films grown by decreasing the Tsfrom our previous standard temperature of 350°C down to 125°C, fixing all other deposition parameters including Tfat 1800°C. By decreasing Ts, both the total hydrogen content (CH) and the Ge-H bonding increased, but the Si-H2bonding is not measurable in the Tsrange of 180°-300°C. The E04 increases from 1.40 to 1.51 eV as Tsdecreased from 350° to 125°C, mainly due to the increased total hydrogen content (CH). At the same time, the photo-to-dark conductivity ratio increases almost three orders of magnitude over this range of Ts.
Numerical Studies Of The Dynamics Of Silicon: Relaxation, Nucleation And Energy Landscape
Authors: Mousseau Normand , Beaucage Philippe , Valiquette Francis 
Published: June 2019

AbstractUsing various simulation techniques, such as molecular dynamics and the activation-relaxation technique, we are slowly developing a consistent picture of the dynamical properties of amorphous silicon. For example, results of an extensive search for the activated events surrounding a single minimum, in a well-relaxed model represented by a modified Stillinger-Weber potential, confirm that barrier height at the transition point, for activated mechanisms, is determined essentially by the binding energy of a single bond and not the details of the mechanism. We will discuss these results in some detail as well as recent simulations of nucleation in liquid and amorphous silicon.
Stress Effects on Nanocrystal Formation by Ni-Induced Crystallization of Amorphous Si
Authors: Liu Yaocheng , Deal Michael D. , Sultana Mahmooda , Plummer James D. 
Published: June 2019

AbstractMetal-induced crystallization (MIC) of amorphous Si is gaining increased interest because of its potential use for low-temperature fabrication of integrated circuits. In this work, the MIC technique was used to make Si nanocrystals and the effects of stress on the crystallization were studied. Amorphous Si films were deposited onto the Si substrate with thermal oxides on top by low-pressure chemical vapor deposition (LPCVD) and then patterned into nanoscale pillars by electron beam lithography and reactive ion etching. A conformal low-temperature oxide (LTO) layer was deposited to cover the pillars, followed by an anisotropic etch back to form a spacer, leaving only the top surface of the pillars exposed to the 5 nm Ni sputtering deposition afterwards. An HF dip was used to partially remove the LTO spacers on the pillars, leading to different LTO thicknesses on different samples. These samples were then annealed to crystallize the amorphous Si pillars, forming Si nanocrystals. Transmission electron microscope (TEM) observations after anneal found a clear dependence of the crystallization rate on the pillar size as well as the LTO thickness. The crystallization rate was lower for pillars with thicker LTO spacers, while for the same LTO thickness the crystallization rate was lower for pillars with narrower width. A model based on the stress in the pillars is proposed to explain this dependence. This model suggests some methods to control the nickel-induced crystallization process and achieve higher quality Si nanocrystals.
Formation of Large, Orientation-Controlled, Nearly Single Crystalline Si Thin Films on SiO2 Using Contact Printing of Rolled and Annealed Nickel Tapes
Authors: Huh Hwang , Shin Jung H. 
Published: June 2019

AbstractAmorphous silicon (a-Si) films prepared on oxidized silicon wafer were crystallized to a highly textured form using contact printing of rolled and annealed nickel tapes. Crystallization was achieved by first annealing the a-Si film in contact with patterned Ni tape at 600°C for 20 min in a flowing forming gas (90 % N2, 10 % H2) environment, then removing the Ni tape and further annealing the a-Si film in vacuum for2hrsat600°C. An array of crystalline regions with diameters of up to 20 μm could be formed. Electron microscopy indicates that the regions are essentially single-crystalline except for the presence of twins and/or type A-B formations, and that all regions have the same orientation in all 3 directions even when separated by more than hundreds of microns. High resolution TEM analysis shows that formation of such orientation-controlled, nearly single crystalline regions is due to formation of nearly single crystalline NiSi2 under the point of contact, which then acts as the template for silicide-induced lateral crystallization. Furthermore, the orientation relationship between Si grains and Ni tape is observed to be Si (110) || Ni (001)
Scattering Rings in Birefringent Porous Silicon
Authors: Oton Claudio J. , Gaburro Zeno , Ghulinyan Mher , Daldosso Nicola , Pancheri Lucio , Bettotti Paolo , Negro Luca Dal , Pavesi Lorenzo 
Published: June 2019

AbstractWe report the observation of strongly anisotropic scattering of laser light at oblique incidence on (100)-oriented porous silicon layers. We performed angle-resolved light scattering measurements and three concentric rings were observed. Modeling porous silicon by means of nanometric columnar air pores and an effective anisotropic uniaxial dielectric constant explains the observed phenomenon, and besides, the observation of the angle aperture of these rings allows a direct measurement of relative birefringence. We finally study the changes of optical anisotropy after different modifications of the structure.
Direct Electrical Characterization of Metal Induced Lateral Crystallization Regions by Spreading Resistance Probe Measurements
Authors: Myasnikov Alexandre M. , Poon Vincent M.C. , Leung Vincent T.C. , Chan Mansun , Cheng Lawrence C.F. 
Published: June 2019

AbstractMaterial characterization of metal induced lateral crystallization (MILC) process of amorphous silicon (a-Si) has been performed by using the spreading resistance probe (SRP) measurements. It was found that carrier mobility in boron ion implanted layer, formed in MILC region, is up to 65 % in comparison with mobility in boron ion implanted layer, formed in single crystalline silicon. It was also observed in this work that prolongation of MILC process from 1 hour to 2 hours had induced the increasing of mobility from 24 cm2/Vs to 34 cm2/Vs.
Laser Interference Structuring of a-GeN for the Production of Optical Diffraction Gratings
Authors: Mulato M. , Zanatta A. R. , Toet D. , Chambouleyron I. E. 
Published: June 2019

AbstractIn this work, we study the pulsed laser crystallization of hydrogen-free amorphous germanium-nitrogen alloys (a-GeN). We discuss the role of nitrogen during phase transitions and the possible application of the resulting structure as an optical diffraction grating. The crystallized region results of pure microcrystalline germanium (μc-Ge). An indication that Ge-N bonds have broken and nitrogen outdiffused of the film is obtained from infrared spectroscopy and confirmed by Raman spectra. A pattern of alternating a-GeN and μc-Ge lines with a period of about 4 μm acts as an optical diffraction grating due to the difference in optical properties between the two materials, and the three dimensional surface profile, caused by N2 effusion, that is formed on the sample.
Performance of Thin-Film Silicon MEMS Resonators in Vacuum
Authors: Gaspar J. , Chu V. , Conde J. P. 
Published: June 2019

AbstractThis paper reports on the fabrication and characterization of microelectromechanical bridge resonators on glass substrates using thin-film technology and surface micromachining. All the processing steps are performed at temperatures below 110°C. The microbridges consist of either a single layer of heavily doped n-type amorphous silicon (n+-a-Si:H) or bilayers of aluminum (Al) and intrinsic a-Si:H. The bridge is suspended over a gate electrode with a 1 μm air-gap. Applying a voltage between the bridge and an underlying Al gate electrode electrostatically actuates the microstructures. The resulting deflection is monitored optically. The resonance of the microbridges is measured in air and in vacuum. Resonance frequencies up to 70 MHz and quality factors up to 3000 are obtained at pressures below 1 Torr. The energy dissipation mechanisms of the resonators are discussed.
Above-Threshold Parameter Extraction Including Contact Resistance Effects for a-Si:H TFTs on Glass and Plastic
Authors: Servati Peyman , Striakhilev Denis , Nathan Arokia 
Published: June 2019

AbstractThis paper presents a fast and accurate method for extraction of the above-threshold physical parameters (such as threshold voltage, power parameter, effective mobility, and contact resistance) from measurement data in the linear and saturation regions of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) fabricated on glass and plastic substrates. The method of extraction is different from techniques that are currently used by virtue of the departure from the square law dependence of the current-voltage characteristics. In addition, a broader range of process-induced variation in material properties is expected, which is accentuated by the effects of different substrates, leading to wide-ranging device parameters. In particular, non-ideal parameters such as contact resistance may vary by orders of magnitude due to process variations, thus strongly influencing the extracted values of TFT parameters if its effect is not considered in the extraction method. In this paper, the effect of contact resistance and other non-ideal parameters is systematically identified and eliminated using TFTs with different channel length. The extracted values for TFTs on glass and plastic substrates clearly highlights the differences in material properties stemming from the different process conditions and substrate properties, and provide insight that is invaluable for subsequent device/process optimization.
Depth Profiling of Light-Induced Defects in Hydrogenated Amorphous Silicon by Transient Photocurrent Spectroscopy
Authors: Reynolds Steve , Main Charlie , Brüggemann Rudi 
Published: June 2019

AbstractThe sensitivity of transient photocurrent measurements to the spatial location of native and metastable electronic defects in hydrogenated amorphous silicon films is demonstrated. The technique utilises red and green laser excitation to generate excess carriers in the bulk and at the surfaces of the film, respectively. In annealed films the defect density is found to be higher in the surface regions. Following white light soaking, the metastable defect density at the surface at which the light is incident is greater than that in the bulk, which in turn is greater than that at the exit surface. This is attributed to the white light absorption profile within the film. Green light soaking creates metastable defects at the incident surface, with the bulk of the film largely unaffected.
Micro-Raman Studies of Mixed-phase Hydrogenated Silicon Solar Cells
Authors: Owens Jessica M. , Han Daxing , Yan Baojie , Yang Jeffrey , Lord Kenneth , Guha Subhendu 
Published: June 2019

AbstractThe open-circuit voltage (Voc) of mixed-phase hydrogenated silicon solar cells has been found to increase after light soaking. In this study, we use micro-Raman to investigate the heterogeneous structure of solar cells in the amorphous-to-nanocrystalline transition region. For a cell with Voc = 0.981 V, Raman spectra show a typical broad Gaussian lineshape around 480 cm-1, a signature of typical amorphous material. A cell with Voc = 0.674 V displays a sharp Lorentzian peak around 516 cm-1, indicative of nanocrystallinity. A cell with Voc = 0.767 V was systematically scanned for 20 different positions in 500 μm increments. Most spectra show a typical Gaussian lineshape around 480 cm-1, several spectra reveal a hint of a nanocrystalline shoulder around 512 cm-1, and one spectrum exhibits a distinct nanocrystalline peak. We conclude that the nanocrystallite distribution in the mixed-phase material is very non-uniform even within a mm dot. This result provides direct evidence supporting a recently proposed two-diode equivalent-circuit model to explain the light-induced effect.
Metamict Transformation of Silica
Authors: Cheng Ju-Yin , Treacy M.M. J. , Keblinski P. J. 
Published: June 2019

AbstractAlpha quartz can be transformed to a metamict phase in a physical reaction such as irradiation with fast ions, neutrons and electrons. As truly inspired by this fact, we design a simple experiment to produce disordered silica and at the same time watch the transformation using a transmission electron microscope. This work simply presents electron-damaged silica in dark field at Bragg reflection. Since the transformation is not complete, disordered silica (at the sample edge) and retained quartz can be compared in each image. Not surprisingly, more speckles are found in the quartz than in the disordered structure. But it is too early to say no medium-range ordering in amorphous silica because the experiment only shows one Bragg diffraction. Systematic work to complete and measure the disordering again is being pursued.