bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotope Exchange in Hydrogenated Silicon-Oxynitride (SiON) for 1.55μm Optical Waveguide Applications
Authors: Lee Jinju , Cheng Kangguo , Lyding Joseph W. , Salemink Huub W.M.
Published: April 2011

We report a novel way of reducing the unwanted absorption loss in silicon-oxynitride (SiON) waveguides by replacing nitrogen-hydrogen (N-H) bonds with nitrogen-deuterium (N-D) bonds in an isotope exchange process. D was introduced to SiON layers in an atmospheric D anneal after the deposition of SiON. The deuterated SiON showed a factor of 2 less absorption at 1.51 μm than before the D anneal. This is an additional loss reduction, since a typical pre-anneal in N2 reduces the loss by a factor of 10. Compared to the loss in as-deposited SiON at this wavelength, the loss after D anneal is reduced by a factor of 20. The D annealing temperature varied from 450 to 950 °C. There is a correlation between the loss reduction and the level of isotope exchange in the SiON waveguide, and also, an onset temperature for thermal activation of the isotope exchange. This mechanism is characterized carefully by secondary ion mass spectrometry (SIMS).
Transport Properties of Polycrystalline Silicon with Various Textures and Microstructures
Authors: Kamiya Toshio , Nakahata Kouichi , Suemasu Atsushi , Ro Kazuyoshi , Fortmann C.M. , Shimizu Isamu
Published: April 2011

Carrier transport property was studied in relation to microstructure for polycrystalline silicon (poly-Si) prepared from SiF4 and H2 gas mixtures at temperatures below 360°C. It was found that Hall mobility markedly increased with the increase in crystal fraction especially at crystal fractions larger than 80% and it exhibited good correlation with orientation fluctuation as well as with crystal fraction. In addition, dependence of Hall mobility on orientation fluctuation exhibited different tendency between (220) and (400) oriented poly-Si. It suggests that atomic configuration and electronic structure at grain boundaries depends on orientation structure, resulting in the different dependence of Hall mobility on orientation fluctuation. By applying hot-vapor annealing at 310°C to 1 μm-thick P-doped (400) oriented poly-Si, Hall mobility was improved from 10 cm2/Vs to 17 cm2/Vs.
A Laplace Transform Technique for Direct Determination of Density of Electronic States in Disordered Semiconductors from Transient Photocurrent Data
Authors: Gueorguieva Mariana J. , Main Charles , Reynolds Steve
Published: April 2011

A new technique for direct determination of the density of electronic states (DOS) in disordered semiconductors is described. It involves Laplace transformation of transient photocurrent data I(t) followed by the numerical solution of the system of linear algebraic equations obtained from the Fredholm integral of the first kind, for a DOS represented by a series of discrete levels. No approximations are used in the solution, and no prior assumptions as to the form of the DOS are made. The fidelity of this method is assessed and compared with existing techniques by application to computer-simulated I(t) data generated from single-level and continuous DOS profiles, and to experimental data.
Hydrogenated Amorphous Silicon and Silicon Nitride Deposited at less than 100° C by ECR-PECVD for Thin Film Transistors
Authors: Flewitt Andrew J. , Dyson Andrew P. , Robertson John , Milne William I.
Published: April 2011

A systematic study has been made of the growth of both hydrogenated amorphous silicon (a-Si:H) and silicon nitride (a-SiN) by electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD). In the case of a-SiN, helium and nitrogen gas is injected into the system such that it passes through the resonance zone. These highly ionised gases provide sufficient energy to ionise the silane gas, which is injected further downstream. It is demonstrated that a gas phase reaction occurs between the silane and nitrogen species. It is control of the ratio of silane to nitrogen in the plasma which is critical for the production of stoichiometric a-SiN. Material has been produced at 80 °C with a Si:N ratio of 1:1.3 a breakdown strength of ∼6 MV cm−1 and resistivity of >1014 Ωcm. In the case of a-Si:H, helium and hydrogen gas is injected into the ECR zone and silane is injected downstream. It is shown that control of the gas phase reactions is critical in this process also. a-Si:H has been deposited at 80 °C with a dark conductivity of 10−11 Ω−1 cm−1 and a photosensitivity of just below 4×104. Such materials are suitable for use in thin film transistors on plastic substrates.
Preparation of Microcrystalline Silicon Based Solar Cells at High i-layer Deposition Rates Using a Gas Jet Technique
Authors: Jones S.J. , Crucet R. , Deng X. , Williamson D.L. , Izu M.
Published: April 2011

A Gas Jet technique has been used to prepare microcrystalline silicon (μc-Si) thin films at deposition rates as high as 20 Å/s. The films have microcrystal sizes between 80 and 120 Å with a heterogeneous microstructure containing regions with columnar growth and other regions with a more randomly oriented microstructure. These materials have been used as i-layers for nip single-junction solar cells. The high deposition rates allow for fabrication of the required thicker μc-Si i-layers in a similar amount of time to those used for high quality a-SiGe:H i-layers (rates of 1-3 Å/s). Using a 610nm cutoff filter which only allows red light to strike the device, pre-light soaked short circuit currents of 8-10 mA/cm2 and 2.7% red-light efficiencies have been obtained while AM1.5 white light efficiencies are above 7%. These efficiencies are higher than those typically obtained for μc-Si cells prepared at the high i-layer growth rates using other deposition techniques. After 1000 h. of light soaking, the efficiencies on average degrade only by 2-5% (stabilized efficiencies of 2.6%) consistent with the expected high stability with the microcrystalline materials. The small amount of degradation compares with the 15-17% degradation in efficiencies for a-SiGe:H cells subjected to similar irradiation treatments (final light-soaked red light efficiencies of 3.2%). Improvements in the cell efficiencies may come through an understanding of the role that columnar microstructure and void structure plays in determining the device performance.
Thickness and Interface Layer Effects on the Amorphous Silicon Film Property Studied by Various Photoluminescence Excitation Wavelengths
Authors: Yue Guozhen , Han Daxing , Yang Jeffrey , Guha Subhendu
Published: April 2011

We have studied the structure of highly hydrogen-diluted a-Si:H films by using Raman and photoluminescence (PL) spectroscopies. Raman spectra show a typical broad a-Si:H peak in the films with different substrate surfaces or i-layer thicknesses, except for one 1.4 μm film deposited directly onto a stainless steel (ss) substrate that shows the c-Si peak. An apparent μc-Si component was characterized by a low energy PL enhancement in a 0.5 μm film deposited directly onto the ss substrate. When a thin n-layer was inserted between the substrate and the a-Si film, no μc-Si growth was found in the first 0.5-1.0 μm thick layer but there was a μc-Si component in the top surface layer when the film was grown to a 1.5 μm thickness. The nonuniformity structure along the growth direction was characterized by PL spectroscopy using varied laser excitation wavelengths of 325, 488, 514.5, and 632.8 nm. We find that PL spectroscopy is a sensitive tool to characterize the microcrystallinity of the film.
In-line Characterization of Thin Polysilicon Films by Variable Angle Spectroscopic Ellipsometry
Authors: Paprotta S. , Röver K. S. , Ferretti R. , Höhne U. , Kähler J. D. , Haase J.
Published: April 2011

Up to now an in-line method for parameter determination of deposited thin polysilicon films is not available. In this paper a method for monitoring the polysilicon deposition process in device manufacturing by variable angle spectroscopic ellipsometry (VASE) is demonstrated. Therefore several polysilicon films are deposited on thermally oxidized [100] silicon wafers. These samples are characterized by VASE in the optical range of 450 - 850 nm. Parameters are determined by simulation using a multilayer model consisting of air, interface layer (surface roughness), polysilicon, SiO2 and silicon substrate. Different optical models representing the properties of polysilicon are tested. The free parameters are the oxide thickness, the composition and the thickness of the interface layer (air, polysilicon) as well as the thickness and the complex refractive index of the polysilicon layer. Results of the spectroscopic analysis are verified by AFM and SEM measurements. It can be shown that parameters of the deposited polysilicon films, which often could only be determined by complex and destructive off-line analysis methods are also accessible by non-destructive in-line VASE measurements.
Electromigration Reliability of Dual-Damascene Cu/Oxide Interconnects
Authors: Ogawa Ennis T. , Blaschke Volker A. , Bierwag Alex , Lee Ki-Don , Matsuhashi Hideki , Griffiths David , Ramamurthi Anup , Justison Patrick R. , Havemann Robert H. , Ho Paul S.
Published: April 2011

An electromigration study has determined the lifetime characteristics and failure mode of dual-damascene Cu/oxide interconnects at temperatures ranging between 200 and 325 °C at a current density of 1.0 MA/cm2. A novel test structure design is used which incorporates a repeated chain of “Blech-type” line elements. The large interconnect ensemble permits a statistical approach to addressing interconnect reliability issues using typical failure analysis tools such as focused ion beam imaging. The larger sample size of the test structure thus enables efficient identification of “early failure” or extrinsic modes of interconnect failure associated with process development. The analysis so far indicates that two major damage modes are observable: (1) via-voiding and (2) voiding within the damascene trench.
Theoretical and Experimental Analysis of the Low Dielectric Constant of Fluorinated Silica
Authors: Demkov A. , Zollner S. , Liu R. , Werho D. , Kottke M. , Gregory R.B. , Angyal M. , Filipiak S. , Adams G.B.
Published: April 2011

Fluorinated silica has a dielectric constant lower than that of F-free SiO2 and is a potential interlayer dielectric. We investigate the F-doped SiO2 with ab-initio modeling and various characterization techniques searching to explain the dielectric constant reduction. FTIR transmission and spectroscopic ellipsometry give us information about the ionic and electronic contributions to ε. Nuclear reaction analysis and Auger spectrometry measure F composition. XPS and FTIR provide information on the atomic structure of the film. We use several cells of cristobalite to model fluorinated silica using the electronic structure theory. The ground state geometry, vibrational density of states, electronic band structure, and Born effective charges are analyzed. The calculations suggest that it is the ionic component of the dielectric constant that is mostly effected by the F incorporation.
Study of Dry Photoresist Stripping Processes for Hydrogen Silsesquioxane Thin Films
Authors: Liou Huey-Chiang , Duel Jerry , Finch Victor , Han Qingyuan , Sakthivel Palani , Ruffin Ricky
Published: April 2011

The impact of dry stripping process chemistries on the selective removal DUV photoresist (PR) in the presence of hydrogen silsesquioxane (HSQ) have been studied along with HSQ film properties in order to develop a new, effective process to minimize changes in HSQ during the PR stripping processes. The results show that oxygen-free gas mixtures, specifically H2/N2 gas mixtures, have the best combination of PR:HSQ ash selectivity and minimized changes in HSQ films. However, gas mixtures containing CF4 or O2 greatly reduce PR/HSQ ash selectivity. The process temperature is another parameter that strongly influences ash selectivity. While the higher ash temperature greatly enhances selectivity in oxygen-free gas mixtures, the ash selectivity is only marginally enhanced with increasing ash temperature in the presence of O2. Furthermore, the k-value of HSQ suffers in the presence of O2 due to the oxidization of HSQ films. The data also shows that lower pressure will help to increase ash selectivity. In this study, processes have been demonstrated, which yield a PR:HSQ selectivity greater than 150, while maintaining the dielectric constant of HSQ at 2.8.
Sol-Gel Derived Silica Layers for Low-k Dielectrics Applications
Authors: Acosta Sylvie , Ayral André , Guizard Christian , Lecornec Charles , Passemard Gérard , Moussavi Mehdi
Published: April 2011

Porous silica exhibits attractive dielectric properties, which make it a potential candidate for use as insulator into interconnect structures. A new way of preparation of highly porous silica layers by the sol-gel route was investigated and is presented. The synthesis strategy was based on the use of common and low toxicity reagents and on the development of a simple process without gaseous ammonia post-treatment or supercritical drying step. Defect free layers were deposited by spin coating on 200 mm silicon wafers and characterized. Thin layers with a total porosity larger than 70% and an average pore size of 5 nm were produced. The dielectric constant measured under nitrogen flow on these highly porous layers is equal to ∼ 2.5, which can be compared to the value calculated from the measured porosity, ∼ 1.9. This difference is explained by the presence of water adsorbed on the hydrophilic surface of the unmodified silica.
Effects of Curing Temperature on the Mechanical Reliability of Low Dielectric-Constant Spin-on-Glasses
Authors: Toivola Yvete , Cook Robert F. , Saha Chandan
Published: April 2011

The variations in the mechanical properties of a commercial low-k silsesquioxane material with curing temperature are examined, focusing on the transition from the low modulus, high stress, under-cured state to the high modulus, low stress, over-cured state. Film modulus and hardness are determined by instrumented nanoindentation and film dielectric constant is determined by ac capacitance measurements of metal dot structures. The mechanical behavior is correlated with changes in molecular structure via infrared spectroscopy. An implication of the results is that there is an intermediate curing temperature for optimum silsesquioxane interconnection performance.
Reliability of Tantalum Based Diffusion Barriers between Cu and Si
Authors: Laurila Tomi , Zeng Kejun , Seppälä A. , Molarius Jyrki , Suni Ilkka , Kivilahti Jorma K.
Published: April 2011

The reaction mechanisms in the Si|Ta|Cu and Si|TaC|Cu metallization systems are discussed based on the experimental results and the assessed ternary Si-Ta-Cu, Si-Ta-C and Ta-C-Cu phase diagrams. The ternary Si-Ta-N and Ta-N-Cu phase diagrams were also assessed in order to compare the thermodynamic properties of the TaC diffusion barriers to more widely investigated TaNx diffusion barriers. With the help of the sheet resistance measurements, RBS, XRD, SEM, and TEM the Ta barrier layer was observed to fail above 650 °C due to the formation of TaSi2. This was accompanied by the diffusion of Cu through the silicide layer and the resulting formation of Cu3Si precipitates. The stability of the TaC layers was better and the failure was observed above 750 °C due to the formation of Cu3Si and TaSi2. However, interdiffusion of Cu and Si was observed already at lower temperatures due to the presence of pinholes in the TaC layer. This emphasises the importance of the fabrication method and the quality of the TaC layers.
Integrated CVD-PVD Al Plug Process for Sub-Quarter Micron Devices: Effects of Underlayer on the Via Filling and the Microstructure of the Al Film
Authors: Lee Won-Jun , Kim Jung Joo , Kim Jun Ki , Park Jin Won , Kwon Hyug Jin , Park Heung Lak , Rha Sa-Kyun
Published: April 2011

The integrated CVD-PVD Al plug process was successfully applied to a sub-quarter micron device for the simultaneous formation of plugs and wires. The effects of the underlayer on the via filling and the microstructure of the CVD-PVD Al films were investigated. Three types of underlayers were examined in this work: the Ti film deposited by the ionized PVD (I-PVD) method, the MOCVD TiN film stacked on the I-PVD Ti film, and the PVD Al film deposited on the I-PVD Ti film. Excellent via filling was achieved by employing the MOCVD TiN/I-PVD Ti or the PVD Al/I-PVD Ti as an underlayer. When only I-PVD Ti film was used as an underlayer, complete via filling was not obtained, because the CVD Al film sealed the top of vias. The CVD-PVD Al film deposited on the PVD Al/I-PVD Ti underlayer also showed excellent crystallographic texture of Al <111> and surface morphology, which is superior to those of the CVD-PVD Al film deposited on the MOCVD TiN/I-PVD Ti underlayer.
Comprehensive Reactor-Scale Modeling of III-V Ternary Compound Growth by Movpe
Authors: Yakovlev E.V. , Talalaev R.A. , Karpov S. Yu. , Shpolyanskiy Yu.A. , Makarov Yu.N. , Lowry S.A.
Published: April 2011

A novel quasi-thermodynamic approach is suggested to simulate surface chemistry in III-V compound MOVPE. Blocking of free adsorption sites by methyl radicals is considered as the mechanism limiting the growth rate at low temperatures. This assumption has provided a good reproduction of experimental data on GaAs MOVPE in various types of reactor. The commercial computational fluid dynamics software CFD-ACE™ has been used to perform a detailed threedimensional modeling of AlGaAs and InGaP deposition in an AIX-200 horizontal reactor. The surface model has been incorporated into the code to obtain the growth rate and layer composition distributions over the substrate. Modeling results demonstrate a reasonable agreement with experimental data.
Nitrogen Incorporation and Growth Kinetics of GaAsN/GaAs Epilayers Grown by MOVPE
Authors: Auvray Laurent , Dumont Hervé , Dazord Jacques , Monteil Yves , Bouix Jean
Published: April 2011

The nitrogen incorporation behavior in GaAs was investigated in the growth temperature range 500-600°C. It was observed that the temperature-dependence of the nitrogen incorporation exhibits two regimes. At 530°C, the nitrogen content x is a nonlinear function of the gas-phase composition indicating a surface-controlled reaction mechanism. The N composition varies slowly with 500°C < T < 560°C with an activation energy of 0.6 eV. For T < 560°C, N decreases exponentially with Ea= 3.7 eV, interpreted in terms of nitrogen desorption. In light of experimental results, we propose a surface kinetic model based on the competitive adsorption of group V precursors.
Simulation Of Polycrystalline Silicon Growth By Pulsed Excimer Laser Annealing
Authors: Kudo Toshio , Ichishima Daiji , Jin Cheng-Guo
Published: April 2011

The dynamic simulation of poly-Si film synthesis has been fulfilled by means of the overlapping irradiation of single- and double-pulsed XeCl excimer lasers shaped into the line beam. A novel model applied to the dynamic simulation is based on the homogeneous nucleation, and the growth and shrinkage velocity of Si grains. The results simulated with the single-pulsed XeCl excimer laser has reproduced the super lateral growth (SLG) phenomenon which occurs in the very narrow range of energy density (the near complete melt regime). The actual energy density dispersion within 5.3% allows us to visualize the multiformity of grain sizes in the cross sectional texture. Standing on the reproduction of the SLG phenomenon by the single-pulsed irradiation, we have obtained the practical knowledge of the growth process of larger grains by the double-pulsed irradiation. We intend that the first pulse has charge of completely melting and the second pulse has charge of adjusting the number of nuclei. The adjustment of the first pulse energy density rather than that of the second pulse energy density leads to the growth of huge columnar grains much larger than the thickness of the Si layer. For the double-pulsed irradiation, the influence of the worst energy density dispersion (each of double pulses has the same fluctuation as the single pulse) is much larger than that of the actual delay time jitter (within 2.5ns) in a sense of the multiformity of grain sizes.
Influence Of Substrate Temperature On Barium Ferrite Films Prepared by Laser Deposition
Authors: Song W.D. , Lu Y.F. , Wang W.J. , Chong T.C.
Published: April 2011

Influence of substrate temperature on properties of barium ferrite films prepared by laser deposition is studied in this paper. The magnetic properties, grain shape and crystalline orientation of the films are discussed for the films prepared by laser deposition with in-situ heating, post annealing and varying substrate temperature. The results show that magnetic properties, grain shape and crystalline orientation of the film deposited with varying substrate temperature are close to the film deposited with post-annealing and different to the film deposited with in-situ heating.
Oxygen Content And Crystallinity Effects in Pulsed Laser Deposited Lanthanum Manganite Thin Films
Authors: Pietambaram Srinivas V. , Kumar D. , Singh Rajiv K. , Lee C. B.
Published: April 2011

Eventhough colossal magnetoresistance in Lanthanum calcium manganite (LCMO) thin films was known for a long time, the effect of oxygen content and crystallinity on the properties of these films is not clearly understood. It is in this context that we have performed a systematic study of these effects by annealing the films in various ambients. A series of LCMO thin films have been grown in situ on (100) LaAlO3 substrates using a pulsed laser deposition technique under identical conditions. Microstructural characterization carried out on these films has shown that the films are smooth, single phase and highly textured. The films were subjected to the following post deposition treatments: (i) annealing in oxygen at 900°C for 4 hrs, (ii) annealing in argon at 900°C for 4 hrs, (iii) annealing in oxygen at 500°C for 12 hrs, (iv) annealing in argon for 12 hrs and (v) annealing in vacuum at 850°C for half-an-hour. As deposited LCMO films show a transition temperature of 260 K and a magnetoresistance ratio (defined as [R(0)−R(H)/R(H)]) of 190% at 260 K in 5T magnetic field. The samples subjected to 500°C oxygen and Ar anneal have shown no change in the transition temperature and MR ratio. The films subjected to a 900°C annealing in Ar ambient have shown marginal improvement in transition temperature but a drastic improvement in the MR ratio (525%). 900°C oxygen annealed films have shown an improvement in the transition temperature (290 K) and MR ratio (225%) over as deposited films. Vacuum annealed samples have shown deteriorated properties. These results indicate that the metal-insulator transition is related to the oxygen content of the films while the MR ratio is related to the domain size.
Surface Processing And Micromachining of Polyimide Driven by A High Average Power Infra-Red Free Electron Laser
Authors: Kelley Michael J.
Published: April 2011

The long history and wide use of polyimide as a dielectric in the microelectronics industry has made it a favorite material for laser processing studies. The FEL used in the present work delivered picosecond-long 25 microjoule pulses at approximately 3.10 and 5.80 microns. The former is not associated with any strong absorption, while the latter is the strongest absorption band in the IR. This study explored hole drilling and surface transformation of as-made and aluminized DuPont Kapton HN PMDA-ODA polyimde film.
Growth Of ZnO/MgZnO Superlattice On Sapphire
Authors: Muth J.F. , Teng C.W. , Sharma A.K. , Kvit A. , Kolbas R.M. , Narayan J.
Published: April 2011

The optical and structural properties of ZnO/ MgZnO superlattices were investigated by transmission electron microscope, transmission measurement and photoluminescence. The uncoupled wells ranged in thickness from ∼30 Å to 75 Å. Modulation of the Mg content was observed in Z-contrast TEM indicating the alloy composition was periodic. The density of stacking faults in the superlattice was extremely high, however the photoluminescence in the narrowest well case was blue shifted, and substantially brighter than comparable bulk layers of ZnO and MgZnO indicating that the emission was enhanced. Excitonic features were observed in the optical absorption spectra and also revealed that diffusion of Mg from the barrier layers into the well was occurring.
Growth kinetics and diffraction properties of STMV crystals
Authors: Kuznetsov Yu. G. , Malkin A. J. , McPherson A.
Published: April 2011

Two crystal forms, orthorhombic and cubic, of satellite tobacco mosaic virus have been investigated. Atomic force microscopy showed that the orthorhombic crystals were characterized by a high density of point defects, while the cubic crystals were practically defect-free. Nonetheless, orthorhombic crystals diffract to a high resolution of 1.8 Å while the cubic crystals diffract to only about 4 to 6 Å resolution. Differences in the properties of viruses incorporated into the two crystal structures were demonstrated by growth kinetics studies. It appears that physical and chemical treatments applied to protein and virus solutions during their extraction and purification introduce a variety of specific structural changes and that these alterations may then affect the diffraction properties of resultant macromolecular crystals.
Novel Studies of Roughening of the Prism Plane of Ice
Authors: Williamson Ann-Marie , Lips Alex
Published: April 2011

A novel technique for examining kinetic roughening of crystals is described, and applied to the study of the prism plane of ice in contact with aqueous fructose solution. The technique can be generally applied to crystals that roughen at low driving forces. Since the residual driving force for growth utilised is that due to Ostwald ripening, this technique also facilitates simultaneous quantification of ensemble growth kinetics and crystal anisotropy during ripening. The driving force required for kinetic roughening, and the step, or ledge, free energy of this plane of ice show an approximately linear variation with temperature over the experimental temperature range −13°C to −17°C. Whilst we can conclude that the thermodynamic roughening temperature (TR) is higher than −13°C, its precise value, and conformance or otherwise of the roughening transition with Kosterlitz Thouless scaling, can not be concluded from the current data set.
Optical Properties of Microcavity Structures using the Organic Light Emitting Materials
Authors: Jung Boo Young , Kim Nam Young , Lee Chang Hee , Hwangbo Chang Kwon , Seoul Chang
Published: April 2011

We investigated the optical properties of Fabry-Perot microcavity with a tris(8- hydroxyquinoline)aluminum (Alq3) organic film by measuring the photoluminescence (PL) and transmittance. An Alq3 layer as an active layer was sandwiched between two mirrors, which were metal or (TiO2|SiO2) dielectric multilayer reflectors. An Alq3 layer on glass, [air|Alq3|glass], showed a PL peak around 513 nm and its full width half maximum (FWHM) was about 80 nm. Three types of microcavity, such as Type A [air|metal|Alq3|metal|glass], Type B [air|dielectric|Alq3|dielectric|glass], and Type C [air|metal|Alq3|dielectric|glass], were fabricated. The result shows that the FWHMs of three Fabry-Perot microcavities were reduced to 15∼27.5, 7∼10.5 and 16∼16.6 nm, respectively, and the microcavity structure is expected to improve the efficiency and tunability of emission spectrum in display.
Location-Controlled Large-Grains in Near-Agglomeration Excimer-Laser Crystallized Silicon Films
Authors: van der Wilt Paul Ch. , Ishihara Ryoichi , Bertens Jurgen
Published: April 2011

Large grains in thin silicon films were grown by controlling the location of unmolten islands, which are left after near-complete melting of the film during excimer laser crystallization. As the initially amorphous film was first transformed in small grain polycrystalline silicon, these islands contain seeds for crystal growth. To get a single large grain, either the number of seeds was reduced to one or a single one was selected from the seeds by a ‘grain filter’. Former was achieved by making a small indentation in the isolating layer underlying the silicon film so that seeds remain embedded in the indentation. Latter was achieved by making a small diameter hole in the underlying isolating layer, which was filled with amorphous silicon. The lateral growth is preceded by a vertical growth phase during which a single grain is filtered from the initial set of seeds present at the bottom of the hole. In the experiment described, highest yield was achieved for samples in which the melt-depth to hole- diameter ratio was largest.
Oxide Charging Effects by PH3/He Ion Shower Doping
Authors: Kim Cheon-Hong , Yoo Juhn-Suk , Park Kee-Chan , Han Min-Koo
Published: April 2011

We report the oxide charging effects on metal oxide semiconductor (MOS) structure caused by PH3/He ion shower doping. The parallel negative shift of flat-band voltage occurred for the ion-doped PETEOS samples even after thermal annealing. When the ion dose was higher, this shift was larger. These results show that a considerable amount of positive charges were induced inside the oxide films after PH3/He ion shower doping process. For the same ion dose, the flat-band voltage shift is larger when the thickness of PETEOS is thicker. When the ion dose was 1.5×1017cm−2and the thickness of PETEOS was 80nm, the shift of flat-band voltage was larger than −7V. We can conclude that PH3/He ion shower doping process induces the positive charges, which result in the flat band voltage shift of MOS capacitors, in the bulk oxide films when oxide films are exposed to ion shower doping.
Location Control of Laterally Columnar Si Grains by Dual-Beam Excimer-Laser Melting of Si Thin-Film
Authors: Ishihara Ryoichi
Published: April 2011

The offset of the underlying TiW is introduced in the island of Si, SiO2 and TiW on glass. During the dual-beam excimer-irradiation to the Si and the TiW, the offset in TiW acts as an extra heat source, which melts completely the Si film near the edge, whereas the Si inside is partially melted. The laterally columnar Si grains with a length of 3.2 μm were grown from the inside of the island towards the edge. By changing the shape of the edge, the direction of the solidification of the grain was successfully controlled in such a way that the all grain-boundaries are directed towards the edge and a single grain expands. The grain-boundary-free area as large as 4 μm × 3 μm was obtained at a predetermined position of glass.
Effects Due to and Derived from Spontaneous Ordering in III-V Semiconductor Alloys
Authors: Zhang Yong , Mascarenhas A.
Published: April 2011

Two interesting and important aspects of spontaneous CuPt ordering in III-V semiconductor alloys, which have only been investigated recently, are reviewed in this paper. The first aspect addresses the statistical effects that should be considered as the most unique consequence of the phenomenon of ordering, more specifically, how ordering affects the alloy fluctuations and hence the physical properties of the alloy. The second aspect tackles some intriguing properties of the domain twins of two CuPt ordered variants, specifically, considering the transmission of a ballistic electron beam through such a domain twin and its analogy to a highly interesting phenomenon, negative refraction, for light.
Synthesis, Characterization and Application of Thin Film Carbon Nanotube Material
Authors: Obraztsov Alexander N. , Volkov Alexander P.
Published: April 2011

The non-catalytical chemical vapor deposition (CVD) method was used to grow carbon thin film material consisting of plate-like nanosized graphite crystallites and multiwall carbon nanotubes with predominant orientation of both species by their crystallographic plane, corresponding to a graphite basal plane, along a normal to the film surface. A number of experimental techniques was used for examination and characterization of the film phase composition, morphology, and electron properties peculiarities. Low-field electron emission with highly density of emission sites and emission current was obtained for the film material and allow to demonstrate their applicability for sealed prototypes of light-emitting devices.
Surrounding effects in single-walled and multi-walled carbon nanotubes
Authors: Buisson Jean-Pierre , Chauvet Olivier , Lefrant Serge , Stephan Christophe , Benoit Jean-Michel
Published: April 2011

The low frequency RBM observed in SWNTs has been proved to probe efficiently their diameter distribution. We have built a model to estimate the interactions between individual nanotubes when arranged in bundles which leads to a RBM upshift of 10 to 20 cm−1. In a PMMA-SWNTs composite, our model shows that an upshift can be also predicted as due to the stress applied by the polymer on the bundles upon breathing. Finally, the interaction between concentric layers in MWNTs can lead to low frequency modes originating from the RBM of individual tubes as observed experimentally.
Scanning Tunneling Microscopy and Spectroscopy of Short Multiwall Carbon Nanotubes
Authors: Hassanien A. , Mrzel A. , Tokumoto M. , Zhao X. , Ando Y. , Tománek D.
Published: April 2011

We report on the structural analysis of multiwall carbon nanotubes (MWNTs), produced by DC arc discharge in hydrogen gas, using a scanning tunneling microscope operated at ambient conditions. On a microscopic scale the images show tubes condensed in ropes as well as individual tubes which are separated from each other. Individual nanotubes exhibit various diameters (2.5-6 nm) and chiralities (0-30Å). For MWNTs rope, the outer portion is composed of highly oriented nanotubes with nearly uniform diameter (4-5 nm) and chirality. Strong correlation is found between the structural parameters and the electronic properties in which the MWNTs span the metallic-semiconductor regime. True atomic-resolution topographic STM images of the outer shell show hexagonal arrangements of carbon atoms that are unequally visible by STM tip. This suggests that the stacking nature of MWNTs, may effect the electronic band structure of the tube shells. Unlike other MWNTs produced by arc discharge in helium gas, the length of the tubes are rather short (80-500 nm), which make it feasible to use them as a components for molecular electronic devices.
Application of Carbon Nanotubes and Fullerenes for Thermal Management in Ceramics
Authors: Yowell Leonard L. , Mayeaux Brian M. , Wang Hsin , Barrera Enrique V.
Published: April 2011

New techniques for thermal management in ceramics at the nanoscale level have been investigated using low percentages of carbon nanotubes to reduce thermal conductivity of bulk ceramics. Samples of yttria-stabilized zirconia containing purified single-walled carbon nanotubes (SWNT) or vapor grown carbon fibers (VGCF) have been prepared by tape casting and analyzed using the laser flash method to evaluate reductions in thermal conductivity at high temperatures. New features in the samples due to the presence of carbon nanotubes have been characterized using Raman, SEM, TEM and, in the case of VGCFs, are related to significant reductions in thermal conductivity (>25%). The inclusion of a low percentage of nanoscale carbon fibers, the intimate relationship between the fibers and ceramic particles, and the indication that the fibers possess a crystalline overcoating, all contribute to the lowering of the thermal conductivity.
Rapid, Room Temperature, High-Density Hydrogen Adsorption on Single-Walled Carbon Nanotubes at Atmospheric Pressure Assisted by a Metal Alloy
Authors: Heben M.J. , Dillon A.C. , Gennett T. , Alleman J.L. , Parilla P.A. , Jones K.M. , Hornyak G.L.
Published: April 2011

Laser-generated, carbon single-walled nanotubes (SWNTs) adsorb hydrogen in a matter of minutes at room temperature and atmospheric pressure in the presence of a Ti-6Al-4V metal alloy. The unusual hydrogen adsorption properties are activated when the SWNTs are sonicated in nitric acid with a Ti-6Al-4V probe. The process cuts the SWNTs and introduces ∼15-40 wt% metal alloy into the previously pure single-walled nanotube material. Subsequent hydrogen adsorption occurs in two separate sites with a maximum adsorption capacity of ∼7 wt% on a total sample weight basis. Approximately 2.5 wt% hydrogen is evolved at 300 K while the remainder desorbs between 475-850 K. The pure metal alloy adsorbs ∼ 2.5 wt% H2, and evolvesydrogen with increasing temperature in a manner similar to the alloy-doped SWNTs. However, it is clear from studies presented here that the SWNT fraction is quite active in H2 uptake, adsorbing as much as 7 % on a SWNT weight basis.
Electrical Rectification by a Monolayer of Hexadecylquinolinium Tricyanoquinodimethanide Sandwiched between Gold Electrodes
Authors: Metzger Robert M.
Published: April 2011

Unimolecular rectification, previously reported between oxide-bearing electrodes, was detected between oxide-free Au electrodes for a Langmuir-Blodgett monolayer of the zwitterionic D+-π-A− molecule hexadecylquinolinium tricyanoquinodimethanide, C16H33Q-3CNQ. The top gold electrode was deposited from a Au vapor pre-cooled by multiple collisions with Ar atoms. The maximum rectification ratio is 27.5 at 2.2 Volts (the average rectification ratio is 7.55). The currents are as large as 9.04 × 104 electrons molecule−1 s−1. The result reinforces previous work with oxide-bearing Al electrodes, but the currents with Au electrodes are larger by three to five orders of magnitude.
A New Assembling Method for Nano-sized Particles Using an Electrified Pattern Drawn by a Focused Ion Beam
Authors: Fudouzi Hiroshi , Kobayashi Mikihiko , Shinya Norio
Published: April 2011

This paper describes a new technique to fabricate two-dimensional microstructures assembled with nano-sized particles. The nano-sized particles attract a lot of attention because of their unique properties compared to bulk materials. Micro- and nano- structures assembled with nano-sized particles have potential applications in electronic, optical and biochemical fields. The Self-Assembled Monolayer (SAM) film patterning is one of the methods to assemble the nano-sized particles. We have proposed a new method to assemble nano-sized particles on a substrate using an electric field generated by an electrified pattern. In this study, following our methods titanium oxide (TiO2, diam.=21nm) particles were patterned on an n-type (100) silicon substrate having an oxidized layer. The particle deposition on the substrates was carried out using a colloidal suspension process and an aerosol process.
Laser Ablation Fabricated Nano-Composite of Metal Silicide Crystallines in Silicon Wire
Authors: Qi Jifa , Masumoto Yasuaki
Published: April 2011

Silicon nanowires containing a high density of copper atoms were prepared by laser ablation of Si/metal mixture targets at 1200 °C in argon gas flow. Copper atoms can gather in Si nanowires and precipitate into copper silicide nanocrystals distributed alone the wire axis. The diameters of the copper silicide nanocrystals increase with that of the host nanowire. The possible growth process of the composite nanowires was proposed.
Full Color Luminescence from Amorphous Silicon Quantum Dots Embedded in Silion Nitride
Authors: Park Nae-Man , Kim Tae-Soo , Choi Chel-Jong , Seong Tae-Yeon , Park Seong-Ju
Published: April 2011

Amorphous silicon quantum dots (a-Si QDs), which show a quantum confinement effect, were grown in a silion nitride film by plasma enhanced chemical vapor deposition. Red, green, blue, and white photolumiscence were observed from the a-Si QD strictures by controlling the fot size. An organe light-emitting device (LED) was fabricated using a-Si QDs with a mean size of 2.0 nm. The turn-on vottage was less than 5 V. An external quantum effiency of 2×10−3 % was also demonstrated. These results show that an LED using a-Si QDs embedded in the silicon nitride film is superior in terms of electrical and optical properties to other Si-based LEDs.
Low Temperature growth of poly-crystalline film of Silicon-rich Silicon-Germanium by Reactive Thermal Chemical Vapor Deposition
Authors: Shimizu Kousaku , Zhang Jianjun , Lee Jeong-Woo , Hanna Jun-Ichi
Published: April 2011

Low temperature growth of poly-SiGe has been investigated by reactive thermal chemical vapor deposition method, which is a newly developed technique for preparing poly-SiGe by using redox reactions in a set of source materials, i.e., Si2H6 and GeF4. In order to prepare silicon-rich poly-SiGe of high mobility, a series of experiment on total pressure, gas flow rates of the source materials and dilution gas of He, and residence time at 450°C has been investigated.

At 0.45 Torr, high crystallinity films with high silicon content were prepared, however, homogeneity of film thickness and reproducibility of the film growth was quite low for device application. For overcoming this problem, the growth condition has been studied especially in higher-pressure range of 5-15 Torr. Appropriate choice of the residence time and the gas flow ratios lead to significant improvement in the Si content in the films. Finally, more than 95% of silicon-rich poly-SiGe films, which is p-type, has 7.5 cm2/Vs of Hall mobility and (220) orientation, have been prepared at 10 Torr and 450°C within ±2% fluctuation of reproducibility which is enough to fabricate devices.
Nanocrystalline Silicon by Microwave CVD for Thin Film Transistors and Solar Cells
Authors: Song Young J. , Lee Hak-Gyu , Teng Lihong , Anderson Wayne A.
Published: April 2011

Microwave chemical vapor deposition (MCVD) is utilized to deposit nanocrystalline silicon (nc-si) thin films onto a variety of substrates for application to thin film transistors (TFT's) and solar cells. It is especially important to gain reproducible control of the processing. Thus, an in-situ mass spectrometer (MS) records the plasma conditions with variation of process conditions such as gas selection, pressures, partial pressures, and substrate temperature. These data are correlated with electrical and optical properties of the films. Raman spectra show a FWHM of 11/cm with position at 522/cm as desired for crystalline Si. Typical film thickness is 100nm with grain size of 20-30 nm, using standard deposition, and 50-80 nm when the substrate is intensely optically illuminated during deposition, called photon assist (PA). Hydrogen dilution serves to increase the crystallinity of the films. The ratio of photo-to dark conductivity exceeds 10+5 with dark conductivity as low as 1.5 × 10-10 S/cm. Thin film transistors have been fabricated with Ion/Ioff of 10+7. Hetrojunction solar cells were fabricated using amorphous Si/ nc-Si/ crystlline Si giving a conversion efficiency of above 10.5%, without an antireflection coating. The use of MS in device design will be emphasized.
Fluctuation Microscopy Studies of Medium-range Order Structures in Amorphous Tetrahedral Semiconductors
Authors: Chen Xidong , Gibson J. Murray , Sullivan John , Friedmann Tom , Voyles Paul
Published: April 2011

We applied fluctuation microscopy technique to study medium-range order in tetrahedral semiconductor materials, such as amorphous silicon, amorphous diamond-like carbon films. It is shown that this technique is very sensitive to local structure changes in the medium range order and promises solutions to open questions that cannot be answered by current techniques. For asdeposited amorphous germanium and silicon, we previously identified a fine-grain para-crystallite structure [1, 2], which will be relaxed into a lower-energy continuous random network structure after thermal annealing. With the same fluctuation microscopy technique, we however found that thermal annealing introduces medium-range order in amorphous diamond-like carbon films. Future studies will be focused on modeling and systematic exploration of annealing effects.
CMOS compatible Si/SiO2 multilayers for Light Emitting Diodes
Authors: Gaburro Z. , Pavesi L. , Pucker G. , Bellutti P.
Published: April 2011

We report photoluminescence and electroluminescence at room temperature in diodes based on Si/SiO2 multilayers. The multilayers are fabricated by alternating Si and SiO2 layers, whose thickness is, respectively, 2 and 5 nanometers. In photoluminescence, a single band is observed, centered at 800 nm, which is due to electron-hole pair recombination under quantum confinement. On the other hand, in electroluminescence, two bands are reported. The first band is in the infrared spectrum, and is blackbody radiation. The second band is visible, and is originated by relaxation of a single type of electrical carrier (electrons), as suggested by a fast decay time (less than 0.1 µs). Possible mechanisms can be hot-electron relaxation or coupling with surface plasmon-polaritons.
Strong Enhancement of Porous Silicon Photoluminescence by Dry Photo-Chemical Surface Treatment
Authors: Stolyarova S. , El-Bahar A. , Nemirovsky Y.
Published: April 2011

Porous silicon has been subjected to NF3/UV photochemical surface treatment in the range of 300-4000C. This treatment is found to enhance strongly the photoluminescence of porous silicon by couple orders of magnitude. The effect of photoluminescence enhancement has been observed only when the NF3 treated porous silicon was exposed to air environment. The photoluminescence intensity continued to grow with the aging time in air, even at the room temperature. Using atomic force microscope, scanning electron microscope and Auger measurements, it is found that the photoluminescence enhancement correlated with the formation of crystalline oxide layer at the porous silicon surface. This oxide layer SiOx (x≅2) is much more stoichiometric as compared to the native oxide SiOx (x≅1) covering the reference porous silicon surface (not treated by NF3). The rapid growth of the SiO2 layer is supposed to be due to the NF3/UV photo-thermal etching of the as-formed native oxide as well as to the cleaning and passivation of the porous silicon surface with fluorine.
Transport of carriers in thin Metal/PS/c-Si device Structures based on Porous Silicon
Authors: Balagurov Leonid A. , Bayliss Sue C. , Petrova Elena A. , Unal Bayram , Yarkin Dmitrii G.
Published: April 2011

Thin porous silicon (PS) based metal/PS/p-c-Si structures were prepared on moderate-and high- resistivity substrates. Measurements of current-voltage (I-V) dependencies and impedance at various temperatures were used for the investigation of carrier transport in these structures. The exponential forward bias I-Vdependencies for both types of structures spread over several orders of magnitude with a low value of quality factor (close to 2) and have activation temperature dependencies with an activation energy equal to half the c-Si band gap. The reverse current has a square root dependence on the reverse bias voltage and the activation energy is equal to half the c-Si band gap. Therefore, it was concluded that the reverse and forward currents in thin PS-based device structures were determined by the generation and recombination of carriers in the depletion region of the c-Si substrate. It was shown that a large area spreading current exists in structures made on highly resistive substrates, which appears to be due to a highly conductive inverse (n-type) layer formed in the c-Si substrate at the PS/c-Si heterojunction.
Testing of porous silicon membranes as a novel humidity sensor
Authors: Quercia L. , Noce M. Della , Ferrara V. La , Francia G. Di
Published: April 2011

A new gas sensor device based on a porous silicon membrane has been fabricated. The sensible membrane has been bonded to a 1 cm2 Al2O3 substrate [1], where electrical contacts have been previously deposited by vacuum evaporation. In this work we present the results of DC measurements showing a good response of this device to humidity gradients. In this frame, the most striking properties of our device are its selectivity and a fast and full recovery after exposure to humidity levels up to 90%. Moreover, the new fabrication process used to realize the sensor merges the advantages typical of porous silicon with thin film ones, by means of a simple process.