bluuebunny/crossref_metadata_2025 huggingface dataset:
GAS-Phase Decomposition Kinetics of MOVPE Precursors in a Counterflow Jet Reactor
Authors: Safvi S. A. , Mountziaris T. J.
Published: March 2011

A new reactor for studying the purely homogeneous thermal decomposition of organometallic precursors used in the Metalorganic Vapor Phase Epitaxy (MOVPE) of semiconductors is presented. The idea is based on the use of a counterflow jet configuration with one jet being heated and the other unheated. The heated jet contains pure carrier gas (typically hydrogen or nitrogen), while the unheated jet contains vapors of an organometallic species diluted in the same carrier gas. Under appropriate operating conditions, decomposition of the organometallic species takes place near the stagnation plane where the hot jet collides with the cool jet. Since the reactions occur in the gas phase and away from hot walls, purely homogeneous kinetics can be obtained. Such a counterflow jet reactor was designed for studying the thermal decomposition of tertiary-butyl-arsine (TBA), t-C4H9AsH2, a very promising precursor for MOVPE of GaAs films. Two-dimensional finite element simulations of transport phenomena and kinetics have been used to identify optimal operating conditions. An experimental system was constructed and capillary-sampled mass spectroscopy at the stagnation plane was used to study the thermal decomposition of TBA in nitrogen at a total pressure of 252 Torr. Gas-chromatography of the effluent gas stream was employed for positive identification of the hydrocarbon byproducts. The results indicate the existence of two major decomposition routes: (1) A low activation energy pathway producing isobutane AsH, and (2) a higher activation energy, β-hydride elimination pathway producing isobutene and arsine.
The Adsorption and Decomposition of Gallane Adducts on GaAs (100)
Authors: Foord J. S. , Wee A.T.S. , Singh N. K. , Whitaker T. J. , O'Hare D.
Published: March 2011

The adsorption and decomposition of GaH3NMe3 and GaH3PMe3 on GaAs (100) has been investigated using XPS, TDS and molecular beam techniques. Both precursors react in a similar way with the adsorbed layer formed at low temperatures decomposing as the temperature is raised to produce metallic Ga, gaseous gallium hydride(s) and adsorbed hydrogen and the Lewis base, which also undergo desorption. Molecular beam measurements show that both compounds exhibit similar decomposition kinetics and decompose more readily than the aluminium analogues. The results indicate that the site-blocking effects, which prevent the low temperature decomposition of alane adducts, are less significant for the gallane compounds.
Metallisation and Silicidation of Porous Silicon
Authors: Aylett Bernard J. , Earwaker Lyndsay G. , Keen John M.
Published: March 2011

Thin films of cobalt, rhenium, or cobalt silicide have been deposited down the pores of porous silicon layers, using HCo(CO)4, HRe(CO)5, and SiH3Co(CO)4as precursors in a Chemical Vapour Infiltration and Decomposition (CVID) technique.
Copper Films Prepared by Metal Organic Chemical Vapor Deposition (MOCVD) Process Using Copper (Acetylacetonate) and Water Vapor as Reactants: The Impact of Water Vapor
Authors: Chang Yu-Neng
Published: March 2011

By using the strong reductive potential of copper acetylacetone (Cu(acac)2) when Cu(acac)2) was thermally decomposed, copper metal films were prepared by metal organic chemical vapor deposition (MOCVD) process using sublimed Cu(acac)2 vapor and water vapor as reactants, at one atmosphere pressure. According to thermodynamic calculations, Cu films could be prepared by MOCVD process with a high ratio of partial pressures for water vapor and Cu(acac)2 vapor (PH2O/Pcu(acac)2>30) In this paper, the impacts of MOCVD processing parameters such as watervapor partial pressure, total carrier gas flow rate, and precursor partial pressure on film composition and microstructure were investigated. Deposition temperature is the primary processing parameter affecting film stoichiometry. In a specific deposition temperature window, from 370°C to 400°C, polycrystalline Cu films with Cu [111] preferential orientation were deposited. ER and XRD results indicated that films deposited at temperature lower than 350°C contain copper oxide phase with poor crystal structure. By comparing the values of X-ray Auger Electron Spectroscopy (XAES) and Auger parameter (αAu) from photoelectrons of Cu films and standards from reference compounds, die principle oxidation state of copper in these films was determined as Cu(0). The deposition results indicated that a water vapor partial pressure above 10 torr is necessary to produce Cu films. As indicated by SEM, Increasing the carrier gas flow rate, above 600 sccm, can reduce the average temperature profile in the thermal boundary layer above the substrate surface, retard the gas phase reaction rate, presumably eliminate the homogeneous nucleation, and deposit smooth Cu films.
Surface and Reactor Effects on Selective Copper Deposition from Cu(hfac)tmvs
Authors: Norman John A. T. , Roberts David A. , Hochberg Arthur K.
Published: March 2011

The selectivity of OMCVD copper films grown at 160°C/500 mTorr from the volatile liquid precursor Cu(hfac)tmvs was evaluated for various commercial 6” wafers patterned with either TiN/SiO2 or TiN/Si3N4. By processing wafers “as received”, only thermal grown SiO2 consistently resisted metallization, allowing copper films up to 1.5μ thick to be grown on TiN. For SiO2, films containing H2O, especially from PECVD, only blanket deposition was observed. However, by a utilizing simple thermal predeposition dehydration some of these SiO2 films were conditioned to give selective deposition.
Nucleation of Tungsten on Titanium Nitride with Hydrogen Reduction of Tungsten Hexafluoride
Authors: Srinivas D. , Foster R. , Marcus S. , Arora R. , Rebenne H.
Published: March 2011

In this work, a hydrogen (H2) reduction process has been developed which gives tungsten (W) nucleation on titanium nitride (TiN) adhesion layers with a very short incubation time, eliminating the need for a silane (SiH4reduced seed layer. The nucleation was found to be strongly dependent on the following factors: temperature of the substrate, total pressure in chamber, and gas introduction sequence into the reactor. Theenhanced nucleation rate has been explained based on two competing reactions: dissociation of H2, and formation of titanium subfluorides on the TiN surface.
CBE Growth of InP with Triethylindium and Metalorganic Phosphorous Precursors: Bisphosphinoethane and Tertiarybutyl-Phosphine
Authors: Chin Albert , Hersee Steve , Martin Paul , Mazurowski John , Ballingall James , Glass J. A. , Spencer James T.
Published: March 2011

Two metallorganic phosphorous precursors, bisphosphinoethane (BPE) and tertiarybutyl phosphine (TBP), were studied. For indium phosphide (InP) grown using BPE, the measured room temperature and 77K Hall mobilities were 4,200 and 22,000 cm2/Vs, with carrierdensities 5.7E15 and 4.0E15 cm−3, respectively. For InP grown using TBP, the measured room temperature and 77K Hall mobilities were 4,400 and 26,000 cm2/Vs, with carrier densities 6.4E15 and 5.1E15 cm−3, respectively. An impurity build-up at the substrate interface is responsible for the relatively low mobility in the adjacent epitaxial layers. SIMS analysis showed that S and Si are the primary impurities measured in films grown with BPE and TBP, respectively; impurity concentrations increasedwith cracking temperature. The full width at half maximum (FWHM) of donor bound exciton peaks measured by 2.2K photoluminescence for InP grown by BPE and TBP were 0.84 and 1.28 meV, respectively.
Chemical Vapor Deposition of SiC from Silacyclobutane and Methylsilane
Authors: Johnson A. D. , Perrin J. , Mucha J. A. , Ibbotson D. E.
Published: March 2011

The kinetics of SiC deposition has been studied over the temperature range 650–1050 ° C using the single-source reagents silacyclobutane (SCB) and methylsi-lane (MeSiH3 ) whose decomposition supplies the isomeric film-forming precursors H2Si = CH2 and HSiCH3, respectively. Thermal decomposition has been monitored by mass spectrometry and the SiC thin films characterized by scattering spec-trometry (RBS & ERD), FTIR spectroscopy and X-ray diffraction. Deposition rates from the two are comparable, with activation energies of 41 kcal/mole and 53 kcal/mole for SCB and MeSiH3 decomposition, respectively. Silacyclobutane deposits C-rich material lower temperatures, while SiC deposited from MeSiH3 is Si-rich at all temperatures. A mechanism for SiC CVD is proposed that is consistent with the observed kinetics and products.
Chemical Vapor Deposition of Beta Silicon Carbide Epilayers Using the Single Source Precursor 1,2-Disilylethane
Authors: Parsons J. D. , Roberts D. A. , Wu J. G. , Chadda A. K. , Chen H-S. , Hockenhull H.
Published: March 2011

A β-SiC epitaxial growth process, using 1,2-disilylethane (DES), was developed. DSE was selected because it contains an equal number of C and Si atoms and its reported decomposition characteristics suggest that C and Si could be obtained from it at approximately equal rates. Repeatable nucleation and epitaxial growth conditions, giving complete substrate coverage and controlled growth, were established by atmospheric pressure CVD, in an inverted-vertical reactor. A substrate temperature of 1290± 10°C was found to be optimum for β-SiC epilayer nucleation and growth. The maximum β-SiC epitaxial growth rate obtained was 10μms/hr. Undoped β-SiC epilayers were n-type (n≈1016 cm−3 ). DSE synthesis, CVD growth parameters, SiC deposition characteristics and β-SiC epitaxial film properties are described.
Chemical and Electrical Mechanisms in Titanium, Platinum, and Hafnium Contacts to Alpha (6H) Silicon Carbide
Authors: Porter L. M. , Glass R. C. , Davis R. F. , Bow J. S. , Kim M. J. , Carpenter R. W.
Published: March 2011

Thin films (2 Å - 1000 Å) of titanium, platinum, and hafnium were deposited via UHV electron beam evaporation at room temperature on n-type, (0001) alpha (6H)-SiC and compared in terms of interfacial chemistry, energy barriers to electrical conduction, and macroscopic electrical behavior. Current-voltage measurements have shown that these contacts are rectifying, all with ideality factors between 1.01 and 1.09. The lowest leakage currents (∼5 × 10−8 A/cm2 at -10 V) were determined for unannealed Pt contacts and for Hf contacts annealed at 700°C for 20 minutes. Current-voltage (I-V), capacitance-voltage (C-V), and x-ray photoelectron spectro-scopy (XPS) were among the techniques used to determine barrier heights, all of which were within a few tenths of an electron volt of 1.0 eV. The narrow range of calculated barrier heights along with the XPS valence spectrum of the chemically prepared SiC surface give evidence that the Fermi level is pinned at the semiconductor surface.
Oxygen Atom Induced Deposition of Silicon Dioxide
Authors: Levedakis Dimitri A. , Raupp Gregory B.
Published: March 2011

Silicon dioxide was deposited from tetraethylorthosilicate (TEOS) and remote microwave oxygen plasma on a heated silicon substrate in a cold-wall reactor. The deposition rate and film quality were examined as functions of substrate temperature, total pressure, absorbed plasma power and O2:TEOS flow ratio. The deposition reaction exhibited an activation energy of approximately 10 kJ/mol for substrate temperatures in the range of 323–623 K. The deposition rate reached a maximum with increasing total pressure. The rate was found to be a near-linear function of the absorbed microwave power. At fixedabsorbed power the rate reached a maximum with increasing O2:TEOS flow ratio. A one-dimensional mathematical model was developed to predict the oxygen radical concentration at the exit of the afterglow region of the oxygen discharge. Comparisons of the predicted oxygen radical concentrations with the deposition rates at corresponding deposition conditions supports the view that the overall SiO2 deposition reaction is largely controlled by the concentration of oxygen radicals. The average refractive index ofthe deposited films was 1.466 ± 0.011. Fourier transform infra-red (FTIR) transmission spectra showed significant concentrations of hydroxyls in the deposited films.
Reactive Scattering of Si2 H6 from the Si(100) Surface
Authors: Hansen D. A. , Furjanic M. J. , Xia L.-Q. , Engstrom J. R.
Published: March 2011

The reaction of Si2H6 with the Si(100) surface has been examined via supersonic molecular beam scattering techniques. The effects of incident translational energy, incident angle, mean vibrational energy and surface temperature have been considered explicitly. It is found that the reaction probability is most sensitive tothe incident translational energy, varying nearly linearly with increasing energy. The effect of incident angle θi can be accounted for by an energy scaling law that is given approximately by cosnθi, where n ∼ 1.
Growth of GaN, AlN and InN by Electron Cyclotron Resonance-Metal Organic Molecular Beam Epitaxy
Authors: Wisk P. W. , Abernathy C. R. , Pearton S. J. , Ren F. , Lothian J. R. , Katz A. , Jones K.
Published: March 2011

We have investigated the feasibility of depositing GaN, AIN and InN from nitrogen plasmas by electron cyclotron resonance-metal organic molecular beam epitaxy (ECR-MOMBE). Growth rate, morphology, and resistivity were evaluated as function of growth temperature and group IB flux. It was found that stoichiometric materials could be deposited at reasonable growth rates on either GaAs or sapphire substrates. Low contact resistance, ∼5 × 10−7 Ω-cm2, can be obtained on In due to the high carrier concentrations, 1020 cm−3 obtained in this material.
The Decomposition Chemistry of an AlN Precursor Bis-Dimethylaluminum Deutero-Amide, [(CH3)2AlND2]3, as Revealed by Time-of-Flight Molecular beam mass Spectrometry
Authors: Amato Carmela C. , Hudson John B. , Interrante Leonard V.
Published: March 2011

A molecular beam mass spectrometer coupled to the inlet portion of a hot-wall CVD reactor has been used to measure the time-of-flight (TOF) distribution of molecules sampled from the reactor. The molecular weights of the species in the reactor can be determined from test TOF distributions. This technique has been used to identify the gas phasespecies present in a hot-wall reactor during the CVD of A1N using bis-dimethylaluminum deutero-amide,[(CH3)2AlND2]3 (I), as the precursor. Evidence has been found for: deuterated methane, CH3D, trimeric form of the precursor I, and its dimeric form. TOF evidence also supports the presence of an oligomer of I with a pentameric structure, as well as a number of substituted versions of trimer and dimer. Mechanisms have been formulated that explain methane elimination from the precursor as well as the formation of all species observed.
Strained Quantum Dots in Porous Silicon
Authors: Zhao Xue-Shu , Persans Peter D. , Schroeder John , Wu Yeun-Jung
Published: March 2011

On the basis of Raman, photoluminescence, and absorption studies of porous and nanoparticle silicon we propose that the strong luminescence in porous silicon results from strained silicon quantum dots. A silicon nanoparticle is a special Jahn-Teller system induced by extended electron states rather than localized state. Thus Raman scattering and photoluminescence in porous silicon are multi-phonon assisted free electronic transition processes, all observed anomalous properties of porous silicon can be clearly explained by using this strained quantum dot model.
Picosecond Decay Dynamics in Porous Silicon
Authors: Matsumoto T. , Futagi T. , Mimura H. , Kanemitsu Y.
Published: March 2011

Picosecond decay dynamics of luminescent porous silicon has been studied using the second harmonics (SH) of a cw modelocked YLF laser and a synchroscan streak camera. Picosecond luminescence decay shows nonexponential behavior that becomes large with decreasing emission energy. When increasing hydrogen termination on the surface of a Si microcrystal occurs, this picosecond luminescence decay becomes faster. Our experimental results indicate that there are two luminescent states in porous Si : a weak luminescent quantum confinement state and a strong luminescent surface localized state.
Study of Photoluminescent thin film Porous Silicon on Sapphire
Authors: Dubbelday W. B. , Szaflarskf D. M. , Shimabukuro R. L. , Russell S. D.
Published: March 2011

Photoluminescence in porous silicon on sapphire (SOS) prepared through chemical staining and photo-initiated chemical etch is demonstrated. SOS consists of single crystal quality material on a transparent substrate through which photoluminescence can be excited and observed. Porous silicon films as thin as 270 nm are shown to photoluminesce. This study explores the effect of varying film thickness and crystal quality on the photoluminescent emission from porous silicon. Introduction of crystal defects by ion implantation is used to create controlled damaged layers prior to fabricating porous silicon. No photoluminescence is observed from chemically stained or electrochemically etched amorphized layers. Corroborative results are obtained using LPCVD deposited amorphous silicon layers.
Fast Photoluminescence from Porous Silicon
Authors: Petrova-Koch V. , Muschik T. , Kovalev D. I. , Koch F. , Lehmann V.
Published: March 2011

Time-resolved studies of the visible photoluminescence in porous silicon with three different coverages of the internal surface are reported. We use aged, naturally oxidized porous Si (oxihydride), rapid thermal processed material (oxide) and samples stored in HF (pure hydride). A new, fast luminescence band in the blue-green spectral range and with response time less than 100 ns is observed at room temperature in each of the samples, although with different intensities. The observations prove that this is not an oxide-defect luminescence. We speculate on mechanisms for the origin of the fast luminescence in nanometer-size crystallites of Si.
Structural Investigation of Electrochemically Etched Silicon
Authors: Heuser B. J. , Spooner S. , Glinka C. J. , Gilliam D. L. , Winslow N. A. , Boley M. S.
Published: March 2011

Small-angle neutron scattering (SANS) measurements of four electrochemically etched, porous silicon (PS) samples have been performed over a wide wavevector transfer (Q) range. The intermediate to high Q results can be modeled with a non-particulate, random phase model. Correlation length scales on the order of 1 to 2 nm thought to characterize the PS skeleton have been deduced from the SANS data. The microstructural anisotropy was studied tilting two of the samples with respect to the neutron beam. These samples exhibited an asymmetric scattering pattern at intermediate Q (0.1 ≤ Q ≥ 0.6 nm-1) in this condition. Photoluminescence spectra from all four samples have been recorded as well. A correlation appears to exist between the SANS and photoluminescence measurements. An x-ray diffraction measurement of one sample demonstrates that the PS layer retains the silicon lattice structure. Significant peak broadening is observed that we interpreted as a quasi-particle size effect The PS particle size calculated from the x-ray diffraction measurement is equal to the correlation length obtained in the SANS measurement.
Photochemical Etching Effects on Optical Properties of Porous Silicon
Authors: Kanemitsu Y. , Uto H. , Masumoto Y. , Matsumoto T. , Futagi T. , Mimura H.
Published: March 2011

We have studied effects of hydrogen-termination on optical properties of porous Si. The hydrogen concentration in the samples was controlled by photochemical etching after the electrochemical anodization. Transmission electron microscopy examination shows that the size of Si crystallites in porous silicon ranges from 3 to 10 nm and no significant size changes occur by the photochemical etching process. The PL spectra, the PL excitation spectra, and the picosecond PL decay rate were sensitive to the photochemical etching process. Spectroscopic analysis suggests that the radiative recombination occurs at the near-surface region of the Si crystallites.
Investigation of Porous Silicon Films Structure by Optical Methods
Authors: Basmaji P. , Grivickas V. , Surdutovich G. I. , Vitlina R. , Bagnato V. S.
Published: March 2011

The structure of aged porous silicon (PS) has been investigated using reflectivity, photoluminescence (PL), optical absorption and photoconductivity decay. An optical anisotropy in a perpendicular to surface direction is observed for PS samples below a critical porosity of 70%. The photostability of the PL spectra imply three different structures of PS, these should be attributed to quantum size structures, polymeric type structures and fluor-related structures. The absorption edge is deconvoluted into a band-to-band absorption with energy ranging between Eg = 1.6–2 eV and an absorption shoulder at hu ≤ Eg. The high energy PL band around 2.3 eV resembles that of fluoroindate glass. The observed rapid lifetime at high injection level is attributed to excitonic Auger-type recombination.
Rapid Photoluminescence Intensity Degradation in Porous Silicon
Authors: Basmaji P. , Bernussi A. A. , Rossi J. C. , Matvienko B.
Published: March 2011

Rapid photoluminescence intensity degradation are observed in porous silicon layers formed at different preparation conditions. The decay rate, ranging from 0.5 to tens of seconds, is found to be a function of illumination intensity, sample temperature and emission wavelength. We attributed the degradation effect to photochemical reactions on the surface.
Light Emission from Porous Silicon Subjected to Rapid Thermal Oxidation
Authors: Cullis A. G. , Canham L. T. , Williams G. M. , Smith P. W. , Dosser O. D.
Published: March 2011

Luminescent oxidised porous Si is produced by rapid thermal annealing of the anodised material in a dry oxygen ambient. Its light-emitting properties are studied by both photoluminescence and cathodoluminescence methods. The structure of the oxidised material is examined by transmission electron microscopy, while its oxygen content is determined by X-ray microanalysis. These investigations show that crystalline Si nanostructures remain in the oxidised porous material and account for its luminescence properties. The work demonstrates that the speculated importance of either Si-based amorphous phases or the interesting material, siloxene, in this regard is unrealistic.
The Effect of Lewis Base Chemisorption on the Luminscence of Porous Silicon
Authors: Coffer Jeffery L. , Lilley Sean C. , Martin Rebecca A. , Files-Sesler Leigh Ann
Published: March 2011

We report here studies on the effects of Lewis base addition on the observed luminescence of porous silicon generated non-anodically from a stain etch of <100> p-type wafers and whose surface morphology has been characterized by atomic force microscopy (AFM). Addition of dilute heptane solutions of alkyl amines such as n-butyl amine (C4H7NH2) results in dramatic quenching of the steady-state photoluminescence (PL) near 625 nm. The observed fractional changes in integrated PL intensity as a function of amine concentration have been fit to a simple equilibrium model demonstrating Langmuir-type behavior from which adduct formation constants have been calculated. These steady-state PL measurements are complemented by Fourier Transform Infrared (FT IR) spectroscopic measurements monitoring the effect of amine adsorption on the silicon hydride stretching modes [v(Si-Hx)] near 2100 cm-1. Based on these results, a physical model for the amine interactions with the porous silicon surface is presented.
New Results on Electroluminescence from Porous Silicon
Authors: Steiner Peter , Kozlowski Frank , Sandmaier Hermann , Lang Walter
Published: March 2011

First results on light emitting diodes in porous silicon were reported in 1991. They showed a quantum efficiency of 10-7 to 10-5 and an orange spectrum. Over the last year some progress was achieved:

- By applying UV-light during the etching blue and green light emitting diodes in porous silicon are fabricated.

- When a p/n junction is realized within the porous region, a quantum efficiency of 10-4 is obtained.
Porous Silicon-Based Optoelectronic Devices: Processing and Characterization
Authors: Kalkhoran Nader M.
Published: March 2011

A patterning process compatible with conventional Si electronics technology, which has resolution better than 5 μm, has been developed in order to perform selected-area anodic etching for producing luminescent porous Si layers (PSL). Correlations between the anodic etching and photolithographic parameters have been identified, and their effects on the resolution and luminescence of porous Si layers have been studied. Finally, the first monolithic processing, i.e., true wafer-scale integration, of a Si-based visible light-emitting diode (LED) and a photodetector using conventional Si technology has been demonstrated.
Quantum Confinement Effects on the Dielectric Constant of Porous Silicon
Authors: Tsu R. , Ioriatti L. , Harvey J. F. , Shen H. , Lux R. A.
Published: March 2011

The reduction of the dielectric constant due to quantum confinement is studied both experimentally and theoretically. Angle resolved ellipsometry measurements with Ar- and He-Ne-lasers give values for the index of refraction far below what can be accounted for from porosity alone. A modified Penn model to include quantum size effects has been used to calculate the reduction in the static dielectric constant (ε) with extreme confinement. Since the binding energy of shallow impurities depends inversely on ε2, the drastic decrease in the carrier concentration as a result of the decrease in ε leads to a self-limiting process for the electrochemical etching of porous silicon.
Composition and Structure of Spark Eroded Porous Silicon
Authors: Hummel R. E. , Chang S.-S. , Ludwig M. , Morrone A.
Published: March 2011

Porous silicon which has been prepared by a “dry” technique, that is, by spark erosion, yields similar photoluminescence spectra as anodically etched porous silicon which has been prepared in aqueous solutions. Fourier transform infrared spectra reveal that the dominant features in spark eroded silicon are the Si-O-Si stretching mode and the Si-O-Si bending mode. No infrared vibrational modes characteristic for siloxene have been found in spark eroded Si. Results from X-ray and electron diffraction studies suggest that spark eroded Si involves minute polycrystalline silicon particles which are imbedded in an amorphous matrix.
Carrier Transport Through Grain Boundaries in Hydrogenated Microcrystalline Silicon
Authors: Grebner S. , Wang F. , Schwarz R.
Published: March 2011

To analyse the influence of the grain boundaries (gb) on the transport of carriers in hydrogenated microcrystalline silicon (μC-Si:H) the ambipolar diffusion length (LLMB) was measured by SSPG. In addition, the films were characterised by photo-conductivity, dark conductivity activation energy, Urbach energy (determined by CPM), hydrogen effusion, Raman spectroscopy, X-ray scattering and optical transmission.

The sample series was prepared by PECVD of SiH4 diluted with increasing H2 content. Taking the structural information by Raman spectra and X-ray into account, we explain our optical and activation energy measurements within a three-phase-model (amorphous phase, crystalline phase, gb) and a Fermi level pinning in μc-Si:H.
Spectroscopic Ellipsometry and Interference Reflectometry Measurements of CVD Silicon Grown on Oxidized Silicon
Authors: Jellison G. E. , Keefer M. , Thornquist L.
Published: March 2011

Several samples of thin-film silicon grown on oxidized Si, both oxidized and unoxidized, have been examined using spectroscopie ellipsometry (SE) and constant angle reflection interference spectroscopy (CARIS). The SE data was fit to 5- or 6- layer models of the sample near-surface region, using the optical functions of thin-film silicon determined from a previous work. Reasonable fits were obtained from samples containing amorphous Si (a-Si) or large-grain poly-crystalline Si (p-Si), but fits to samples containing small-grain, undoped p-Si were poor unless a 8–15 nm surface roughness layer is included. Furthermore, the optical functions of p-Si:ud are not consistent from sample to sample. The optical functions determined from SE measurements were then used to interpret CARIS measurements, extracting the thicknesses of the films, which are then compared with the thicknesses obtained from SE.
A Particular Structure of B-doped μc-Si/a-Si:H Layers on Insulator
Authors: Le Berre M. , Lemiti M. , Pinard P. , Bustarret E. , Grieshaber W. , Bruyère J.-C. , Brunei M.
Published: March 2011

Microcrystalline films of thicknesses ranging from 0.3 to 1.1 μm have been deposited on oxidized silicon wafers by PECVD in a 50KHz capacitive discharge reactor at 450°C. Two series of films have been elaborated over a wide range of boron concentrations at the same H2:SiH4 ratio of 9:1. Cross section TEM micrographs showed the films to consist of two sublayers of distinct crystalline nature, whose relative thickness depends on the preparation conditions. With a strongly <220> textured microcrystalline structure, the overlayer snowed a columnar morphology, while the amorphous underlayer reached thicknesses of 350nm. Two additional striking features were observed by TEM: - The grains took two symmetrical orientations relative to the preferential [220] growth axis;- The interface between the amorphous and crystalline regions had a sawtooth pattern with a period around 300nm. In contrast to these microstructural results, the B-profile as measured by SIMS was found to be fiat accross the whole thickness. These local measurements are compared to the results of grazing X ray diffraction and Raman measurements. We observe and discuss a discrepancy between the X ray coherence length and the dimensions of the columns as observed by TEM. While optimized conditions lead to a vanishing amorphous sublayer, the more original features described above are tentatively interpreted taking into account the high compressive strains in the layers deposited at low plasma frequencies.
TEM Study and Hall Measurement of nc-Si Prepared by Controlled Deposition
Authors: Nakata Masami , Shimizu Isamu
Published: March 2011

We report the results of a study in which we combined growth experiments with measurements of the nc-structure and of electrical transport Samples were prepared by plasma enhanced-CVD using SiF4 and H2 gases. We also added PH3 and H2 as control parameters for structural change. The microscopic structure was directly observed by TEM. Electron transport in nc-Si was investigated by Hall effect measurements performed at temperatures from 100K to 400K. We produced samples in which the Hall mobility was applied from general transport mechanism of poly crystalline silicon. However, from TEM observation, we conclude that dominant factor on electrical transport strongly depends on the sample structure, and nanocrystalline-silicon structure is so varied as to make it difficult to determine the transport mechanism without the observation of the microscopic structure.
Low Temperature Fabrication of Poly-Si TFTs using in-situ Chemically Cleaning Method
Authors: Kono Naoki , Nagahara Tatsuro , Fujimoto Kenji , Kashiwagi Yusaku , Kakinoki Hisashi
Published: March 2011

Thin film transistors were fabricated using polycrystalline silicon (poly-Si) film which were directly deposited on Corning 7059 glass substrates by plasma chemical vapor deposition method at very low temperature of 450°C. No annealing procedure was carried out in the fabrication process. The dependences of the crystallinity and the electrical properties on the poly-Si film thickness were investigated for three kinds of films deposited under different conditions. These dependences on the film thickness were found to be strongly influenced by the deposition condition, especially the reaction gas pressure. By choosing optimum poly-Si deposition condition carefully, high performance TFTs have been fabricated by this novel method.
Pulsed-Laser Annealing of Silicon Films
Authors: Sameshima T.
Published: March 2011

Phase transition between crystalline and amorphous states was studied through 30ns-pulsed XeCl laser induced melting of silicon films. Crystallization occurs through interface controlled growth for laser energy above surface melting threshold. Grain size is smaller than lOOnm because of short melt duration (<80ns). Amorphization is observed in silicon films thinner than 40nm when the silicon films are completely melted then solidified homogeneously. The amorphized films have a large defect density (∼1020cm-3eV-1), which is remarkably reduced by hydrogen plasma treatment for 1 minute. This paper also discusses the application to fabrication of thin film transistors with a high carrier mobility (>100cm2/Vs) at a low temperature of 250°C.
High-Quality Polycrystalline Silicon thin Films Prepared by Solid Phase Crystallization (Spc) Method
Authors: Matsuyama T. , Baba T. , Tanaka M. , Tsuda S. , Nishiwaki H. , Nakano S. , Hanafusa H. , Kuwano Y.
Published: March 2011

The relationship between the grain size of poly-Si after SPC and the structure of a-Si before SPC was studied. The structure of a-Si was characterized by TA/TO: the Raman intensity ratio of the Transverse Acoustic (TA) like band and the Transverse Optical (TO) like band. A good positive correlation between the grain size and TS/TO was revealed for the first time. The nucleation and growth kinetics were speculated by using a thermodynamic model. The grain size could be enlarged up to 6 μ m by applying textured substrates to a-Si with a large structural disorder. This film was applied to the active layer of solar cells, and a collection efficiency of 51% at 900 nm was obtained.
Origin of Blue Shifts in Quantum-Well Wires Unrelated to Lateral Confinement
Authors: Gustafsson Anders , Liu X. , Maximov I. , Samuelson L. , Seifert W.
Published: March 2011

Experimentally observed blue shifts of the peak position of the luminescence from quantum-well-wire and -dot structures are often significantly larger than the calculated shifts induced by lateral confinement in the structures. In this work we have used high-quality InGaAsAnP multi-quantum-wells for the fabrication of wires. The quantum wells are in the range 3 to 17 monolayers (ML) nominally. The thinnest well, 3 ML, shows a clearly resolved split into two luminescence peaks from areas with a thickness difference of 1 ML. In the case of the wires, the luminescence from the thicker wells show a blue shift, as well a significant broadening. However, the thinnest well shows no blue shift, but a different ratio of the two peaks, with the high energy peak favoured in the wire case. We interpret these effects in terms of a reduced transfer of excitons from thinner to thicker areas of the well in the wire as compared to the unpattemed areas. This due to a reduction of the transfer from 2 dimensional to 1 dimensional in the wires. The peaks originating in areas of different ML thicknesses are not spectrally resolved in the thicker wells and the reduced transfer therefore results in a blue shift as well as a broadening of the luminescence peak.
Electron Relaxation in Multisubband GaAs Quantum Wire
Authors: Leão Salviano A. , HipóLito Oscar , Peeters François M.
Published: March 2011

The intra-and intersubband scattering rates for emission and absorption of longitudinal optical (LO) phonons by electrons confined in a cylindrical GaAs-GaAlAs quantum wire are calculated. Multiple peaks due to intersubband transitions appeared on the total scattering rate as a function of the electron energy.
Third-Order Optical Nonlinearities of Quantized CdS and Metal Ultrafine Particles Co-Dispersed in Polymer Matrices – Surface Modification Effect
Authors: Yao Hiroshi , Hayashi Toyoharu
Published: March 2011

Quantized CdS particles of about 60 A in diameter were prepared by an organo-sol method in the presence of PVP (poly(N-vinyl-2-pyrrolidone)), and this new method could make the CdS ultrafine particles densely dispersed in PHEMA (poly(2-hydroxyethyl methacrylate)) host films. The values of | x(3) |/α (third-order optical nonlinear susceptibility per unit absorption coefficient) were obtained (2.0 × 10-10 esu· cm at 460 nm and 2.7 × 10-10esu · cm at 470 nm) using a nanosecond DFWM technique. An enhancement of non-linearity was observed for the first time when Ag particles or Ag+ ion were co-dispersed with the CdS particles in small amounts. The addition of 8.57 wt% Ag particles, or 4.28 wt% Ag+ ion in the ratio to CdS made | x(3) |/α enhanced to be 3.9 × 10-10 esu· cm, or 4.1 × 10-10 esu· cm, respectively. The surface modification by the formation of Ag2S on the surface of CdS colloids is believed to be responsible for this enhancement.
Blue Light Emission from Porous Silicon
Authors: Hou X. Y. , Shi G. , Wang W. , Zhang F. L. , Hao P. H. , Huang D. M. , Jin X. F. , Wang Xun
Published: March 2011

Through a post treatment of light emitting porous silicon in boilingwater, a large blue shift of its photoluminescence (PL) spectrum hasbeen observed and a stable blue-green light emission at the peak wavelength down to 500 nm is achieved. The effect of boiling water treatment is suggested to be a kind of oxidation, which could reduce thesize of the Si column, fill up some micropores and strengthen the Siskeleton. The photoluminescence microscopic observation shows that the surface of blue light emitting porous silicon is composed of manysmall uniformly light-emitting domains at the size of several tens of μm. Fourier transform infrared reflection (FTIR) measurements show that the formation of Si-H bonds is not responsible for the visible luminescence in the very thin Si wires.
Optical Properties of Colloidal MoS2
Authors: Wagoner G. A. , Persans P. D. , Ruppert A. F.
Published: March 2011

We report measurements and analysis of the optical transmission spectra of colloidal 2H-M0S2. prepared by ultrasonic shattering of synthetic crystals in N-Methyl Formamide. We used a combination of TEM, X-ray diffraction and dynamic light scattering to characterize particle shape and size. For a typical sample, the particles are platelets which have an average thickness of 50 Å and a diameter of 500 Å. Particle dielectric functions, deduced from both dilute colloids and thin films prepared by flocculaUon, differ significantly from bulk values. Calculations show that the average extinction coefficient is affected by particle aspect ratio, but this can not explain all the features of the data. Specifically, we observe a suppression of the absorbance peaks in the band edge exciton region between 1.7 and 2.1 eV, and increased absorbance below 1.7 eV. We suggest that the particles do not possess bulk-like dielectric properties and that tins is due to defects.
Microcharacterization of CuInSe2 Grown by Coevaporation and Selenization
Authors: Bode M. H. , Al-Jassim M. M. , Tuttle J. , Albin D.
Published: March 2011

Thin films of CuInSe2, grown by coevaporation or by selenization of a Cu-In precursor, were analyzed in a scanning transmission electron microscope. While the coevaporated film shows clear evidence of second phases (Cu2Se) around the individual grains, no second phases could be found in the selenized material. Structural characterization also showed the presence of two ordered phases in the coevaporated films, the ordered-vacancy compound CuIn2Se3.5, and a CuPt-ordered phase of CuInSe2.
Rapid Thermal Annealing of Spin-On Glass Films
Authors: Ventura Laurent , Hartiti Bouchaíb , Slaoui Abdelilah , Muller Jean-Claude , Siffert Paul
Published: March 2011

Rapid thermal annealing is investigated for curing spin-on glass insulating films. The annealed SOG films were mainly evaluated using infrared absorption spectroscopy and by electrical measurement of the defects present at the Si/Sio2 interface. We found in particular after rapid thermal annealing an important densification of the layers as a function of temperature and a reduction of the interfacial state densities which are comparable to classical thermal oxides.
Voltage, Fluence, and Polarity Dependence of Trap Generation Inside of Thin Silicon Oxide Films
Authors: Scott Ronald S. , Dumin David J.
Published: March 2011

The tunnelling front model has been used to obtain the spatial distribution of high-voltage, stress generated traps inside of MOS capacitors. It was found that the number of traps created by high voltage stress was proportional to the cube root of the fluence through the oxide during the stress. Measurement of the trap generation rate indicated that fewer traps were being created as higher amounts of charge were passed through the oxide. Further tests indicated that there was a voltage dependence to the trap generation which was independent of stress polarity.
Stress Induced Increased Low Level Leakage in Thin Oxides
Authors: Dumin D. J. , Maddux J. R. , Wong D.-P.
Published: March 2011

It has been observed that the low-level, pre-tunneling currents through thin gate oxides increased after the oxides had been stressed at high voltages. The number of traps inside of the oxide generated by the stress has been shown to increase as the 1/3 power of the fluence that had passed through the oxide during the stress. The increases in the low-level, pre-tunneling currents have been shown to be proportional to the number of stress generated traps in the oxide and not to the fluence during the stress. The voltage dependences of the excess low-level leakage currents were stress and measurement polarity dependent. Attempts have been made to fit the voltage dependences of the excess low-level currents to Fowler-Nordheim tunneling, Frenkel-Poole conduction or Schottky barrier lowering. The increase in the portion of the low-level, pre-tunneling current that was not dependent on stress/measurement polarity sequence was best fit using Schottky emission currents. The model that has been developed to describe the increases in the low-level currents has centered on trap-assisted currents through the oxides.
Development of Aluminum Gate Thin-Film Transistors Based on Aluminum Oxide Insulators
Authors: Tsukada Toshjhisa
Published: March 2011

Development of aluminum gate thin-film transistors (TFT) is described. This TFT is fabricated based on an aluminum oxide insulator technology, in which aluminum is anodically oxidized to form Al2O3. The use of aluminum is effective in reducing the delay of the gate busline of the display panels due to its low resistivity. The Al2O3 films formed by an anodic oxidation, block the growth of hillocks during TFT fabrication which is one of the biggest issues of aluminum metallization. With this technology it is possible to design and fabricate TFT/LCD panels larger than 30 inches and with more than 1000 scan lines.
High Channel Mobility a-Si:H Thin Film Transistors with Oxide/Nitride Dielectrics
Authors: He S. S. , Stephens D. J. , Lucovsky G. , Hamaker R. W.
Published: March 2011

We describe: i) nitride-layer optimization; ii) device fabrication: and iii) electrical properties of a-Si:H thin film transistors, TFTs, that integrate oxide/nitride dielectrics into an inverted, staggered gate structure. We have systematically changed the concentrations of Si-Si, Si-H and Si-NH bonding groups within the deposited nitride layers by varying the source gas flow ratio, R = NH3/SiH4 from 2.5 to 12.5. The electrical characteristics of the TFTs improve significantly as the gas phase ratio R is increased from 2.5 to approximately 10, and then decrease as R is further increased. The performance of the TFTs peaks for a source gas ratio of -10, where the channel mobility is ∼1.4 cm2/V-s, the threshold voltage is 2.3 V; and the Ion to Ioff current ratio is > 105.These increases in performance can only realized in devices in which the back of the Si channel region is passivated with an oxy-nitride interfacial region.
Electrical Properties of Tantalum Based Composite Oxide Films
Authors: Kattelus Hannu , Ylilammi Markku , Salmi Jorma , Ranta-Aho Timo , Kanen Erjany , Suni Andilkka
Published: March 2011

Tantalum oxide is a widely used insulator in electronic applications requiring high permittivity. When deposited at low temperature, tantalum oxide films, however, often exhibit large leakage current. A common way to reduce leakage is to anneal the films in an ambient containing extremely reactive oxygen species, or at high temperature in dry oxygen. A different approach is to use composite oxide materials. We have studied layered tantalum based oxide films deposited by Atomic Layer Epitaxy, and observed that the leakage current is decreased by several orders of magnitude when a fraction of tantalum oxide is replaced by another oxide, such as aluminum or hafnium oxide. Leakage current density of 40 nA/cm2 in the electric field of 1 MV/cm is attained for unannealed Ta-Hf-O film deposited at 300°C. Layered composite insulators are an interesting new class of materials, and ALE proves to be a useful method for depositing them.
Electrical Properties of Ferroelectric Thin Film Capacitors with Different Structures
Authors: Jia Q. X. , Yi J. , Shi Z. Q. , Ho K. K. , Chang L. H. , Anderson W. A.
Published: March 2011

Ferroelectric BaTiO3 thin film capacitors were fabricated using different designs. Silicon wafers with an oxide layer were used as the substrates. Conductive metallic oxide of RuO2 was reactively sputtered on SiO2/Si as a bottom electrode. The BaTiO3 thin films with a thickness in the range of 150–300nm were deposited by RF magnetron sputtering. Different capacitor structures, including single layer amorphous, single layer polycrys-talline, and bi-layer amorphous on polycrystalline, were investigated in this study. The clear interface between BaTiO3 and RuO2 as demonstrated by cross-sectional scanning electron microscopy implies little interdiffusion. The DC conducticity of a film with a thickness of around 200nm was as low as 1×10−13OHgr-cm at 4V. The dielectric constant of the composite structure was controlled in a range from 30 to 130. Breakdown voltage varied from 5×105V/cm to 1×106V/cm.
Non-Contact Real-Time Evaluation of Polyimide Thin Film Thermoelastic Properties Through Impulsive Stimulated Thermal Scattering
Authors: Rogers J. A. , Duggal A. R. , Nelson K. A.
Published: March 2011

We demonstrate a new purely optical based method for the excitation and detection of acoustic and thermal disturbances in thin films. This technique is applied to the determination of the viscoelastic properties of unsupported and silicon supported polyimide thin (∼1 micron) films. We show how this technique can be used to detect film delaminations and suggest how it may be used to probe film-substrate adhesion quality.
Polysilicon and Simox Characterization Using Spectroscopic Ellipsometry
Authors: Asinovsky L. M.
Published: March 2011

Spectroscopic ellipsometry has been used to characterize Poly-Si, prepared with the bulk LPCVD technology and SIMOX samples. SIMOX samples were prepared by implantation of the oxygen ion (≈ 1.8×1018ions/cm2 at 200keV) of the c-Si substrate and annealing at 1300°C for 5 h. The measurements were taken at angles of incidence of 65 and 70 degrees in the wavelength range from 260 to 860 nm. The analysis of the data identified the presence of the inhomogeneity in the poly-Si layer and slight deviation of the Si layer optical constants spectra from that of the c-Si in the SIMOX sample. A method is presented that provides a step by step procedure for interpretation of the spectroscopic ellipsometry measurements.