bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Compensation Mechanism of Amorphous Silicon Films: Study of Stability
Authors: Caputo D. , De Cesare G. , Palma F. , Tucci M. , Minarini C. , Terzini E.
Published: April 2011

We investigated a-Si:H compensated materials deposited over a wide range of gas dopant concentrations, from 0.125 ppm up to 103 ppm.

We achieved compensation for different ratio in the gas phase of diborane and phosphine, depending on their concentration. As a relevant result, we found that at constant boron concentration compensation occurs by using two different values of phosphine flow. This behavior can be described by a change of formation mechanism involving active dopants, defects and boron-phosphorus complex, that occurs in a different way depending on the dopant concentrations.

The two compensation regimes are evidenced also by a different behavior under light soaking. Furthermore we found that photocurrent evolution under illumination is determined by two concurrent mechanisms: activation of dopant species and increase of defect density.
Amorphous/Crystalline Silicon Two Terminal Visibleænfrared Tunable Photodetector: Modeling and Realization
Authors: De Cesare G. , Irrera F. , Tucci M.
Published: April 2011

Difference in the absorption coefficient profile of the amorphous and crystalline silicon is the key idea for the realization of a new visible/infrared tunable photodetector (VIP). The device consists on a n-doped a-Si:H/intrinsic a-Si:H/p-doped a-SiC:H multilayer grown by PECVD on a p-type crystalline silicon wafer doped by a phosphourus diffusion. A grid-shaped aluminum front contact with transparent conductive oxide coating is used as window for the incident light. Tunable sensitivity in the visible and near infrared spectral range can be achieved under different values of the external voltage, with excellent spectral separation between the two quantum efficiencies peaks at 480 nm and 800 nm.

A simple analytical model taking into account the absorption profile, diffusion and drift lengths, and layer thicknesses reproduces fairly well the experimental results.
Growth and Characterization of In-Based Nitride Compounds and their Double Heterostructures
Authors: Joshkin V. A. , Roberts J. C , Piner E. L. , Behbehani M. K. , McIntosh F. G. , Wang L. , Lin S. , Shmagin I. , Krishnankutty S. , Kolbas R. M. , El-Masry N. A. , Bedair S. M.
Published: April 2011

We report on the growth and characterization of InGaN bulk films and AlGaN/InGaN/AlGaN double heterostructures (DHs). Good quality bulk InGaN films have been grown by metalorganic chemical vapor deposition (MOCVD) with up to 40% InN as characterized by x-ray diffraction. The effect of hydrogen in the growth ambient on the lnN% incorporation in the InGaN films is presented. Photoluminescence (PL) spectra of AlGaN/InGaN/AlGaN DHs exhibit emission wavelengths from the violet through yellow depending on the growth conditions of the active InGaN layer. The PL spectra are fairly broad both at room temperature and 20 K, and could be a result of native defects or impurity related transitions. We also observed a linear dependence between the PL intensity and excitation power density in the 0.001 W/cm2 to 10 MW/cm2 range. Time resolved PL of one of these DHs suggest a recombination lifetime on the order of 520 ps.
Growth of Bulk, Polycrystalline Gallium and Indium Nitride at Sub-Atmospheric Pressures
Authors: Angus John C. , Argoitia Alberto , Hayman Cliff C. , Wang Long , Dyck Jeffrey S. , Kash Kathleen
Published: April 2011

Bulk, polycrystalline gallium nitride and indium nitride were crystallized at sub-atmospheric pressures by saturating the pure metals with nitrogen from a microwave electron cyclotron resonance source. Saturation of Ga/In melts with nitrogen led only to the crystallization of gallium nitride. The polycrystalline samples were wurtzitic. The gallium nitride was well faceted, with narrow Raman lineshapes, and showed near-band-edge and yellow band photo-luminescence at both 4K and 300K. The indium nitride was formed in smaller amounts, was less well faceted, and showed no photoluminescence.
Dependence of the Residual Strain in GaN on the AlN Buffer Layer Annealing Parameters
Authors: Le Vaillant Y.-M. , Ciur S. , Andenet A. , Briot O. , Gil B. , Aulombard R. L. , Bisaro R. , Olivier J. , Durand O. , Duboz J.-Y.
Published: April 2011

The problem of residual strain in GaN epilayers is currently the attention of many studies, since it affects the optical and electrical properties of the epilayers. In order to discuss the origin of this residual strain, we have grown a series of GaN epilayers onto AlN buffer layers, sapphire (0001) being used as substrate. The buffer layer is usually deposited in an amorphous state and is recrystallized by a thermal annealing. Here we have made a systematic study of the buffer recrystallization by changing the annealing temperature and the annealing time. The surface morphology is probed using Atomic Force Microscopy (AFM). The lattice parameter c is carried out from accurate x-ray diffraction measurements. The GaN layers were studied by low temperature photoluminescence and reflectivity. The amount of residual strain is calibrated from the position of the A exciton and the optical quality of the layers is assessed from the photoluminescence linewidths. The longer the annealing time the better the strain relaxation in AlN buffer layers and the higher the lattice mismatch with GaN overlayers.
Plasma Cleaning and Nitridation of Sapphire Substrates for AlxGa1-xN Epitaxy as Studied by ARXPS and XPD
Authors: Seelmann-Eggebert M. , Zimmermann H. , Obloh H. , Niebuhr R. , Wachtendorf B.
Published: April 2011

The influence of plasma and thermal treatments on the structure and composition of sapphire (00–1) surfaces have been studied by hemispherically recorded x-ray photoelectron spectroscopy in view of substrate preparation for the epitaxy of GaN. Producing well-ordered surfaces, O2 plasma based treatments are found to efficiently remove surface contamination. AlN films with good short-range order are obtained by a simple high temperature nitridation step in the MOCVD reactor.
Mosaic Structure and Cathodoluminescence of GaN Epilayer Grown by LP-MOVPE
Authors: Duan Shukun , Teng Xuegong , Li Yenran , Wang Yutian , Han Peide , Lu Dacheng
Published: April 2011

We have studied the growth of GaN on (0001) sapphire and (111) spinel substrates by LP-MOVPE and compared the mosaic structure and cathodoluminescence for the heteroepitaxial films of GaN grown on these substrates.
X-Ray Photoelectron Diffraction Measurements of Hexagonal GaN(0004) Thin Films
Authors: Denecke R. , Morais J. , Wetzel C. , Liesegang J. , Haller E. E. , Fadley C. S.
Published: April 2011

We report on the first scanned-angle x-ray photoelectron diffraction measurements on GaN(0001) in the wurtzite structure, as grown on sapphire substrates using MOCVD. These as-grown samples reveal forward scattering peaks in agreement with a theoretical calculation using a single scattering cluster calculation. The surface contamination by O and C does not exhibit any clear structure. From the combination of experiment and theoretical calculation and from a simple intensity ratio argument the surface termination for these samples could be determined to be N. The data also indicate that C is on average closer to the GaN surface than O.
Complete Characterization of AlxGa1-xN/InxGa1-xN/GaN Devices by Sims
Authors: Huang C. , Mitha S. , Erickson J. W. , Clark-Phelps R. , Sheng Jack , Gao Y.
Published: April 2011

SIMS analysis was applied to the characterization of GaN, AlGaN/GaN and InGaN/GaN grown by MOCVD. Such characterization enables the control of purity and doping, and the determination of growth rate and alloy composition. The analysis can be performed on finished optoelectronic and electronic devices and this makes SIMS technique a powerful tool for failure analysis, reverse engineering, and concurrent engineering.
Photoelectrochemical etching of GaN
Authors: Youtsey C. , Bulman G. , Adesida I.
Published: April 2011

A photoelectrochemical etching process for n-type GaN using KOH solution and broad-area Hg arc lamp illumination is described. Etch rates as high as 320 nm/min are obtained. The etch rate is investigated as a function of light intensity for stirred and unstirred solutions. Preliminary results on etching of Al0.1Ga0.9N layers are reported.
Patterning of GaN in High-Density Cl2- and BCl3-Based Plasmas
Authors: Shul R. J. , Briggs R. D. , Han J. , Pearton S. J. , Lee J. W. , Vartuli C. B. , Killeen K. P. , Ludowise M. J.
Published: April 2011

Fabrication of group-Ill nitride electronic and photonic devices relies heavily on the ability to pattern features with anisotropie profiles, smooth surface morphologies, etch rates often exceeding 0.5 μm/min, and a low degree of plasma-induced damage. Patterning these materials has been especially difficult due to their high bond energies and their relatively inert chemical nature as compared to other compound semiconductors. However, high-density plasma etching has been an effective patterning technique due to ion fluxes which are 2 to 4 orders of magnitude higher than conventional RIE systems. GaN etch rates as high as -1.3 μm/min have been reported in ECR generated ICI plasmas at -150 V dc-bias. In this study, we report high-density GaN etch results for ECR- and ICP-generated plasmas as a function of Cl2- and BCl3-based plasma chemistries.
Dry Etching of GaN Using Reactive Ion Beam Etching and Chemically Assisted Reactive Ion Beam Etching
Authors: Lee Jae-Won , Park Hyong-Soo , Park Yong-Jo , Yoo Myong-Cheol , Kim Tae-Il , Kim Hyeon-Soo , Yeom Geun-Yong
Published: April 2011

Dry etching characteristics of GaN using reactive ion beam etching (RIBE) were studied. Etching profile, etching rate and etching selectivity to a photoresist (PR) mask were investigated as a function of various etching parameters. Characteristics of chemically assisted reactive ion beam etching (CARIBE) and RIBE were compared at varied mixtures of CH4 and Cl2. A highly anisotropie etching profile with a smooth surface was obtained for tilted RIBE with Ch at room temperature. Etching selectivity to a PR was dramatically improved in RIBE and CARIBE when a volume fraction of CH4 to the mixture of CH4 and Ch was larger than 0.83.
Plasma Damage Effects in InAlN Field Effect Transistors
Authors: Ren F. , Lothian J. R. , Chen Y. K. , Mackenzie J. D. , Donovan S. M. , Abernathy C. R. , Varturi C. B. , Lee J. W. , Pearton S. J. , Wilson R. G.
Published: April 2011

During gate mesa plasma etching of InN/InAlN field effect transistors the apparent conductivity in the channel can be either increased through three different mechanisms. If hydrogen is part of the plasma chemistry, hydrogen passivation of the shallow donors in the InAlN can occur, we find diffusion depths for 2H of ≥ 0.5 micron in 30 mins at 200°C. The hydrogen remains in the material until temperatures ≥ 700°C Energetic ion bombardment in SF6/O2 or BCl/Ar plasmas also compensates the doping in the InAlN by creation of deep acceptor states. Finally the conductivity of the immediate InAlN surface can be increased by preferential loss of N during BCl3 plasma etching, leading to poor rectifying contact characteristics when the gate metal is deposited on this etched surface. Careful control of plasma chemistry, ion energy and stoichiometry of the etched surface are necessary for acceptable pinch-off characteristics.
New Precursor Routes to Nanocrystalline Cubic/Hexagonal Gallium Nitride, GaN
Authors: Wells R. L. , Janik J. F. , Gladfelter W. L. , Coffer J. L. , Johnsons M. A. , Steffey B. D.
Published: April 2011

Two precursor routes culminating in bulk nanocrystalline gallium nitride materials are reported, with emphasis on the materials' XRD/crystalline features and photoluminescence (PL). First, the new polymeric gallium imide, {Ga(NH)3/2}n, can be converted to nanocrystalline, cubic/hexagonal GaN ranging in color from yellow to light gray. Second, a new route to gallazane, [H2GaNH2]x, from the combination of LiGaH4 and NH4X (X = Cl, Br) in Et2O is shown to result in a material that slowly converts to a polymeric solid via H2 and NH3 elimination-condensation pathways. Both the gallazane and the polymeric solid are pyrolyzed to dark gray nanocrystalline, phase-inhomogeneous GaN as above. Specific variations in the pyrolysis conditions enable some control over the particle nanosize and a degree of crystalline phase-inhomogeneity of the materials. These nanophase GaN materials have also been characterized by room temperature photoluminescence (PL) measurements. In general, the observed emission spectra are strongly dependent on pyrolysis temperature and typically exhibit weak defect yellow-green emission. While the as-prepared GaN does not exhibit band-edge PL, a brief hydrofluoric acid etch yields nanophase GaN exhibiting an intense blue-emitting PL spectrum with an emission maximum near 420 nm.
Phase Formation and Morphology in Nickel and Nickel/Gold Contacts to Gallium Nitride
Authors: Venugopalan H. S. , Mohney S. E. , Luther B. P. , DeLucca J. M. , Wolter S. D. , Redwing J. M. , Bulman G. E.
Published: April 2011

Metallurgical reactions between Ni and GaN have been explored at temperatures between 400 and 900 °C in N2, Ar, and forming gas. A trend of increasing Ga content in the reacted films was observed with increasing temperature. The reactions are consistent with the thermodynamics of the Ni-Ga-N system. Changes in the film morphology on annealing were also examined. Metal island formation and a corresponding deep, non-uniform metal penetration into GaN were observed at high temperatures. The relevance of the observed nature of phase formation and morphology in these thin films to electrical properties of Ni/GaN and Au/Ni/GaN contacts is also considered.
Comparison of Electron and Hole Initiated Impact Ionization in Zincblende and Wurtzite Phase Gallium Nitride
Authors: Bellotti E. , Oguzman I. H. , Kölnik J. , Brennan K. F. , Wang R. , Ruderi P. P.
Published: April 2011

In this paper, we present the first calculations of the electron and hole impact ionizatioi coefficients for both wurtzite and zincblende phase GaN as a function of the applied electrii field. The calculations are made using an ensemble Monte Carlo simulator including the ful details of the conduction and valence bands derived from an empirical pseudopotentia calculation. The interband impact ionization transition rates for both carrier species an determined by direct numerical integration including a wavevector dependent dielectric function It is found that the electron and hole ionization coefficients are comparable in zincblende Ga> at an applied field of ∼ 3 MV/cm, yet vary to a slight degree at both higher and lower applied field strengths. In the wurtzite phase, the electron and hole coefficients are comparable at hig] fields but diverge at lower applied fields. The most striking result is that the ionization rates an predicted to be substantially different for both carrier species between the two phases. It i predicted that the ionization rates for both carrier species in the zincblende phase are significanti; higher than in the wurtzite phase over the full range of applied fields examined.
Aluminum Nitride Thin Films Grown by Plasma-Assisted Pulsed Laser Deposition on Si Substrates
Authors: Okamoto M. , Ogawa T. , Mori Y. , Sasaki T.
Published: April 2011

The smooth and highly oriented AlN films were obtained using pulsed laser deposition from sintered AlN target in a nitrogen ambient. The XRD investigation revealed that highly oriented AlN thin films along the c-axis (AlN (0002)) normal to the substrate were obtained both on Si(111) and on Si(100) substrates. The (0002) x-ray peak width became narrower with increasing substrate temperature. The CL investigation showed that AlN films at high laser energy density (Ed) indicated CL peak at shorter wavelength (306nm) than that at low Ed (394nm). N/Al atomic ratio in AlN films grown at high Ed also increased as comparison with the films grown at low Ed.
High Performance High Dielectric Constant Films Deposited by Dual Spectral Source Rapid Isothermal Assisted Metalorganic Chemical Vapor Deposition (MOCVD)
Authors: Chen Y. , Singh R. , DeBoer S. , Thakur R.P.S.
Published: April 2011

Dual spectral source assisted MOCVD is an ideal technique for the deposition of high dielectric constant materials as well as other electronic and optical materials. Tungsten halogen lamps and a deuterium lamp are used as the sources of optical and thermal energy. Ta2O5films were deposited at 200°C for 30 minutes and annealed at 600°C for 30 minutes have shown leakage current densities as low as 10−10A/ cm2for gate voltage under 5V. To the best of our knowledge, these are the best results reported to date by other researchers. The high energy photons used in thein-situcleaning and deposition process play an important role in obtaining high quality films of Ta2O5.
Rapid Verticai Processor for Fast-Ramp Small-Batch Diffusion and Oxidation Applications
Authors: Porter Cole , Laser Allan , Ratliff Christopher
Published: April 2011

Fast-ramp small-batch vertical furnace technology improves batch furnace processing capabilities. Reducing cycle time and improving diffusion control while still maintaining a low cost of ownership and film thickness uniformity are the key benefits of this new technology. A new high power density furnace has been designed to accommodate accelerated wafer temperature ramp up and cool down rates. Unique quartz fixturing is also used to minimize thermal stress across the wafers. This paper will describe both thermal uniformity and film uniformity results for a 65Å Gate Oxide Process for the Rapid Vertical Processor (RVP). In addition, thermal stress data and throughput results will be presented.
In-Situ Oxygen Monitoring of Rapid Thermal Process Chamber: Diagnosis of Gas Flow Dynamics and Wafer Processing
Authors: Kondoh E. , Maex K.
Published: April 2011

Two types of real-time oxygen monitoring are investigated for RTP applications, i.e. addressing the basis for a state-of-the-art clean ambient technology and understanding its impact on real processes. Diagnosing of gas flow dynamics in the chamber is carried out by tracer experiments. Deviation from plug flow, which decreases purge efficiency, is found to be a function of gas flow rate. The monitoring of a typical two-step RTP process for silicidation of Ti or Co show that both adsorption and desorption take place. Oxygen is desorbed first at lower temperatures (during temperature ramp) then starts to be adsorbed at higher temperatures. In the case of Ti, a few monolayers of oxygen is adsorbed during the first RTP but less oxygen is adsorbed during the second RTP. The amount of oxygen adsorbed during Co RTP is found to be not as high as during Ti RTP.
Kinetics of Pt Silicide Formation Studied by Spectral Ellipsometry
Authors: Schwarz R. , Dittrich A. , Zhou S. M. , Hundhausen M. , Ley L. , Chen L. Y. , Woerle D. , Manke C. , Schulz M.
Published: April 2011

Suicide formation during thermal annealing of thin Pt layers deposited by evaporation onto crystalline silicon substrates was studied by in-situ spectral ellipsometry. As was shown in an earlier study, Pt suicide is formed in a two-step process with intermediate stages of Pt2Si and PtSi at temperatures of about 190 and 240 °C, respectively. We observed a shift of about 15 °C of the di- and monosilicide formation, when the anneal rate was lowered from 3 to 1 K/min. The analysis of the reaction kinetics using the normalized ellipsometric angle δ yields a good fit to the data for different anneal rates with an activation energy of (1.6 ± 0.2) eV. The underlying model of suicide formation through a multilayer system was checked with depth profiles and compositional information obtained from Rutherford Backscattering.
Laser-Assisted TiSi2 Formation for ULSI Applications
Authors: Shamma Nader , Talwar Somit , Verma Gaurav , Kramer Karl-Josef , Farrar Nigel , Chi Chiu , Greene Wayne , Weiner Kurt
Published: April 2011

In this paper, we describe the results of recent work in which TiSi2 formation on deep-submicron polysilicon gates is achieved using pulsed excimer laser irradiation. Formation of low resistivity titanium suicide on sub-0.1 μm polysilicon lines is confirmed by sheet resistance measurements. High-resolution TEM examination shows exceptionally smooth interface between suicide and heavily-doped silicon substrate. Gate to source/drain bridging is not observed. Analytical techniques including Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD) have been used to characterize the irradiated films. This laser-assisted suicide formation process is a promising technology for extreme submicron MOSFET applications.
Rapid Thermal Process Requirements for The Annealing of Ultra-Shallow Junctions
Authors: Downey Daniel F. , Daryanani Sonu L. , Meloni Marylou , Brown Kristen M. , Felch Susan B. , Lee Brian S. , Marcus Steven D. , Gelpey Jeff
Published: April 2011

2. 0 keV 11B+, 2.2 keV 49BF2+ ion implanted and 1.0 kV Plasma Doped (PLAD) wafers of a dose of 1E15/cm2 were annealed at various times and temperatures in a variety of ambiente: 600 to 50,000 ppm O2 in N2; 5% NH3 in N2; N2O; N2 or Ar, in order to investigate the effects of the annealing ambient on the formation of ultra-shallow junctions. RGA data was collected during some (if the anneals to assist in identifying the complex surface chemistry responsible for boron out-diffusion. Subsequent to the anneals, ellipsometric, XPS, four-point probe sheet resistance and SJJVIS measurements were performed to further elucidate the effects of the different ambients on the r etained boron dose, the sheet resistance value, the RTP grown oxide layer and the junction depth. In the cases where oxygen was present, e.g. N2O and O2 in N2, an oxidation enhanced diffusion of the boron was observed. This was most dramatic for the N2O anneals, which at 1050°C 10s diffused the boron an additional 283 to 427 Å, depending on the particular doping condition and species. For the case of BF2 implants and PLAD, anneals in 5% NH3 in N2 reduced the junction depth by a nitridation reduced diffusion mechanism. RGA data indicated that the out-diffusion mechanisms for B and BF2 implanted wafers are different, with the BF2 exhibiting dopant loss mechanisms during the 950°C anneals, producing F containing compounds. B implants did not show doping loss mechanisms, ais observed by the RGA, until the 1050°C anneals and these signals did not contain F containing compounds. Equivalent effective energy boron implants of 8.9 keV BF2 vs. 2.0 keV B, however, indicated that the overall effect of the F in the BF2 implants is very beneficial in the creation of ultra-shallow junctions (compared to B implants): reducing the junction depth by 428 Å, and increasing the electrical activation (determined by SRP) by 11.7%, even though the retained dose (resulting from an increased out-diffusion of B), was decreased by 5.4%.
Temperature Measurement Issues in Rapid Thermal Processing
Authors: DeWitt D. P. , Sorrell F. Y. , Elliott J. K.
Published: April 2011

Reliable radiometrie temperature measurement has been a major challenge in making rapid thermal processing (RTP) more widely accepted. In order to meet road map requirements involving temperature uncertainty, uniformity and control, new techniques must be demonstrated and/or existing measurement methods must be substantially improved. Critical aspects of radiometrie methods for temperature measurement are centered about the topics: radiative and optical properties of the wafers including layered systems, surface roughness effects, and reflected irradiation from lamp banks and chamber walls. The systematic method for inferring temperature is rooted in the measurement equation which relates the radiometer output to the exitent spectral radiance from the target which reaches the detector and prescribes the roles that emissivity variability and stray radiation have on the result. An overview is provided on the knowledge base for optical and thermal radiative properties. Methods for reducing emissivity and stray radiation effects are summarized. Calibration procedures necessary to assure that the in-chamber or local temperature scale is traceable to the International Temperature Scale (ITS-90) are discussed. The issues which can impact improved temperature measurement practice are summarized.
Low Temperature Si Oxidation with Excimer Lamp Sources
Authors: Boyd Ian W. , Zhang Jun-Ying
Published: April 2011

The principles of vacuum ultraviolet (VUV) and ultraviolet (UV) light generated from a new type of excimer lamp are described. Direct photo-oxidation of silicon at a temperature of 250°C has been investigated using a Xe2* excimer lamp operating at a wavelength of 172 nm. The induced reaction rate of 0.1 nm/min is 90 times greater than thermal oxidation at 612°C. Results will be compared to those previously obtained by a low pressure mercury lamp and conventional furnace oxidation. Ozone plays an extremely important role in the reaction enhancement which was found to be strongly dependent upon oxygen pressure with the highest rates being achievable below 10 mbar. Ellipsometry, Fourier transform infrared spectroscopy, capacitance-voltage, and current-voltage measurements have been employed to characterise the oxide films grown and indicate them to be high quality layers. The electrical properties of the as-grown films have been improved significantly by applying an additional UV/O3annealing step. A simple model explaining the observed reduction in the leakage current after UV annealing is proposed whilst the current conduction mechanism within the films is discussed.
Exploitation of Quantum Photoeffects in Reducing Microscopic Defects and Processing Cycle Time in Advanced Rapid Thermal Processing
Authors: Vedagarbha V. , Singh R. , Ratakonda D. , Vedula L. , Rohatgi A. , Narayanan S.
Published: April 2011

Rapid thermal processing is fast emerging as a vital low thermal budget processing technique. Use of photons of wavelengths less than 800 nm in conjunction with infrared and visible photons in RTP resulted in the reduction of microscopic defects and processing time. Screen printed back surface field (BSF) contacts and ohmic contacts which are an integral part of solar cells were processed and Schottky barrier diodes were made. Cycle time was reduced from 172 see's to 108 see's in the case of back surface field contacts and from 162 see's to 122 see's for the ohmic contacts. The Schottky diodes were characterized for electrical data. The structural properties of the metal silicon interface have direct correlation with the electrical properties of the device.
Impact of Emissivity-Independent Temperature Control in Rapid Thermal Processing
Authors: Oh Minseok , Nguyenphiu Binh , Huang Robert , Ma Yi , Chaplin Stefanie , Brady David , Lee Cynthia
Published: April 2011

Due to polycrystallization, the emissivity of amorphous silicon is known to vary during annealing at temperatures above 500°C. This transition from α-Si to poly-Si usually occurs during the ramp and the beginning of steady stages of the rapid thermal process. However, the majority of current temperature control methods in RTP neglect time-dependent change of emissivity, and the temperature profile of process calibration is different from that of real annealing process. Various kinds of wafers with in-situ doped amorphous Si are investigated using emissivity-independent temperature control. Some process parameters and material parameters, such as ramp rate and doping level, are explored to study their influences on emissivity change, and consequently on electrical and optical parameters.
Dynamics of a Plasma Panel Discharge: Current Waveform and Optical Emission
Authors: Ambalanath S. , Compaan A. D. , Truxon J. M. , Gottschalky J. , Shvidky A. , Theodosiou C. E. , Williamson W.
Published: April 2011

We have studied the current waveform as well as the time- and spectrally-resolved optical emission from a monochrome ac plasma display panel as a function of driving voltage. The voltage driver provided a 18 ns risetime pulse which allowed for a clean separation between the displacement current pulse, ∼25 ns wide, and the discharge pulse. The commercial panel was specially filled with pure He to facilitate comparisons with numerical modeling of the discharge based on relatively new computational procedures which are applied to a local-field approximation for the plasma. The delay in the discharge pulse and the light emission at 668 nm (3d 1D→2p 1P), ranges from ∼100 ns just above the sustain threshold (± 110V) to ∼30 ns at higher voltage (±150 V).
Low-Temperature Crystallization of Amorphous Silicon Thin Films by Microwave Heating
Authors: Lee Jeong No , Kim Yoon Chang , Choi Yong Woo , Ahn Byung Tae
Published: April 2011

Microwave heating was utilized for the first time for solid phase crystallization of amorphous silicon films. Microwave heating lowered annealing temperature and reduced the annealing time for complete crystallization. For example, the amorphous silicon film deposited at 400 °C was fully crystallized in 3 h at 550 °C below which glass is available as a substrate. On microwave heating, the hydrogen in the amorphous films diffused out very quickly, but there was no change in structural disorder following hydrogen evolution. The lower temperature crystallization of a-Si films compared to conventional furnace annealing is due to the interaction between microwave and silicon atoms. The grain size of the crystallized silicon films was in the range of 0.55 to 0.78 μm, depending on the deposition temperature. These grain sizes are not so small comparing those of Si films by conventional furnace heating, while the crystallization processing time is much shorter.
Comparison of Conventional and Self-Aligned a-Si:H Thin Film Transistors
Authors: Yang Chien-Sheng , Read Walter W. , Arthur Chris B. , Parsons Gregory N.
Published: April 2011

Conventional and self-aligned processes were developed for 250 °C inverse-staggered bottom gate a-Si:H thin film transistors (TFT's). Tri-layers of silicon nitride, amorphous silicon, and silicon nitride were continuously deposited in a plasma enhanced chemical vapor deposition system (PECVD). A self-alignment technique including back-side exposure and top nitride over etch was developed, which eliminates a masking step and the critical alignment of via opening used in typical TFT processing. Full self-aligned TFT's formed by selective n+ deposition were also fabricated successfully. Transistors show linear mobility ranging from 0.7 to 1.0 cm2/Vs, and current ON/OFF ratios greater than 106 were achieved for all TFT's.
Profile Simulation of Reactive Ion Etching for Silicon Tip-on-Post and Bottle-Neck Structures in Fed Applications
Authors: Zoulkarneev A. R. , Kim J. M. , Hong J. P. , Choi J. H. , Michine V. V.
Published: April 2011

This articles describes an investigation of the reactive ion etching of tip-on-post and bottle-neck silicon structures used for fabrication field emission devices. The analytical study for the angular distribution of incident etching ions is presented by the simulation with temporal profile evolution. The surface simulations are compared with experimental results. This comparison shows that numerical expression for the angular distribution could be applied for incident ion flux in case tip-on-post and bottle-neck silicon structures.
Luminescent Studies of Fluorescent Chromophore-Doped Silica Aerogels for Flat Panel Display Applications
Authors: Glauser Sally A. C. , Lee Howard W. H.
Published: April 2011

The remarkable optical and electronic properties of doped and undoped silica aerogels establish their utility as unique, multifunctional host materials for fluorescent dyes and other luminescent materials for display and imaging applications. We present results on the photoluminescence, absorption, and photoluminescence excitation spectra of undoped silica aerogels and aerogels doped with Er3+, rhodamine 6G (R6G), and fluorescein.
Direct Writing and Lift-Off Patterning of Copper Lines at 200°C Maximum Process Temperature
Authors: Hong C. M. , Gleskova H. , Wagner S.
Published: April 2011

We adapted a new technique for depositing copper lines, at a maximum process temperature of 200°C. The technique is based on the decomposition of copper hexanoate by UV light, followed by annealing in H2 [1]. A copper film resistivity of 8 μΩcm is obtained. We patterned this copper metallization on Corning 7059 glass substrates by three different techniques, including exposure through a shadow mask, lift-off of xerographic toner, and direct writing.
Conducting Polymer Films for Plastic Liquid Crystal Displays
Authors: Huang Ling , O'Ferrall Catherine , Shashidhar Ranganathan , Fritz William , Hewitt Richard , Smith Steve , William Doane J.
Published: April 2011

In a conventional liquid crystal display (LCD), glass substrates coated with an indium tin oxide (ITO) layer are typically used for the application of an electric field to the liquid crystal material. For many applications, there is a need for a LCD with a plastic substrate. While ITO works well with glass, it does not adhere as well to plastic. It is brittle, and has a tendency to crack under constant bend conditions. Polypyrrole is well known for its good conductivity and chemical stability. Moreover, as an organic polymeric material, polypyrrole film can also flex and bend with the plastic substrate. Therefore, it is a good candidate for plastic LCDs. We present here the results on the development of polypyrrole films deposited on plastic substrates which are suitable for reflective LCDs.
Reflective Flat Panel Display Materials Based on Holographically Formed Liquid Crystal-Polymer Dispersions
Authors: Williams A. D. , Nelson E. W. , Silverstein L. D. , Fiske T. G. , Crawford G. P.
Published: April 2011

Holographically formed polymer dispersed liquid crystal (H-PDLC) displays are investigated in terms of their electro-optic performance parameters and their potential as capable full color display systems. It is demonstrated that the transmission-voltage curve can be modified by low concentrations of chiral dopants, increasing the steepness of the response curve. To probe the details of full-color reflective H-PDLC displays, we invoke a generalized colorimetric/photometric analysis to estimate the display reflectance, white-point, and chromaticity diagram for a vertically integrated stack of red, green, and blue H-PDLC displays.
Improving Contrast Ratio in Color Filters for AMLCD Devices
Authors: Pai D. Y. , Cernigliaro G. J. , Richardson T. A.
Published: April 2011

The widespread use of pigmented color filters in the AMLCD industry has focused attention on their deficiencies, which include marginal film transmittance, significant depolarization and generally poor imaging characteristics for the corresponding imaging resists. These limitations result in diminished color filter contrast and curtailed brightness for the AMLCD device. Incremental color filter contrast improvements have been generated through use of smaller pigment particles which reduce, but do not eliminate, light scattering. As standard pigment synthetic and grind processes give only small color contrast gains, at a cost of protracted pigment manufacture time, another route to more significant gains in color filter contrast is probably necessary. The work herein describes our attempt at defining one viable approach to real improvements in the key color filter responses of reduced depolarization and improved color contrast.

Our approach employs colorants prepared from colloidal suspensions of nanosized, mono-dispersed, dense silica spheres to which appropriate red, green and blue dyes are sorbed. Subsequent dispersion of each colorant nanocomposite in carrier polymer and photoimaging chemistry yields the corresponding negative-tone red, green and blue imageable photoresist. The synthesis and use of monodispersed colorant colloids has been described by Giesche and Matijevic for this and other related areas, but their utility is limited to applications not addressing the more advanced color filter requirements mentioned above. To those ends, our work focused on the synthesis, formulation and optical testing of nanocomposite colorant particles ranging from 10–30 nm in size, using dye chemistry which bridges compatibility between both silica nanosphere and carrier polymer, resulting in clear, highly transparent color films. Two independent optical tests comparing the color contrast on nanocomposite red films with coatings of similar transmittance prepared from reference red pigment dispersion provided rationalization that light scattering is significantly reduced in the nanocomposite film, as evidenced by the 3–10 fold increase in the color contrast ratios.
The Characterization of Al2O3 Films Grown by Atomic Layer Deposition Using Al(CH3)3 and H2O
Authors: Yun Sun Jin , Lee Kyung-Ho , Skarp Jarmo , Kim Hae-Rim , Nam Kee-Soo
Published: April 2011

The materials characteristics of Al2O3 films grown on Si (100) substrate by traveling wave reactor atomic layer deposition were investigated at the growth temperature ranging from 250 to 500°C. The Al2O3 films grown using Al(CH3)3(TMA) and H2O as precursors were characterized and also compared with the films grown using AlCl3 and H2O. In the study of impurity incorporation, the films grown using TMA showed the C and H count rates of secondary ion mass spectrometry (SIMS) approximately 7–10 times higher than those of the film grown using AlCl3. For the Al2O3 films grown using TMA, the impurity contents and the growth rate decreased and the refractive index increased as increasing the growth temperature. The effect of purge time increase on the impurity incorporation was very small compared with that of growth temperature. The refractive indices were 1.64 and 1.68 at the growth temperatures of 250 and 400°C, respectively. The rough estimation using SIMS data and refractive indices indicated that the H-content decreased from 8.6 at% to 2.9 at% as increasing the substrate temperature from 250 to 400°C. The Al2O3 film grown using AlCl3 and H2O at 500°C contained approximately 0.5% Cl and revealed the refractive index of 1.65.
Transmission Electron Microscopy Study of YBa2Cu3O7-x Thin Film Multilayer Devices
Authors: Barnett M. A. , Abell J. S. , Aindow M. , Chew N. G. , Hirst P. J. , Humphreys R. G.
Published: April 2011

Patterned thin film multilayer structures, consisting of superconducting YBa2Cu3O7-x (YBCO) and insulating PrBa2Cu3O7-x (PrBCO), deposited onto (001) MgO substrates by electron beam co-evaporation, have been examined using Transmission Electron Microscopy (TEM). It is shown that PrBCO films grown over 30° steps in YBCO layers are free of tilt-grain boundaries. The PrBCO is c-oriented everywhere and shows pronounced faceting on the steps. Strain contrast features are present where the PrBCO has to adapt to large variations in the slope angle of the underlying YBCO layer. However, tilt-grain boundaries in YBCO or PrBCO layers are nucleated when depositing over small MgO steps formed by unintentional milling into the substrate. It is shown that grain boundaries associated with milled steps on MgO can be eliminated by the use of a PrBCO buffer layer beneath the superconducting base layer.
Colossal Magnetoresistance in La-Ca-Mn-O
Authors: Jin S.
Published: April 2011

Very large increase in electrical conductivity by several orders of magnitude is obtained when an external magnetic field is applied to the colossal magnetoresistance (CMR) materials such as La-Ca-Mn-O. The magnetoresistance is strongly temperature-dependent, and exhibits a sharp peak below room temperature, which can be shifted by adjusting the composition or processing parameters. The control of lattice geometry or strain, e.g., by chemical substitution, epitaxial growth or post-deposition anneal of thin films appears to be crucial in obtaining the CMR properties. The orders of magnitude change in electrical resistivity could be useful for various magnetic and electric device applications.
Structure-Property Relationships in SrRuO3 Epitaxial Thin Films
Authors: Maria J-P. , Trolier-McKinstry S. , Schlom D. G.
Published: April 2011

Epitaxial SrRuO3 films were prepared on (001) SrTiO3 substrates by pulsed laser deposition. The film structure was characterized by 4-circle x-ray diffraction and the electrical behavior by temperature dependent resistivity measurements. With variations in the deposition conditions, significant changes in both structural and electrical properties were observed. When deposited under conditions favoring appreciable energetic bombardment, the SrRuO3 films on SrTiO3 exhibited extended in and out-of-plane lattice constants and increased values of resistivity; in addition, a depression of the Curie temperature was measured. SrRuO3 deposited under less aggressive conditions displayed structures and properties more similar to those associated with bulk crystals.
Giant Ferromagnetic Hall Coefficient in La0.5Ca0.5CoO3
Authors: Samoilov A. V. , Yeh N. -C. , Vasquez R. P.
Published: April 2011

We report the studies of the Hall effect and magnetic properties in La0.5Ca0.5CoO3 thin films and ceramics. We use the local Hall probe and SQUID magnetometers to measure the magnetization M of the samples. Both below and above the Curie temperature, the Hall resistivity pxy(H) is shown to be proportional to M(H) (H is the applied magnetic field). Thus, our results provide convincing evidence for the anomalous Hall effect in these cobaltites. The value of the anomalous Hall coefficient Rs in La0.5Ca0.5CoO3 significantly exceeds those of other known single-phase ferromagnetic metals. We suggest that the coexistence of high- and low-spin configurations in the perovskite cobaltites, which gives rise to magnetic percolation behavior in La1-xCax.CoO3,may be responsible for the giant Ra.
Preparation of Epitaxial and Polycrystalline La0.8Sr0.2MnO3 Films by Dipping-Pyrolysis Process
Authors: Manabe T. , Fujimoto T. , Hwang K-S. , Yamaguchhi I. , Kondo W. , Kojima I. , Mizuta S. , Kumagai T.
Published: April 2011

The films of La0.8Sr0.2MnO3 (LSMO) were prepared on single-crystal SrTiO3(100) and polycrystalline yttria-stabilized zirconia (YSZ) substrates by dipping-pyrolysis process using metal naphthenates as starting materials. The crystallinity, grain alignment, morphology and electric properties of the films were compared. Epitaxial films were found to grow on SrTiO3, heat-treated at 1200°C, by x-ray diffraction, and to exhibit very smooth surfaces by SEM and AFM observations. On the other hand, the surfaces of the polycrystalline films grown on YSZ consisted of round-shaped LSMO grains. The resistivity of the epitaxial films was about two orders of magnitude lower than that of the polycrystalline films prepared under the same conditions. Preparation of epitaxial LSMO films on SrTiO3(110) is also presented.
The Effects Of Substrate Thermal Mismatch on the Domain Structure of MOCVD-Derived Potassium Niobate Thin Films
Authors: Nystrom M. J. , Wessels B. W.
Published: April 2011

Domain stabilization in epitaxial potassium niobate films deposited by metalorganic chemical vapor deposition was studied. Stabilization was examined for films deposited on substrates with different coefficients of thermal expansion. X-ray diffraction of KNb03 films deposited on (100) MgAl204, (r) A1203, and (100)pseudocubic YAIO3 substrates shows a mixed domain structure consisting of (110) and (001) domains. However, KNb03 thin films deposited under identical conditions on (100) MgO, (100) SrTi03, and (100)pseudocubic LaA103 substrates exhibited only a single domain variant. A direct correlation between (001) domain volume fraction in the as-deposited KNb03 films and calculated strain resulting from thermal mismatch is observed.
Epitaxial Growth of Oxide Thin Films on (001) Metal Surfaces Using Pulsed-Laser Deposition
Authors: Norton D. P. , Park C. , Saffian B. , Budai J. D. , Goyal A. , Christen D. K. , Kroeger D. M. , Lee D. , He Q. , Paranthaman M.
Published: April 2011

The epitaxial growth of CeO2 on various (001) metal surfaces using pulsed-laser deposition is discussed. In particular, the growth of (001) CeO2 on (001) Pd, Ag, and Ni is described. Emphasis is given to the specific deposition conditions which successfully alleviate the formation ornative oxides at the metal/metal oxide interface. The control of the epitaxial relationships between the oriented oxides films and the underlying noble and oxidizing metal surfaces is addressed.
MOCVD Precursor Delivery Monitored and Controlled Using UV Spectroscopy
Authors: Rappoli Brian J. , DeSisto William J. , Marks Tobin J. , Belot John A.
Published: April 2011

The glyme adducts of bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate)barium, Ba(hfac)2•glyme, are frequently employed as precursors in the MOCVD fabrication of HTSC thin films. The physical properties of these precursors can be modified by changing the glyme ligand in the barium complex. In this study, gas phase concentrations of two barium complexes as a function of purge time and bubbler temperature have been examined by in-situ UV spectroscopy. Also presented are the details of a UV spectrophotometric-based feedback control system designed to maintain constant gas phase concentration of 2,2,6,6-tetramethyl-3,5-heptadionate (thd) precursors, Cu(thd)2 and Y(thd)3, during MOCVD growth of mixed metal oxide films.
Llo Phase Formation in CoPt Thin Films
Authors: Ristau R. A. , Barmak K. , Coffey K. R. , Howard J. K.
Published: April 2011

The high magnetic anisotropy and high coercivity of equiatomic CoPt thin films make them attractive as potential materials for magnetic recording applications. Magnetic coercivity (Hc) over 10 kOe has been measured in films in which the as-deposited fee phase has been partially transformed to the atomically ordered Ll0 phase. Very high Hc has been related to high volume fraction and small size of the Ll0 precipitates. A better understanding of the Ll0 phase formation and quantification of volume fraction is critical to optimizing the magnetic properties of this material.

As we have previously reported, an increase in Hc was observed with an increase in Ll0 volume fraction in 10 nm thick, equiatomic CoPt films. In our current investigation we have observed that, at anneal temperatures far from the order/disorder transition temperature, e.g. at T = 0.6 Tc, numerous, very fine Ll0 precipitates are seen, some of which cluster at the parent phase grain boundaries. At T = 0.85 Tc, very few, larger Ll0 regions were seen. As precipitates of the ordered phase grow to impingement, antiphase boundaries (APB) are formed. This is consistent with a heterogeneous nucleation and growth mechanism for the formation of the Ll0 phase throughout the temperature range studies.
Low-Temperature Growth of NiMnSb Heusler Alloy Thin Films
Authors: Childress J.R. , Caballero J.A. , Geerts W.J. , Petroff F. , Galtier P. , Suzuki Y. , Thiele J.-U. , Weller D.
Published: April 2011

Ferromagnetic Heusler alloys such as NiMnSb may have unique applications to magnetoresistive devices because of their predicted half-metallic band-structure (i.e., 100% spin-polarized at the Fermi level). However, the high temperatures (>500°C) used to date for the synthesis of the ordered alloy in bulk or thin-film form is incompatible with the reliable fabrication of nanoscale multilayer structures from this material. We report on the growth of high-quality polycrystalline thin films, 200–1000Å thick, of Clb-structured NiMnSb by RF-magnetron sputtering of a composite NiMnSb target onto glass and silicon substrates at temperatures as low as 250°C. We have established that substrate temperature, deposition rate and argon gas pressures all play a critical role in obtaining the Clb-structured phase by direct deposition. Optimal conditions result in films whose properties, including lattice parameter, saturation magnetization, resistivity and magneto-optical Kerr rotation spectrum are identical to those of bulk NiMnSb. Additionally, coercive fields as low as a few oersteds make these films compatible with low-field applications.