bluuebunny/crossref_metadata_2025 huggingface dataset:
ZITO (ZnO-SnO2-In2O3 ) Transparent Conducting Oxides: Electrical and Optical Properties of DC Magnetron Sputtered Films
Authors: Ow-Yang Cleva , Yeom Hyo-Yong , Yaglioglu Burag , Paine David C.
Published: April 2011

Amorphous ZITO films were deposited by dc magnetron sputtering onto glass substrates from ceramic oxide targets containing Zn:In:Sn cation ratios of 1:2:1 and 1:2:1.5. The microstructure, carrier density, mobility, and resistivity of as-deposited and annealed samples were evaluated using x-ray diffraction and Hall effect measurements. The as-deposited films were amorphous and remained so after annealing at 200°C in air for up to five hours. Transmissivity of the films exceeded 80% in the visible spectral region. The minimum resistivity value (7.6×10−4 Ω-cm) was obtained from thin films deposited using the 1:2:1 composition target and a substrate temperature of 300°C.
Molybdenum doped Indium Oxide thin films prepared by rf sputtering
Authors: Elangovan Elamurugu , Marques Antonio , Pimentel Ana , Martins Rodrigo , Fortunato Elvira
Published: April 2011

Molybdenum doped indium oxide (IMO) thin films rf sputtered at room temperature were studied as a function of oxygen volume percentage (O2 vol. %) varied between 0 and 17.5. The as-deposited films were amorphous irrespective of O2 vol. %. The minimum transmittance (<10 %) of the films deposited without oxygen has been increased on introducing oxygen (3.5 O2 vol. %) to a maximum of 90 %. The optical band gap has been increased from 3.80 eV (without oxygen) to 3.92 eV (3.5 O2 vol. %). The films were highly resistive and the hall coefficients were detectable only for the films deposited without oxygen. In order to increase the electrical conductivity, the films were annealed in the range 100-500°C in open-air and N2/H2 gas for 1 hour. The annealed films become polycrystalline with enhanced electrical and optical properties. The effect of annealing conditions on these films will be presented and discussed in detail.
Variable Temperature Capacitance-Voltage Measurements to Investigate the Density of Localized Trapping Levels in Organic Semiconductors
Authors: Sedghi Naser , Donaghy David , Raja Munira , Badriya Samer , Higgins Simon J. , Eccleston Bill
Published: April 2011

We have approximated the tail of the Gaussian distribution of states of organic semiconduc-tors with an exponential function. We have used this approach to calculate the carrier concentra-tion in organic materials, and subsequently the charge distribution in the accumulation region of a field effect device and the space-charge capacitance in accumulation mode. Small signal high frequency capacitance-voltage measurements performed at various temperatures show good agreement with this model and the characteristic temperature of the exponential function has been estimated from these measurements based on the theory developed.
In-situ TEM Study of Thermally Induced Voids in 180 nm Cu Interconnects
Authors: An Jin Ho , Ferreira P.J.
Published: April 2011

Cu interconnects have decreased in width and are at around 100 nm. A decrease in interconnect width have led to a predominately bamboo structured Cu lines. In Cu interconnects, void formation during high temperature is a reliability issue, and this study looks at the void formation behavior in damascene Cu interconnects with a predominately bamboo microstructure. First, the crystal texture and grain morphology of the Cu interconnects was observed. Then to determine the void formation behavior, in-situ Transmission Electron Microscopy (TEM) was performed. Voids that formed as a result of in-situ heating were analyzed in terms of preferential void formation sites and crystal orientation where voids formed. In bamboo structured lines, voids formed at the triple junction of grain boundary and Cu/diffusion barrier interface. The crystal orientation where voids nucleated was studied to identify diffusion paths during void nucleation and growth.
In-situ TEM observation of electromagnetic field in some real materials
Authors: Sasaki Katsuhiro , Wang Zhouguang , Fukunaga Keiichi , Hirayama Tsukasa , Kuroda Kotaro , Saka Hiroyasu
Published: April 2011

Electromagnetic fields presents in some real materials have been observed using electron holography and a simple method named the Shadow Image Distortion (SID) method which we have developed. The in-situ electron holography observation of the electric field surrounding a ceramic particle showed the rapid degradation of dielectric properties of the particle at an elevated temperature. The cross sectional view of mean electrostatic potential distributions in a silicon device has been observed. In-situ electron holography and SID observations showed the electrostatic potential distribution across a reverse biased p-n junction in a compound semiconductor. The SID method using a dedicated tool allowed single-step imaging of 2D maps of electromagnetic field.
Quantifying the Order of Spontaneous Ripple Patterns on Ion-Irradiated Si(111)
Authors: George H. Bola , Brown Ari-David , McGrath Matthew R. , Erlebacher Jonah D. , Aziz Michael J.
Published: April 2011

Uniform keV ion irradiation causes a morphological instability known to result in the spontaneous formation of topographic ripple and dot patterns. The degree of order of these patterns, which has important implications for non-lithographic patterning applications, varies markedly with fabrication conditions. We investigate the influence of systematic variations of fabrication conditions, including current density, ion fluence and ion energy, on the degree of order of argon ion bombarded Si(111) surfaces. For quantifying order in sputter rippled topographic images, we develop an algorithm that evaluates the density of topological defects, such as ripple bifurcations and terminations, and suitably normalizes the result in order to present a scalar figure of merit: the normalized defect density. We discuss fabrication conditions that lead to extremely well ordered dot and ripple patterns upon irradiation.
Irradiation-Enhanced Second-Phase Precipitation in Zr-Fe Nanocrystalline Thin Films
Authors: Kaoumi Djamel , Motta Arthur T. , Birtcher Robert C.
Published: April 2011

In situ observations in a transmission electron microscope (TEM) were used to study ion-beam enhancement of second-phase precipitation in Zr-Fe nanocrystalline thin films. The free-standing films were prepared by co-sputter deposition with an Fe content of 1.2 at%. TEM diffraction analysis showed that only the hcp Zr crystal structure was present in the as-deposited films. No second phases were detected, although Rutherford Backscattering Spectroscopy (RBS) confirmed a Fe content beyond the solubility limit of Fe in Zr (of the order of ppm). This means the thin films were Zr solid solutions supersaturated with Fe. Heat treatment in the absence of irradiation was observed to cause precipitation of the Zr2Fe intermetallic phase, but only above 673 K. The same second-phase precipitation can occur at lower temperatures in the presence of ion irradiation. Samples were irradiated in-situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with Kr ions to fluences in excess of 1016 ion/cm2, at temperatures ranging from 50 to 573 K. Second phase precipitation was detected by electron diffraction patterns and by dark field imaging comparing regions exposed to the beam with regions protected from the beam by the TEM support grid. Precipitation of Zr2Fe intermetallic phase was observed at all irradiating temperatures above room temperature. In the bulk, this phase is thermodynamically metastable in the range of temperatures investigated (relative to the orthorhombic Zr3Fe intermetallic phase). The kinetics of the irradiation-enhanced second-phase precipitation was followed by recording the diffraction patterns at regular intervals. The dose to precipitation was found to decrease with increasing irradiation temperature.
Nano-Sized Zirconium Carbides: Synthesis, Characterisation and Irradiation
Authors: Dollé Mickaël , Gosset Dominique , Bogicevic Christine , Baldinozzi Guido , Karolak Fabienne , Simeone David
Published: April 2011

The projects of a new generation of nuclear plants with improved yield and drastical reduction of waste production make necessary the development of materials able to withstand high temperature (1000-1200°C) in normal conditions. New materials such as the refractory transition metal carbides are then considered. These materials have a ceramic-like, brittle behaviour. Their mechanical properties might be improved by decreasing the particles size at a nanometer level. The behaviour under irradiation of such nano-sized materials have then to be compared with classical micro-sized ones. High density, nano-sized materials have been obtained by two different sintering techniques. In order to simulate neutron irradiation, the samples were irradiated with low energy heavy ions. Consequently, the damaged material has a low thickness (100-200 nm), requiring surface analysis methods. Here, the grazing incidence X-ray diffraction method is used. From a Rietveld analysis of the diffraction patterns, the micro-sized materials show a linear volume swelling in the range 20-40 dpa in the Zr sublattice. Nano- and micro-sized materials both show high internal distortions.
Ion beam analysis of single crystal CVD diamond
Authors: Manfredotti Claudio , Lo GIudice Alessandro , Medunic Stiepko , Jaksic Milko , Colombo Elisabetta
Published: April 2011

IBIC ( Ion Beam Induced Charge ) represents a powerful method to investigate the homogeneity of the response of semiconductor nuclear detectors from the point of view of charge collection efficiency ( cce ) with a spatial resolution of few microns. Polycrystalline materials like CVD diamond displayed in the past non-uniform cce maps, in which it was easy to notice the appearance of single grains. Moreover, the presence of traps in the defective regions around the grain boundaries caused strong polarization effects which in practice impeded in many cases to get reasonable cce maps. With the availability of new homoepitaxially grown CVD diamond samples the situation is now very much improved : maps are very uniform and the non-homogeneous broadening of peaks with the consequent worsening of energy resolution is extremely reduced.

In this paper, both proton and alpha microbeams of energies 3 and 4.5 MeV were used for the investigation of single crystal CVD homoepitaxial diamond, with a beam diameter spot of about 1.2 mm over scanned areas of more than 1 mm2, sampled in regions of interest from 450 um × 450 um down to 150 um × 150 um and below. The good spatial homogeneity together with a cce value of about 50 % made it possible to reach energy resolutions of 1.3 % FWHM, including a not negligible electrical noise. These values compare quite well with Si performances, which in the same conditions reached 0.85% FWHM. The stability and reproducibility of the detector was very good without any preliminary priming and polarization effects were reduced to a minimum. The detector was pushed in some cases up to 700 cps with apparently no cce losses and with only a slight worsening of energy resolution.
High Energy Focused Ion Beam Nanoprobes: Design and Applications
Authors: Glass Gary A. , Rout Bibhudutta , Dymnikov Alexander D. , Eschenazi Elia V. , Greco Richard , Zachry Daniel P.
Published: April 2011

An overview of the present state of high energy focused ion beam (HEFIB) system technology, nanoprobe system design and specific ion beam writing applications will be presented. In particular, the combination of P-beam, heavy-ion writing and ion implantation to produce microstructures in resists and silicon will be demonstrated.

Heretofore, the development of HEFIB technology worldwide has progressed through a series of developments at independent research facilities, each having relatively narrow and mostly isolated, research purposes. However, a complete, versatile HEFIB nanoprobe system capable of both analysis and modification will require the combination of several component systems, each with specialized technology, and significant advances in the design of a complete system can only be expected from an effort that includes a coordinated development of the component parts.
Positron Annihilation Investigation in Ion-implanted Yttria-stabilized Zirconia
Authors: Grynszpan Robert , Brauer G. , Anwand W.
Published: April 2011

Implantation with a variety of sub-MeV ions (He, Ar, Xe, O, and I) were performed on cubic single crystals of yttria-stabilized zirconia in order to assess the capability of such material to withstand high fluences as a confinement matrix for nuclear waste. In this work, we confronted the results of both Doppler Broadening using slow positron implantation spectroscopy (DB-SPIS) and the Rutherford Backscattering/Channeling spectroscopy (RBS-C) which are sensitive to lattice defects almost opposite in nature. In spite of their difference in defect specific sensitivity, and except for a precursory damage production stage almost exclusively exhibited by SPIS for very low doses (< 0.1 dpa), either techniques show a similar fluence dependence, which exhibits 3 stages starting respectively around 0.1, 2 and 3 dpa, regardless of the damaging ion. However, owing to the stage I plateau displayed in the variation of the DB-SPIS lineshape parameter, we were able to estimate an ion-mass dependence of the critical size of open-volume defects reached before the production of new predominant defects.
Formation and characterization of swelled nano-porous structures on ion-irradiated Ge surfaces
Authors: Yanagisawa Junichi , Ogushi Keiji , Takarabe Kentaro , Gamo Kenji , Akasaka Yoichi
Published: April 2011

Single crystal germanium (Ge) surfaces were irradiated with 100 keV Ga ions at room temperature at doses up to 3×1017 cm-2 and were observed by a scanning electron microscope (SEM) and an atomic force microscope (AFM). It is found that the Ga-irradiated regions swelled and nano-porous structures were formed on the surface after the Ga irradiation up to a dose of about 2×1017 cm-2, but the region was etched by the Ga irradiation for larger doses. The atomic composition of the swelled and etched surfaces was investigated by an Auger electron spectroscopy (AES), but no Ga signal was observed, indicating that the precipitation of Ga did not influence on these characteristics of the Ga-irradiated Ge surfaces. To investigate the water resistance of such nano-porous structures, the sample was dipped in water up to 10 hours, and the surface was observed using SEM and AFM. It is found that the swelled structures were maintained, but the etched region formed by larger-dose irradiation was partially peeled off. This indicates that the nano-porous structures can be used under water environments as a functional surface, such as filters, and deep etching can be performed by larger dose irradiations and dipping the sample in water.
Fabrication of patterned domains with graphitic clusters in amorphous carbon using a combination of ion implantation and electron irradiation techniques
Authors: Iwamura Eiji , Aizawa Tatsuhiko
Published: April 2011

Fabrication of domains containing graphitic structures in amorphous carbon (a-C) films was demonstrated. Amorphous carbon thin films with 200 nm thickness were deposited on Si substrates by ion-beam sputtering. Iron atoms in a range from 4×1013 to 3.7×1016 cm-2 were doped to the a-C films by an ion implantation technique through a nickel mask with a grid of square windows of 500×500 μm and a net of 50 μm in width as a template. After removing the metal mask, the partly Fe-containing a-C films were exposed to a low-energy electron shower. In the regions where Fe atoms were implanted, Fe were crystallized and preferably diffused toward the film surface leaving graphitic structures more than 10 nm in size in the interior of the amorphous carbon films. On the other hand, the masked regions, where Fe atoms were not implanted, remained amorphous. The results suggest that regions, which consist of amorphous domains and graphitic domains, can be intentionally arranged in a-C thin films.
SIMS Depth Profiling Free of Martix Effects
Authors: Huber Peter , Karl Helmut , Stritzker Bernd
Published: April 2011

We present a method of determining elemental depth profiles with secondary ion mass spectrometry (SIMS) corrected by all non-linearities between the SIMS countrate and the elemental concentration caused by chemical matrix effects, resulting in an absolute concentration depth profile. The key to this method is a low dose ion implantation step of corresponding reference isotopes prior to SIMS depth profiling. Spectra evaluation is performed on the basis of a selfconsistent evaluation in which the depth dependent influence of the matrix is determined. The technique is demonstrated for sequentially high dose ion implanted Cd and Se in SiO2.
Characterization of Plasma Immersion Deposited Multilayer Coatings by Ion Beam Techniques Combined with Energy Filtered Transmission Electron Microscopy
Authors: Schwarz Florian , Lindner Joerg K. N. , Häeberlen Maik , Thorwarth Goetz , Hammerl Claus , Assmann Walter , Kuhn Marcus , Stritzker Bernd
Published: April 2011

Multilayered and nanostructured coatings of amorphous carbon (DLC), silicon composite multilayers and nanocluster containing films today have great potential for applications as hard coatings, wear reduction layers and as diffusion barriers in biomaterials. Plasma immersion ion implantation and deposition (PIII&D) is a powerful technique to synthesize such films. The quantitative nanoscale analysis of the elemental distribution in such multielemental films and thin film stacks however is demanding.

In this paper it is shown how the high spatial resolution capabilities of energy filtered trans-mission electron microscopy (EFTEM) chemical analysis can be combined with accurate and standard-less concentration determination of ion beam analysis (IBA) techniques like Rutherford Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA) to achieve absolute and accurate multielement concentration profiles in complicated nanomaterials.
Deposition of ITO Film on Ion Beam Treated Polymers
Authors: Hsiao Shih Hsiu , Yamaguchi Tetsuro , Tanaka Yoshikazu , Ide-Ektessabi Ari
Published: April 2011

Indium oxide doped with tin oxide, ITO, is extensively used to fabricate transparent conductive coatings. ITO thin film on flexible substrates has been used in applications including touch panel contacts, electrodes for LCD and Plasma displays. ITO thin film can be deposited onto polymer substrates using electron-beam evaporation. Surface modification of polymer substrate improves its superficial properties, adhesion in particular, to meet specific requirements while retaining the good mechanical properties of the substrates. In this study, a system consists of a linear ion beam and an electron beam which have been developed in vacuum. The linear ion beam treats the polymer surface while simultaneously the ITO thin film is deposited onto the surface using electron-beam evaporation. We demonstrated that polymer surface treated with the ion beam has been improved. Moreover, the linear ion beam source provides good uniformity of surface treatment and is very suitable for production-scale processes. An integrated electron-beam evaporation and linear ion beam system significantly increases the chemical compatibility of a polymer surface to an over-layer.
Low Temperature Annealing Effects on Magnetron Sputtered Ni(V)/Al Reactive Coatings
Authors: Blickley Matthew P. , Soroka Nicholas A. , Demaree John Derek , Hirvonen James K. , Dehmer Peter G.
Published: April 2011

Reactive nanofoil coatings of magnetron-sputtered aluminum and nickel/vanadium bilayers were characterized for reliable debonding of segmented carbon composite or metallic structures to be used in future Army applications. We determined the initiation energies of multilayer stacks by discharging an electric spark from a fixed capacitor bank and varying DC voltage before and after low temperature annealing, which resulted in varying amounts of interfacial interdiffusion observable by Rutherford backscattering spectrometry (RBS). The propagation velocity of the reaction was also measured using high speed video photography. Significant increases in initiation energy and decreasing propagation velocities were observed with increasing anneal times and temperatures, in agreement with the RBS results and existing literature discussion of reaction mechanisms. Initiation sensitivity and propagation velocity were both impacted by varying the stoichiometric ratio of Al and Ni/V, and the propagation rate was also affected by the nature of the substrate. These results allow for the optimization of both reliable initiation and long term, low temperature storage stability of the final reactive coatings for debonding applications.
Time-resolved Photoconductivity as a Probe of Carrier Transport in Microcrystalline Silicon
Authors: Reynolds Steve
Published: April 2011

The use of transient photoconductivity techniques in the investigation of carrier transport in microcrystalline silicon is described. Results are presented which highlight variations in transport parameters such as carrier mobility and density of states with structure composition. Hole mobility is significantly enhanced by crystalline content in the film of 10% or less. The density of states inferred from transport measurements parallel to and at right angles to the direction of film growth differ somewhat, suggesting that transport may be anisotropic.
Characterization of the Evolution in Metastable Defects Created by Recombination of Carriers Generated by Photo-generation and Injection in p-i-n a-Si:H Solar Cells
Authors: Deng Jingdong , Rross Benjamin , Albert Mathew , Collins Robert , Wronski Christopher
Published: April 2011

The creation of metastable defects in the bulk of the intrinsic layers of a-Si:H p-i-n solar cells by recombination of photo-generated carriers as well as those injected under far forward bias has been investigated. The evolutions in the defects, created with volume-absorbed red light at open circuit voltage and constant far forward bias currents, were characterized with the Shockley-Reed-Hall recombination obtained from the dark currents under low forward bias voltages. This allowed the kinetics to be studied at different temperatures in the absence of isothermal annealing. It is found that the form of the kinetics obtained with the two methods are the same and a detailed study was carried out with currents from 1 to 100mA/cm2 with carrier injection during which the electron and hole concentrations remain essentially constant. This kinetics is similar to that reported for thin film results exhibiting stretched exponential behavior with a t1/3 relation over a limited regime before the onset of saturation. By separating the contributions of the metastable defects from the intrinsic defects, their evolution is found to have a t1/2 dependence over the entire range prior to the onset of saturation. Since these kinetics also exhibit an (intensity)2t dependence they point to a rate equation for the creation of metastable defects, Nms, dNms / dt ~ (intensity)2 / Nms, which is suggestive of new creation mechanisms for SWE defects.
Properties of Nanocrystalline 3C-SiC:H and SiC:Ge:H Films Deposited at Low Substrate Temperatures
Authors: Miyajima Shinsuke , Yamada Akira , Konagai Makoto
Published: April 2011

We have investigated properties of nanocrystalline hydrogenated cubic silicon carbide (nc-3C-SiC:H) and silicon carbide: germanium alloy (nc-SiC:Ge:H) films deposited by hot-wire chemical vapor deposition (HWCVD) at low temperatures of about 300°C. we found that the density of charged defects was strongly influenced by grain size of the films. In-situ doping into nc-3C-SiC:H films was also carried out. N-type nc-3C-SiC:H films were successfully deposited by using phosphine (PH3) and hexamethyldisilazane (HMDS) as dopants. We found that HMDS is an effective n-type dopant for low temperature deposition of nc-3C-SiC:H films by HWCVD. For the deposition of p-type nc-3C-SiC:H with trimethylaluminum (TMA), it was found that the substrate temperature of above 300°C is required to activate the acceptors. We added dimethylgermane (DMG) into mixture of MMS and H2 to prepare nc-SiC:Ge:H films. The nc-SiC:Ge:H films with Ge mole fraction of 1.9% were successfully deposited.
Interface Study Of Nanocrystalline Silicon and Crystalline Silicon Using Microwave Photoconductivity Decay
Authors: Farrokh Baroughi Mahdi , Sivoththaman Siva
Published: April 2011

This paper presents a measurement technique for studying of the interface between a nanocrystalline silicon (nc-Si) film and a crystalline silicon (c-Si) substrate using microwave photoconductivity decay (MWPCD). The nc-Si films were deposited using plasma enhanced chemical vapor deposition of highly hydrogen-diluted silane. The films were deposited on both sides of the high purity float-zone (FZ) Si wafers. The high resolution transmission electron microscope (HRTEM) analysis of the interface and the characterization of the effective excess carrier lifetime of the samples using MWPCD revealed the following results: (i) The crystallinity of the deposited nc-Si films is very high. The nc-Si film follows the crystal orientation of the substrate such that not a well-defined boundary between nc-Si film and the c-Si substrate is observed. (ii) A surface recombination velocity of less than 10 cm/s was measured for the interface region of the nc-Si/c-Si junctions. (iii) A small discontinuity in the band-energy diagram of the interface region was observed.
Microstructure Characterization of Amorphous Silicon-Nitride Films by Effusion Measurements
Authors: Beyer Wolfhard , Dekkers H.F.W.
Published: April 2011

The microstructure of a-Si:N:H films, which are applied as antireflection coating and for defect passivation in multicrystalline silicon (mc-Si) solar cells, was studied by gas effusion experiments. The results show for as-deposited material of low substrate temperatures (TS = 200 – 300°C) a predominant diffusion of molecular hydrogen for temperatures up to 800°C in agreement with the presence of interconnected openings (voids). At higher substrate temperatures, the material has a more compact structure and atomic hydrogen is the dominant diffusing species in the accessible temperature range. Annealing effects were also studied. The results are consistent with the concept that atomic hydrogen released from the a-Si:N:H coating serves for defect passivation in μc-Si solar cells.
Effect of Hydrogen Dilution on Structure and Electronic Properties of Ge:H and GeYSi1-Y Films Deposited by Low Frequency Plasma
Authors: Kosarev Andrey , Sanchez L. , Torres A. , Felter T. , Ilinskii A. , Kudrjavtsev Y. , Asomoza R.
Published: April 2011

We report on a systematical study of growth rate, surface morphology, hydrogen and oxygen incorporation, optical and electrical properties in Ge:H and GeYSi1-Y:H, Y> 0.85 films, deposited in a capacitive reactor by low frequency PE CVD. Silane and germane were used as feed gases diluted by hydrogen. Hydrogen dilution characterized by R= QH2/[QSiH4+QGeH4], where QH2, QSiH4, and QGeH4 are gas flows of hydrogen, silane and germane, respectively. The flow was varied in the range of R=20 to 80. Composition of the films was characterized by SIMS profiling. We did not observed a significant change of the deposition rate Vd in GeYSi1-Y:H films in all the range of R, while for Ge:H films Vd was significantly reduced after R=50. AFM characterization of the surface morphology demonstrated that at R=50 average height (R) reached maximum in both Ge:H and GeYSi1-Y:H films, while average diameter (R) had a minimum in GeYSi1-Y:H films and maximum in Ge:H films. Both Ge:H and GeYSi1-Y:H films demonstrated change of E04 in the studied range of R, and a minimum clearly appeared in E at R=50-60 suggesting significant reduction in weak bonds of these films. The activation energy of conductivity Ea slightly increases with R in Ge:H films and shows no definitive trend in GeYSi1-Y:H: films. Both FTIR and SIMS data show a general trend of reducing hydrogen and oxygen content with R. These two types of films showed different behavior and correlations between surface morphology and optical and electrical properties.
Detection of SiH3 radicals and cluster formation in a highly H2 diluted SiH4 VHF plasma by means of time resolved cavity ring down spectroscopy
Authors: Nagai Takehiko , Smets Arno H. M. , Kondo Michio
Published: April 2011

The spatial distribution of the SiH3 radicals between the electrodes of a hydrogen diluted silane VHF plasma under thin film hydrogenated microcrystalline silicon (μc-Si:H) growth conditions has been measured using the time resolved cavity ringdown (τ-CRD) absorption spectroscopy technique. The μc-Si:H growth rate is estimated from the measured spatial SiH3 profiles using a simple model based upon diffusion controlled flux of SiH3 radicals to the electrode surface, where the SiH3 can react with the film surface. The calculated value of μc-Si:H growth rate roughly agrees with the value of the experimentally determined growth rate. This agreement implies that the SiH3 radical is the main growth contributor to the μc-Si:H growth. Furthermore, the τ-CRD reveals the growth kinetics of the clusters in the plasma by light scattering at these clusters on time scales of 1 s after the plasma ignition.
Thermally-Stimulated Currents in Thin-Film Semiconductors: Analysis and Modelling
Authors: Main Charles , Souffi Nacera , Reynolds Steve , Aneva Zdravka , Brüggemann Rudi , Rose Mervyn
Published: April 2011

This paper investigates the robustness of the thermally stimulated current technique as a method to determine the density of states distribution in thin film semiconductors under a wide range of conditions. Numerical simulation is used to solve the non-linear time-dependent rate equations for free and trapped charge in systems with continuous and structured DOS profiles. We explore the derivation of energy and density scales from temperature and conductivity data. We examine for these systems the limits of the method's apparent immunity to varying conditions of strong and weak retrapping, and investigate the corrections required for variations in carrier lifetime with temperature.
Pulsed Laser Deposition of Boron Doped Si70Ge30
Authors: Sedky Sherif , ElDeftar Ibrahim , Mortagy Omar
Published: April 2011

The main objective of this work is to investigate the possibility of combining pulsed laser deposition (PLD) and pulsed laser annealing to realize p-type Si1-xGex thin films suitable for post-processing MEMS on top of standard pre-fabricated driving electronics. The main advantage of this approach is that the substrate is kept at a CMOS backend compatible temperature throughout the deposition and thus the MEMS integration process will have no thermal impact on the underlying electronics. In addition, it is demonstrated that PLD Si1-xGex has good adhesion to SiO2 and accordingly there is no need for a silicon nucleation which is the case for LPCVD and PECVD. Furthermore, this technique is much more economical than CVD as it does don't imply using expensive gas precursors such as germane and silane.
Growth and Electronic Properties of Nanocrystalline Si
Authors: Dalal Vikram , Muthukrishnan Kamal , Saripalli Satya , Stieler Dan , Noack Max
Published: April 2011

Nanocrystalline Silicon is an important electronic materials for solar cells, for display devices and for sensors. In this paper, we discuss the influence of ions on the growth and properties of thenanocrystalline Si:H material. Using a unique growth geometry, combination of hot wire and ECR plasma growth, we show that low energy ion bombrdment is beneficial for growing high quality materials. Ion bombardment by H is shown to etch the films during growth and also promote crystallinity. The results on film growth are compared with simulations of growth using the SRIM program. The electronic properties measured include mobilities of both electrons and holes in device-type structures, carrier lifetimes, diffusion lengths, defect densities and capture cross-sections for holes. Electron mobility is found to increase with grain size, with a minimum mobility being in the range of 1 cm2/V-s. The hole mobility is also in this range, and three different methods of measuring it give approximately the same value. The capture cross-section for holes is of the order of 1-2 × 10-16 cm2. The lifetime of carriers is found to depend inversely on the defect density, implying that the recombination is trap controlled.
Numerical Simulation of Microcrystalline Silicon Growth on Structured Substrate
Authors: Python Martin , Vallat-Sauvain Evelyne , Bailat Julien , Ballif Christophe , Shah Arvind
Published: April 2011

The growth of thin-film silicon close to the amorphous/microcrystalline transition is qualitatively described by a 3D - discrete dynamical growth model on a cubic lattice. The result of this simulation is a representation of the microstructure of the layer as a function of time, i.e. computer-generated animations of growing microcrystalline silicon layers. It permits to follow the evolution of the nucleation and of the growth of the crystalline phase, the surface roughness, the average crystalline volume fraction and the void volume fraction. In these computer simulations, the effects of the substrate surface morphology and of the distribution of particles incidence angle have been studied.

Comparison between simulated normal and isotropic incidence on structured substrates indicates that, under microcrystalline growth conditions, shadowing effects lead to the occurrence of cracks in the simulated microstructure. These effects are also evidenced experimentally in the case of μc-Si:H silicon layers deposited by very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) on periodic and random nanostructured substrates.
Fast Deposition of Highly Crystallized Microcrystalline Si Films Utilizing a High-Density Microwave Plasma Source for Si Thin Film Solar Cells
Authors: Jia Haijun , Shirai Hajime , Kondo Michio
Published: April 2011

In this work, we investigate the influences of source gas supply method and dc substrate bias on the deposition rate as well as structural properties of μc-Si films and demonstrate the high rate synthesis of highly crystallized μc-Si films with improved film density by using a high-density and low-temperature microwave plasma source. A high flux of SiH3 and atomic hydrogen on film growing surface achieved through adjusting SiH4 gas supply configuration is effective for the fast deposition of highly crystallized μc-Si films and for the improvement of film mass density. Appropriate ion bombardment under moderate negative dc substrate bias along with the suppression of contributions of detrimental species to film growth also account for the improvement in properties of resulting films. As a consequence, a very fast deposition rate of ~65 Å/s was achieved with a high Raman crystallinity Ic/Ia>3 and a low defect density of (1-2)×1016 cm-3 despite a high silane concentration of 67%.
Amorphous Silicon as an Active Material in Optical Resonators
Authors: Hohlfeld Dennis , Zappe Hans
Published: April 2011

The application of amorphous silicon as a thermo-optically active material in MEMS-based, tunable optical filters is presented. The thin film interference filter employs a solid-state silicon cavity and silicon-based distributed Bragg reflectors (DBR). Tuning is achieved by varying the the resonator's refractive index and thus its optical thickness through thermal modulation. The filter is configured as a membrane and operates up to a temperature of 450 °C. Such a filter is essential for monitoring and reconfiguration of optical data communication networks and is also applicable for chemical and gas sensing.
Role of the Oxide Layer on the Performances of a-Si:H Schottky Structures Applied to PDS Fabrication
Authors: Aguas Hugo , Pereira Luis , Costa Daniel , Raniero Leandro , Fortunato Elvira , Martins Rodrigo
Published: April 2011

In this work we present results of studies performed on Schottky and MIS (metal-insulator – semiconductor) PSD (position sensitive detectors) structures: substrate (glass)/ Cr (300 nm) / a-Si:H [n] (37 nm) / a-Si:H [i] (600 nm) / SiO2 (1.5 nm – for the MIS) / Au (7 nm). The effect of the interfacial oxide layer between Au and a-Si:H, for the MIS structures, was studied and compared with the Schottky, in order to determine how beneficial it could be for device performances and time degradation. For doing so, the Au thickness of 70Å was deposited by thermal evaporation on an oxide free (Schottky) and oxidized (20Å) (MIS) a-Si:H surfaces. These structures were characterized by SIMS, RBS, SEM and AFM in order to correlate the obtained diffusion profile of Au at the interface and the topography with the presence of the oxide at the interface. The results show that the Au inter-diffuses very easily in the oxide free a-Si:H surface, even at room temperature, degrading the devices performance. On the other hand, the MIS structures, with their interfacial oxide present no structural changes after annealing and the PSD produced are stable. We believe that this effect is associated with the barrier effect of the interfacial oxide that prevents the Au diffusion. The optimized 1D MIS sensors are stable and exhibit a linearity error as low as 0.8 % and sensitivities of 33 mV/cm for a 5 mW spot beam intensity at a wavelength of 532 nm, while the Schottky sensors showed a time degradation of their characteristics.
Un-cooled Micro-bolometer with Sandwiched Thermo-sensing Layer Based on Ge Films Deposited by Plasma
Authors: Kosarev Andrey , Moreno Mario , Torres Alfonso , Ambrosio Roberto
Published: April 2011

We have fabricated and studied an un-cooled micro-bolometer with thermo-sensing layer sandwiched between two electrodes. The micro-bolometer has “bridge” configuration to provide sufficient thermo isolation of the thermo-sensing layer and is made on the surface of silicon wafer by means of surface micro-machining technique. The support layer of SiN and thermo-sensing layer of a-Ge:H,F have been deposited by low frequency PE CVD. The active area of the thermo-sensing layer is Ab=70x66 μm2. Temperature dependence of conductivity σ(T), current-voltage characteristics I(U), spectral noise density and thermal response time have been measured to characterize operation and to determine main performance characteristics. Activation energy of the thermo-sensing layer was Ea=0.34 eV providing thermal coefficient of resistance α=0.043 K-1. Pixel resistance was in the range Rb=(1÷30)x105 Ohm. Current and voltage responsivities were in the range RI=0.3÷14 AW-1 and RU=(1÷2)x105 VW-1, respectively. The value of detectivity was in the range of D*=(1÷40)x108 cmHz1/2W-1 and response time was τ=100 μs. The characteristics obtained in this micro-bolometer with sandwiched thermo-sensing layer make it promising for further development.
Dynamic Measurements of MEMS-Based Field Effect Transistors Using Scanning Capacitance Microscopy
Authors: Anderson Meredith L. , Young R.W. , Nakakura C.Y.
Published: April 2011

In this research, we have employed scanning capacitance microscopy (SCM) to image 2D carrier profiles of a MEMS device. Multiple device states are exercised and examined for changes in carrier response as a function of applied bias. First, experimental and simulated dopant profiles of the source and drain pn junctions were measured with device contacts grounded. Their comparison revealed good agreement. Scanning capacitance microscopy was then used to image changes in carrier distribution within the channel of the device while independent bias voltages were applied to the source, gate, drain, and well regions. Device operation was confirmed by simultaneously measuring the drain current. The SCM image contrast directly beneath the gate was observed to change as a function of applied gate bias voltage.
Ambipolar Thin-Film Transistors Fabricated by PECVD Nanocrystalline Silicon
Authors: Lee Czang-Ho , Sazonov Andrei , Rad Mohammad R. E. , Chaji G. Reza , Nathan Arokia
Published: April 2011

We report on directly deposited plasma-enhanced chemical vapor deposition (PECVD) nanocrystalline silicon (nc-Si:H) ambipolar thin-film transistors (TFTs) fabricated at 260 °C. The ambipolar operation is achieved adopting Cr metal contacts with high-quality nc-Si:H channel layer, which creates highly conductive Cr silicided drain/source contacts, reducing both electron and hole injection barriers. The n-channel nc-Si:H TFTs show a field-effect electron mobility (meFE) of 150 cm2/Vs, threshold voltage (VT) ~ 2 V, subthreshold slope (S) ~0.3 V/dec, and ON/OFF current ratio of more than 107, while the p-channel nc-Si:H TFTs show a field-effect hole mobility (mhFE) of 26 cm2/Vs, VT ~ -3.8 V, S ~0.25 V/dec, and ON/OFF current ratio of more than 106. Complementary metal-oxide-semiconductor (CMOS) logic integrated with two ambipolar nc-Si:H TFTs shows reasonable transfer characteristics. The results presented here demonstrate that low-temperature nc-Si:H TFT technology is feasible for total integration of active-matrix TFT backplanes.
An Asymmetric Dual Gate Poly-Si TFTs for Improving Hot Carrier Stress Stability and Kink Effect Suppression
Authors: Park Joong Hyun , Nam Woo Jin , Lee Jae Hoon , Han Min Koo
Published: April 2011

An asymmetric dual gate poly-Si thin film transistors (TFTs), which is consist a long-gate TFT and a short-gate TFT, were fabricated in order to suppress the kink current and increase the reliability. The long-gate TFT operates in a linear regime and limits the total current flow by its current operation region. The asymmetric dual-gate does not exhibit from the kink current in a high drain bias due to the distribution of lateral electric field. The asymmetric dual-gate structure improves kink-free characteristics compared with conventional single and dual-gate TFTs. The hot-carrier stress reliability is successfully improved due to kink current suppression.
A Novel Self-Aligned Field Induced Drain Polycrystalline Silicon Thin Film Transistor Fabricated by using a Selective Side Etch Process
Authors: Liao Ta-Chuan , Wu Chun-Yu , Chien Feng-Tso , Tsai Chun-Chien , Chen Hsiu-Hsin , Kung Chung-Yuan , Cheng Huang-Chung
Published: April 2011

A novel T-shaped-gated (T-Gate) polycrystalline silicon thin-film transistor (poly-Si TFT) with vacuum gaps has been proposed and fabricated only with a simple process. The T-Gate structure is formed only by a selective undercut-etching technology of the Mo/Al bi-layers. Then, vacuum gaps are in-situ embedded in this T-Gate structure subsequent to capping the SiH4-based passivation oxide under the vacuum process chamber. Experimental results reveal that the proposed T-Gate poly-Si TFTs have excellent electrical performance, which has higher maximum on-off current ratio of 4.6 e107, and the lower off-state leakage current at VGS = -10 V and VDS = 5V of about 100 times less than that of the conventional one. It is attributed to the additional undoped offset region and the vacuum gap to reduce the maximum electric field at drain junction while ascribed to the sub-gate to maintain the on-current. Therefore, such a T-Gate poly-Si TFT is very suitable for the applications and manufacturing in active matrix liquid crystal displays (AMLCDs) and active matrix organic light emitting diodes (AMOLEDs).
Novel approaches of light management in thin-film silicon solar cells
Authors: Krc Janez , Zeman M. , Campa A. , Smole F. , Topic M.
Published: April 2011

In order to improve light trapping in thin-film silicon solar cells two novel approaches are investigated in this article: angle-selective management of light scattering inside the solar cell and wavelength-selective manipulation of high reflectance or transmittance of light. Diffraction gratings are analyzed as a representative of the first approach. Haze and angular distribution function of scattered (diffracted) light in reflection are measured for aluminum-based rectangular periodic gratings with different period and height of the rectangles. High haze values in specific wavelength region and scattering angles of the investigated gratings measured in air and water agree very well with the theoretical predictions. Considering the actual optical situation in microcrystalline silicon solar cells, optimal period and height of the rectangular gratings applied as a back reflector are calculated for obtaining the total reflection at the front interfaces. In the frame of the second approach, photonic-crystal-like structures are introduced. By means of optical simulations photonic-crystal-like structures are investigated for two possible applications: an intermediate reflector in a micromorph silicon solar cell with wavelength-selective reflectivity and a dielectric back reflector with a high reflectance in the long-wavelength region. The photonic crystal structure consisting of sequences of n-doped amorphous silicon and ZnO layers is designed for the efficient intermediate reflector. For the back reflector with a high reflectance the structures with intrinsic amorphous silicon, SiO2, MgF2 and TiO2 are proposed.
Thin-film polycrystalline-silicon solar cells on high-temperature glass based on aluminum-induced crystallization of amorphous silicon
Authors: Van Gestel Dries , Gordon Ivan , Carnel Lode , Pinckney Linda R. , Mayolet Alexandre , D'Haen Jan , Beaucarne Guy , Poortmans Jef
Published: April 2011

Efficient thin-film polycrystalline-silicon (pc-Si) solar cells on foreign substrates could lower the price of photovoltaic electricity. Aluminum-induced crystallization (AIC) of amorphous silicon followed by epitaxial thickening at high temperatures seems a good way to obtain efficient pc-Si solar cells. Due to its transparency and low cost, glass is well suited as substrate for pc-Si cells. However, most glass substrates do not withstand temperatures around 1000°C that are needed for high-temperature epitaxial growth. In this paper we investigate the use of experimental transparent glass-ceramics with high strain-point temperatures as substrates for pc-Si solar cells. AIC seed layers made on these substrates showed in-plane grain sizes up to 16 μm. Columnar growth was observed on these seed layers during high-temperature epitaxy. First pc-Si solar cells made on glass-ceramic substrates in substrate configuration showed efficiencies up to 4.5%, fill factors up to 75% and open-circuit voltage (Voc) values up to 536 mV. This is the highest Voc reported for pc-Si solar cells on glass and the best cell efficiency reported for cells made by AIC on glass.
Ultra Shallow Junctions Optimization with Non Doping Species Co-implantation
Authors: Cagnat Nathalie , Laviron Cyrille , Mathiot Daniel , Duriez Blandine , Singer Julien , Gwoziecki Romain , Salvetti Frédéric , Dumont Benjamin , Pouydebasque Arnaud
Published: April 2011

The permanent decrease of the transistor size to improve the performances of integrated circuits must be accompanied by a permanent decrease of the depth of the source-drain junctions. At the same time, in order to keep acceptable sheet resistance values, the dopant concentration in the source-drain areas has to be continuously increased. A possible technological way to meet the junction depth and abruptness requirements is to use co-implantation of non doping species with classical implantations, especially for light ions as B or P.

In order to clarify the complex interactions occurring during these co-implantation processes, we have performed an extensive experimental study of the effect of Ge, F, N, C and their combinations on boron. A special interest was given to the overall integration issues. We will show that it is required to optimize the respective locations of co-implanted species with respect to the B profiles (more precisely the ion implantation damage locations), as well as the co-implanted species doses, to get an acceptable compromise between the efficient diffusion decrease required for the junction abruptness and depth, and a reasonable current leakages.