bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of the Concentration of Ga on Junction Formation in Thin-film ZnO/CdS/CuInXGal-XSe2 /Mo Photovoltaic Devices
Authors: Matson R. J. , Contreras M. A. , Tuttle J. R. , Swartzlander A. B. , Parilla P. A. , Noufi R. 
Published: April 2011

AbstractCharge-collection microscopy (CCM)—commonly known as electron-beam-induced current [EBIC] microscopy—in a scanning electron microscope (SEM) was used to obtain charge-collection efficiency profiles of cleaved thin-film ZnO/CdS/CuInXGal-XSe2/Mo photovoltaic devices on glass substrates, with x varied between 0 and 100%. We observed considerable variation in the EBIC peak position, the uniformity (between and within devices), and overall charge-collection profile of the junction as a function of Ga concentration. Whereas using only CuInSe2 (CIS) absorber material results in a rather wide and buried junction in the CIS, the systematic addition of Ga to the p-CuInSe2 matrix affects the conductivity type of the material, thereby creating an increasingly abrupt, uniform, and shallow junction near the heteroface. Although the substitution of Ga for In improves overall device performance up to ∼ X=25% and the Voc continues to improve, the Jsc, FF, and device efficiency degrade with additional Ga.
Enhanced Mo Adhesion on Glass With Cr Interlayers for Copper Indium Diselenide Thin Film Devices
Authors: Alleman Jeff , Ginley Dave , Hasoon Falah , Asher Sally , Noufi Rommel 
Published: April 2011

AbstractA key element of current Copper Indium Diselenide (CIS) and Copper Indium Gallium Diselenide (CIGS) thin film solar cells is the use of a Mo back contact on soda lime glass (SGL). Because of surface preparation problems, high process temperatures, and mismatch of thermal expansion coefficients, adhesion of the Mo to the soda lime glass can be variable. Also beneficial is the Na facile diffusion of the glass into the absorber layer. We report on the use of thin Cr interlayers to improve the adhesion at the Mo/glass interface. The films were subsequently annealed in vacuum under normal process conditions. Adhesion was excellent and quite uniform for Mo layers with a Cr interlayer of 50 to 800 Å compared to control samples without Cr. X-ray Photoelectron Spectroscopy (XPS) data suggests CrO bonding at the glass interface and Cr metallic bonding at the Cr Mo interface. Secondary Ion Mass Spectrometry (SIMS) data for Mo/Cr films shows diffusion of Na throughout the Mo layer identical to that for Mo alone samples. Resistivities of the films have been measured to be 11 μhms-cm, twice that for bulk material of 5.7 μohms-cm. CIGS films were then grown for comparison to films grown on Mo only substrates.
Growth and Characterization of CuInSe2Epitaxial Films for Device Applications
Authors: Niki S. , Kurafuji T. , Fons P. J. , Kim I. , Hellman O. , Yamada A. 
Published: April 2011

AbstractCuInSe2(CIS) epitaxial layers have been grown on both GaAs (001) and In0.29Ga0.71As pseudo lattice-matched substrates by molecular beam epitaxy, and characterized for device applications. Despite a large lattice mismatch of Δa/a˜2.2%, epitaxial growth of CuInSe2has been demonstrated on GaAs (001) showing their film properties strongly dependent on the Cu/In ratio. In-rich films had a large number of twins on {112} planes, and were found to be heavily compensated. On the other hand, Cu-rich films showed distinct photoluminescence emissions indicating significantly higher film quality in comparison with In-rich films. Two dimensional reciprocal x-ray intensity area mapping and cross-sectional transmission electron microscopy showed the formation of an interfacial layer in the vicinity of the CuInSe2/GaAs interface resulting from the strain-induced interdiffusion between CuInSe2and GaAs. Reduction in lattice mismatch to Δa/a˜0.2% by using In0.29Ga0.71Aspseudolattice-matched substrates made possible the growth of high quality CuInSe2with predominant free exciton emissions in their photoluminescence spectra and with residual defect densities of as low as p˜l×1017cm-3implying the growth of device quality CuInSe2epitaxial films.
Growth of CuInS2 Films on Crystalline Substrates
Authors: Hunger R. , Scheer R. , Alt M. , Lewerenz H. J. 
Published: April 2011

AbstractCuInS2 films were grown by molecular beam epitaxy (MBE) on hydrogen terminated Si(111) substrates with 4° miscut. X-ray diffraction (XRD) texture analysis reveals that CuInS2 was grown heteroepitaxially with the epitaxial relationships CuInS2(112) II Si(111) and [111] II [111]. Moreover, a substantial amount of rotational twins is observed. The crystalline order is maintained across the interface as observed by cross-sectional transmission electron microscopy (XTEM). XRD and scanning electron microscopy (SEM) investigations show that nonstoichiometric preparation greatly influences the growth morphology and leads to the formation of secondary phases.
Thin-Film Cadmium Sulfide/Cadmium Telluride Alloys
Authors: Jensen D. G. , McCandless B. E. , Birkmire R. W. 
Published: April 2011

AbstractThin films of CdTel-xSx with bulk atomic compositions, x≡[S]/([S]+[Te]), ranging from 0 to 0.45 were deposited by vacuum co-evaporation of CdTe and CdS with substrate temperatures of 200 and 250°C. X-ray diffraction analysis revealed that films with x < 0.3 were predominately single phase having the zincblende structure. Films with 0.35 < x < 0.45 contained the wurtzite modification. Lattice parameter determination indicated that each phase exists with compositions well within the miscibility gap shown on published equilibrium phase diagrams. The variation of the optical band gap with x was determined by measuring transmission and reflection of the films. Heat treatment at 415°C in the presence of CdC12 caused the films to segregate into two phases consistent with the phase diagram. If the CdCl2 is assumed to only promote the phase segregation process, then the compositions of the two phases after heat treatment may be taken as measurements of the solubility limits of S in CdTe and Te in CdS respectively. The solubility limit of S in CdTe was thus determined to be 5.8% at 415°C which is the temperature used for the common CdC12 treatment of CdTe-based solar cells. An analysis of CdTe/CdS solar cell device structures shows that the atomic composition of alloys created by interdiffusion are consistent with these solubility limits.
Effects of Magnetic Field Configuration on Rf Sputtering for CdS/CdTe Solar Cells
Authors: Compaan A. , Shao M. , Fischer A. , Grecu D. , Jayamaha U. , Contreraspuente G. , Bohn R. G. 
Published: April 2011

AbstractWe report studies of solar cells prepared by rf planar magnetron sputtering in which the films were deposited using magnetic field structures ranging from approximately balanced to strongly unbalanced in the “type II” configuration. For films grown with the unbalanced configurations, we find much stronger photoluminescence and much better cell performance than for the balanced configuration. The CdTe films show differences in electrical performance depending on magnetic field as well. These effects are interpreted as arising from the enhanced electron and ion bombardment of the film growth interface for the unbalanced magnetrons. Using two unbalanced magnetrons we have fabricated an all-rf-sputtered cell with NREL-verified efficiency of 11.66% at air mass 1.5 illumination.
Deposition Schemes for Low Cost Transparent Conductors for Photovoltaics
Authors: Delahoy A. E. , Cherny M. 
Published: April 2011

AbstractProduction requirements for transparent conductors for thin film photovoltaics are reviewed, with particular reference to magnetron sputtered zinc oxide. On-going optimization processes for ZnO:AI prepared on 0.43 m2substrates by bipolar, reactive sputtering from ZnO:A12O3targets and by reactive sputtering from a Zn:Al target are described. Optical emission from the plasma is used to study the state of the sputtering target. Attention is drawn to the spatial dependence of deposition conditions under the cathode.
High Performance Transparent Conducting Films of Cadmium Indate Prepared by Rf sputtering.
Authors: Coutts T. J. , Wu X. , Mulligan W. P. 
Published: April 2011

AbstractWe are examining various spinel-structured thin films (e.g., Cd2SnO4, Zn2SnO4) to develop higher-quality transparent conducting oxides (TCO) than more conventional materials such as indium tin oxide. Here, we report on cadmium indate (CdIn2O4, CIO), which is another member of this family. Thin films of CIO were deposited by radio-frequency (RF) magnetron sputtering, from an oxide target, onto borosilicate glass substrates. The variables included the substrate temperature, sputtering gas composition, and pressure. Film properties were measured before and after heat treatment. Characterization involved Hall effect measurements, optical and infrared spectrophotometry, X-ray diffraction, and atomic-force microscopy. Film resistivities as low as 2.3x10-4Ω cm were achieved for a film thickness of 0.55 μm. The transmittance was 90% in the visible region of the spectrum, without correction for substrate losses and without an anti-reflection coating. The plasma resonance occurred at longer wavelengths than for other materials and this, with a bandgap of approximately 3.1 eV, presents a wide window for optical transmittance. The highest mobility was 54 cm2 V-s-1 and the highest carrier concentration was 7.5x1020 cm-3.
Full-Optical Characterization of Thin Films in Photovoltaic Cells
Authors: Romanov D. A. , Victoria N. , Kalameitsev A. V. 
Published: April 2011

AbstractWe present a handy new method of optical investigation of thin semiconductor layers regardless of the substrate's composition and structure. The method was especially developed for the particular case of thin (˜ 1μm ) CdTe films obtained by means of electrochemical deposition on conducting glass for further solar cell applications. The procedure consists in transmission and reflection (or the transmission only) measurements under different thicknesses of the semiconductor layer and following semi-analytical treatment of the data. Finally we obtain the frequency dependencies of the real and imaginary parts of the refractive index for the semiconductor material of the layer.
Ftir and UV Study of Amorphous Silicon-Boron Alloys Deposited by LPCVD
Authors: Yang G.-R. , Zhao Y.-P. , Tong B. Y. 
Published: April 2011

AbstractAs-deposited and wet oxidized a-Si:B alloy deposited by low pressure chemical vapor deposition (LPCVD) with various boron content was studied by UV Spectroscopy and Fourier Transform Infrared Spectroscopy. It is found that the optical band gap of a-Si:B varies with respect to the boron content, which provides potential application probability in narrow-gap photovoltaic devices. This effect is associated with the structure change induced by B content. The oxidation behaviors of a-Si:B films with boron content 3 at.% – 25 at.% are different from those with boron content exceeded 30 at.%. Possible oxidation mechanism for different boron content a-Si:B film are proposed.
Single-Crystalline and Bamboo Al Lines Fabricated by Graphoepitaxy: Microstructure and 1/f Noise Measurements
Authors: Van Den Homberg Marc J.C. , Verbruggen A. H. , Alkemade P. F. A. , Radelaar S. 
Published: April 2011

AbstractThe continuing scaling-down of integrated circuits leads to increased metallization reliability problems, especially electromigration. We used 1/f noise measurements to study the relation between electromigration and microstructure. These measurements are very sensitive to the microstructural attributes, such as grain boundaries and dislocations. Al lines were grown by graphoepitaxy: First, a pure Al film was grown by dc magnetron sputtering on a groove pattern etched into a SiO2 substrate. The growth was then followed by an in situ rapid thermal anneal that resulted in a complete filling of the grooves with Al. These Al lines were carefully characterized with SEM and Backscatter Kikuchi Diffraction. Depending on the presence of a temperature gradient during the anneal, the lines were either nearly single-crystalline or bamboo with one grain per ∼ 3 μm. The resistivity was ∼ 2.8 μΩcm, only slightly higher than for bulk Al. We measured the 1/f noise with the two-channel ac technique at RT. We found in both bamboo as well as the single-crystalline lines a very low noise intensity; a factor two lower than in conventionally sputter deposited and annealed Al lines. No clear difference between the noise spectra of the bamboo and the single-crystalline lines was observed. We concluded that grain boundaries are not the only contributor to 1/f noise; other types of defects must play a role as well.
Characterization of the early stages of EM in Al-based metal lines by means of a HRRMT based on an extremely stable ambient temperature
Authors: D'Haeger V. , De Ceuninck W. , De Schepper L. , Stals L. M. 
Published: April 2011

AbstractA high resolution resistometric measurement technique (HRRMT) is used to study electromigration (EM) in different Al-based metal lines. Instead of using a bridge-method, the high resolution is now obtained by performing experiments in a very stable temperature environment. The main advantage of this technique is that resistance variations are measured, due to processes that occur in the tested metal line only. During EM, both resistivity and geometrical variations can occur, both resulting in a resistance change. A new method is proposed in order to separate these two contributions on-line during the whole EM-experiment. It is shown that even at low current stress, geometrical changes are the main cause for the EM-induced resistance increase.
Microstructure of Passivated Al-Cu and Al-Si-Cu Conductor Lines: Interaction of Precipitates, Defects and Mechanical Stresses
Authors: Dirks A. G. 
Published: April 2011

AbstractIn this paper the results of our investigations of passivated, narrow lines of both Al-Cu and Al-Si-Cu (0.4 at.% Cu, 1.0 at.% Si) by transmission electron microscopy will be presented. Thin alloy films have been deposited on either oxide or refractory-metal films. During the standard anneal treatment of 0.5 h at 400 °C the atomic mobility is relatively high. At this temperature the binary Al-Cu films are one-phase alloys. Depending on the cooling rate, transformation occurs into a two-phase mixture of (initially) finely distributed, Cu-enriched particles and Al. The precipitates eventually form the equilibrium θ-Al2Cu phase, which tends to form large conglomerates upon further annealing. In contrast, the ternary Al-Si-Cu films are two-phase alloys already at 400 °C: at this temperature Si precipitates are pre:sent in the Al matrix, whereas the onset of Cu precipitation is not far below this temperature.
Influence of Solute Additions on Electromigration in Aluminum
Authors: Kim Choong-Un , Morris J. W. , Génin F. Y. , Fluss M. J. 
Published: April 2011

AbstractThis study investigates the effect of solute additions on electromigration in Al-based thin film binary alloys. The “cross-strip” technique was used to observe solute electromigration and its influence on Al electromigration. The results of electromigration tests on five alloy additions, Ag, Au, Cu, Pd and Ni, are presented. It is concluded that beneficial solutes have two characteristics. First, they have a large, negative effective valence (Z**). Second, they have sufficient solubility in Al at test temperature to provide a reservoir of mobile atoms. Ag and Au are relatively ineffective because of their low effective valence. Pd and Ni appears to be relatively ineffective because of their low solubility at test temperature. Only Cu satisfies both criteria.
Copper Diffusion Into Aluminum-Silicon Metallizations by Accelerated Thermal and Electrical Stressing
Authors: Ramseyer G. O. , Walsh L. H. , Beasock J. V. , Helbig H. F. , Lacoe R. C. , Brown S. 
Published: April 2011

AbstractPatterned 930 nm Al(1%-Si) interconnects over 147 nm of Cu were electromigration lifetime tested at 1.0–1.5 × 105 A/cm2 at 250 °C. The morphology of the surfaces of the electromigrated stripes with different line widths and times to failure were characterized by atomic force microscopy, and changes in surface roughness were compared. The diffusion of copper into the electromigrated aluminum stripes was determined by depth profiling using Auger electron spectroscopy. In particular, areas where hillocks formed were examined and compared to areas of median roughness.
Residual Gas Phase Contamination of Al-Cu Alloy Films and its Effect on Electromigration Behavior
Authors: Hashim Imran , Raaijmakers Ivo J. , Adler Glen , Sidhwa Ardy , Chopra Sudhir 
Published: April 2011

AbstractThe major sources of impurities in sputtered Al alloy films for interconnects, prepared by physical vapor deposition include those originating from the target material, residual gases present in the vacuum system, and those introduced through the gas delivery system. In this study, we report the effect of impurities incorporated from residual gases present in vacuum systems on the electromigration performance of 0.6 μm wide Al-l%Cu lines. Controlled leaks of isotope gases H2O18, N215, O218, and C13H4, in 10−6 10−9 Torr range, were introduced into a PVD tool during the sputtering process. Using these isotope gases, the impurities originating from residual gases were distinguished from those originating from other sources of impurities. The sputtering target was found to be the major source of H and O impurities in the film, whereas N atoms are introduced in the film mainly through the gas phase. Furthermore, N atoms in the film were found to affect its electromigration behaviour to a larger extent than O and H.
Generation of Hole Traps in Silicon Dioxide Under Fowler-Nordheim Stress
Authors: Brożek T. , Chan Y. D. , Viswanathan C. R. 
Published: April 2011

AbstractHigh field electron injection in silicon oxide layers in metal-oxide-semiconductor system is widely known to degrade thin silicon oxide layers and the silicon-oxide interface, eventually leading to catastrophic oxide breakdown. In this work we report generation of hole traps under high-field stressing of thermal silicon dioxide layers on silicon. Excess hole trapping on newly generated hole traps is observed by substrate hot-hole injection in 9 nm oxide PMOS transistors after high-field Fowler-Nordheim stress followed by standard post-metallization annealing in nitrogen. The concentration of generated traps is stress-polarity dependent and increases with electron fluence during degrading stress. Relaxation behavior under switching oxide fields indicates that the nature of hole trapping sites is different from anomalous positive charge centers. A correlation of density of generated hole traps with the amount of generated electron traps shows that both types of traps are effectively generated in the oxide layer under Fowler-Nordheim tunneling electron injection.
Transient Photocurrent Spectroscopy of Trap Levels in Ultra-Thin SiO2 Films
Authors: Miura Y. , Fujieda S. 
Published: April 2011

AbstractStress-induced trap levels near Si/SiO2 interfaces for MOS diodes with 10 imi-thick oxides are investigated by measuring the transient photocurrent, which depends on the incident photon energy. The electron trap levels are filled by tunneling injection, and the electrons are depopulated by monochromatic light irradiation. The transient photocurrent, which is measured as an external circuit current, decays exponentially with time. Based on a proposed detrapping model, the optical cross section is estimated to be about 1×10−17 cm2 for hv=2−3 eV. The obtained photo-accessible trap density has a broad distribution at around hv=2.5 eV.
Front-End Integration Effects on Gate Oxide Quality
Authors: Lin F. , Ajuria S. A. , Ilderem V. , Masquelier M. P. 
Published: April 2011

AbstractIn this paper, the impact of several front-end processing steps (up to gate oxidation) on gate oxide integrity (GOI) is evaluated. In PBL isolation processing, the use of as-deposited amorphous silicon (a-Si), subsequently annealed during nitride deposition, results in better structural and electrical properties compared to as-deposited polysilicon or as-deposited a-Si with an extra anneal step prior to nitride deposition. Thicker or dual sacrificial schemes exhibit improved gate oxide low voltage breakdown and charge-to-breakdown. Dilute RCA chemistries during pre-gate cleaning produce equal or better surfaces for gate oxidation than the conventional non-dilute RCA with less chemical usage. As gate oxides are scaled below 100Å, lowering gate oxidation temperature is proven to result in far better gate oxide quality than maintaining process temperatures at or above 900°C and diluting oxygen in either argon or nitrogen.
A Novel Method For Studying Degradation Related To Plasma Processing Of Silicon Wafers
Authors: Lagowski J. , Hofl A. , Jastrzebski L. , Edelman P. , Esry T. 
Published: April 2011

AbstractA new generation of monitoring tools based on oxide potential and surface photovoltage measurements offers real-time, non-contact diagnostics of plasma damage, especially dielectric charge build-up, radiation damage, and heavy metal contamination. The approach relies on reusable, 10 00Åoxide monitor wafers rather than test structures. The technique generates whole wafer maps powerful for correlating plasma damage with plasma equipment characteristics.
Non-Destructive Assessment Of Semiconductor Carrier Lifetime Using Photothermal Radiometry
Authors: Amirhaghi S. , Kenyon A. J. , Federighi M. , Pitt C. W. 
Published: April 2011

AbstractOf crucial importance to all areas of the microelectronics industry is the characterisation of silicon wafer quality. An important indicator of this is carrier lifetime, and a convenient non-destructive method for its measurement is Pholothermal Radiometry. This involves the photo-generation within a semiconductor sample of electron-hole pairs. Periodic generation of carriers leads to modulation of free-carrier absorption of mid-ir radiation provided by a black body source. The fr-radiation detected from the photo-excited region is inversely proportional to the optically induced carrier density. As the modulation frequency is increased, a point is reached at which the photo-generated carriers no longer have sufficient time to decay between pulses. This frequency is dependent on the carrier lifetime. We present a description of the Photothermal Radiometric lifetime scanning instrument built at UCL. This instrument offers an accurate method for producing detailed maps of carrier lifetime across whole or part wafers. The problem of surface-state effects has been addressed by employing a broad-band uv source to optically fill the surface states of the sample under investigation. The instrument is capable of producing maps of lifetime variation with 0.5 mm resolution. Alternatively, for selected points on a wafer, the instrument can generate detailed frequercy scans of free-carrier absorption. From these, it is possible to obtain information on surface recombination velocity and diffusion length.