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Jul 2012

Volume 30, Issue 4 (partial)

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Dry etching characteristics of TaN absorber for extreme ultraviolet mask with Ru buffer layer

Wanjae Park, Ohyung Kwon, Ki-Woong Whang, and Jeongyun Lee

J. Vac. Sci. Technol. A 30, 041301 (2012); http://dx.doi.org/10.1116/1.4718420 (5 pages)

Online Publication Date: 11 May 2012

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The extreme ultraviolet (EUV) mask using reflective optics has a structure totally different from that of the conventional mask. This study investigated the dry etching characteristics of the EUV mask layer in which TaN and Ru were used as the absorber and buffer layer, respectively. The TaN absorber etching requires high etch selectivity of TaN over Ru to achieve the high EUV reflectivity. In this work, the TaN etching rate was investigated with various halogen gases in the capacitively coupled plasma type etching system. The etching rates with the fluorinated gases were higher than that with the chlorinated gas. Ru could not be etched without oxygen in all of the considered etch gases. The etching rate of TaN and its etch selectivity to Ru were increased with the increase of RF power, pressure and SF6 gas flow ratio. When the real EUV mask specimens were 100% over etched under the highest selectivity etching condition, the Ru buffer layer still remained, which was confirmed by x-ray photoelectron spectroscopy analysis. The surface roughness of etched reflective mirror was very small, and the EUV reflectivity was equivalent to that of the reference mirror (EUV reflectivity is over 60%) which was confirmed by measuring the intensity and the diffracted pattern of 13.5 nm EUV obtained using x-ray charge coupled device camera. The Ru buffer layer could be removed by the O2 plasma used in the posterior photo resist ashing process without affecting the EUV reflectivity.
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81.65.Cf Surface cleaning, etching, patterning
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.35.bt Other materials

Comprehensive computer model for magnetron sputtering. I. Gas heating and rarefaction

Francisco J. Jimenez and Steven K. Dew

J. Vac. Sci. Technol. A 30, 041302 (2012); http://dx.doi.org/10.1116/1.4712534 (13 pages)

Online Publication Date: 15 May 2012

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The complex interaction between several variables in magnetron sputtering discharges is a challenge in developing engineering design tools for industrial applications. For instance, at high pressures, rarefaction and gas heating should no longer be neglected for determining several parameters of the process. In this article, we use a comprehensive 3D reactor-scale simulator that incorporates most phenomena of interest in a self-consistent manner to simulate the transport of sputtered particles over a wide range of pressures and powers. Calculations of aluminum deposition rates and metal vapor densities are in reasonable agreement with experiments over a wide range of pressures and powers. Of the elements investigated (Al, Ti, and Cu), copper showed the greatest rarefaction (30%) due to its higher sputtering yield. Titanium, despite a slightly lower sputtering yield than Al, shows a greater rarefaction than aluminum as more particles are reflected from the target as high energy neutrals. In this case, a more efficient energy transfer process is responsible for the higher rarefaction observed in Ti sputtering when compared to Al. The authors also observed that by sputtering at a higher pressure, the probability of electron impact ionization of sputtered particles is increased and speculate about the role of this process in contrast to penning ionization, which is believed to be the dominant ionization mechanism in magnetron sputtering.
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81.15.Cd Deposition by sputtering
62.50.-p High-pressure effects in solids and liquids
52.80.-s Electric discharges
52.50.Nr Plasma heating by DC fields; ohmic heating, arcs
52.65.-y Plasma simulation
52.25.Fi Transport properties
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Tracking electron-induced carbon contamination and cleaning of Ru surfaces by Auger electron spectroscopy

Aloke Kanjilal, Mark Catalfano, Sivanandan S. Harilal, Ahmed Hassanein, and Bryan Rice

J. Vac. Sci. Technol. A 30, 041401 (2012); http://dx.doi.org/10.1116/1.4718426 (6 pages)

Online Publication Date: 17 May 2012

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Extreme ultraviolet (EUV) radiation induced growth of carbon and oxygen desorption were investigated on a Ru surface by Auger electron spectroscopy (AES) in the presence and absence of additional photoelectrons (PEs) from a focusing Ru mirror. A decrease in EUV reflectivity with carbon growth in the presence of additional PEs has been observed. Conversely, a carbonaceous Ru surface was cleaned in sequential AES, and discussed in terms of secondary electron assisted dissociation of residual hydrocarbons and water molecules, followed by a chemical reaction between adsorbed carbon and oxygen atoms.
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81.65.Cf Surface cleaning, etching, patterning
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.43.Nr Desorption kinetics
68.43.Mn Adsorption kinetics
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
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Atomic layer deposited iridium oxide thin film as microelectrode coating in stem cell applications

Tomi Ryynänen, Laura Ylä-Outinen, Susanna Narkilahti, Jarno M. A. Tanskanen, Jari Hyttinen, Jani Hämäläinen, Markku Leskelä, and Jukka Lekkala

J. Vac. Sci. Technol. A 30, 041501 (2012); http://dx.doi.org/10.1116/1.4709447 (5 pages)

Online Publication Date: 27 April 2012

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Microelectrodes of microelectrode arrays (MEAs) used in cellular electrophysiology studies were coated with iridium oxide (IrOx) thin film using atomic layer deposition (ALD). This work was motivated by the need to find a practical alternative to commercially used titanium nitride (TiN) microelectrode coating. The advantages of ALD IrOx coating include decreased impedance and noise levels and improved stimulation capability of the microelectrodes compared to uncoated microelectrodes. The authors’ process also takes advantage of ALD’s exact process control and relatively low source material start costs compared to traditionally used sputtering and electrochemical methods. Biocompatibility and suitability of ALD IrOx microelectrodes for stem cell research applications were verified by culturing human embryonic stem cell derived neuronal cells for 28 days on ALD IrOx MEAs and successfully measuring electrical activity of the cell network. Electrode impedance of 450 kΩ at 1 kHz was achieved with ALD IrOx in the authors’ 30 μm microelectrodes. This is better than that reported for any uncoated microelectrodes with equal size, even equal to that of inactivated sputtered IrOx coating. Also, stimulation capability was demonstrated. However, further development, including, e.g., applying electrochemical activation, is needed to achieve the performance of commercial TiN-coated microelectrodes.
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87.85.jc Electrical, thermal, and mechanical properties of biological matter
87.85.jj Biocompatibility
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
87.19.L- Neuroscience

Characterization studies of aluminum oxide barrier coatings on polymeric substrates

Carolin F. Struller, Peter J. Kelly, Nick J. Copeland, and Christopher M. Liauw

J. Vac. Sci. Technol. A 30, 041502 (2012); http://dx.doi.org/10.1116/1.4709451 (8 pages)

Online Publication Date: 27 April 2012

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Aluminum coatings are widely used as oxygen and water barrier layers on food packaging materials to protect the product from contamination and to extend its shelf life. Thin layers of aluminum, of the order of a few tens of nanometers, are thermally evaporated onto polymeric web in high speed roll-to-roll vacuum metallizers. More recently, transparent barrier layers, based on silica or aluminum oxide, have been introduced to allow product visibility and provide retortable, sterilizable, or microwaveable packaging. In all cases, though, the barrier characteristics are critically dependent on both the structure and properties of the coating and the nature and surface properties of the polymer film substrate. This paper, therefore, reports on characterization trials of aluminum oxide (AlOx) coatings deposited onto polyethylene terephthalate (PET) and biaxially oriented polypropylene (BOPP) film substrates. Coating structures and properties have been investigated by scanning electron microscopy and atomic force microscopy; the influence of process parameters on barrier levels has been determined; surface energies have been determined through contact angle measurements; and coating-to-substrate adhesion has been assessed using “pull-off” tests. The main findings of this study are that the barrier performance of AlOx coated PET and BOPP films strongly depends on the surface properties of the plain film and the aluminum oxide film growth. While AlOx coated PET films deliver consistent barrier results, BOPP reveals considerable variations, depending on the individual substrate.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
68.03.Cd Surface tension and related phenomena
68.35.Np Adhesion

Initiated-chemical vapor deposition of organosilicon layers: Monomer adsorption, bulk growth, and process window definition

Gianfranco Aresta, Jurgen Palmans, Mauritius C. M. van de Sanden, and Mariadriana Creatore

J. Vac. Sci. Technol. A 30, 041503 (2012); http://dx.doi.org/10.1116/1.4711762 (11 pages)

Online Publication Date: 15 May 2012

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Organosilicon layers have been deposited from 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (V3D3) by means of the initiated-chemical vapor deposition (i-CVD) technique in a deposition setup, ad hoc designed for the engineering of multilayer moisture permeation barriers. The application of Fourier transform infrared (FTIR) spectroscopy shows that the polymerization proceeds through the scission of the vinyl bond and allows quantifying the degree of conversion of vinyl groups, which is found to be larger than 80% for all the deposited layers. In situ real-time spectroscopic ellipsometry (SE) allows following all the i-CVD growth stages, i.e., from the initial monomer adsorption to the layer bulk growth. Finally, the combination of SE and FTIR has allowed defining the process window for the deposition of stable and highly cross-linked poly(V3D3) layers by tuning a key process parameter, i.e. the surface monomer adsorption.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.43.Mn Adsorption kinetics
68.65.Ac Multilayers
78.30.Jw Organic compounds, polymers
82.35.-x Polymers: properties; reactions; polymerization

In/ITO whisker and optoelectronic properties of ITO films deposited by ion beam sputtering

Jung-Hsiung Shen, Sung-Wei Yeh, and Lay Gaik Teoh

J. Vac. Sci. Technol. A 30, 041504 (2012); http://dx.doi.org/10.1116/1.4716468 (6 pages)

Online Publication Date: 15 May 2012

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ITO films were deposited on a glass substrate using ion beam sputtering, with oxygen flow rates from 0.5 to 2 sccm. The films consisted of randomly oriented ITO nanoparticles and metallic indium (In) with {101} facets, following the specific crystallographic relationship of [010]In//[110]ITO; (001)In//(001)ITO with habit planes (100)In//(011)ITO, when fabricated using a low oxygen flow rate. Oxygen flow rate in excess of 2.0 sccm results in the growth of amorphous films. The epitaxial In nanoparticles probably act as seeds for the development of curved ITO whiskers as small as 10 nm and extend up to 100 nm in length along the [100] direction, with poorly defined shape, possibly due to the tapering and bending of the whisker to form a tilt boundary about the [011] zone axis of the ITO. The ITO whisker growth was facilitated by the In globular tips in the vapor–liquid–solid growth mechanism. The films prepared using a series of oxygen flow rates showed different chemical-bonding states, electric resistivity and optical transparency; as a result of phase and microstructural changes.
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68.55.ag Semiconductors
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
73.61.Jc Amorphous semiconductors; glasses
78.66.Jg Amorphous semiconductors; glasses
81.05.Gc Amorphous semiconductors
81.15.Cd Deposition by sputtering
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Tin dioxide as an alternative window layer for improving the damp-heat stability of copper indium gallium diselenide solar cells

B. Selin Tosun, Rebekah K. Feist, Stephen A. Campbell, and Eray S. Aydil

J. Vac. Sci. Technol. A 30, 04D101 (2012); http://dx.doi.org/10.1116/1.3692225 (5 pages)

Online Publication Date: 7 March 2012

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The authors demonstrate a new copper indium gallium diselenide solar cell architecture by replacing the ZnO in the traditional design with SnO2. The open circuit voltages and efficiencies of the solar cells made with ZnO and SnO2 were the same indicating favorable band alignment. The solar cells made with SnO2 showed significantly better damp-heat stability than those made with ZnO. The efficiency of solar cells made with SnO2 decreased less than 5% after 120 h at 85 °C and 85% relative humidity while the efficiency of solar cells made with ZnO declined by more than 70%.
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88.40.H- Solar cells (photovoltaics)

Magnetron-sputter deposition of Fe3S4 thin films and their conversion into pyrite (FeS2) by thermal sulfurization for photovoltaic applications

Hongfei Liu and Dongzhi Chi

J. Vac. Sci. Technol. A 30, 04D102 (2012); http://dx.doi.org/10.1116/1.3699022 (5 pages)

Online Publication Date: 2 April 2012

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The authors report on the fabrication of FeS2 (pyrite) thin films by sulfurizing Fe3S4 that were deposited by direct current magnetron sputtering at room temperature. Under the selected sputtering conditions, Fe3S4 nanocrystal films are obtained and the nanocrystals tend to locally cluster and closely pack into ricelike nanoparticles with an increase in film thickness. Meanwhile, the film tends to crack when the film thickness is increased over ∼1.3 μm. The film cracking can be effectively suppressed by an introduction of a 3-nm Cu intermediate layer prior to Fe3S4 deposition. However, an introduction of a 3-nm Al intermediate layer tends to enhance the film cracking. By post-growth thermal sulfurization of the Fe3S4 thin films in a tube-furnace, FeS2 with high phase purity, as determined by using x ray diffraction, is obtained. Optical absorption spectroscopy was employed to characterize the resultant FeS2 thin films, which revealed two absorption edges at 0.9 and 1.2 eV, respectively. These two absorption edges are assigned to the direct bandgap (0.9 eV) and the indirect allowed transitions (1.2 eV) of FeS2, respectively.
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68.55.ag Semiconductors
78.40.Fy Semiconductors
78.66.Li Other semiconductors
81.07.Bc Nanocrystalline materials
81.15.Cd Deposition by sputtering
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Effect of inserting a thin buffer layer on the efficiency in n-ZnO/p-Cu2O heterojunction solar cells

Yuki Nishi, Toshihiro Miyata, and Tadatsugu Minami

J. Vac. Sci. Technol. A 30, 04D103 (2012); http://dx.doi.org/10.1116/1.3698596 (6 pages)

Online Publication Date: 18 April 2012

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Transparent conducting Al-doped ZnO (AZO)/nondoped ZnO/Cu2O heterojunction solar cells were fabricated by inserting a thin nondoped ZnO film as a buffer layer between an n+-AZO thin film and a p-Cu2O sheet prepared by thermally oxidizing a Cu sheet. The effect of inserting the buffer layer on the obtainable photovoltaic properties in n+-AZO/n-ZnO/p-Cu2O heterojunction solar cells was investigated to improve the conversion efficiency. An improvement of photovoltaic properties was obtained by optimizing the thickness as well as the deposition conditions in the nondoped ZnO thin-film buffer layer. The obtained improvement of photovoltaic properties may be attributable mainly to an increase of the barrier height formed in the np junction, resulting from the inserted buffer layer functioning as an n-type ZnO layer as well as an enhancement of carrier lifetimes near the interface between the nondoped ZnO thin-film buffer layer and the Cu2O. A high efficiency of 4.08% was obtained in an AZO/nondoped ZnO/Cu2O heterojunction solar cell fabricated using a buffer layer prepared at room temperature and an O2 gas pressure of 1.0 Pa with a thickness of 50 nm on a Cu2O sheet and measured under simulated AM1.5G solar.
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88.40.hj Efficiency and performance of solar cells
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
88.40.J- Types of solar cells

Solar cell with built-in charge: Experimental studies of diode model parameters

Kimberly A. Sablon, John W. Little, Andrei Sergeev, Nizami Vagidov, and Vladimir Mitin

J. Vac. Sci. Technol. A 30, 04D104 (2012); http://dx.doi.org/10.1116/1.3703607 (4 pages)

Online Publication Date: 19 April 2012

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Quantum dots acquire built-in charge due to selective n-doping of the interdot space. The quantum dots with built-in charge (Q-BIC) increase electron coupling to IR radiation and suppress photoelectron capture, which in turn decrease the recombination via quantum dots. To investigate effects of the built-in-dot charge on recombination processes and device performance, the light and dark I–V characteristics and their temperature dependences of Q-BIC solar cells are measured. Employing the diode model, the data are analyzed in terms of the ideality factor, shunt resistance, and reverse saturation current. The authors compare the n-doped Q-BIC solar cells with the GaAs p-i-n reference cell, undoped, and p-doped devices. The analysis provides a qualitative description of the effect of doping on carrier kinetics and transport. The authors show that n-doping substantially reduces the recombination via quantum dots.
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88.40.J- Types of solar cells
85.30.Kk Junction diodes

Electrochemical properties of sputter-deposited MoO3 films in lithium microbatteries

C. V. Ramana, V. V. Atuchin, H. Groult, and C. M. Julien

J. Vac. Sci. Technol. A 30, 04D105 (2012); http://dx.doi.org/10.1116/1.3701763 (5 pages)

Online Publication Date: 24 April 2012

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Molybdenum oxide (MoO3) films were prepared by magnetron sputtering using an Mo target. The films were sputtered in the reactive atmosphere of an argon–oxygen gas mixture under various substrate temperatures, Ts, and oxygen partial pressures, p(O2). The effects of the growth conditions on the microstructure were examined using reflection high-energy electron diffraction and x-ray photoelectron spectroscopy. The analyses indicate that stoichiometric and polycrystalline MoO3 films were obtained at Ts = 445 °C and p(O2) = 61%. The applicability of the sputtered MoO3 films for lithium microbattery application has been demonstrated. The discharge–charge profiles, the kinetics of lithium intercalation process in the film, and the cycling behavior have been investigated in detail to understand the effect of microstructure on the electrochemical performance.
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81.15.Cd Deposition by sputtering
82.45.Mp Thin layers, films, monolayers, membranes
82.47.Aa Lithium-ion batteries
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Chemical and structural study of electrically passivating Al2O3/Si interfaces prepared by atomic layer deposition

Volker Naumann, Martin Otto, Ralf B. Wehrspohn, and Christian Hagendorf

J. Vac. Sci. Technol. A 30, 04D106 (2012); http://dx.doi.org/10.1116/1.4704601 (6 pages) | Cited 1 time

Online Publication Date: 24 April 2012

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Aluminum oxide (Al2O3) layers, prepared by atomic layer deposition (ALD), provide excellent surface passivation properties on crystalline Si surfaces, which are of major importance for photovoltaic applications. Beyond the chemical passivation by reduction of the electronic surface state density, a supportive field effect passivation mechanism emerges at the Al2O3/Si interface. The atomic origin of the fixed negative charges that are responsible for the field effect is currently under discussion. In this contribution, thin layers of Al2O3 with thicknesses ranging from the submonolayer region to several nanometers have been grown on Si substrates by means of thermal ALD. The principle elements of the samples have been quantified by x-ray photoelectron spectroscopy as a function of the film thickness. Changes at the interface upon thermal annealing have been investigated in detail. After the first few ALD cycles an imperfect Al2O3 layer is found together with the formation of an ultrathin SiOx interlayer. Continued deposition leads to stoichiometric Al2O3 growth. Within the first ∼1 nm from the Si interface, additional O (“excess O”), surpassing the Al2O3 and SiO2 stoichiometry, is observed. The excess O does not completely react with the Si surface to SiO2 during thermal annealing. Therefore, interstitial O in near-interface Al2O3 is suggested to provide the fixed negatively charged states.
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81.65.Rv Passivation
61.66.Bi Elemental solids
61.66.Dk Alloys
68.55.-a Thin film structure and morphology
73.20.At Surface states, band structure, electron density of states
73.61.Le Other inorganic semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Investigating the effects of proton exchange membrane fuel cell conditions on carbon supported platinum electrocatalyst composition and performance

Anant Patel, Kateryna Artyushkova, Plamen Atanassov, Vesna Colbow, Monica Dutta, David Harvey, and Silvia Wessel

J. Vac. Sci. Technol. A 30, 04D107 (2012); http://dx.doi.org/10.1116/1.4707153 (7 pages)

Online Publication Date: 26 April 2012

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Changes that carbon-supported platinum electrocatalysts undergo in a proton exchange membrane fuel cell environment were simulated by ex situ heat treatment of catalyst powder samples at 150 °C and 100% relative humidity. In order to study modifications that are introduced to chemistry, morphology, and performance of electrocatalysts, XPS, HREELS and three-electrode rotating disk electrode experiments were performed. Before heat treatment, graphitic content varied by 20% among samples with different types of carbon supports, with distinct differences between bulk and surface compositions within each sample. Following the aging protocol, the bulk and surface chemistry of the samples were similar, with graphite content increasing or remaining constant and Pt-carbide decreasing for all samples. From the correlation of changes in chemical composition and losses in performance of the electrocatalysts, we conclude that relative distribution of Pt particles on graphitic and amorphous carbon is as important for electrocatalytic activity as the absolute amount of graphitic carbon present.
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88.30.pd Proton exchange membrane fuel cells (PEM)
82.47.Gh Proton exchange membrane (PEM) fuel cells

Amorphous and nanocrystalline silicon thin film photovoltaic technology on flexible substrates

Baojie Yan, Jeffrey Yang, and Subhendu Guha

J. Vac. Sci. Technol. A 30, 04D108 (2012); http://dx.doi.org/10.1116/1.4707154 (10 pages)

Online Publication Date: 26 April 2012

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This paper reviews our thin film silicon-based photovoltaic (PV) technology, including material and device studies as well as roll-to-roll manufacturing on a flexible substrate. Our current thin film silicon PV products are made with hydrogenated amorphous silicon (a-Si:H) and amorphous silicon germanium (a-SiGe:H) alloys. The advantages of a-Si:H-based technology are low cost, capability of large scale manufacturing, abundance of raw materials, and no environmental concerns. One disadvantage of a-Si:H PV technology is lower energy conversion efficiency than solar panels made of crystalline and polycrystalline silicon and compound crystal thin film semiconductors. Significant efforts have been made to improve efficiency. First, a-Si:H and a-SiGe:H material quality has been improved by optimizing deposition conditions, especially using high hydrogen dilution to deposit the amorphous materials close to the amorphous/nanocrystalline transition. Second, cell efficiency has been improved by engineering the device structure, such as bandgap profiling. In order to use the solar spectrum effectively, multijunction structures that incorporate a-SiGe:H in the middle and bottom cells have been used. The authors achieved record high solar cell efficiency with an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structure. Using the same structure, we fabricated solar laminates on flexible stainless steel coils with roll-to-roll production systems. Our current product has a stable aperture area efficiency of 8.2%. In recent years, hydrogenated nanocrystalline silicon (nc-Si:H) has emerged as a potential replacement for the a-SiGe:H bottom cell in multijunction structures. The authors have conducted a great deal of research and development of a-Si:H- and nc-Si:H-based multijunction PV technology. The authors have significantly improved the efficiency of a-Si:H and nc-Si:H multijunction solar cells and modules by optimizing the nc-Si:H material quality and device structure. The authors achieved an initial active-area (∼0.25 cm2) solar cell efficiency of 16.3% using an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure and an initial aperture-area module (∼400 cm2) efficiency of 12.0% and a stable aperture-area module (∼800 cm2) efficiency of 11.3% using an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure. The authors expect to launch a new a-Si:H/nc-Si:H/nc-Si:H triple-junction product in near future with much higher efficiency than the current product.
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88.40.jj Silicon solar cells
88.40.jp Multijunction solar cells
88.40.hj Efficiency and performance of solar cells

Photoresponse of PbS nanoparticles–quaterthiophene films prepared by gaseous deposition as probed by XPS

Michael W. Majeski, F. Douglas Pleticha, Igor L. Bolotin, Luke Hanley, Eda Yilmaz, and Sefik Suzer

J. Vac. Sci. Technol. A 30, 04D109 (2012); http://dx.doi.org/10.1116/1.4709386 (5 pages)

Online Publication Date: 1 May 2012

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Semiconducting lead sulfide (PbS) nanoparticles were cluster beam deposited into evaporated quaterthiophene (4T) organic films, which in some cases were additionally modified by simultaneous 50 eV acetylene ion bombardment. Surface chemistry of these nanocomposite films was first examined using standard x-ray photoelectron spectroscopy (XPS). XPS was also used to probe photoinduced shifts in peak binding energies upon illumination with a continuous wave green laser and the magnitudes of these peak shifts were interpreted as changes in relative photoconductivity. The four types of films examined all displayed photoconductivity: 4T only, 4T with acetylene ions, 4T with PbS nanoparticles, and 4T with both PbS nanoparticles and acetylene ions. Furthermore, the ion-modified films displayed higher photoconductivity, which was consistent with enhanced bonding within the 4T organic matrix and between 4T and PbS nanoparticles. PbS nanoparticles displayed higher photoconductivity than the 4T component, regardless of ion modification.
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73.50.Pz Photoconduction and photovoltaic effects
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.07.Bc Nanocrystalline materials
68.55.-a Thin film structure and morphology
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Charge transport and relaxation in hydrogenated barium titanate films and their potential for integrated supercapacitors

Fadhel El Kamel and Patrice Gonon

J. Vac. Sci. Technol. A 30, 04D110 (2012); http://dx.doi.org/10.1116/1.4714356 (6 pages)

Online Publication Date: 7 May 2012

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Hydrogenated barium titanate films show enhancement of the double-layer capacitance and therefore can be employed as electrolytes in the all-solid-state supercapacitors. This behavior was attributed to the accumulation of protons at the metal–electrolyte interface over a Debye length (capacitive double layer). Electrical measurements were carried out on hydrogenated layers (BaTiO3:H) and trilayer stack (BaTiO3/BaTiO3:H/BaTiO3) to study the active defects at the origin of the conduction mechanisms.
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73.61.Ng Insulators
84.32.Tt Capacitors

Correlations of Cu(In, Ga)Se2 imaging with device performance, defects, and microstructural properties

Steve Johnston, Thomas Unold, Ingrid Repins, Ana Kanevce, Katherine Zaunbrecher, Fei Yan, Jian V. Li, Patricia Dippo, Rajalakshmi Sundaramoorthy, Kim M. Jones, and Bobby To

J. Vac. Sci. Technol. A 30, 04D111 (2012); http://dx.doi.org/10.1116/1.4714358 (6 pages)

Online Publication Date: 10 May 2012

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Camera imaging techniques have been used for the characterization of Cu(In,Ga)Se2 (CIGS) solar cells. Photoluminescence (PL) imaging shows brightness variations after the deposition of the CIGS layer that persist through CdS deposition and subsequent processing steps to finish the devices. PL and electroluminescence imaging on finished cells show a correlation to the devices’ corresponding efficiency and open-circuit voltage (VOC), and dark defect-related spots correspond to bright spots on images from illuminated lock-in thermography (LIT) and forward-bias dark LIT. These image-detected defect areas are weak diodes and shunts. Imaging provides locations of defects detrimental to solar cell performance. Some of these defects are analyzed in more detail by scanning electron microscopy using cross-sectional views.
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88.40.J- Types of solar cells
88.40.hj Efficiency and performance of solar cells
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