Jump to Content
View Cart
Top 20 Most Read Articles
April 2012
The 20 articles with the most full-text downloads during the month, in descending order.
 |
Compositional study of vacuum annealed Al doped ZnO thin films obtained by RF magnetron sputtering J. Vac. Sci. Technol. A 29, 051514 (2011); http://dx.doi.org/10.1116/1.3624787 (9 pages) Online Publication Date: 18 August 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Aluminum doped zinc oxide (AZO) thin films were obtained by RF magnetron sputtering. The effects of deposition parameters such as power, gas flow conditions, and substrate heating have been studied. Deposited and annealed films were characterized for composition as well as microstructure using x ray photoelectron spectroscopy and x ray diffraction. Films produced were polycrystalline in nature. Surface imaging and roughness studies were carried out using SEM and AFM, respectively. Columnar grain growth was predominantly observed. Optical and electrical properties were evaluated for transparent conducting oxide applications. Processing conditions were optimized to obtain highly transparent AZO films with a low resistivity value of 6.67 × 10−4 Ω cm.
|
|||
|
Show PACS
|
|||
|
|
Photovoltaic manufacturing: Present status, future prospects, and research needs J. Vac. Sci. Technol. A 29, 030801 (2011); http://dx.doi.org/10.1116/1.3569757 (16 pages) Online Publication Date: 29 March 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
In May 2010 the United States National Science Foundation sponsored a two-day workshop to review the state-of-the-art and research challenges in photovoltaic (PV) manufacturing. This article summarizes the major conclusions and outcomes from this workshop, which was focused on identifying the science that needs to be done to help accelerate PV manufacturing. A significant portion of the article focuses on assessing the current status of and future opportunities in the major PV manufacturing technologies. These are solar cells based on crystalline silicon (c-Si), thin films of cadmium telluride (CdTe), thin films of copper indium gallium diselenide, and thin films of hydrogenated amorphous and nanocrystalline silicon. Current trends indicate that the cost per watt of c-Si and CdTe solar cells are being reduced to levels beyond the constraints commonly associated with these technologies. With a focus on TW/yr production capacity, the issue of material availability is discussed along with the emerging technologies of dye-sensitized solar cells and organic photovoltaics that are potentially less constrained by elemental abundance. Lastly, recommendations are made for research investment, with an emphasis on those areas that are expected to have cross-cutting impact.
|
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 30, 010802 (2012); http://dx.doi.org/10.1116/1.3670745 (11 pages) Online Publication Date: 14 December 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Atomic layer deposition (ALD) is a technique capable of producing ultrathin conformal films with atomic level control over thickness. A major drawback of ALD is its low deposition rate, making ALD less attractive for applications that require high throughput processing. An approach to overcome this drawback is spatial ALD, i.e., an ALD mode where the half-reactions are separated spatially instead of through the use of purge steps. This allows for high deposition rate and high throughput ALD without compromising the typical ALD assets. This paper gives a perspective of past and current developments in spatial ALD. The technology is discussed and the main players are identified. Furthermore, this overview highlights current as well as new applications for spatial ALD, with a focus on photovoltaics and flexible electronics.
|
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 30, 020801 (2012); http://dx.doi.org/10.1116/1.3676433 (19 pages) Online Publication Date: 15 February 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Dye sensitized solar cells (DSSCs) have received a tremendous amount of attention since the first report of a 7% efficient cell in 1991. Confirmed record efficiencies are now 11.2% for small cells and 9.9% for submodules, and low-cost production methods are enabling manufacturing of DSSC products for a variety of markets. This review describes the present status of DSSC devices and manufacturing as well as research challenges that must be addressed to continue the rapid commercialization of DSSC technology. These challenges fall into the categories of improving efficiency, stability, and manufacturability. Efficiency improvements will hinge on the development of new combinations of dyes, redox couples, and photoanodes. Best-case lifetimes are determined by the kinetics of various molecular-level processes, and realization of these lifetimes will require improved encapsulation of cells and modules. Low-cost and sustainable manufacturing of DSSC modules depends on use of high-throughput roll-to-roll processing and inexpensive, abundant materials. Prospects for simultaneous improvement of efficiency, stability, and manufacturing are discussed.
|
|||
|
Show PACS
|
|||
|
|
Plasma-Assisted Atomic Layer Deposition: Basics, Opportunities, and Challenges J. Vac. Sci. Technol. A 29, 050801 (2011); http://dx.doi.org/10.1116/1.3609974 (26 pages) Online Publication Date: 18 August 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Plasma-assisted atomic layer deposition (ALD) is an energy-enhanced method for the synthesis of ultra-thin films with Å-level resolution in which a plasma is employed during one step of the cyclic deposition process. The use of plasma species as reactants allows for more freedom in processing conditions and for a wider range of material properties compared with the conventional thermally-driven ALD method. Due to the continuous miniaturization in the microelectronics industry and the increasing relevance of ultra-thin films in many other applications, the deposition method has rapidly gained popularity in recent years, as is apparent from the increased number of articles published on the topic and plasma-assisted ALD reactors installed. To address the main differences between plasma-assisted ALD and thermal ALD, some basic aspects related to processing plasmas are presented in this review article. The plasma species and their role in the surface chemistry are addressed and different equipment configurations, including radical-enhanced ALD, direct plasma ALD, and remote plasma ALD, are described. The benefits and challenges provided by the use of a plasma step are presented and it is shown that the use of a plasma leads to a wider choice in material properties, substrate temperature, choice of precursors, and processing conditions, but that the processing can also be compromised by reduced film conformality and plasma damage. Finally, several reported emerging applications of plasma-assisted ALD are reviewed. It is expected that the merits offered by plasma-assisted ALD will further increase the interest of equipment manufacturers for developing industrial-scale deposition configurations such that the method will find its use in several manufacturing applications.
|
|||
|
Show PACS
|
|||
|
|
Microstructural evolution during film growth J. Vac. Sci. Technol. A 21, S117 (2003); http://dx.doi.org/10.1116/1.1601610 (12 pages) Online Publication Date: 2 September 2003
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Atomic-scale control and manipulation of the microstructure of polycrystalline thin films during kinetically limited low-temperature deposition, crucial for a broad range of industrial applications, has been a leading goal of materials science during the past decades. Here, we review the present understanding of film growth processes—nucleation, coalescence, competitive grain growth, and recrystallization—and their role in microstructural evolution as a function of deposition variables including temperature, the presence of reactive species, and the use of low-energy ion irradiation during growth. © 2003 American Vacuum Society. |
|||
|
Show PACS
|
|||
|
|
High power impulse magnetron sputtering discharge J. Vac. Sci. Technol. A 30, 030801 (2012); http://dx.doi.org/10.1116/1.3691832 (35 pages) Online Publication Date: 14 March 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency while keeping the average power about 2 orders of magnitude lower than the peak power. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth by controlling the energy and direction of the deposition species. This is a significant advantage over conventional dc magnetron sputtering where the sputtered vapor consists mainly of neutral species. The HiPIMS discharge is now an established ionized physical vapor deposition technique, which is easily scalable and has been successfully introduced into various industrial applications. The authors give an overview of the development of the HiPIMS discharge, and the underlying mechanisms that dictate the discharge properties. First, an introduction to the magnetron sputtering discharge and its various configurations and modifications is given. Then the development and properties of the high power pulsed power supply are discussed, followed by an overview of the measured plasma parameters in the HiPIMS discharge, the electron energy and density, the ion energy, ion flux and plasma composition, and a discussion on the deposition rate. Finally, some of the models that have been developed to gain understanding of the discharge processes are reviewed, including the phenomenological material pathway model, and the ionization region model.
|
|||
|
Show PACS
|
|||
|
|
Influence of ionization degree on film properties when using high power impulse magnetron sputtering J. Vac. Sci. Technol. A 30, 031507 (2012); http://dx.doi.org/10.1116/1.3700227 (5 pages) Online Publication Date: 3 April 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Chromium thin films are deposited by combining direct current magnetron sputtering and high power impulse magnetron sputtering (HiPIMS) on a single cathode in an industrial deposition system. While maintaining a constant deposition rate and unchanged metal ion energy distribution function, the fraction of the total power supplied by either deposition technique is altered, and thereby also the metal ion to metal neutral ratio of the deposition flux. It is observed that the required total average power needed to be proportionally increased as the HiPIMS fraction is increased to be able to keep a constant deposition rate. The influence on microstructure, electrical, and electrochemical properties of the films is investigated and shows improvements with the use of HiPIMS. However, considerable influence of the studied properties occurs already when only some 40% of the total power is supplied by the HiPIMS technique. Further increase of the HiPIMS power fraction results in comparatively minor influence of the studied properties yet significant deposition rate efficiency reduction. The results show that the degree of ionization can be controlled separately, and that the advantages associated with using HiPIMS can be obtained while much of the deposition rate reduction, often reported for HiPIMS, can be avoided.
|
|||
|
Show PACS
|
|||
|
|
Structural analysis of Si(111)‐7×7 by UHV‐transmission electron diffraction and microscopy J. Vac. Sci. Technol. A 3, 1502 (1985); http://dx.doi.org/10.1116/1.573160 (5 pages)
Full Text:
|
Download PDF
|
||
|
Show Abstract
Structural analysis of the surface reconstructions investigated by ultrahigh vacuum (UHV) transmission electron microscopy (TEM) and diffraction (TED) is shown. By TED intensity analysis a new structural model of Si(111)‐7×7 is derived. The model basically consists of 12 adatoms arranged locally in the 2×2 structure, nine dimers on the sides of the triangular subunits of the 7×7 unit cell and a stacking fault layer. UHV–HREM of Si (111)‐7×7 surface is commented. |
|||
|
Show PACS
|
|||
|
|
Metal–organic interface and charge injection in organic electronic devices J. Vac. Sci. Technol. A 21, 521 (2003); http://dx.doi.org/10.1116/1.1559919 (11 pages) Online Publication Date: 18 March 2003
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Charge injection at the interface between metallic electrodes and organic semiconductors plays a crucial role in the performance of organic (opto-)electronic devices. This article discusses the current understanding of the formation of the metal–organic contact and the parameters which control the injection current. Organic semiconductors differ significantly from their inorganic counterparts, primarily because they are amorphous van der Waals solids. As a result the electronic states are highly localized, and charge transport is by site-to-site hopping. Organics can also form clean interfaces with many metals, free of interface states in the gap. Nevertheless, there is generally found to be a significant vacuum level offset, the origins of which are not yet fully understood. Organic semiconductors are frequently free of donor and acceptor dopants, and as a result the depletion depth is larger than the organic layer thickness. Thus the Fermi level in the organic and the charge injection barriers depend most directly on the interface offset. The charge injection process is described as thermally assisted tunneling from the delocalized states of the metal into the localized states of the semiconductor, whose energy includes contributions from the mean barrier height, the image potential, the energetic disorder, and the applied electric field. There is no completely satisfactory analytic theory for the field and temperature dependence of the injection current, which, for well characterized interfaces, exhibits behavior relating to both thermionic emission and field-induced tunneling. © 2003 American Vacuum Society. |
|||
|
Show PACS
|
|||
|
|
The search for novel, superhard materials J. Vac. Sci. Technol. A 17, 2401 (1999); http://dx.doi.org/10.1116/1.581977 (20 pages)
Full Text:
|
Download PDF
|
|||||||||||||
|
Show Abstract
The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed. Two basic approaches are outlined including the intrinsic superhard materials, such as diamond, cubic boron nitride, C3N4, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure. The theoretically predicted high hardness of C3N4 has not been experimentally documented so far. Ceramics made of cubic boron nitride prepared at high pressure and temperature find many applications whereas thin films prepared by activated deposition from the gas phase are still in the stage of fundamental development. The greatest progress has been achieved in the field of nanostructured materials including superlattices and nanocomposites where superhardness of ⩾50 GPa was reported for several systems. More recently, nc-TiN/SiNx nanocomposites with hardness of 105 GPa were prepared, reaching the hardness of diamond. The principles of design for these materials are summarized and some unresolved questions outlined. © 1999 American Vacuum Society. |
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
J. Vac. Sci. Technol. A 30, 04D101 (2012); http://dx.doi.org/10.1116/1.3692225 (5 pages) Online Publication Date: 7 March 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
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%.
|
||||
|
Show PACS
|
||||
|
|
Atomic layer deposition for electrochemical energy generation and storage systems J. Vac. Sci. Technol. A 30, 010803 (2012); http://dx.doi.org/10.1116/1.3672027 (14 pages) Online Publication Date: 27 December 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Clean renewable energy sources (e.g., solar, wind, and hydro) offers the most promising solution to energy and environmental sustainability. On the other hand, owing to the spatial and temporal variations of renewable energy sources, and transportation and mobility needs, high density energy storage and efficient energy distribution to points of use is also critical. Moreover, it is challenging to scale up those processes in a cost-effective way. Electrochemical processes, including photoelectrochemical devices, batteries, fuel cells, super capacitors, and others, have shown promise for addressing many of the abovementioned challenges. Materials with designer properties, especially the interfacial properties, play critical role for the performance of those devices. Atomic layer deposition is capable of precise engineering material properties on atomic scale. In this review, we focus on the current state of knowledge of the applications, perspective and challenges of atomic layer deposition process on the electrochemical energy generation and storage devices and processes.
|
|||
|
Show PACS
|
|||
|
|
Imaging and phase identification of Cu2ZnSnS4 thin films using confocal Raman spectroscopy J. Vac. Sci. Technol. A 29, 051203 (2011); http://dx.doi.org/10.1116/1.3625249 (11 pages) Online Publication Date: 26 August 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Copper zinc tin sulfide (Cu2ZnSnS4 or CZTS) is a potential candidate for next generation thin film solar cells because it contains abundant and nontoxic elements and exhibits high light absorption. Thin films of CZTS are typically synthesized by sulfidizing a stack of zinc, copper, and tin films. In addition to CZTS, a variety of binary and ternary metal sulfides can form and distinguishing among phases with similar crystal structure can be difficult. Herein, the authors show that confocal Raman spectroscopy and imaging can distinguish between CZTS and the other binary and ternary sulfides. Specifically, Raman spectroscopy was used to detect and distinguish between CZTS (338 cm−1), Cu2SnS3 (298 cm−1), and Cu4SnS4 (318 cm−1) phases through their characteristic scattering peaks. Confocal Raman spectroscopy was then used to image the distribution of coexisting phases and is demonstrated to be a useful tool for examining the heterogeneity of CZTS films. The authors show that, during sulfidation of a zinc/copper/tin film stack, ternary sulfides of copper and tin, such as Cu2SnS3 form first and are then converted to CZTS. The reason for formation of Cu2SnS3 as an intermediary to CZTS is the strong tendency of copper and tin to form intermetallic alloys upon evaporation. These alloys sulfidize and form copper tin sulfides first, and then eventually convert to CZTS in the presence of zinc. As a consequence, films sulfidized for 8 h at 400 °C contain both CZTS and Cu2SnS3, whereas films sulfidized at 500 °C contain nearly phase-pure CZTS. In addition, using Cu Kα radiation, the authors identify three CZTS X-ray diffraction peaks at 37.1° [(202)], 38° [(211)], and 44.9° [(105) and (213)], which are absent in ZnS and very weak in Cu2SnS3.
|
|||
|
Show PACS
|
|||
|
|
Nanosphere lithography: A materials general fabrication process for periodic particle array surfaces J. Vac. Sci. Technol. A 13, 1553 (1995); http://dx.doi.org/10.1116/1.579726 (6 pages)
Full Text:
|
Download PDF
|
||
|
Show Abstract
In this article nanosphere lithography (NSL) is demonstrated to be a materials general fabrication process for the production of periodic particle array (PPA) surfaces having nanometer scale features. A variety of PPA surfaces have been prepared using identical single‐layer (SL) and double‐layer (DL) NSL masks made by self‐assembly of polymer nanospheres with diameter, D=264 nm, and varying both the substrate material S and the particle material M. In the examples shown here, S was an insulator, semiconductor, or metal and M was a metal, inorganic ionic insulator, or an organic π‐electron semiconductor. PPA structural characterization and determination of nanoparticle metrics was accomplished with atomic force microscopy. This is the first demonstration of nanometer scale PPA surfaces formed from molecular materials. © 1995 American Vacuum Society |
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 30, 04D102 (2012); http://dx.doi.org/10.1116/1.3699022 (5 pages) Online Publication Date: 2 April 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
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.
|
|||
|
Show PACS
|
|||
|
|
Thin-film electronics by atomic layer deposition J. Vac. Sci. Technol. A 30, 018501 (2012); http://dx.doi.org/10.1116/1.3670748 (9 pages) Online Publication Date: 14 December 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Atomic layer deposition (ALD) produces conformal films with low defects and a high degree of thickness control. Many applications leverage these properties to yield excellent dielectrics and barrier layers. In recent years, ALD has been exploited to produce thin-film transistors, in which the technique is capable of producing all of the layers required, including the semiconductor. This perspective will examine the state-of-the-art use of ALD to produce thin-film electronics, notably the zinc oxide-based thin-film transistor. It is critical that the ZnO-based semiconductor material have sufficiently high resistivity in order to yield transistors with low off current and good switching characteristics. The nature of this problem and the approaches used to address it will be discussed. The use of rapid deposition technologies, such as spatial ALD, also has a strong impact on the quality of the ZnO semiconductor. Finally, demonstrations of various thin film electronics devices and systems produced by ALD will be reviewed.
|
|||
|
Show PACS
|
|||
|
|
Atomic layer deposition for nanostructured Li-ion batteries J. Vac. Sci. Technol. A 30, 010801 (2012); http://dx.doi.org/10.1116/1.3660699 (10 pages) Online Publication Date: 21 November 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
Nanostructuring is targeted as a solution to achieve the improvements required for implementing Li-ion batteries in a wide range of applications. These applications range in size from electrical vehicles down to microsystems. Atomic layer deposition (ALD) could be an enabling technology for nanostructured Li-ion batteries as it is capable of depositing ultrathin films (1–100 nm) in complex structures with precise growth control. The potential of ALD is reviewed for three battery concepts that can be distinguished, i.e., particle-based electrodes, 3D-structured electrodes, and 3D all-solid-state microbatteries. It is discussed that a large range of materials can be deposited by ALD and recent demonstrations of battery improvements by ALD are used to exemplify its large potential.
|
||||
|
Show PACS
|
||||
|
|
Transparent conductive Al-doped ZnO thin films grown at room temperature J. Vac. Sci. Technol. A 29, 031505 (2011); http://dx.doi.org/10.1116/1.3565462 (6 pages) Online Publication Date: 16 March 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Aluminum-doped ZnO (ZnO:Al, AZO) thin films were prepared on glass substrates by dc reactive magnetron sputtering from a Zn–Al alloy target at room temperature. The effects of the Ar-to-O2 partial pressure ratios on the structural, electrical, and optical properties of AZO films were studied in detail. AZO films grown using 100:4 to 100:8 Ar-to-O2 ratio result in acceptable quality films with c-axis orientated crystals, uniform grains, 10−3 Ω cm resistivity, greater than 1020 cm−3 electron concentration, and high transmittance, 90%, in the visible region. The lowest resistivity of 4.11×10−3 Ω cm was obtained under the Ar-to-O2 partial pressure ratio of 100:4. A relatively strong UV emission at ∼ 3.26 eV was observed in the room-temperature photoluminescence spectrum. X-ray photoelectron spectroscopy analysis confirmed that Al was introduced into ZnO and substitutes for Zn and doped the film n-type.
|
|||
|
Show PACS
|
|||
|
|
Work function of fluorine doped tin oxide J. Vac. Sci. Technol. A 29, 011019 (2011); http://dx.doi.org/10.1116/1.3525641 (4 pages) Online Publication Date: 5 January 2011
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Fluorine doped tin oxide (FTO) is a commonly used transparent conducting oxide in optoelectronic device applications. The work function of FTO is commonly cited as 4.4 eV, which is incommensurate with recent device performance results. Using x-ray photoelectron spectroscopy, the authors measured the work function of commercial FTO to be 5.0±0.1 eV. UV ozone treatment was found to increase the work function by ∼ 0.1 eV due to surface band bending. The origins of the much lower work function previously reported are also discussed and are found to be a result of carbon contamination and UV induced work function lowering.
|
|||
|
Show PACS
|
|||
This Publication
Scitation
SPIN
Scitopia
Google Scholar
PubMed