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Quantum dot (QD) sensitized solar cells have been receiving significant attention because of their potential to replace the existing conventional solar cells as low cost and high efficiency alternatives. This widespread attention has generated a large number of published research papers in the field that were recently reviewed. The challenge in reviewing the literature is in transforming the collected technical information generated through independently conducted perturbation experiments into an alternative point of view. A unique approach based on inferential statistics is explained and applied to reviewed QD based solar cells data. Analyzing the data in this fashion has provided us new and previously unknown insight into the operation and functioning of solar cells as well as the relative quantitative importance of each variable involved in determining the properties of interest in solar cells. This methodology is very powerful and can be applied to gain insight through reviewing the published data in any field of science to set the direction for ongoing and future research. In addition, the response surface methodology is explained and used to predict the reachable optimum efficiency of 20% with a given set of materials combination given the current state of the art.

Electron energy-loss measurements on thin films of collodion at low temperatures (90 K) show that the characteristic electron dose D e for mass loss first increases and then decreases with increasing dose rate (current density). This behaviour is explained in terms of the limited diffusion rates at low specimen temperature and the heating effect of the electron beam, and can be approximately modelled using a simple computer program. For a small-diameter electron probe, the increase in D e can be several orders of magnitude, suggesting a substantial advantage of STEM (in comparison to fixed-beam TEM) for examining beam-sensitive specimens.

A simple process for improving texture and electrical mobility of polycrystalline films is described. The technique involves annealing the film in a controlled temperature gradient and produces chainlike structures of impurity-free grains; dopants and other defects are confined to grain boundaries. The diffusion of impurities, as well as self-diffusion of the host lattice, produces a combing effect and causes grain reorientation in the annealed films. The electrical sheet conductance increases with increasing temperature gradient but attains an optimum value, above which the conductance falls due to microcracking of the film.

Laboratory thermomechanical processing (TMP) experiments have been carried out to study the austenite transformation characteristics, precipitation behavior, and recrystallization of deformed ferrite for an interstitial-free (IF) steel in the temperature range just below Ar 3. For cooling rates in the range 0.1 °C s−1 to 130 °C s−1, austenite transforms to either polygonal ferrite (PF) or massive ferrite (MF). The transformation temperatures vary systematically with cooling rate and austenite condition. There is indirect evidence that the transformation rates for both PF and MF are decreased by the presence of substitutional solute atoms and precipitate particles. When unstable austenite is deformed at 850 °C, it transforms to an extremely fine strain-induced MF. Under conditions of high supersaturation of Ti, Nb, and S, (Ti,Nb) x S y precipitates form at 850 °C as coprecipitates on pre-existing (Ti,Nb)N particles and as discrete precipitates within PF grains. Pre-existing intragranular (Ti,Nb) x S y precipitates retard recrystallization and grain coarsening of PF deformed at 850 °C and result in a stable, recovered subgrain structure. The results are relevant to the design of TMP schedules for warm rolling of IF steels.

We have studied thin films of tin-doped indium oxide prepared by e-beam evaporation using a zone-confining arrangement and exhibiting different microstructures. Specimens prepared with 5.1 at% tin are polycrystalline in nature while those prepared with 6.6 at% tin exhibit a granular microstructure which consists of a mixture of amorphous and crystalline grains. The appearance of the amorphous phase is attributed to the segregation of impurities. Three peaks at energies of 6, 9 and 14 eV are observed on the extinction coefficient of these specimens. These peaks become much sharper for the specimen showing a mixed microstructure due to improved crystallinity and purity of crystalline grains in this specimen.

A method for extracting the free electron density and mobility as well as the thickness of a semiconducting film from the optical transmission data is presented. The method is tested for tin-doped indium oxide thin films prepared with different thicknesses and different dopant concentrations. Thickness values extracted from this method agree very closely with those measured by interferometric method. Also, different samples prepared with the same dopant concentration exhibit similar carrier density but differ from those prepared with different dopant concentrations.

In this paper images of tin-doped indium oxide thin films obtained in a scanning tunnelling microscope (STM) are compared with those obtained from conventional transmission electron microscopy (CTEM) and scanning transmission electron microscopy (STEM). Corrugations with amplitude twice as big as compared to the thickness of the sample are observed at the grain boundaries. This is interpreted to have arisen from higher density of free carriers at the grain boundaries due to segregation of dopant over these boundaries. On an average, the grains appear twice as big in STM as compared to CTEM and STEM. This is attributed to the inability of the STM to detect twinned and similar boundaries in the absence of a change in free carrier density at the boundary.

Issues surrounding data access, ownership, and control raise important issues for science policy. The new sociology of science has examined many features of scientific knowledge and practice, but has made only preliminary efforts to study data access. Building on ethnographic studies of scientific laboratories (and other constructivist work), this article suggests how the new sociology of science can study data access empirically. The article develops a perspective based on an analysis of the process of scientific production and the creation, packaging, and exchange of data streams. It also provides an example of how constructivist studies can contribute to policy analysis.

Indium oxide, tin oxide, and some other doped and undoped oxide semiconductors show an interesting and technologically important combination of properties. They have high luminous transparency, good electrical conductivity and high infrared reflectivity. Numerous techniques for depositing these materials have been developed and have undergone a number of changes during last two decades. An understanding of the basic physics of these materials has begun to dawn. Most of the literature on transparent conducting oxides consists of studying the dependence of the properties on the composition, preparation conditions, such as deposition rate, substrate temperature or post-deposition heat treatment. In this paper the authors have employed the transmission electron microscopy to study the microstructure of reactively evaporated, electron beam evaporated, ion-beam sputtered amorphous indium oxide and reactively evaporated amorphous tin oxide thin films. These films, which have received little attention in the past, can have enormous potential as transparent conductive coatings on heat-sensitive substrates and inexpensive solar cells.

We have studied reactively evaporated thin films of amorphous indium oxide by HREM and have attempted to observe the structural changes appearing during the course of crystallization as the films are irradiated with electron beam. Two kinds of process are observed for crystallization: (i) gradual ordering over the whole of the projected area leading to crystallization with no obvious nucleation event, and (ii) nucleation and growth process.

Tin-doped indium oxide films have been prepared by e-beam reactive evaporation using a zone-confining process. The lowest resistivity of 4.4 × 10 −7 Ω m is lower by a factor of about 4 than previously reported values. Despite such a low resistivity the optical transparency is high (above 70% for film-substrate composite) and the mobility is 0.0103 m2 V−1 s−1 which is comparable to the mobility observed for flux-grown single crystals of indium oxide.

The Microstructural Physics group at the Cavendish Laboratory is actively involved in a considerable number of research projects which cover a broad range of materials science. In this paper, we describe briefly several such projects, with particular emphasis given to the application of parallel-detection electron energy loss spectroscopy (PEELS) on a scanning transmission electron microscope (STEM) to the analysis of materials such as stainless steels, catalysts, and high temperature superconductors. In addition, we describe a number of related projects that are currently being carried out in the group, particularly those which utilise and develop novel STEM imaging and analytical techniques. © 1993 Wiley-Liss, Inc.

Thin films exhibiting high optical transmission, low emissivity for thermal radiations and good electrical conductivity have important applications, such as transparent electrodes for electrochemical studies, infrared reflectors, antistatic coatings, thin-film resistors, antireflection coatings, resistance-reducing top layers on various solar cells and for a variety of display devices and imaging tubes [1-5]. Tin-doped indium oxide (ITO) is the best and most extensively studied material of this type. The required quality of the film increases with increasing sophistication of application. Achievement of the lowest possible resistivity is of practical significance, as it provides some freedom over the choice of film thickness to achieve high optical transmission while still maintaining low sheet resistance. Efforts to improve the resistivity while maintaining high optical transparency have included: postdeposition heat treatment [6], doping at both cation and anion sites [7], and production of multilayered indium oxide-tin oxide films [8]. Two methods which could reduce the resistivity and have not yet been tried are: growth of single-crystal indium oxide films followed by epitaxial growth of a thin film of Sn203, so that the single-crystal epilayer of S n 2 0 3 provides free electrons which could then be mobile in the indium oxide layers; and doping of the top few layers of a single-crystal indium oxide film with tin. Both of these methods require very expensive equipment and impose limitations on the choice of the substrate. Hence, they are impractical for commercial production. In addition to the achievement of the lowest possible resistivities, the other main objectives of the present research were to achieve the highest possible electron mobility and to provide an answer to the long-debated [9-12] question of the dominant scattering mechanism in tin-doped indium oxide films. This letter reports a very simple method for preparing selectively doped thin films. The objective was to devise a simple cost-effective method to produce films containing "zones" of heavily doped material sandwiches between the "zones" or relatively high-purity material. The heavily doped "zones" would act as free electron generators and the high-purity "zones" would provide a path for the electrons. The result would be high electron mobility and charge carrier density, and hence lower electri

Materials scientists have struggled for a while to find a process which can be used to engineer individual grain boundaries separating two adjacent grains. Considerable effort has also been devoted to finding a technique that can control the orientation of individual grains. A temperature gradient applied during the chemical vapor deposition of thin copper films provides an effect such that chains of grains oriented in the same direction are produced at chosen positions in the film. As a result of an interaction between defect migration and crystal growth, interconnected grains, oriented in the 〈110〉 direction and separated by twin grain boundaries, form chains along contours of equal temperature. When the temperature gradient is small, low-angle tilt boundaries, low-energy coincidence-site boundaries, and twin boundaries are observed. For a sharp temperature gradient, all boundaries are coherent twin boundaries.

Nucleation of crystals within an amorphous phase can be induced using electron beam irradiation in an electron microscope. In contrast to generally believed two-step phase transformation involving nucleation and growth, we observe a three-step transformation: a two-step nucleation stage followed by the growth process. The two steps in the nucleation stage are: the formation of a basic crystalline skeleton followed by the diffusion of excess defects to the periphery of the crystalline skeleton.

We discuss here the theoretical calculations for resistivity as a function of carrier density based on the dominant ionized impurity scattering mechanism and compare the experimental data with the theoretical lower limit. Our experimental resistivity values are below the theoretical lower limit for a homogeneous distribution of donors.

To understand the electronic conduction mechanism in Sn-doped indium oxide thin films, it is important to study the effect of dopant atoms on the neighbouring indium oxide lattice. Ideally Sn is a substitutional dopant at random indium sites. The difference in valence (Sn4+ replaces In3+) requires that an extra electron is donated to the lattice and thus contributes to the free carrier density. But since Sn is an adjacent member of the same row in the periodic table, the difference in the ionic radius (In3+: 0.218 nm; Sn4+: 0.205 nm) will introduce a strain in the indium oxide lattice. Free carrier electron waves will no longer see a perfect periodic lattice and will be scattered, resulting in the reduction of free carrier mobility, which will lower the electrical conductivity (an undesirable effect in most applications).One of the main objectives of the present investigation is to understand the effects of the strain (produced by difference in the ionic radius) on the microstructure of the indium oxide lattice when the doping level is increased to give high carrier densities. Sn-doped indium oxide thin films were prepared with four different concentrations: 9, 10, 11 and 12 mol. % of SnO2 in the starting material. All the samples were prepared at an oxygen partial pressure of 0.067 Pa and a substrate temperature of 250°C using an Edwards 306 coating unit with an electron gun attachment for heating the crucible. These deposition conditions have been found to give optimum electrical properties in Sn-doped indium oxide films. A JEOL 2000EX transmission electron microscope was used to investigate the specimen microstructure.

The microstructure and electrical properties of tin‐doped indium oxide thin films crystallized under the action of a temperature gradient are compared with those of films prepared under uniform temperature. This zone‐confining process, coupled with slow deposition rates, causes preferential segregation of dopants from grains growing at lower temperatures toward grain boundaries located at higher temperature. Recrystallization within a chain or zone of grains on a line of equal temperature causes these grains to be oriented in the same direction. The boundaries separating grains are twin boundaries. Electronic mean free paths in the zone‐confined specimens are from two to four times the average size of the grains.

Thin films of indium oxide were prepared by evaporating indium in the presence of oxygen. The effects of varying the oxygen partial pressure on the optical, electrical and structural properties were investigated. Films evaporated under the optimum oxygen partial pressure of 0.133 Pa exhibited a resistivity of 4.8 × 10 -4 Ω cm and a transmittance of more than 80% at wavelengths of 600 nm and above, for a film thickness of 225 nm. All the films, in the range of partial pressure of oxygen used, were found to be n type. The films showed a b.c.c. structure with a0 = 1.0118 nm and a preferred orientation along the 〈400〉 axis.

Reproductive health in the workplace presents in microcosm all of the ethical dilemmas raised by occupational medicine and medicine generally, including confidentiality, workers' right to know, individual autonomy, paternalism, informed consent, cost-benefit analysis, and a host of other issues.

Recent court decisions have stressed the necessity for cost-benefit analysis in evaluating Occupational and Safety Health Administration (OSHA) standards, thus raising difficult ethical questions which this paper analyzes using classical approaches of deontology and teleology. Since both modes of analysis have deficiencies, the need for a synthesis using economic and noneconomic measures is suggested.

A study of the electrical resistivity and microstructure of thin copper films deposited by low-pressure chemical vapor deposition from copper (I) hexafluoroacetylacetonate vinyltrimethylsilane (Cupra Select) was undertaken. Evidence for the nucleation of solid copper in the gas phase at substrate temperatures of about 250 °C is presented. A process to predict the effects of gas-phase nucleation and growth on the electrical resistivity of the resulting film is discussed.