Film Processing Conditions Research Articles

Performance measurements of mammographic systems

Performance measurements of 30 mammographic installations were carried out in order to see the current level of image quality and breast doses.The half of the systems tested in this survey indicated automatic exposure control and beam collimation problems. Film processing and dark room conditions were not optimum for the majority of the installations. Image quality phantoms were exposed by the user and team of the survey at each visited center. Lower breast doses were obtained at equal image qualities for the radiographs of the team indicating the importance of adequate handling of some exposure parameters. Corrective actions were suggested to each installation and necessary guidance was advised for the implementation of routine quality control activities.

Percolated perpendicular medium of FePt‐MgO/MgO bilayer films for ultra‐high magnetic recording

AbstractPercolated perpendicular (FePt)100–x‐(MgO)x thin films with x = 0–10.07 vol.% were fabricated on glass substrate with MgO(200)underlayer. When the substrate temperature was 580 oC, a significant enhancement in coercivity was observed at 1.23 vol.% of MgO, which was due to the precipitation of MgO in FePt film causing the hindrance in domain wall motion. As the amount of MgO was increased above 1.23 vol.%, the percolated perpendicular structure began to transform into granular perpendicular structure. Meanwhile, the MgO was found to segregate along grain boundaries of FePt grains, leading to the reduction of FePt grain size. As a result the coercivity and ordering parameter became smaller. In this study the percolated perpendicular medium using FePt film with doping adequate amount of MgO has shown possibility to be an efficient method to increase recording density if the film processing conditions are optimized further. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of the processing conditions on charge transfer and transport properties in poly(2-methoxy-5-(2′-ethylhexyloxy)1-4-phenylenevinylene):C60 composites for photovoltaics

Polymer-based photovoltaic devices have been elaborated by blending the conjugated polymer, poly(2-methoxy-5-(2′-ethylhexyloxy)1-4-phenylenevinylene) (MEH-PPV) with the buckminsterfullerene, C60. The solvent used has a main influence on the optical and electrical properties of the photoactive layers. This could be attributed to different dispersion abilities of C60 in the polymer layers shown by Atomic Force Microscopy and Scanning Electron Microscopy. Its effect on the transfer and transport properties has been studied. Thin film processing conditions have been modified by the preparation of blends of solutions of the polymer in Tetrahydrofuran and fullerene in Ortho-dichlorobenzene. The resulting spin casted layers show improved morphologies implying better dispersion of the fullerenes and increased short circuit currents. A decrease in the fullerene critical concentration to form percolation paths has been demonstrated. The improvement of the photovoltaic properties of the MEH-PPV/C60 composites has been attributed to the nanosized fullerene domains formed upon phase separation. We used optical spectroscopy to study the charge transfer efficiency and electrical measurements to investigate charge transport properties in MEH-PPV:C60.

CVD of MgO Thin Films from Bis(methylcyclopentadienyl) Magnesium

AbstractThin films of MgO are grown by CVD, with a high growth rate, on Si(001) and quartz substrates in the temperature range 400–550 °C, using bis(methylcyclopentadienyl)magnesium [Mg(CH3‐C5H4)2] as the precursor. The films obtained are investigated by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and optical absorption, in order to investigate the interrelations between film properties and processing conditions. Cubic phase MgO (periclase) films, characterized by a low carbon contamination and a granular surface morphology, are obtained.

High-Throughput Screening and Optimization of Photoembossed Relief Structures

A methodology for the rapid design, screening, and optimization of coating systems with surface relief structures, using a combination of statistical experimental design, high-throughput experimentation, data mining, and graphical and mathematical optimization routines was developed. The methodology was applied to photopolymers used in photoembossing applications. A library of 72 films was prepared by dispensing a given amount of sample onto a chemically patterned substrate consisting of hydrophilic areas separated by fluorinated hydrophobic barriers. Film composition and film processing conditions were determined using statistical experimental design. The surface topology of the films was characterized by automated AFM. Subsequently, models explaining the dependence of surface topologies on sample composition and processing parameters were developed and used for screening a virtual 4000-membered in silico library of photopolymer lacquers. Simple graphical optimization or Pareto algorithms were subsequently used to find an ensemble of formulations, which were optimal with respect to a predefined set of properties, such as aspect ratio and shape of the relief structures.

Influence of the Nanoscale Morphology on the Photovoltaic Properties of Fullerene/MEH‐PPV Composites

AbstractThe relation between morphology and photoelectric properties of PPV derivatives/fullerene composites forming bulk heterojunction solar cells has been investigated. The solvent used to spin cast the photoactive layers has a main influence on the quenching of the MEH‐PPV fluorescence, which could be attributed to different dispersion abilities of C60 in the polymer layer shown by AFM microscopy. Formation of large fullerene aggregates is observed at fullerene concentrations of the order of 10% leading to phase separation for composite layers processed in THF, whereas more dispersed distributions of fullerenes are observed in an aromatic solvent like ODCB which accounts for a more efficient luminescence quenching with increasing filler concentrations. However the improvement of the dissociation of photogenerated charge pairs is counterbalanced by a less efficient charge transport in the composite shown by lower short circuit currents probably due to unfavorable polymer chain arrangement in ODCB. Thin film processing conditions have been modified by the preparation of blends of solutions of the polymer in THF and fullerene in ODCB. The resulting spin casted layers show improved morphologies implying better dispersion of the fullerenes and increased short circuit currents. The improvement of the photovoltaic properties of the MEH‐PPV/C60 composites has been attributed to the nanosized fullerene domains formed upon phase separation.

Cross-Linked Polyfluorene Polymer Precursors: Electrodeposition, PLED Device Characterization, and Two-Site Co-deposition with Poly(vinylcarbazole)

Electropolymerization of π-conjugated polymers is considered as an alternative method for depositing and patterning charge injection, transport, and luminescent layers in organic electronic devices. In this study, a series of novel poly(fluoren-9,9-diyl-alt-alkan-α,ω-diyl) polymers with increasing alkyl spacer lengths were synthesized and used as precursors for the deposition of conjugated polymers formed by the oxidative coupling of the fluorene units. The precursor polymers and their conjugated polymer network were characterized in solution and in film form, and their charge-transport characteristics were investigated by fabricating electroluminescent polymer light emitting diode (PLED) devices. Interesting charge carrier transport properties based on thickness and co-deposition with another precursor polymer gives the potential for optimized solid-state device performance and film processing conditions. Finally, a “two-pixel” prototype PLED was demonstrated using a sequential electrochemical co-deposit...

The influence of growth conditions on the microstructure and critical currents of TFA-MODYBa2Cu3O7 films

The influence of three processing parameters, temperature, gas flow rate and water pressure, on theYBa2Cu3O7 filmgrowth on LaAlO3 single-crystal substrates from trifluoroacetate precursors has been investigated and the optimal filmprocessing conditions to achieve high critical currents have been determined. We have found thatthe growth conditions maximizing the critical current density are those where the nucleation ofa-axis oriented grains is minimized, as determined byμ-Raman spectroscopy. Under these conditions the normal state resistivity is very near tothat of single crystals because a vanishingly small film porosity is achieved. Transmissionelectron microscopy analysis of films quenched from the growth temperature gives somehints for understanding the mechanism linking the film porosity with the concentration ofa-axis grains. A cross-linked influence of different processing parameters,such as temperature and water pressure, or water pressure and gasflow, has been demonstrated. The optimal growth temperatures are790–830 °C, but at these growth temperatures, the critical current density is still dependent on the gasflow rate and water pressure. The optimal processing ranges are a compromise between twodifferent competing phenomena influencing the quality of the films: inhomogeneous filmformation due to HF gas stagnancy at small nominal growth rates (low gas flow rate orwater pressure) and perturbed crystallinity at high gas flow rates or water pressures.

A quality assurance program in dental radiographic units in western Greece

This survey reports on successful efforts to establish a quality assurance (QA) program for 50 intraoral x-ray units in the public and private sectors in the region of Achaia, Greece. It was conducted in 2 phases, in 1996 and in 2003, including on-site inspections, QA tests, and standard questionnaires. The aim of the study was to assess equipment conditions, knowledge, and adoption of radiographic QA guidelines by general dentists and, more importantly, the impact of the recommendations and training provided. The tested parameters focused on radiation protection, equipment maintenance, film speed used, film processing conditions, and radiologic characteristics such as voltage, radiation leakage, type of collimation, source-to-skin distance, timer accuracy, and entrance dose. The data gathered in 1996 demonstrate minimal compliance with equipment function requirements and radiation safety measures. 1 The comparative evaluation of all the parameters gathered from the 2 surveys, indicated that in 2003 the vast majority of the dentists followed the recommendations given in 1996. Only 2 dentists persisted in neglecting the guidelines.

Microscopic Morphology of Thin Films of Phthalocyanine/Perylene Blends for Organic Solar Cell Devices

AbstractWe report on the microstructure of 2(3)-9(10)-16(17)-23(24)-tetra(2-decyltetradecyloxy)- phthalocyanine/peryleneoleylamine (PcH2/PTCDI) blends. Thin films, to be used as active layers in organic photovoltaic cells, were prepared by spin coating and spin casting of dilute toluene solutions on indium tin oxide (ITO) substrates. The morphology of the thin films has been studied using Tapping Mode (TM) atomic force microscopy (AFM), whereas Scanning Electron Microscopy (SEM) was used to reveal the various top electrode morphologies, inherent to the different film processing conditions.

Interface instabilities and electronic properties of ZrO2 on silicon (100)

The interface stability of Zr-based high-k dielectrics with an oxide buffer layer was explored with x-ray (hυ=1254eV) and ultraviolet (hυ=21.2eV) photoemission spectroscopy. Zirconium oxide films were grown and characterized in situ in a stepwise sequence to explore their chemical stability and electronic properties as a function of film thickness and processing conditions. The buffer layers serve to lower the interface state density and to address the high temperature instabilities of ZrO2 in direct contact with Si. This research addresses three issues: (1) the development of the band offsets and electronic structure during the low temperature (T<300°C) growth processes, (2) variations in the band structure as effected by process conditions and annealing (T<700°C), and (3) the interface stability of Zr oxide films at high temperatures (T>700°C). Annealing the as-grown films to 600°C results in an ∼2eV shift of the ZrO2-Si band alignment, giving a band offset that is, favorable to devices, in agreement with predictions and in agreement with other experiments. We propose that the as-grown films contain excess oxygen resulting in a charge transfer from the Si substrate to the internal (ZrO2-SiO2) interface and that annealing to 600°C is sufficient to drive off this oxygen. Further annealing to 900°C, in the presence of excess Si at the surface, results in decomposition of the oxide to form ZrSi2.

CVD of Nanophasic (Zn, Cd)S Thin Films: From Multi‐Layers to Solid Solutions

AbstractNanostructured ZnxCd1 – xS (0 ≤ x ≤ 1) thin films were synthesized by CVD on SiO2 substrates using M(O‐iPrXan)2 (M = Zn,Cd; O‐iPrXan = S2COCH(CH3)2) as precursor compounds. The method of preparation used consisted in the sequential deposition of single‐phase MS coatings (M = Zn,Cd) at 300 °C in a N2 flow, followed by ex‐situ annealing in an inert atmosphere at various temperatures in the range 400–700 °C. The obtained specimens were thoroughly characterized before and after thermal treatments, paying particular attention to their structure, composition, morphology, and optical properties. Annealing in N2 at 600 °C for 3 h resulted in the formation of a homogeneous ZnxCd1 – xS solid solution. Lower temperatures did not produce a uniform sample composition, while more severe annealing conditions induced CdS sublimation. Moreover, a compositional control of the ZnxCd1 – xS ternary phase could be achieved by varying the ZnS overlayer deposition time.Irrespective of the annealing conditions, all the obtained films were contaminant‐free and nanophasic (∅︁ ≈25 nm), and possessed a hexagonal crystal structure the lattice parameters of which decreased linearly with increasing zinc molar fraction. A parallel evolution of optical absorption spectra was also observed. In the present paper, the interrelations between film properties and processing conditions are investigated, focusing particularly on the (Zn,Cd)S evolution to ZnxCd1 – xS solid solutions.

Conduction mechanisms in MOS gate dielectric films

This paper reviews the conduction mechanisms in the gate dielectric films of MOSFETs for VLSI and ULSI technologies. They include Fowler–Nordheim tunneling, internal Schottky (or Pool–Frenkel) effect, two-step (or trap-assisted) tunneling, shallow-trap-assisted tunneling, and band-to-band tunneling. The current transport in the gate dielectric films is manly controlled by film material composition, film processing conditions, film thickness, trap energy level and trap density in the films. In general, for a given gate dielectric film, the current transport behaviors are normally governed by one or two conduction mechanisms.

Effects of radiation and charge trapping on the reliability of high-κ gate dielectrics

The radiation response and long term reliability of alternative gate dielectrics will play a critical role in determining the viability of these materials for use in future space applications. The total dose radiation responses of several near and long term alternative gate dielectrics to SiO2 are discussed. Radiation results are presented for nitrided oxides, which show no change in interface trap density with dose and oxide trapped charge densities comparable to ultra thin thermal oxides. For aluminum oxide and hafnium oxide gate dielectric stacks, the density of oxide trapped charge is shown to depend strongly on the film thickness and processing conditions. The alternative gate dielectrics discussed here are shown to have effective trapping efficiencies that are up to ∼15 to 20 times larger than thermal SiO2 of equivalent electrical thickness. A discussion of single event effects in devices and ICs is also provided. It is shown that some alternative gate dielectrics exhibit excellent tolerance to heavy ion induced gate dielectric breakdown. However, it is not yet known how irradiation with energetic particles will affect the long term reliability of MOS devices with high-κ gate dielectrics in a space environment.

Epitaxial La0.67(Sr,Ca)0.33MnO3 Films on Si for IR Bolometer Applications

ABSTRACTWe report on processing and properties of La0.67(Sr,Ca)0.33MnO3(LSCMO) films grown by pulsed laser deposition technique on Si(001) substrates buffered with Bi4Ti3O12/CeO2/YSZ heteroepitaxial layers. X-ray diffraction shows cube-on-cube growth of epitaxial Bi4Ti3O12/CeO2/YSZ/Si heterostructure whereas the LSCMO layer grows in the “diagonal-on-side” manner onto the Bi4Ti3O12 (BTO) template. High resolution TEM images demonstrate sharp interfaces between the buffer layers and LSCMO film as well as rare misfit dislocations on the CeO2/YSZ interface. LSCMO film processing conditions have been optimized to get maximum temperature coefficient of resistivity TCR = 4.4%K-1 and colossal magnetoresistance(CMR) ‘Delta;ρ/ρ ∼ 2.9%kOe-1 @ 294K. Almost ultimate CMR performance at room temperature has been achieved due to successive improvement of c-axisorientation of layers: full widths at half-maximum (FWHM) 0.65, 0.58, 0.65, 1.13 and 0.18 degrees in LSCMO/BTO/CeO2/YSZ/Si stack, respectively. Characterization of electrical noise in CMR film yields noise equivalent temperature difference (NETD) as low as 1.2 ‘mu;K/√Hz @ 30Hz and 294K.

Epitaxial Colossal Magnetoresistive/Ferroelectric Heterostructures on Si

We report on processing and properties of La0.67(Sr, Ca)0.33MnO3 (LSCMO) films grown by pulsed laser deposition technique on Si(001) substrates buffered with Bi4Ti3O12/CeO2/YSZ heteroepitaxial layers. X-ray diffraction shows cube-on-cube growth of epitaxial Bi4Ti3O12/CeO2/YSZ/Si heterostructure whereas the LSCMO layer grows in the “diagonal-on-side” manner onto the Bi4Ti3O12 (BTO) template. High resolution TEM images demonstrate sharp interfaces between the buffer layers and LSCMO film as well as rare misfit dislocations on the CeO2/YSZ interface. LSCMO film processing conditions have been optimized to get maximum temperature coefficient of resistivity TCR = 4.4% K− 1 and colossal magnetoresistance (CMR) Δ ρ/ρ ∼ 2.9% kOe−1 @ 294 K. Almost ultimate CMR performance at room temperature has been achieved due to successive improvement of c-axis orientation of layers: full widths at half-maximum (FWHM) = 0.65, 0.58, 0.65, 1.13 and 0.18 degrees in LSCMO/BTO/CeO2/YSZ/Si stack, respectively. Characterization of electrical noise in CMR film yields Noise Equivalent Temperature Difference (NETD) as low as 1.2 μ K/√surd Hz @ 30 Hz and 294 K.

The properties of praseodymium bis[octakis(octyloxy)phthalocyaninato] complex Langmuir–Blodgett films for NO 2 sensor

Langmuir–Blodgett (LB) films of general organic semiconductor materials may be used as gas sensors because the conductivity depends on the presence of some gas species. Praseodymium bis[phthalocyaninato] complex-based LB films are very sensitive to the change of nitrogen dioxide(NO 2) gas concentration. In the paper, a new kind of sandwich-like praseodymium bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] complex Pr[Pc ∗] 2 ( Pc ∗= Pc (OC 8H 17) 8) was used as film-forming material. It is found that a mixture of Pr[Pc ∗] 2 and octadecanol (OA) with 1:6 molar ratio formed an excellent material for the fabrication of gas-sensing LB film. The sensitive property of Pr[Pc ∗] 2 LB films to NO 2 gas was monitored by the change of resistance during gas exposure. The detecting range was from 0 to 100 ppm, and the response time of 11-layer Pr[Pc ∗] 2 LB film to 20 ppm NO 2 was 27 s at room temperature. Factors affecting gas-sensing properties of Pr[Pc ∗] 2 LB films to NO 2 gas such as temperature, number of film layers and processing conditions were also discussed in the paper.

Dependence of threshold thickness of crystallization and film morphology on film processing conditions in poly(vinylidene fluoride–trifluoroethylene) copolymer thin films

In spin-cast films of poly(vinylidene fluoride–trifluoroethylene) on metalized silicon substrate, there exists a threshold thickness of crystallization dth, below which the crystallinity drops precipitously. Due to the direct link between the crystallinity and functional properties in the polymer, there is a corresponding large change in the film ferroelectric properties, including the dielectric constant, the polarization level, and polarization switching speed, as the thickness is reduced to below dth. Detail microstructure studies show that this threshold thickness is controlled by the stable crystal lamellar size along the film thickness direction. By varying the film processing condition to reduce the crystal lamellar size in the thickness direction, dth can be reduced markedly. As a result, better ferroelectric responses were obtained in ultrathin films.

Influence of processing conditions of polymer film on dropwise condensation heat transfer

The effect of processing conditions of polymer film on dropwise condensation heat transfer of steam under atmospheric pressure is investigated to find an effective technique to prepare a viable polymer film sustaining long-term dropwise condensation pattern state. The polytetrafluoroethylene (PTFE) films were coated on the external surfaces of brass tubes, copper tube, stainless steel tube and carbon steel tube by means of the dynamic ion-beam mixed implantation technique, with a variety of surface processing conditions. The experimental results indicated that heat flux is increased by 0.3–4.6 times and condensation heat transfer coefficient by 1.6–28.6 times of film condensation values for the brass tubes treated with various conditions. The surface processing condition is crucial to the adhesion between polymer film and metal substrate, different substrate material requires different optimal processing condition, and leads to different condensation heat transfer characteristic.

Effect of polishing conditions on terminating optical connectors with spherical convex polished ends.

Increased demand for fiber-optic technology has created significant growth in the sales of interconnection devices such as fiber-optic connectors, cable assemblies, and adapters. To ensure good connector performance during actual use, several process parameters related to geometric and optical characteristics of the connector must be thoroughly understood during the manufacturing stage. The experimental design has been used here to see the influence of applied pressure and time on the fiber end geometry as well as optical performance. The mathematical model is also applied to explain the phenomena of the present fiber undercut-reflectance relation. By a proper choice of polishing film grit size and processing conditions, it is possible to obtain fiber connectors with less fiber undercut and better return loss. Influences of film grit size and rubber-pad thickness on the reflectance and the fiber undercut are also presented.