610 research outputs found
Additive Soft-Lithographic Patterning of Submicrometer- and Nanometer-Scale Large-Area Resists on Electronic Materials
No full textWe describe a novel soft-lithographic technique possessing broad utility for the fabrication of large area, nanoscale (100 nm) multilayer resist structures on electronic material substrates. This additive patterning method transfers ultrathin poly(dimethylsiloxane) (PDMS) decals to an underlying SiO2-capped organic planarazation layer. The PDMS patterns serve as a latent image through which high-quality multilayer resist structures can be developed using reactive ion-beam etching
Micron and submicron patterning of polydimethylsiloxane resists on electronic materials by decal transfer lithography and reactive ion-beam etching: Application to the fabrication of high-mobility, thin-film transistors
No full textWe describe a technique for fabricating micron and submicron-sized polydimethylsiloxane (PDMS) patterns on electronic material substrates using decal transfer lithography (DTL) in conjunction with reactive ion-beam etching (RIE). We validate the use of this unconventional polymeric system as a suitable resist material for fabricating Si-based microelectronic devices. In this process, an O-2/CF4 gas mixture was used to etch a supporting PDMS thin film that resides atop a closed-form decal polymer to reveal conventional resist structures. These structures provide an effective latent image that, in turn, provides for an extension of soft lithography as a form of multilayer lithography-one yielding submicron structures similar to those obtained from the conventional photochemical methods used to prepare such resists. This combined DTL/RIE patterning procedure was found to be compatible with commercially available planarization layers and provides a direct means for preparing high aspect ratio resist features. We illustrate the applicability of soft lithography as a means for fabricating electronic devices by using it to prepare model silicon-based thin-film transistors exploiting silicon-on-insulator wafer technology. (c) 2006 American Institute of Physics
Orientation and chemistry of alkoxides on copper(111)
No full textSurface analytical techniques have been used to study the interaction of straight-chain alcohols with a preoxidized single-crystal Cu(111) surface under ultra-high vacuum conditions. The adsorbed alcohols deprotonate to form stable alkoxides chemisorbed to the surface. These alkoxides decompose at elevated temperatures by -hydride elimination, desorbing as aldehydes. The influence of deuterium isotope labelling, selective fluorination, and chain length on this mechanism has been studied. Temperature Programmed Reaction (TPR) spectra for the reactions of ethoxides and 1-propoxides and their selectively deuterated counterparts reveal both primary kinetic isotope effects and measurable secondary isotope effects.Fourier Transform Infrared Reflection Absorption Spectra (FT-IRAS) have been obtained for ethoxide, selectively fluorinated and deuterated ethoxides, 1-propoxide and selectively deuterated 1-propoxides, at saturation coverages on the Cu(111) surface. Quantitative measurements of the absorption intensities of the absorbed alkoxides and the randomly oriented corresponding alcohols allowed determination of the orientation of the adsorbed ethoxide and trifluoroethoxide. Ethoxide on the Cu(111) surface has the C-C bond tilted 70 2\sp\circ from the surface normal while in trifluoroethoxide the C-C bond is oriented 50 5\sp\circ from the surface normal. In both species the plane of the molecule defined by the C-C-O atoms is tilted towards the surface. This tilt between the plane of the molecule and the plane of the surface normal is 17 2\sp\circ for ethoxide and 20 11\sp\circ for trifluoroethoxide. The FT-IRAS spectra of the 1-propoxides have been compared to the reflection infrared spectra of self-assembled monolayers containing long alkyl chains. The spectra show evidence for both crystalline-like packing and conformational disorder in the adlayer, suggesting the presence of both ordered and disordered domains of the alkoxides on the Cu(111) surface. Finally, the FT-IRAS spectra of propene and a set of fluorinated propenes have been obtained. These physisorbed molecules are shown to lie with their molecular C-C=C planes parallel to the metal surface.Made available in DSpace on 2011-05-07T12:24:05Z (GMT). No. of bitstreams: 2
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Intraoperative liver ultrasound still affects surgical strategy for patients with colorectal metastases in the modern era
No full textIntraoperative liver ultrasound still affects surgical strategy for patients with colorectal metastases in the modern era.
Ferrero A1, Langella S, Giuliante F, Viganò L, Vellone M, Zimmitti G, Ardito F, Nuzzo G, Capussotti L.
Author information1Department of Surgery, Ospedale Mauriziano "Umberto I", Largo Turati 62, 10128, Turin, Italy, [email protected].
Abstract
BACKGROUND: The present study was designed to evaluate the role of intraoperative ultrasound (IOUS) in intrahepatic staging and the impact on surgical strategy for patients with colorectal liver metastases (CRLM).
METHODS: The study included 515 patients who had undergone liver resection for CRLM at two tertiary care referral centers. Data from a prospectively collected database were retrospectively analysed. Early intrahepatic recurrence was assessed at 3 and 6 months after resection and was considered as residual disease undetected by IOUS. Performance of imaging modalities was compared by analysis of studies on individual patients.
RESULTS: A total of 1,370 liver metastases were detected preoperatively with a median of 3 imaging modalities. MRI and PET were performed in 51 and 42 % of the patients, respectively. Median number of days between last imaging and surgery was 18. Contrast-enhanced IOUS was performed in 136 patients (26.4 %). Intraoperatively, 293 new nodules were found in 132 patients: on histology 280 were CRLM (17.6 %). Surgical strategy was changed in 140 patients (27.2 %). On multivariate analysis synchronous and bilobar metastases ≥ 3 in number, BMI ≥ 30, and time between last imaging and surgery longer than 18 days resulted in predictive factors indicating new nodules detected by IOUS. Early intrahepatic recurrences were 3.7 and 7.9 % at 3 and 6 months. Performance of CT, MRI, FDG-PET, and intraoperative staging was compared: sensitivity was 63.6, 68.8, 53.6, and 92 % and specificity was 91, 92.3, 95.8, and 97.8 %, respectively
CONCLUSIONS: The use of IOUS continues to be mandatory for correct staging of patients with CRLM undergoing liver resection
A Printable Form of Single‐Crystalline Gallium Nitride for Flexible Optoelectronic Systems
No full textThis work was supported by the DARPA-funded AFRL-managed
Macroelectronics Program and used the Center for Microanalysis
of Materials and the Laser and Spectroscopy Facility of the Frederick
Seitz Materials Research Laboratory, supported by the
Department of Energy (DEFG02-96ER45439). K.L. thanks Prof.
Jae Min Myoung in the Department of Materials Science and
Engineering at Yonsei University for valuable information related
to the processing of GaN thin films
Thermal and dynamic processes in deposition, growth, and etching of materials: I. Thermal and collision-induced activation of alkyl intermediates on aluminum. II. Chemical vapor deposition and growth of silicide on copper
No full textChemical vapor deposition (CVD) is becoming an increasingly important manufacturing process for the fabrication of VLSI and ULSI devices. A major challenge in optimizing a CVD process is developing an understanding of the complex mechanistic pathways followed. The first section in this thesis reports studies on the thermal and dynamical activation of surface bound alkyl species which play a vital role in the form of intermediates in metal-organic chemical vapor deposition. The particular systems of interest are those of aluminum CVD precursors. Models of these intermediates are obtained by thermal decomposition of alkyl iodides. The results provide an insight into the complex reaction patterns involved in the thermal reactions and rate-structure sensitivities of the alkyl species in the presence of the coadsorbed halogen atom. Multiple reaction pathways including metal etching processes which bear direct implications to the synthesis of organometallics and metal etching, are identified.It is becoming apparent that chemistry at surfaces, whether it be heterogeneous catalysis, semiconductor etching, or chemical vapor deposition, is controlled by much more than the nature and structure of the surface. Also, nonthermal activation of autocatalytic reactions is often required for the nucleation and growth of thin films in devices so that the stability of the device structure is maintained. Dynamical pathways followed in these high pressure and energy processes have to be well understood. The second part of these studies describe an investigation of collision-induced reaction of alkyl intermediates using supersonic inert gas atomic beams. Selective activation of a thermodynamically favored unimolecular decomposition reaction is initiated by hyperthermal collisions. Quantitative estimations of the reaction cross sections are made using straightforward hard sphere energy transfer dynamics. This successful demonstration of collision-induced activation of large, multiatomic moieties has paved the way for proposed studies (now underway in our group) on actual CVD precursors with known barriers to nucleation and growth.In the second section, the reaction mechanisms and kinetics of competitive dissociation, disproportionation, and thin film growth processes involved in the chemical vapor deposition of metal-silicide thin films are investigated. Metal-silicides are widely used as interconnect and gate materials in devices and also as corrosion resistant materials. Reactivity of silane and disilane with copper is studied in detail using temperature programmed reaction, Auger electron, Fourier transform infrared reflection absorption spectroscopies and low energy electron diffraction. For both the precursors, the structural chemistry and product distributions of adsorbed intermediates found at low temperatures are quite rich but significantly differ at the mechanistic level. It is shown quantitatively that disilane is almost 2-3 orders of magnitude more reactive than silane due to its facile Si-Si bond dissociation. However, in both cases, kinetics of silicon deposition and silicide formation are limited by the site-blocking effect of surface bound hydrogen generated by the decomposition of the silyl fragments. An ordered silicide overlayer is readily formed at higher coverages effected above dihydrogen desorption temperatures. This bimolecular process has to compete with an associative reaction which leads to the formation of silane. The results obtained from the different spectroscopic data show that the growth process involves an intriguing set of coupled reactions in which deposition, island growth, and Si etching effectively compete in a complex manner. Understanding of these parameters and the reaction mechanisms involved, enables the application of this process for the vapor phase growth of silicide thin films.Made available in DSpace on 2011-05-07T13:22:33Z (GMT). No. of bitstreams: 2
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Thermal and dynamic processes in deposition, growth, and etching of materials: I. Thermal and collision-induced activation of alkyl intermediates on aluminum. II. Chemical vapor deposition and growth of silicide on copper
No full textChemical vapor deposition (CVD) is becoming an increasingly important manufacturing process for the fabrication of VLSI and ULSI devices. A major challenge in optimizing a CVD process is developing an understanding of the complex mechanistic pathways followed. The first section in this thesis reports studies on the thermal and dynamical activation of surface bound alkyl species which play a vital role in the form of intermediates in metal-organic chemical vapor deposition. The particular systems of interest are those of aluminum CVD precursors. Models of these intermediates are obtained by thermal decomposition of alkyl iodides. The results provide an insight into the complex reaction patterns involved in the thermal reactions and rate-structure sensitivities of the alkyl species in the presence of the coadsorbed halogen atom. Multiple reaction pathways including metal etching processes which bear direct implications to the synthesis of organometallics and metal etching, are identified.It is becoming apparent that chemistry at surfaces, whether it be heterogeneous catalysis, semiconductor etching, or chemical vapor deposition, is controlled by much more than the nature and structure of the surface. Also, nonthermal activation of autocatalytic reactions is often required for the nucleation and growth of thin films in devices so that the stability of the device structure is maintained. Dynamical pathways followed in these high pressure and energy processes have to be well understood. The second part of these studies describe an investigation of collision-induced reaction of alkyl intermediates using supersonic inert gas atomic beams. Selective activation of a thermodynamically favored unimolecular decomposition reaction is initiated by hyperthermal collisions. Quantitative estimations of the reaction cross sections are made using straightforward hard sphere energy transfer dynamics. This successful demonstration of collision-induced activation of large, multiatomic moieties has paved the way for proposed studies (now underway in our group) on actual CVD precursors with known barriers to nucleation and growth.In the second section, the reaction mechanisms and kinetics of competitive dissociation, disproportionation, and thin film growth processes involved in the chemical vapor deposition of metal-silicide thin films are investigated. Metal-silicides are widely used as interconnect and gate materials in devices and also as corrosion resistant materials. Reactivity of silane and disilane with copper is studied in detail using temperature programmed reaction, Auger electron, Fourier transform infrared reflection absorption spectroscopies and low energy electron diffraction. For both the precursors, the structural chemistry and product distributions of adsorbed intermediates found at low temperatures are quite rich but significantly differ at the mechanistic level. It is shown quantitatively that disilane is almost 2-3 orders of magnitude more reactive than silane due to its facile Si-Si bond dissociation. However, in both cases, kinetics of silicon deposition and silicide formation are limited by the site-blocking effect of surface bound hydrogen generated by the decomposition of the silyl fragments. An ordered silicide overlayer is readily formed at higher coverages effected above dihydrogen desorption temperatures. This bimolecular process has to compete with an associative reaction which leads to the formation of silane. The results obtained from the different spectroscopic data show that the growth process involves an intriguing set of coupled reactions in which deposition, island growth, and Si etching effectively compete in a complex manner. Understanding of these parameters and the reaction mechanisms involved, enables the application of this process for the vapor phase growth of silicide thin films.U of I OnlyETDs are only available to UIUC Users without author permissio
Transfer printing by kinetic control of adhesion to an elastomeric stamp
No full textAn increasing number of technologies require large-scale integration of disparate classes of separately fabricated objects into spatially organized, functional systems(1-9). Here we introduce an approach for heterogeneous integration based on kinetically controlled switching between adhesion and release of solid objects to and from an elastomeric stamp. We describe the physics of soft adhesion that govern this process and demonstrate the method by printing objects with a wide range of sizes and shapes, made of single-crystal silicon and GaN, mica, highly ordered pyrolytic graphite, silica and pollen, onto a variety of substrates without specially designed surface chemistries or separate adhesive layers. Printed p-n junctions and photodiodes fixed directly on highly curved surfaces illustrate some unique device-level capabilities of this approach.The authors thank A. Shim for helpful discussions, A. Jerez for help generating schematic cartoons,
J. Rinne for supplying silica microspheres, J. Lyding for the use of his AFM, and C. J. Hubert for the use
of her African Violets. This work was supported by DARPA-funded AFRL-managed Macroelectronics
ProgramContract FA8650-04-C-7101, the US Department of Energy under grant
DEFG02-91-ER45439, the National Science Foundation under grant DMII-0328162, and a graduate
fellowship from the Fannie and John Hertz Foundation.
Correspondence and requests for materials should be addressed to J.A.R
High-speed mechanically flexible single-crystal silicon thin-film transistors on plastic substrates
No full textAbstract—This letter describes the fabrication and properties of bendable single-crystal-silicon thin film transistors formed on plastic substrates. These devices use ultrathin single-crystal silicon ribbons for the semiconductor, with optimized device layouts and low-temperature gate dielectrics. The level of performance that can be achieved approaches that of traditional silicon transis-tors on rigid bulk wafers: effective mobilities> 500 cm2/V · s, ON/OFF ratios> 105, and response frequencies> 500 MHz at channel lengths of 2 µm. This type of device might provide a promising route to flexible digital circuits for classes of ap-plications whose performance requirements cannot be satisfied with organic semiconductors, amorphous silicon, or other related approaches. Index Terms—Flexible circuits, printed transistors, silicon-on-insulator (SOI) wafer, thin film transistor (TFT). I
Kinetic and Mechanistic Studies of Chemical Vapor Deposition Processes on Metal Surfaces
No full textRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I OnlyMetal deposition from hexafluoroacetylacetonate complexes is also examined on Cu(111) and Pt(100) surfaces single crystal surfaces. In the case of the Rh(hfac)(C2H4)2 and Pt(hfac)2 on a copper surface, the transfer of the hfac ligands takes place below ∼220 K and this species subsequently either decomposes or reacts with the substrate to form Cu(hfac)2. This latter reaction is promoted by the presence of platinum on the copper surface but not by the presence of rhodium. In the reaction of Pt(hfac)2 on Pt(100), ligand dissociation begins ∼400 K and the resultant CFx surface fragments recombine to form a fluorocarbon species. This pathway is more strongly promoted in the presence of hydrogen as a reducing agent.Made available in DSpace on 2015-09-25T22:14:44Z (GMT). No. of bitstreams: 2
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Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs169 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2000
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