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Dive into the research topics where Benjamin Watts is active.

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Featured researches published by Benjamin Watts.


ACS Nano | 2012

Microstructure of Polycrystalline PBTTT Films: Domain Mapping and Structure Formation

Torben Schuettfort; Benjamin Watts; Lars Thomsen; Mijung Lee; Henning Sirringhaus; Christopher R. McNeill

We utilize near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and scanning transmission X-ray microscopy (STXM) to study the microstructure and domain structure of polycrystalline films of the semiconducting polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). Total electron yield NEXAFS spectroscopy is used to examine the surface structure of the first 1-2 molecular layers, while bulk-sensitive STXM is used to produce maps of domain orientation and order sampled through the entire film thickness. We study different phases of PBTTT including as-cast, terraced and nanoribbon morphologies produced via spin-coating as well as aligned films of as-cast and nanoribbon morphologies produced by zone-casting. For the terraced morphology, domains are observed that are larger than the size of the terraced surface features, and the calculated degree of order is reduced compared to the nanoribbon morphology. For zone-cast films, we find that, although little optical anisotropy is observed in the bulk of as-cast films, a high degree of surface structural anisotropy is observed with NEXAFS spectroscopy, similar to what is observed in annealed nanoribbon films. This observation indicates that the aligned surface structure in unannealed zone-cast films templates the bulk ordering of the aligned nanoribbon phase. STXM domain mapping of aligned nanoribbon films reveals elongated, micrometer-wide domains with each domain misoriented with respect to its neighbor by up to 45°, but with broad domain boundaries. Within each nanoribbon domain, a high degree of X-ray dichroism is observed, indicating correlated ordering throughout the bulk of the film.


Journal of Chemical Physics | 2011

Calibrated NEXAFS spectra of common conjugated polymers

Benjamin Watts; Sufal Swaraj; Dennis Nordlund; J. Lüning; Harald Ade

Near edge x-ray absorption fine structure (NEXAFS) spectroscopy has evolved into a powerful characterization tool for polymeric materials and is increasingly being used to elucidate composition and orientation in thin films of relevance to organic electronic devices. For accurate quantitative compositional analysis, insight into the electronic structure and the ability to assess molecular orientation, reliable reference spectra with known energy resolution and calibrated energy scale are required. We report a set of such NEXAFS spectra from 23 semiconducting polymers and some related materials that are frequently used in organic device research.


Advanced Materials | 2011

Sub-Micrometer Charge Modulation Microscopy of a High Mobility Polymeric n-Channel Field-Effect Transistor

Calogero Sciascia; Nicola Martino; Torben Schuettfort; Benjamin Watts; Giulia Grancini; Maria Rosa Antognazza; M. Zavelani-Rossi; Christopher R. McNeill; Mario Caironi

After two decades of fundamental research and steady development, solution processable organic fi eld-effect transistors (OFETs) have recently reached a mature stage that preludes their adoption in a variety of commercial applications from light-weight, stretchable, large-area sensors to low-cost, fl exible electronic circuits. [ 1–5 ] Despite the fact that fi eld-effect mobilities ( μ fe ) exceeding 1 cm 2 V − 1 s − 1 for both pand n-channel OFETs are now achievable with commercial, off-the-shelf conjugated organic small molecules and polymers, [ 4 ] fundamental studies are still strongly needed because of an incomplete understanding of the main mechanisms governing charge injection and transport in such devices. [ 7–9 ] To this extent, probing techniques capable of providing local information regarding mobility, fi eld, and charge distribution along the channel of a working device would be greatly benefi cial. Of particular interest for organic semiconductors is the relationship between microstructure and charge transport properties. This is even more evident in the case of recently developed high-mobility and stable n-channel OFETs, [ 6 ] in which the unusual face-on orientation of molecules has confounded expectations of what is required for effective charge transport. Scanning Kelvin-probe miscroscopy (SKPM) [ 7 ] is a powerful technique that allowed to map the potential profi le along the channels of OFETs with resolution better than 50 nm. [ 8 , 9 ]


Journal of Vacuum Science and Technology | 2007

Resonant soft x-ray reflectivity of organic thin films

Cheng Wang; Tohru Araki; Benjamin Watts; Shane E. Harton; Tadanori Koga; Saibal Basu; Harald Ade

At photon energies close to absorption edges in the soft x-ray range, the complex index of refraction, n=1−δ−iβ, of organic materials varies rapidly as a function of photon energy in a manner that strongly depends on the chemical moieties and functionalities present in the material. The authors present details of how these molecular structure specific variations in the complex index of refraction can be utilized to enhance and tune the contrast in reflectivity experiments of organic films. This near edge contrast enhancement mimics the specific contrast achieved through deuterium labeling in neutron reflectivity (NR). This relatively new x-ray approach, resonant soft x-ray reflectivity (RSoXR), thus combines aspects of NR and conventional x-ray reflectivity (XR), yet does not require special chemical procedures. The capabilities of RSoXR are exemplified using a number of polymeric bi- and multilayers. Furthermore, a direct comparison of RSoXR to conventional x-ray reflectivity and NR for polystyrene and p...


Small | 2010

Structure of Phase-Separated Ferroelectric/Semiconducting Polymer Blends for Organic Non-volatile Memories

Christopher R. McNeill; Kamal Asadi; Benjamin Watts; Paul W. M. Blom; Dago M. de Leeuw

The phase-separated structure of blends of the ferroelectric polymer P(VDF-TrFE) and the semiconducting polymer P3HT used in organic non-volatile memories is revealed with soft X-ray spectromicroscopy. These thin-film blends show a columnar morphology, with P3HT-rich columns enclosed in a continuous, essentially pure P(VDF-TrFE) phase favorable for data storage operation.


Biomicrofluidics | 2011

Sealing SU-8 microfluidic channels using PDMS

Zhiyi Zhang; Ping Zhao; Gaozhi Xiao; Benjamin Watts; Chang-Qing Xu

A simple method of irreversibly sealing SU-8 microfluidic channels using PDMS is reported in this paper. The method is based on inducing a chemical reaction between PDMS and SU-8 by first generating amino groups on PDMS surface using N(2) plasma treatment, then allowing the amino groups to react with the residual epoxy groups on SU-8 surface at an elevated temperature. The N(2) plasma treatment of PDMS can be conducted using an ordinary plasma chamber and high purity N(2), while the residual epoxy groups on SU-8 surface can be preserved by post-exposure baking SU-8 at a temperature no higher than 95 °C. The resultant chemical bonding between PDMS and SU-8 using the method create an interface that can withstand a stress that is greater than the bulk strength of PDMS. The bond is permanent and is long-term resistant to water. The method was applied in fabricating SU-8 microfluidi-photonic integrated devices, and the obtained devices were tested to show desirable performance.


Macromolecular Rapid Communications | 2010

Simultaneous Surface and Bulk Imaging of Polymer Blends with X-ray Spectromicroscopy

Benjamin Watts; Christopher R. McNeill

We demonstrate the utility of soft X-ray spectromicroscopy to simultaneously image the surface and bulk composition of polymer blend thin films. In addition to conventional scanning transmission X-ray microscopy that employs a scintillator and photomultiplier tube to measure the transmitted X-ray flux, channeltron detection of near-surface photoelectrons is employed to provide information of the composition of the first few nanometers of the film. Laterally phase-separated blends of two polyfluorene co-polymers are studied, with the structure of both wetting and capping layers clearly imaged. This new information provides insight into the connectivity of bulk and surface structures that is of particular relevance to the operation of such blends in optoelectronic devices.


Small | 2012

Studying polymer/fullerene intermixing and miscibility in laterally patterned films with X-ray spectromicroscopy.

Xiaoxi He; Brian A. Collins; Benjamin Watts; Harald Ade; Christopher R. McNeill

Films of the fullerene derivatives [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(61) BM) and [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71) BM) are patterned on silicon nitride membranes using photolithography to study, with X-ray spectromicroscopy, the lateral, solid-state diffusion of fullerene derivatives into conjugated polymer films. After patterning of the fullerene film, a film of conjugated polymer is laminated on top and the structure is annealed in order to study lateral intermixing and facilitate measurement of fullerene miscibility. Lateral intermixing of polymer and fullerene readily occurs for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) and regiorandom poly(3-hexylthiophene) (RRa-P3HT). A 42 wt.% miscibility of PC(61) BM in PBTTT is measured, while miscibilities of 20 and 41 wt.% are measured for PC(61) BM and PC(71) BM, respectively, in RRa-P3HT, thereby demonstrating a significant difference in the miscibilities of these two fullerene derivatives. For regioregular poly(3-hexylthiophene) (RR-P3HT), incomplete lateral intermixing of fullerene and RR-P3HT is observed with PCBM crystallite formation competing with the lateral diffusion of PCBM molecules into the polymer film.


Journal of Applied Crystallography | 2015

The NeXus data format

Mark Könnecke; Frederick Akeroyd; Herbert J. Bernstein; Aaron S. Brewster; Stuart I. Campbell; B. Clausen; S.P. Cottrell; Jens Uwe Hoffmann; Pete R. Jemian; David Mannicke; Raymond Osborn; Peter F. Peterson; Tobias Richter; Jiro Suzuki; Benjamin Watts; E. Wintersberger; Joachim Wuttke

A description is presented of the NeXus data format for X-ray and neutron scattering and muon spectroscopy.


IOP Conference Series: Materials Science and Engineering | 2010

Resonant Soft X-ray Scattering of Polymers with a 2D Detector: Initial Results and System Developments at the Advanced Light Source

Cheng Wang; Alexander Hexemer; J Nasiatka; E R Chan; Anthony Young; Howard A. Padmore; W F Schlotter; J Lüning; Sufal Swaraj; Benjamin Watts; Eliot Gann; Hongping Yan; Harald Ade

Most advanced applications of polymers rely on heterogeneous structures or specific interfacial properties to yield desired performance and functionalities. Rational design and application require that these structures be characterized. Recently, it has been demonstrated that soft x-ray scattering is a unique complementary technique to conventional hard x-ray and neutron scattering and an excellent tool for polymer structure determination with improved chemical sensitivity. Efforts to enhance the capabilities and efficiency of soft x-ray scattering through the use of a CCD detector will be delineated and first results presented. Development of a dedicated setup at beamline 11.0.1.2 of the Advanced Light Source will be described. This set-up has an elliptically polarized undulator as a source, which offers complete polarization control and hence unique capabilities.

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Harald Ade

North Carolina State University

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Zhiyi Zhang

National Research Council

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Cheng Wang

Lawrence Berkeley National Laboratory

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