A large-stroke planar 2-DOF flexure-based positioning stage for vacuum environments

The growing demand from industry for high-precision systems introduces new challenges for positioning mechanisms. High accuracy and repeatability down\ud to the sub-micron scale are not uncommon. This is often combined with extreme environments, like high UV light sources, electron beams or vacuum. This\ud article focuses on the flexure mechanism for a largestroke planar XY-positioning system. Applications for such a flexure mechanism can be found in for example lithography, micromachining or microscopy

Co-crystal of suberic acid and 1,2-bis(4-pyridyl)ethane: A new case of packing polymorphism

The polymorphic behaviour of a co-crystal composed of neutral suberic acid and 1, 2-bis(4-pyridyl)ethane is reported. A multidisciplinary approach has been employed, using thermal analysis methods (differential scanning calorimetry and polarized light thermomicroscopy), spectroscopic methods (infrared spectroscopy) and X-ray single crystal and powder diffraction. Two new polymorphs, I and III; have been identified, and for one of them the crystal structure has been elucidated and compared to that of a known polymorph, form II, showing that the assembling of the molecules in chains via H-bonds is a common feature of both polymorphs. Polymorph II, obtained by crystallization from an aqueous or ethanol solution or by grinding, undergoes a solid-solid transition to polymorph I, which melts at 180.5 °C. Upon cooling from the melt, polymorph I is obtained, and a solid-solid transformation also occurs, to polymorph III''. Polymorph III was obtained serendipitously in an attempt to prepare a Nd(III) complex. The relative stability of the three polymorphic forms was established

Electrical characterization of single nanometer-wide Si fins in dense arrays

This paper demonstrates the development of a methodology using the micro four-point probe (μ4PP) technique to electrically characterize single nanometer-wide fins arranged in dense arrays. We show that through the concept of carefully controlling the electrical contact formation process, the electrical measurement can be confined to one individual fin although the used measurement electrodes physically contact more than one fin. We demonstrate that we can precisely measure the resistance of individual ca. 20 nm wide fins and that we can correlate the measured variations in fin resistance with variations in their nanometric width. Due to the demonstrated high precision of the technique, this opens the prospect for the use of μ4PP in electrical critical dimension metrology

Influence of cantilever surface modification on the quality factor of microresonators.

De begeleider en/of auteur heeft geen toestemming gegeven tot het openbaar maken van de scriptie. The supervisor and/or the author did not authorize public publication of the thesis.

Exact Constraint Design of a Two-Degree of Freedom Flexure-Based Mechanism

We present the exact constraint design of a two degrees of freedom cross-flexure-based stage that combines a large workspace to footprint ratio with high vibration mode frequencies. To maximize unwanted vibration mode frequencies the mechanism is an assembly of optimized parts. To ensure a deterministic behavior the assembled mechanism is made exactly constrained. We analyze the kinematics of the mechanism using three methods; Grüblers criterion, opening the kinematic loops, and with a multibody singular value decomposition method. Nine release-flexures are implemented to obtain an exact constraint design. Measurements of the actuation force and natural frequency show no bifurcation, and load stiffening is minimized, even though there are various errors causing nonlinearity. Misalignment of the exact constraint designs does not lead to large stress, it does however decrease the support stiffness significantly. We conclude that designing an assembled mechanism in an exactly constrained manner leads to predictable stiffnesses and modal frequencie

CCDC 1544884: Experimental Crystal Structure Determination

Related Article: Maria A. Susano, Pablo Martín-Ramos, Teresa M.R. Maria, Steven Folkersma, Laura C.J. Pereira, Manuela Ramos Silva|2017|J.Mol.Struct.|1147|76|doi:10.1016/j.molstruc.2017.06.043,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Electrical characterization of single nanometer-wide Si fins in dense arrays

This paper demonstrates the development of a methodology using the micro four-point probe (μ4PP) technique to electrically characterize single nanometer-wide fins arranged in dense arrays. We show that through the concept of carefully controlling the electrical contact formation process, the electrical measurement can be confined to one individual fin although the used measurement electrodes physically contact more than one fin. We demonstrate that we can precisely measure the resistance of individual ca. 20 nm wide fins and that we can correlate the measured variations in fin resistance with variations in their nanometric width. Due to the demonstrated high precision of the technique, this opens the prospect for the use of μ4PP in electrical critical dimension metrology.status: publishe