Durability of nanosized oxygen-barrier coatings on polymers

The National Ignition Facility (NIF) laser with its 192 independent laser beams is not only the world’s largest laser but also the largest optical system ever built. With its 192 independent laser ...

Large optics for the National Ignition Facility

Given the heterogeneous nature of cultures, tumors, and tissues, the ability to capture, contain, and analyze single cells is important for genomics, proteomics, diagnostics, therapeutics, and surgery. Moreover, for surgical applications in small conduits in the body such as in the cardiovascular system, there is a need for tiny tools that approach the size of the single red blood cells that traverse the blood vessels and capillaries. We describe the fabrication of arrayed or untethered single cell grippers composed of biocompatible and bioresorbable silicon monoxide and silicon dioxide. The energy required to actuate these grippers is derived from the release of residual stress in 3–27 nm thick films, did not require any wires, tethers, or batteries, and resulted in folding angles over 100° with folding radii as small as 765 nm. We developed and applied a finite element model to predict these folding angles. Finally, we demonstrated the capture of live mouse fibroblast cells in an array of grippers and i...

Self-Folding Single Cell Grippers

Generation and evolution of residual stresses in physical vapour-deposited thin films

Effective surface passivation of type-II InAs∕GaSb superlattice photodiodes with cutoff wavelengths in the long-wavelength infrared is presented. A stable passivation layer, the electrical properties of which do not change as a function of the ambient environment nor time, has been prepared by a solvent-based surface preparation, vacuum desorption, and the application of an insulating polyimide layer. Passivated photodiodes, with dimensions ranging from 400×400to25×25μm2, with a cutoff wavelength of ∼11μm, exhibited near bulk-limited R0A values of ∼12Ωcm2, surface resistivities in excess of 104Ωcm, and very uniform current-voltage behavior at 77K.

Near bulk-limited R0A of long-wavelength infrared type-II InAs/GaSb superlattice photodiodes with polyimide surface passivation

Silicon dioxide thin films have been prepared by electron‐gun evaporation under various deposition conditions. The residual stresses in SiO2 films were determined by measurements of the radius of curvature of Si and Ge substrates. The composition and density of films were deduced from Rutherford backscattering spectroscopy and elastic recoil detection analyses. The films were found to be stoichiometric (Si/O=1/2) under the deposition conditions investigated. The compressive residual stresses in films deposited at the base pressure (2×10−5 mbar) varied from −20 to −550 MPa as the substrate temperature increased from 20 to 285 °C. At a substrate temperature of 200 °C, the residual stresses varied from +70 to −180 MPa with decreasing oxygen pressure in the deposition chamber. The contribution of three types of stresses, namely thermal, intrinsic, and water‐induced stresses, can be distinguished. The stress component resulting from the absorption of water molecules in porous SiO2 films was obtained from varia...

Residual stresses in evaporated silicon dioxide thin films: Correlation with deposition parameters and aging behavior

Deposition of silicon dioxide thin films on silicon, germanium, and glass substrates has been accomplished by electron gun evaporation under various experimental conditions. The level of compressive residual stresses in evaporated SiO2 films determined just after deposition of films on Si or Ge substrates and the mass density of silica were found to be dependent on the substrate temperature and oxygen partial pressure in the evaporation chamber. Moreover, the intensity of compressive residual stresses decreased linearly as the logarithm of the exposure time of films to room air (aging time) was increased. After a compressive–tensile stress transition observed at a given aging time for films with relatively low densities, the intensity of tensile stresses continued to increase progressively with increasing aging time. The relative variation of residual stresses in SiO2 films was dependent on the mass density of the deposited material. Since the intensity of the absorption band of Si–OH radicals in the infrared spectra of SiO2 films exposed to room air increased with increasing aging time, the evolution of residual stresses was attributed to the effect of the hydration of silica by water vapor contained in room air. A reaction mechanism involving the physical adsorption of water vapor molecules on the SiO2 surface and reaction between adspecies and Si–O–Si species is proposed and discussed to interpret the logarithmic kinetics of residual stress evolution in evaporated SiO2 films exposed to room air.

J. Y. Robic

Papers

Residual stresses in evaporated silicon dioxide thin films: Correlation with deposition parameters and aging behavior

Kinetics of residual stress evolution in evaporated silicon dioxide films exposed to room air

Residual stress in silicon dioxide thin films produced by ion-assisted deposition