No abstract

Anhydrous silylation of vinyltrimethoxysilane (VTMS) onto silica and zirconia substrates was investigated experimentally to demonstrate and quantify the effects of surface water on multilayer silylation. Silylation coverage was controlled by the availability of surface water, which is consumed in multilayer silylation reactions. Silylation coverage increased with surface water coverage, reaching a maximum at approximately two monolayers of water. The subsequent decline in silylation coverage is attributed to the formation of bulk polysilanes and the decreased accessibility of the water-bearing surface to the hydrophobic VTMS molecules. Atomic force microscopy images revealed a nanometer-scale clusterlike surface morphology consistent with the formation of bonded polysilanes. The present study suggests that multilayered silylated surfaces can be prepared reproducibly. Such surfaces could prove useful in applications that require a high concentration of surface active groups such as in ceramic membrane modification, construction of biocompatible surfaces, and adhesion enhancement in polymer composites.

manufacturable, high throughput process. Currently, In this paper, we present the latest advancements 75 mm diameter InP substrates are used and EBL of sub 50 nm InGaAs/InAlAs/InP High Electron lithography requires less than 1 hour for exposure Mobility Transistor (InP HEMT) devices that have over the wafer. A maximum wafer throughput of 150 achieved extrapolated Fmax above 1 THz. This wafers per week and 100 wafers per week on 100 mm extrapolation is both based on unilateral gain (1.2 diameter wafers would be possible on a single EBL THz) and maximum stable gain/maximum available system. A 2nd key enhancement is the reduction of gain (1.1 THz) extrapolations, with an associated fT of ohmic contact resistance through a higher doped cap 385 GHz. This extrapolation is validated by the layer design coupled with a InAs/InGaAs channel demonstration of a 3-stage common source low noise grown by molecular beam epitaxy. The sheet MMIC amplifier which exhibits greater than 18 dB gain resistance of the epitaxial layers is lowered to 75 at 300 GHz and 15 dB gain at 340 GHz. ohm/sq. (compared to 110 ohm/sq. in the baseline InP HEMT profile) and the mobility was improved to as INTRODUCTION high as 15,000 cmA2N-sec (compared to 12,000 Future systems will extend the need for higher cmA2/V-sec in the baseline InP HEMT profile). A low frequency and bandwidth devices and circuits beyond contact resistance of 0.05 ohm-mm and a high peak current capability and concepts. Rapid development transconductance as high as 2300 mS/mm was and advancement of solid state transistor and MMIC measured at 1V drain bias with a device breakdown technology has pushed extremely high cutoff typically of 2.5V and a maximum drain source voltage frequency and high maximum oscillation frequencies of 2V and good device pinchoff characteristics. (Fmax) in various technologies [1][2][3]. This paper describes the latest advancements of sub 50 nm InP HEMT DEVICE MEASUREMENTS InGaAs/InAlAs/InP High Electron Mobility Transistor S-parameter measurements on extended (InP HEMT) devices that have achieved extrapolated reference plane 2 finger 20 um grounded CPW Fmax above 1 THz for the first time to the best of our devices with 2-mil thick substrates were measured knowledge and is validated by the demonstration of a from 1-110 GHz. The grounded CPW and extended 3-stage low noise MMIC amplifier at 340 GHz with reference plane serve to reduce measurement and greater than 15 dB gain. calibration issues such as probe coupling and substrate modes. The device performance is deInP HEMT DEVICE FABRICATION embedded using an EM simulated SOLT calibration To develop the THz Fmax InP HEMT device, structures fabricated on-wafer. H21 and maximum several process enhancements were implemented on stable gain (MSG) are relatively smooth and follows NGST's baseline InP HEMTs [4]. One key process the theoretical slope of -20 dB/decade and -10 enhancement was the reduction of gate length from dB/decade slope closely from 1 -110 GHz. The 70 to less than 50 nm. Based on cross sections ext...

No abstract

The kinetics of aqueous free‐radical graft polymerization of 1‐vinyl‐2‐pyrrolidone onto silica activated with vinyltrimethoxysilane was studied with a mechanistic polymerization model and experimental data for a temperature range of 70–90 °C. The polymerization was initiated with hydrogen peroxide with initial monomer concentrations ranging from 10 to 40 vol %. The kinetic model, which incorporates the hybrid cage–complex initiation mechanism, describes the experimental polymerization data for which the kinetic order, with respect to the monomer concentration, varies from 1 to . Surface chain growth occurs by both monomer addition and homopolymer grafting, although the latter contribution to the total polymer graft yield is less significant. Increasing the initial monomer concentration enhances both surface polymer density and average grafted chain length. Increasing reaction temperature, however, produces a denser surface layer of shorter polymer chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 26–42, 2002