Varian Associates

About: Varian Associates is a based out in . It is known for research contribution in the topics: Beam (structure) & Amplifier. The organization has 2160 authors who have published 2591 publications receiving 46002 citations.

Polar mode scattering in ballistic transport GaAs devices

Abstract: Polar optic scattering in a ballistic transport n-GaAs device at 77 K is shown to be significant for voltages above the threshold for polar phonon emission, 0.035 V. Monte Carlo results for electron effective velocities at fields expected in such devices support this conclusion.

Spectrosorptance measuring system and method

Abstract: Apparatus and method for measuring the absolute absorptance of a relatively thin sample displaying both reflecting and transmitting characteristics. An integrating sphere is provided, and monochromatic reference and sample beams are projected into the sphere from a pair of angularly-spaced ports. Detector means are positioned at the sphere to receive illumination from the internal sphere wall, including the illumination arising from the first reflectance from that portion of the sphere directly illuminated by the sample and reference beams. The reference and sample electrical signals proceeding from the detector are equalized over the wavelength range of the instrument to establish a relatively flat baseline with the sample withdrawn from the sample beam. The sample is then repositioned within the sample beam. By virtue of the position of the detector and the thinness of the sample, the detector views the illumination of the sphere wall, but substantially excludes the first reflectance and scattered energy from the sample. The light falling on the detector due to illumination of the sphere via the sample is compared with the light falling on the detector due to illumination of the sphere by the reference beam, the ratio between the two providing a direct measure of the quantity of incident sample beam energy transmitted and reflected by said sample. By subtracting the thus determined reflectance and transmittance of the sample from unity, the absorptance of the sample may be directly indicated.

Sputter system incorporating an improved blocking shield for contouring the thickness of sputter coated layers

Abstract: The arbitrary contouring of thickness of a sputter-deposited film is made possible by a blocking means having a primary blocking shield and an ancillary blocking shield. The primary blocking shield intercepts atoms sputtered directly from the cathode target by line-of-sight transport. The ancillary blocking shield extends downwardly from the side of the primary blocking shield which is placed closest to the substrate. The ancillary blocking shield intercepts atoms sputtered from the cathode which by intervening gas collisions have been redirected to travel underneath the primary blocking shield. Precise tailoring of the thickness profile of the coating on the substrate is thereby provided and the quality of the composite film is maintained. The method for contouring the thickness of sputter coated layers comprises sputter coating portions of the film at successive stations. By employing the improved blocking shield at selected stations, the film in the aggregate may have the desired thickness contour.

TRIPLET STATE STUDIES OF FLAVlNS BY ELECTRON PARAMAGNETIC RESONANCE—II

Abstract: — A continuation of studies is presented on the excited triplet state of flavins using EPR techniques. Detailed experiments are reported on the triplet state of flavin-mono-nucleotide (FMN) and flavin-adenine-dinucleotide (FAD). Action spectra of triplet yield are explained in terms of the optical absorption for FMN and FAD. Effects of light saturation, concentration quenching and oxygen on the triplet state are discussed. It is suggested that the rate constant k3 for the intersystem crossover from the excited singlet to the triplet state is increased by oxygen and quenchers such as KI. Detailed kinetic studies are presented on the formation of the triplet state.