Adsorption Kinetics of Cs on GaAs

Abstract

Cesium adsorption on vacuum-cleaved p-GaAs (110) was monitored at 10−10 Torr concurrently by photoemission and x-ray photoelectron spectroscopy (ESCA). Cesium was supplied at R = 6.9×1012 atoms/cm2 sec by a calibrated valved room-temperature Knudsen effusion cell. ESCA results showed that the first monolayer of Cs contains N = 6.2×1014 atoms/cm2, that it adsorbs irreversibly, and that fractional coverage is θ = 1−exp(− Rt/N). Maximum photoyield (hence minimum work function) corresponds to θ = 1. The second layer of Cs decreases photoyield, but is desorbed with a time constant of less than 1 min.

Tunable Multifuctionality in Heusler Alloys by Extreme Conditions

“…The elemental ratio is influenced using energy-dispersive analysis of X-rays, which provide the actual chemical ratio as Ni 1.99 Mn 1.01 Ga 1.00 and Ni 1.9 Mn 1.15 Ga 0.95 for x = 0 (Ni 2 MnGa) and 0.15 (Ni 1.85 Mn 1.15 Ga), respectively. The magnetic studies are accomplished at different pressures by 9 Tesla Physical Property Measurement System (PPMS-9T)-Vibrating Sample Magnetometer (VSM) (Quantum design, USA) module furnished with the Cu-Be clamp-type pressure cell with 10 kbar upper pressure [28]. The thermomagnetic data are recorded with VSM for both cooling and heating mode in the temperature range of 2 K-300 K under ambient and high pressures up to 7.4 kbar for Ni 1.85 Mn 1.15 Ga (x = 0.15) and 9.69 kbar for Ni 2 MnGa (x = 0) nominal compositions at a constant magnetic field of 0.01 T. The isothermal magnetization M (H) is recorded up to 5 T at ambient and high pressure at different temperatures (180-250 K: x = 0 & 130-160 K: x = 0.15) across T M .…”

“…Nevertheless, resistivity, piezoresistance (PR) [25], and pressure-induced phase transition [26,27] are renowned as important phenomena that occur in Heusler alloys. PR is the change in resistance provoked by pressure effect was first discovered by Smith [28] in semiconductors (Si, Ge) possessing anisotropic energy with wide band structures. Further, they are being broadly used as stress and strain sensors [29].…”