Secondary-electron velocity spectra and angular distributions from ions penetrating thin solids

Abstract

We present velocity spectra and angular distributions of secondary electrons emitted from cleaned surfaces of thin carbon and gold foils penetrated by H+ (Ep = 0.8 and 1.2 MeV), H2+ (Ep/Mp = 0.8 MeV/u) and C+ (Vp = 2.30- and 2.85 VB). Prominent structures in doubly differential velocity spectra d2n/dEdΩ of secondary electrons (SE) are (1) the "true SE" peak at low electron energies Ee < 10 eV, (2) the binary encounter peak at electron velocities Ve = 2Vp cos θ (observation angle θ), (3) convoy electrons at Ve = Vp (θ = 0°), (4) loss electrons (from ions carrying electrons) at Ve = - Vp at θ = 180° (backward direction!), and (5) low-energy peaks (Ee < 25 eV) resulting from the decay of plasmons. Another collective effect, the directed emission of shock electrons perpendicular to the heavy-ion-induced wake in the electron plasma of the solid, can be observed in angular distributions of secondary electrons. This phenomenon is used to study the refraction of low-energy electrons at solid surfaces. Furthermore, it was found that secondary electron emission from metals and YBaCuO high-temperature superconductors depends on the target temperature. © 1990.