SECONDARY-ELECTRON VELOCITY SPECTRA AND ANGULAR-DISTRIBUTIONS FROM IONS PENETRATING THIN SOLIDS

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.