When an electron beam impinges on a solid, some particles of the beam come back and emerge from the target surface. These electrons are known as the backscattered electrons. Because of their penetration below the surface and the resulting loss of small amounts of energy by ionizations, electron excitations and plasmon emissions, the backscattered electrons are not reflected without dissipation of energy. A fraction of their energy is indeed lost into the solid before to emerge. When the target is a surface film, i.e. a thin film deposited on a substrate of a different material, the number of backscattered electrons depends on the film thickness, on the electron primary energy and on the materials constituting the film and the substrate. In simulating, with the Monte Carlo method, the processes of penetration and backscattering of electrons impinging on supported thin films one has to take into account the interface between the film and the substrate and, in particular, the change in the scattering probabilities per unit length in passing from the film to the substrate and viceversa. In this paper a Monte Carlo code written to simulate keV electrons interacting with surface films is described. Monte Carlo results concerning 5 to 20 keV electrons backscattered from various films deposited on different substrates are then compared both with experimental and theoretical data.
Monte Carlo simulation of the interaction of electrons with supported and unsupported thin films
Dapor, Maurizio
2003-01-01
Abstract
When an electron beam impinges on a solid, some particles of the beam come back and emerge from the target surface. These electrons are known as the backscattered electrons. Because of their penetration below the surface and the resulting loss of small amounts of energy by ionizations, electron excitations and plasmon emissions, the backscattered electrons are not reflected without dissipation of energy. A fraction of their energy is indeed lost into the solid before to emerge. When the target is a surface film, i.e. a thin film deposited on a substrate of a different material, the number of backscattered electrons depends on the film thickness, on the electron primary energy and on the materials constituting the film and the substrate. In simulating, with the Monte Carlo method, the processes of penetration and backscattering of electrons impinging on supported thin films one has to take into account the interface between the film and the substrate and, in particular, the change in the scattering probabilities per unit length in passing from the film to the substrate and viceversa. In this paper a Monte Carlo code written to simulate keV electrons interacting with surface films is described. Monte Carlo results concerning 5 to 20 keV electrons backscattered from various films deposited on different substrates are then compared both with experimental and theoretical data.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
