Fundamental electron-precursor-solid interactions derived from time dependent electron beam induced deposition simulations and experiments

Abstract

Unknown parameters critical to understanding the electron-precursor–substrate interactions during electron beam induced deposition (EBID) have long limited our ability to fully control this nanoscale, directed assembly method. We report here values for the fundamental interaction parameters of D, the precursor surface diffusion coefficient, delta, the sticking probability and tau, the mean surface residence time which are critical parameters for understanding the assembly of EBID deposits. Values of D=6.4um2s-1, delta=0.0250 and tau=3.2ms were determined for a commonly used precursor molecule tungsten hexacarbonyl W(CO)6. Space and time predictions of the adsorbed precursor coverage C(r,t) were solved by an explicit finite differencing numerical scheme. Evolving nanopillar surface morphology was derived from solutions of C(r,t) considering electron induced dissociation as the critical depletion term. This made it possible to infer the space and time dependent precursor coverage both on, and around nanopillar structures to better understand local precursor dynamics during mass transport limited (MTL) and reaction–rate limited (RRL) EBID.