Nanofabrication Research Laboratory, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37381-6487, USA.
ACS Nano. 2010 Mar 23;4(3):1619-29. doi: 10.1021/nn901363a.
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 that describe the precursor-solid interaction, the precursor surface diffusion coefficient (D), the precursor sticking probability (delta), and the mean precursor surface residence time (tau), which are critical parameters for understanding the assembly of EBID deposits. Values of D = 6.4 microm(2) s(-1), delta = 0.0250, and tau = 3.20 ms were determined for a commonly used precursor molecule, tungsten hexacarbonyl W(CO)6. Space and time predictions of the adsorbed precursor coverage were solved by an explicit finite differencing numerical scheme. Evolving nanopillar surface morphology was derived from simulations 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.
长期以来，理解电子束诱导沉积（EBID）过程中电子前体-底物相互作用的未知参数一直限制了我们完全控制这种纳米级定向组装方法的能力。我们在此报告了描述前体-固体相互作用、前体表面扩散系数（D）、前体附着概率（δ）和前体表面平均停留时间（τ）的值，这些值是理解 EBID 沉积物组装的关键参数。对于一种常用的前体分子六羰基钨 W(CO)6，确定了 D = 6.4 µm2 s-1、δ = 0.0250 和 τ = 3.20 ms。通过显式有限差分数值方案求解了吸附前体覆盖率的空间和时间预测。考虑到电子诱导的离解是关键的消耗项，从模拟中推导出了纳米柱表面形貌的演变。这使得在纳米柱结构上和周围更好地理解质量传输受限（MTL）和反应速率受限（RRL）EBID 过程中局部前体动力学成为可能，从而可以推断出空间和时间相关的前体覆盖率。
