Muthukumar Kaliappan, Valentí Roser, Jeschke Harald O
Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
J Chem Phys. 2014 May 14;140(18):184706. doi: 10.1063/1.4873584.
Tungsten and cobalt carbonyls adsorbed on a substrate are typical starting points for the electron beam induced deposition of tungsten or cobalt based metallic nanostructures. We employ first principles molecular dynamics simulations to investigate the dynamics and vibrational spectra of W(CO)6 and W(CO)5 as well as Co2(CO)8 and Co(CO)4 precursor molecules on fully and partially hydroxylated silica surfaces. Such surfaces resemble the initial conditions of electron beam induced growth processes. We find that both W(CO)6 and Co2(CO)8 are stable at room temperature and mobile on a silica surface saturated with hydroxyl groups (OH), moving up to half an Angström per picosecond. In contrast, chemisorbed W(CO)5 or Co(CO)4 ions at room temperature do not change their binding site. These results contribute to gaining fundamental insight into how the molecules behave in the simulated time window of 20 ps and our determined vibrational spectra of all species provide signatures for experimentally distinguishing the form in which precursors cover a substrate.
吸附在基底上的钨羰基化合物和钴羰基化合物是基于钨或钴的金属纳米结构电子束诱导沉积的典型起始点。我们采用第一性原理分子动力学模拟来研究W(CO)6和W(CO)5以及Co2(CO)8和Co(CO)4前驱体分子在完全羟基化和部分羟基化的二氧化硅表面上的动力学和振动光谱。这样的表面类似于电子束诱导生长过程的初始条件。我们发现，W(CO)6和Co2(CO)8在室温下都是稳定的，并且在羟基（OH）饱和的二氧化硅表面上可以移动，移动速度可达每皮秒0.5埃。相比之下，室温下化学吸附的W(CO)5或Co(CO)4离子不会改变它们的结合位点。这些结果有助于深入了解分子在20皮秒的模拟时间窗口内的行为，并且我们确定的所有物种的振动光谱为实验区分前驱体覆盖基底的形式提供了特征。
