Desorption of deposited species plays a role in determining the evolution of surface morphology during crystal growth when the desorption time constant is short compared with the time to diffuse to a defect site, step edge, or kink. However, experiments to directly test the predictions of these effects are lacking. Novel techniques such as in situ coherent x-ray scattering can provide significant new information. Herein we present x-ray photon correlation spectroscopy (XPCS) measurements during diindenoperylene (DIP) vapor deposition on thermally oxidized silicon surfaces. DIP forms a nearly complete two-dimensional first layer over the range of temperatures studied (40–$120{}^{\circ }\text{C}$), followed by mounded growth during subsequent deposition. Local step flow within mounds was observed, and we find that there was a terrace-length-dependent behavior of the step edge dynamics. This led to unstable growth with rapid roughening ($\beta >0.5$) and deviation from a symmetric error-function-like height profile. At high temperatures, the grooves between the mounds tend to close up leading to nearly flat polycrystalline films. Numerical analysis based on a $(1+1)$-dimensional model suggests that terrace-length dependent desorption of deposited ad-molecules is an essential cause of the step dynamics, and it influences the morphology evolution.

中文翻译：

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解吸薄膜生长中的局部阶跃流动力学

当解吸时间常数与扩散到缺陷位点、台阶边缘或扭结的时间相比较短时，沉积物质的解吸在决定晶体生长过程中表面形态的演变方面发挥着重要作用。然而，缺乏直接测试这些效应预测的实验。原位相干 X 射线散射等新技术可以提供重要的新信息。在此，我们介绍了热氧化硅表面上二茚并苝 (DIP) 气相沉积期间的 X 射线光子相关光谱 (XPCS) 测量。 DIP 在研究的温度范围内（40-$120{}^{\circ }\text{C}$），然后在随后的沉积过程中形成堆状生长。观察到土丘内的局部台阶流，我们发现台阶边缘动力学存在依赖于平台长度的行为。这导致不稳定的生长和快速粗糙化（$\beta >0.5$）以及与类似误差函数的对称高度轮廓的偏差。在高温下，土堆之间的凹槽往往会闭合，形成几乎平坦的多晶薄膜。基于数值分析$（1+1）$维模型表明，沉积的广告分子的平台长度依赖性解吸是阶跃动力学的重要原因，并且它影响形态演化。