Motion of individual atoms and mesoscopic structural dynamics on non-equillibrium surfaces

为了实现对非平衡表面上单个原子和分子动态运动的直接观察，并了解其微观机理，我们研制了一种新型的变温扫描探针显微镜。为了进一步研究表面动力学，我们还用热脱附和高分辨电子能量损失谱研究了（NO+CO）共吸附体系在Pd（100）表面上的有序性。噪声信号输出。地形成像模式的垂直噪声为3 pm（p-p），这使得能够对过渡金属的（100）和（111）表面进行成像。这种显微镜还可以在低至1 pA的隧穿电流下工作，这使得对低电导率材料如有机晶体的成像成为可能.在应用扫描探针显微镜之前，我们用低能电子衍射、热脱附和振动光谱研究了（NO+CO）/Pd（100）共吸附体系的有序性.我们发现，NO和CO形成稳定的混合有序相，并在混合有序相中进行爆炸性CO2生成反应。采用基于格子气模型的Monte Carlo动力学模拟方法研究了NO-CO分子间的相互作用，并对H+H/Pd（100）反应进行了研究，发现H原子的碰撞迫使预吸附的H原子进入Pd体（冲压吸收）。讨论了MH 2体系势能面的特征。

In order to realize the direct observation of the dynamic motion of individual atoms and molecules on the non-equillibrium surfaces and to understand the underlying microscopic mechanism, we have developped a new variable-temperature scanned probe microscope. In order to study further on the surface dynamics, we have also conducted thermal desorption and high-resolution electron energy loss spectroscopy to investigate the ordering in the (NO+CO) coadsorption system on the Pd (100) surface.The scanned probe microscope developped in the present study can be operated under ultrahigh vacuum and at sample temperature from 100 to 1000K.Another important characteristic is its low-noise signal output. The vertical noise for the topographic imaging mode is 3pm (p-p), which enables the imaging of (100) and (111) surfaces of transition metals. This microscope can also be operated at tunneling current as low as 1pA, which enables imaging of low-conductivity materials such as organic crystals.The ordering in (NO+CO) /Pd (100) coadsorption system has been studied by low-energy electron diffraction, thermal desorption and vibrational spectroscopy preparatory to the application of the scanned probe microscope. We have found that NO and CO form stable mixed ordered phases and that an explosive CO2 formation reaction undergoes in the mixed ordered phases. A kinetic Monte Carlo simulation based on a lattice-gas model has been done to quantify NO-CO intermolecular interactions.We have also investigated on the H+H/Pd (100) reaction and found that the impinging H atoms force the preadsorbed H atoms to penetrate into Pd bulk (stamping absorption). The characteristics of the potential energy surface for the MH2 system was discussed.