原子力显微镜研究Si（111）和Si（100）上纳米硅化钴肖特基势垒
Conducting Atomic Force Microscopy Studies of Nanoscale Cobalt Silicide Schottky Barriers on Si(111) and Si(100)
摘要：
硅化钴（CoSi 2）岛的形成是通过在超高真空（UHV）中在干净的Si（111）和Si（100）衬底上沉积钴的薄膜（~0.1至0.3 nm），然后退火至~880 ℃。导电原子力显微镜已进行这些岛屿上的特征和测量其电流-电压（I-V）特性。利用电子发射理论分析了器件的电流-电压曲线，得到了硅化物岛与硅衬底之间的肖特基势垒高度和理想因子。对样品（“钝化表面”）非原位进行电流-电压测量，其中岛周围的硅表面用天然氧化物钝化。其他样品（“清洁表面”）保持在UHV下，同时记录I-V曲线。通过比较两种表面上岛的势垒高度和理想因子，研究了非钝化表面对导电的影响。清洁表面势垒高度被发现是约0.2至0.3 eV以下的势垒高度从钝化表面上类似的岛屿测量。肖特基势垒的降低主要归因于清洁硅表面的非钝化表面态对费米能级的钉扎。然而，所测量的清洁表面岛的势垒高度在Si（111）和Si（100）上是相等的，这表明未钝化的表面受到钴杂质的影响。此外，清洁表面上的岛的势垒高度低于由于单独的费米能级钉扎，并且额外的势垒高度降低主要归因于扩展电阻效应。肖特基势垒的不均匀性也可能导致额外的势垒高度降低和接触中的非理想性。随着温度的降低，清洁表面势垒高度降低，理想因子增加，这是由于费米能级的温度变化。
英文摘要：
Cobalt silicide (CoSi2) islands have been formed by the deposition of thin films (~0.1 to 0.3 nm) of cobalt on clean Si(111) and Si(100) substrates in ultrahigh vacuum (UHV) followed by annealing to ~880 degrees C. Conducting atomic force microscopy has been performed on these islands to characterize and measure their current-voltage (I-V) characteristics. Current-voltage curves were analyzed using thermionic emission theory to obtain the Schottky barrier heights and ideality factors between the silicide islands and the silicon substrates. Current-voltage measurements were performed ex situ for samples ("passivated surfaces") where the silicon surface surrounding the islands was passivated with a native oxide. Other samples ("clean surfaces") remained in UHV while I-V curves were recorded. By comparing barrier heights and ideality factors for islands on both surfaces, the effects of the non-passivated surfaces on conduction were studied. The clean surface barrier heights were found to be ~0.2 to 0.3 eV below barrier heights measured from similar islands on passivated surfaces. The reduced Schottky barrier is mainly attributed to Fermi level pinning by non-passivated surface states of the clean silicon surface. However, the measured barrier heights of the clean surface islands are equivalent on both Si(111) and Si(100), suggesting that the non-passivated surfaces are influenced by cobalt impurities. Furthermore, the barrier heights of islands on the clean surfaces are lower than due to Fermi level pinning alone and the additional barrier height lowering is primarily attributed to spreading resistance effects. Schottky barrier inhomogeneity may also cause additional barrier height lowering and non-ideality in the contacts. The clean surface barrier heights decreased and the ideality factors increased with decreasing temperature, which is attributed to the temperature variation of the Fermi level.
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