Control of Silicon quantum structures and its application to room-temperature device operation

研究了硅烷（SiH_4）低压气相沉积在超薄SiO_2上自组装硅量子点（SiQDs），提出了SiQDs定位的形成机理，并开发了一种控制SiQDs排列的实用工艺。此外，对覆盖极薄SiO_2的多层堆叠siqd，在室温下测量了其特定的非线性电导及其时间变化。本研究的主要结果和成果如下：(1)由于SiO_2表面的Si-OH键是SiH_4-LPCVD的反应位点，因此控制Si-OH键的位置可以控制SiO_2上SiQDs的排列。(2)由于碳氢化合物和/或水分子的物理吸附，表面污染严重破坏了Si点排列的区域选择性成核，这在暴露于洁净室空气中是不可避免的。(3)采用扫描探针显微镜等表面改性技术，在SiO_2表面的某一位置或区域有意地形成Si-OH键。在此基础上，开发了一种无污染的选择性成核工艺，实现了siqd的高选择性生长和精确定位。(4)利用原子力显微镜（AFM）的形貌和电流图像对超薄SiO_2层夹心SiQDs阵列的双势垒结构进行了表征。结果表明，每个SiQDs的共振隧穿不仅取决于点的大小，还取决于相邻点之间电子电荷的差异。(5)通过使用开尔文探针模式操作AFM针尖所测量的局部表面电位的变化，可以推导出进入siqd的电子电荷量。(6)研究了通过重复点形成和表面氧化制备的SiO_2覆盖多层siqd的电子传递，并在室温下测量了隧道电流通过耦合siqd时明显的随机电报噪声（RTN）。偏置电压对RTN中频率和电流变化的依赖性表明，观察到的RTN现象可以解释为电子在耦合量子点隧穿路径附近的点上充电和放电。少

Self-assembling formation of silicon quantum dots (SiQDs) on ultrathin SiO_2 by low pressure CVD using silane (SiH_4) has been studied, and the formation mechanism for positioning SiQDs has been proposed and a practical process to control the arrangement of the SiQDs has been developed. In addition, for multiply-stacked SiQDs covered with very thin SiO_2, specific non-linear conductance and its temporal variation have been measured at room temperature. The major results and achievements of this research are as follows :(1) Since Si-OH bonds on the SiO_2 surface act as reactive sites in SiH_4-LPCVD, the position control of the Si-OH bonds enables us to control the arrangement of the SiQDs on SiO_2.(2) Area-selective nucleation for the Si dot arrangement is degraded seriously by surface contamination due to physisorption of hydrocarbons and/or water molecules, which is inevitable in exposure to clean room air.(3) Surface modification techniques using a scanning probe microscope such as A … More FM or STM have been applied to form the Si-OH bonds out the SiO_2 surface intentionally at a certain position or area. Based on these techniques, a contamination-free process for the selective nucleation has been developed to realize highly-selective growth and precise positioning of the SiQDs.(4) The double barrier structures of a SiQDs array sandwiched with ultrathin SiO_2 layers have been characterized by simultaneously-measured AFM topographic and current images, The results show that the resonant tunneling through each of the SiQDs depends on not only the dot size but also the difference in electron charging among the neighboring dots.(5) The amount of electron charging into the SiQDs can be derived from the change in the local surface potential measured by operating an AFM tip with a Kelvin probe mode.(6) The electron transport through multiply-stacked SiQDs covered with SiO_2, which were prepared by repeating the dot formation and the surface oxidation, has been studied and distinct random telegraph noise (RTN) in tunneling current, through coupled SiQDs has been measured even at room temperature. The bias voltage dependence of the frequency and the current variation in the RTN suggests that the observed RTN phenomenon can be interpreted in terms of electron charging and discharging in the dots being the neighbor of the tunneling path for coupled quantum dots. Less