硅(001)图形衬底上锗硅纳米线的定位生长

纳米线的定位生长是实现纳米线量子器件寻址和集成的前提.结合自上而下的纳米加工和自下而上的自组装技术,通过分子束外延生长方法,在具有周期性凹槽结构的硅(001)图形衬底上首先低温生长硅锗薄膜然后升温退火,实现了有序锗硅纳米线在凹槽中的定位生长,锗硅纳米线的表面晶面为(105)晶面.详细研究了退火温度、硅锗的比例及图形周期对纳米线形成与否,以及纳米线尺寸的影响.

Controllable growth of Ge Si nanowires on trench patterned Si(001) substrate

Controllable growth of nanowires is a prerequisite for addressability and scalability of nanowire quantum devices. By combining top-down nanofabrication and bottom-up self-assembly, site-controlled Ge Si nanowires with two(105) facets can be grown on Si(001) substrate with pre-patterned trenches. Trenches along the 100]or 010] crystallographic direction with 60 nm in width and 6 nm in height are fabricated on Si substrate by electron beam lithography and reactive ion etching. Subsequently, a 60-nm-thick Si buffer layer is grown at330–400 ℃ on the patterned substrate to improve the surface quality. The facets at the tip of the trenches transform into(11 n) after depositing the Si buffer layer. Self-organized Ge Si nanowires form inside the trenches by depositing the 6-nm-thick Si67 Ge33 film at 450 ℃ followed by 1 h annealing at 510 ℃. The Ge Si nanowires are(105)-faceted with an average height of approximately 7 nm. Furthermore, we systematically study the influence of annealing temperature, Ge concentration and pattern period on the formation of site-controllable Ge Si nanowire on a patterned Si(001) substrate. The Ge Si nanowires can be formed only inside the trenches within a specific annealing temperature ranging from 500 ℃ to 520 ℃. It is also discovered that Ge Si nanowires are very sensitive to Ge concentration, as they cannot form at lower Ge concentration due to a large nucleation energy barrier. In contrast, high Ge concentration will lead to the discontinuity of nanowires caused by higher atomic diffusion barrier. The generated Ge Si nanowires in the trenches exhibit similar dimensions at different pattern periods, which indicates that the growth process is thermodynamically determined. Overall, we realize the controllable growth of the Ge Si nanowires, while the length of nanowires can reach the millimeter even centimeter scales, replying on the patterned trench length. The above results offer a controllable growth method of the Ge nanowires, which could potentially lead to the scalability of the Ge quantum devices on Si substrates.