Experimental verification of dielectric constant decrease in silicon nanostructures
Experimental verification of dielectric constant decrease in silicon nanostructures
复制标题
硅纳米结构介电常数降低的实验验证
DOI：
10.1117/12.767475
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发表时间：
2008
影响因子：
3.3
通讯作者：
P. Fauchet
中科院分区：
文献类型：
--
作者：
H. G. Yoo;P. Fauchet
在使用硅纳米结构的器件设计中，准确地知道介电函数ε通常是重要的，因为它决定了它们的许多电学和光学性质。一些理论研究预测，随着纳米结构尺寸的减小，介电常数ε会降低。两种相互竞争的物理机制已经被提出：量子限制和表面效应(由于表面可极化键的断裂)。关于ε的尺寸依赖关系的实验工作很少，其中只测量了一个特定的平均尺寸的ε。在我们的工作中，我们用变角椭圆偏振光谱仪测量了入射角度分别为65°、70°和75°时，不同尺寸的薄晶片的ε随尺寸的变化。通过反复对SOI晶片顶层硅层进行等离子体氧化和BOE刻蚀，制备了不同厚度(~15 nm~2.5 nm)的薄晶片。在每个刻蚀步骤之间进行椭偏测量和表面轮廓测量。在波长为1700 nm，硅透明，体相ε为11.7时，我们发现对于2.5 nm厚的硅片，ε降低到7.5.我们的结果首次系统地测量了硅纳米结构的介电函数随尺寸的变化，也是对理论的首次检验。
During the design of devices using Si nanostructures, it is often important to precisely know the dielectric function ε, since it determines many of their electrical and optical properties. Several theoretical studies have predicted a reduction in the dielectric constant ε as the nanostructure size decreases. Two competing physical mechanisms have been proposed for the reduction: quantum confinement and surface effects (due to a breaking of polarizable bonds on the surface). There have been only a few experimental works on the size dependence of ε, in which ε was measured only for one particular average size. In our work, we have measured the size-dependent ε of thin crystalline slabs at different sizes using variable angle spectroscopic ellipsometry from 270 nm to 1700 nm at the incident angles of 65°, 70° and 75°. The thin crystalline slabs of different thicknesses (~ 15 nm to 2.5 nm) were fabricated by repeatedly subjecting the top Si layer of SOI wafers to plasma oxidation and BOE etching. Ellipsometry and surface profile measurements were performed between each etching step. At the wavelength of 1700 nm, for which silicon is transparent and bulk ε is 11.7, we found thatε was reduced to 7.5 for a 2.5 nm thick Si slab. Our results represent the first systematic measurement of the dielectric function of Si nanostructures as a function of size and represent the first test of the theories.