Submicron x-ray diffraction and local strain of embedded GaAs nanowires in trenched Si substrate
Ling Lee(李寧)1,2*, Ching-Shun Ku(古慶順)3
1Center of Nanoscience and Technology, Tunghai University, Taichung, Taiwan
2Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan
3National Synchrotron Radiation Research Center, Hsinchu, Taiwan
* presenting author:李寧,
A novel technique based on synchrotron radiation submicron x-ray diffraction was introduced to directly measure the local strain and the spatial distribution in GaAs nanowires, which are embedded in long trenches on Si wafer along [1-10] with SiO2 sidewalls. The two-dimensional scan of x-ray diffraction was performed by the pseudo-polychromatic x-ray beam with a horizontal and vertical size of 250 nm and 350 nm, respectively, at beamline 34-ID-E in Advanced Photon Source.

The dilatation components of the local stress tensor of GaAs were deduced by the Laue spots diffracted by (008), (3-315), and (228) planes. It is observed that a large in-plane tension occurs along [1-10] than that along [110]. In addition, the spatial distribution of strain in a single wire and the dependence of strain on the ratio between trench width and sidewall width were measured. These results indicate that the anisotropic strain could be explained by the induced compression by SiO2 sidewalls. The induced stress results from the smaller thermal expansion coefficient of SiO2, and the value is determined by the volume ratio between GaAs and SiO2.

Furthermore, the submicron X-ray diffraction facility BL21A established in Taiwan Photon Source (TPS) with a better spatial resolution and much more opportunities of simultaneous analyses was also introduced in this talk.

Keywords: submicron x-ray diffraction, GaAs, strain, Taiwan Photon Source