Study on interfacial interaction between Si and ZnO

Abstract

The interfacial reaction and bonding mechanism of Si based undoped and Al-doped ZnO films were investigated experimentally and numerically. Si/ZnO heterojunctions were fabricated onto p-Si(100) wafers by RF magnetron sputtering, then the undoped and Al doped ZnO (AZO) films coated Si substrates were annealed in argon atmosphere (ZnO-Ar and AZO-Ar) and air atmosphere (ZnO-Air and AZO-Air) respectively. X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR) show the prepared Si-based films have wurtzite structure with (002) preferential growth, and demonstrate several Si oxides exist in both cases. X-ray photoelectron spectroscopy (XPS) finds that oxygen vacancies exist in ZnO-Ar, moreover, the stoichiometry between Zn and O in AZO-Ar film to be close to 1:1, and high oxygen content in ZnO-Air, which are also supported by Hall measurement. Furthermore, the Si 2p of XPS spectrum shows the width of interfacial interaction between Si and ZnO become weaker with the order of ZnO-Ar, AZO-Ar and ZnO-Air. To elucidate the joining and bonding mechanism between Si substrate and ZnO coating layer, molecular dynamics and first principle simulations were performed in this work, the simulation results show certain interstitial Si atoms coming from Si substrate interact with O atoms related to the Zn–O bonding at the Si/ZnO interface, and resulting in oxygen vacancies in ZnO film. The experiment and simulation show the interfacial interaction between Si and ZnO depends on oxygen content coming from ZnO coating layer, the limited oxygen coming from ZnO film could increase the width of Si/ZnO interfacial interaction and leave oxygen vacancies in ZnO film due to Si robbing O atoms related to Zn–O bonding.