Surface Energy Engineering (SEE) Correlated to Crystal Anisotropy of Piezo-Electric LiTaO3 for Nano-Bonding to Si and alpha-quartz SiO2 (T \textless 453 K)

One of the most piezoelectric materials, LiTaO3, is ideal for voice activated Si chips. Currently, heteroepitaxy (HE) and Direct Wafer Bonding (DWB) can't integrate highly anisotropic (c/a$=$2.7) trigonal LiTaO3 to cubic diamond Si (c-Si)-- nor to trigonal alpha -quartz SiO2 (a-qSiO2, c/a$=$1.1). The lattice mismatch is 255{\%}, thus HE is impossible. Moreover, the thermal expansion mismatch is huge. LiTaO3 expands 8X more than Si and 25X more than a-qSiO2. LiTaO3 decomposes into Ta2O5 and Li ions at T\textgreater 673K so DWB and HE destroy LiTaO3. But this work uses Nano-Bonding (NB) at T\textless 453K by Surface Energy $\gamma $ Engineering (SEE) to modify surfaces into complementary, unstable states via 2D precursor phases catalyzing NB. Hydro-affinity (HA) and $\gamma $ scales with surface interactions. Three Liquid Contact Angle Analysis (3LCAA) can measure HA and $\gamma $ and map them along crystal directions. Contact angles on LiTaO3 are found to vary significantly by 40{\%} with crystal direction. Anisotropy of HA correlates with $\gamma $. $\gamma $ varies only 6{\%} with crystal directions and yields insights into SEE.