Monolithic integration of functional oxides in silicon by chemical solution deposition

In the past years, great efforts have been devoted to combine the functionality of oxides with the performances of semiconductor platforms for the development of novel and more efficient device applications. However, further incorporation of functional oxide nanostructures as active materials in electronics critically depends on the ability to integrate crystalline metal oxides into silicon structures [1]. In this regard, the presented work takes advantage of all the benefits of soft chemistry to overcome the main challenges for the monolithic integration of novel nanostructured functional oxide materials on silicon including (i) epitaxial piezoelectric α-quartz thin films with tunable textures on silicon wafers [2] and (ii) ferromagnetic La0.7Sr0.3MnO3 (LSMO) thin films epitaxially grown on (100)-silicon at low temperature. Importantly, piezoelectric quartz growth mechanism is governed by a thermally activated devitrification of the native amorphous silica surface layer assisted by a heterogeneous catalysis under atmospheric conditions driven by alkaline earth cations present in the precursor solution. Quartz films are made of perfectly oriented individual crystallites epitaxially grown on (100) face of Si substrate with a controlled porosity after using templating agents [3]. Moreover, a quantitative study of the converse piezoelectric effect of quartz thin films through piezoresponse force microscopy shows that the piezoelectric coefficient d33 is between 1.5 and 3.5 pm/V which is in agreement with the 2.3 pm/V of the quartz single crystal d11. Epitaxial LSMO thin films synthesis, involves the use of polymer assisted deposition (PAD) process [4] combined with the controlled epitaxial growth of SrTiO3 buffer layer grown by molecular beam epitaxy (MBE) at the silicon surface, which allowed LSMO thin films to stabilize and crystallize at low temperature. All together, the methodology presented here exhibits a great potential and offers a pathway to design novel oxide compounds on silicon substrates by chemical routes with unique optical, electric, or magnetic properties. [1] A. Carretero-Genevrier et al. Nanoscale, 20, 892-897. (2014). [2] A. Carretero-Genevrier et al. Science, 20, 892-897. (2013). [3] G.L. Drisko et al. Adv.Funct.Mater. 24, 5494–5502 (2014) [4] Q. X. Jia, et al. Nature Materials 3, 529 (2004)