• Marcaud, Guillaume
• Alonso-Ramos, Carlos
• Damas, Pedro
• Agnus, Guillaume
• Pillard, Valerie
• Vivien, Laurent
• Marris-Morini, Delphine
• Roux, Xavier Le
• Berciano, Mathias
• Maroutian, Thomas
• Matzen, Sylvia
• Lecoeur, Philippe
• Cassan, Eric

Abstract

The hybrid integration of oxides on silicon or sapphire is promising to bring other properties (such as multiferroicity or piezoelectricity) that can be combined and tuned at the nanoscale to develop new devices. Moreover, their epitaxial growth and difference of thermal expansion induce strain that can be used to break the symmetry and reveal second-order nonlinear effect in silicon. This work is mainly devoted to optimization of the growth of functional oxides such as YSZ (Yttria-Stabilized Zirconia) on sapphire and silicon, in order to control the crystalline quality, the control of strain distribution and the interfaces YSZ/Si. Epitaxial growth of YSZ thin films Preliminary optical and strain measurements on YSZ on silicon Conclusions Perspectives POPSTAR In the case of YSZ, the yttrium content can be used to tune the lattice mismatch with silicon and thus the epitaxial strain. The growth of YSZ on sapphire substrate allows measuring optical properties of this oxide without silicon interface effects. Functional oxides are deposited by epitaxial growth (pulsed-laser deposition) on silicon and so naturally induce strong strain due to large lattice parameter mismatch. Furthermore the difference of thermal expansion coefficients between YSZ and silicon is 5 times higher than Si 3 N 4 Si YSZ S i O 2 SEM image of silicon strip waveguide strained with epitaxial YSZ thin film Pulsed-laser deposition (PLD) Red parameters have been tested :  Sapphire : oxygen pressure [3] and surface state of the substrate are the most important parameters which lead to the growth of (002) or (111)YSZ on sapphire C-cut. Even if we have seen only (002)YSZ on sapphire R-cut, the quality is lower than on C-cut.  Silicon : oxygen pressure is the key parameter to grow epitaxially YSZ on silicon and to reduce the silica thickness at the interface. Map of Si raman peak [2] Wolf, " Micro-Raman Spectroscopy to Study Local Mechanical Stress in Silicon Integrated Circuits. " Semicond. Sci. Technol. 1996 • Shift of Si Raman peak : Waveguide strained by YSZ about 500 MPa [2]. • Weak transmission of 30 dB/cm. Need to improve the quality of the growth and control YSZ/Si interface. Transmission measurement at 1,55 µm Sapphire structure • Efficiently control and understand the chemical and thermal treatment of the substrates • Fabricate optical structures of YSZ on sapphire including waveguides • Optimize the growth quality of YSZ on silicon to avoid formation of silica at interface and increase the strain generation • Study the strain on different structures of silicon with different process of YSZ growth in PLD • YSZ-strained Si waveguides :-From First measurements, transmission in YSZ-strained Si waveguides is quite low, showing that the quality of the waveguides has to be further improved.-Si waveguides have been elaborated and strained thanks to the difference of thermal expansion of YSZ thin films and silicon substrate (strain evidenced by Raman measurements). • Epitaxial growth on sapphire :-The growth of YSZ thin films on sapphire has been optimized by studying the effects of all the PLD parameters.-Oxygen pressure and state surface of the substrate are the key to control YSZ growth orientation and films quality.-Optimized films surface exhibits a very low roughness (below 1nm) with atomic steps (related to the ones of the substrate).-Films grown on C-cut substrates have significantly better crystalline quality than on R-cut substrates. Only one orientation of YSZ film (002) can be stabilized with substrate treatment.-2-1

Topics

• Deposition
• impedance spectroscopy
• surface
• scanning electron microscopy
• thin film
• Oxygen
• thermal expansion
• Silicon
• Yttrium
• Raman spectroscopy