Micromachined piezo-actuator for full control of in-plane stress in thin films

The tailoring of the elastic strain fields in materials provides a largely unexplored degree of freedom that opens up a new horizon towards the development of engineered materials and new devices similarly to what chemical alloying meant for human civilization [1]. Strain-tunable physical properties of materials is a recent topic in a wide range of research areas like nanophotonics [2], spintronics [3], topological insulators [4] and graphene [5], among others. However, understanding and exploring new physical phenomena on strained materials relies on the ability to develop new techniques that allow full stress (strain) tunability on demand (i.e. major strain magnitude, strain direction and strain anisotropy). The approach presented in this work is based on a micromachined piezo-actuator device fabricated by femtosecond laser cutting [6]. The response of the device is studied by finite element method (FEM) simulations using GaAs nanomembranes bonded on the piezo-actuator. Such simulations demonstrate that our actuators are capable of full control of the in-plane stress configuration and allow strain magnitude values up to about 3%. Preliminary experimental results on strain-tunable GaAs optical properties confirm the expectations. References [1] J. Li, Z. Shan, and E. Ma, MRS Bulletin, 39 (2014) 108 - 162. [2] R. Trotta, P. Atkinson, J.D. Plumhof et al., Adv. Mater., 24 (2012) 2668 - 2672. [3] N. Lei, T. Devolder, G. Agnus et al. Nat. Commun., 4 (2013) 1378. [4] Y. Liu, Y.Y. Li, S. Rajput et al., Nat. Phys., 10 (2014) 294 - 299. [5] F. Ding, H. Ji, Y. Chen et al., Nano Lett., 10 (2010) 3453 - 3458. [6] A. Rastelli, I. Daruka, and R. Trotta , " Verfahren zur Durchstimmung der Verspannung in Dünnschichten" , patent submitted (2014).