Tuning mechanical modes and influence of charge screening in nanowire resonators arXiv:1001.2882v1 [cond-mat.mes-hall] 18 Jan 2010 We probe electro-mechanical properties of InAs nanowire (diameter ∼ 100 nm) resonators where the suspended nanowire (NW) is also the active channel of a field effect transistor (FET). We observe and explain the non-monotonic dispersion of the resonant frequency with DC gate voltage ( V DC g ). The effect of electronic screening on the properties of the resonator can be seen in the amplitude. We observe the mixing of mechanical modes with V DC g . We also experimentally probe and quantitatively explain the hysteretic non-linear properties, as a function of V DC g , of the resonator using the Duffing equation. Abstract Hari S. Solanki, 1 Shamashis Sengupta, 1 Sajal Dhara, 1 Vibhor Singh, 1 Sunil Patil, 1 Rohan Dhall, 1 Jeevak Parpia, 2 Arnab Bhattacharya, 1 and Mandar M. Deshmukh 1, ∗ $^{1}$Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India $^{2}$LASSP, Cornell University, Ithaca NY 14853 1