Fig. 3. Normal and parametric resonances of a Si NW observed by in situ TEM. (a) Normal mode (n = 2) resonant motions from the 1^st order to the 5^th order at ∼2.2 MHz, ∼14.9 MHz, ∼41.8 MHz, ∼82.5 MHz and ∼137.5 MHz. Node positions are marked by red solid circles. (b) Parametric resonance (n = 4) from the 1^st order to the 5^th order at ∼1.1 MHz, ∼7.2 MHz, ∼20.4 MHz, ∼41.0 MHz and ∼68.6 MHz. (c) Simulated resonant shapes from the 1^st order to the 5^th order. (d) Plot of resonant frequencies of normal and parametric resonances (n = 2 and 4) from the 1^st order to the 5^th order.