Articles you may be interested inModeling and simulation for the enhancement of electron storage in a stacked multilayer nanocrystallite silicon floating gate memory

We report low-temperature measurements of dissipation in megahertz-range, suspended, singlecrystal nanomechanical oscillators. At millikelvin temperatures, both dissipation (inverse quality factor) and shift in the resonance frequency display reproducible features, similar to those observed in sound attenuation experiments in disordered glasses and consistent with measurements in larger micromechanical oscillators fabricated from single-crystal silicon. Dissipation in our single-crystal nanomechanical structures is dominated by internal quantum friction due to an estimated number of roughly 50 two-level systems, which represent both dangling bonds on the surface and bulk defects.

We report the observation of discrete displacement of nanomechanical oscillators with gigahertz-range resonance frequencies at millikelvin temperatures. The oscillators are nanomachined single-crystal structures of silicon, designed to provide two distinct sets of coupled elements with very low and very high frequencies. With this novel design, femtometer-level displacement of the frequency-determining element is amplified into collective motion of the entire micron-sized structure. The observed discrete response possibly results from energy quantization at the onset of the quantum regime in these macroscopic nanomechanical oscillators.

Gaidarzhy et al. Reply: In our Letter [1], we reported experimental data on a novel multielement nanomechanical oscillator with mechanical motion at frequencies up to 3 GHz [2]. At a higher cryostat temperature of 1 K, where the thermal occupation number N th k B T=hf 14 for a 1.5 GHz mode, the oscillator behaves classically according to Hooke's law. At 110 mK, where N th k B T=hf 1, response to the driving force shows clear transitions between two discrete states in a dramatic deviation from the monotonic Hooke's-law response. After ruling out a number of classical interpretations, we conjecture that the discrete transitions are possibly of quantum mechanical origin.In their Comment [3], Schwab et al. contend that the discrete transitions observed in the experiment cannot have ''any connection to quantum phenomena.'' We show that such a conclusion cannot be drawn on the basis of their arguments. Second, they claim that the conjecture of energy quantization in the observed mode of the oscillator is in conflict with elasticity theory and magnetomotive detection technique. In addition, Schwab et al., claim that the preamplifier noise will drive the resonator to 440 K ''far above the temperature of 100 mK.'' They also derive an effective resonator temperature of 8800 K from the experimental parameters. As we show below, our experimental data clearly indicate that both of these statements are incorrect.(i) On the measurement scheme.-Contrary to the claim of Schwab et al. [3], quantum nondemolition (QND) measurement is not necessary for the detection of quantized spectrum, as is well known since measurements of discrete atomic spectra over a hundred years ago. Of course, QND is necessary for measurement with continuous monitoring of the quantum system. However, ours is not a continuous measurement. Furthermore, linear driving can prepare a system in certain nonclassical states (e.g., coherent states). The system can be prepared also in an energy eigenstate by linear drive in a two-step process by driving the system to a highly excited state, and then allowing it to relax to an eigenbasis of energy or number states.(ii) On heating due to the preamp backaction noise.-The preamp input noise indeed contributes to the heating of the oscillator, but the question is whether this heating raises the sample temperature to hundreds of Kelvin or a few tens of millikelvin. Our measurement of temperature dependence of the mechanical response (frequency shift and jump statistics) enables us to discern the oscillator temperature within a few tens of millikelvin down to 110 mK. At the top of the cryostat, the preamp input voltage noise of S 1=2 v 1:1 nV=Hz 1=2 translates to a noise power of P N S v BW=50 0:7 pW, in the effective bandwidth BW 30 MHz. The high frequency noise power incident on the sample is attenuated by the coaxes down to 300 fW. Even for a broadband response with a 1.5 GHz bandwidth, the noise power translates to 15 pW. In fact, the backaction noise contribution to heating (temperature increase) in our experiments is ...

Extensive studies of spin transfer and spin relaxation at a ferromagneticnonmagnetic interface 21,22,23 have shown that such a system can act as an effective source