Theory of potential modulation in lateral surface superlattices

Davies, John H.; Larkin, I. A.

doi:10.1103/physrevb.49.4800

Cited by 123 publications

(83 citation statements)

References 32 publications

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“…We neglect the small bending in electrostatic calculations, but save the bound charge determined by (16) and (17) at 0 ≤ l ≤ L and put it zero otherwise. Using these simplifications, we can estimate the screening charge density using the method of images as follows:…”

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confidence: 99%

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Piezoelectric Electromechanical Coupling in Nanomechanical Resonators with a Two-Dimensional Electron Gas

et al. 2016

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The electrical response of two-dimensional electron gas to vibrations of a nanomechanical cantilever containing it is studied. Vibrations of perpendicularly oriented cantilevers are experimentally shown to change oppositely the conductivity near their bases. This indicates the piezoelectric nature of electromechanical coupling. A physical model is developed, which quantitatively explains the experiment. It shows that the main origin of the conductivity change is a rapid change in the mechanical stress on the boundary between suspended and non-suspended areas, rather than the stress itself.PACS numbers: 85.85.+j, 73.50.Dn, 77.65.Ly Most of the currently studied low-dimensional electron systems are fabricated from a two-dimensional electron gas (2DEG) embedded in a semiconductor bulk. A classical example of such a system is a 2DEG in GaAs/AlGaAs heterostructures. However, selective etching of a sacrificial layer (often called surface nanomachining) gives an opportunity to create also a 2DEG embedded in a thin membrane freely suspended over a substrate [1]. The nanostructures fabricated from such membranes are mechanically moveable with their movement affecting electron transport and conductivity [2]. Such electromechanical coupling gives an opportunity to probe mechanical motion at the nano-scale and it could be used to study various interesting mechanical phenomena, such as "phonon lasing" [3] and the quantum-limited motion of an artificially made object [4]. Moreover, it opens up new prospects for studying non-trivial transport phenomena in 2DEG under unusual conditions, namely, in the presence of additional mechanical degrees of freedom, and for creating nanoelectromechanical systems (NEMS). For example, papers [5,6] show that the electron transport through a quantum point contact placed on a micromechanical resonator is sensitive to mechanical vibrations. Papers [2,7,8] demonstrate that diffusive conductive channels in 2DEG can also be used as nanoelectromechanical transducers.The two fundamental key points arising in the context of NEMS are the physical mechanisms underlying actuation and transduction of the nanomechanical motion. The question about the actuation in NEMS with 2DEG is addressed elsewhere [7], while, in the present paper, we focus on the transduction mechanism. Most of the papers considering GaAs/AlGaAs-based suspended systems contain a proposal that a 2DEG embedded in a resonator is sensitive to its vibrations due to the change in the density of a 2DEG that screens the piezoelectrically induced bound charge [2,5,6,9]. However, there is a lack of experimental evidence for this hypothesis.In the present paper, we experimentally demonstrate that the dominant physical mechanism making a 2DEG sensitive to NEMS mechanical vibrations is associated with the piezoelectric effect and show the sensitivity magnitude. We propose also a physical model giving an independent estimate for the value of electron density change consistent with the experiment. According to the model, the local change in the 2DE...

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confidence: 99%

“…To estimate δn, we neglect the last term in (18), use the model of pure electrostatic screening [16] and consider the 2DEG as having constant electrical potential δφ ext + δφ resp = 0. This assumption is reasonable if…”

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Piezoelectric Electromechanical Coupling in Nanomechanical Resonators with a Two-Dimensional Electron Gas

et al. 2016

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“…When the cantilever bends, the 2DEG density changes in such a way as to maintain constant electrochemical potential. However, to simplify the calculations, we use the pure electrostatic screening model (Davies and Larkin, 1994) and consider the 2DEG as a media having a constant electrical potential. As shown in Shevyrin et al (2016), this simplification is reasonable if the cantilever thickness far exceeds the Bohr radius a B = 4π 0 2 m −1 e −2 ≈ 13 nm (here m is an electron effective mass and e is the elementary charge).…”

Section: Model Descriptionmentioning

confidence: 99%

A two-dimensional electron gas sensing motion of a nanomechanical cantilever

Shevyrin

Pogosov

2017

Mech. Sci.

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Abstract.A quantitative physical model, describing the piezoelectric electromechanical coupling in nanomechanical resonators with a two-dimensional electron gas, is developed. Numerical calculations of the change in density of a two-dimensional electron gas contained in a vibrating cantilever are performed using the model and are shown to be consistent with the experiment. The obtained data show that the vibration-induced electron density modulation is localized near the clamping point and that it is related to a rapid spatial change in the mechanical stress near this point. It is shown that details of the clamping geometry significantly affect the magnitude of the effect.

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“…Typically, at helium temperatures, they have electron densities of 3 to 5 x 10 15 m-2 , mobilities of 60 to 80 m 2 V-1 s-1 , and electron mean free paths of 6 to 8 m. The 2DEG is formed at a (AlGa)As/GaAs heterointerface 35 nm to 50 nm beneath the surface of the heterostructure. When ferromagnetic stripes and gratings are used they are orientated normal to the [100] GaAs crystal direction, which is non-piezoelectric, to minimise any strain-induced electric modulation at the 2DEG due to the differential thermal contraction of the ferromagnet and the GaAs [24]. We will consider the 2DEG to lie in the x-y plane and the current to flow in the x-direction.…”

Section: Hybrid Ferromagnetic/semiconductor Devicesmentioning

confidence: 99%