Electromechanical conversion efficiency of GaN NWs: critical influence of the NW stiffness, the Schottky nano-contact and the surface charge effects

Gogneau, N.; Chrétien, Pascal; Sodhi, Tanbir; Couraud, Laurent; Leroy, L.; Travers, Laurent; Harmand, Jean-Chistophe; Julien, F. H.; Tchernycheva, Maria; Houzé, Frédéric

doi:10.1039/d1nr07863a

Cited by 6 publications

(14 citation statements)

References 63 publications

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“…In contrast, no clear trend was observed as the seed layer deposition temperature was modified. Our results confirm the trend found in recent works[27,29] where a smaller NW radius led to a larger piezoresponse. However, since PFM characterizes the converse piezoelectric effect instead of the direct piezoelectric effect, there was no intentional force applied on the NWs in this mode.…”

supporting

confidence: 93%

“…However, since PFM characterizes the converse piezoelectric effect instead of the direct piezoelectric effect, there was no intentional force applied on the NWs in this mode. Therefore there was no need for a PMMA matrix to mechanically consolidate the NWs which were not prompt to parasitic flexion by contrast with previous work [29].…”

Section: Resultsmentioning

confidence: 77%

“…Piezoresponse force microscopy (PFM) is the perfect tool to probe the converse piezoelectric effect on individual NWs [25][26][27][28], but no study of the effect of the NWs dimensions has been reported with this technique. Up to now, the most convincing results about the influence of NW diameter on the piezoelectric response of individual NWs have been obtained very recently by probing the direct piezoelectric effect of GaN NWs under constant normal force [29]. Despite the consolidating PMMA matrix, the thinnest NWs were highly strained, with buckling and twinning/ twisting effects leading to complex strain and polarization fields.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the diameter-dependent piezoelectric response of semiconducting ZnO nanowires by Piezoresponse Force Microscopy and FEM simulations

et al. 2023

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Semiconducting piezoelectric nanowires (NWs) are promising candidates to develop highly efficient mechanical energy transducers made of biocompatible and non-critical materials. The increasing interest in mechanical energy harvesting makes the investigation of the competition between piezoelectricity, free carrier screening and depletion in semiconducting NWs essential. To date, this topic has scarcely been investigated because of the experimental challenges raised by the characterization of the direct piezoelectric effect in these nanostructures. Here we get rid of these limitations using the PFM technique in DataCube mode and measuring the effective piezoelectric coefficient through the converse piezoelectric effect. We demonstrate a sharp increase in the effective piezoelectric coefficient of vertically aligned ZnO NWs as their radius decreases. We also present a numerical model that quantitatively explains this behavior by taking into account both the dopants and the surface traps. These results have a strong impact on the characterization and optimization of mechanical energy transducers based on vertically aligned semiconducting NWs.

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supporting

confidence: 93%

Section: Resultsmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

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Investigation of the diameter-dependent piezoelectric response of semiconducting ZnO nanowires by Piezoresponse Force Microscopy and FEM simulations

et al. 2023

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“…Experimentally, beyond literature surveys which can only provide indirect and qualitative clues due to the large number of interfering parameters, the influence of geometry on NW piezoresponse has only started to be examined quantitatively. In a recent paper [24], vertical GaN NWs with light P-doping, sub-100 nm diameters and about 1 µm length have been grown by PA-MBE and their piezoelectric properties tested at nanoscale by measuring simultaneously the open circuit voltage V OC and the deformation under controlled vertical force. Results corresponding to purely axial compression have been obtained with the 'rigid NWs' population.…”

Section: Introductionmentioning

confidence: 99%

Length and polarity dependent saturation of the electromechanical response of piezoelectric semiconducting nanowires

Garcia

Mouis

Jalabert

et al. 2023

J. Phys. D: Appl. Phys.

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The question of the length dependence of the electromechanical response of semiconducting piezoelectric NWs was explored. We identified a new physical mechanism of piezoresponse saturation, which originates from the combination of the influence of interface traps and piezoelectric polarization in the depleted NW. Our results are in better qualitative agreement with experimental observations than presently existing theories. To do so, we used the Finite Element Method to simulate the coupled set of equations describing mechanical, piezoelectric and semiconducting properties. In order to reduce the number of parameters, simulations focused on the case of uniform ZnO nanowires grown along the c-axis. Saturation was explained by the incapacity of surface traps to maintain depletion along the whole NW beyond a certain length, as a result of the electric potential shift induced by piezoelectric polarization. An analytical model was developed to support this analysis. It provided the dependence trends of saturation length and piezoresponse as a function of NW dimensions, doping level, surface traps density and crystal polarity, as well as with external pressure, in fair agreement with simulation results. Moreover, we discovered that one consequence of this mechanism was that crystal polarity had an impact on the smoothness of the radius-dependent transition between high and low piezoresponse under axial stress. These results have important implications for the optimization of electromechanical sensors and nanogenerators based on piezoelectric semiconducting NWs and related composite materials.

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“…However, this can impose a limitation to reduce the NW diameter if the radial etching step also leads to some axial etching. Long NWs with high aspect ratios are required for flexible electronics or energy conversion devices, for instance. Diameter and aspect ratio are also important in NW photonic devices: To exploit the advantages of the NW geometry, the diameter of the objects must be shorter than the wavelength of the interacting photons, , and the NW diameter is critical to obtain linear devices. , …”

Section: Introductionmentioning

confidence: 99%

High-Aspect-Ratio GaN p–i–n Nanowires for Linear UV Photodetectors

da Silva,

Biegański,

Durand

et al. 2023

ACS Appl. Nano Mater.

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Ultraviolet GaN photodetectors based on nanowires (NWs) fabricated by top-down strategies promise improved uniformity, morphology, and doping control with respect to bottom-up ones. However, exploiting the advantages of the NW geometry requires sub-wavelength NW diameters. We present fabrication of large-area sub-200 nm diameter top-down GaN p–i–n NW ultraviolet photodetectors with lengths over 2 μm produced from a planar specimen using nanosphere lithography, followed by a combination of dry and crystallographic-selective wet etching. Photocurrent measurements in single-NW devices under bias show a linear response as a function of the optical power, with increased current levels under reverse bias. The linearity proves that the drift of photogenerated carriers at the junction is the dominating photodetection mechanism, with negligible contributions from surface effects. These results demonstrate that the unique properties of NW-based photodetectors can be assessed through a scalable and low-cost fabrication process.

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Electromechanical conversion efficiency of GaN NWs: critical influence of the NW stiffness, the Schottky nano-contact and the surface charge effects

Abstract: The GaN piezoelectric nanowires (NWs) are considered as promising nanomaterials to develop high-efficient piezoelectric generators.

Cited by 6 publications

References 63 publications

Investigation of the diameter-dependent piezoelectric response of semiconducting ZnO nanowires by Piezoresponse Force Microscopy and FEM simulations

Investigation of the diameter-dependent piezoelectric response of semiconducting ZnO nanowires by Piezoresponse Force Microscopy and FEM simulations

Length and polarity dependent saturation of the electromechanical response of piezoelectric semiconducting nanowires

High-Aspect-Ratio GaN p–i–n Nanowires for Linear UV Photodetectors

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