Acoustic investigation of the elastic properties of ZnO films

Carlotti, G.; Socino, G.; Petri, Alberto; Verona, É.

doi:10.1063/1.98502

Cited by 126 publications

(47 citation statements)

References 7 publications

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“…Using this technique, the estimated direct piezoelectric constant was e 31 =.0377 C/m 2 . This was about an order of magnitude smaller than that reported in the literature [13,14].…”

Section: Zno Film Characterizationcontrasting

confidence: 50%

Strain Sensing With Piezoelectric Zinc Oxide Thin Films for Vibration Suppression in Hard Disk Drives

Felix

Kon

Nie

et al. 2008

ASME 2008 Dynamic Systems and Control Conference, Parts a and B

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This paper describes the integration of thin film ZnO strain sensors onto hard disk drive suspensions for improved vibration suppression for tracking control. Sensor location was designed using an efficient optimization methodology based on linear quadratic gaussian (LQG) control. Sensors were fabricated directly onto steel wafers that were subsequently made into instrumented suspensions. Prototype instrumented suspensions were installed into commercial hard drives and tested. For the first time, a sensing signal was successfully obtained while the suspension was flying on a disk as in normal drive operation. Preliminary models were identified from experimental transfer functions. Nominal H 2 control simulations demonstrated improved vibration suppression as a result of both the better resolution and higher sensing rate provided by the sensors.

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“…Using this technique, the estimated direct piezoelectric constant was e 31 =.0377 C/m 2 . This was about an order of magnitude smaller than that reported in the literature [13,14].…”

Section: Zno Film Characterizationcontrasting

confidence: 50%

Strain Sensing With Piezoelectric Zinc Oxide Thin Films for Vibration Suppression in Hard Disk Drives

Felix

Kon

Nie

et al. 2008

ASME 2008 Dynamic Systems and Control Conference, Parts a and B

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“…From a theoretical perspective point of view, we believe that this effect can also contribute to the larger piezoelectric coefficients measured in ZnO NWs [21] compared to those of ZnO thin films. [45] Indeed, in addition to possible nonlinear effects which are more likely to be present in thin NWs, [46] part of the improvement could be associated to the surface depletion effects enlightened in this paper. From an application point of view, an additional advantage is that the response of such a NW-based composite can be improved by increasing NW length while increasing a thin film thickness would be ineffective.…”

Section: Comparison With a Zno Thin Filmmentioning

confidence: 99%

Unveiling the Influence of Surface Fermi Level Pinning on the Piezoelectric Response of Semiconducting Nanowires

Tao

Mouis

Ardila

2017

Adv Elect Materials

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environment ever since they were first demonstrated. [4] Experimentally, it has been proved that ZnO NW based piezoelectric devices can generate a potential of a few volts. [15] This can be retrieved theoretically as long as there are no free carriers. However, experimentally prepared ZnO NWs are spontaneously n-type doped by impurities during their synthesis [16,17] and in such a case, screening by free carriers is expected to reduce drastically the piezoelectric response. There remain many such contradictions between experimental results and the present theoretical understanding of ZnO NW-based devices when realistic doping levels are considered. Chief among them are (1) decent and length-dependent performance of ZnO NWs, [18] while anticipations based on analytical and computational study showed that the output of NWs under compression were reduced to a few millivolts and presenting length-independent performance due to the screening effect; [19,20] (2) enhanced piezoelectric coefficients, [21] which were measured for ZnO NWs with diameter beyond the size effects anticipated by ab initio method; [22] and (3) dissymmetric piezoelectric response of bent nanogenerators (NGs) under tensile and compressive strain. [23] Relatively high potentials (>0.2 V) can be repeatedly obtained from NGs integrating long and large ZnO NWs [24][25][26][27] with presumably nonintentional doping. Increasing the doping concentration will reduce the generated piezopotential. [28] The nature of matrix material, as well as processing conditions, has been shown to play an important role. [24] (Table S1, Supporting Information).In this paper, we solve these contradictions by accounting for surface Fermi level pinning (SFLP). This effect commonly exists at the surface of III-V and II-VI semiconductor compounds. [29][30][31] At the surface of n-type ZnO NWs, oxygen molecules get negatively charged by capturing the free electrons from NW core. This forms a low-conductivity depletion layer near the surface, where the screening of piezoelectric potential by free carriers effect is suppressed. [30,[32][33][34][35][36] This effect has been used to neglect free carriers in most simulation studies dealing with the piezoelectric response of semiconducting nanowirebased devices. A few papers have accounted for free carriers, although without account for SFLP. [20,37] Here instead, full coupling between piezoelectric effect and semiconducting physics, including free carriers and SFLP, was considered.ZnO nanowires (NWs) are excellent candidates for the integration of energy harvesters, mechanical sensors, piezotronic and piezophototronic devices. However, ZnO NWs are usually nonintentionally n-doped during their growth. Thus, it can be expected theoretically that their piezoelectric response be degraded and mostly geometry-independent as a result of strong screening effects by free carriers, while experimentally many NW-based piezoelectric transducers demonstrate quite reasonable performance. In this paper, this apparent contradiction is explained by...

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“…Owing to their high conductivity and transparency in the visible wavelength region, they have been used in optical and electronic devices such as surface acoustic wave devices (SAW), display panels, solar cells, and ultraviolet (UV) light emitting diodes [1][2][3][4][5][6]. Indium tin oxide (ITO) is used for most of the TCO applications [7].…”

Section: Introductionmentioning

confidence: 99%