Preparation and characterization of ZnO microcantilever for nanoactuation

Nanoscale Research Letters, Dec 2012

Zinc oxide [ZnO] thin films are deposited using a radiofrequency magnetron sputtering method under room temperature. Its crystalline quality, surface morphology, and composition purity are characterized by X-ray diffraction [XRD], atomic force microscopy [AFM], field-emission scanning electron microscopy [FE-SEM], and energy-dispersive X-ray spectroscopy [EDS]. XRD pattern of the ZnO thin film shows that it has a high c-axis-preferring orientation, which is confirmed by a FE-SEM cross-sectional image of the film. The EDS analysis indicates that only Zn and O elements are contained in the ZnO film. The AFM image shows that the film's surface is very smooth and dense, and the surface roughness is 5.899 nm. The microcantilever (Au/Ti/ZnO/Au/Ti/SiO2/Si) based on the ZnO thin film is fabricated by micromachining techniques. The dynamic characterizations of the cantilever using a laser Doppler vibrometer show that the amplitude of the cantilever tip is linear with the driving voltage, and the amplitude of this microcantilever's tip increased from 2.1 to 13.6 nm when the driving voltage increased from 0.05 to 0.3 Vrms. The calculated transverse piezoelectric constant d31 of the ZnO thin film is -3.27 pC/N. This d31 is high compared with other published results. This ZnO thin film will be used in smart slider in hard disk drives to do nanoactuation in the future.

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Preparation and characterization of ZnO microcantilever for nanoactuation

Peihong Wang 0 Hejun Du 0 Shengnan Shen 0 1 Mingsheng Zhang 1 Bo Liu 1 0 School of Mechanical and Aerospace Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore , 639798, Republic of Singapore 1 Data Storage Institute, 5 Engineering Drive 1 , Singapore , 117608, Republic of Singapore Zinc oxide [ZnO] thin films are deposited using a radiofrequency magnetron sputtering method under room temperature. Its crystalline quality, surface morphology, and composition purity are characterized by X-ray diffraction [XRD], atomic force microscopy [AFM], field-emission scanning electron microscopy [FE-SEM], and energy-dispersive X-ray spectroscopy [EDS]. XRD pattern of the ZnO thin film shows that it has a high c-axispreferring orientation, which is confirmed by a FE-SEM cross-sectional image of the film. The EDS analysis indicates that only Zn and O elements are contained in the ZnO film. The AFM image shows that the film's surface is very smooth and dense, and the surface roughness is 5.899 nm. The microcantilever (Au/Ti/ZnO/Au/Ti/SiO2/Si) based on the ZnO thin film is fabricated by micromachining techniques. The dynamic characterizations of the cantilever using a laser Doppler vibrometer show that the amplitude of the cantilever tip is linear with the driving voltage, and the amplitude of this microcantilever's tip increased from 2.1 to 13.6 nm when the driving voltage increased from 0.05 to 0.3 Vrms. The calculated transverse piezoelectric constant d31 of the ZnO thin film is -3.27 pC/N. This d31 is high compared with other published results. This ZnO thin film will be used in smart slider in hard disk drives to do nanoactuation in the future. - Introduction As the recording density of hard disk drive [HDD] further increases, the spacing between the slider and the disk decreases quickly. A 10-Tb/in2 recording density requires a 2 to 3 nm or even less of head-media spacing when HDD is working [1]. In that case, contact between slider and disk will not be avoided completely. So, it is necessary to detect the slider-disk contact and then adjust the spacing to decrease the damage to the headdisk interface. Due to quick response and contact detection ability, many piezoelectric sensors/actuators based on bulk and thin film lead zirconate titanate [PZT] have been proposed in order to solve the above problem [2,3]. However, it is hard to fabricate a bulk PZT material into a microscale dimension. Meanwhile, the deposition of PZT thin film usually requires processing at over 600C [4], which is not compatible with fabrication of magnetic heads in HDD technology. Compared to PZT material, ZnO thin film also has good piezoelectric quality, and its microfabrication does not need head process under very high temperature [5]. So, ZnO film-based piezoelectric sensors/actuators are being designed and used in smart slider to detect the head-disk contact and then adjust the flying height in our ongoing project. There were many papers about the fabrication and characterization of ZnO films in the past decades [6-8]. However, few reports presented the piezoelectric quality of ZnO film quantitatively. In this paper, a ZnO thin film for the application of nanoactuator was deposited using a radiofrequency [RF] magnetron sputtering system under room temperature and was characterized by X-ray diffraction [XRD], energy-dispersive X-ray spectroscopy [EDS], field-emission scanning electron microscopy [FESEM], and atomic force microscopy [AFM]. Moreover, a ZnO film-based piezoelectric microcantilever was fabricated by micromachining techniques. The dynamic response of the piezoelectric cantilever was measured using a laser Doppler vibrometer [LDV]. The calculation result showed that the transverse piezoelectric constant d31 of the ZnO thin film is -3.27 pC/N. This d31 is high compared with other published results. In the future, this ZnO thin film will be used in smart slider to do nanoactuation in HDDs. Experimental details ZnO thin films were deposited by RF magnetron sputtering system using a ZnO target (99.99%) with a diameter of 2 in. and a thickness of 3 mm. The substrate comprised p-type silicon (100) with a SiO2 layer and a Au/Ti seed layer. The thickness of the SiO2 layer and the Au/Ti seed layer were 1 m and 300 nm/50 nm, respectively. The chamber was down to 5 10-6 Torr using a molecular pump before introducing mixed Ar and O2 gases. In the deposition of the ZnO thin film, the RF power was 70 W, the working pressure was 0.8 Pa, the O2/(Ar + O2) gas ratio was 0.25, and the substrate temperature was at room temperature. The above deposition condition was from our previous optimization result. The corresponding deposition rate of the ZnO film was about 0.28 m/h, and the deposition time was 4.5 h. The ZnO piezoelectric microcantilever was fabricated by micromachining techniques. The substrate was (100) p-type silicon wafer on which a 1 m of silicon dioxide [SiO2] was grown using a thermal oxidation method. (...truncated)


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Peihong Wang, Hejun Du, Shengnan Shen, Mingsheng Zhang, Bo Liu. Preparation and characterization of ZnO microcantilever for nanoactuation, Nanoscale Research Letters, 2012, pp. 176, Volume 7, Issue 1, DOI: 10.1186/1556-276X-7-176