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Tuneable Q-Factor of MEMS Cantilevers with Integrated Piezoelectric Thin Films
摘要： In atomic force microscopes (AFM) a resonantly excited, micro-machined cantilever with a tip is used for sensing surface-related properties. When targeting the integration of AFMs into vacuum environments (e.g., for enhancing the performance of scanning electron microscopes), a tuneable Q-factor of the resonating AFM cantilever is a key feature to enable high speed measurements with high local resolution. To achieve this goal, in this study an additional mechanical stimulus is applied to the cantilever with respect to the stimulus provided by the macroscopic piezoelectric actuator. This additional stimulus is generated by an aluminum nitride piezoelectric thin film actuator integrated on the cantilever, which is driven by a phase shifted excitation. The Q-factor is determined electrically by the piezoelectric layer in a Wheatstone bridge configuration and optically verified in parallel with a laser Doppler vibrometer. Depending on the measurement technique, the Q-factor is reduced by a factor of about 1.9 (electrically) and 1.6 (optically), thus enabling the damping of MEMS structures with a straight-forward and cheap electronic approach.
关键词： phase shifted excitation,vacuum,electronically tuneable Q-factor,AFM,MEMS cantilever,AlN,piezoelectric,peak shaping
更新于2025-09-09 09:28:46
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Materials Science and Technology of Optical Fabrication || Novel Process and Characterization Techniques
摘要： There are many conventional optical-fabrication process and characterization techniques, and they are well documented in the literature [1, 2]. These include the following: ? Interferometry techniques and test plating to measure surface ?gure, wedge, and parallelism ? Needle pro?lometry, white-light interferometry, and atomic force microscopy (AFM) to measure surface roughness ? Optical, confocal, and dark-?eld microscopy and visual inspection to measure surface quality ? Baume density ?oats, pH sensors, and particle-size analyzers to characterize polishing slurries ? Hardness testers to characterize lap materials, particularly pitch In this chapter, some novel techniques (and perhaps obscure techniques) that provide additional insight into the optical-fabrication process are described. Chapters 2–5 focused on the phenomena that govern the basic properties of a workpiece during and after optical fabrication, namely surface ?gure, surface quality, surface roughness, and material removal rate. The novel process and characterization techniques explored in this chapter are described for an optical-fabrication engineer or an optician who might wish to use them.
关键词： optical-fabrication,AFM,interferometry,characterization techniques,polishing slurries
更新于2025-09-09 09:28:46
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Influence of 120 MeV S9+ ion irradiation on structural, optical and morphological properties of zirconium oxide thin films deposited by RF sputtering
摘要： The calibrated and controlled swift heavy ions (SHI) beam irradiation generates defects which can cause modifications in various properties of the materials such as structural, optical, magnetic, morphological, and chemical etc. The passage of ion through the target material causes the nuclear energy losses (Sn) and electronic energy losses (Se). The Se dominates over Sn in SHI irradiation. In the present study, ZrO2 thin films were grown on silicon and glass substrate by using RF sputtering deposition technique. For the purpose of modifications induced by swift heavy ions, these films were irradiated by a 120 MeV S9+ ion beam of 1 pnA current, with varying ion fluences from 5E12 to 1E13 ions/cm2, using the tandem accelerator at the Inter University Accelerator Center (IUAC), New Delhi, India. The X-ray diffraction (XRD) patterns confirmed the formation of monoclinic and tetragonal phases and it was observed that XRD peak intensities increased up to the fluence of 5E12 ions/cm2 followed by opposite behavior at higher fluences. Atomic force microscope (AFM) study revealed the increased surface roughness after SHI irradiation. In addition to it, the formation of electronic transition states in optical band gap region and enhancement of absorption edge was observed from UV- visible spectroscopy (UV-Vis) results due to which direct band gap energy value decreased from those of un-irradiated samples. Photoluminescence (PL) broad emission spectra were determined using the excitation wavelength at 290 nm with the prominent peak at 415 nm which can be ascribed to Zr vacancies due to band edge emission as a result of free- exciton recombination. Rutherford backscattering spectrometry (RBS) technique was used for depth profiling and elemental composition in zirconia thin films. The expected role of electronic energy loss during ion irradiation to modify the properties of the material has been discussed.
关键词： PL,ZrO2 thin films,XRD,UV-Vis,AFM,RBS,SHI irradiation
更新于2025-09-09 09:28:46
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Dynamical modeling of manipulation process in Trolling-Mode AFM
摘要： Dynamical lumped modeling of Trolling-mode AFM in manipulation of bio-samples is presented. The combination of high accuracy and compatibility with physiological conditions makes AFM a unique tool for studying biological materials in liquid medium. However, AFM microcantilever suffers from severe sensitivity degradation and noise intensification while operating in liquid; the large hydrodynamic drag between the cantilever and the surrounding liquid overwhelms the tip-sample interaction forces that are important in controlling the process. Therefore, an appropriate nanoneedle should be long enough to keep the cantilever out of liquid medium and short enough to be able to transmit the required force to push nanoparticle. Nonetheless, a long nanoneedle may deflect under the pushing force; therefore, its bending deflection should be accounted for in governing equations. Moreover, analytical and finite element stress analysis of nanoneedle and cantilever is performed to assure about their selected material and geometry. JKR theory is utilized to model contact mechanics between the needle/surface and the particle. Drag and meniscus forces are used to model the liquid media. Governing equations are solved using ODE45 and the system behavior is simulated. Critical conditions of sliding including critical time and force are obtained and changes of pushing force, needle deflection and indentation depths are illustrated. Also, effects of velocity variations are observed. Then, different heights for nanoneedle are tested and an appropriate one is selected for our purpose (to keep the needle out of liquid and transmit the force appropriately). The simulation is repeated for various biological particles and their behaviors are studied. At the end, the present simulation is validated through comparing the results with a previous work. This comparison shows that the simulation is reliable for the intended purpose.
关键词： Trolling-Mode AFM,Lumped model,Liquid environment,Manipulation
更新于2025-09-09 09:28:46
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Customized MFM probes with high lateral resolution
摘要： Magnetic force microscopy (MFM) is a widely used technique for magnetic imaging. Besides its advantages such as the high spatial resolution and the easy use in the characterization of relevant applied materials, the main handicaps of the technique are the lack of control over the tip stray field and poor lateral resolution when working under standard conditions. In this work, we present a convenient route to prepare high-performance MFM probes with sub-10 nm (sub-25 nm) topographic (magnetic) lateral resolution by following an easy and quick low-cost approach. This allows one to not only customize the tip stray field, avoiding tip-induced changes in the sample magnetization, but also to optimize MFM imaging in vacuum (or liquid media) by choosing tips mounted on hard (or soft) cantilevers, a technology that is currently not available on the market.
关键词： magnetic materials,AFM probes,high-resolution microscopy,atomic force microscopy (AFM),magnetic force microscopy (MFM)
更新于2025-09-04 15:30:14
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Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement
摘要： Self-sensing techniques for atomic force microscope (AFM) cantilevers have several advantageous characteristics compared to the optical beam deflection method. The possibility of down scaling, parallelization of cantilever arrays and the absence of optical interference associated imaging artifacts have led to an increased research interest in these methods. However, for multifrequency AFM, the optimization of the transducer layout on the cantilever for higher order modes has not been addressed. To fully utilize an integrated piezoelectric transducer, this work alters the layout of the piezoelectric layer to maximize both the deflection of the cantilever and measured piezoelectric charge response for a given mode with respect to the spatial distribution of the strain. On a prototype cantilever design, significant increases in actuator and sensor sensitivities were achieved for the first four modes without any substantial increase in sensor noise. The transduction mechanism is specifically targeted at multifrequency AFM and has the potential to provide higher resolution imaging on higher order modes.
关键词： multimodal AFM,atomic force microscopy,multifrequency AFM,self-sensing,piezoelectric cantilever
更新于2025-09-04 15:30:14
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Preparation, characterization and electrical behaviors of PEDOT:PSS-Au/Ag nanocomposite thin films: an ecofriendly approach
摘要： Structure, morphology and electrical behaviors of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) or PEDOT:PSS thin films are investigated in the presence of protein-mediated green chemically synthesized positively charged gold and silver nanoparticles. The pure and PEDOT:PSS nanocomposite thin films are prepared by spin coating method. The presence of both nanoparticle and polymer is confirmed from X-ray diffraction, whereas composite formation is confirmed from Raman and FTIR spectroscopy. Atomic force microscopy (AFM) images show the surface morphologies of both pure and composite films, whereas average film thicknesses are obtained from AFM and X-ray reflectivity analysis. The presence of electrostatic interaction between the positively charged metallic nanoparticles and negatively charged PSS chains leads to the electrostatic shielding between cationic PEDOT and anionic PSS, which favors better charge transfer through PEDOT–PEDOT conducting paths. The increase in electrical conductivity is visualized from the current–voltage (I–V) curves, which show that the conductivity is relatively higher in the presence of silver than gold nanoparticles in the composite thin films. The conductivity of nanocomposite films is approximately five to six times enhanced in comparison with the pristine PEDOT:PSS thin films.
关键词： FTIR spectroscopy,PEDOT:PSS-Au/Ag thin films,AFM,UV–Vis,Nanocomposites,Conductivity
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - Kuala Lumpur (2018.8.15-2018.8.17)] 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - A Study on the Atomic Topography of Nanostructured TiO<inf>2</inf>Thin Films: Effect of Annealing
摘要： Titanium dioxide (TiO2) is one of the most investigated metal oxides due to the wide range of applications such as photocatalysts. Photocatalytic activity will increased when the surface area is higher. Hence, this research focus on the surface topography and roughness of nanostructured TiO2 films characterized by atomic force microscopy (AFM) in order to obtain thin films with the optimum roughness for photocatalytic activity. TiO2 thin films were prepared by spin coating method at room temperature. The TiO2 solutions of 0.1 - 0.2 M were synthesized from titanium butoxide in ethanol. TiO2 films were deposited on the silicon substrates and annealed at 450°C. The results shown when the film was annealed, the grain were clearly observed. The grain size and the roughness increased when the film were annealed at high temperature. 0.2 M of TiO2 thin film exhibit the higher roughness with Ra and RMS values were 51.29 and 78.90 nm, respectively.
关键词： Molarity,Roughness,TiO2,Topography,AFM
更新于2025-09-04 15:30:14
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Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds
摘要： Herein, we present the formation of gold nanorods (GNRs) on novel gold–poly(methyl methacrylate) (Au–PMMA) nanocomposite substrates with unprecedented growth control through the polymer molecular weight (Mw) and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au–PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer Mw and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower Mw PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method.
关键词： direct surface growth,gold nanorods,nanocomposites,atomic force microscopy (AFM),poly(methyl methacrylate) (PMMA)
更新于2025-09-04 15:30:14
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Investigation of structural, optical and morphological properties of InGaN/GaN structure
摘要： In this study, InGaN/GaN structure is investigated in the temperature range of 300–500?°C with steps of 50?°C. InGaN/GaN multi-quantum well structure is deposited on c-orientated sapphire wafer by metal organic chemical vapour deposition method. All the parameters except for temperature kept constant during growth period. InGaN/GaN structures with different In content are investigated by XRD technique. Their structural, optical and morphological characteristics are determined by high resolution X-ray diffraction, Fourier transform spectroscopy (FTIR), photo luminescence (PL), transmission and atomic force microscopy (AFM). According to FTIR and PL spectra’s, it is noticed that band gap values coincide with blue region in the electromagnetic spectrum. As a result of transmission measurements it is seen that light is completely absorbed by the sample at approximately 390?nm. Using XRD technique, dislocation densities and strain are calculated. Full width at half maximum of the XRD peak values gained from X-ray diffraction are used in an alternative method called William-son–Hall (W–H). Using W–H method, lateral and vertical crystal lengths and tilt angles are determined. Surface roughness parameters are investigated by AFM. Different properties of GaN and InGaN layers are compared as dependent on increasing temperature. According to AFM images it is seen that these structures have high surface roughness and large crystal size. All the results yielded from the mentioned methods are in good agreement with the previous works done by different authors.
关键词： FTIR,MOCVD,XRD,AFM,PL,InGaN/GaN
更新于2025-09-04 15:30:14