SNOM/AFM microprobe integrated with piezoresistive cantilever beam for multifunctional surface analysis (original) (raw)
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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2004
In scanning near field optical microscope ͑SNOM͒, an optical probe with aperture diameter well below the optical wavelength is moved over the sample. The sample-probe distance control is one of the key problems in SNOM. Our earlier approach allowed for fabrication of the piezo-SNOM/ atomic force microscopy ͑AFM͒ probe, however, reproductivity of the process and optical quality of the device were not satisfactory. Now we report an innovative processing sequence, which offers highly reproductive batch processing, typical for semiconductor technology and renders it possible to produce cantilevers playing role of an AFM detector as well as a nanoaperture detector. Moreover, illumination of the aperture is easier because of a wide input opening and its big cone angle. The throughput is in the range of 10 Ϫ5 and higher. Apertures in hollow pyramids have been formed by direct ion beam drilling with a focused beam of 30 keV Ga ϩ ions. Direct focused ion beam ͑FIB͒ drilling is a reproducible process for hole formation at the 30-100 nm diameter range. Formation of smaller apertures is possible if a special FIB drilling/deposition procedure is applied.
Opto-mechanical probe for combining atomic force microscopy and optical near-field surface analysis
Optics letters, 2014
We have developed a new easy-to-use probe that can be used to combine atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). We show that, using this device, the evanescent field, obtained by total internal reflection conditions in a prism, can be visualized by approaching the surface with the scanning tip. Furthermore, we were able to obtain simultaneous AFM and SNOM images of a standard test grating in air and in liquid. The lateral resolution in AFM and SNOM mode was estimated to be 45 and 160 nm, respectively. This new probe overcomes a number of limitations that commercial probes have, while yielding the same resolution.
A novel piezoresistive microprobe for atomic and lateral force microscopy
Sensors and Actuators A: Physical, 2005
In this article, we present the development of a novel probe for atomic force and lateral force microscopy, based on detailed finiteelements method (FEM) simulation. The FEM simulation is performed by means of the ANSYS 5.3 code. The developed probe consists of a micromachined silicon cantilever beam with an integrated micro-tip and piezoresistive sensors for detecting the lateral and vertical forces acting on the tip. The sensitivity for vertical displacement detection of 1.26 V/nm (for 1 k piezoresistor) and for lateral displacement detection of 0.46 V/nm (for 0.7 k resistors), by 0.6 V applied supply voltage was obtained. The principle of the probe, theoretical analysis, and experimental investigation of the probe sensor are discussed. The probe is suitable for operating in contact and noncontact atomic force microscopy (AFM) mode. The probe was utilized for imaging the surface of a chromium/quartz structure.
Scanning proximity probes for nanoscience and nanofabrication
Microelectronic Engineering, 2006
The AFM-technology has undergone tremendous development during the past decade. This review is devoted to the realization of piezoresistive sensors used in scanning probe microscopy at University of Kassel. It is expected that in the near future major technological breakthroughs in scanning proximal probe nanotools will allow for key scientific impact on analysis and synthesis of nanostructures. All the piezoresistive cantilever sensors described here are based on advanced silicon micromachining and standard CMOS processing. Moreover, using a newly optimized piezoresistive detection scheme process comprising a Wheatstone bridge, we have designed and fabricated piezoresistive cantilevers for atomic force microscopy, which improve surface topography resolution by an order of magnitude to 0.1 nm. The elegance of this concept is that by using an almost identical detection principle and differently functionalized tips or cantilever surfaces, we can detect subtle sample interactions (mechanical, electrical, thermal, and chemical) with a significantly more compact system than with optical beam deflection techniques. For non-contact scanning force microscopy, we integrate a thermally driven bimorph actuator with the piezoresistive cantilever and make use of direct-oscillation in a higher flexural mode. The cantilever then operates in the phase shift atomic force microscopy (AFM) detection technique.
Contact atomic force microscopy using piezoresistive cantilevers in load force modulation mode
Ultramicroscopy, 2018
Scanning probe microscopy (SPM) encompasses several techniques for imaging of the physical and chemical material properties at nanoscale. The scanning process is based on the detection of the deflection of the cantilever, which is caused by near field interactions, while the tip runs over the sample's surface. The variety of deflection detection methods including optical, piezoresistive, piezoelectric technologies has been developed and applied depending on the measurement mode and measurement environment. There are many advantages (compactness, vacuum compatibility, etc.) of the piezoresistive detection method, which makes it very attractive for almost all SPM experiments. Due to the technological limitations the stiffness of the piezoresistive beams is usually higher than the stiffness of the cantilever detected using optical methods. This is the basic constraint for the application of the piezoresistive beams in contact mode (CM) atomic force microscopy (AFM) investigations performed at low load forces (usually less than 20 nN). Drift of the deflection signal, which is related to thermal fluctuations of the measurement setup, causes that the microscope controller compensates the fluctuations instead of compensating the strength of tip-surface interactions. Therefore, it is quite difficult to keep near field interaction precisely at the setpoint level during the whole scanning process. This can lead to either damage of the cantilever's tip and material surface or loosing the contact with the investigated sample and making the measurement unreliable. For these reasons, load force modulation (LoFM) scanning mode, in which the interaction at the tip is precisely controlled at every point of the sample surface, is proposed to enable precise AFM surface investigations using the piezoresistive cantilevers. In this article we describe the developed measurement algorithm as well as proposed and introduced hardware and software solutions. The results of the experiments confirm strong reduction of the AFM entire setup drift. The results demonstrating contactless tip lateral movements are presented. It is common knowledge that such a scanning reduces tip wear.
Multi-Probe Atomic Force Microscopy Using Piezoelectric Cantilevers
Japanese Journal of Applied Physics, 2007
We developed a multi-probe atomic force microscopy (MP-AFM) system using piezo-resistive cantilevers. The use of piezo-resistive self-sensing cantilevers with deflection sensors as probes markedly reduced complexity in the ordinary AFM setup. Simultaneous observation images can be acquired by the MP-AFM under frequency modulation (FM) detection operations. The minimum distance between these probes was 6.9 µm using the piezoresistive cantilevers fabricated by a focused ion beam. Furthermore, we found that the nanoscale interaction between the probes was detected by determining the change in the amplitude of each cantilever. It was clarified that the interaction effect depended on the vibration amplitude of the cantilever-probe.
Review of Scientific Instruments, 2010
We describe in detail how atomic force microscopy ͑AFM͒ images can be routinely achieved with macroscopic silicon-based chips integrating mesoscopic tips, paving the way for the development of new near field devices combining AFM imaging with any kind of functionality integrated on a chip. The chips have been glued at the end of the free prong of 100 kHz quartz tuning forks mounted in Qplus configuration. Numerical simulations by modal analysis have been carried out to clarify the nature of the vibration modes observed in the experimental spectra. It is shown that two low frequency modes can be used to drive the system and scan the surface with a great stability in amplitude modulation as well as in frequency modulation AFM under ultrahigh vacuum. The AFM capabilities are demonstrated through a series of examples including phase and dissipation contrast imaging, force spectroscopy measurements, and investigations of soft samples in weak interaction with the substrate. The lateral resolution with the tips grown by focused ion beam deposition already matches the one achieved in standard amplitude modulation mode AFM experiments. Hayton et al. Rev. Sci. Instrum. 81, 093707 ͑2010͒ 093707-3 Hayton et al. Rev. Sci. Instrum. 81, 093707 ͑2010͒ 093707-4 Hayton et al. Rev. Sci. Instrum. 81, 093707 ͑2010͒ 093707-5 Hayton et al. Rev. Sci. Instrum. 81, 093707 ͑2010͒
Surface and Interface Analysis, 2001
We present a non-optical shear force method to control the probe-sample distance for scanning near-field optical microscopy (SNOM). In this system, the detection of shear force is accomplished by attaching a tapered fibre-optic probe to a piezoelectric bimorph cantilever, which realizes the excitation and the detection simultaneously. The decrease in amplitude of the cantilever is observed when the probe approaches the sample and the shifts in resonance frequency are measured as a function of set-point. The shear force images can be obtained reliably because the set-point is >0.8. These results suggest that the system is reasonably sensitive to shear force and can be used easily for SNOM.
Sensors and Actuators A: Physical, 2000
We have developed a new generic platform for the fabrication of multipurpose microprobes with integrated piezoresistive read-out, built-in background filter and silicon tip. The probe fabrication is based on SOI wafers with buried boron etch-stop layers, which allow us to realize probes with fully encapsulated resistors and integrated silicon tips. The dimensions of the resistors are well defined and leak-current is eliminated. Probes with a force constant in the range of 0.8-4 Nrm and with resonant frequencies in the range of 40-80 y1 y7˚y1 Ž. kHz have been fabricated. The probes typically display a deflection sensitivity of D RrR z s 2.4 = 10 A , and a force sensitivity Ž. y1 y6 y1 D RrR F s 2.7 = 10 nN. The change in resistance of the piezoresistors is detected by a highly symmetrical on-chip Wheatstone bridge arrangement. The measured noise level in the Wheatstone bridge is in good agreement with the calculated noise limit and å minimum detectable cantilever deflection of 0.3 A has been predicted for a measurement bandwidth of 10 Hz. The symmetrical bridge configuration has been compared with a nonsymmetrical setup, and it is concluded that the symmetrical Wheatstone bridge significantly Ž. decreases nonlinearities in the output response. Finally, the probe has successfully been used for atomic force microscopy AFM imaging.
Improving tapping mode atomic force microscopy with piezoelectric cantilevers
Ultramicroscopy, 2004
This article summarizes improvements to the speed, simplicity and versatility of tapping mode atomic force microscopy (AFM). Improvements are enabled by a piezoelectric microcantilever with a sharp silicon tip and a thin, low-stress zinc oxide (ZnO) film to both actuate and sense deflection. First, we demonstrate self-sensing tapping mode without laser detection. Similar previous work has been limited by unoptimized probe tips, cantilever thicknesses, and stress in the piezoelectric films. Tests indicate self-sensing amplitude resolution is as good or better than optical detection, with double the sensitivity, using the same type of cantilever. Second, we demonstrate self-oscillating tapping mode AFM. The cantilever's integrated piezoelectric film serves as the frequency-determining component of an oscillator circuit. The circuit oscillates the cantilever near its resonant frequency by applying positive feedback to the film. We present images and force-distance curves using both self-sensing and self-oscillating techniques. Finally, highspeed tapping mode imaging in liquid, where electric components of the cantilever require insulation, is demonstrated.