A versatile multipurpose scanning probe microscope (original) (raw)
Related papers
Modelling of conductive atomic force microscope probes for scanning tunnelling microscope operation
Micro and Nano Letters, 2012
A comprehensive model is proposed that can be used to select a proper conductive atomic force microscopy (CAFM) probe for use in stable scanning tunnelling microscopy (STM) operation. This type of operation mode could be useful for scanning and patterning heterogeneous surfaces with both conductive and insulating parts using electrical principles in a non-contact fashion. The model includes elastic contact deformation, intermolecular forces, electrostatic attraction and tunnelling current generation between the tip and the sample and the snap-into contact criterion of the probe. Using the model, snap-into contact distances of the probes with varying stiffness values under different bias voltages are found, and is verified with experiments. It is shown that, for a given sample and tip materials, an optimal bias voltage for STM operation with CAFM cantilevers exists. The results also show that, to successfully utilise CAFM probes as STM end-effectors, there is a minimum normal stiffness limit for a given bias voltage. For operation on metal surfaces using metal-coated probes with tip radius values smaller than 50 nm, the model predicts that probes with high stiffness values (.24 N/m) enable both STM and AFM operations reliably with potential resolution reduction in AFM force sensing. The model also implies that probes with longer tips are better for minimising the electrostatic attraction between the cantilever and the substrate. The model would help researchers to select proper CAFM probes, which could enable simultaneous AFM and STM imaging and manipulation capabilities for tip-based nanofabrication applications.
Multiple-Probe Scanning Probe Microscope
Compendium of Surface and Interface Analysis, 2018
Multiple-probe scanning probe microscope (MP-SPM) was developed to overcome difficulties in characterizing physical properties of nanoscale structures and materials with conventional SPM families, such as a scanning tunneling microscope (STM), an atomic force microscope (AFM), and the related proximal probe microscopes [1-14]. Conventional SPMs use a single probe to observe surface structures and local properties at a high-spatial resolution down to atomic scale. In the case of STM, as shown in Fig. 64.1a, an electrical current flowing to/from a conductive and atomically sharpened probe from/to a conductive sample establishes a concentration of current at a surface of the sample and this is the reason why STM is very sensitive to local density of states (LDOS) of the surface. Here, since the STM probe and the surface are separated by a small (typically 1 nm) vacuum gap, current is obtained via tunneling of electrons across the spatial gap, providing very accurate control of probe-to-sample distance via a feedback control to maintain the tunneling current constant, for example. As readily understood from Fig. 64.1a, conventional STM is measuring electrical current flowing in the direction perpendicular to the surface plane as shown by the red arrow. Therefore, a single-probe STM is essentially not suitable to measure electrical properties in the direction parallel to sample surfaces, while, in many cases, we want to measure electrical properties of surfaces, nanomaterials placed on surfaces, and device structures fabricated on surfaces. Therefore, multiple-probe
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.
Nanoscale, 2009
Atomic force microscopy (AFM) is in its thirties and has become an invaluable tool for studying the micro-and nanoworlds. As a stand-alone, high-resolution imaging technique and force transducer, it defies most other surface instrumentation in ease of use, sensitivity and versatility. Still, the technique has limitations to overcome. A promising way is to integrate the atomic force microscope into hybrid devices, a combination of two or three complementary techniques in one instrument. In this way, a comprehensive description of molecular processes is at hand; morphological, (electro)chemical, mechanical and kinetic information are simultaneously obtained in one experiment. Hereby we review the recent efforts towards such development, describing the aim and the applications resulting from the combination of AFM with spectroscopic, optical, mechanical or electrochemical techniques. Interesting possibilities include using AFM to bring optical microscopies beyond the diffraction limit and also bestowing spectroscopic capabilities on the atomic force microscope.
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.
Fabrication of conductive atomic force microscope probes and their evaluation for carrier mapping
Smart Sensors, Actuators, and MEMS, 2003
Scanning Spreading Resistance Microscopy (SSRM) and Scanning Capacitance Microscopy (SCM) are two techniques based upon the atomic force microscope (AFM), which are used to obtain two-dimensional carrier maps of a semiconductor device's cross-section. As all AFM techniques, they require probes with sharp tips to get good resolution images. Additionally, a hard and wear resistant tip material is needed to withstand the extreme mechanical stress tips are submitted to while a good conductivity is necessary for the characterization of highly doped areas of modern devices. In this work, several types of materials are evaluated based upon their mechanical and electrical characteristics: metals, hardmetals, conductive oxides and doped diamond. Commercial metal and diamond coated silicon tips are currently used (only diamond for SSRM). However, tips with thin metal coatings wear fast while the high resistivity of diamond limits the dynamic range. In both cases, the radius of curvature of coated tips is fairly large limiting the resolution. Probes with tips made out of TiN, a hardmetal, were manufactured using the molding technique. Using these tips, an ohmic point contact was obtained on Si. In SSRM mode, resistivity contrast was observed for the first time for a metallic tip. TiN tips also proved to be hard enough to penetrate the oxide and obtain SSRM images on InP. A good contrast and a monotonic behavior on n-type silicon in the absence of bias were obtained in SCM. The wear rate of TiN tips is lower than that of coated Si tips. However, despite their high hardness, TiN tips wore fast under high pressure and the tips died after a few SSRM scan lines on Si, and after a few images on InP.
Photomask Technology 2019, 2019
An integration of atomic force microscopy (AFM) and scanning electron microscopy (SEM) within a single system is opening new capabilities for correlative microscopy and tip-induced nanoscale interactions. Here, the performance of an AFM-integration into a high resolution scanning electron microscope and focused ion beam (FIB) system for nanoscale characterization and nanofabrication is presented. Combining the six-axis degree of freedom (DOF) of the AFM system with the DOF of the SEM stage system, the total number of independent degree of freedom of the configuration becomes eleven. The AFM system is using piezoresistive thermo-mechanically transduced cantilevers (active cantilevers). The AFM integrated into SEM is using active cantilevers that can characterize and generate nanostructures all in situ without the need to break vacuum or contaminate the sample. The developed AFM-integration is described and its performance is demonstrated. The benefit of the active cantilever prevents the use of heavy and complex optical cantilever detection technique and makes the AFM integration into a SEM very simple and convenient. Results from combined examinations applying fast AFM-methods and SEM-image fusion, AFM-SEM combined metrology verification, and tip-based nanofabrication are shown. Simultaneous operation of SEM and AFM provides a fast navigation combined with sub-nm topographic image acquisition. The combination of two or more different types of techniques like SEM, energy dispersive x-ray spectroscopy, and AFM is called correlative microscopy because analytical information from the same place of the sample can be obtained and correlated [1]. We introduced to the SEM/FIB tool correlative nanofabrication methods like field-emission scanning probe 11148-51 N • E • W • S BACUS News is published monthly by SPIE for BACUS, the international technical group of SPIE dedicated to the advancement of photomask technology.
Indirect tip fabrication for Scanning Probe Microscopy
Microelectronic Engineering, 1996
Different fabrication technologies for Scanning Probe Microscopy tips have been investigated, using the so called mould technique. By a combination of reactive ion etching and wet anisotropic etching novel, high aspect ratio tip moulds have been produced in silicon. The resulting tip shapes are investigated by electroplating a nickel layer on the silicon substrate, whereafter the silicon is removed, yielding conductive tips, which can be used for Atomic Force Microscopy as well as Scanning Tunnelling Microscopy.
Introductory Review, Scanning Tunneling Microscopy (STM) & Atomic Force Microscopy (AFM)
Atomic-scale resolution is needed to study the arrangement of atoms in materials and advance the understanding of properties and behavior they exhibit. Since the seventeenth-century optical microscopes using visible light as illumination source have led our quest to observe microscopic species but the resolution attainable quickly reached physical limits due to the relatively longer wavelength of visible light and deterring hazard of using a wavelength in UV spectrum. After the discovery of wave nature associated with particle bodies, a new channel of thought opened considering much shorter wavelength of particles and their special properties when interacting with the sample under observation. These particles i.e. electrons, neutrons and ions were developed in different techniques and were used as illumination sources. Herein, the development of scanning tunneling microscopy which used electrons to uncover irregularities of the arrangement of atoms in a thin material via the quantum mechanical phenomenon of electron tunneling has become a sensational invention. Atomic Force Microscopy (AFM) is a development over STM which relied on measuring the forces of contact between the sample and a scanning probe which overcomes the earlier technique only allowing conductors or pretreated surfaces for rendering them conducting, to be observed. Since measuring contact forces between materials is a more fundamental approach, that is equally and more sensitive than measuring tunneling current flowing between them, atomic force microscopy has been successfully able to image insulators as well as semiconductors and conductors with atomic resolution, by substituting tunneling current with an atomic contact force sensing arrangement, a delicate cantilever, which can image conductors and insulators alike via mechanical “touch” while running over surface atoms of the sample. Since the sample surface contamination with foreign atoms and humidity can affect the success of AFM, in sophisticated labs, it is done in an ultra-high vacuum environment with the surface adequately cleaned of impurities and prepared for flatness. Maintaining such an assembly is challenging, however, AFM has seen the massive proliferation in hobbyist’s lab as well, in form of ambient condition scanning environment technique and through self-assembled instrumentations. The success of ATM as a cost-effective imaging tool with dramatically increased ease of understanding and use particularly with the much needed assistance of significant computing power in the form of personal computers which offset the computational difficulty of resolving experimental information, which in turn is responsible for physical simplicity of instrument design, and thus its proliferation to numerous labs in universities and technology companies worldwide.
Journal of vacuum science and technology, 2018
More than 40 years after its invention, the atomic force microscopy (AFM) can be integrated with scanning electron microscope (SEM) instruments as an increasingly capable and productive characterization tool with sub-nanometer spatial resolution. The authors have designed and developed an AFM instrument capable to be integrated into any SEM or in a combination of SEM with a focused ion-beam (FIB) tool. The combination of two or more different types of techniques like SEM, energy dispersive x-ray spectroscopy, and AFM is called correlative microscopy because analytical information from the same place of the sample can be obtained and correlated. For the first time, they introduced to the SEM/FIB tool correlative nanofabrication methods like field-emission scanning probe lithography, tip-based electron beam induced deposition, and nanomachining. The combination of all these methods provides a completely new nanotechnology instrument, which should be seen as a tool for correlative nanofabrication and microscopy. Thus, it provides for the first time the capabilities of a stand-alone instrument with the capabilities of nondestructive three-dimensional tip-based metrology and nanofabrication into the combined SEM/FIB tool. In this article, the authors describe all these methods in detail and present a brief example of the results obtained. They demonstrate that the self-sensing, self-actuating cantilevers (called active cantilevers) equipped with Diamond tip are a versatile toolkit for fast imaging and emerging nanofabrication. The AFM integrated into SEM is using active cantilevers that can characterize and generate nanostructures all in situ without the need to break-vacuum or contaminate the sample.