Atomic force microscopy is one of the most important tools in nanoscience. It employs an atomic p... more Atomic force microscopy is one of the most important tools in nanoscience. It employs an atomic probe that can resolve surfaces with atomic and subatomic spatial resolution and manipulate atoms. The qPlus sensor is a quartz-based self-sensing cantilever with a high stiffness that, in contrast to Si cantilevers, allows to oscillate at atomic radius amplitudes in the proximity of reactive surfaces and thus provides a high spatial resolution. This article reports on the development of this sensor and discusses applications in materials research.
The combination of inelastic electron tunneling spectroscopy (IETS), also used for IET spectrum b... more The combination of inelastic electron tunneling spectroscopy (IETS), also used for IET spectrum based on scanning tunneling microscopy with atomic force microscopy (AFM) enables us to measure the vibrational energies of a single molecule along with the force exerted by the tip of a microscope, which deepens our understanding on the interaction between the tip and the molecule on a surface. The resolution of IETS is a crucial factor in determining the vibrational energies of a molecule. However, radio frequency (RF) noise from the environment significantly deteriorates the resolution. We introduce an RF noise filtering technique, which enables high resolution IETS while maintaining uncompromised AFM performance, demonstrated by vibrational measurements of a CO molecule on a copper surface.
When perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) is deposited on the Ag(111) surface at... more When perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) is deposited on the Ag(111) surface at submonolayer coverage, it forms islands under which the native Shockley state of the Ag(111) surface can no longer be found. Previous work has shown that this state shifts upwards to form a new interface state starting at 0.6 V above the Fermi level, having properties of a two-dimensional electron gas (2DEG). We investigated mixed islands of PTCDA and copper phthalocyanine (CuPc) to study the change in the electronic state with the addition of an electron donor. We no longer observe a 2DEG state and instead identify states at 0.46 and 0.79 V. While one state appears in dI/dV images as an array of one-dimensional quantum wells, our analysis shows that this state does not act as a free electron gas and that the features are instead localized above individual PTCDA molecules.
Scanning probe microscopy can be used to probe the internal atomic structure of flat organic mole... more Scanning probe microscopy can be used to probe the internal atomic structure of flat organic molecules. This technique requires an unreactive tip and has, until now, been demonstrated only at liquid helium and liquid nitrogen temperatures. We demonstrate intramolecular and intermolecular force contrast at room temperature on PTCDA molecules adsorbed on a Ag=Sið111Þ-ð ffiffi ffi 3 p × ffiffi ffi 3 p Þ surface. The oscillating force sensor allows us to dynamically measure the vertical decay constant of the tunneling current. The precision of this method is increased by quantifying the transimpedance of the current to voltage converter and accounting for the tip oscillation. This measurement yields a clear contrast between neighboring molecules, which we attribute to the different charge states.
Atomically-resolved imaging and force measurements using the atomic force microscope (AFM) are pe... more Atomically-resolved imaging and force measurements using the atomic force microscope (AFM) are performed most commonly in a frequency-modulation (FM) mode. This has led to spectacular results, including direct observation of the atomic structure of complex molecules and quantification of chemical and frictional forces at the atomic scale. We address here a critical question: Is recovery of force from the measured frequency shift experienced by the AFM cantilever ill-posed-that is, unreliable in the presence of (unavoidable) measurement uncertainty? Resolution of this issue underlies all force measurements using FM-AFM, but remains outstanding. It is shown that concavity of the force law's distance dependence controls ill-posed behavior, with a rapid concavity change corrupting force measurements by inducing spurious and unphysical effects-such rapid change is not uncommon. Practical conditions to eliminate ill-posed behavior are formulated which are verified experimentally. This study lays the foundations for robust atomically-resolved force spectroscopy and future work that will seek to regularize ill-posed force measurements.
Nanoscience pioneer who invented advanced microscopes Calvin (“Cal”) Forrest Quate, a pioneer in ... more Nanoscience pioneer who invented advanced microscopes Calvin (“Cal”) Forrest Quate, a pioneer in nanoscience and inventor of new forms of microscopy, passed away on 6 July 2019. He was 95. Cal was always on the lookout for science's practical applications. His inquisitive and inventive mind led to important advances in disparate fields ranging from electron beam interactions in microwave devices to high-resolution acoustical imaging. He is best known today for his role in developing the atomic force microscope (AFM), now an indispensable nanoscience tool.
Sliding friction is a nonconservative force in which kinetic energy is dissipated via various phe... more Sliding friction is a nonconservative force in which kinetic energy is dissipated via various phenomena. We used lateral force microscopy to measure the energy loss as a tip oscillates laterally above a surface with sub-Angstrom amplitudes. By terminating the tip with a single molecule, we ensure the tip ends in a single atom. We have reported that energy is dissipated as a CO molecule at the tip apex is oscillated over pairs of atoms. This is a result of the CO being bent in different directions as the tip moves in one direction and then in the other. We confirm this with a model that describes the CO on the tip as a torsional spring. Surprisingly, we only observe dissipation within a small range of tip heights. This allows us to determine the necessary components to model friction and shows how sensitive friction is to the local potential energy landscape.
Fabrication of devices incorporating transition metal dichalcogenides (TMDCs) is mostly done in a... more Fabrication of devices incorporating transition metal dichalcogenides (TMDCs) is mostly done in ambient conditions and thus investigation of TMDCs' cleanliness in air at the nanoscale is important. We imaged MoS 2 , WS 2 , MoSe 2 and WSe 2 by using atomic force microscopy (AFM). Mechanical exfoliation of the TMDCs provided clean terraces on sulfides MoS 2 and WS 2. In contrast, the selenides appeared to be contaminated directly after cleavage in most cases. Long-term measurements on MoSe 2 revealed that these unwanted adsorbates are mobile on the surface. In situ cleavage and imaging of WSe 2 in ultra-high vacuum shows clean surfaces, proving the airborne character of the adsorbed particles.
Platinum is relatively reactive, compared to silver and copper, which prompted us to study the gr... more Platinum is relatively reactive, compared to silver and copper, which prompted us to study the growth and structure of a thin insulating layer on Pt(111). We grew monolayer islands of NaCl and studied them with scanning tunneling microscopy (STM) and atomic force microscopy (AFM). STM images of the islands revealed a square lattice which we confirmed, via density functional theory (DFT) calculations, to be the Cl anions, similar to other surfaces. Surprisingly, however, the AFM images appeared to only resolve approximately two-thirds of the Cl ions. DFT calculations showed that the adsorption heights of the Cl anions above the surface have a bimodal distribution in which they are either approximately 60 pm above the Na ionic plane or 40 pm lower. An electrostatic model shows that this structure reproduces the AFM observations.
The resolution of frequency modulation atomic force microscopy is limited by instrumental noise. ... more The resolution of frequency modulation atomic force microscopy is limited by instrumental noise. When using a qPlus sensor, the deflection detector noise is the dominant noise contribution. It can be reduced by improving the preamplifier used to amplify the sensor deflection signal. We present a simple single-stage differential preamplifier which outperforms previous designs known to us by at least a factor of two in the deflection noise density. We show specific versions of this preamplifier to use in ambient conditions, in ultra-high vacuum at room temperature, and at 4.2 K. Furthermore, we compare the thermal peak analysis and the frequency shift noise density method as a means to determine the deflection noise density. We note that this preamplifier can also be used for any currentgenerating sensors such as other piezoelectric sensors and photodiodes, but, in this paper, we restrict our analysis to qPlus sensors.
Surface-layer (S-layer) proteins form the outermost envelope in many bacteria and most archaea an... more Surface-layer (S-layer) proteins form the outermost envelope in many bacteria and most archaea and arrange in 2D quasi-crystalline structures via self-assembly. We investigated S-layer proteins extracted from the archaeon Pyrobaculum aerophilium with a qPlus sensor-based atomic force microscope (AFM) in both liquid and ambient conditions and compared it to transmission electron microscopy (TEM) images under vacuum conditions. For AFM scanning, a next-generation liquid cell and a new protocol for creating long and sharp sapphire tips was introduced. Initial AFM images showed only layers of residual detergent molecules (SDS), which are used to isolate the Slayer proteins from the cells. SDS was not visible in the TEM images, requiring a more thorough (11) Volkl, P.
Artificial diamond is created by exposing graphite to pressures on the order of 10 GPa and temper... more Artificial diamond is created by exposing graphite to pressures on the order of 10 GPa and temperatures of about 2000 K. Here, we provide evidence that the pressure exerted by the tip of an atomic force microscope onto graphene over the carbon buffer layer of silicon carbide can lead to a temporary transition of graphite to diamond on the atomic scale. We perform atomic force microscopy with CO terminated tips and copper oxide (CuOx) tips to image graphene and to induce the structural transition. A local transition induced by the force of the tip is accompanied by local rehybridization from an sp2-bonded to an sp3-bonded local structure. Density functional theory predicts that a repulsive threshold of ≈ 13 nN, followed by a force reduction by ≈ 4 nN is overcome when inducing the graphite-diamond transition. The experimental observation of the third harmonic with a magnitude of about 200 fm fits well to overcoming a force barrier of F barrier ≈ 5 nN, followed by a force reduction by −F barrier and an upswing by F barrier for decreasing distances. Experimental evidence for this transition is provided by the emergence of third harmonics in the cantilever oscillation when the laterally flexible CO terminated tip exerts a large repulsive force. Probing the sample with rigid CuOx tips in the strong repulsive regime shows a strong difference in the yielding of the A versus B sites to the pressure of the tip. The large repulsive overall force of ≈ 10 nN is only compatible with the experimental data if one assumes that the repulsive force acting on the tip when inducing the transition is compensated by a heavily increased van-der-Waals attraction of the tip due to form fitting of tip and sample by local indentation. The experiment also shows that atomic force microscopy allows to perform high pressure physics on the atomic scale.
What defines the lifetime of electronic states in artificial quantum structures? We measured the ... more What defines the lifetime of electronic states in artificial quantum structures? We measured the spectral widths of resonant eigenstates in a circular, CO-based quantum corral on a Cu(111) surface and found that the widths are related to the size of the corral and that the line shape is essentially Gaussian. A model linking the energy dependence with the movement of single surface electrons shows that the observed behavior is consistent with lifetime limitations due to interaction with the corral walls.
Since the original publication of Noncontact Atomic Force Microscopy in 2002, the noncontact atom... more Since the original publication of Noncontact Atomic Force Microscopy in 2002, the noncontact atomic force microscope (NC-AFM) has achieved remarkable progress. This second treatment deals with the following outstanding recent results obtained with atomic resolution since then: force spectroscopy and mapping with atomic resolution; tuning fork; atomic manipulation; magnetic exchange force microscopy; atomic and molecular imaging in liquids; and other new technologies. These results and technologies are now helping evolve NC-AFM toward practical tools for characterization and manipulation of individual atoms/molecules and nanostructures with atomic/subatomic resolution. Therefore, the book exemplifies how NC-AFM has become a crucial tool for the expanding fields of nanoscience and nanotechnology
Scanning probe microscopy (SPM) methods such as scanning tunneling microscopy (STM) and noncontac... more Scanning probe microscopy (SPM) methods such as scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) are the basic technologies for nanotechnology and also for future bottom-up processes. In Sect. 5.1, the principles of AFM such as its operating modes and the NC-AFM frequency-modulation method are fully explained. Then, in Sect. 5.2, applications of NC-AFM to semiconductors, which make clear its potential in terms of spatial resolution and function, are introduced. Next, in Sect. 5.3, applications of NC-AFM to insulators such as alkali halides, fluorides and transition-metal oxides are introduced. Lastly, in Sect. 5.4, applications of NC-AFM to molecules such as carboxylate (RCOO – ) with R = H, CH3, C(CH3)3 and CF3 are introduced. Thus, NC-AFM can observe atoms and molecules on various kinds of surfaces such as semiconductors, insulators and metal oxides with atomic or molecular resolution. These sections are essential to understand the state of the art and future possibilities for NC-AFM, which is the second generation of atom/molecule technology.
Proceedings ... annual meeting, Electron Microscopy Society of America, 1994
The atomic force microscope (AFM) works by measuring the deflection of a cantilever as it is scan... more The atomic force microscope (AFM) works by measuring the deflection of a cantilever as it is scanned over a sample. A sharp tip at the end of the cantilever is responsible for the high lateral resolution achieved with the AFM. There are several ways to measure the deflection of the cantilever. The technique used to measure the deflection of the cantilever most often dictates the mechanical complexity and stability of the instrument. Electron tunneling, interferometry and capacitive sensors have been used successfully. The most common way to measure the cantilever deflection is by means of an optical deflection detector.The piezoresistivc cantilever offers a new way to measure the deflection of the cantilever, with performances comparable to the performances of other deflection detectors, and with the advantage that the sensor is incorporated in the cantilever. This simplifies the design and operation of the microscope In particular, the piezoresistive cantilever facilitates the use and often improves the performances of an AFM when operated in ultra high vacuum (UHV), at low temperature, or when used to image large samples.
Atomic force microscopy is one of the most important tools in nanoscience. It employs an atomic p... more Atomic force microscopy is one of the most important tools in nanoscience. It employs an atomic probe that can resolve surfaces with atomic and subatomic spatial resolution and manipulate atoms. The qPlus sensor is a quartz-based self-sensing cantilever with a high stiffness that, in contrast to Si cantilevers, allows to oscillate at atomic radius amplitudes in the proximity of reactive surfaces and thus provides a high spatial resolution. This article reports on the development of this sensor and discusses applications in materials research.
The combination of inelastic electron tunneling spectroscopy (IETS), also used for IET spectrum b... more The combination of inelastic electron tunneling spectroscopy (IETS), also used for IET spectrum based on scanning tunneling microscopy with atomic force microscopy (AFM) enables us to measure the vibrational energies of a single molecule along with the force exerted by the tip of a microscope, which deepens our understanding on the interaction between the tip and the molecule on a surface. The resolution of IETS is a crucial factor in determining the vibrational energies of a molecule. However, radio frequency (RF) noise from the environment significantly deteriorates the resolution. We introduce an RF noise filtering technique, which enables high resolution IETS while maintaining uncompromised AFM performance, demonstrated by vibrational measurements of a CO molecule on a copper surface.
When perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) is deposited on the Ag(111) surface at... more When perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) is deposited on the Ag(111) surface at submonolayer coverage, it forms islands under which the native Shockley state of the Ag(111) surface can no longer be found. Previous work has shown that this state shifts upwards to form a new interface state starting at 0.6 V above the Fermi level, having properties of a two-dimensional electron gas (2DEG). We investigated mixed islands of PTCDA and copper phthalocyanine (CuPc) to study the change in the electronic state with the addition of an electron donor. We no longer observe a 2DEG state and instead identify states at 0.46 and 0.79 V. While one state appears in dI/dV images as an array of one-dimensional quantum wells, our analysis shows that this state does not act as a free electron gas and that the features are instead localized above individual PTCDA molecules.
Scanning probe microscopy can be used to probe the internal atomic structure of flat organic mole... more Scanning probe microscopy can be used to probe the internal atomic structure of flat organic molecules. This technique requires an unreactive tip and has, until now, been demonstrated only at liquid helium and liquid nitrogen temperatures. We demonstrate intramolecular and intermolecular force contrast at room temperature on PTCDA molecules adsorbed on a Ag=Sið111Þ-ð ffiffi ffi 3 p × ffiffi ffi 3 p Þ surface. The oscillating force sensor allows us to dynamically measure the vertical decay constant of the tunneling current. The precision of this method is increased by quantifying the transimpedance of the current to voltage converter and accounting for the tip oscillation. This measurement yields a clear contrast between neighboring molecules, which we attribute to the different charge states.
Atomically-resolved imaging and force measurements using the atomic force microscope (AFM) are pe... more Atomically-resolved imaging and force measurements using the atomic force microscope (AFM) are performed most commonly in a frequency-modulation (FM) mode. This has led to spectacular results, including direct observation of the atomic structure of complex molecules and quantification of chemical and frictional forces at the atomic scale. We address here a critical question: Is recovery of force from the measured frequency shift experienced by the AFM cantilever ill-posed-that is, unreliable in the presence of (unavoidable) measurement uncertainty? Resolution of this issue underlies all force measurements using FM-AFM, but remains outstanding. It is shown that concavity of the force law's distance dependence controls ill-posed behavior, with a rapid concavity change corrupting force measurements by inducing spurious and unphysical effects-such rapid change is not uncommon. Practical conditions to eliminate ill-posed behavior are formulated which are verified experimentally. This study lays the foundations for robust atomically-resolved force spectroscopy and future work that will seek to regularize ill-posed force measurements.
Nanoscience pioneer who invented advanced microscopes Calvin (“Cal”) Forrest Quate, a pioneer in ... more Nanoscience pioneer who invented advanced microscopes Calvin (“Cal”) Forrest Quate, a pioneer in nanoscience and inventor of new forms of microscopy, passed away on 6 July 2019. He was 95. Cal was always on the lookout for science's practical applications. His inquisitive and inventive mind led to important advances in disparate fields ranging from electron beam interactions in microwave devices to high-resolution acoustical imaging. He is best known today for his role in developing the atomic force microscope (AFM), now an indispensable nanoscience tool.
Sliding friction is a nonconservative force in which kinetic energy is dissipated via various phe... more Sliding friction is a nonconservative force in which kinetic energy is dissipated via various phenomena. We used lateral force microscopy to measure the energy loss as a tip oscillates laterally above a surface with sub-Angstrom amplitudes. By terminating the tip with a single molecule, we ensure the tip ends in a single atom. We have reported that energy is dissipated as a CO molecule at the tip apex is oscillated over pairs of atoms. This is a result of the CO being bent in different directions as the tip moves in one direction and then in the other. We confirm this with a model that describes the CO on the tip as a torsional spring. Surprisingly, we only observe dissipation within a small range of tip heights. This allows us to determine the necessary components to model friction and shows how sensitive friction is to the local potential energy landscape.
Fabrication of devices incorporating transition metal dichalcogenides (TMDCs) is mostly done in a... more Fabrication of devices incorporating transition metal dichalcogenides (TMDCs) is mostly done in ambient conditions and thus investigation of TMDCs' cleanliness in air at the nanoscale is important. We imaged MoS 2 , WS 2 , MoSe 2 and WSe 2 by using atomic force microscopy (AFM). Mechanical exfoliation of the TMDCs provided clean terraces on sulfides MoS 2 and WS 2. In contrast, the selenides appeared to be contaminated directly after cleavage in most cases. Long-term measurements on MoSe 2 revealed that these unwanted adsorbates are mobile on the surface. In situ cleavage and imaging of WSe 2 in ultra-high vacuum shows clean surfaces, proving the airborne character of the adsorbed particles.
Platinum is relatively reactive, compared to silver and copper, which prompted us to study the gr... more Platinum is relatively reactive, compared to silver and copper, which prompted us to study the growth and structure of a thin insulating layer on Pt(111). We grew monolayer islands of NaCl and studied them with scanning tunneling microscopy (STM) and atomic force microscopy (AFM). STM images of the islands revealed a square lattice which we confirmed, via density functional theory (DFT) calculations, to be the Cl anions, similar to other surfaces. Surprisingly, however, the AFM images appeared to only resolve approximately two-thirds of the Cl ions. DFT calculations showed that the adsorption heights of the Cl anions above the surface have a bimodal distribution in which they are either approximately 60 pm above the Na ionic plane or 40 pm lower. An electrostatic model shows that this structure reproduces the AFM observations.
The resolution of frequency modulation atomic force microscopy is limited by instrumental noise. ... more The resolution of frequency modulation atomic force microscopy is limited by instrumental noise. When using a qPlus sensor, the deflection detector noise is the dominant noise contribution. It can be reduced by improving the preamplifier used to amplify the sensor deflection signal. We present a simple single-stage differential preamplifier which outperforms previous designs known to us by at least a factor of two in the deflection noise density. We show specific versions of this preamplifier to use in ambient conditions, in ultra-high vacuum at room temperature, and at 4.2 K. Furthermore, we compare the thermal peak analysis and the frequency shift noise density method as a means to determine the deflection noise density. We note that this preamplifier can also be used for any currentgenerating sensors such as other piezoelectric sensors and photodiodes, but, in this paper, we restrict our analysis to qPlus sensors.
Surface-layer (S-layer) proteins form the outermost envelope in many bacteria and most archaea an... more Surface-layer (S-layer) proteins form the outermost envelope in many bacteria and most archaea and arrange in 2D quasi-crystalline structures via self-assembly. We investigated S-layer proteins extracted from the archaeon Pyrobaculum aerophilium with a qPlus sensor-based atomic force microscope (AFM) in both liquid and ambient conditions and compared it to transmission electron microscopy (TEM) images under vacuum conditions. For AFM scanning, a next-generation liquid cell and a new protocol for creating long and sharp sapphire tips was introduced. Initial AFM images showed only layers of residual detergent molecules (SDS), which are used to isolate the Slayer proteins from the cells. SDS was not visible in the TEM images, requiring a more thorough (11) Volkl, P.
Artificial diamond is created by exposing graphite to pressures on the order of 10 GPa and temper... more Artificial diamond is created by exposing graphite to pressures on the order of 10 GPa and temperatures of about 2000 K. Here, we provide evidence that the pressure exerted by the tip of an atomic force microscope onto graphene over the carbon buffer layer of silicon carbide can lead to a temporary transition of graphite to diamond on the atomic scale. We perform atomic force microscopy with CO terminated tips and copper oxide (CuOx) tips to image graphene and to induce the structural transition. A local transition induced by the force of the tip is accompanied by local rehybridization from an sp2-bonded to an sp3-bonded local structure. Density functional theory predicts that a repulsive threshold of ≈ 13 nN, followed by a force reduction by ≈ 4 nN is overcome when inducing the graphite-diamond transition. The experimental observation of the third harmonic with a magnitude of about 200 fm fits well to overcoming a force barrier of F barrier ≈ 5 nN, followed by a force reduction by −F barrier and an upswing by F barrier for decreasing distances. Experimental evidence for this transition is provided by the emergence of third harmonics in the cantilever oscillation when the laterally flexible CO terminated tip exerts a large repulsive force. Probing the sample with rigid CuOx tips in the strong repulsive regime shows a strong difference in the yielding of the A versus B sites to the pressure of the tip. The large repulsive overall force of ≈ 10 nN is only compatible with the experimental data if one assumes that the repulsive force acting on the tip when inducing the transition is compensated by a heavily increased van-der-Waals attraction of the tip due to form fitting of tip and sample by local indentation. The experiment also shows that atomic force microscopy allows to perform high pressure physics on the atomic scale.
What defines the lifetime of electronic states in artificial quantum structures? We measured the ... more What defines the lifetime of electronic states in artificial quantum structures? We measured the spectral widths of resonant eigenstates in a circular, CO-based quantum corral on a Cu(111) surface and found that the widths are related to the size of the corral and that the line shape is essentially Gaussian. A model linking the energy dependence with the movement of single surface electrons shows that the observed behavior is consistent with lifetime limitations due to interaction with the corral walls.
Since the original publication of Noncontact Atomic Force Microscopy in 2002, the noncontact atom... more Since the original publication of Noncontact Atomic Force Microscopy in 2002, the noncontact atomic force microscope (NC-AFM) has achieved remarkable progress. This second treatment deals with the following outstanding recent results obtained with atomic resolution since then: force spectroscopy and mapping with atomic resolution; tuning fork; atomic manipulation; magnetic exchange force microscopy; atomic and molecular imaging in liquids; and other new technologies. These results and technologies are now helping evolve NC-AFM toward practical tools for characterization and manipulation of individual atoms/molecules and nanostructures with atomic/subatomic resolution. Therefore, the book exemplifies how NC-AFM has become a crucial tool for the expanding fields of nanoscience and nanotechnology
Scanning probe microscopy (SPM) methods such as scanning tunneling microscopy (STM) and noncontac... more Scanning probe microscopy (SPM) methods such as scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) are the basic technologies for nanotechnology and also for future bottom-up processes. In Sect. 5.1, the principles of AFM such as its operating modes and the NC-AFM frequency-modulation method are fully explained. Then, in Sect. 5.2, applications of NC-AFM to semiconductors, which make clear its potential in terms of spatial resolution and function, are introduced. Next, in Sect. 5.3, applications of NC-AFM to insulators such as alkali halides, fluorides and transition-metal oxides are introduced. Lastly, in Sect. 5.4, applications of NC-AFM to molecules such as carboxylate (RCOO – ) with R = H, CH3, C(CH3)3 and CF3 are introduced. Thus, NC-AFM can observe atoms and molecules on various kinds of surfaces such as semiconductors, insulators and metal oxides with atomic or molecular resolution. These sections are essential to understand the state of the art and future possibilities for NC-AFM, which is the second generation of atom/molecule technology.
Proceedings ... annual meeting, Electron Microscopy Society of America, 1994
The atomic force microscope (AFM) works by measuring the deflection of a cantilever as it is scan... more The atomic force microscope (AFM) works by measuring the deflection of a cantilever as it is scanned over a sample. A sharp tip at the end of the cantilever is responsible for the high lateral resolution achieved with the AFM. There are several ways to measure the deflection of the cantilever. The technique used to measure the deflection of the cantilever most often dictates the mechanical complexity and stability of the instrument. Electron tunneling, interferometry and capacitive sensors have been used successfully. The most common way to measure the cantilever deflection is by means of an optical deflection detector.The piezoresistivc cantilever offers a new way to measure the deflection of the cantilever, with performances comparable to the performances of other deflection detectors, and with the advantage that the sensor is incorporated in the cantilever. This simplifies the design and operation of the microscope In particular, the piezoresistive cantilever facilitates the use and often improves the performances of an AFM when operated in ultra high vacuum (UHV), at low temperature, or when used to image large samples.
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Papers by Franz Giessibl