Peter Grutter - Academia.edu (original) (raw)

Papers by Peter Grutter

arXiv (Cornell University), Jun 23, 2023

The Si/SiO2 interface is populated by isolated trap states which modify its electronic properties... more The Si/SiO2 interface is populated by isolated trap states which modify its electronic properties. These traps are of critical interest for the development of semiconductor-based quantum sensors and computers, as well as nanoelectronic devices. Here, we study the electric susceptibility of the Si/SiO2 interface with nm spatial resolution using frequency-modulated atomic force microscopy to measure a patterned dopant delta-layer buried 2 nm beneath the silicon native oxide interface. We show that surface charge organization timescales, which range from 1 − 150 ns, increase significantly around interfacial states. We conclude that dielectric loss under time-varying gate biases at MHz and sub-MHz frequencies in metal-insulator-semiconductor capacitor device architectures is highly spatially heterogeneous over nm length scales.

Advanced electronic materials, Apr 18, 2019

bulkier systems for many in vitro and in vivo bioelectronic applications, [7] including high reso... more bulkier systems for many in vitro and in vivo bioelectronic applications, [7] including high resolution mapping of cell activity [7b,d] and flexible self-powered biosensors for electrophysiological signal monitoring. [8] To fabricate fully stretchable OECTs, the mechanical properties of PEDOT:PSS, which is inherently brittle, need to be modified by blending it with elastomers or surfactants. Mixtures of PEDOT:PSS with elastomers yield conductive gels. [9] However, for OECTs, thin films are preferred to gels since a low thickness favors a reversible and fast doping/ dedoping process, leading to a high ON/ OFF ratio and a fast response time. [10] Stretchable PEDOT:PSS thin films can be obtained by blending PEDOT:PSS and surfactants, which act as soft domains to absorb the external strain and reduce the electrostatic interactions between PEDOT and PSS. [6,11] Blends of PEDOT:PSS and surfactants are easily processable on stretchable substrates and can yield stretchable ultrathin films with a high conductivity. However, the effect of the processing parameters such as film thickness and baking temperature on the stretchability of PEDOT:PSS films is yet to be investigated. To push forward their applications in developing strain-insensitive OECTs, further optimization of the electromechanical properties of PEDOT:PSS thin films is needed to minimize the current change with strain. An additional challenge for fabricating fully stretchable OECTs is that they require stretchable metal contacts. Stretchable conductors such as liquid metals, Poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) based organic electrochemical transistors (OECTs) have been widely applied in bioelectronics because of their low power consumption, biocompatibility, and ability to convert ionic biological signals into electronic signals with high sensitivity. Here, the processing of PEDOT:PSS thin films on soft substrates is reported for stretchable OECT applications. Enhanced stretchability of PEDOT:PSS films on elastic substrates is obtained by synergistically reducing the film thickness and decreasing the baking temperature. The resultant films, together with ultrathin Au electrodes, enable the assembling of fully stretchable OECTs using conventional fabrication techniques, without prestretching the substrates. The stretchable OECTs maintain similar electrical characteristics within 30% applied strain. It is also demonstrated that brittle PEDOT:PSS films, which are not suitable for making stretchable OECTs, can be used for transparent pressure sensors.

arXiv (Cornell University), Sep 30, 2021

In this work, we experimentally demonstrate two-state fluctuations in a metal-insulatorsemiconduc... more In this work, we experimentally demonstrate two-state fluctuations in a metal-insulatorsemiconductor (MIS) device formed out of a metallic atomic force microscopy tip, vacuum gap, and multilayer MoSe2 sample. We show that noise in this device is intrinsically bias-dependent due to the bias-dependent surface potential, and does not require that the frequency or magnitude of individual dopant fluctuations are themselves bias-dependent. Finally, we measure spatial nonhomogeneities in band bending (charge reorganization) timescales.

Magnetic force microscopy (MFM) is a well-established technique for imaging the magnetic structur... more Magnetic force microscopy (MFM) is a well-established technique for imaging the magnetic structures of small magnetic particles. In cooperation with external magnetic fields, MFM can be used to study the magnetization switching mechanism of submicrometer-sized magnetic particles. Various MFM techniques allow the measurement of a hysteresis curve of an individual particle, which can then be compared to ensemble measurements. The advantage of using MFM-constructed hysteresis loops is that one can in principle understand the origin of dispersion in switching fields. It is also possible to directly observe the correlation between magnetic particles through careful imaging and control of the external magnetic field. In all of these measurements, attention needs to be paid to avoid artifacts that result from the unavoidable magnetic tip stray field. Control can be achieved by optimizing the MFM operation mode as well as the tip parameters. It is even possible to use the tip stray field to locally and reproducibly manipulate the magnetic-moment state of small particles. In this article, we illustrate these concepts and issues by studying various lithographically patterned magnetic nanoparticles, thus demonstrating the versatility of MFM for imaging, manipulation, and spectroscopic measurements of small particles.

$Research paper thumbnail of Quantifying bio-filament morphology below the diffraction limit of an optical microscope using out-of-focus images$

Applied Optics, Mar 19, 2020

A method to measure the dimensions of objects below the optical diffraction limit using diffracti... more A method to measure the dimensions of objects below the optical diffraction limit using diffraction analysis of out-of-focus bright-field images is presented. The method relies on the comparison of the diffraction patterns of an object of unknown size to those of calibration objects of known size. Correlative scanning electron microscope measurements are used to demonstrate the applicability of this method to measure 100 nm microbeads as well as objects with a geometry different from the calibration objects. This technique is important in the context of tethered particle experiments, in which bio-filaments are bound between a substrate and a microbead. This procedure is applied to obtain the diameters of axonal extensions or neurites that are mechanically created in samples of rat hippocampal neurons. The dependence of neurite geometry on mechanical pull speed is investigated, and the diameter is found to be rate independent.

Journal of Applied Physics, Apr 15, 1997

arXiv (Cornell University), Oct 25, 2019

Reliable operation of frequency modulation mode atomic force microscopy (FM-AFM) depends on a cle... more Reliable operation of frequency modulation mode atomic force microscopy (FM-AFM) depends on a clean resonance of an AFM cantilever. It is recognized that the spurious mechanical resonances which originate from various mechanical components in the microscope body are excited by a piezoelectric element that is intended for exciting the AFM cantilever oscillation and these spurious resonance modes cause the serious undesirable signal artifacts in both frequency shift and dissipation signals. We present an experimental setup to excite only the oscillation of the AFM cantilever in a fiber-optic interferometer system using optical excitation force. While the optical excitation force is provided by a separate laser light source with a different wavelength (excitation laser : λ = 1310 nm), the excitation laser light is still guided through the same single-mode optical fiber that guides the laser light (detection laser : λ = 1550 nm) used for the interferometric detection of the cantilever deflection. We present the details of the instrumentation and its performance. This setup allows us to eliminate the problems associated with the spurious mechanical resonances such as the apparent dissipation signal and the inaccuracy in the resonance frequency measurement.

Interleukin-13 inhibits proliferation and enhances contractility of human airway smooth muscle ce... more Interleukin-13 inhibits proliferation and enhances contractility of human airway smooth muscle cells without change in contractile phenotype.

The first commercial thermal scanning probe lithography tool is used for patterning of single- an... more The first commercial thermal scanning probe lithography tool is used for patterning of single- and bi-level surface-relief gratings. A modified tri-layer pattern transfer process is proposed to facilitate the fabrication of bi-level gratings.

Journal of The Mechanical Behavior of Biomedical Materials, Oct 1, 2019

We use micromanipulation techniques and real-time particle tracking to develop an approach to stu... more We use micromanipulation techniques and real-time particle tracking to develop an approach to study specific attributes of neuron mechanics. We use a mechanical probe composed of a hollow micropipette with its tip fixed to a functionalized bead to induce the formation of a neurite in a sample of rat hippocampal neurons. We then move the sample relative to the pipette tip, elongating the neurite while simultaneously measuring its tension by optically tracking the deflection of the beaded tip. By calibrating the spring constant of the pipette, we can convert this deflection to a force. We use this technique to obtain uniaxial strain measurements of induced neurites and investigate the dependence of the force-extension relationship on mechanical pull speed. We show that in the range of pull speeds studied (0.05-1.8 μm/s), the variation in the work to extend a neurite 10 μm is consistent across pull speeds. We do not observe statistically significant rate-dependent effects in the forceextension profiles; instead we find the same quadratic behaviour (with parameters drawn from the same distributions) at each pull speed.

Applied Physics Letters, Dec 3, 2018

A common use for atomic force microscopy is to quantify local forces through tip-sample interacti... more A common use for atomic force microscopy is to quantify local forces through tip-sample interactions between the probe tip and a sample surface. The accuracy of these measurements depends on the accuracy to which the cantilever spring constant is known. Recent work has demonstrated that the measured spring constant of a cantilever can vary up to a factor of two, even for the exact same cantilever measured by different users on different microscopes. Here we demonstrate that a standard method for calibrating the spring constant (using the oscillations due to thermal energy) is susceptible to ambient noise, which can alter the result significantly. We demonstrate a new step-by-step method to measure the spring constant by actively driving the cantilever to measure the resonance frequency and quality factor, giving results that are unaffected by acoustic noise. Our method can be performed rapidly on any atomic force microscope without any expensive additional hardware.

Applied Physics Letters, Apr 17, 2017

We report a Kelvin probe force microscopy (KPFM) implementation using the dissipation signal of a... more We report a Kelvin probe force microscopy (KPFM) implementation using the dissipation signal of a frequency modulation atomic force microscopy that is capable of detecting the gradient of electrostatic force rather than electrostatic force. It features a simple implementation and faster scanning as it requires no low frequency modulation. We show that applying a coherent ac voltage with two times the cantilever oscillation frequency induces the dissipation signal proportional to the electrostatic force gradient which depends on the effective dc bias voltage including the contact potential difference. We demonstrate the KPFM images of a MoS 2 flake taken with the present method is in quantitative agreement with that taken with the frequency modulated Kelvin probe force microscopy technique.

Beilstein Journal of Nanotechnology, Mar 1, 2019

Recently, there have been a number of variations of electrostatic force microscopy (EFM) that all... more Recently, there have been a number of variations of electrostatic force microscopy (EFM) that allow for the measurement of timevarying forces arising from phenomena such as ion transport in battery materials or charge separation in photovoltaic systems. These forces reveal information about dynamic processes happening over nanometer length scales due to the nanometer-sized probe tips used in atomic force microscopy. Here, we review in detail several time-resolved EFM techniques based on non-contact atomic force microscopy, elaborating on their specific limitations and challenges. We also introduce a new experimental technique that can resolve time-varying signals well below the oscillation period of the cantilever and compare and contrast it with those previously established.

Physical Review B, May 25, 2005

We used a combined ultrahigh vacuum scanning tunneling and atomic force microscope ͑STM/AFM͒ to s... more We used a combined ultrahigh vacuum scanning tunneling and atomic force microscope ͑STM/AFM͒ to study W tip-Au͑111͒ sample interactions in the regimes from weak coupling to strong interaction and simultaneously measure current changes from picoamperes to microamperes. Close correlation between conductance and interaction forces in a STM configuration was observed. In particular, the electrical and mechanical points of contact are determined based on the observed barrier collapse and adhesive bond formation, respectively. These points of contact, as defined by force and current measurements, coincide within measurement error. Ab initio calculations of the current as a function of distance in the tunneling regime is in quantitative agreement with experimental results. The obtained results are discussed in the context of dissipation in noncontact AFM as well as electrical contact formation in molecular electronics.

Physical Review Letters, Jan 8, 2010

We present theoretical and experimental results on the mechanical damping of an atomic force micr... more We present theoretical and experimental results on the mechanical damping of an atomic force microscope cantilever strongly coupled to a self-assembled InAs quantum dot. When the cantilever oscillation amplitude is large, its motion dominates the charge dynamics of the dot which in turn leads to nonlinear, amplitude-dependent damping of the cantilever. We observe highly asymmetric lineshapes of Coulomb blockade peaks in the damping that reflect the degeneracy of energy levels on the dot, in excellent agreement with our strong coupling theory. Furthermore, we predict that excited state spectroscopy is possible by studying the damping versus oscillation amplitude, in analogy to varying the amplitude of an ac gate voltage.

arXiv (Cornell University), Apr 20, 2017

W e review a new experimental implementation of Kelvin probe force microscopy (KPFM) in which the... more W e review a new experimental implementation of Kelvin probe force microscopy (KPFM) in which the dissipation signal of frequency modulation atomic force microscopy (FM-AFM) is used for dc bias voltage feedback (D-KPFM). The dissipation arises from an oscillating electrostatic force that is coherent with the tip oscillation, which is caused by applying the ac voltage between the tip and sample. The magnitude of the externally induced dissipation is found to be proportional to the effective dc bias voltage, which is the difference between the applied dc voltage and the contact potential difference. Two different implementations of D-KPFM are presented. In the first implementation, the frequency of the applied ac voltage, f el , is chosen to be the same as the tip oscillation (f el = f m : 1ωD-KPFM). In the second one, the ac voltage frequency, f el , is chosen to be twice the tip oscillation frequency (f el = 2f m : 2ωD-KPFM). In 1ωD-KPFM, the dissipation is proportional to the electrostatic force, which enables the use of a small ac voltage amplitude even down to ≈ 10 mV. In 2ωD-KPFM, the dissipation is proportional to the electrostatic force gradient, which results in the same potential contrast as that obtained by FM-KPFM. D-KPFM features a simple implementation with no lock-in amplifier and faster scanning as it requires no low frequency modulation. The use of a small ac voltage amplitude in 1ωD-KPFM is of great importance in characterizing of technically relevant materials in which their electrical properties can be disturbed by the applied electric field. 2ωD-KPFM is useful when more accurate potential measurement is required. The operations in 1ω and 2ωD-KPFM can be switched easily to take advantage of both features at the same location on a sample.

arXiv (Cornell University), Sep 5, 2018

Atomic force microscopy (AFM) is an analytical surface characterization tool which can reveal a s... more Atomic force microscopy (AFM) is an analytical surface characterization tool which can reveal a sample's topography with high spatial resolution while simultaneously probing tip-sample interactions. Local measurement of chemical properties with high-resolution has gained much popularity in recent years with advances in dynamic AFM methodologies. A calibration factor is required to convert the electrical readout to a mechanical oscillation amplitude in order to extract quantitative information about the surface. We propose a new calibration technique for the oscillation amplitude of electrically driven probes, which is based on measuring the electrical energy input to maintain the oscillation amplitude constant. We demonstrate the application of the new technique with quartz tuning fork including the qPlus configuration, while the same principle can be applied to other piezoelectric resonators such as length extension resonators, or piezoelectric cantilevers. The calibration factor obtained by this technique is found to be in agreement with using thermal noise spectrum method for capsulated, decapsulated tuning forks and tuning forks in the qPlus configuration.

arXiv (Cornell University), Dec 20, 2018

With recent advances in scanning probe microscopy (SPM), it is now routine to determine the atomi... more With recent advances in scanning probe microscopy (SPM), it is now routine to determine the atomic structure of surfaces and molecules while quantifying the local tip-sample interaction potentials. Such quantitative experiments are based on the accurate measurement of the resonance frequency shift due to the tip-sample interaction. Here, we experimentally show that the resonance frequency of oscillating probes used for SPM experiments change systematically as a function of oscillation amplitude under typical operating conditions. This change in resonance frequency is not due to tip-sample interactions, but rather due to the cantilever strain or geometric effects and thus the resonance frequency being a function of the oscillation amplitude. Our numerical calculations demonstrate that the amplitude dependence of the resonance frequency is an additional yet overlooked systematic error source that can result nonnegligible errors in measured interaction potentials and forces. Our experimental results and complementary numerical calculations reveal that the frequency shift due to this amplitude dependence needs to be corrected even for experiments with active oscillation amplitude control to be able to quantify the tip-sample interaction potentials and forces with milli-electron volt and pico-Newton resolutions.

Physical review, May 10, 2002

ChemInform, Jun 19, 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.