Kelvin probe force microscopy as a tool for characterizing chemical sensors

Grover, Ranjan; Carthy, B. Mc; Zhao, Yanming; Jabbour, Ghassan E.; Sarid, Dror; Laws, G. M.; Takulapalli, Bharath R.; Thornton, Trevor; Gust, Devens

doi:10.1063/1.1810209

Cited by 13 publications

(10 citation statements)

References 18 publications

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“…[53] KPFM measurements have also been performed on quantum dots, [54,55] quantum wells under illumination, [56] laser diodes, [57] nanotubes, [58,59] and chemically sensitive field-effect transistors. [60] This technique permitted the measurement of the size dependence of the work function for different nanostructures, such as multi-walled nanotubes, [61] and the charging behavior of dots. [55] One of the most promising applications of KPFM is indeed its use on working devices, where the effect of current or light passing through the device can be observed on different areas of the device.…”

Section: Kpfm Of Conventional Inorganic Materialsmentioning

confidence: 99%

Electronic Characterization of Organic Thin Films by Kelvin Probe Force Microscopy

2006

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This review highlights the potential of Kelvin probe force microscopy (KPFM) beyond imaging to simultaneously study structural and electronic properties of functional surfaces and interfaces. This is of paramount importance since it is well established that a solid surface possesses different properties than the bulk material. The versatility of the technique allows one to carry out investigations in a non‐invasive way for different environmental conditions and sample types with resolutions of a few nanometers and some millivolts. KPFM can be used to acquire a wide knowledge of the overall electronic and electrical behavior of a sample surface. Moreover, by KPFM it is possible to study complex electronic phenomena in supramolecular engineered systems and devices. The combination of such a methodology with external stimuli, e.g., light irradiation, opens new doors to the exploration of processes occurring in nature or in artificial complex architectures. Therefore, KPFM is an extremely powerful technique that permits the unraveling of electronic (dynamic) properties of materials, enabling the optimization of the design and performance of new devices based on organic‐semiconductor nanoarchitectures.

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Section: Kpfm Of Conventional Inorganic Materialsmentioning

confidence: 99%

Electronic Characterization of Organic Thin Films by Kelvin Probe Force Microscopy

2006

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“…This fundamental parameter largely reflects electron activities and is directly related to chemical, physical, and mechanical properties of materials [2][3][4][5][6][7][8]. Recent studies have shown that EWF can be used as a sensitive parameter to characterize many surface properties of biomaterials.…”

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confidence: 99%

Electron Work Function–An Effective Parameter for In-situ Reflection of Electron Activities in Various Processes

Li¹

2013

J Biosens Bioelectron

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Electron work function (EWF) is the minimum energy required to move electrons at the Fermi level from inside a conducting material to its surface with zero kinetic energy [1,2]. This fundamental parameter largely reflects electron activities and is directly related to chemical, physical, and mechanical properties of materials [2][3][4][5][6][7][8]. Recent studies have shown that EWF can be used as a sensitive parameter to characterize many surface properties of biomaterials. As an example [9], the affinity of medical implant materials for bacteria can be characterized by EWF. Figure 1A illustrates the adhesive forces of nanocrystalline stainless steel samples with different gran sizes. As shown, as the grain size decreases, the adhesion decreases due to the fact that the passive film becomes more protective, blocking the interaction between the steel and surrounding media. Such a trend is consistent with the variations in electron work function, as shown in Figure 1B. A higher surface EWF corresponds to a higher degree of reluctance for interacting with the environment. The decrease in the number of bacteria bound to the surfaces with an increase in EWF provides direct evidence.Another example is the use of EWF in analyzing the photocatalyical activity of TiO2 nanotubes (TNTs). TNTs have been used for different applications such as DNA biosensor [10], detection of bacteria [11] and toxic compounds [12]. TNTs have also been explored for immobilizing proteins and enzymes in biomaterial and biosensor applications [13,14]. Many of the application are related to the photocatalytic activity of TNTs, which is usually evaluated by variations in photocurrent and absorbance under illumination. However, the photocurrent response or absorbance does not provide sufficient information for full understanding of the photocatalytic behaviour of TNAs.Recent studies have demonstrated that the electron work function is a very sensitive parameter for in-situ analysis of photocatalytic activity of TNTs [15]. Figure 2 illustrates variations in the work function of TiO 2 nanotubes with different tube lengths (corresponding to the anodization duration; the larger the anodization duration, the longer the nanotubes). Figures 2A, C, E and G illustrate variations in EWF of the TNAs illuminated successively by lights having wavelengths of 670 nm, 650 nm, 550 nm, 450 nm, 420 nm, 400 nm and 390 nm. As shown, EWF of the TNAs was relatively stable when they were illuminated by lights of 670 nm and 620 nm, indicating that the photonic energies of the lights are not sufficient to excite electrons in the TNAs. While when the wavelength of incident light is in the absorption range of TNAs lower than 550 nm, electrons can be excited accompanied with an apparent decrease in EWF. The observed decrease in EWF with a decrease in the wavelength of incident light is an indication of photoninduced electron-hole separation, which requires photons with their energy above a certain level.The TNAs were also illuminated successively by the lights with different ...

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“…Addition of charge at the native oxide surface also lowers its surface work function (secondary gate work function ⌽ M2 ), and consequently, V FB2 decreases (by 0.2 eV). 25 However, due to the fact that the charge added to the molecular monolayer is expected to be essentially immobile (it only changes the dipole moment of the molecules), the contribution of the V FB2 term can be ignored in this analysis. The V g2-L term is relevant only when the device is exposed to liquid solutions and will be considered later in the discussion.…”

Section: Resultsmentioning

confidence: 99%

Molecular Sensing Using Monolayer Floating Gate, Fully Depleted SOI MOSFET Acting as an Exponential Transducer

Takulapalli

2010

ACS Nano

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Field-effect transistor-based chemical sensors fall into two broad categories based on the principle of signal transduction-chemiresistor or Schottky-type devices and MOSFET or inversion-type devices. In this paper, we report a new inversion-type device concept-fully depleted exponentially coupled (FDEC) sensor, using molecular monolayer floating gate fully depleted silicon on insulator (SOI) MOSFET. Molecular binding at the chemical-sensitive surface lowers the threshold voltage of the device inversion channel due to a unique capacitive charge-coupling mechanism involving interface defect states, causing an exponential increase in the inversion channel current. This response of the device is in opposite direction when compared to typical MOSFET-type sensors, wherein inversion current decreases in a conventional n-channel sensor device upon addition of negative charge to the chemical-sensitive device surface. The new sensor architecture enables ultrahigh sensitivity along with extraordinary selectivity. We propose the new sensor concept with the aid of analytical equations and present results from our experiments in liquid phase and gas phase to demonstrate the new principle of signal transduction. We present data from numerical simulations to further support our theory.

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Kelvin probe force microscopy as a tool for characterizing chemical sensors

Cited by 13 publications

References 18 publications

Electronic Characterization of Organic Thin Films by Kelvin Probe Force Microscopy

Electronic Characterization of Organic Thin Films by Kelvin Probe Force Microscopy

Electron Work Function–An Effective Parameter for In-situ Reflection of Electron Activities in Various Processes

Molecular Sensing Using Monolayer Floating Gate, Fully Depleted SOI MOSFET Acting as an Exponential Transducer

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