Investigation of the spatial resolution of the light-addressable potentiometric sensor

George, Michael; Parak, Wolfgang J.; Gerhardt, Ilja; Moritz, W.; Kaesen, F; Geiger, H.; Eisele, I.; Gaub, Hermann E.

doi:10.1016/s0924-4247(00)00455-6

Cited by 67 publications

(51 citation statements)

References 14 publications

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“…SOI substrates with a 7 m thick silicon layer were shown to have an effective diffusion length of charge carriers of about 13 m. The diffusion length in an SOS substrate with a 1 m thick silicon layer was found to be close to 0.6 m. This indicates that SPIM measurements with submicrometer resolution are possible using a high quality optical setup. Considering that George et al predicted a linear relationship between the thickness of the silicon layer and the resolution of photocurrent measurements, the difference found between SOI and SOS substrates was greater than expected [13]. This may be due to the fact that the silicon layer in case of SOS was not only thinner but also had a higher doping concentration, which is also known to improve the resolution [13].…”

Section: Discussionmentioning

confidence: 84%

“…Considering that George et al predicted a linear relationship between the thickness of the silicon layer and the resolution of photocurrent measurements, the difference found between SOI and SOS substrates was greater than expected [13]. This may be due to the fact that the silicon layer in case of SOS was not only thinner but also had a higher doping concentration, which is also known to improve the resolution [13].…”

Section: Discussionmentioning

confidence: 84%

“…Theoretical considerations and experimental results described in the literature suggest that the resolution of photocurrent measurements is closely related to the thickness of the silicon [12,13]. Nakao et al achieved a resolution of about 10 m for LAPS using a 20 m thick silicon substrate [12].…”

Section: Resolution Of Spimmentioning

confidence: 99%

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Scanning Photo-Induced Impedance Microscopy—Resolution studies and polymer characterization

Krause

Moritz

Talabani

et al. 2006

Electrochimica Acta

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Scanning Photo-Induced Impedance Microscopy (SPIM) is an impedance imaging technique that is based on photocurrent measurements at field-effect structures. The material under investigation is deposited onto a semiconductor-insulator substrate. A thin metal film or an electrolyte solution with an immersed electrode serves as the gate contact. A modulated light beam focused into the space charge region of the semiconductor produces a photocurrent, which is directly related to the local impedance of the material. The absolute impedance of a polymer film can be measured by calibrating photocurrents using a known impedance in series with the sample.Depending on the wavelength of light used, charge carriers are not only generated in the focus but also throughout the bulk of the semiconductor. This can have adverse effects on the lateral resolution. Two-photon experiments were carried out to confine charge carrier generation to the space charge layer. The lateral resolution of SPIM is also limited by the lateral diffusion of charge carriers in the semiconductor. This problem can be solved by using thin silicon layers as semiconductor substrates. A resolution of better than 1 m was achieved using silicon on sapphire (SOS) substrates with a 1 m thick silicon layer.

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Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 84%

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Scanning Photo-Induced Impedance Microscopy—Resolution studies and polymer characterization

Krause

Moritz

Talabani

et al. 2006

Electrochimica Acta

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“…For p-type silicon, electrons, the minority carriers, are important for the photocurrent in the reversed bias regimen. The spatial extent of the cloud of free electrons photogenerated in semiconductor is determined by the minority carrier lifetime and diffusion coefficient and could be on the order of 100 m in our case (George et al 2000). If there were low-resistivity cross-interface pathways due to, for example, microscopic holes in the glial layer, most of the electric current would "escape" through such pathways found in a 100-m radius around the illuminated location, and only the pathways traversed by the neurites of the patched cell would have a stimulating effect.…”

Section: Discussionmentioning

confidence: 90%

Light-Directed Electrical Stimulation of Neurons Cultured on Silicon Wafers

Starovoytov¹,

Choi²,

Seung³

2005

Journal of Neurophysiology

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. Lightdirected electrical stimulation of neurons cultured on silicon wafers. J Neurophysiol 93: 1090 -1098, 2005. First published September 22, 2004 doi:10.1152/jn.00836.2004. Dissociated neurons cultured in vitro can serve as a model system for studying the dynamics of neural networks. Such studies depend on techniques for stimulating patterns of neural activity. We show a technique for extracellular stimulation of dissociated neurons cultured on silicon wafers. When the silicon surface is reverse biased, electrical current can be generated near any neuron by pulsing a laser. Complex spatiotemporal stimulation patterns can be produced by directing a single beam with an acousto-optic deflector. The technique can generate a stimulating current at any location in the culture. This contrasts with multielectrode arrays (MEAs), which can stimulate only at fixed electrode locations. To characterize reliability and spatial selectivity of stimulation, we used intracellular (patch-clamp) recordings to monitor the effect of targeted laser pulses on cultured hippocampal neurons. Action potentials could be stimulated with submillisecond precision and 100-micron spatial resolution at rates exceeding 100 Hz. Optimal control parameters for stimulation are discussed.

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“…It limits the density of measuring points on the multisensor surface and the smallest size of structures that can be visualized by the chemical imaging sensor. It has been demonstrated both experimentally and theoretically [8][9][10] that the spatial resolution is determined by the beam size and the lateral diffusion of photocarriers in the semiconductor substrate. With appropriate focusing optics, the beam size can be reduced down to the scale of 1 µm or the wavelength of the light.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Thin-Film LAPS with Amorphous Silicon

Yoshinobu

Schöning

Finger³

et al. 2004

Sensors

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Abstract:To improve the spatial resolution of the light-addressable potentiometric sensor (LAPS), it is necessary to reduce the thickness of the semiconductor layer, which, however, causes a problem of the mechanical strength of the sensor plate. In this study, a thin-film LAPS was fabricated with amorphous silicon (a-Si) deposited on a transparent glass substrate. The current-voltage characteristics and pH sensitivity of the fabricated a-Si LAPS were investigated.

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Investigation of the spatial resolution of the light-addressable potentiometric sensor

Cited by 67 publications

References 14 publications

Scanning Photo-Induced Impedance Microscopy—Resolution studies and polymer characterization

Scanning Photo-Induced Impedance Microscopy—Resolution studies and polymer characterization

Light-Directed Electrical Stimulation of Neurons Cultured on Silicon Wafers

Fabrication of Thin-Film LAPS with Amorphous Silicon

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