A novel switchable lowpass filter constructed with electromagnetic bandgap and illumination‐sensitive cadmium sulfide

Wu, J. H. T.; Qiu, S. N.; Qiu, Chun; Shih, I.

doi:10.1002/mop.22665

Micro & Optical Tech Letters

2007

DOI: 10.1002/mop.22665

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A novel switchable lowpass filter constructed with electromagnetic bandgap and illumination‐sensitive cadmium sulfide

J. H. T. Wu

S. N. Qiu

Chun Qiu

et al.

Abstract: A novel construction of microwave switchable lowpass filter based on electromagnetic bandgap (EBG) and cadmium sulfide (CdS) thin film is proposed. Linearly tapered slot‐array EBG structure is well known for its exceptional stopband ability and compact physical size. When the illumination‐sensitive CdS thin film is deposited on the perforations of the EBG structure, the stopband phenomenon induced by tapered slot‐array can be controlled by optical means. Innovative “conductive islands” were introduced to resid… Show more

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2012

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Cited by 2 publications

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“…The interest in semiconducting materials has grown over the past 3 decades due to electro-optical properties that make them suitable for applications in optoelectronic devices, particularly solar cells, 1,2 photodetectors, [3][4][5] and phototransistors 6 . Optically controlled microwave switches, 7 filters, 8 and phase-shifters 9 are being developed with enthusiasm by researchers around the world. When some insulating materials are exposed to visible light, they can exhibit conducting properties similar to metal, which allows them to shield electromagnetic (EM) waves.…”

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confidence: 99%

Photo-Response Switching of Flexible CdS Films Using Visible Light and Electric Field

Hur

Choi

Yoon

et al. 2012

ECS J. Solid State Sci. Technol.

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Shielding and transmission of electro-magnetic waves (8–12 GHz) by visible light was achieved using flexible CdS films grown on a polyethersulfone polymer substrate at room temperature. The photo-resistance of the films was primarily dependent on the intensity of the visible light, and values for dark- and photo-resistance of the films at a visible light intensity of 50,000 lux were approximately 3×104 and 3×102 Ω/square, respectively. When a light-off state was followed by a light-on state, the dark resistance did not fully recover to the original resistance values. The switching characteristics of the CdS films were substantially improved by application of an electric field to the CdS films. The direct current (dc), which flows in CdS films via dc voltage, did not influence the incident electro-magnetic wave of 10 GHz to the CdS films. The dc electric field applied to the CdS films aligned the electrons and improved the collection efficiency after a light-off, resulting in complete recovery of the resistance to its original state.

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mentioning

confidence: 99%

Photo-Response Switching of Flexible CdS Films Using Visible Light and Electric Field

Hur

Choi

Yoon

et al. 2012

ECS J. Solid State Sci. Technol.

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show abstract

“…Optically controlled microwave switches, 1 filters, 2 and phaseshifters 3 using semiconducting materials are being developed with enthusiasm by researchers around the world. When some insulating materials are exposed to visible light, they can exhibit conducting properties similar to metal, which allows them to shield electromagnetic (EM) waves.…”

mentioning

confidence: 99%

Enhancement of the Photo-Response Properties of the Flexible CdS Films by an Application of Electrical Field

Hur

Choi

Yoon

et al. 2012

J. Electrochem. Soc.

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Photo-response switching of the CdS films grown at an optimum condition for the photo-sensor applications was investigated by an application of the electrical field. Recovery to the original dark-resistance after a light-off was achieved for 60 s by an application of the electrical field (∼30 V) in the two electrodes structure. On the other hand, in the structure of three electrodes, after application of −10 V for microsecond at third electrode at a light-off state, the dark-resistance was recovered to its original value for three second. An application of the negative electrical field in the three electrodes structure remarkably improved the switching characteristics of the photo-response of the CdS films.Optically controlled microwave switches, 1 filters, 2 and phaseshifters 3 using semiconducting materials are being developed with enthusiasm by researchers around the world. When some insulating materials are exposed to visible light, they can exhibit conducting properties similar to metal, which allows them to shield electromagnetic (EM) waves. When the light is turned off, if they revert to their original state, they can transmit EM waves effectively. Because both shielding and transmitting of high-frequency EM waves can be conveniently controlled by visible light, these materials can be widely applied for screening EM waves in the GHz frequency range.Photoconductivity by visible light in polycrystalline semiconductor films has been reported by many researchers studying a wide range of materials including amorphous-Si:H, 4, 5 PbTe, 6, 7 ZnO, 8, 9 etc. Cadmium sulfide (CdS), a non-stoichiometric n-type semiconductor with direct band-gap energy of 2.42 eV, exhibited a very high photosensitivity in the visible spectrum. The most improved dark-and photo-sheet resistance values in CdS materials were approximately 5 × 10 12 and ∼10 5 /square, respectively. 10, 11 Recently, to increase the charge carriers in the conduction band of CdS films when exposed to visible light, defects in CdS films grown using various H 2 /(Ar+H 2 ) flow ratios were located within the CdS band-gap, and did not contribute to conduction in a darkened-state. Transformation to a sheet resistance below 50 /square under visible light was accomplished using CdS films grown on flexible polyethersulfon (PES) substrates at room temperature. 12 In the case of polymer substrates, they have many merits compared with those deposited onto glass substrates; they are light weight, of small volume and can make the obtained devices foldable, easy to carry. High conductivity of CdS films was also achieved by controlling the film morphology. However, as far as can be ascertained, the switching property of the photo-response has not been studied in the large area CdS films with a photo-resistance below 200 /square at a visible light. However, for the photo-sensor application, the switching properties of the photo-response should be studied in detail. In the present study, an enhancement of the photoresponse switching of the CdS films was achieved by an applicat...

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A novel switchable lowpass filter constructed with electromagnetic bandgap and illumination‐sensitive cadmium sulfide

Cited by 2 publications

References 11 publications

Photo-Response Switching of Flexible CdS Films Using Visible Light and Electric Field

Photo-Response Switching of Flexible CdS Films Using Visible Light and Electric Field

Enhancement of the Photo-Response Properties of the Flexible CdS Films by an Application of Electrical Field

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