In this investigation properties of organic semiconductor copper phthalocyanine (CuPc) capacitive humidity and illumination sensors were studied. Organic thin film was deposited by vacuum evaporation on a glass substrate with silver surface-type electrodes to form the Ag/CuPc/Ag sensor. The capacitance of the samples was evaluated at room temperature in the relative humidity range of 35-92%. It was observed that capacitance of the Ag/CuPc/Ag sensor increases with increase in humidity. The ratio of the relative capacitance to relative humidity was about 200. It is assumed that in general the capacitive response of the sensor is associated with polarization due to absorption of water molecules and transfer of charges (electrons and holes). It was observed that under filament lamp illumination of up to 1,000 lx the capacitance of the Ag/CuPc/Ag photo capacitive detectors increased continuously by 20% as compared to dark condition. It is assumed that photo capacitive response of the sensor is associated with polarization due to transfer of photo-generated electrons and holes. An equivalent circuit of the Ag/CuPc/Ag capacitive humidity and illumination sensor was developed. Humidity and illumination dependent capacitance properties of this sensor make it attractive for use in humidity and illumination multi-meters. The sensor may be used in instruments for environmental monitoring of humidity and illumination.
Anodic oxide filnls (-1500 A thick) formed on tantalum in saturated H3B03, saturated Na?S04, 86% E13P04, 1% I112S0,,, and 100% HrS04 have been examined by a simple but sensitive glancing angle X-ray technique. They are amorphous as formed but can be crystallized on annealing a t various temperatures between 500 and 1000" C. The times and temperatures required for crystallization depend on the electrolyte used. The crystallization process is competitive with the dissolution of oxygen in the substrate metal. The observed powder diffraction patterns show considerable variation fro111 sample to sample. Similar variations have been reported in the literature for different samples of TaZOe. A structural lllodel is proposed for o-Ta2Oa based on the isostructural relationship with UzOe, whose structure is related to that of a-U03. This proposed structure consists of linear chains of Ta-O-Ta-0-parallel to the c axis with varying disorder in the ab plane. This disorder accounts for the observed variations in the patterns. The proposed structure is a defect one and the ordering of these defects inay account for solnc of the reports of irreversible transformations observed on heating Ta?Oj.
INTRODUCTIOS
In this study, the photocapacitive behavior of organic semiconductor, photosensitive material, poly-Nepoxypropylcarbazole (PEPC) doped with tetracyanoquinodimethane (TCNQ) and copper phthalocyanine (CuPc) were investigated. A sandwich type CG/PEPC-TCNQ/Al photocapacitive detector was fabricated by screen printing technology. Thin films of the copper phthalocyanine (CuPc) were deposited by vacuum evaporation on glass substrates with silver surface-type electrodes and a Ag/CuPc/Ag photo capacitive detector was fabricated. It was shown that under filament lamp illumination up to 2000 lx the capacitance of the CG/PEPC-TCNQ/Al photocapacitive detectors increased up to 5 % with respect to the dark condition . Similarly the capacitance of the Ag/CuPc/Ag photocapacitive detectors increased continuously up to 20 % at 1000 lx relative to the dark condition. It is assumed that photocapacitive response of the detectors is associated with polarization due to the transfer of photogenerated electrons and holes.
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