This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine（VOPc） as the active material.The devices,which comprise three different thickne...This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine（VOPc） as the active material.The devices,which comprise three different thicknesses, have been fabricated using the thermal evaporation technique.A thin film of VOPc is deposited on thoroughly cleaned glass substrates with pre-patterned Ag electrodes.The capacitive effect of the samples under humidity has been investigated. Comparison of the samples with different thicknesses shows that the thinnest device seems more sensitive towards humidity.The humidity dependent capacitance properties of the sensor make it beneficial for use in commercial hygrometers.展开更多
A resistive-type relative humidity （RH） sensor based on vanadium complex （VO2（3-f[）） film is reported in this study. Gold electrodes were deposited on the glass substrates in a co-planar structure. A thin film o...A resistive-type relative humidity （RH） sensor based on vanadium complex （VO2（3-f[）） film is reported in this study. Gold electrodes were deposited on the glass substrates in a co-planar structure. A thin film of vanadium complex was coated as a humidity-sensing material on the top of the pre-patterned electrodes. The humidity-sensing principle of the sensor was based on the conductivity change of coated sensing element upon adsorption/desorption of water vapor. The resistance of the humidity sensor measured at 1 kHz decreased linearly with increasing the humidity in the range of 35%-70% RH. The overall resistance of the sensor decreases 11 times. An equivalent circuit for the VO2（3-fl） based resistive-type humidity sensor was developed. The properties of the sensor studied in this work make it beneficial for use in the instruments for environmental monitoring of humidity.展开更多
A thin film of blended poly-N-epoxypropylcarbazole（PEPC）（25 wt.%）,nickel phthalocyanine（NiPc）（50 wt.%） and ZnO nano-powder（25 wt.%） in benzene（5 wt.%） was spin-coated on a glass substrate with silver elect...A thin film of blended poly-N-epoxypropylcarbazole（PEPC）（25 wt.%）,nickel phthalocyanine（NiPc）（50 wt.%） and ZnO nano-powder（25 wt.%） in benzene（5 wt.%） was spin-coated on a glass substrate with silver electrodes to produce a surface-type Ag/PEPC/NiPc/ZnO/Ag capacitive and resistive sensor.Sensors with two different PEPC/NiPc/ZnO film thicknesses（330 and 400 nm） were fabricated and compared.The effects of humidity on capacitance and resistance of the Ag/PEPC/NiPc/ZnO/Ag sensors were investigated at two frequencies of the applied voltage：120 Hz and 1 kHz.It was observed that at 120 Hz under humidity of up to 95%RH the capacitance of the sensors increased by 540 times and resistance decreased by 450 times with respect to humidity conditions of 50%RH. It was found that the sensor with a thinner semiconducting film（330 nm） was more sensitive than the sensor with a thicker film（400 nm）.The sensitivity was improved when the sensor was used at a lower frequency as compared with a high frequency.It is assumed that the humidity response of the sensors is associated with absorption of water vapors and doping of water molecules in the semiconductor blend layer.This had been proven by simulation of the capacitance-humidity relationship.展开更多
A blend of copper oxide nanopowder （Cu2O）, 3 wt.%, and poly-N-epoxypropylcarbazole （PEPC）, 2 wt.%, in benzol was drop-casted on glass substrates with pre-deposited surface-type silver electrodes for the fabricatio...A blend of copper oxide nanopowder （Cu2O）, 3 wt.%, and poly-N-epoxypropylcarbazole （PEPC）, 2 wt.%, in benzol was drop-casted on glass substrates with pre-deposited surface-type silver electrodes for the fabrication of Cu20-PEPC nanocomposite thin films. The thicknesses of the Cu20-PEPC films were in the range of 10-13 μm. The effect of humidity on the electrical properties of the nanocomposite films was investigated by measuring the capacitance and dissipation of the samples at two different frequencies of the applied voltage： 120 Hz and 1 kHz. The AC resistance of the samples was determined from the dissipation values, and the DC resistance was measured directly. The effect of ageing on the humidity sensing properties of the nanocomposite was observed. After ageing, it was observed that at 120 Hz and 1 kHz, under a humidity of up to 86% RH, the capacitance of the cell increased by 85 and 8 times, and the resistance decreased by 345 and 157 times, accordingly, with respect to 30% RH conditions. It was found that with an increase in frequency, the capacitance and resistance of the samples decreased. It is assumed that the humidity response of the cell is associated with the diffusion of water vapors and doping of the semiconductor nanocomposite by water molecules.展开更多
A vanadium complex （VO2（3-fl）） and CNT composite film based temperature sensor is reported in this study. Surface-type silver electrodes were deposited on the glass substrates. A thin film of VOE（3-fl） and CNT c...A vanadium complex （VO2（3-fl）） and CNT composite film based temperature sensor is reported in this study. Surface-type silver electrodes were deposited on the glass substrates. A thin film of VOE（3-fl） and CNT composite was coated as a temperature-sensing material on the top of the pre-patterned Ag electrodes. The temperature-sensing principle of the sensor was based on the conductivity change of the coated sensing element upon heating or cooling processes. DC and AC （100 Hz） resistances of the temperature sensor decreased quasi- linearly with increasing the temperature in the range of 25-80 ℃. The overall resistance of the sensor decreases by 1.8-2.1 and 1.9-2.0 times at DC and AC voltage, respectively. The resistance temperature coefficients of the sensor were in the range of-（0.9-1.3）% and -（1.1-1.3）% at DC and AC voltage, respectively. The properties of the sensor studied in this work, make it beneficial to be used in the instruments for environmental monitoring of temperature.展开更多
Thin films of five vanadium compounds/composite： （1） VO2（3-fl） （3-fl = 3-Hydroxyflavone）, （2） VO（pbd）： （pbd = 1-Phenyl-l, 3-butadione）, （3） VO（dbm）2 （dbm = Dibenzoylmethane）, （4） VPc （Vanadyl Ph...Thin films of five vanadium compounds/composite： （1） VO2（3-fl） （3-fl = 3-Hydroxyflavone）, （2） VO（pbd）： （pbd = 1-Phenyl-l, 3-butadione）, （3） VO（dbm）2 （dbm = Dibenzoylmethane）, （4） VPc （Vanadyl Phthalocyanine） and （5） V2O5-PEPC （V2O5- poly-N-epoxypropylcarbazole composite）, were deposited by the dropcasting method from the solution in benzene. The transmittance-irradiance relationships were investigated and the transmission in the visible spectrum and optical images were obtained as well. It was found that the transmittance of the VO2（3-fl）, VO（pbd）2, VO（dbm）2 and VPc, was practically independent of the irradiance; whereas the transmittance of V2O5-PEPC decreased by 4% for thin and 9% for thick films with an increase of the irradiance.展开更多
This paper throws light on the preparation of transition metal-doped Mg_(0.5)Zn_(0.5)Al_(2)O_(4)(x=0,0.05 and TM=Co,Ni,Cu)aluminates via solid-state reaction route.The X-ray diffraction characterization analysis confi...This paper throws light on the preparation of transition metal-doped Mg_(0.5)Zn_(0.5)Al_(2)O_(4)(x=0,0.05 and TM=Co,Ni,Cu)aluminates via solid-state reaction route.The X-ray diffraction characterization analysis confirmed that all the samples have crystallized into the psuedocubic phase having space group Fd3m and were single phased.The incorporation of transition metals viz.Co^(2+),Ni^(2+),Cu^(2+)in the Mg_(0.5)Zn_(0.5)Al_(2)O_(4)matrix does not result in the appearance of new peaks or any considerable shift in diffraction peaks within the limits of XRD experimentation.This infers homogeneous dispersion of dopants at the Mg-site which is attributed to nearly same ionic radii of the dopants to that of Mg-site in Mg 0:5 Zn0:5 Al 2 O 4.Lattice structure,bonding nature and hence the spinel formation were verified through Raman scattering technique.The compositional verification was carried out via energy dispersive analysis of X-rays(EDAX).The surface morphology and hence the microstructural studies were carried out using field emission scanning electron microscopy(FESEM).The synthesized Mg_(0.5)Zn_(0.5)Al_(2)O_(4)(x=0,0.05 and TM=Co,Ni,Cu)aluminate samples were tested for polarization studies keeping their insulating nature into consideration and they displayed a sign of well-behaved P-E loop.展开更多
The preparation of La_(0.9)Na_(0.1)CrO_(3)(LNCO),Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)(NCFO)and their composites of the type e1xT La_(0.9)Na_(0.1)CrO_(3)(LNCO)t(x)Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)(NCFO)ex?0.25,0.50T through solid st...The preparation of La_(0.9)Na_(0.1)CrO_(3)(LNCO),Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)(NCFO)and their composites of the type e1xT La_(0.9)Na_(0.1)CrO_(3)(LNCO)t(x)Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)(NCFO)ex?0.25,0.50T through solid state route is reported.From X-ray diffraction data analysis,the parent La_(0.9)Na_(0.1)CrO_(3)was found to crystallize in orthorhombic structure(Pnma)while Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)has crystallized into the cubic structure(Fd3m)further verified via Retvield refinement.The morphology and compositional studies were carried out using field emission scanning electron microscopy(FESEM)and energy dispersive analysis of X-rays(EDAX),respectively.Lattice structure was confirmed via Raman characterization for the prepared samples.The sample formation was further verified through Fourier transform Infra-Red(FTIR)spectroscopy.The dielectric studies reveal the La_(0.9)Na_(0.1)CrO_(3)e13*10^(4)T and Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)e1.83*10^(4)T exhibit high dielectric constant.However,their composites show abrupt drop in dielectric constant.The electric modulus study confirmed that the samples exhibit non-Debye character with spread of relaxation time constants.展开更多
Au/cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole （PEPC） blend thin films. A blend of 2wt% of each cellulose and PEPC in benzol was used for...Au/cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole （PEPC） blend thin films. A blend of 2wt% of each cellulose and PEPC in benzol was used for the deposition of humidity sensing films. Blend films were deposited on glass substrates with preliminary deposited surface-type gold electrodes. Films of different thicknesses of cellulose and PEPC composite were deposited by drop-casting technique. A change in electrical resistance and capacitance of the fabricated devices was observed by increasing the relative humidity in the range of 0-95% RH. It was observed that the capacitances of the sensors increase, while their resistances decrease with increasing the relative humidity. The sensors were connected to op-amp square wave oscillators. It was observed that with increasing the relative humidity, the oscillator＇s frequencies were also increased in the range of 4.2-12.0 kHz for 65μm thick film sample, 4.1-9.0 kHz for 88μm thick film sample, and 4.2-9.0 kHz for 210μm sample. Effects of film thickness on the oscillator＇s frequency with respect to humidity were also investigated. This polymer humidity sensor controlled oscillator can be used for short-range and long-range remote systems at environmental monitoring and assessment of the humidity level.展开更多
文摘This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine（VOPc） as the active material.The devices,which comprise three different thicknesses, have been fabricated using the thermal evaporation technique.A thin film of VOPc is deposited on thoroughly cleaned glass substrates with pre-patterned Ag electrodes.The capacitive effect of the samples under humidity has been investigated. Comparison of the samples with different thicknesses shows that the thinnest device seems more sensitive towards humidity.The humidity dependent capacitance properties of the sensor make it beneficial for use in commercial hygrometers.
基金support of Ghulam Ishaq Khan Institute of Engineering Sciences and Technology
文摘A resistive-type relative humidity （RH） sensor based on vanadium complex （VO2（3-f[）） film is reported in this study. Gold electrodes were deposited on the glass substrates in a co-planar structure. A thin film of vanadium complex was coated as a humidity-sensing material on the top of the pre-patterned electrodes. The humidity-sensing principle of the sensor was based on the conductivity change of coated sensing element upon adsorption/desorption of water vapor. The resistance of the humidity sensor measured at 1 kHz decreased linearly with increasing the humidity in the range of 35%-70% RH. The overall resistance of the sensor decreases 11 times. An equivalent circuit for the VO2（3-fl） based resistive-type humidity sensor was developed. The properties of the sensor studied in this work make it beneficial for use in the instruments for environmental monitoring of humidity.
文摘A thin film of blended poly-N-epoxypropylcarbazole（PEPC）（25 wt.%）,nickel phthalocyanine（NiPc）（50 wt.%） and ZnO nano-powder（25 wt.%） in benzene（5 wt.%） was spin-coated on a glass substrate with silver electrodes to produce a surface-type Ag/PEPC/NiPc/ZnO/Ag capacitive and resistive sensor.Sensors with two different PEPC/NiPc/ZnO film thicknesses（330 and 400 nm） were fabricated and compared.The effects of humidity on capacitance and resistance of the Ag/PEPC/NiPc/ZnO/Ag sensors were investigated at two frequencies of the applied voltage：120 Hz and 1 kHz.It was observed that at 120 Hz under humidity of up to 95%RH the capacitance of the sensors increased by 540 times and resistance decreased by 450 times with respect to humidity conditions of 50%RH. It was found that the sensor with a thinner semiconducting film（330 nm） was more sensitive than the sensor with a thicker film（400 nm）.The sensitivity was improved when the sensor was used at a lower frequency as compared with a high frequency.It is assumed that the humidity response of the sensors is associated with absorption of water vapors and doping of water molecules in the semiconductor blend layer.This had been proven by simulation of the capacitance-humidity relationship.
基金the GIK Institute of Engineering Sciences and Technology for its support in this work
文摘A blend of copper oxide nanopowder （Cu2O）, 3 wt.%, and poly-N-epoxypropylcarbazole （PEPC）, 2 wt.%, in benzol was drop-casted on glass substrates with pre-deposited surface-type silver electrodes for the fabrication of Cu20-PEPC nanocomposite thin films. The thicknesses of the Cu20-PEPC films were in the range of 10-13 μm. The effect of humidity on the electrical properties of the nanocomposite films was investigated by measuring the capacitance and dissipation of the samples at two different frequencies of the applied voltage： 120 Hz and 1 kHz. The AC resistance of the samples was determined from the dissipation values, and the DC resistance was measured directly. The effect of ageing on the humidity sensing properties of the nanocomposite was observed. After ageing, it was observed that at 120 Hz and 1 kHz, under a humidity of up to 86% RH, the capacitance of the cell increased by 85 and 8 times, and the resistance decreased by 345 and 157 times, accordingly, with respect to 30% RH conditions. It was found that with an increase in frequency, the capacitance and resistance of the samples decreased. It is assumed that the humidity response of the cell is associated with the diffusion of water vapors and doping of the semiconductor nanocomposite by water molecules.
基金the GIK Institute of Engineering Sciences and Technology for its support of this work
文摘A vanadium complex （VO2（3-fl）） and CNT composite film based temperature sensor is reported in this study. Surface-type silver electrodes were deposited on the glass substrates. A thin film of VOE（3-fl） and CNT composite was coated as a temperature-sensing material on the top of the pre-patterned Ag electrodes. The temperature-sensing principle of the sensor was based on the conductivity change of the coated sensing element upon heating or cooling processes. DC and AC （100 Hz） resistances of the temperature sensor decreased quasi- linearly with increasing the temperature in the range of 25-80 ℃. The overall resistance of the sensor decreases by 1.8-2.1 and 1.9-2.0 times at DC and AC voltage, respectively. The resistance temperature coefficients of the sensor were in the range of-（0.9-1.3）% and -（1.1-1.3）% at DC and AC voltage, respectively. The properties of the sensor studied in this work, make it beneficial to be used in the instruments for environmental monitoring of temperature.
文摘Thin films of five vanadium compounds/composite： （1） VO2（3-fl） （3-fl = 3-Hydroxyflavone）, （2） VO（pbd）： （pbd = 1-Phenyl-l, 3-butadione）, （3） VO（dbm）2 （dbm = Dibenzoylmethane）, （4） VPc （Vanadyl Phthalocyanine） and （5） V2O5-PEPC （V2O5- poly-N-epoxypropylcarbazole composite）, were deposited by the dropcasting method from the solution in benzene. The transmittance-irradiance relationships were investigated and the transmission in the visible spectrum and optical images were obtained as well. It was found that the transmittance of the VO2（3-fl）, VO（pbd）2, VO（dbm）2 and VPc, was practically independent of the irradiance; whereas the transmittance of V2O5-PEPC decreased by 4% for thin and 9% for thick films with an increase of the irradiance.
文摘This paper throws light on the preparation of transition metal-doped Mg_(0.5)Zn_(0.5)Al_(2)O_(4)(x=0,0.05 and TM=Co,Ni,Cu)aluminates via solid-state reaction route.The X-ray diffraction characterization analysis confirmed that all the samples have crystallized into the psuedocubic phase having space group Fd3m and were single phased.The incorporation of transition metals viz.Co^(2+),Ni^(2+),Cu^(2+)in the Mg_(0.5)Zn_(0.5)Al_(2)O_(4)matrix does not result in the appearance of new peaks or any considerable shift in diffraction peaks within the limits of XRD experimentation.This infers homogeneous dispersion of dopants at the Mg-site which is attributed to nearly same ionic radii of the dopants to that of Mg-site in Mg 0:5 Zn0:5 Al 2 O 4.Lattice structure,bonding nature and hence the spinel formation were verified through Raman scattering technique.The compositional verification was carried out via energy dispersive analysis of X-rays(EDAX).The surface morphology and hence the microstructural studies were carried out using field emission scanning electron microscopy(FESEM).The synthesized Mg_(0.5)Zn_(0.5)Al_(2)O_(4)(x=0,0.05 and TM=Co,Ni,Cu)aluminate samples were tested for polarization studies keeping their insulating nature into consideration and they displayed a sign of well-behaved P-E loop.
文摘The preparation of La_(0.9)Na_(0.1)CrO_(3)(LNCO),Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)(NCFO)and their composites of the type e1xT La_(0.9)Na_(0.1)CrO_(3)(LNCO)t(x)Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)(NCFO)ex?0.25,0.50T through solid state route is reported.From X-ray diffraction data analysis,the parent La_(0.9)Na_(0.1)CrO_(3)was found to crystallize in orthorhombic structure(Pnma)while Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)has crystallized into the cubic structure(Fd3m)further verified via Retvield refinement.The morphology and compositional studies were carried out using field emission scanning electron microscopy(FESEM)and energy dispersive analysis of X-rays(EDAX),respectively.Lattice structure was confirmed via Raman characterization for the prepared samples.The sample formation was further verified through Fourier transform Infra-Red(FTIR)spectroscopy.The dielectric studies reveal the La_(0.9)Na_(0.1)CrO_(3)e13*10^(4)T and Ni_(0.5)Cu_(0.5)Fe_(2)O_(4)e1.83*10^(4)T exhibit high dielectric constant.However,their composites show abrupt drop in dielectric constant.The electric modulus study confirmed that the samples exhibit non-Debye character with spread of relaxation time constants.
基金GIK Institute of Engineering Sciences and Technology for the support extended to this work
文摘Au/cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole （PEPC） blend thin films. A blend of 2wt% of each cellulose and PEPC in benzol was used for the deposition of humidity sensing films. Blend films were deposited on glass substrates with preliminary deposited surface-type gold electrodes. Films of different thicknesses of cellulose and PEPC composite were deposited by drop-casting technique. A change in electrical resistance and capacitance of the fabricated devices was observed by increasing the relative humidity in the range of 0-95% RH. It was observed that the capacitances of the sensors increase, while their resistances decrease with increasing the relative humidity. The sensors were connected to op-amp square wave oscillators. It was observed that with increasing the relative humidity, the oscillator＇s frequencies were also increased in the range of 4.2-12.0 kHz for 65μm thick film sample, 4.1-9.0 kHz for 88μm thick film sample, and 4.2-9.0 kHz for 210μm sample. Effects of film thickness on the oscillator＇s frequency with respect to humidity were also investigated. This polymer humidity sensor controlled oscillator can be used for short-range and long-range remote systems at environmental monitoring and assessment of the humidity level.
