Muhammad Hassan Sayyad

Characterization of vanadyl phthalocyanine based surface-type capacitive humidity sensors

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.

Extreme-ultraviolet studies with laser-produced plasmas

A new multilaser multichannel spectrometer system has been developed that allows a wide range of investigations of the interaction of extreme-ultraviolet (EUV) photons with matter in the form of free atoms or ions, e.g., in gases or plasmas or bound as in solids. The EUV photons are generated by a laser-produced plasma. Applications to the study of photoabsorption by thin foils, gases, and ground- and excited-state atoms and ions are described. The design and performance of a collimated, quasi-monochromatic, intense source of EUV radiation based on the combination of a laser-produced plasma with a EUV multilayer mirror is also reported.

Electrical characterization of the organic semiconductor Ag/CuPc/Au Schottky diode

This paper reports on the fabrication and investigation of a surface-type organic semiconductor copper phthalocyanine (CuPc) based diode. A thin film of CuPc of thickness 100 nm was thermally sublimed onto a glass substrate with preliminary deposited metallic electrodes to form a surface-type Ag/CuPc/Au Schottky diode. The current-voltage characteristics were measured at room temperature under dark conditions. The barrier height was calculated as 1.05 eV The values of mobility and conductivity was found to be 1.74 × 10−9 cm2 (V · s) and 5.5 × 10−6 Ω−1 · cm−1, respectively. At low voltages the device showed ohmic conduction and the space charge limited current conduction mechanisms were dominated at higher voltages.

Electrical characterization of the ITO/NiPc/PEDOT: PSS junction diode

This paper reports on the fabrication and characterization of an ITO/NiPc/PEDOT?:?PSS junction diode. A thin film of nickel phthalocyanine (NiPc) was deposited by the thermal vacuum deposition method on indium tin oxide (ITO) used as a substrate. The current?voltage characteristics of the diode were measured at room temperature under dark condition and showed rectifying behaviour. The values of several electrical parameters such as ideality factor, barrier height, conductivity, and series and shunt resistances were calculated.

Photo-organic field effect transistor based on a metalloporphyrin

We report the effect of light on the output characteristics of the organic field effect transistor fabricated by using the 5,10,15,20-Tetrakis(3 � ,5 � -di-tertbutylphenyl)porphyrinatocopper(II) (TDTPPCu) as a channel material and demonstrate light for controlling the drain‐source current instead of the gate voltage. Upon illumination, a detectable change in the drain‐source current was observed.

Investigation of Optical and Humidity-Sensing Properties of Vanadyl Phthalocyanine-Derivative Thin Films

In this study an active layer of Vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO) has been employed in surface type humidity sensor. On top of preliminary deposited asymmetric metal electrodes, a VOPcPhO thin film was spun cast to obtain a surface type Al/VOPcPhO/Au sensor. The gap between the electrodes was 40 um. A solution of 30 mg/ml was deposited at 3000 rpm. The thickness of the VOPcPhO film was 150 nm. The capacitive effect of the sample was evaluated in the relative humidity range 0–87%RH, at room temperature. It was observed that the capacitance of the sensor increases 10 times under the effect of entire humidity range in the relative humidity level. The optical properties of VOPcPhO thin film were also investigated. The humidity-dependent capacitive properties make the sensor suitable for the application in the instruments used for environmental monitoring of humidity.

ENHANCEMENT IN THE SENSING PROPERTIES OF METHYL ORANGE THIN FILM BY TiO2 NANOPARTICLES

This paper reports the enhancement in the sensing properties of organic dye methyl orange (MO) by introducing TiO2 nanoparticles. For this purpose, two surface type Ag/MO/Ag and Ag/MO:TiO2/Ag multifunctional sensors were fabricated by spin coating a 3.0 wt.% solution of MO and 3.0:0.3 wt.% of MO:TiO2 composite on pre-patterned silver (Ag) electrodes. The gap between Ag electrodes was 40 μm. The Ag/MO/Ag and Ag/MO:TiO2/Ag structures were characterized to investigate their response towards humidity and temperature variations. The Ag/MO:TiO2/Ag sensor exhibited better sensitivity and response time than Ag/MO/Ag sensor. The large surface to volume ratio of TiO2 nanoparticles is the primary reason for the higher sensitivity of Ag/MO:TiO2/Ag sensor. The sensors can be used to detect humidity variations from 30% to 95% RH and temperature variation from 30°C to 200°C with good stability. Surface morphologies of the film were investigated by scanning electron microscope (SEM).

Organic semiconductor nickel phthalocyanine-based photocapacitive and photoresistive detector

In this study, the photosensitive organic semiconductor nickel phthalocyanine (NiPc) is investigated as a photocapacitive and photoresistive detector. NiPc thin film is grown by vacuum thermal evaporation on an indium tin oxide (ITO)-coated glass substrate. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is deposited as a top electrode by drop-casting to fabricate the ITO/NiPc/PEDOT:PSS light detector. It has been observed that under the unmodulated filament lamp illumination of up to 9720 lux the capacitance of the detectors increased up to 21, 18 and 4% at a frequency of measuring voltage of 120 Hz, 1 kHz and 10 kHz, respectively, under dark conditions. The change in resistance with the variation in the intensity of light is also investigated. The capacitance and resistance of the light detector decrease with an increase in the frequency. It is assumed that the photocapacitive and photoresistive response of the detector is associated with polarization occurring due to the transfer of photo-generated electrons and holes. The calculated results are in reasonable agreement with the experimental results.

Dye-Sensitized Solar Cells Based on Porous Hollow Tin Oxide Nanofibers

Porous hollow tin oxide (SnO2) nanofibers and their composite with titanium dioxide (TiO2) particles (Degussa P25) were investigated as a photoanode for dye-sensitized solar cells. Incorporation of TiO2 particles in porous hollow SnO2 fibers enhanced the power conversion efficiency (η) from 4.06% to 5.72% under 100-mW/cm2 light intensity. The enhancement of efficiency was mainly attributed to increase in current density (Jsc) and improvement in fill factor (FF). Increase in Jsc was caused by higher dye loading as indicated by UV-Vis absorption spectra and the improvement in FF was attributed to faster charge transport time as obtained from transient analysis. The microstructure of SnO2 fibers was studied using transmission electron microscope, scanning electron microscope, and X-ray diffraction. The electron transfer and recombination life times were studied using transient analysis, whereas interfacial charge transfer was studied using electrochemical impedance spectroscopy.

Electrical Characteristics of A1/CNT/NiPc/PEPC/Ag Surface-Type Cell

The blend of nickel phthalocyanine (NiPc) (2 wt. %) poly-N-epoxypropylcarbazole (PEPC), (1 wt. %) and carbon nano-tube (CNT) powder (2 wt. %) in benzole is deposited by drop-casting on glass substrates with pre-deposited metallic electrodes to fabricate Ag/CNT/NiPc/PEPC/A1 surface type cell. It is assumed that the high nonlinearity of the I — V characteristics is related to deep traps in the nano-scale depletion region in NiPc that is observed experimentally. The values of ideality factor and barrier height are determined from the I — V curve and they are found to be 8.4 and 1.05eV, respectively. The values of mobility and conductivity are calculated to be 7.94 × 10−8 cm/Vs and 3.5 × 10−6 Ω−1 cm−1. The values of ideality factor and series resistance are also calculated by using Cheungs functions, which are in good agreement with the values calculated from the I — V curve.