Photo Resistance Research Articles

Influence of deposition temperature on the defect mediated persistence photo-conducting behaviour of spray coated Zn0.96Nd0.04O thin films

The incorporation of Neodymium into ZnO lattice enhances the photo conducting property of the deposited films which are strongly dependent on preparation conditions. Hence, the comprehensive work carried out to understand the influence of deposition temperature (300 °C–500 °C) on the persistence photoconductivity of Zn0.96Nd0.04O films deposited on glass substrates using spray pyrolysis method. The maximum crystallite size of ∼16.3 nm with minimum dislocation density and strain values were noticed for the films deposited at 450 °C. The mixed fibrous -granular morphology was noticed in the deposited films. The maximum transparency above 90 % in the visible region and an increased bandgap of 3.42 eV was observed in the films deposited at 450 °C. The percentage of defects were calculated using the area under the curve of photoluminescence spectra. The charge carrier density of 1.7 × 1017 cm−3, mobility of 62.8 cm2/Vs and lesser resistivity of 1.3 × 102 Ω cm were noted for the films deposited at 450 °C. Under the illumination of UV light, the photocurrent of Zn0.96Nd0.04O films deposited at 450 °C increased by four orders. The persistence in the photo resistance was due to the presence of Zn and O related defects, which acts as trap centres. The variation of photo resistance with time indicates the films deposited at 450 °C has faster photo response due to the faster electron – hole recombination process. The maximum photocurrent at 360 nm was noted for the films synthesized at 450 °C due to improved crystallinity with stoichiometry nature of the films. Hence, the Zn0.96Nd0.04O films deposited at 450 °C suitable for light dependent resistor and fixed wavelength UV photodetector applications.

Effect of incorporating graphene oxide in ZnS and study of the thermistor applications of ZnS-RGO film

We report the effect of incorporating graphene oxide in ZnS and developed a ZnS-RGO hybrid film with negative temperature coefficient (NTC) for thermistor application towards temperature sensing in this study. The light sensing properties of the films were also investigated by exposing the film to light sources from mercury and tungsten lamp and recording the photo resistance. As the composition of ZnS in ZnS-RGO increased, sharper diffraction peaks were observed thus confirming improved crystallinity. The crystallite size of ZnS-RGO hybrid decreased from 4.02 to 1.87 nm while the lattice strain increased from 0.0086 to 0.0185 as the composition of ZnS in the hybrid increased. ZnS-RGO recorded a maximum sensor response of 1.91 which is approximately twice the maximum value obtained for pure ZnS in literature. The negative temperature coefficient (NTC) for ZnS-RGO (0.00174825/K) was higher than values obtained in literature for ZnS and Ag nanoparticles coated RGO. Furthermore, the sensitivity value of ZnS-RGO (0.00769 Ω/ K) was five times that of ZnS while the activation energy (0.0352 eV) was about seven times the value reported for ZnS. The increase in activation energy of ZnS-RGO compared to ZnS is responsible for the improved sensing response of the hybrid while the intercalation of ZnS in GO created reactive sites that resulted in activation energy, sensing response and an NTC much higher than in pure ZnS thus favoring utilization of ZnS-RGO as thermistors. This research has shown that ZnS, intercalated in the matrix of GO improved the thermal and photo sensing properties of ZnS and is thus suitable in thermistor applications. These properties can be used to suggest the application of ZnS-RGO in optoelectronic applications such as EM detectors, solar cells and temperature monitoring devices.

Ultraviolet photoconductivity and photoluminescence properties of spray pyrolyzed ZnO nanostructure: Effect of deposition temperature

The current investigation focuses on the influence of substrate temperature on Zinc Oxide (ZnO) thin films synthesized on glass substrates using 0.1 M precursor solution by low-cost spray pyrolysis technique. The x-ray diffraction peaks matched the hexagonal wurtzite structure of ZnO with the highest intensity along the (1 0 1) plane. Estimated the crystallite size, dislocation density, micro-strain, and the number of crystallites in the deposits using X ray diffraction (XRD) data. The crystallinity of the films deposited at 450 °C was maximum. Fibrous surface morphology is altered by varying the deposition temperature. The enhancement of optical transmittance and energy bandgap of the deposits with deposition temperature. The reduction of Urbach energy with an increase in the substrate temperature confirmed the improvement of crystallinity. The photoluminescence study revealed peaks associated with electron-hole pair recombination, zinc, and oxygen-related defects. The samples deposited at 450 °C showed minimum defects. Commission Internationale de l'éclairage (CIE) chromaticity diagram showed white light emission for sample deposited at 450 °C with the color temperature equal to 5378 °C which is agreeing with the temperature of a normal white light source. Improvement of free carrier concentration and n-type conductivity due to the enhancement of crystallinity was observed. ZnO thin films deposited at 450 °C showed maximum photocurrent when illuminated with UV light and faster rise and fall of photo resistance due to the improvement in the crystallinity and carrier concentration. The maximum photosensitivity was observed for the samples synthesized at 450 °C. Hence the ZnO thin films deposited at 450 °C can be used as ultraviolet photodetector material.

Photoconductivity study of ZnxS1-x thin film using multiple light sources

ABSTRACT This research studied the photoconductivity of zinc sulfide thin film using multiple light sources and investigated the thermal sensing performance. Zinc sulfide with high degree sulfur vacancies was spin coated on glass and the film illuminated with light from mercury, tungsten and sodium lamp. The photo resistance value between 250 and 750 nm was obtained. High strain value obtained for the particles shows that the film is defect enriched while a steady increase in photoresistance from the UV to the visible spectrum was observed in all three lamps. However, tungsten lamp showed lower photoresistance values compared to other lamps. The photoconductivity measurements disclose a band gap of between 1.77 and 2.50 eV depending on the lamp used and reveal that the photoconductivity is controlled by boundaries of vacancies in the material. The lamps were used as photo analyzers and showed that ZnS may function as UV detectors in opto-electronic applications.

Investigation of the thermal and light sensing properties of graphene oxide and reduced graphene oxide films obtained by spin coating method

This paper reported the thermal and light sensing properties of graphene oxide (GO) and reduced graphene oxide (RGO) films obtained by spin coating on soda lime glass. GO showed a higher thermal sensing response of 9.0 compared to RGO which had a maximum thermal sensing response of 2.2 at 623 K. The thermal conductivity of GO and RGO increased with temperature although RGO typified better thermal conductivity. For GO, a negative temperature coefficient of resistance (NTC) of 0.0032153 /K was obtained which is higher than values obtained in literatures while RGO had a NTC value of 0.00201/K. For the photo sensing, the peak photo resistance of GO corresponds to an energy band gap of 3.5 eV while the peak photo resistance of RGO corresponds to a decreased energy band gap of 2.76 eV. It was also confirmed that lower bandgap favored improved photosensing function. RGO film showed intrinsic photoconductivity as the photoconductivity increased at longer wavelengths. The photo sensing of GO and RGO were dominated by inter-band optical transitions in the UV to mid infrared region. The obtained NTC values for GO and RGO and the photoconductivity of the materials can promote further utilization in robotics and optical applications.

Field effects on heterojunctions composed with electron-doped La1−xHfxMnO3and Nb-SrTiO3perovskites

Thin films and heterojunctions of Hf[Formula: see text]-doped LaMnO3manganite have been studied. The sole tetravalent state of Hf[Formula: see text] ensures formation of [Formula: see text]-type La[Formula: see text]Hf[Formula: see text]MnO3(LHMO) manganite. Photoinduced resistance was also observed as illuminated by visible light. The induced photoresistance (PR) could be greatly enhanced by the compressive strain. The LHMO/Nb-STO heterojunctions showed excellent rectifying characteristics, which are comparable with those [Formula: see text]-junctions of conventional semiconductors. Their transport properties are tunable electrically and magnetically. Such LHMO/Nb-STO heterojunctions have the potential to develop novel functional field-effect transistors based on manganite perovskites.

The Application of Sliding Mode Control of a Speed Induction Motor Pump using FPGA

Objectives: This paper shows the efficiency of using a sliding mode control of a photovoltaic pumping system, which is strongly non-linear. It contains several non-linear sub-systems (photovoltaic generator, DC/AC converter, an asynchronous three phase motor-pump, centrifugal pumps and two coupled tanks). The mathematical model of the whole system was achieved after the modeling of the various parts constituting it. Furthermore, an FPGA implementation on the map Xilinx Spartan 3A was performed to prove the effectiveness of the proposed sliding mode control of the motor-pump angular speed. Methods/Statistical analysis: The values of the irradiance and the temperature were respectively measured by the sensors (photo resistance and LM35). They vary according to the climatic conditions that change permanently during the year. Experimental results are compared with those obtained in Matlab. Findings: The motor-pump speed reached its maximum value when the irradiance is maximal. Likewise, a low irradiance allows a low speed. The FPGA board is responsible for finding the suitable frequency according to the instantaneous irradiance. This frequency will be the reference in the scalar control implemented on the DV51, which powers the motor-pump. Hence, we have carried out a real-time control according to the climatic conditions. Application/Improvements: Pumping is an alternative way of managing water resources in different areas (surface water, groundwater, desalination, agricultural use or industry).In the future work; we can control the water levels in the coupled tanks.

The Mechanism of the Bridge Defect Caused By the Reaction with the Dispersant Polymer in Slurry and the Double Patterning Photo Layer

At the present time, semiconductor process technology node is going under 10nm from 20~30nm base. The 1X nm design rule will be general trend in the next few years. In this situation, the Chemical Mechanical Planarization (CMP) is focusing on the fine defect which is under 20nm. At this conference, I would present the mechanism of defect which caused by dispersant polymer, additive polymer and slurry inhibitor in ultimate fine design technology era. We found the medium weighted polymer chains were still remained after polishing even if in situ cleaning and ex-situ cleaning was performed. And the remained polymer reacted with the Photo Resistance (PR) material while processing double patterning (DPT). Since the defect size was so small, the defect was not detected in the processing. It is supposed that the compounds composed of slurry polymer and PR material block the etching reaction and make a bridge between line and line spacer. To prevent these polymer enhanced defects, well designed slurry should be used and the perfect cleaning solution is especially needed. The failure mechanism is that a lot of minus charged polymers attached on plus charged layer react with PR and DPT layer and finally going hardening on annealing around 200°C. So, the cleaning solution have to have higher polymer solubility to remove the additive polymer chains on minus or plus charged layer.

TiO<sub>2</sub>纳米管光电材料在低温下的阻变特性研究

选用电化学阳极阳化方法在金属Ti片上生长了TiO2纳米管，并用碳纳米管(CNT)薄膜作为上电级，制作成了CNT/TiO2/Ti三明治形状的纳米器件。测试了样品在各低温下的光电响应特性和电阻特性。研究表明，选用碳纳米管作上电极的TiO2纳米管阵列，在532 nm的激光照射下，其光电导和暗电导特性极大地受到温度的影响。在低温下的光电阻和暗电阻会随着温度的增加而减小，同时暗电流增大，光响应度增强。最后，该器件和作了前置电阻处理后的同类型器件作了简要对比分析。 This paper presents the TiO2 nanotube array (NTA) anodized. Use the carbon nanotube (CNT) film as the upper electrode coated on the TiO2 NTA, a CNT/TiO2NTA/Ti sandwich nanodevice has been fabricated. Its photoresponse and resistance characteristics at low temperature have been researched. Result shows that at 532 nm illumination, the photoconductivity of TiO2 NTA and the dark-conductivity have been strongly impacted by the temperature. The dark resistance and the photo resistance will decrease while the temperature rising, and the dark current and photoresponse accordingly increases as well. Finally, compared with other nanodevice used pre-electroforming, this result has been briefly studied.

Design on a Collision Warning and Vehicle-Headlights Intelligent Switching System

The purpose of this paper is to propose a design of an automobile driver-assistance system. It uses the STC12C5A60S2 as its main controller, and the HC-SR04 as its ultrasonic ranging. Then, the sensor DHT11 is responsible for the external temperature and humidity measurement as well as the velocity correction. These help to improve the precision of the ultrasonic measurement. Through the combination of the vehicle distance detecting and the photo resistance monitoring the external illuminance, we can realize the vehicle-headlights intelligent switching. LCD12864 is an information display combining all the information such as temperature, humidity, vehicle distance and so on, and finally conduct the collision warning via the buzzer. The experimental results show that the system designed has advantages of reliable operation, simple structure, low price and double functions as the collision warning and the vehicle-headlights intelligent switching, which ensures it a good application prospect.

Multichromophoric sugar for fluorescence photoswitching.

A multichromophoric glucopyranoside 2 bearing three dicyanomethylenepyran (DCM) fluorophores and one diarylethene (DAE) photochrome has been prepared by Cu(I)-catalyzed alkyne–azide cycloaddition reaction. The fluorescence of 2 was switched off upon UV irradiation, in proportion with the open to closed form (OF to CF) conversion extent of the DAE moiety. A nearly 100% Förster-type resonance energy transfer (FRET) from all three DCM moieties to a single DAE (in its CF) moiety was achieved. Upon visible irradiation, the initial fluorescence intensity was recovered. The observed photoswiching is reversible, with excellent photo resistance.

Controlling photo-oxidation processes of a polyfluorene derivative: The effect of additives and mechanism

The control of the photo degradation of a fluorene–vinylene–phenylene based-polymer, poly(9,9-di-hexylfluorenediylvinylene-alt-1,4-phenylenevinylene) (LaPPS16) was achieved by addition of a radical scavenger (RS) (enhancing photo resistance) or a radical initiator (RI) (reducing photo resistance). Photoluminescence, UV–Vis absorption, 1H NMR spectroscopies and gel permeation chromatography (GPC) revealed that the incorporating small amounts of RS or RI is an efficient way to control the rates of the photo-oxidation reactions, and thus to obtain the conjugated polymer with foreseeable degradation rates for applications in blue-light sensitive detectors for neonatal phototherapy.

Spectral and photophysical properties, photo and heat resistance of dipyrrolylmethene borofluoride complex and its hybrid material with polymethylmethacrylate

A hybrid material based on polymethylmethacrylate with immobilized borofluoride dipyrrolylmethene complex. The inclusion of the chromophore in the polymer environment is shown to result in a reduced polarization due to the weakening of the forces of intermolecular interactions. Study of spectral properties, photo and thermal stability showed that inclusion of the complex in the polymer matrix can significantly increase the photo and thermal stability and mechanical strength of the material while preserving the spectral characteristics inherent to the individual compound.

The Simulation and Fabrication of Ag/SiO2/Ag Thin Films Color Filter

Abstract This research is based on concepts of the Fabry-Perot principle to design a non-absorption inorganic thin film color filter to increase the saturation of color filters. To make red (R), green (G), and blue (B) color filters, the SiO2 should possess three different thicknesses sandwiched by the silver (Ag) reflective layer. Through thin film optical software simulation, the transmittance and color saturation of R, G, and B color filters were analyzed by changing different thin film materials and thickness thereof. In addition, the actual R, G, and B color filter samples were made by pulse direct current magnetron sputtering and radio frequency magnetron sputtering, respectively. The simulated results show that Ag film has a better transmittance and color saturation than aluminum film. The effect of the magnitude of refractive index, n of SiO2 on the transmittance of R, G, and B color filters is not significant, but, it will result in the red color filter sample center peak wavelength shifts at about 20 nm. The better thicknesses of Ag/SiO2/Ag for the color saturation as well as transmittance in R, G, and B color filters are 30 nm/170 nm/30 nm, 30 nm/131 nm/30 nm, 30 nm/100 nm/30 nm, respectively. Compared with the organic photo resistance coating color filter, this inorganic thin film color filter has better color saturation and optical transmittance than the organic photo resistance coating color filter. When the color filter deviates 15 degrees from the straight angle, the center peak wavelength of R, G, and B will shift left 15∼30 nm, and its transmittance will also decrease 1∼5%. This is because that with a larger viewing angle, the longer the path for the light has to traverse through the color filter, which would result with the change in the color wavelength as well as effect to transmittance.

Research on protection of the architectural glazed ceramics in the Palace Museum, Beijing

Abstract The main damage of architectural glazed ceramics in the Palace Museum was investigated and the photo resistance, thermal resistance of protective materials as well as the protected performance such as hydrophobicity, freeze-thaw resistance, bending and compressive strength of the polymer-applied ceramics was tested. The results showed the main damage of glazed ceramics was the shedding of glaze layer and the change of environmental water and temperature especially subzero was the main reason for the glaze shedding. The photo-resistant and thermal-resistant of protective materials fluorine resin and the compound materials composed mainly of the fluorine resin were better than Paraloid B72 and the compound materials composed mainly of Paraloid B72. The wrapping method was selected for the protection of glazed ceramics and the hydrophobicity, freeze-thaw resistance, bending and compressive strength of the polymer-applied ceramics were improved, especially protected by fluorine resin and the compound materials composed mainly of the fluorine resin. The optimum polymer could penetrate into the damaged seriously glazed ceramics and play a hydrophobic role in the protection. The report will be useful for the preservation of damaged seriously architectural glazed ceramics.

Electron beam lithography on cylindrical roller

We developed a nano-structure fabrication technology over a cylindrical roller using electron beam lithography (EBL) and a specimen rotation apparatus. The high-resolution patterning is done on a cylindrical roller specimen and it is achieved by controlling the thickness of photo-resistance (PR) and dosage of the electron beam (EB). We successfully obtained homogeneous arrays of one-third circle grating with a nano-scale width 100 nm and a large area of 6 × 3.5 mm square. Couples of the “ITRI” character marks were also fabricated. The stitching control was accurately derived using the in-house made two-axis rotation system, which provides the smallest stitching of about 1.6 μm. The minimum feature size of 100 nm over the cylindrical roller is demonstrated. Moreover, the Nicole template with “ITRI” character pattern on the cylindrical roller was also successfully made, of which thickness is about 80 nm.

PbS Thin Films Using Cost Effective Chemical Method and Enhancement in its Conductance

In the present work the PbS thin films were coated on a glass substrate using chemical bath deposition (CBD) technique which is a scalable technique that can be employed for large area devices. PbS is a direct narrow gap semiconductor which has also been used as photo resistance, diode lasers, humidity and temperature sensors, decorative coatings and solar control coatings. At room temperature, its energy band gap is approximately 0.37-0.4 eV. The reactive substances used to obtained the PbS layers were (Pb(NO3)2), (NaOH), (SC(NH2)2) and H2O for different concentrations at constant room temperature. The structure was determined by X-ray diffraction studies. The thickness of these films was controlled to around 200 nm on changing the concentrations of lead nitrate and thiourea of the reaction solution. When the concentration of lead nitrate is varied from 0.15 o 0.19 M, the resistance decreased considerably which can even be measurable using multimeter. This shows that the films are not resistive. The film was found to be of p-type by hot probe method.

Spin Effects of Low-dimensional Electron Gases Studied by Far-infrared Photoconductivity Experiments

AbstractWe review our recent work on spin effects in low-dimensional electron gases studied using far-infrared photoconductivity technique. We measure the spin-orbit coupling parameter α via spectroscopy by detecting the combined resonance. Detailed filling-factor dependent study shows the collective nature of this excitation, in accordance to theoretical predictions that both Kohn and Larmor theorem are broken for long-wavelength excitations that changes both the Landau and spin quantum numbers. We find that the long spin-relaxation time of a two-dimensional electron gas results in a novel bolometric spin effect, which gives rise to a substantial photo resistance change by reversing the spin polarization of electrons at the Fermi-level.

Far-infrared photoconductivity of electrons in an array of nanostructured antidots

We present far-infrared (FIR) photo-conductivity measurements for a two-dimensional electron gas in an array of nano-structured antidots. We detect, resistively and spectrally resolved, both the magnetoplasmon and the edge-magnetoplasmon modes. Temperature-dependent measurements demonstrates that both modes contribute to the photo resistance by heating the electron gas via resonant absorption of the FIR radiation. Influences of spin effect and phonon bands on the collective excitations in the antidot lattice are observed.

P‐112: Novel Rewritable Card System Using Liquid Crystalline Polymer

AbstractWe have developed a novel rewritable card system using liquid crystalline polymer. The erasing and writing procedures were carried out by application of a thermal‐electrical field alternately to the rewritable medium. This rewritable card has characteristic feature such as high durability, high heat resistance, high photo resistance and also the materials of the system is superior to the well‐ known the rewritable media.